productivity of construction equipment

Productivity of Construction Equipment

Mansoor Azam QureshiNUST

April 10, 2023Mansoor Azam Qureshi 2

Pro

du

ctiv

ity

Genera

lD

efin

ition

It is the number of units and the size of equipment that would

permit the constructor to accomplish the activity with a

duration resulting in the lowest cost.

Estimating and planning involves the judicious selection of equipment, the careful scheduling of time and

resources, and the accurate determination of expected system output and cost.


Factors Affecting Productivity

Haul unit horsepower Haul road rolling resistance Haul road grades Haul unit loaded and empty weight Haul unit transmission characteristics Haul unit loading time Haul unit travel time Haul unit delay time Altitude of the project site


Haul Unit Horsepower Total power that an engine is capable of

generating is expressed as its horsepower. Available horsepower is power that is

available to perform work after taking into account losses and consumption in other machine functions. It is product (HP x efficiency)

Rimpull is defined as the tractive force between the driving wheels and the surface on which they travel.( V is velocity in mph)


Machine Power

Power generated by engine

Drawbar Pull

Rolling Resistance

Rimpull


Rolling Resistance Rolling resistance is resistance offered to movement of

materials on a plain surface; often expressed in pounds per ton of materials.

Rimpull minus rolling resistance gives force available for acceleration and velocity.

Rolling Resistance depends upon:


Typical Rolling Resistance


Road Gradients

The force-opposing movement of a machine up a frictionless slope is grade resistance.

The effect of gravitational force in aiding movement of a vehicle down a slope is grade assistance.

F= 20 lbs/ G% per Ton


Load and Traction Traction is force developed between the

driving wheels or tracks and the haul surface. Traction is function of Surface conditions and

load on powered running gear. The coefficient of traction can be defined as

the factor by which the total weight on the drive wheels or tracks should be multiplied to determine the maximum possible tractive force between the wheels or tracks and the surface just before slipping will occur.

Usable force = Coefficient of traction X Weight on powered running gear


Coefficient of Traction


Load on Powered Running Gear


Loading Time

Time to load a mover for load shifting will determine no of loads that can be transferred. Longer loading time lesser will be productivity.

Te is cycle time for loader Ch is capacity of a hauler Ce loading rate/capacity of loder


Travel Time

It is time for moving load from production site to disposal site. Longer time will reduce productivity.


Delay Time

Human and machine system suffer from inherent delays due to reaction time and capacity.


Productivity Measurement

Material properties have a direct effect on the ease or difficulty of handling the material, on the selection of equipment, and on equipment production rates.

Quantities are often measured in volume units. Volume of material under different conditions

varies appreciably.


Volume Measures


Volu

me R

ela

tions

Sw

ell Fa

ctor

Shrin

kag

e

Facto

r

The swell factor is the ratio of the loose dry weight per unit volume to the bank dry weight per unit volume.

Loose dry unit weightSwell Factor = _______________________

Bank dry unit weightSwell% = ( 1/SwF – 1 )x100

The shrinkage factor is the ratio of the compacted dry weight per unit volume to the bank dry weight per unit volume:

Compacted dry unit weightShrinkage Factor = _________________________ Bank dry unit weightShrinkage % =( SrF – 1 )x100


Size of the job: Larger volumes of excavation will require larger excavators, or smaller excavators in greater number.Activity time constraints: Shortage of time for excavation may force contractors to increase the size or numbers of equipment for activities related to excavation.Availability of equipment: Productivity of excavation activities will diminish if the equipment used to perform them is available but not the most adequate.Cost of transportation of equipment: This cost depends on the size of the job, the distance of transportation, and the means of transportation.Type of excavation: Principal types of excavation in building projects are cut and/or fill, excavation massive, and excavation for the elements of foundation. The most adequate equipment to perform one of these activities is not the most adequate to perform the others.Soil characteristics: The type and condition of the soil is important when choosing the most adequate equipment since each piece of equipment has different outputs for different soils. Moreover, one excavation pit could have different soils at different stratums.Geometric characteristics of elements to be excavated: Functional characteristics of different types of equipment makes such considerations necessary.Space constraints: The performance of equipment is influenced by the spatial limitations for the movement of excavators.Characteristics of haul units: The size of an excavator will depend on the haul units if there is a constraint on the size and/or number of these units.Location of dumping areas: The distance between the construction site and dumping areas could be relevant not only for selecting the type and number of haulers, but also the type of excavators.Weather and temperature: Rain, snow and severe temperature conditions affect the job-site productivity of labor and equipment.


Example

A front-end loader loads a fleet of dump trucks (capacity 18 loose cu yd each), which haul the earth to a fill where it is compacted with a shrinkage factor of 10%. The earth has a percent swell of 20%. The job requires a volume of 18,000 compacted cu yd. Distance between quarry and project site is 5miles connected with dirt track.

How many hours will be required to excavate and haul the material to the fill.

April 10, 2023 21

Loader Capacity A front end loader with a 2 bank cu yd bucket capacity

is available to load dump trucks. Determine its capacity if operator work for 50 min in an hr. Time for various activities are shown in solution. Determine its productivity.

Calculate cycle time› Move to stock pile 0.10 min› Fill bucket 0.10 min› Move to truck and maneuver to load 0.2 min› Dump loaded bucket 0.10 min› Total cycle time 0.50 min

No of cycle per hr= 60/Cycle time 120 C/hr Productivity = 120x2x50/60 = 200 bank cu yd per hr

Mansoor Azam Qureshi


Loader Working Total volume of compacted fill Vc=18000 cu yd Shrinkage % = 10% Volume in Bank Measure = V/(1-sh%/100) Vb = 18000/(1-0.1) =20000 cu yd Volume to transported is loose form(Vl) =Vb x (1 + Swell%/100 Vl= 20000x(1+0.2) = 24000 cu yd Loader Production (bank) = 200 cu yd/hr Loader Production (loose) = 200x1.2 = 240 cu yd/ hr Loader time =24000/240 = 100 Hrs


Dump Truck Capacity

Capacity depends upon hp, haulage distance , track conditions and turn round time.

Profile of track for haulage is shown along with rolling resistance and gradient


Horse Power of dump truck converts into rimpull at wheels which required to move load by over coming resistances

Rimpull or power required in pounds to over come resistances is shown for 70 ton truck.

Speed and rimpull available at wheels for different gear rattios for selected truck as given by manufacturer are shown


Rimpull at rated hp.

Suitable speed and travel time for travel are shown for each one mile sec.

Sec Res lb Gear Speed Time› 1 4200 5 22.6 mph 2.65 min› 2 11200 3 8.1 7.41› 3 5600 4 13.8 4.35› 4 0 5 22.6 2.65› 5 2800 5 22.6 2.65 › Total time loade travel 19.71› Time for back move 13.25› 33 min

productivity of construction equipment

Education

ton mansoor azam qureshi21

x100 mansoor azam qureshi21

mph mansoor azam qureshi21

unit volume

bank dry unit weight

size of equipment

adequate equipment

bank dry weight