alistair g.f. gibb - trent global fabrication part thre… · · 2011-11-242nd floor 19 bedrooms,...

A l i s t a i r G.F. Gibb

pre fabr ica t ion pre-assembly modular isat ion

Part Three APPLICATIONS

This part answers the question: ‘what types of projects can benefit from off-site fabrication?’ Off-site fabrication is used for all types of projects and all sectors of construction project clients and end-users from single-person residential to national power generation. This part provides some examples for various client sectors and where appropriate gives an indication of the countries or project types that most commonly use the application. The lists are illustrative rather than exhaustive.

3.1 Residential applications This category considers domestic buildings up to three storeys, large-scale domestic (high-rise), hospitals, hotels and institutional living accommodation e.g. student, armed forces, prisons. Several residential case studies are presented in Part One (Case Studies 1.2-1.5).

3.1.1 Non-volumetric application examples

Timber (or metal) framed houses Most developed countries Roof trusses Most developed countries Dry-wall systems for internal partitions Most developed countries Concrete panel systems For medium & high- rise, especially non-UK Precast concrete frames and cladding For medium & high-rise, especially non-UK Steel frames For medium & high-rise, most developed

Building services modules Especially for hospitals, rarely for domestic countries

3.1.2 Volumetric application examples

Concrete modular units

Plant room or toilet modules for hospitals or hotels

Operating theatre modules Toilet modules for institutional

Medium and high-rise systems e.g. UK prisons (Case Study 4.3.4, p.167)

Mainly Europe & USA Mainly Europe & USA

Mainly Europe & USA living accommodation

- 54 -

~ APPLICATIONS

I 3.1.3 Modular building examples

Modular house systems for individual

Road-side motels

Medium-sized ‘out-of-town’

dwellings Mainly Japan Especially UK e.g. Forte-Crest (Case Study

3. I ) , Granada, Friendly Hotels

hospital units Mainly Europe

Case Study 3.1 Yorkon

Off-site fabricated modular hotel extension,

This case study illustrates the use of modular building techniques for a major new extension to a four-storey hotel. Yorkon Ltd supplied and installed 57 modules for the Forte Posthouse Hotel in Edinburgh. Figure 3.1 provides a plan layout of the hotel showing the original section, which was built conventionally, and the new extension using modular units. The figure shows the repetition of bedrooms that is ideally suited to modular construction and is one of the main reasons for the technique’s success in medium-rise hotel developments

The four-storey units were installed on a concrete platform giving access under- neath and linking the new extension with the existing five-storey block (Figure 3.2). The concrete platform and barrel roof were supplied by the building contractor.

Project details The new hotel accommodation was as follows: Ground level Car parking and accesslegress route maintained beneath the concrete

2nd floor 19 bedrooms, five which cater for guests with disabilities platform

3RD FLOOR I Figure 3.1 extension. Courtesy of Yorkon Ltd.

Plun luyout of Edinburgh Forte Posthouse showing originul and new

- 55 -

I OFF-SITE FABRICATION ~

Figure 3.2 of Yorkon Ltd.

Photograph of the completed four storey hotel extension. Courtesy

3rd floor 26 bedrooms 4th floor 26 bedrooms 5th floor 24 bedrooms plus two meeting rooms.

The module’s external dimensions were: Double room modules Single room modules Staircase modules (incorporating housemaid’s closet) 12.00 m X 3.00 m

15.80 m X 3.79 m 7.30 m x 3.79 m

The structural frame to the units was of structural steel hot-rolled columns with anti- corrosive paint finish. This gives monocoque frame construction with five-storey cap- abilities The unit floors were insulated cold-formed galvanised steel ‘plate floor’ assembly with structural board floor deck and steel underdrawing. The walls were fully insulated load-bearing cold-formed galvanised steel frames. The roof comprised insulated warm roof panels with integral steel joists forming a composite one-piece construction with external weatherproof membrane. The units had factory-fitted double- glazed windows with cavity drip trays and damp-proof membranes manufactured in PVCu. (Timber and powder coated aluminium are also available.)

Ceilings, floors and walls to the Edinburgh building, had a one-hour fire rating as it is over two storeys high. Buildings below two storeys have a half an hour rating. Sound insulation between bedroom walls and floors is 55 dB. Thermal performance of the walls (including a single external brick leaf) is 0.28 W/m2K, floors 0.25 W/m2K and ceiling and roofs 0.19 Wlm2K.

- 56 -

Figure 3.3 Isometric representation of hotel bedroom units. Courtesy of Yorkon Ltd.

The project team considers that the benefits of modular building for the hotel industry include:

Minimum disruption on site means existing facilities can operate as normal: Number of personnel and amount of plant and deliveries are reduced, lead-

ing to safer and quieter working site. Reduced costs:

construction details

built factory conditions Enhanced quality:

Due to the standardisation of the product, bulk purchasing and repetitive

No costly delays due to inclement weather, rather benefiting from purpose-

Quality controlled factory conditions Trained operatives Inspection prior to delivery.

Speed: Reduced programmes due to the tandem build process The site is prepared

LANTAC (Local Authority National Type Approval Certificate) approval as the manufacturing and fitting out of modules takes place.

of the system eases the planning and statutory approval process.

- 57 -

OFF-SITE FABRICATION

Rooms are practically complete on delivery

Income generated quicker due to short programme times. Fast turnaround of capital outlay:

Acknowledgements This case study was compiledfrorn information provided by Stephanie Clint of Yorkon Ltd.

3.2 Light industrial applications


Steel framed structures with panellised cladding Prefabricated roof systems (e.g. Case Study 3.2) Internal wall systems Storage and material handling systems

Case Study 3.2 Modified Roof Erection System (MRES), Kentucky USA

Conventional steel roof erection on large plan buildings is done in situ, at height. MRES involves the assembly of large roof sections at ground level, within the building footprint and then hoisting them into place. The MRES team aimed to address several important areas, namely safety, productivity, labour shortage, schedule, quality; and cost. The team developed the following rules:

The process must be safe. The process must allow for reverting to conventional erection if problems jeopard-

A reasonable increase in cost is acceptable for this prototype process. All increases and decreases in cost need to be considered. The steel subcontractor must endorse the use of the process

ise the schedule.

Figure 3.4 shows the three main stages of MRES. The initial trial of MRES was on a 13 378 m*industrial building in the USA. The

building had a clear height of 7.3 m and 24 bays of 15.2 x 18.3 m. Half of the plant was built traditionally, using in situ methods, and the other half used MRES, enabling comparison of the two approaches Roof modules incorporated two bays and measured 18.3 x 30.5 m. The modules were pre-assembled at low level where electrical, mechanical and fire protection works were also completed. The modules were then lifted into place using compressed-air driven hoists with a pulley system fixed to the previously erected structural columns

A comparative study of the two approaches is summarised as follows:

- 5 8 -

APPLICATIONS

1. Roof Module’s Structure Components

2. Roof Module Complete and Ready to L i f t

3. Roof Modules Being Raised t o Permanent Position

Figure 3.4 Stevens & Murray, 1994, Figures 1-3.

The Modgied Roof Erection System (MRES). Adapted from

Safety Safety was enhanced by reducing on-site hours, combined with a significant reduction in the work done at height.

Productivity Productivity was improved because personnel continued working in weather conditions that would have prevented work at height. Mechanical works were installed at

- 5 9 -


180 160 140 CONVENTIONAL ERECTION 120

VI h

2 100 80 60

40 20 0

r

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35

Calendar Days

Figure 3.5 Labour Utilisation: M R E S vs conventional. Adapted from Stevens & Murray, 1994, Figure 12.

ground level leading to further productivity gains Labour required for MRES was 85% of the conventional section. The comparison is shown in Figure 3.5.

The assembly process in MRES was the same as conventional but at ground level. However, the lifting process was new to the erection teams, which influenced productivity. The first module to be lifted took 35 minutes, whereas the average lifting time was around 11 or 12 minutes.

Schedule The project was completed two months early, due in part to the benefits of continued work in inclement weather mentioned above. Comparison between the two approaches is shown in Figure 3.6.

U ME

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 Calendar d a y s

Figure 3.6 Schedule comparison: M R E S vs conventional. Adapted from Stevens & Murray, 1994, Figure 13.

- 6 0 -

APPLICATIONS

During the period when both approaches were under way, MRES only stopped for two days, compared to the conventional system’s down-time of six days. The MRES team claims that further labour reductions will be realised on future projects due to increased module sizes and additional experience.

cost For this prototype case the initial cost of MRES was slightly higher than the conventional method, primarily due to extra materials required as stiffeners to the roof modules and additional lifting equipment. The MRES team claims that further savings will be seen in repeat projects

Similar applications On-site pre-assembly of roof units adjacent to the building has been used on a number of other projects such as the Daewoo developments in Korea (Case Study 1.5, p. 28) and Hong Kong’s Chek Lap Kok airport terminal (Case Study 4.4.1, p. 175). Project credits

James A Grey Construction Co. Ltd. Alan L Murray (Stevens & Murray, 1994) Source

MRES Contractor


Modular plant units in some cases, although rare for conventional light industrial developments

3.2.3 Modular building examples

Small to medium industrial units available off-the-shelf or ‘to order’ based on standard systems in many developed countries These are not as common as for commercial buildings due to the prevalence of cost-effective frame and cladding systems for industrial use.

3.3 Commercial applications

Examples of off-site fabrication for a commercial development are given in Example 1.1 (p. 5) and Case Study 3.3 (p. 62).


As for other project types, and in particular: Building services modules for risers and floor distribution (most developed countries). Internal partition systems Raised floor and suspended ceiling systems

-61-



Toilet pods, plant rooms, lift shafts and building services riser shafts installed within new or existing buildings (many developed countries) (e.g. Example 3.1).


Small to medium office units available off-the-shelf or ‘to order’ based on standard systems, used in many developed countries, e.g. Case Study 4.3.3, p. 163.

Example 3.1

The Hongkong & Shanghai Bank in Hong Kong, with architectural design by Foster Associates, exemplified optimisation of off-site fabrication in the 1980s Amongst the many applications on the project, 139 building service modules and risers (designed by Ove Amp & Partners) were prefabricated by Mitsubish at their AKO factory (Davies, 1986). The units were a combination of plant rooms and ofice restrooms (toilets) and weighed up to 50 tonnes They were transported from Japan to Hong Kong by sea. The units were located external to the main building onto a purpose-made steel structure that formed part of the overall architectural design.

Hongkong & Shanghai Bank

Case Study 3.3 Embankment Place office development, central London

Innovative management and technology were combined to create 42 000 m2 ofice space in the air above a mainline railway station in the heart of London. The building was completed towards the end of the 1980s’ commercial building boom in the UK, and exploited the air rights above Charing Cross railway station. The main building provided 13 storeys of large floor office space suspended from a large box-girder bowstring arch spanning 30 metres, which was supported on two rows of structural steel columns founding on 45 metre deep hand-dug caissons This building could not have been completed successfully except for appropriate utilisation of off-site fabrication techniques

Applications of off-site fabrication

Structural steel frame Prefabrication here was limited due to lifting restrictions and there being no room adjacent to the site to pre-assemble on-site. Column and beam elements were fabricated in as large pieces as possible in accordance with normal UK practice for steel structures The roof-level bowstring arch was assembled on-site from off-site fabricated box-girder sections These had been pre-assembled off-site to check for quality of fit. Main wall cladding The main wall cladding to all elevations comprised panellised metal and glass curtain wall units These units incorporated granite stone facings, fully glazed windows, all

- 6 2 -

APPLICATIONS

Figure 3.7

weather barriers and radiant heating panels In situ construction of the main walls would not have been possible due to the very short on-site period available. Further- more, work over a live railway station would have prevented the use of conventional scaffold which is associated with in situ ‘stick system’ cladding. Panellised cladding was also chosen because it produced a higher quality end-product, benefiting from the enhanced factory environment and the opportunity to prototype and pre-inspect off- site. A full-size sample incorporating several panels and all the major cladding features was tested for buildability and performance at the manufacturer’s works in Ger- many (Figure 3.8).

Embankment Place from the River Thames.

Figure 3.8 Gartner, Germany.

Clcrdding prototype during performance testing. Courtesy of Joseph

- 63 -

OFF-SITE FAEWCATION

Figure 3.9 Cladding panels being transported to site.

Materials were sourced throughout the world (e.g. granite from Italy, aluminium elements from Germany), and then assembled at the German cladding contractor’s plant in the UK. Units were inspected for quality at the works, and also after installation on-site. Units were transported to site on A-frames using specially designed low- loader vehicles (Figure 3.9), and installed with tower cranes provided by the construction manager.

A key feature of the cladding was the pre-installation of fixing brackets to form a sophisticated system, enabling accurate positioning of internal dovetail support slots Brackets for the whole elevation were installed and checked prior to panel installation. External dovetail fixings on the back of the panel slotted into the support bracket dovetails, enabling units to be installed in less than 20 minutes. (Figure 3.10) Delivery and installation had to be stringently planned and coordinated to safeguard the gen- eral public around the site. Service core cladding External wall cladding to the service cores was fabricated off-site as stone-faced precast concrete panels Stone was sourced from Italy, as for the main wall panels, and cast onto the face of the precast units, connected by stainless steel dowel pins (Figure 3.1 1). Units were generally storey height and designed to utilise the on-site craneage to ca-

- 6 4 -

APPLICATIONS

Figure 3.10 Cladding panel being installed (note pre-fixed support brackets).

pacity (i.e. units may be different sizes depending on their location relative to the cranes). The fixing system was less sophisticated than the main wall cladding, comprising concrete corbels and dowel pins Toilet units and air-handling plant units Both the ofice washroom units and air-handling plant units located at the service cores on each floor were pre-assembled off-site. Due to their size these units were delivered at predetermined times and located into the side of the building (as described in section 5.6), before being rolled into place. Toilet units are described in more detail in Part 4 (Case Study 4.2.1, p. 128). Figure 3.12 shows the typical floor layout and locations of toilet and air-handling units

Acknowledgements This case study was compiled from the author’s own experience on the project and from information provided by Paul West and John Hushes of k i n g Management Ltd.

- 65 -

OFF-SITE FA~RICATION

Figure 3.11 Stone-faced precast concrete cladding panels during manufacture.

Figure 3.12 handling units.

Typicalfloor layout at Embankment Place showing toilet and air-

- 6 6 -

.I --

APPLICATIONS

Project credits Greycoat plc Terry Farrell & Company Ove Arup & Partners Laing Management Limited Redpath Dorman Long Joseph Gartner Dean Jesmond IAC Jordan’s Modular

Client Architect Structural engineer Construction manager Structural steel contractor Main wall cladding contractor Precast cladding contractor Air-handling unit manufacturer Toilet pod manufacturer

3.4 Retail Applications 3.4.1 Non-volumetric application examples

As for other project types.


Modular plant rooms, services risers, toilet units, lifts and escalators for new-build or refurbishment of larger stores.


Smaller, out-of-town retail units

Petrol station forecourt units

e.g. UK Drive-Thru McDonalds, Case Study 4.3.2,

e.g. Agip Petroli, ESSO, BP, Case study4.3.1, p. 155, p. 160.

and Example 3.2.

Example 3.2

The modular building concept has now been taken up by four large petrol retailers - Jet, Shell, Elf and Esso. Cook (1996) reports on how each retailer is adopting the modular concept to focus on its business philosophy. Jet’s prefabricated petrol sta- tions consist of five modules, whilst Esso’s approach is to use only two standard modules with prefabricated wall panels forming the customer service area, allowing a more flexible design layout. This method also reduces transport costs from five lorries to only two.

Petrol station retail outlets

3.5 Institutional applications (schools, universities, etc.) There is considerable overlap between this category and residential projects (Section 3.1).

- 67 -


~

Example 3.4 Second Severn Crossing


Various post and panel systems for low to medium rise, e.g. CLASP UK, Panablok UK (Case Study 4.1.4, p. 104).


Not common except for residential blocks, see Section 3.1, p. 54.


‘Temporary’ classrooms, modular teaching areas etc., for example Terrapin UK in use since 1960s and 1970s Provision of additional facilities for existing buildings, Example 3.3.

Example 3.3 Prison kitchens

Wandsworth Prison in London used off-site fabrication to provide an additional 600 m2 of kitchen space using modular building techniques The 12 m x 3 m x 3.2 m units cost less than &950/m2 which was estimated to be 30% less than the traditional construction method (anon, 1991).

3.6 Civil engineering applications The civil engineering sector is very broad and therefore hard to define for the purposes of this book. The definition used here is ‘major construction projects whose main constituent part is not buildings or process plant’ for example roads, bridges and dams


Many and various applications in most countries Examples include project-specific (made to order) items such as precast concrete structural sections for bridges, prefabricated structural steel sections, precast or preformed foundation pile sections and prefabricated reinforcement cages

This major civil engineering project provides a second bridge crossing over the River Severn between England and Wales and utilised off-site fabrication extensively. Laing- GTM chief engineer Neil Kitchener explains (Kitchener and Mizon, 1997) that the main bridge was designed as a cable-stayed structure, using in situ concrete pylons with a composite steel concrete deck. The viaducts were designed as a pair of concrete box-girders to be erected using glued segmental balanced cantilever techniques The

1 - 6 8 -

APPLICATIONS

Figure 3.13 Second Severn Crossing. Courtesy of Laing-GTM.

foundations for both structures were designed generally as spread foundations, using precast concrete caissons. This project could not have been attempted without the use of off-site fabrication. This example is developed further in Case Study 4.1.6, p.113.

Acknowledgements This exumple wus compiled from information provided by Neil Kitchener und David Lloyd of Luing-GTM.

Example 3.5 Rosyth Royal Dockyard: Z Caisson of Precast concrete

The Sl.8 million Rosyth Royal Dockyard Z Caisson, built by the Costain Taylor Woodrow Joint Venture, won the prestigious British Construction Industry award in

- 69 -


1996 in the small project category (anon, 1997a). The project comprised a caisson gate to be installed into an existing dry-dock used for nuclear submarine refitting. Traditionally such caissons have been constructed from structural steel, whereas this project used precast concrete. Design and construction time was only nine months The 20 m x 30 m x 15 m caisson weighing 6500 tonnes was slipformed in an adjacent dry-dock. This technique minimised construction joints and allowed a fabrication time of just twelve weeks Following fabrication the dock was flooded and the caisson floated into its final position and ballasted down onto a prepared base (Figure 3.14). Project credits

Babcock Rosyth Defence/MoD Client Babtie Group Engineer Taylor Woodrow/Costain JV Contractor


Not so applicable for civil engineering except for specific items of plant, etc.


Not so applicable for civil engineering except for ancillary buildings, etc.

Figure 3.14 Z Caisson beingfloated into itsfinal position. Courtesy of Costain Taylor Woodrow JY

- 70 -

APPLICATIONS

3.7 Engineering construction applications The engineering construction sector includes the construction of facilities for the process plant, petrochemical and power generation industries. Compared to most of the sectors described previously, engineering construction prioritises the plant or facility itself, with the structure and building being required only to enclose the machinery or plant. Similarly, this sector is generally concerned with the speed of the overall project giving the earliest possible ‘power-on’ date with the subsequent commencement of production. The use of pre-designed pre-assembled units is seen by many as a neces- sary requirement to achieve these goals. This sector is dominated by US-owned and controlled organisations In a survey of the USA engineering construction sector, working on plants both within the US (20Y0) and elsewhere (SO%), more than 85% of clients stated that they would build more modular facilities in the future and 90% considered that modular construction increased competitiveness (CII 1994).


Non-volumetric examples generally cover the enclosing building frame and cladding.


Typical applications often include the modular construction of the process plant itself, complete with supporting structure. In this way all the work for a particular section of the plant is fabricated, assembled, inspected and tested off-site, leaving only the final commissioning element for the on-site team. Such items are often called ‘vendor packaged units’ and include items such as pumps, heating units or exhaust systems (Exam- ples 3.6-3.8). The Singapore Aromatics Plant is presented in Case Study 4.2.4, p.139.

Example 3.6 Bear Canyon geothermal power plant

This 20 MW geothermal power plant in the USA utilised off-site fabrication for most of its elements. Modular units were provided for turbine generators, gas removal equipment, air compressors and accessories, fire water pumps and accessories, electrical equipment modules and emergency diesel generators The turbine generators weighed 96 tonnes and measured 11 m X 4 m X 4 m. The interface between modules was limited to wiring for power and controls and external piping connections

A four-month saving (15%) was made in design and construction duration, compared to the original planned traditional construction method. The units required heavier lifting equipment, but there were fewer lifts. The project team claimed cost savings of 3% for the design, construct and start-up of the plant, as well as additional revenue from the early commissioning (Phair, 1989).

Example 3.7 Calgary Refinery unit, Canada

The engineering construction sector has been at the forefront of off-site fabrication for

- 71 -


many years. This example shows the extent of off-site fabrication (often called ‘modularisation’ in this sector) in the early 1980s. There have been further developments in off-site fabrication in the sector since the 1980s as reflected in Case Study 4.2.4, p. 139.

The Calgary Refinery is a petroleum facility in Alberta, Canada. Modularisation reduced the project period by three months compared to the predicted traditional in situ approach mainly due to the reduction of the influence of inclement weather by moving works off-site. Calgary was one of the first major projects in North America to use modularisation and it comprised 120 module% 30 of which were pipe rack modules and 90 process modules

Table 3.1 shows the extent of modularisation on the project. Modules were fabricated in three manufacturing facilities in Calgary. Maximum module sizes were 12.2 m X 6.7 m X 5.6 m, weighing up to 40 tonnes in order to meet access restrictions on the roads between the manufacturing facilities and the site.

Example 3.8 Petrochemical Plant, Illinois, USA

This project comprised the replacement of a high pressure polyethylene reaction system with a low pressure system to achieve lower operating costs and a broader range of product capability, for Northern Petrochemical Company. The main aim of the project was to complete the change with the minimum disruption of operation of the

Table 3.1 Adapted from Glaser & Starkey, 1982.

Extent of rnodulurisution on Culgary Refinery unit.

Number of Units Percent Equipment Total Modulurised Modulurised

Pumps 64 Compressors, fans 6 Towers 8 Drums, reactors 36 Shell &tube exchangers 22 Air coolers 16 Stack 1

Miscellaneous 33 Air preheater 1

62 0 0

23 21 0 0 0

10

97 0 0 64 96 0 0 0

30

Totals 187 116 62

Notes: 57% of all piping was on modules expansion joints, etc.

Miscellaneous included ejectors, cranes,

- 72 -

existing plant. The key aspect therefore was to achieve the shortest possible on-site time and to ensure that the on-site performance was achieved as this had to incorporate expensive shut-down periods Predictability of performance was essential. Off- site fabrication was used and achieved a40% reduction in construction time (1 5 months to 9 months) with a reduction in project costs of between 5 and 10% through increased productivity (40%) and reduced on-site time. The modules were fabricated in West Virginia by Union Carbide, and fabrication did not start until the design was 100% complete and 80% of the materials were in hand. In this way the predictability of the project outcomes was assured.

The CII MODEX system (see Section 5.4) was used to evaluate the modularisation strategy. The combined analysis recommended modular construction with a confidence factor of 55%. Table 3.2 gives more detail of the MODEX analysis

Table 3.2 Illinois. Adapted from CII, 1994.

MODEX follow-up analysis on Norchem Plant,

Factor Confidence in Modular Construction

Plant location 45% Labour considerations 61% Plant characteristics 58% Environmental & organisational 61% Project risks 59%


True modular building examples tend to be where a relatively small scale facility is provided and the structure and envelope for the whole building can be incorporated within the unit itself (Example 3.9). In most cases in engineering construction the structure and cladding (which may themselves be fabricated off-site) are installed separate from the plant itself.

Example 3.9 Thames Water waste water treatment plant

Thames Water Utilities, which supplies water to the London region, has developed the Thames Flooded Filter (TFF) to perform the biological phase of sewage treatment (Lock, 1992). TFF is a modular two-stage process comprising a series of prefabricated epoxy-coated steel tanks in containers Further units incorporate control, pump- ing and air-supply plant. Each unit, weighing around 18 tonnes and measuring 9 m X 3 m X 4 m, is installed onto a prepared concrete base after which all pipework and electrical connections are made.

A TFF unit can be installed within six months from placement of order and costs around 30% less than conventional units constructed in situ. When a plant needs to be

- 73 -


extended more units are supplied adjacent to the existing units, which is considerably more straight forward than is the case with conventional treatment plants

3.8 Offshore applications




This application was basically the birthplace of modular units, with most offshore platforms comprising a number of fully finished modular units The remote location of offshore platforms is a major factor in the use of volumetric off-site fabrication as much as possible. In situ construction of offshore platforms would not be realistic.

Figure 3.15 shows the extent of topside modules for a large oil and gas producing platform, and Example 3.13 describes the replacement of off-site fabricated modules for an offshore platform as part of a major refurbishment. Further consideration of the offshore sector is outside the scope of this book.


In a sense, many of the volumetric units described in section 3.8.2 are actually modular building applications in that the units form the complete building element.

3.9 Building services applications Building services are, of course, incorporated into all of the buildings and structures mentioned previously in this section. However, their prominence in the field of off-site fabrication justifies a separate mention. The UK’s Building Services Research and Information Association (BSRIA) is benchmarking the effective use of off-site fabrication in the building services sector (BSRIA, 1998).

Several years earlier, in a marketing report for BSRIA, Cuell(l991) recorded that E84 million was spent on prefabricated building services equipment in the UK in 1989 towards the end of the commercial building boom. Of this, E8 million was spent on packaged boiler houses, E21 million on air conditioning, E25 million on toilet modules, E18 million on generators and E12 million on electrical switchgear (see Figure 3.16). Commercial offices (36%) and retail buildings (28%) were the most common users of prefabricated building services equipment in the 1989 survey. Building services applications are also described in Case Study 4.1.3, p.98.


Examples include prefabricated pipework, multi-service distribution modules, and multi- service riser shafts

- 74 -

APPLICATIONS

MO4 NORTH WELLHEAD MODULE MO6 SOUTH WELLHEAD MODULE MO7 CENTRAL ACCESS MODULE-EAST MO8 CENTRAL ACCESS MODULE-WEST M10 INJECTION COMPRESSION MODULE M11 RECOMPRESSION MODULE M12 MAINFOLD MODULE M13 REFRIGERATION MODULE M15 MAIN GENERATION MODULE M16 STABlLlSATlON MODULE M17 GENERATION MODULE M18 PROCESS UTILITIES MODULES M21 WORKSHOP 8 CHEMICAL

INJECTION MODULW

M24 SERVICES 8 ELECTRICAL MODULE

LO1 SOUTH LIVING QUARTERS L02 CENTRAL LIVING QUARTERS L03 NORTH LIVING QUARTERS LO4 LIVING QUARTERS SERVICES H01 HELIDECK= HO2 HELICOPTER HANGAR

W11 DRILLERS STORAGE &

W12 LIQUID MUD MODULE W15 DRILLING SUPERVISION MODUL W16 OFFICE MODULE W17 CHANGE ROOM MODULE W20 SKID RAILS INFILL SECTION

POWER DISTRIBUTION MODU

Figure 3.15 producing platform. Adapted from Bent, 1988,Figure 3.

Module fabrication arrangement f o r topsides of a large, North Sea

- 75 -


Electrical Switchgear Packaged Boiler Houses f12M E8M

/?-Air Conditioni E21M Generators

- Toilet Pods Overall UK Building Services 1989 ‘Spend’ f25M

on Prefabrication = f84M

Figure 3.16 Financial breakdown of the prefabricated building services sector in 1989. Adapted from Cuell, 1991.

One of the most prominent of London’s 1970s buildings is the NatWest Tower in the City of London. Waters (1981) explains that a major achievement of the services contractor was the ‘high degree of prefabrication in the design.’ From this early begin- ning the prefabrication of services has developed into a complex business

The development of prefabricated services now extends to horizontal services Bunn (1995) reports on the current refurbishment of the NatWest Tower, where 80% of the vertical and horizontal HVAC services are being prefabricated.

3.9.2 Vohnetric application examples

Examples include plant rooms, boiler houses, air handling units, and toilet pods. Chevin (1991) illustrates how vertical service riser shafts were incorporated into a

major project on London Wall, London (Case Study 4.2.3, p.136). Having used prefabrication for service risers, the logical next step for service contractors was to develop prefabricated plant rooms, air-handling units and boiler houses One of the larg- est boiler houses installed in the UK is detailed by Nealeet al. (1991). A well designed off-site fabricated plant area for a chiller and boiler can result in a 30% space saving over a conventionally built alternative (anon, 1991).

Prefabricated lifts, complete with motor room, have been developed and installed in a project at 20 The Old Bailey (Chevin, 1991) (see also Case Study 4.2.5, p.148).

One of the earliest UK success stories for volumetric off-site fabrication of building services was the prefabricated toilet units installed at Triton Court in London’s Finsbury Square, redeveloped under archtects Sheppard Robson (Hannay, 1985). Unlike later models, used extensively in the 1980s, these forerunners were not of sophisticated construction. Gibb (1994) details how modern steel-framed toilet pods were incorporated within two fast-track developments to satisfy their respective clients’

- 7 6 -

APPLICATIONS

objectives. Case study 4.2.1 (p.128) describes precast concrete toilet units for a major hotel refurbishment.

One of the most striking buildings to incorporate off-site fabricated volumetric units is Richard Rogers’ Lloyd’s building. The heavily sculptured exterior facade includes prefabricated toilet and staircase units stacked on top of one another. In a more subtle display at the Channel Four building, Victoria, London, Rogers again uses prefabricated services units to create distinctive external features


Building services are, of course, integrated into most modular building applications off-site. In addition the services may be prefabricated prior to installation. However, complete modular buildings for building services are obviously not applicable except for stand-alone plant facilities (Example 3.9).

3.10 Temporary, emergency and relocatable applications Section 2.10 describes the reusability and relocatability of off-site fabricated units and provides several examples (Examples 2.7,2.8,2.9). In some cases the buildings may be intended for temporary, or for emergency, short-term or repeated use at several different locations Further applications are given in Examples 3.10 and 3.1 1.

3.10.1 Non-volumetric application examples Panellised buildings are readily relocatable Panellised buildings for construction site

Panellised buildings for emergency

Panellised buildings for major public gatherings Most countries

3.10.2 Volumetric application examples Power generation and services modules for use at major public gatherings, etc.

3.10.3 Modular building examples Modular buildings for emergency

accommodation Especially after major disasters Flat-pack modular units for emergency

accommodation, to reduce transport costs Construction site accommodation (ofiices,

toilets, etc.) Most developed countries Modular buildings for major public gatherings Most developed countries

accommodation Most countries

accommodation Especially after major disasters

- 77 -


Example 3.10 Emergency classrooms for Romanian orphans

A series of sectional timber-framed classrooms were supplied by Wernick Buildings to an orphanage in a remote part of Moldavia, eastern Romania, to provide teaching space for 118 people with special educational needs (anon, 1991).

I - 7% -

Example 3.11 Two-bedroom modular homes for emergency resettlement in the Caribbean

In 1997, the Caribbean island of Montserrat, a British protectorate, was devastated by volcanic eruptions The British Government offered a E6.5 million aid package, part of which included the provision of a thousand modular homes The prefabricated two-bedroom homes, costing &12 000 each, were located at Davy Hill, at the northern tip of the island, remote from the lava flow. The timber and plasterboard units were fabricated off-site including bathrooms, kitchens and all fuctures Final assembly was completed on-site with the installation of a metal roof Strictly speaking the units are not temporary, in that they are expected to be in use for more than 10 years. However, they demonstrate the ability of the modular building sector to respond to emergencies (anon, 1997b). Project credits

International Building Systems, Texas Manufacturer Root & Brown Project Manager

3.11 Remote sites applications This category covers projects that are located far from other civilisation or adequate sources of materials or labour (Example 3.12). This is often one of the key project parameters that will lead to an off-site fabrication strategy being adopted (Case Study 4.2.4, p.139).






Most often used, as maximum prefabrication is usually a requirement. Units may be flat-packed to facilitate transport logistics

I I

APPLICATIONS

Example 3.12 Oil Sands development project, Venezuela

The Oil Sands development project is a production and processing facility in a remote location in Venezuela’s Orinoco Valley.

Remoteness and transportation of labour The project is located in a sparsely populated region on the north bank of the Orinoco river about 50 km from Ciudad Guyana, a city of 350 000 which was home to most of the workforce. Transportation of workers to site was by bus and ferry as there were no bridges or tunnels, a journey of around three hours each day. This transportation of labour was both costly and time consuming. Off-site fabrication helped to reduce the need for on-site labour with savings in cost and time.

Broader benefits Several other benefits were cited for off-site fabrication, namely (Glaser & Starkey, 1982):

Workload and employment opportunities shared among various parts of the country

Optimum use of national resources and transfer of technology to local businesses Broad-based development and improvement of local pre-fabrication facilities Training additional craftsmen and supervisors throughout the country

3.12 Refurbishment applications The maintenance and refurbishment market represents more than a quarter of total construction output in the UK. Off-site fabrication is particularly suited to refurbishment, although its use has not yet been fully realised. One reason for this is that buildings that are now being refurbished were often constructed before prefabrication was as viable as it is today, or at least the prefabrication that was chosen paid no attention to life-cycle issues, such as maintenance or refurbishment.

Clearly, a prefabricated plant room at roof level is relatively easy to replace, with minimum disruption to the users of the building. This would be similar for other prefabricated elements providing they were not installed in the original building in a sequence that would require large parts of the building fabric to be dismantled to enable the units to be removed and replaced. Where there is the possibility of later refurbishment, this needs to be considered carefully when planning the design and sequencing of the initial construction project. Modularisation of plant modules for petrochemical or power generation facilities is driven partially by the benefits from the ease by which modules can be replaced at a later date (Example 3.13). Furthermore, the use of off-site fabricated units in the refurbishment of older properties is an application that can be very effective (Case Studies 4.2. I , p. 128 and 4.2.2, p. 134). In Fin- land, prefabricated bathroom modules have been stacked on the outside of 1960s residential tower blocks as part of a major refurbishment project (Taylor, 1997).

- 79 -


Example 3.13 Trinidad offshore modular living quarters

Amoco Trinidad operates several major oil-fields off the eastern coast of Trinidad and Tobago in the West Indies Since the initial offshore hydrocarbon discoveries during the late 1960% several offshore drilling and production steel jacket structures have been set to develop the offshore oil-fields Over time the personnel accommodation had become outdated and needed to be modified. After reviewing several accommodation options, including single lift quarters using a derrick barge, Amoco Trini- dad determined that a modular construction approach offered suitable economics, provided excellent construction schedule flexibility and met all accommodation re- quirements for future offshore operations Project goals included improving offshore safety, quality and organisational goals, and facilitating the integration of the offshore maintenance and production staffs from several platforms into a single operations-oriented staff. To accomplish these goals the existing quarters were replaced with a three-storey, modular steel design that could be assembled with existing labour and equipment. The platform modifications increased the offshore accommodation from 85 to 156 personnel (84%), and provided reliable offshore accommodation for living, recreation and business for the following 20 years The project exceeded the original constructability and quality expectations and met the economic and schedule goals (Jennings, 1994). Success factors:

Costs were controllable and were held exactly to the approved budget. The modular plug-in methodology yielded a very high quality product with mini-

mum offshore efforts. Lessons learned:

Detailed design engineering is critical for successful field installation. Modular projects should be test assembled to the fullest extent possible at the

Close attention to final location construction capability is essential. Client input and expectations must be absolutely finalised prior to modularisation. Large offshore quarters can be effectively constructed with modular methods.

fabrication site.

References anon, 1997a. British Construction Industry Awards, NCE, Emap Business Communications,

London, 24 October, IV-V & VII-E. anon, 1997b. A thousand prefabs for volcano-stricken island. Building Design, September 19,

4. anon, 1991. Prefabricated Construction. Building, The Builder Group, London, 6 Septem-

ber, 59. BSRIA, 1998. Report on Prefabrication and Preassembly in the Building Services Sector. Avail-

able from Building Services Research and Information Association, Bracknell, Berkshire, RG12 7AH, UK.

-80-

APPLICATIONS

Bent, J. A., 1988. Modular Design and Construction. AACE Transactions, American Asso- ciation Of Cost Engineers (32nd Annual Meeting) And The 10th International Cost Engi- neering Congress, Ch. 104, 8-14.

CII, 1994. Modularisation I Preassemb/v - Benchmarking implementation results, CII Con@- ence 1994. Construction Industry Institute, Austin, Texas, 20 pp.

Cook, A., 1996. Pump Action. Building, The Builder Group, 12 July, 48-49. Cuell, M., 1991. Opportunities in Prefabrication. Building Services Research and Information

Davies, C., 1986. Building the Bank. Architectural Review, 179, 82-107. Glaser, L. B. & Starkey, A., 1982. How modular plant construction offers improved cost and

schedule controls. 26th Syniposiicm on Utility Cost Management, Houston Texas, ISBN 0930284143.

Jennings, C. W, 1994. Trinidad Offshore Modular Living Quarters, Amoco Production Com- pany, Modularisation / Preassembfy, 1994 CIIConjierence. Construction Industry Institute, Austin, Texas, USA, 3.

Kitchener, J. N. & Mizon, D. H., 1997. Second Severn Crossing-Pre-construction period and design development. Proceedings of the Institution of Civil Engineerg Civil Engineering: Second Severn Crossing, 120, Special Issue 2, 13-21.

Lock, J., 1992. Waste water treatment plant built with modules. Pollution Engineering, April 1, 48-49.

Phair, K. A., 1989. Modular design and construction at Bear Canyon 20 MW power plant. Geothermal Resources Council, Transactions, 13, October, 633-637.

Stevens, J. D. & Murray, A. L., 1994. Modified roof erection system. Journalof Construction Engineering and Management, American Society of Civil Engineers, 120, (4), December, ISSN 0733-9364/94/0004-0828, Paper No. 73 19, 828-837.

Association, Bracknell, BSRIA Report 60870/1.

Taylor, D., 1997. Facelifts for Finland. Construction News, June 12, 26.

- 81 -

<.

o€€-site f abr icatian

Off-site fabrication is a topic of international interest and provides an effective construction

,. .:.technique in terms of quality, time, cost, _ ' fun'&on, '.'-;.,%: , 'productivity ! ._ and safety. It is adopted :woildwide as the ideal means of producing an

.'i&mense .. . array of elements from structural members, cladding units, bathrooms to fully-

fin ish ed m'od u I a r b u i Id i ng s.

. / ! '

. . :.-

. .. I . . . _ . 3 .

. .?.j ' . . .

. .. . rovides a ,complete guide 7. , -, t o , .

the principles, a ppl ica tidns s for design .and construction.

cas' e studies .and 'examples'from world illustrate the flexibility and

site fabrication. Practitioners, d students in:civil and structural

g, building and construction, ement and related subjects,

will find the book provides;excellent guidance to the technology and its effective implementation.

. . . . , , . i . 1'. . , . . . . I . .. .

W H I l T L E S PUBLISHING

alistair g.f. gibb - trent global fabrication part thre… · · 2011-11-242nd floor 19 bedrooms,...

Documents