# Ce 556 Chapter 16 Review Questions

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## Essay Preview: Ce 556 Chapter 16 Review Questions

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Chapter 16 Review Questions: 1, 2, 3, 5, 6

Chapter 17 Review Questions: 1, 2, 3, 6

## Chapter 16

Q1. Can you produce an accurate forecast of the cost of a project using the cost-per-unit method of estimating? Explain.

A1: It is possible to get an accurate forecast of a project’s cost by using the price-per-unit, but it can only be accurate if the future project is nearly identical in size and scope to the past projects from which the unit pricing was obtained. This includes such similarities as the size of the project, the overall finish quality, the physical location of the work, and the time of year in which past work was done, and the future project is to be done. If the differences in these particulars are drastic, the accuracy of the cost estimate will be questionable, and adjustments to improve the accuracy will be difficult if not possible.

Q2. Describe the cost-per-unit-area method of estimating, and give an example of an estimate produced by this method.

A2: Here the unit of analysis is the square foot or square meter of gross floor area of the project. The gross floor area is defined as the area of all floors measured to the out- side of containing walls. As with the previous method, the analysis begins with the construction cost of a completed project. The known project construction cost is divided by the gross floor area of the project to obtain a cost per unit area, which can then be applied to future projects to estimate their construction cost.

For example, suppose a 50,000-square-foot office building of a certain type was built in a certain place for \$9,850,000. Therefore, the unit cost is \$9,850,000/50,000, or \$197 per square foot. A similar 39,000-square-foot office is proposed, so the estimated price is 39,000 × \$197 = \$7,683,000.

Q3. Suggest why the cost per unit area is the most popular method of preliminary estimating.

A3: The unit area method has several strengths:

1. Produces an estimate quickly.
2. Little data required for the calculation—just the gross floor area (GFA) and the projected cost per square foot.
3. As a rough check on estimates.
4. One design can be compared with another.
5. A large amount of data is published on unit area costs.
6. Widely used and understood.
7. Easy to communicate to laypeople.

Q5. Why is the assembly method of estimating more accurate than any of the single- rate methods?

A5: Assembly estimating can be a powerful cost control tool since the nature of the assembly, materials, and construction methods can all be defined and these data reflected in the estimated price. The accuracy is dramatically improved because the quality, shape, size, and construction type can all be considered using this method. It still allows building prices to be estimated quickly because all of the components can be reduced to a relatively few number of assemblies.

Q6. Calculate a unit price (each) for the pile cap assembly shown in Figure 16.7 based on the same unit rates as the grade beam assembly shown in Figure 16.6. Make the unit price of pile cap forms the same as that for grade beam forms and the price of #6 rebar \$1.52 per pound.

A6: Excavation width at bottom= (24+36+24)/12=7 ft

Excavation width at top= 7+(128-123)/2×2=12 ft

Excavation volume = Average Length × Average Width × Average Height

= 9.5 × 9.5 × 5= 451.25 cu ft = 16.71 CY =17 CY

Volume of Pile Cap = 3×3×32/12 = 24 cu ft = 0.89 CY = 1 CY

Backfill volume = Excavation volume – Volume of Pile Cap

= 451.25- 24 = 427.25 cu ft = 15.82 CY= 16 CY

Pile Cap Forms = 3 × 4 × 32/12 = 32 SF

Total Rebar weight= 1.502 lb/ LF ×3 LF ×5 =22.53 lb

 Pricing Pile Cap Assembly(Price per CF based on 24 CF) Item Quantity Units Unit Rate (\$) Total(\$) Excavation 17 CY 3.2 54.40 Backfill 16 CY 13.5 216.00 Remove Surplus 1 CY 8.25 8.25 Concrete Piles 1 No. 850 850.00 Pile Cap Forms 32 SF 5.3 169.60 Concrete -Placing 1 CY 28 28.00 -Material 1 CY 132 132.00 # 6 rebar 23 lbs 1.52 34.96 Total 1493.21 Price per Cubic feet = 62.22 ( including pile) Price per Cubic feet = 26.80 (without pile)

## Chapter 17

Q1. Why is a trade breakdown of the cost of construction preferred by contractors?

A1: Contractors prepare their cost estimates largely by obtaining prices for each of the trades involved in a project, so a trade breakdown is most useful to them. However, a trade breakdown is far too detailed for the preliminary type of estimate prepared at the conception stage of a project. A breakdown on a functional basis is less detailed and reflects the systems approach taken by designers; this makes it easier for estimators to work with designers.

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