Construction Cost Estimating PDF

## Excavation and Construction Cost Estimating 1. An excavator has a bucket capacity of 2.8 yd³. Its operation cycle consists of the following phases: * excavation time = 45 sec * travel time (two-way) = 4 min * dumping/transfer time = 30 sec. Assume an overall efficiency factor fo...

## Excavation and Construction Cost Estimating 1. An excavator has a bucket capacity of 2.8 yd³. Its operation cycle consists of the following phases: * excavation time = 45 sec * travel time (two-way) = 4 min * dumping/transfer time = 30 sec. Assume an overall efficiency factor for the excavator = 85%. The quantity of material to be excavated (bank measure) = 50,000 ft³. The material has the following properties: * Swell = 20% * In situ unit weight = 120 lb/ft³ * Water content = 30% Assuming 8-hr workdays, the number of days required to complete the job is most nearly: * A. 9 * B. 10 * C. 11 * D. 13 2. An excavator has a bucket capacity of 3.0 yd³. Its operation cycle consists of the following phases: * excavation time = 45 sec * travel time (two-way) = 4 min * transfer time (to trucks) = 45 sec. The excavator transfers the excavated material to a fleet of trucks that carry the material offsite. The following data is given: * Overall efficiency factor for the excavator = 90% * Truck capacity = 15 yd³ * Truck cycle time (transfer + two-way travel + dumping) = 90 min * The quantity of excavated material = 2,600 yd³ (loose) The number of trucks needed to balance the production of the excavator, assuming 8-hr workdays, is most nearly: * A. 2 * B. 3 * C. 4 * D. 5 3. The architect for a warehouse building has proposed a design change to ensure compatibility with local building codes. The revised SOW is to substitute one layer of 5/8-in.-thick sheet rock with two layers of 12-in.-thick fire code (FC) GWB and to provide insulation within the wall cavity. The building plan dimensions are: 180 ft × 200 ft * Floor-to-ceiling height: 12 ft * Openings: eight 6 ft 0 in. wide × 10 ft 0 in. high openings | Labor rates | Price | |-------------------------|--------| | Carpenter foreman (working) | $50.00 fully burdened | | Carpenter (journeyman) | $40.00 fully burdened | | Laborer | $25.00 fully burdened | Work crew: * 4 carpenters * 2 laborers * 1 working foreman Work crew productivity (based on 8 hr/day) * GWB installation 960 ft2/L.H. * Insulation 1,920 ft2/L.H. Material costs (add 10% waste factor for all materials): * 4 ft 0 in. x 10 ft 0 in. × 1½ in. GWB (FC) $0.285/ft² * 4 ft 0 in. x 10 ft 0 in. × 5/8 in. GWB $0.255/ft² * Insulation $0.45/ft² Contractor's overhead 10% Contractor's profit 5% The complete cost ($) of the change order for the revised SOW is most nearly: * A. 3,300 * B. 4,200 * C. 9,800 * D. 7,800 4. A 450-ft-long canal (trapezoidal section: 19-ft-bottom width, 3H:2V side slopes) is to be lined with concrete to a nominal thickness of 8 in. Material waste is estimated to be 5%. * Concrete cost = $98/yd³ * Concrete pour rate = 8 yd³/hr * Surface finishing compound is purchased in 5-gal containers costing $40 each * Coverage of surfacing compound = 300 ft²/gal The total material cost ($) is most nearly: * A. 75,000 * B. 85,000 * C. 95,000 * D. 105,000 5. Dump trucks with a capacity of 16 yd³ are used to dispose of excavated materials from a site. The distance from the dump-site is 4 mi and the average speed of the dump trucks is 30 mph. The bucket capacity of the power shovel is 3 yd³; power shovel excavation rate is 10 yd³/min (bank measure); the transfer time to the dump trucks (per 3-yd³ load) is 40 sec; and a dump time (per 3-yd³ load) is 30 sec. The excavated material has a swell of 10%. The factors affecting the job site productivity of the dump truck are: 0.80 for equipment idle time and 0.70 for operator efficiency. If a fleet of dump trucks is used to haul the excavated material, the number of trucks needed is most nearly: * A. 3 * B. 4 * C. 5 * D. 6 6. A certain project includes the activities summarized in the table below. The start date of the project is week 0. The project duration (weeks) is most nearly: * A. 32 * B. 36 * C. 41 * D. 44 | Activity | Predecessor Activities | Duration (weeks)| |---------|------------------------|----------------| | Start | - | - | | A | Start | 8 | | B | A | 6 | | C | A | 7 | | D | B | 8 | | E | C, D | 7 | | F | E | 7 | | G | F | 8 | | Finish | G | - | 7. A 6-in.-square unreinforced-concrete beam is loaded in third-point loading on a simple span of 5 ft. The test is conducted at 28 days after the concrete beam is cast. If the failure occurs by flexural cracking within the middle third of the beam when load P = 800 lb, the 28-day compressive strength (lb/in.²) of the concrete is most nearly: * A. 6,500 * B. 5,500 * C. 4,500 * D. 3,500 8. A 6-in.-diameter x 12-in.-height concrete cylinder fails at a transverse load of 55,000 lb at 28 days in a split cylinder test. The 28-day compression strength (lb/in.²) of the concrete is most nearly: * A. 6,200 * B. 5,200 * C. 4,200 * D. 3,200 9. Normal weight concrete (unit weight = 145 lb/ft³) is placed at a rate of 12 ft/hr into 18-ft-high column forms. The blended cement mix contains 30% fly ash but no retarders. Average concrete temperature during curing is 50°F. The maximum lateral design pressure (lb/ft²) for the design of forms is most nearly: * A. 2,600 * B. 2,760 * C. 2,150 * D. 2,300 10. A temporary road closure (not exceeding 20 min during the daytime) is established around a 1,250-ft long work zone (including a buffer space) on a freeway. The distance (ft) from the centerline of the work zone to the location of the ROAD WORK AHEAD sign is most nearly: * A. 4,800 * B. 5,800 * C. 6,800 * D. 7,800 11. Whenever a masonry wall is constructed, a limited access zone is to be established. Which of the following is true? * A. The limited access zone shall run to the same length on both sides of the wall. * B. The width of the limited access zone shall be wall height plus 2 ft. * C. The width of the limited access zone shall be wall height plus 4 ft. * D. If provided along the entire length of the wall, the width of the limited access zone is based on the judgment of the contractor. 12. According to OSHA, lifelines shall be secured above the point of operation to an anchorage or structural member capable of supporting a dead weight (lb) of at least: * A. 5,000 * B. 4,500 * C. 4,000 * D. 3,200 13. According to OSHA, the limiting exposure (dB) to impulse or impact peak noise level is most nearly: * A. 80 * B. 100 * C. 120 * D. 140 14. A job requires specially engineered fill to be hauled from storage to the job site and then placed and compacted. Given the following information the installed cost ($/yd³) of the fill is most nearly: * Compacted volume required at job site 15,000 yd³ * Distance from storage to job site 32 mi * Average truck speed 32 mph * Truck capacity (net) 50,000 lb * Truck load time 25 min * Truck unload time 10 min * Truck operating cost $80 per hr * Cost of fill at storage facility $3 per ton * Compacted unit weight of fill 140 lb/ft³ * Cost to place & compact fill $0.50 per yd³ The installed cost of the fill is most nearly: * A. 15 * B. 27 * C. 23 * D. 22 15. The following table shows areas of cut and fill sections at locations 50 ft apart. Assume shrinkage = 12% and bulking = 25%. Cumulative earthwork (yd³) between stations 0 + 0.00 and 3 + 0.00 is most nearly: * A. 1,340 * B. 1,850 * C. 2,200 * D. 2,500 | Station | Cut Area (ft²) | Fill Area (ft²) | |---------|---------------|----------------| | 0+00.00 | 563.2 | 342.2 | | 0+50.00 | 213.5 | 213.6 | | 1+00.00 | 123.5 | 343.3 | | 1+50.00 | 654.6 | 111.0 | | 2+00.00 | 973.1 | 762.4 | | 2+50.00 | 567.3 | 342.9 | | 3+00.00 | 451.6 | 190.4 | 16. A contractor has the following options for a project lasting 18 months: * **Option A:** Monthly rental of excavation equipment at $15,000 per month + operating costs $2,000/month * **Option B:** Purchase equipment for $200,000 * Maintenance costs = $8,000/month * Resale value of equipment after 18 months = $120,000 * Nominal interest rate = 10% p.a. The benefit:cost ratio of option B (purchasing) is most nearly: * A. 0.95 * B. 1.25 * C. 1.55 * D. 1.95 17. An excavation plan is outlined in the following figure. Each grid square is 50 ft. × 50 ft. The numbers are depth of cut (ft.) at indicated locations. The total volume of cut (yd³) is most nearly: * A. 4,500 * B. 5,000 * C. 5,500 * D. 6,000 18. An existing landfill, in the shape of a truncated pyramid, is rectangular at the base with plan dimensions 4,000 ft. × 2,500 ft. The free-standing sides slope 3H:1V. The height of the landfill is 12 ft. The top of the landfill must be covered with cover soil to a depth of 18 in. The amount of cover soil (yd³) required is most nearly: * A. 525,000 * B. 650,500 * C. 712,200 * D. 821,435 19. The following table shows ordinates of a mass haul diagram for a highway construction project. The free haul distance is 300 ft. Overhaul cost is $3.70/station-yd. | Station | Cumulative Yardage (yd³) | |---------|--------------------------| | 30+00 | 0 | | 42+40 | 800 | | 45+10 | 1275 | | 47+00 | 1560 | | 46+10 | 1275 | | 50+30 | 680 | | 53+42 | 0 | The total cost of overhaul is most nearly: * A. $35,000 * B. $40,000 * C. $45,000 * D. $50,000 20. The total duration of a project was estimated as follows: * 522 working days at 6 days per week and 10 hr a day of work * 30 days (10 hr per day) for contingencies such as bad weather, which would be worked on weekends and holidays. The labor agreement defines the regular work day as an 8-hr-long week-day. Labor cost for premium time is 50% for hours during the week, and 80% for weekend work. What is most nearly the overall labor premium rate for the project? * A. 1.25 * B. 1.28 * C. 1.31 * D. 1.34 21. A roller is used to compact soil to a specific density. The roller can achieve this target density for a 6-in. layer of material in four passes. The following specifications are given: * Width of roller drum = 8.0 ft * Forward speed of roller = 3 mph * Overall efficiency of roller = 80% * Soil shrinkage = 15% The material delivery rate (bank measure) to the site is 950 yd³/hr. The number of rollers required to keep up with this material delivery rate is most nearly: * A. 1 * B. 2 * C. 3 * D. 4 22. A 14-ft-high wall is placed at a rate of 4 ft./hr. Concrete is lightweight (135 pcf) made with Type I cement and a retarding admixture. The average concrete temperature is 60°F. The lateral design pressure exerted by the fresh concrete is most nearly: * A. 870 * B. 750 * C. 900 * D. 725 23. Specifications for a construction job state that wall forms can be removed once the concrete reaches a compressive strength of 3,400 psi. The maturity curve (Nurse-Saul) for the concrete is shown in the figure below. The cement hydration is assumed to cease below a temperature of 30°F. The average temperature of the concrete during the curing process is 70°F. The number of hours that the contractor has to wait before removing forms is most nearly: * A. 24 * B. 36 * C. 48 * D. 60 24. An activity on an arrow network for a project is shown below. Numbers adjacent to arrows are activity durations (weeks). The total float (weeks) for activity G is: * A. 1 * B. 2 * C. 2 * D. 3 25. As part of the PERT analysis of a project, durations are estimated for activities A through G and summarized in the table below. The critical path for the project is ACEF. | Activity | Optimistic Duration (weeks) | Most Probable Duration (weeks) | Pessimistic Duration (weeks) | |---------|------------------------------|------------------------------|------------------------------| | A | 3 | 4 | 5 | | B | 4 | 5 | 7 | | C | 5 | 7 | 8 | | D | 3 | 4 | 5 | | E | 5 | 6 | 7 | | F | 7 | 9 | 10 | | G | 4 | 5 | 6 | The probability (%) that the project will be completed in less than 25 weeks is most nearly: * A. 12 * B. 18 * C. 20 * D. 22 26. A new earth haul project requires moving 323,000 ft³ (bank measure) of excavated material to a location 12 mi away. A bidding contractor had completed a similar project (size and scope) 2½ years ago. The proposed price for the job on record was $525.00 per dump-truck load. Annual construction inflation factor is 3.2%. The contractor uses a fleet of dump trucks with 26-yd³ capacity (heaped). The excavated material has a swell factor of 25%. The contractor's bid ($) should be most nearly: * A. 262,000 * B. 302,000 * C. 326,000 * D. 353,000 27. A building construction site is represented by the following rectangle ABCD. The original elevation of the water table at the site is 325.8 ft (above sea level). The dashed line shows the limits of proposed construction. The bottom elevation of the mat foundation for the building is 325.65 ft. Steady state pumping from a 9-in.-diameter well at point B is to be used to lower the GWT. The transmissivity of the underlying aquifer is 250 ft²/hr. During construction, the GWT must be lowered to at least 5 ft. below the bottom of the foundation and no higher than an elevation of 324.0 ft. within the limits of the site. The minimum steady-state pumping rate (gal/min) required is most nearly: * A. 1,000 * B. 1,500 * C. 2,000 * D. 3,000 28. A contract has 90 days remaining until completion. Early completion will be paid $18,000 bonus per day that the duration is shortened. Activities on the critical path are targeted for "crashing." Critical activities can be accelerated by allocating additional crew units. Additional cost and schedule reduction are shown in the table below. If crews must be added as a complete unit, the net bonus is maximized by the addition of how many crews? * A. 1 additional crew unit * B. 2 additional crew units * C. 3 additional crew units * D. None of the crashing schemes are profitable | Crew Units Added | Added Crew Cost per Day | Schedule Days Reduced | |-------------------|---------------------------|-----------------------| | 1 | $3,200 | 15 | | 2 | $6,000 | 21 | | 3 | $9,000 | 31 | 29. The activity on a node diagram for a project is shown below. All durations are in weeks. All relationships are finish to start unless noted otherwise. The free float (weeks) of activity A is: * A. 0 * B. 1 * C. 2 * D. 3 <start_of_image> Schematic: A node diagram with nodes representing activities and arrows showing the sequence and duration. 30. All costs for a construction project are classified as either direct costs (material, labor, etc.) or indirect costs (leasing and rental costs, utilities, etc.). The estimated variation of these cost categories vs. project duration (weeks) is shown. The optimum project duration (weeks) is most nearly: * A. 10 * B. 13 * C. 16 * D. 19 31. A 5-story structure steel frame is to be constructed. Story height is 12 ft. The maximum tolerance for out-of-plumbness of the columns (in.) at the fourth floor is most nearly: * A. 0.25 * B. 0.65 * C. 0.95 * D. 1.15