6.5 Construction Principles: Design Requirements, Project Organization, Cost Control, and Value Engineering

6.5 Construction Principles: Design Requirements, Project Organization, Cost Control, and Value Engineering

The AMSTHC TOS area "Construction Principles" has five competencies:

1. Enumerate general design requirements.
2. Review the general conditions of the construction contract.
3. Estimate labor, materials and other quantities.
4. Design project organization, cost-control procedures and project documentation.
5. Interpret value engineering analysis models.

Contract documents and Civil Code Articles 1723 and 1724 are covered in Section 1.3, and quantity and cost estimating in Section 6.6. This section covers the rest.

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General Design Requirements

Design principles across all codes:

• Strength: factored loads must not exceed design strength.
• Serviceability: limit deflection, cracking and vibration.
• Durability: provide cover, coatings and drainage.
• Constructability: standardize sizes, repeat forms and avoid congestion.
• Economy: minimize life-cycle cost.

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General Conditions of the Construction Contract

The general conditions set the rules of the relationship between owner and contractor. Typical clauses:

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Estimating Labor, Materials and Other Quantities

1. Materials are taken off from the drawings in standard units (Section 6.6). Allowances are added for waste, laps and breakage.
2. Labor is estimated from productivity rates, the units of work per crew-day.

$\text{Crew-days} = \frac{\text{Quantity}}{\text{Crew output per day}}, \qquad \text{Labor cost} = \text{Crew-days} \times \text{Crew daily cost}$

1. Equipment cost is estimated from rental or ownership-and-operating rates multiplied by the required hours.

Example. A wall needs $240\text{ m}^2$ of plastering. A crew of 1 mason and 1 helper plasters $12\text{ m}^2$ per day, and the crew costs PHP 1,600 per day. The work takes $240/12 = 20$ crew-days, and labor costs $20 \times 1{,}600 = \text{PHP }32{,}000$.

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Project Organization

Typical roles on a building project:

• the owner;
• the design professionals (architect and engineers of record);
• the construction manager or project manager;
• the contractor's project engineer and site engineer;
• foremen and leadmen who direct crews;
• the materials engineer or quality control staff;
• the safety officer.

Government projects add a resident engineer who represents the agency.

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Cost Control by Earned Value

Earned value management integrates scope, schedule and cost:

Example. The budget at completion (BAC) is PHP 20 million. At month 6, PV = PHP 9.0 million, EV = PHP 8.0 million and AC = PHP 10.0 million.

• CPI = 0.80 and SPI = 0.89.
• CV = −PHP 2.0 million and SV = −PHP 1.0 million.
• EAC = 20/0.80 = PHP 25 million.

The project is over budget and behind schedule. Management should look for cost overruns in specific work items and recover the schedule.

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Project Documentation

• Daily site logs: weather, manpower, equipment, work done, incidents.
• Requests for information (RFIs) and responses.
• Shop drawings and submittals with approval status.
• Material test results and inspection reports.
• Variation orders and extension-of-time requests.
• Progress reports and photographs.
• Minutes of meetings.
• As-built drawings and the punch list at completion.

Good documentation is the evidence used to settle claims and disputes.

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Value Engineering

Value engineering (VE) is an organized study of functions to achieve the required performance at the lowest life-cycle cost, without reducing quality or safety:

$\text{Value} = \frac{\text{Function (worth)}}{\text{Cost}}$

The VE job plan:

1. Information. Collect costs, requirements and constraints.
2. Function analysis. Describe each element as a verb plus a noun, for example "support load" or "exclude water." Then identify high-cost, low-worth functions.
3. Creative. Brainstorm alternatives.
4. Evaluation. Screen and rank alternatives by weighted criteria and life-cycle cost.
5. Development. Detail the best proposals with costs and risks.
6. Presentation and implementation. Recommend changes to the owner.

Example. Replacing a cast-in-place retaining wall with a mechanically stabilized earth wall may provide the same function, retaining fill, at lower cost and shorter duration. VE compares the two on life-cycle cost, which includes maintenance and durability, not just first cost.