a comparison of material quantities estimates to onsite

A Comparison of Material Quantities Estimates to Onsite Material Use for Bridge Infrastructure Projects

by

Bolaji Akinola Olanrewaju

A thesis submitted in conformity with the requirements for the degree of Master of Applied Science

Graduate Department of Civil and Mineral Engineering University of Toronto

© Copyright by Bolaji Akinola Olanrewaju (2020)

ii

A Comparison of Material Quantities for Highway Bridge Projects:

Detailed Design Stage vs Construction Stage

Bolaji Akinola Olanrewaju

Master of Applied Science

Department of Civil and Mineral Engineering

University of Toronto

2020

Abstract

Material estimates play a crucial role in predicting project cost, project duration, and embodied

CO2e emissions for construction projects. Several factors that occur during the implementation

stage introduce discrepancies in material quantity estimates, which misinform critical decisions

that affect project delivery. There is, however, a limited understanding of the variability in material

estimates for construction projects, and its impacts on other estimating processes. This thesis

compares construction stage quantities to detailed design estimates for eighteen Canadian-based

bridges to quantify the variability in material quantities and to determine the driving factors.

Results show a 3%-85%, 8%-23%, 5%-19%, and 11%-17% increase in concrete, rebar, structural

steel, and asphalt quantities between estimates and onsite use. The results of this thesis inform our

understanding of design estimates and their interpretation. Adjusting for the discrepancy between

estimates and onsite measurements and targeting the driving factors will reduce environmental

impacts, minimize cost overruns and limit delays.

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Acknowledgements

First, I am incredibly grateful to my supervisors, Professor Shoshanna Saxe and Professor Daman

Panesar for the opportunity to pursue my Master’s degree, and for their guidance, kindness,

patience and encouragement throughout my graduate study. Thank you!

I am also thankful to my research sponsors, EllisDon, Looby, WSP, BASP, NSERC, and the

Ontario Centres of Excellence. My special gratitude to Jonathan Waltr, Jon Vallieres and the

Looby staff for their time and commitment to this research, which has been very much appreciated.

My research team, The InfraGHG Group, thank you all for the continued support. Special thanks

to our project manager Mel Duhamel for efforts in obtaining the data used for this study, and for

handling correspondence with our industry partners.

I am most thankful to my parents, siblings, my uncle, aunt and cousins in the US for their love,

constant encouragement and support. Finally, I thank my friends for all their support and

memories.

Glory to God!

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Table of Contents

Acknowledgements ........................................................................................................................ iii

Table of Contents ........................................................................................................................... iv

List of Tables ................................................................................................................................. vi

List of Figures ............................................................................................................................... vii

Introduction .................................................................................................................................1

1.1 Background ..........................................................................................................................1

1.2 Research Objectives and Contributions ...............................................................................4

1.3 Outline of the Thesis ............................................................................................................5

Literature Review ........................................................................................................................7

2.1 The Need for Material Quantity Estimates in the Construction Industry ............................7

2.2 Factors Driving Uncertainty and Variability in Estimates .................................................10

2.3 Knowledge Gap .................................................................................................................12

Methods .....................................................................................................................................14

3.1 Data Source and Description .............................................................................................14

3.2 Estimating Material Quantities for the Design and Construction Stages ..........................18

3.2.1 Conceptual Design Stage .......................................................................................18

3.2.2 Preliminary Design Stage ......................................................................................19

3.2.3 Detailed Design Stage ............................................................................................19

3.2.4 Construction Stage .................................................................................................21

3.3 Comparison of Material Quantities between the Design and Construction Stages ...........22

3.3.1 Comparison of Detailed Design Estimates to Construction Stage Material Use ...22

3.3.2 Comparison of Material Quantities between the Four Main Stages of a Bridge

Project ....................................................................................................................23

Discussion of Findings ..............................................................................................................24

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4.1 Comparison of Material Quantities Between the Detailed Design Stage and

Construction Stage .............................................................................................................24

4.1.1 Comparison of Concrete Quantities .......................................................................24

4.1.2 Comparison of Reinforcing Steel (Rebar) Quantities ............................................36

4.1.3 Comparison of Structural Steel Quantities ............................................................37

4.1.4 Comparison of Asphalt Quantities .........................................................................38

4.2 Comparison of Material Quantities across the Four Main Design and Construction

Stages .................................................................................................................................39

4.2.1 Evolution of Concrete Quantities...........................................................................39

4.2.2 Evolution of Reinforcing Steel (Rebar) Quantities ................................................42

4.2.3 Evolution of Structural Steel Quantities ................................................................43

4.2.4 Comparison of Results with GHG Results Available in Literature .......................45

Conclusions ...............................................................................................................................46

5.1 Recommendations for the Construction Industry ..............................................................48

Limitations and Future Research ..............................................................................................50

References ......................................................................................................................................51

vi

List of Tables

Table 2-1: The role of material quantity estimates of project stakeholders .................................... 8

Table 2-2: The four main stages of a bridge project ....................................................................... 9

Table 2-3: Causes of variability in estimates for specific case studies ......................................... 11

Table 2-4: Most important factors driving variability in the construction projects ...................... 11

Table 3-1: Composition of the highway bridge case studies regarding bridge span and width,

bridge type, completion status, delivery method, and availability of data ................................... 15

Table 3-2: Design and construction documents obtained from the contractors and their level of

completion..................................................................................................................................... 17

Table 3-3: Mass per unit length value of each girder type ........................................................... 20

Table 4-1: The construction stages of the In-progress bridge case studies................................... 27

Table 4-2: Factors driving additional onsite concrete use ............................................................ 32

Table 4-3: Factors responsible for additional mass concrete use ................................................. 33

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List of Figures

Figure 1-1: Percentage of bridges in need of rehabilitation or replacement ................................... 2

Figure 3-1: Structural components of a typical bridge ................................................................. 23

Figure 4-1: Comparison of concrete quantities between the detailed design stage and the

construction stage of the completed case studies .......................................................................... 25


construction stage for the In-progress bridge case studies............................................................ 26

Figure 4-3: Completed Projects - Comparison of substructure concrete quantities between the

detailed design stage and the construction stage........................................................................... 29

Figure 4-4: Completed Projects - Comparison of superstructure concrete quantities between the


Figure 4-5: In-Progress Projects: Comparison of substructure concrete quantities between the


Figure 4-6: Change in substructure and superstructure concrete quantities between the detailed

design stage and the construction stage ........................................................................................ 30

Figure 4-7: Contribution of factors driving additional onsite concrete use to total substructure

concrete increase ........................................................................................................................... 33

Figure 4-8: Contribution of factors to additional onsite concrete use .......................................... 35

Figure 4-9: Comparison of reinforcing steel quantities between the detailed design stage and

construction stage.......................................................................................................................... 36

Figure 4-10: Comparison of structural steel between the detailed design stage and construction

stage .............................................................................................................................................. 38

Figure 4-11: Comparison of asphalt between the detailed design stage and construction stage .. 39

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Figure 4-12: Evolution of Concrete Quantities for B4 ................................................................. 40

Figure 4-13: Evolution of Concrete Quantities for the Substructure of B8 .................................. 41

Figure 4-14: Evolution of Reinforcing Steel Quantities for B8 .................................................... 43

Figure 4-15: Evolution of Structural Steel Quantities for B8 ...................................................... 44

1

Introduction

This thesis investigates the material quantity differences between onsite material use and estimates

to quantify the uncertainty in material quantity estimates for bridge infrastructure projects in

Canada.

1.1 Background

Bridges are critical components in Canada's transportation network. They are essential for

personal mobility, connect regions and communities, and are vital to Canada's economic

productivity (Transport Canada, 2019). There are over 80,000 highway bridges in Canada, and

on average, 11 million commuters travel over some of Canada's busiest bridges annually

(Government of Canada, 2017). However, over 40% of highway bridges in Canada were built

more than fifty years ago and are nearing the end of their service life (National Research Council

Canada, 2015; Canadian Infrastructure Report Card, 2019). A significant number of these

bridges are structurally deficient, i.e., their structural components are defective due to damage or

deterioration, with about 10,000 highway bridges needing urgent rehabilitation or replacement

(Palu and Mahmoud, 2019).

Figure 1-1 displays the aggregated percentage of Canadian bridges approaching the end of their

service life and requiring immediate attention (Statistics Canada, 2016). Thus, it is expected that

many of these bridges will need to be restored or replaced to meet current and future traffic

demands, as well as to sustain trade networks which accounts for more than 60% of Canada's total

revenue (The Canadian Chamber of Commerce, 2017; Fenn et al., 2019).

In addition to the fact that infrastructure is ageing and warrants repair or replacement, several

economic and environmental indicators suggest there will be a significant boom in bridge

construction activities over the next 30 - 50 years (National Research Council Canada, 2015;

Ministry, 2017; Steer Group, 2019). The most prominent factor is increasing traffic volumes

(Jackson, 2019). The projected increase in Canada's population by about 50% (from 37.1 million

inhabitants to 55.2 million inhabitants) from 2018 to 2068 will intensify the need to improve

regional connectivity and expand current transportation infrastructure network (The Canadian

Chamber of Commerce, 2017; Infrastructure Canada, 2018; Statistics Canada, 2019).

2

Figure 1-1: Percentage of bridges in need of rehabilitation or replacement

% of bridges in need of rehabilitation or replacement

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Other factors indicating significant bridge construction work in the future include further

deterioration of existing bridge infrastructure due to climatic conditions (freezing and thawing,

and chloride exposure), and the influences of future climate change impacts (e.g. floods, frequent

heatwaves, and excessive rainfall) on the safety and performance of existing bridges (Wright et

al., 2012; Public Sector Digest, 2015; Palu, 2019). Also, the lack of routine bridge maintenance

due to inadequate funding and considerable bridge maintenance backlogs further exacerbate

deterioration, resulting in the need to replace the bridges in the future (Ministry of Transportation

Ontario, 2009).

The rehabilitation and replacement of existing bridges, as well as the construction of new bridges

due to the expansion of the current infrastructure network, have the potential for significant

environmental and financial impacts through the use of materials and fuel in construction. The

construction industry, of which the bridge industry is a part of, consumes 50% of global resources

annually (OECD, 2019). It also contributes to the depletion of commonly used construction

materials (Graham, 2017). For example, the shortage of sand and gravel used for the erection of

roads and bridges has been attributed to the increasing rate of construction and urbanization

(Graham, 2017; Beiser, 2019; Brown, 2019). Also, the production processes of the most widely

used bridge construction materials, i.e., concrete, steel, and asphalt, contribute to between 12% -

15% of global anthropogenic CO2 emissions (European Commission, 2016; Lehne and Preston,

2018), and account for 75% - 85% of the total embodied energy of bridges (Du, Safi and Pettersson,

2014; Krantz et al., 2015). Additionally, the bridge construction industry generates a significant

amount of construction waste. In 2016, asphalt and concrete from roads and bridges were

responsible for about 45% of the total construction and demolition debris generated in the U.S.

(U.S. Environmental Protection Agency, 2019).

Furthermore, bridge projects can cause substantial financial strains on federal and provincial

resources, as well as on taxpayer's money (Palu and Mahmoud, 2019). They often experience cost

overruns, with the actual cost being about 34% higher than cost estimates (Flyvbjerg, Holm and

Buhl, 2007; Antoniou, Konstantinidis and Aretoulis, 2016; Dimitriou, Marinelli and Fragkakis,

2018).

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For these reasons, it is encouraged that future bridge projects are designed and constructed in ways

which mitigate their resource consumption, waste generation, financial impacts, and

environmental impacts.

1.2 Research Objectives and Contributions

A first step to mitigating the impacts of bridge construction is to understand material use within

the construction industry. Material quantity estimates are essential in the construction industry

(Antoniou et al., 2018). They are necessary for predicting project cost, labour and equipment

requirements, project duration, and in informing embodied greenhouse gas (GHG) assessments

(Garemo, Matzinger and Robert, 2015; ProEst, 2018; Kiper, 2020). However, several factors that

occur during the construction stage, including design changes due to owners request and differing

site conditions, introduce uncertainty in material quantity estimates (Alaryan, Elshahat and

Dawood, 2014; Desai, Pitroda and Bhavasar, 2015; Albtoosh and Haron, 2017). The uncertainty

in material estimates introduces variability in subsequent estimation processes, which limit efforts

to minimize the aforementioned impacts of the bridge construction industry, and negatively impact

decision making that affect project delivery (Alnuaimi et al., 2010; Choudhry et al., 2017).

Quantifying the variability in material quantity estimates, and understanding the driving factors

can initiate better and comprehensive mitigating solutions to ensure bridge projects are delivered

on-time and under-budget while limiting their environmental impacts. Several authors have

conducted studies to explore the factors causing discrepancies in construction projects across

several countries Asia and Europe (Arain, Assaf and Pheng, 2004; Keane, Sertyesilisik and Ross,

2010; Khoso et al., 2019). There is, however, a limited understanding of the variability in material

quantities estimates for construction projects. Additionally, there is limited research investigating

the factors driving the variability for construction projects across North America.

This thesis compares material quantity estimates at the detailed design stage to onsite material use,

i.e., construction stage material quantities, for eighteen bridge projects. Secondly, this thesis

identifies bridge components and factors responsible for changes in material quantities within the

case studies considered. The bridge construction materials assessed in this thesis are concrete,

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reinforcing steel (rebar), structural steel, and asphalt. These materials were the focus of this thesis

because they are the most widely used bridge construction materials, and also because they

contribute significantly to the cost and environmental impacts of bridge construction (Collings,

2006; Hammervold, Reenaas and Brattebø, 2013; Wang et al., 2015). All eighteen case studies

are located in Canada and are subject to the same bridge code. The case studies comprise nine

prestressed concrete girder bridges, two reinforced concrete bridges, two steel girder bridges, one

post-tensioned concrete bridge, and four structural steel bridges. Eleven of these case studies are

highways crossing over water bodies, while the remaining cross over existing roadways. Seven

of the case studies are recently completed projects as of July 20th 2020, and were constructed in

the last five years. The remaining eleven are ongoing construction projects that are at varying

levels of completion, ranging from superstructure construction to asphalt paving and are all

expected to be completed by early 2021.

Furthermore, using a subset of the case studies where more data was available, this thesis conducts

a preliminary investigation to compare material quantities across the four main bridge design and

construction stages. These stages include the conceptual design stage, the preliminary design stage,

the detailed design stage, and the construction stage. The continuous material quantities

assessment between the four design and construction stages is an attempt at determining the

material quantity impacts of bridges with design and construction development.

The results of this thesis provide information that will inform and facilitate better decision-making

in an uncertain space, to impact the delivery of construction projects positively. The results also

provide information to facilitate the development of other accurate decision support tools

including, cost estimation models, embodied GHG estimation models, and waste generation

models.

1.3 Outline of the Thesis

This thesis is divided into six chapters. Following the introduction in Chapter 1, Chapter 2

identifies existing practices for estimating bridge material quantities in the industry, the factors

driving variability in material quantity estimates and addresses the research gaps. Chapter 3

describes a comprehensive method for analyzing the material quantities between the detailed

design stage and construction stage in this thesis. Also, it describes the process of obtaining

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material quantities for the subset of case studies investigating the evolution of material quantities

across design and construction stages. This chapter also highlights the available data and sources

of supplementary information used in this work. Chapter 4 discusses the findings of the study.

Chapter 5 includes the conclusions and addresses recommendations for the construction industry,

and lastly, Chapter 6 presents research limitations and future work.

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Literature Review

Based on existing literature, this section highlights the need for material quantities estimates, the

factors driving discrepancies in material quantities between the design and construction stages,

and lastly, addresses research gaps.

2.1 The Need for Material Quantity Estimates in the Construction Industry

The estimation of material quantities in the construction industry dates back to the early 19th

century (Canadian Institute of Quantity Surveyors, 2017). During this time, estimations, otherwise

known as quantity takeoffs (QTO)), were done manually by project stakeholders, using

specifications from design drawings to determine the appropriate amount of materials needed by

a project (Popescu, Phaobunjong and Ovararin, 2003; Finch, 2016). The stakeholders responsible

for this process are expected to have a thorough understanding of the construction drawings and

design specifications to produce accurate material quantity estimates (Ramos, 2017). However, in

the mid-2000s, the Architectural-Engineering-Construction (AEC) industry experienced a

significant shift from traditional manual estimations to using several automated takeoff programs

including Autodesk Revit QTO, ProEst, and Navisworks (Azhar, Khalfan and Maqsood, 2012;

ProEst, 2018; Liu, Lu and Peh, 2019). The increasing use of such programs has improved the

efficiency of the estimation process, and reduced estimation errors observed in the manual method

(Golaszewska and Salamak, 2017; Merz, 2019).

Material estimates are vital in the construction industry. They have different levels of importance

to stakeholders involved in a project, i.e., project owner, designers, contractors, and

subcontractors, as summarized in Table 2-1. Estimates vary across the design and construction

stages of bridge projects, which ranges from the conceptual design stage, preliminary design stage,

detailed design stage, to the construction stage, as shown in Table 2-2. They become more accurate

with project development due to the availability of more information (García de Soto, Adey and

Fernando, 2014; Naneva et al., 2020).

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Table 2-1: The role of material quantity estimates of project stakeholders

Source: (Durana, 1999; Watt, 2014; Garemo, Matzinger and Robert, 2015; Marinelli et al.,

2015; Jeong and Gransberg, 2016; Antoniou et al., 2018; Dimitriou, Marinelli and Fragkakis,

2018; ProEst, 2018; QTO Estimating, 2018; Kiper, 2020)

Stakeholder Role of Material Quantity Estimates

Project Owner Provides a holistic view of the project requirements

To effectively allocate a budget within the general financing of the project

Acts as a decision-making tool for determining if the project should be modified, executed

as planned, or abandoned

Provides vital information regarding the construction materials required

Guides the client when choosing the best contractor

Designer Assess the environmental impacts of the bridge design and to ensure bridge designs meet

regulatory requirements relating to greenhouse gas (GHG) emissions

In providing forecasts of construction costs in the pre-planning phases of the design stage

Ensuring that project requirements are met, and design solutions are cost-effective.

Informs the type of contract

Contractor Helps in estimating labour requirements

Informs actual onsite material-use

Develop project milestones

Assists in determining equipment rental costs

Ensures sufficient profit margin

Monitoring and tracking project success

Guides the contractor when agreeing to contractual terms

Guides project bidders when submitting bid proposals

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Table 2-2: The four main stages of a bridge project

Source : (Ma, Chen and He, 2009; Chen and Lian, 2014; Alberta Transportation, 2016; Arjun, 2016; U.S. Department of Transportation, 2016; MEC Bridge Design Engineers,

2017; Multnomah County, 2017; Tang, 2017)

Stage Description

1 Conceptual Design Stage Description of project problem and project objectives Preparation of concept plans

Development of bridge design alternatives

Available information includes bridge width and length, number and types of spans, and material types.

2 Preliminary Design Stage Involves the selection of the best design scheme from the proposed design alternatives

Ascertains the feasibility of the selected bridge concept

Modifications in the stage include: optimization of bridge girders, alteration of girder spacings

3 Detailed Design Stage Involves finalizing all the bridge design details

Design documents are sufficient for the construction of bridge components

Available information includes dimensions and locations of structural members, connections with other members, quantities of rebar.

4 Construction Stage Involves installation of the bridge components using detailed design documents

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However, in construction, very rarely do onsite material quantities align with estimates (Flyvbjerg,

Holm and Buhl, 2007; Cantarelli et al., 2012; Garemo, Matzinger and Robert, 2015). Overrun is a

common occurrence in large infrastructure projects including bridges, and is described as the

difference between the predicted and actual material use (Love et al., 2014; Garemo, Matzinger

and Robert, 2015; Mckinsey & Company, 2015; Institute of Civil Engineers, 2019). Occasionally,

it is caused by the project manager or estimator incorrectly measuring the quantity from the project

drawings and specifications (Netscher, 2015). However, in most cases, it is caused by change

orders initiated at the construction stage either due to client requests, design complexity, change

in project scope or unforeseen site conditions (Chan and Kumaraswamy, 1997; Hameed Memon,

Abdul Rahman and Faris Abul Hasan, 2014; Wang et al., 2015). These factors introduce

uncertainty and variability in material quantity estimates, especially in the design stage, which

causes a ripple effect that propagates to downstream estimating processes, including project cost,

project duration, and embodied GHG assessments (Assaf and Al-Hejji, 2006; Assaf, Hassanain

and Abdallah, 2017; Choudhry et al., 2017).

2.2 Factors Driving Uncertainty and Variability in Estimates

There are a plethora of studies that have been conducted to explore the potential reasons and

causative factors driving uncertainty and variability in estimates in the construction industry (Chan

and Kumaraswamy, 1997; Assbeihat and Sweis, 2015; Jibrin, Muhammad and Labaran, 2020).

Some of these studies highlighted factors specific to a particular case study such as a classroom

building (Alnuaimi et al., 2010), healthcare facility (Keane, Sertyesilisik and Ross, 2010), a road

project, and water transmission project (Alnuaimi et al., 2010), as shown in Table 2-3. Others

explored factors that were particular to project types, i.e. residential projects, transportation

infrastructure, building projects, or general factors for all forms of construction projects, as

outlined in Table 2-4.

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Table 2-3: Causes of variability in estimates for specific case studies

Table 2-4: Most important factors driving variability in the construction projects

Authors

Geographical area Case study

Lack of Coordination between

stakeholders

Errors and omissions in design

documents Differing Site

conditions Change in

project scope Changes due to owners request

(Alnuaimi et al., 2010) Oman Road project x x

(Keane et al., 2010) England Healthcare facility x x x

(Alnuaimi et al., 2010) Oman Water transmission project x x x

(Alnuaimi et al., 2010) Oman Classroom buildings x x

(Alnuaimi et al., 2010) Oman Breakwaters for a seaport x

Authors Geographical

area Structure types

Lack of Coordination

between stakeholders

Insufficient drawing details

Errors and omissions in design

documents Design

complexity

Differing site

conditions

Inadequate contractor experience

Change in project Scope

Weather conditions

Changes due to

owner's request

Lack of contractor

involvement in the design

(Chan and Kumaraswamy, 1997) Hong Kong General x x x x x x x

(Fisk, 1997) U.S.A. Buildings x x x x x x

(Arain et al., 2004) Saudi Arabia Buildings x x x x x x x x

(Wu et al., 2005) Taiwan Transport x x x x x x x x

(Alnuaimi et al., 2010) Oman General x x x

(Keane et al., 2010) England General x x x

(Pourrostam et al., 2011) Malaysia General x x

(Alaryan et al., 2014) Kuwait General x x x x x

(Hameed Memon et al., 2014) Malaysia General x x x x x

(Assbeihat and Sweis, 2015) Jordan General x x ` x

(Desai et al., 2015) India General x x x x x

(Perkins, 2016) U.S.A. General x x x x

(Staiti et al., 2016) Palestine General x x x x x x x x

(Albtoosh and Haron, 2017) Jordan General x x x x x

(Choudhry et al., 2017) Pakistan General x x x x x

(Ali Kamal Balbaa et al., 2019) Egypt General x x x x x x x x x

(Khoso et al., 2019) Pakistan General x x x x x x

(Mohammad and Hamzah, 2019) Malaysia Residential x x x x x

(Tran and Do, 2019) Vietman General x x x x x

(Jibrin et al., 2020 Nigeria General x x x

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Table 2-3 and Table 2-4 show that the most common factors driving variability in the construction

industry and uncertainty in estimates are changes due to owners request, insufficient drawing

details, errors and omissions in design documents, differing site conditions, and change in project

scope.

These two tables suggest the sources of uncertainty and variability in quantity estimates have been

well explored in literature and well understood. However, despite the knowledge that has been

accumulated, little work has been done to investigate and quantify the discrepancies between

onsite material use and estimates due to these driving factors. Additionally, as observed in Table

2-3 and Table 2-4, minimal research studies have investigated the factors driving discrepancies

between design and construction stages for construction projects in North America.

To the authors' knowledge, only two studies in the literature compare detailed design material

quantity estimates to onsite use, i.e., the construction stage, to understand the differences in

material quantities between the two stages. Tang, Cass and Mukherjee, 2013 compared as-planned

estimates and as-built data for a highway reconstruction project in Michigan, U.S.A, and the

authors found a 6% discrepancy in non-reinforced concrete quantities. Similarly, the research

study by Nahangi et al., under review, compared preconstruction estimates obtained from a

Navisworks (a building information modelling software) model, to onsite material-use for a bridge

renewal project in Ontario, Canada. The authors observed a 63%, 31%, and a 171% increase in

concrete, structural steel, and asphalt quantities, respectively. Although very informative, the

limitation of these two studies is that their analyses are based on a single case study, and as a result,

cannot be generalized for other infrastructure types.

2.3 Knowledge Gap

This thesis contributes to the existing literature in two main areas: (1) the discrepancies between

design and construction concerning materials, and (2) factors driving variability in construction

projects. This paper compares the material quantity estimates generated during the tendering stage,

i.e., detailed design stage, to actual onsite material use for bridge construction projects. This thesis

improves on existing studies that have compared onsite material use to estimates by conducting

assessments on eighteen bridge case studies that are all based in Canada. Also, this thesis augments

13

our knowledge on the variability and causes of discrepancies in material quantities for construction

projects across North America which is currently limited.

This thesis increases our understanding of the influence of material variability and uncertainty on

subsequent estimation processes that occur during the preconstruction stages of bridge projects.

Additionally, it provides information that can inform the type of adjustments that need to be

incorporated into future estimates to mitigate impacts of inaccurate forecasts before they become

consequences. The results of this thesis will also inform the uncertainty of the decisions made

regarding the projects relating to the material quantities, to allow stakeholders make better

decisions under uncertainty.

Furthermore, using a subset of the case studies where more data was available, this thesis conducts

a preliminary investigation to compare material quantities across the conceptual design stage, the

preliminary design stage, the detailed design stage, and the construction stage. This thesis will

improve our understanding of how design and construction development impacts the material

quantities of bridge construction projects.

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Methods

This chapter describes an empirical approach to estimate the material quantities of eighteen

Canada-based highway bridges at the detailed design stage and construction stage. Concrete,

reinforcing steel (rebar), structural steel, and asphalt are the four construction materials studied in

this thesis. This is because they are the most widely used bridge construction materials, and they

contribute significantly to the cost and environmental impacts of bridge construction (Collings,

2006; Marinelli et al., 2015; Wang et al., 2015; Antoniou et al., 2018; Penadés-Plà et al., 2018).

3.1 Data Source and Description

Eighteen highway bridge case studies are examined in this thesis. All bridges are located within

Canada and are subjected to the same bridge code. The bridge spans and widths of the case studies

range from 29 – 194 m, and 11 – 19 m, respectively. The bridge case studies are composed of nine

prestressed concrete girder bridges, two reinforced concrete bridges, two steel girder bridges, one

post-tensioned concrete bridge, and four structural steel bridges. Eleven of these case studies are

highways crossing over water bodies, while the remaining cross over existing roadways. Also, the

case studies include thirteen highway projects that were executed using a design-bid-build project

delivery method, and five highway projects implemented using the design-build project delivery

method. None of the case studies is named to protect anonymity; instead, they are referred to with

bridge ID such as B1, B2…B15b, as detailed in Table 3-1.

All eighteen bridges are new constructions and are clustered into three categories: The first

category comprises seven bridge projects that were completed between 2015 and 2019. The second

category includes two ongoing bridge case studies (B6a and B13a), where all the concrete

construction work has been finalized and are at the asphalt paving stage as of July 1st 2020. The

third category comprises nine case studies (B3a, B3b, B6b, B8, B10, B11, B13b, B14a, B14b),

where some of the structural components are still under construction. The substructures of these

nine case studies have been constructed as of July 1st 2020. However, their superstructures are at

varying levels of completion, ranging from deck construction to the construction of the barrier

walls. For this study, the nine bridge projects in the first two categories are grouped as the

completed bridge projects, while the nine case studies in the third category are labelled as in-

progress bridge projects.

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Table 3-1: Composition of the highway bridge case studies regarding bridge span and width, bridge type, completion status, delivery

method, and availability of data

Available Data

Bridge ID

Bridge Span (m)

Bridge Width (m)

Bridge Type Highway Type Status Delivery Method

C P D Con

B1 29.0 13.0 Prestressed Girder Bridge River Crossing Completed DBB x x

B2 33.0 12.4 Prestressed Girder Bridge River Crossing Completed DBB x x

B3a 28.0 14.0 Reinforced Concrete Bridge Roadway Crossing Incomplete DBB x x

B3b 37.5 14.0 Reinforced Concrete Bridge Roadway Crossing Incomplete DBB x x

B4 43.4 12.4 Prestressed Girder Bridge River Crossing Completed DB x x x x

B5 44.0 13.0 Steel Girder Bridge River Crossing Completed DB x x

B6a 46.5 18.5 Prestressed Girder Bridge Roadway Crossing Incomplete DBB x x

B6b 46.5 18.5 Prestressed Girder Bridge Roadway Crossing Incomplete DBB x x

B7 46.5 12.3 Prestressed Girder Bridge River Crossing Completed DB x x

B8 52.1 10.7 Prestressed Girder Bridge River Crossing Incomplete DB x x x x

B9 88.0 11.0 Prestressed Girder Bridge Roadway Crossing Completed DBB x x

B10 98.8 12.1 Prestressed Girder Bridge Roadway Crossing Incomplete DBB x x

B11 112.0 12.1 Post-Tensioned Concrete Bridge Roadway Crossing Incomplete DBB x x

B12 118.0 12.3 Steel Girder Bridge River Crossing Completed DB x x

B13a 150.0 14.0 Steel Bridge River Crossing Incomplete DBB x x

B13b 150.0 14.0 Steel Bridge River Crossing Incomplete DBB x x

B14a 194.0 14.3 Steel Bridge River Crossing Incomplete DBB x x

B14b 209.0 14.3 Steel Bridge River Crossing Incomplete DBB x x

C – Conceptual Design Stage, P – Preliminary Stage, D – Detailed Design Stage, and Con – Construction Stage

16

Lastly, the case studies include four sets of twin bridges (B3a and B3b, B6a and B6b, B14a and

B14b, and B15a and B15b), that represent the northbound and southbound bridge lanes of four

separate case studies.

Design and construction documents for all eighteen case studies were obtained from the general

contractor. For thirteen of the case studies (B1, B2, B3a, B3b, B6a, B6b, B9, B10, B11, B13a,

B13b, B14a, B14b), an external consultant (bridge designer) hired by the project owner designed

the bridges, while the contractor merely executed the project using the prepared design documents.

For the remainder of the case studies, the contractor was responsible for both the design and

construction stages. Table 3-2 gives a comprehensive summary of all the design and construction

documents used in this study. The database of documentation includes:

Preliminary Design Reports: These reports document the early stages of design and

constructability. It makes a full acknowledgement of existing conditions and constraints,

establishes alternatives and comparatives studies between bridge alternatives for selection. It also

serves as the basis for plans and specifications for the final design and construction contracts.

Structural Drawings: These were provided by the general contractor, and comprise a set of plans

and details on how the bridge is going to be built.

Estimator's Bills of Quantities (BOQ): These are documents stating estimated quantities of work

to be performed. The estimators prepared them during the bidding and tendering stages of the DBB

projects, and the detailed design stage of the DB projects.

Concrete and Asphalt Delivery Packages: These documents are concrete and asphalt delivery

invoices provided by material suppliers upon delivery.

Bills of Lading and Steel Mill Certificates: Bills of lading documents are a detailed list comprising

the types and quantities of materials delivered. Steel mill certificates are documents that provide

the chemical and physical composition of the structural steel sections. These documents, which

both contain steel quantities, were supplied by the material suppliers and were handed over to the

general contractor upon delivery.

17

Table 3-2: Design and construction documents obtained from the contractors and their level of completion

● - Available and complete, ◓ - Available but Incomplete, ○ – Not Available, N/A – Not Applicable

N/A indicates that the material or document did not apply to the case study under consideration

Detailed Design Stage Data Construction Stage Data

BOQ

Bridge ID

Prelim. Design Report

Struc. Drwgs Asphalt Concrete Rebar

Struc. steel

Project Schedule (Asphalt

Quantities)

Precast girder

erection files

Struc. steel erection

files

Concrete placement packages +

Concrete Delivery invoices

Asphalt delivery invoices

Bills of Lading (rebar)

Mill certificates (structural

steel)

1 B1 ○ ● ● ● ● ● ○ ● N/A ● ● ◓ ○

2 B2 ○ ● ○ ○ ○ ● ○ ● N/A ● ○ ○ ○

3 B3a ○ ● ○ ● ● N/A ● N/A N/A ● ○ ◓ ○

4 B3b ○ ● ○ ● ● N/A ● N/A N/A ● ○ ◓ N/A

5 B4 ● ● ● ○ ○ N/A ○ ● N/A ● ◓ ○ N/A

6 B5 ○ ● ○ ○ ○ ○ ○ N/A ● ● ● ◓ ●

7 B6a ○ ● ○ ● ● N/A ● ● N/A ● ○ ◓ N/A

8 B6b ○ ● ○ ● ● N/A ● ● N/A ● ○ ◓ N/A

9 B7 ○ ● ● ● ● N/A ○ ● N/A ● ● ● N/A

10 B8 ● ● ● ● ● ○ ○ ● ○ ● ○ ○ ●

11 B9 ○ ● ○ ● ● ● ○ ● ● ● ● ● ●

12 B10 ○ ● ○ ● ● N/A ● ● N/A ● ○ ◓ N/A

13 B11 ○ ● ○ ● ● N/A ● N/A N/A ● ○ ◓ N/A

14 B12 ○ ● ● ● ● ● ○ N/A ● ● ● ● ●

15 B13a ○ ● ○ ● ● ○ ● N/A ● ● ○ ◓ ●

16 B13b ○ ● ○ ● ● ○ ● N/A ● ● ○ ◓ ●

17 B14a ○ ● ○ ● ● ○ ● N/A ● ● ○ ◓ ●

18 B14b ○ ● ○ ● ● ○ ● N/A ● ● ○ ◓ ●

18

Project Schedules: These are documents that describe the project activities, milestones, and

deliverables. They were generated during the bidding stages of the DBB projects, and the detailed

design stage of the DB projects by the scheduler.

Concrete Placement Packages: These documents are prepared by the site superintendent and

indicate the quantities of poured concrete.

Erection Procedure Plans: These are documents produced by the designers and contractors

during the preconstruction stage detailing the assembly of structural components on a

construction site.

Canadian Precast and Prestressed Concrete (CPCI) Manual: A document covering the design,

manufacture and installation of precast and prestressed concrete(Canadian Precast/Prestressed

Concrete Institute, 2017). It contains general design information of precast and prestressed

girders that are made in Canada.

Canadian Institute of Steel Construction (CISC) Steel Manual: A handbook for structural steel

design in Canada containing physical properties of currently available structural steel sections.

3.2 Estimating Material Quantities for the Design and Construction Stages

For this thesis, the design and construction stages of bridges are divided into four stages. These

stages include the conceptual stage, the preliminary stage, the detailed design stage, and the

construction stage. This section gives a detailed description of how material quantities were

calculated for each stage.

3.2.1 Conceptual Design Stage

The conceptual design stage is where the project is defined, and multiple bridge design alternatives

are explored (Morcous et al., 2001). Data for this stage was obtained from preliminary structural

design reports which were prepared by the bridge designers and provided by the contractor.

19

As illustrated in , this report was available for two bridge case studies, B4 and B8 (both DB

projects). The preliminary structural design reports provided ten bridge design alternatives B4,

and five for B8, with each alternative accompanied by concrete, reinforcing steel (rebar), and

structural steel quantity estimates. The analysis resulted in a range of concrete and steel quantities,

with the highest and lowest representing the design alternative with the most and least concrete

and steel quantities, respectively.

3.2.2 Preliminary Design Stage

The preliminary stage involves the selection of the best bridge design among the proposed

alternatives (Tang, 2017). The quantities of this design stage comprise concrete and steel quantity

estimates (i.e. rebar and structural steel) of the selected bridge design for B4 and B8. Reinforcing

steel, structural steel and concrete quantity estimates were available for B8. However, the chosen

design for B4 was a single-span concrete box girder which required zero structural steel quantities.

Thus, the steel quantities for B4 comprised of just the estimated rebar quantities.

3.2.3 Detailed Design Stage

In this design stage, a detailed analysis of the selected design is conducted to finalize all the

essential details of the bridge structure needed for tendering and construction (Wang et al., 2015).

For this thesis, the material quantities in this design stage were primarily obtained from the

estimator's bills of quantities (BOQ), as shown in Table 3-2. For bridge projects with missing BOQ

estimates, other data sources like the structural drawings and project schedules were used in

supplementing missing information, which is further explained below.

3.2.3.1 Asphalt

The primary data source for the asphalt quantities was the estimator's BOQs. The estimators BOQs

were produced just before construction using the detailed design documents. Asphalt quantities

for thirteen case studies were unavailable, as shown in Table 3-2 The unavailable asphalt data for

ten of the thirteen bridge case studies (B3a, B3b, B6a, B6b, B10, B11, B13a, B13b, B14a, and

B14b) were obtained from the project schedules also created during the bidding process. Each

project schedule had the estimated weight of asphalt quantities needed to pave the bridge deck.

For project schedules without asphalt quantities, they were estimated by multiplying the bridge

20

deck area by the proposed asphalt thickness using dimensions obtained from the structural

drawings. The calculated volume was then multiplied by the density of asphalt to obtain the asphalt

mass in megagrams (Mg). This method was validated by comparing asphalt quantities calculated

from the structural drawings, with asphalt quantity estimates obtained from the project schedules,

for case studies where both data were available. The quantities were within 5% of each other.

3.2.3.2 Concrete

Concrete volume quantities of structural components were in most cases provided in the estimator's

BOQ, as displayed in Table 3-2. For case studies where BOQ records were not available, the

concrete volume of each bridge component was estimated using dimensions in the structural

drawings. Similarly, in determining the weight of the prestressed girders, the total girder length

obtained from the estimators BOQs or structural drawings was multiplied by the section's mass

per unit length ratio of each girder type, as shown in Table 3-3. For girder types with unavailable

mass per unit length ratios, the weight of the prestressed girder was estimated using the dimensions

available in the structural drawings.

Table 3-3: Mass per unit length value of each girder type

Bridge ID Type of Girder Girder code Mass per unit length

(kg/m)*

B1 Box Girder B900 Not Available



B6a I-girder CPCI 1900 1,380

B6b I-girder CPCI 1900 1,380



B9 I-girder NU 1600 1,322

B10 I-girder CPCI 1900 1,380

* Mass length ratio from (Canadian Precast/Prestressed Concrete Institute, 2017)

21

3.2.3.3 Steel

3.2.3.3.1 Reinforcing Steel (Rebar)

Rebar quantities were for the most part obtained from the BOQs, as shown in Table 3-2. Bridge

case studies with no rebar data in the BOQs, i.e. B2, B4, and B5, were excluded from the rebar

comparison analysis.

3.2.3.3.2 Structural Steel

Structural steel quantities comprise of the structural steel piles for the bridge foundations in B9;

structural steel girders in B5 and B12; and structural steel frames that make up the four steel

bridges (B13a, B13b, B14a, and B14b). Steel pile quantities were estimated by multiplying the

total pile length obtained from the BOQs, by the corresponding mass per unit length ratio of each

pile type available in the Canadian Institute of Steel Construction Manual. Structural steel girder

quantities and steel frame quantities were extracted from erection procedure plans provided by the

contractor, as displayed in Table 3-2.

Structural steel data was aggregated by the contractor for two sets of twin bridges that represent

northbound and southbound lanes of the same project (B14a and B14b, and B15a and B15b).

Consequently, in each case, the twin bridges were treated as one case study just for the structural

steel comparison analysis

3.2.4 Construction Stage

Onsite material quantities were obtained from a combination of documents delivered to the

construction site by construction material suppliers, and documents used by the contractor in

tracking material delivery, as illustrated in Table 3-2. These documents include asphalt and

concrete delivery invoices, concrete placement packages, steel mill certificates, and bills of lading.

For all the bridge case studies, it is assumed that all the materials delivered to the construction site

were used for construction.

Asphalt quantities were extracted and collated from asphalt delivery tickets. Ready-mix concrete

quantities were aggregated from concrete delivery tickets and concrete placement packages.

Prestressed girder concrete quantities were obtained from shop drawings provided by the suppliers;

22

rebar and structural steel quantities were obtained from bills of lading and mill certificates

provided by the steel suppliers. Only B7, B9, and B12 had a complete set of rebar bills of lading

documents, as shown in Table 3-2. Others either had incomplete or missing rebar data. For this

reason, the rebar analysis for the construction stage was only conducted for B7, B9, and B12 where

sufficient data was available to facilitate comparison between detailed design and construction

stages.

Also, construction sequence documents, minutes from site meetings, change order documents,

project coordinator's notes, and site engineer's records were obtained to verify that stipulated

material quantities correspond with the amounts listed out in the bills of lading, concrete delivery

packages, and asphalt delivery packages.

3.3 Comparison of Material Quantities between the Design and Construction Stages

3.3.1 Comparison of Detailed Design Estimates to Construction Stage Material Use

Following the analyses, a comparison of concrete, rebar, structural steel, and asphalt quantities

was conducted between the detailed design stage and construction stage for the completed and in-

progress case studies. This comparison aims to assess the changes in material quantities between

these two stages.

Also, for the nine completed projects (seven fully completed bridge projects and two ongoing

projects with finalized concrete work), a comparison of concrete quantities between onsite material

use and detailed design estimates was conducted for the two major structural components, i.e., the

substructures and superstructures. For the nine in-progress projects, a comparison of concrete

quantities between the detailed design and construction stage was conducted just for the

substructures.

The substructure is the portion of the bridge below ground that supports the superstructure. It

consists of the pier, pier footings, wingwalls, abutments, mass concrete, and tremie concrete, as

shown in Figure 3-1. The tremie concrete is concrete that is placed below water level to tie

23

different structural elements together. The American Concrete Institute defines mass concrete as

'any volume of concrete with dimensions large enough to require that measures be taken to cope

with the generation of heat from the hydration of cement and attendant volume change to minimize

cracking'. In contrast, the superstructure is the portion of the bridge above the substructure. It

comprises the deck slab, bridge girders, and barrier walls.

* Substructure includes mass concrete and tremie concrete which are not shown in figure

Figure 3-1: Structural components of a typical bridge

3.3.2 Comparison of Material Quantities between the Four Main Stages of

a Bridge Project

A comparison of concrete, rebar and structural steel quantities between the four design and

construction stages (conceptual design stage, preliminary design stage, detailed design stage, and

construction stage) were conducted for the two case studies with sufficient data for all four stages.

24

Discussion of Findings

The results of the material quantity analyses are presented in this chapter based on material type

and level of completion. Firstly, the comparison of concrete quantities for the completed and in-

progress bridges between the detailed design stage and construction stage are presented. Secondly,

the comparison of concrete quantities between the detailed design stage and construction stage of

the superstructure and substructure are presented. Subsequently, the comparison of rebar,

structural steel and asphalt quantities of the completed bridges between the detailed design stage

and construction stage are introduced. Lastly, the evolution of concrete, rebar, and structural steel

quantities across the conceptual, preliminary, detailed design and construction stages for the two

bridge case studies with sufficient data (B4 and B8) are introduced.

4.1 Comparison of Material Quantities Between the Detailed Design Stage and Construction Stage

4.1.1 Comparison of Concrete Quantities

4.1.1.1 Completed Bridge Projects

The completed bridge projects comprise seven fully completed bridges and two ongoing bridge

projects where concrete construction work has been finalized and are currently being asphalt paved

(B6a and B13a) as of July 1st 2020. These include six prestressed concrete girder bridges (B1, B2,

B4, B6a, B7, and B9), two steel girder bridges (B5 and B12), and one steel bridge, B13a.

Figure 4-1 shows the comparison of concrete quantities between the detailed design stage and

construction stage for the completed bridge case studies bridges. Overall, more concrete quantities

were used in the construction stage than predicted in the detailed design stage. The additional

concrete use range from 3% to 85%, with a mean of 21%. B7 experienced the most noticeable

25

change in concrete quantities between the two stages, which was due to the construction of a new

concrete wall not included in the detailed design estimates.


construction stage of the completed case studies

0

500

1000

1500

2000

2500

3000

3500

B1 B2 B4 B5 B6a B7 B9 B12 B13a

Co

ncr

ete

Qu

anti

ties

(M

g)

Detailed Design

Construction

26

4.1.1.2 In-Progress Bridge Projects

The in-progress bridge projects comprise two reinforced concrete bridges (B3a and B3b), three

prestressed girder bridges (B6b, B8, and B10), one post-tensioned concrete bridge (B11), and three

steel bridges (B13b, B14a and B14b). These bridges are at varying levels of completion, as

illustrated in Table 4-1. The aggregated concrete quantities of the completed structural

components, which were obtained from onsite delivery documents were compared with concrete

estimates of the respective components.

Figure 4-2 illustrates that compared to the detailed design concrete estimates, there was generally

more concrete use in the construction stage. The increase in concrete quantities ranges from 7% to

71%, with a mean of 27%. Further investigation into the design and construction documents

indicated that the substructure was the major contributor to the additional concrete use.


construction stage for the In-progress bridge case studies

0

500

1000

1500

2000

2500

3000

3500

4000

4500

B3a B3b B6b B8 B10 B11 B13b B14a B14b

Co

ncr

ete

Qu

anti

ties

(M

g)

Detailed Design

Construction

27

Table 4-1: The construction stages of the In-progress bridge case studies

Bridge ID Construction Stage Structural components yet to

be constructed

Projection of Total Concrete Use

(Mg)

Estimated Concrete Quantities for

Completed Segments (Mg)

Concrete Used to Date

(Mg)

B3a Removal of bridge deck formwork barrier walls 1227 1181 1697

B3b Bridge deck curing approach slabs, barrier walls 1783 1627 1745

B6b Construction of bridge deck approach slabs, barrier walls 1688 1486 1744

B8 Erection of parapet wall formwork Parapet walls 1574 1415 1568

B10 Erection of prestressed girders deck, barrier walls, approach slabs 2320 1161 1582

B11 Erection of Approach Slab Formwork approach slabs 3782 3677 4235

B13b Erection of Structural frames deck, barrier walls, approach slabs 2843 1237 1546

B14a Erection of Bridge Deck Formwork deck, barrier walls, approach slabs 2878 859 1469

B14b Erection of Structural frames deck, barrier walls, approach slabs 4222 1505 1736

28

B14a had the most substantial concrete quantity increase of 71% from 859 Mg to 1469 Mg, as

shown in Figure 4-2 and Table 4-1. This considerable increase is attributed to additional concrete

deliveries being made for the construction of the mass concrete structure, which was not initially

accounted for in the estimator's BOQ.

Furthermore, the analyses show that at their current stages of construction, B3a, B6b, and B11

have consumed 38%, 29% and 8%, respectively, more concrete than the total concrete estimates

for the entire project. As illustrated in Table 4-1, B3a and B11 are missing one structural

component each to reach completed status, while the approach slabs and barrier walls are still

expected to be built for B6b.

4.1.1.3 Comparison of Concrete Quantities Between the Detailed Design Stage and Construction Stage of the Substructure and Superstructure

A comparison of concrete quantities between the detailed design stage and construction stage of

the substructure and superstructure was conducted to investigate the components responsible for

additional concrete use. The substructure consists of the pier, pier footings, wingwalls, abutments,

mass concrete, and tremie concrete, as shown in Figure 3-1. The superstructure comprises the deck

slab, bridge girders, and barrier walls.

Figure 4-3 and Figure 4-4 display the comparison of concrete estimates to actual onsite use for the

substructure and superstructure, respectively, for the nine completed bridge case studies. The

substructure is seen to have consumed significantly more concrete quantities compared to the

superstructure. B1 is the only exception, and the reason for this was due to 30% less concrete being

used for the substructure tremie pour. The mean of the additional onsite concrete use for the

substructure and superstructure across the nine completed bridges are 56% and 5%, respectively,

as illustrated in Figure 4-6.

29

Figure 4-3: Completed Projects - Comparison of substructure concrete quantities between

the detailed design stage and the construction stage

Figure 4-4: Completed Projects - Comparison of superstructure concrete quantities

between the detailed design stage and the construction stage

0

500

1000

1500

2000

2500

B1 B2 B4 B5 B6a B7 B9 B12 B13a

Co

ncr

ete

Qu

anti

ties

(M

g)Detailed Design

Construction

0

200

400

600

800

1000

1200

1400

1600

1800

B1 B2 B4 B5 B6a B7 B9 B12 B13a

Co

ncr

ete

Qu

anti

ties

(M

g)

Detailed Design

Construction

30

Figure 4-5: In-Progress Projects: Comparison of substructure concrete quantities between

the detailed design stage and the construction stage

Figure 4-6: Change in substructure and superstructure concrete quantities between the

detailed design stage and the construction stage

0

200

400

600

800

1000

1200

1400

1600

1800

2000

B3a B3b B6b B8 B10 B11 B13b B14a B14b

Co

ncr

ete

Qu

anti

ties

(M

g)

Detailed Design

Construction

31

The substructure concrete quantities between the detailed design stage and construction stage of

the nine in-progress bridge projects were also compared to investigate additional concrete use.

Although these bridges are incomplete, all the structural components of the substructure have been

constructed, thus allowing for comparison with the concrete estimates from the detailed design

stage.

Figure 4-5 displays the changes in the substructure concrete quantities for the in-progress bridge

projects. On average, the substructure of the in-progress bridges consumed approximately 44%

more concrete quantities in the construction stage, as shown in Figure 4-6.

4.1.1.4 Factors Driving Additional Concrete Use

Across the case studies, five main factors were responsible for the additional concrete quantities

used in the construction of the substructure. They include:

1) Mass concrete for substructure construction: Mass concrete refers to large quantities of concrete

used for filling voids, for example, excavated trenches. It also comprises significant volumes of

concrete with dimensions large enough to require that measures be taken to cope with the

generation of heat from the hydration of the cement and attendant volume change to minimize

cracking (American Concrete Institute, 2016). Structural components with a member thickness of

about 900mm or more are often identified as mass concrete (Alper and Jijina, 2018).

Additional mass concrete was ordered in the construction stage for 10 of the case studies, B3a,

B6a, B6b, B7, B10, B12, B13a, B13b, B14a, and B14b as reported in Table 4-2. According to the

project coordinator's notes and change order documents, the additional mass concrete orders were

used to rectify rock overbreaks during excavation for B3a, B6b, B10, B13a, and B13b, as observed

in Table 4-3. Other reasons driving additional mass concrete quantities in the construction stage

include, more concrete quantities being used to raise the elevation of mass concrete in B14b to the

height of the abutment footing, and omission of mass concrete quantities in the estimators' BOQ

for B14a as shown in Table 4-3. No information on the reasons behind further mass concrete use

was available for B6a, B7, and B12, as observed in Table 4-3.

32

Table 4-2: Factors driving additional onsite concrete use

Bridge ID Mass

concrete

Unexpected

Retaining

Wall

Mudsills/

Levelling

Pads

Unshrinkable

Fill

Concrete in

Footings

Concrete in

Wingwalls and

Abutment

B2 x

B3a x x x x x

B3b x x

B4 x x

B5 x

B6a x x x x

B6b x x

B7 x x

B8 x

B9 x x

B10 x x x

B11 x x x

B12 x x

B13a x x x x

B13b x x x

B14a x x x

B14b x x

33

Table 4-3: Factors responsible for additional mass concrete use

Bridge ID Factors Driving the Increase in Mass Concrete

1 B3a Overbreak

2 B6a Not available

3 B6b Overbreak

4 B7 Not available

5 B10 Overbreak, Reinforce ground in areas where loose rock was found

6 B12 Not available

7 B13a Overbreak, Reinforce ground in areas where loose rock was found

8 B13b Overbreak

9 B14a Omitted in tendering BOQ

10 B14b To increase the elevation of mass concrete to abutment footing level

Figure 4-7: Contribution of factors driving additional onsite concrete use to total

substructure concrete increase

34

The mass concrete had a 6% - 96% contribution to the total concrete increase of the substructure

for the case studies affected, as illustrated in Figure 4-7.

2) Use of mudsills and levelling pads- Temporary structures known as mudsills and levelling pads

were built in B3a, B3b, B6a, B9, B11, and B13a, as shown in Table 4-2, to distribute loads from

the falsework to the supporting ground evenly. The mudsills and levelling pads contributed

between 2% - 88% of the total substructure concrete increase, as illustrated in Figure 4-7

3) Retaining wall – Unexpected retaining walls were introduced in the construction stage for B3a

and B7, as displayed in Table 4-2: Factors driving additional onsite concrete use. This had a 69%

and 86% contribution to the total increase in substructure concrete quantities between the detailed

design and construction stages for B3a and B7, respectively. Also, the contractors carried out

repair work on the retaining walls of B7, as observed in the concrete placement packages, which

accounted for an additional 10% concrete increase.

4) Unshrinkable fill – Bridge B9 ordered more concrete quantities in the construction stage in the

form of unshrinkable fill during the installation of the corrugated steel pipe (CSP) for the integral

abutments. Integral abutments are abutments that allow the substructure and superstructure to

move together to accommodate the required translation and rotation, i.e. no need for bridge

expansion joints and bearings (White, 2007). According to the instruction notices to contractors

prepared by the client, the unshrinkable fill was used as backfill and to provide lateral support for

CSP. The decision to use the unshrinkable fill was backfill was made in the construction stage,

and represented approximately 58% of the additional concrete use in the substructure of B9.

5) Concrete use in the footings, wingwalls, and abutment – Additional concrete use was observed

in the construction of footings, wingwalls, and abutment, as illustrated in Table 4-2. Ten bridge

case studies consumed more concrete in the construction of the footings, while the construction

stage of fifteen bridge case studies consumed more concrete quantities in the construction of the

wingwalls and abutments, as observed in Table 4-2: Factors driving additional onsite concrete

useTable 4-2. The additional concrete use in the footings, and for the combined wingwalls and

abutment had a 6% - 77% and 4% - 100% contribution to the additional concrete use in the

substructure of these bridges as illustrated in Figure 4-7. No information on the reasons behind

further concrete use in these structural members was available.

35

Figure 4-8: Contribution of factors to additional onsite concrete use

-200

0

200

400

600

800

1000

1200

1400

B1 B2 B3a B3b B4 B5 B6a B6b B7 B8 B9 B10 B11 B12 B13a B13b B14a B14b

Co

ntr

ibu

tio

n t

o A

dd

itio

nal

Co

ncr

ete

Use

(M

g)

Unshrinkable fill

Wingwalls and Abutments

Footings

Retaining Walls

Mudsills and Levelling Pads

Mass Concrete

36

Figure 4-8: Contribution of factors to additional onsite concrete use summarizes the contribution

of the factors mentioned above to the additional concrete quantities observed in the substructure.

The negative concrete quantities observed for B3b, B7 and B12 indicate lower concrete quantities

compared to estimates were used onsite. However, the savings in concrete quantities for these three

case studies were marginal compared to the overall quantities of additional concrete used onsite.

Also, Figure 4-8 shows that mass concrete, additional concrete use in footings, wingwalls, and

abutments were the most common for all eighteen bridge case studies, and are the major factors

responsible for the variability in concrete quantities for the highway bridges considered.

4.1.2 Comparison of Reinforcing Steel (Rebar) Quantities

Detailed design stage rebar estimates of the three bridge case studies considered were obtained

from the estimator's BOQ. For the construction stage, rebar quantities were obtained from QA/QC

documents, i.e., bills of lading documents. B7 and B12 were constructed under the same contract;

as a result, the provided QA/QC documents were the combined bills of lading for these two

bridges. For this reason, these two bridges were treated as one case study. Figure 4-9 shows the

comparison between the BOQ estimates and the onsite quantities of reinforcing steel for B9 and

the combined B7 and B12 case studies.

Figure 4-9: Comparison of reinforcing steel quantities between the detailed design stage

and construction stage

0

50

100

150

200

250

B9 B7 + B12

Rei

nfo

rcin

g St

eel Q

uan

titi

es (

Mg)

Detailed Design

Construction

37

B9 experienced a 23% increase in rebar quantities from 79 to 97 Mg. Also, an 8% increase in the

combined rebar quantities for B7 and B12 was observed between the detailed design stage and

construction stage, thus resulting in a total mean increase of 16% for the three case studies.

4.1.3 Comparison of Structural Steel Quantities

Figure 4-10 displays the structural steel comparison between the detailed design stage and

construction stage for seven bridge case studies (B5, B9, B12, B13a, B13b, B14a, and B14b).

Estimates for the detailed design stage were obtained either from the estimator's BOQ (B5 and B9)

or from the structural steel erection procedure documents (B5, B12, B13a, B13b, B14a, B14b).

For the construction stage, quantities were obtained from bills of lading documents and mill

certificates. Structural steel data was aggregated by the contractor for two sets of twin bridges that

represent northbound and southbound lanes of the same project (B13a and B13b, and B14a and

B14b). Consequently, in each case, they were treated as one case study. Figure 4-10 displays the

sum of the structural steel quantities of the twin bridges for the detailed design stage and

construction stage.

As observed in Figure 4-10, the construction stage structural steel quantities are higher than the

detailed design estimates for all the case studies. The increase in structural steel use range from

5% – 19%, with a mean of 11%. However, due to insufficient data, it was not possible to

determine the driving factors responsible for the additional structural steel quantities in the

construction stages of these case studies.

38

* B7 has zero structural steel but is included in the figure to maintain consistency with rebar quantities figure and

asphalt quantities figure

Figure 4-10: Comparison of structural steel between the detailed design stage and

construction stage

4.1.4 Comparison of Asphalt Quantities

Figure 4-11 displays the increase in asphalt quantities from the detailed design stage to the

construction stage for four bridge case studies (B1, B5, and B7 and B12). As observed for the other

construction materials, the asphalt quantities consumed in the construction stage are higher than

the estimated amounts in the detailed design stage. The changes in asphalt quantities range from

11% to 17%, with a mean of approximately 15%. The discrepancy in asphalt quantities indicates

a larger area of roadway paving than what was provided in the structural drawings, and the

estimators BOQ. For example, in B5, an existing road leading to the bridge was paved in the

construction stage which resulted in additional asphalt use. The decision to pave the existing road

was made during the construction stage, resulting in more asphalt quantity use in the construction

stage.

0

500

1000

1500

2000

2500

3000

B5 B9 B7 + B12 B13a + B13b B14a + B14b

Stru

ctu

ral S

tee

l Qu

anti

ties

(M

g)

Detailed Design

Construction

39

Figure 4-11: Comparison of asphalt between the detailed design stage and construction stage

4.2 Comparison of Material Quantities across the Four Main Design and Construction Stages

4.2.1 Evolution of Concrete Quantities

Figure 4-12 and Figure 4-13 illustrate the comparison of concrete quantities across the four design

and construction development stages, i.e., the conceptual design stage, the preliminary design

stage, the detailed design stage and the construction stage, for two bridge case studies (B4 and B8).

These two case studies were the only bridge case studies with sufficient concrete quantity data for

the four design and construction stages considered.

The conceptual stage for B4 comprises concrete quantities of ten design alternatives. The mean of

the concrete quantities for the ten design alternatives (1426 Mg) is plotted, as shown in Figure

4-12.

11740

13012

0

200

400

600

800

1000

1200

1400

1600

1800

B1 B5 B7 + B12

Asp

ahlt

Qu

anti

ties

(M

g)

12000

13000

14000

11000

40

The error bar represents the design alternatives that consume the most and least concrete quantities,

i.e. the most concrete-intensive and least concrete-intensive alternative designs considered. The

preliminary stage is composed of the aggregated concrete quantities of the selected bridge design

(936 Mg); 34% less than the mean value of the preceding stage. The selected design was the eighth-

most concrete-intensive and consumed 52% less concrete compared to the conceptual estimate for

the most concrete-intensive design alternative. As shown in Figure 4-12, the concrete quantities at

the detailed design stage experienced a 6% decrease from the preliminary design stage. The

decrease in material quantities is attributed to the reduction in width and span of the bridge by 150

mm and 2600 mm, respectively.

Figure 4-12: Evolution of Concrete Quantities for B4

Dash line represents the concrete quantities at the conceptual design stage, which is the mean of the concrete

quantities of 10 design alternatives

The error bar represents the most concrete-intensive and least concrete-intensive design alternatives

0

500

1000

1500

2000

Conceptual Design Preliminary Design Detailed Design Construction

Co

ncr

ete

Qu

anti

ties

(M

g)

Design and Construction Stages

41

Conversely, there was an 18% increase in concrete quantities from the detailed design stage to the

construction stage. The 18% increase was due to additional onsite concrete use for the bridge

abutments, wingwalls, and parapet wall.

B8 experienced a different concrete quantity evolution to B4, as shown in Figure 4-13. The

substructure of B8 was completed at the time this thesis was written (July 2020), but the

superstructure remains under construction. Thus, a comparison of concrete quantities between the

four design and construction stages was conducted for just the substructure, as illustrated in Figure

4-13.

Dash line represents the concrete quantities at the conceptual design stage, which is the mean of the concrete


The error bar represents the most concrete-intensive and least concrete-intensive design alternatives

Figure 4-13: Evolution of Concrete Quantities for the Substructure of B8

0

200

400

600

800


Sub

stru

ctu

re C

on

cret

e Q

uan

titi

es (

Mg)

Stages of Design and Construction Development

42

The conceptual stage comprises the concrete quantity estimates of five substructure design

alternatives, the mean of which is 346 Mg. At the preliminary stage, the design consultant selected

the most concrete-intensive design alternative, with a total concrete weight of 1275 Mg. According

to the preliminary design report, this design was chosen because of lower future maintenance costs

and constructability benefits. The substructure concrete estimate at the preliminary design stage

was 480 Mg, a 39% increase from the conceptual stage mean. At the detailed design stage, there

was a 16% increase in the substructure concrete quantities from the preliminary stage. This

increase was due to more concrete quantities assigned to the abutment and wingwalls after the

completion of the detailed design analysis. The final onsite concrete use (i.e. for construction stage)

for the substructure was 709 Mg; 28% higher than the detailed design stage. This increase was

due to additional concrete use in the construction of the piers, pier caps, abutment and wingwalls.

4.2.2 Evolution of Reinforcing Steel (Rebar) Quantities

Figure 4-14 illustrates the comparison of rebar quantities across the conceptual design stage, the

preliminary design stage, and the detailed design stage of B8. The construction stage rebar data

was incomplete due to ongoing construction as at the time this thesis was written (July 2020).

The conceptual stage comprises rebar quantities of five design alternatives. The rebar quantity

estimates for each design alternative was 25 Mg, resulting in a mean of 25 Mg. The preliminary

stage rebar estimates were of the selected bridge design, which was 25 Mg. After the detailed

design analysis was carried out, the resulting rebar quantity estimates at the detailed design stage

increased by 104% to 51 Mg. As of July 1st 2020, 47 Mg of rebar quantities had been ordered to

the construction site of B8, and it is expected that more rebar quantities will be needed to construct

missing structural components (the parapet walls).

43

Dash line represents the rebar quantities at the conceptual design stage, which is the mean of the rebar quantities of

5 design alternatives

Figure 4-14: Evolution of Reinforcing Steel Quantities for B8

4.2.3 Evolution of Structural Steel Quantities

B8 was the only case study with complete structural steel data for all four design and construction

stages. The structural steel data are composed of structural steel piles that make up the bridge

foundations. The conceptual stage of B8 comprises structural steel quantities of five design

alternatives, with an average of 91Mg, as illustrated in Figure 4-15. The error bar represents the

design alternatives that consume the most and least structural steel quantities. The preliminary

stage is composed of the structural steel estimates of the selected bridge design (77 Mg). At the

detailed design stage, there was a 137% increase in structural steel quantities from the preliminary

stage.

0

10

20

30

40

50

60


Rei

nfo

rcin

g St

eel Q

uan

titi

es (

Mg)

44

Dash line represents the rebar quantities at the conceptual design stage, which is the mean of the structural steel


The error bar represents the most structural steel intensive and least structural steel intensive design alternatives

Figure 4-15: Evolution of Structural Steel Quantities for B8

Additional steel piles required to support the modular bridge introduced in the detailed design

stage was the reason for the increase in structural steel quantities. The modular bridge serves as a

temporary detour and aims to reduce traffic disruptions for road users during the construction of

B9. Also, there was a 98% increase in structural steel quantities from the detailed design stage to

the construction stage. However, there was no readily available information to ascertain the reason

for this increase.

0

50

100

150

200

250

300

350

400


Stru

ctu

ral S

tee

l Qu

anti

tes

(Mg)

Design and Construction Stages

45

4.2.4 Comparison of Results with GHG Results Available in Literature

The results of the material quantities trend for bridges across the four design and construction

stages considered were compared to results available in literature for buildings. Cavalliere et al.,

2018 conducted a study to assess the embodied greenhouse gas (GHG) emissions impact of

buildings with design and construction development. The results of their research showed a

declining trend in embodied GHG emissions for buildings, across the design and construction

stages. Their study also suggests that for buildings, the construction stage contributes a lesser

embodied GHG impact than the detailed design stage, which is contrary to the results obtained in

this thesis.

Multiplying the concrete quantities in Figure 4-12 and Figure 4-13 by an Ontario-specific

embodied GHG intensity factor obtained from (Nahangi et al., under review) will reveal that the

embodied GHG emissions of the construction stage for bridges are higher than that of the detailed

design stage. The difference in the relationship between detailed design stage impacts and

construction stage impacts for buildings and bridges initiates the question on whether the material

estimation procedures for buildings produce more accurate estimates than that of bridges.

Alternatively, it could also indicate that for buildings, there are fewer design changes that impact

material quantities in the construction stage than there are for bridges.

However, it is important to note that the results of the study conducted by Cavalliere et al., 2018

were based on fifteen low-rise Swiss residential buildings; thus, the embodied GHG trend for high-

rise and commercial buildings might be very different. Also, the construction stage data were not

actual onsite data but rather material quantities obtained from BIM models. Thus, based on existing

literature, there is a high possibility that those values do not reflect actual onsite use (Nahangi et

al., under review). Unfortunately, there are not enough research studies that compare detailed

design estimates to that of onsite material use. Neither are there enough studies that compare the

evolution of material quantities to fully understand how material quantities, and their associated

impacts vary across design and construction stages for multiple building and infrastructure types.

46

Conclusions

This thesis explored two main objectives: (1) it quantified the variability in material quantity

estimates for eighteen bridge infrastructure projects in Canada and, (2) it identified the factors

driving the differences in quantities.

The first part of the thesis investigated the differences in concrete, reinforcing steel (rebar),

structural steel, and asphalt quantities between the detailed design stage and construction stage

using data obtained from Canadian-based bridge projects. The findings revealed that compared to

estimates, substantially more construction materials are used in the construction stages of bridge

projects. For the completed bridge projects, which comprises seven fully completed bridges and

two ongoing projects where concrete work has been finalized, between 3% - 85% more concrete

quantities were used onsite compared to estimates. Similarly, for in-progress projects, where

concrete construction work is ongoing, between 7% to 71% more concrete quantities were

consumed onsite when compared with estimates.

The substructure was identified as the major contributor to additional concrete use in the

construction stage of the eighteen case studies, which is indicative of its influence on the variability

in material quantity estimates. When compared to their respective detailed design concrete

estimates, the substructure of the completed and in-progress bridge projects consumed, on average,

56% and 44% more concrete quantities, respectively. Upon further investigation, five main factors

were revealed to be responsible for the additional concrete use in the substructure:

a. Rock overbreak during excavation and the improvement the underlying ground conditions

b. The construction of temporary structures known as mudsills and levelling pads in the

construction stage

c. The introduction of unexpected structural components (retaining walls)

d. Extra concrete quantities to serve as backfill and provide lateral support for the CSP during

the installation of the integral abutment

e. Increased concrete use in the construction of footings, wingwalls and abutment.

Also, the observed change in rebar, structural steel, and asphalt quantities range between 8% -

23%, 5% - 19%, and 11% - 17%, respectively.

47

The substantial increase in concrete, rebar, structural steel, and asphalt quantities observed in this

thesis provides empirical evidence which reinforces the general view that there are often

discrepancies between design and construction architectural and structural details, and material

quantities. It is also worth noting that the onsite concrete quantities analyzed in this thesis are not

inclusive of rejected concrete batches that did not meet the design specification. Including these

quantities in the analysis would mean a higher average increase in concrete quantities from the

detailed design stage to the construction stage for the competed and incomplete projects,

respectively.

This thesis is beneficial to project owners, consultant, and contractors as it quantifies the variability

in material quantity estimates and emphasizes some of the reasons responsible for additional

material quantities in the construction stage of bridge projects. It identifies the areas upon which

impact mitigation efforts need to be intensified. Also, it empowers the stakeholders involved with

the necessary information needed to put in place necessary preventive measures to reduce cost

overruns, project delays, and environmental impacts, as well as to increase productivity on the

construction site. For example, although cost contingencies are commonly used in practice to

minimize the impacts of cost overruns due to excess material use onsite, it appears that these

contingencies are inadequate in protecting against increases in project cost and project schedule.

The results of this thesis will inform the uncertainty of the decisions made regarding the project

costs, and allow for the provision of appropriate cost buffers that should be incorporated into the

project cost. The same applies to improve the reliability of the environmental impact assessments

during the pre-construction stage, thus allowing for better decisions to be made under uncertainty.

Additionally, the findings of this study demonstrate that adequate geotechnical risk management

and extensive geotechnical investigations are fundamental to mitigating the impacts of the

variability in material quantity estimates for bridge infrastructure projects.

The second part of this thesis compared material quantities across four main design and

construction stages, i.e., the conceptual design stage, preliminary design stage, detailed design

stage, and construction stage, for a subset of the bridge projects. This comparison was conducted

to determine the material quantity impacts of bridges with design and construction development.

The results of the analysis revealed that the evolution of concrete quantities is influenced by

decisions made across the four design and construction stages. The concrete quantities at the

48

preliminary stage and detailed design stage will either decrease or increase from their respective

preceding stage depending on the decisions and modifications made to the bridge design. However,

based on current industry practices, the concrete quantities at the construction stage of bridge

projects will always be higher in comparison to the detailed design stage.

The results of the rebar analysis suggest an increase in rebar quantities between the preliminary

stage and the detailed design stage. However, due to limited data, it was not possible to determine

the variation in rebar quantities between the detailed design stage and construction stage. Also, the

results indicated that the change in structural steel quantities between the conceptual stage and the

preliminary stage is dependent on design decisions made between these two stages. However, an

increasing trend in structural steel quantities was observed between the preliminary stage, the

detailed design stage, and the construction stage.

Understanding the material quantities evolution allows for stakeholders to initiate new practices

in the conceptual design stage that minimize the occurrence of future design changes responsible

for increases in material quantities. The report published in the Engineering and Physical Sciences

Research Council by Sun et al., 2004 states that more than a third of clients are displeased with

the contractor's ability to keep to quoted price estimates and project timeline. Understanding the

trend in material quantities across will allow for designers and contractors to delineate the project’s

needs and requirements, with an increased level of reliability, to improve the client's satisfaction.

Additionally, the trend in material quantities across the design and construction stages observed

for past bridge projects can be leveraged for early stage decision making of new projects to mitigate

the resource consumption, waste generation, financial impacts, and environmental impacts of the

bridge construction industry.

5.1 Recommendations for the Construction Industry

The authors propose the following recommendations for the construction industry to minimize

variability in material quantity estimates, which should contribute to mitigating the adverse

impacts associated with bridge construction.

A more extensive ground investigation should be conducted before construction to have a better

understanding of the site conditions. Being cognizant of the underlying ground conditions will

49

reduce the occurrence of change orders due to unforeseen ground conditions, which ultimately

influences the variability of material estimates. Also, contractors should adopt methods that either

eliminate overbreak or keep it to a minimum. If the preferred method of excavation is the drilling

and blasting method, then the specific charge and the maximum charge per delay should be

carefully selected to reduce blast-induced damage to surrounding work, either in the form of

overbreak or damaged zone or both. The specific charge is a measure of the explosive mass

required to break a unit volume or a unit mass of the rock, while the maximum charge per delay is

the maximum quantity of explosive charge detonated on one interval within a blast (Adhikari,

2000; Singh and Verma, 2010). Verma et al., 2016 highlighted that depending on the rock mass

quality, a specific charge greater than 2.5 kg/m3 and a maximum charge per delay exceeding the

25-30 range may yield at least a 20% overbreak.

Alternatively, if overbreak cannot be avoided, then adequate allowance for overbreak during

excavation should be incorporated in the concrete and steel preconstruction estimates. Also, it is

good practice for stakeholders to carefully check and scrutinize quantities in design drawings and

estimators BOQs in the design and tendering stages to detect omissions. Recognizing omissions

before the start of construction can limit cost overruns, project delays, and also improve the

reliability of the environmental impacts assessments. Also, it can help prevent the contractors from

being held liable for additional costs due to the omissions.

Furthermore, the project stakeholders responsible for estimating material quantities should also

include quantities of materials that are not included in the drawings but are needed to facilitate the

construction process, e.g. temporary structures. Finally, more collaboration between academia and

industry is encouraged, and more proprietary data from several firms in the construction industry,

including design and engineering firms, and contractors should be made available for researchers

to facilitate more research in this domain.

50

Limitations and Future Research

The findings of this thesis are based on case studies that come from one contractor. Thus, the

inherent biases of the construction methods adopted by the contractor limit the generalization of

the thesis outcomes for the construction industry in Canada. Despite this limitation, this thesis still

offers insight into the importance of understanding the variability in material quantity estimates.

However, further research is needed to validate the results of the material quantity changes

between the detailed design stage and construction stage, especially for rebar, structural steel, and

asphalt, where limited data was available. Also, more studies should be conducted to fully

understand the evolution of material quantities across the design and construction stages of

bridges.

Further research is required to compare the changes in material quantities between the detailed

design stage and construction stage of the design-bid-build project delivery system, with the less

fragmented design-bid project delivery method. The delivery method has a considerable influence

on the organization, documentation, and flow of the projects. Hence it would be interesting to

investigate how the intricacies of the two different project management methods impact the

material quantity changes between the detailed design stage and construction stage, and across the

four design and construction stages.

Furthermore, further research on the influence of construction methods, code of practice,

geographical location (cold and tropical locations), and weather factors on the evolution of

material quantities across the design and construction stages can be conducted to investigate if the

results will be consistent with the material quantities trend provided in this thesis.

51

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