For pile clusters without moment, the pile load Pu for strength design of the footing is obtained by dividing the factored column load by the number of piles n. The factored load equals 1.4D  1.7L, where D is the dead load, including the weight of the pile cap, and L is the live load. For pile clusters with moment, the factored load on the rth pile is 1 eC P
(1.4D  1.7L)  r (9.95) ur n n 2  Cr 1 where e
eccentricity of resultant load with respect to neutral axis of pile group, in. Cr
distance between neutral axis of pile group and center of nth pile, in. n
number of piles in cluster A drilled-pier foundation is used to transmit loads to soil at lower levels through end bearing and, in some situations, side friction. (See also Art. 9.74.) It can be FIGURE 9.49 Bell-bottom drilled pier with dowels for a column. constructed in firm, dry earth or clay soil by machine excavating an unlined hole with a rotating auger or bucket with cutting vanes and filling the hole with plain or reinforced concrete. Under favorable conditions, pier shafts 12 ft in diameter and larger can be constructed economically to depths of 100 ft and more. Buckets with sliding arms can be used to form bells at the bottom of the shaft with a diameter as great as 3 times that of the shaft (Fig. 9.49). Some building codes limit the ratio of shaft height to shaft diameter to a maximum of 30. They also may require the bottom of the bell to have a constant diameter for the bottom foot of height, as shown in Fig. 9.49. The compressive stress permitted on plain-concrete drilled piers with lateral support from surrounding earth varies with different codes. The BOCA National Building Code/1999, limits the computed bearing stress based on service loads to 0.33c
, where
c is the specified concrete compressive strength. Reinforced-concrete drilled piers can be designed as flexural members with axial load, as indicated in Art. 9.82. Allowable unfactored loads on drilled piers with various shaft and bell diameters, supported by end bearing on soils of various allowable bearing pressures, are given in Table 9.23. For maximum-size bells (bell diameter 3 times shaft diameter) and a maximum concrete stress c1
for unfactored loads, the required concrete 0.33
c strength, psi, is 19% of the allowable soil pressure, psf. Column-design procedures are based on a comprehensive investigation reported by American Concrete Institute Committee 105 (Reinforced Concrete Column Investigation, ACI Journal, February 1933) and followed by many supplemental tests. The results indicated that basically the total capacity for axial load can be predicted, TABLE 9.23 Allowable Service (Unfactored) Loads on Drilled Piers, kips* Shaft dia, ft Shaft area, in2
3000
c

The most important contractual liability that may be assumed by the contractor is the so-called hold-harmless clause. A common type of hold-harmless clause as written by a general contractor to a subcontractor is illustrated in the subcontract rider in Fig. 17.7, Paragraph 32a. A similar clause written by the owner for inclusion in the general contract would be slightly modified and would substitute in appropriate places the word Contractor for subcontractor and the word Owner for Contractor. Hold-harmless clauses can be automatically included in a general contractors commercial general-liability policy. However, the general contractor should include the previously mentioned subcontractor hold-harmless clause in each subcontract. Subcontractors will probably be required by their insurance companies to pay an additional premium for this coverage. The commercial general-liability policy includes complete and automatic products- liability insurance, including completed-operations protection. The one exception to this complete coverage is that the policy does not include liability for damage to the work or to the goods themselves, such as the obligation of the contractor to repair or replace if there are defects. While the policy provides coverage, it is in fact an optional protection, which may be deleted. However, every contractor should take advantage of this coverage. Most building contractors use elevators or hoists during construction. The policy automatically covers elevators, hoists, and other such hazards. Escalators may be covered for an additional premium. The breadth of public-liability protection available, the numerous hazards to which a contractor may be exposed, both known and unknown, and the necessity for having complete coverage at all times indicate the need for the advice of trained insurance representatives. 17.15.7 Workers Compensation Insurance Every state requires an employer to secure a policy of workers compensation to provide for an injured employee the benefits of the workers compensation law of that state. An insurance company that has had extensive experience in the workers compensation field is best suited to meet the requirements of most contractors. It is in the employers, as well as the employees, best interests to see that the company entrusted to provide workers compensation insurance is equipped to provide loss-prevention service and prompt first aid and to settle compensation claims fairly

Acoustical Audiovisual Communications Exterior wall maintenance Fire and life safety Food service Geotechnical engineering and subsurface exploration Graphics Space-usage operations Independent research and testing Landscaping Marketing and leasing Materials handling Parking Preconstruction survey Schedule Security Site surveyor Special foundation systems Special structures Specialty lighting Telecommunications Traffic Vertical transportation Water features Wind tunnel testing Although verbal contracts can be considered legal, a formal written document is the preferred way to contract for professional services to be provided by an archi- tect. Purchase orders are not an acceptable means, since they are not applicable to a service arrangement but rather only provide a financial accounting system for purchasing a product, which is normally required internally by a client. A purchase order should not be used as a client-A /E agreement. Most professionals use the AIA Standard Form of Agreement for Architect and Owner (client). Some larger firms, however, have their own form of agreement which augments or further defines that of the AIA. The basic elements of the agreement establish the definition and identification of project phases and define the specific scope and compensation for the architects basic services. Flexibility is built into this agreement to accommodate supplementary services that may be considered. In addition, the agreement should define the understandings of the two parties as well as of any third parties that may be involved in the process and stipulate how the third parties are to be managed and compensated. Furthermore, the client-A /E agreement should define items considered as direct costs that may be reimbursed under the agreement. Other items also to be addressed include project terminology, project terms and definitions, and the architects status as it relates to the profession such that the standard of care is clearly understood. The definition of additional services, changes, and compensation for such services, as well as the method and timing of payment, reimbursable expenses, taxes, the responsibility for client-furnished information, project budgets, ownership of documents, confidentiality provisions, the use of project databases, insurance requirements, termination provisions by either party, and dispute resolution may also be addressed. A/E agreements may also define the documents to be delivered at the conclusion of each development phase and, in certain cases, the time estimated for completion of each phase of service. Compensation for Professional Services. A major concern of an architect is to arrive at an accurate assessment of the scope of services to be performed. The nature of the project, the degree of professional involvement, and the skills required should be considered in arriving at an equitable fee arrangement. Types of fees that