Building's - Distinct Design Approaches

The more important difference between wind and earthquake resistance lies in their basic design approaches. For wind load resistance, the structure is designed so that under the action of maximum wind loads, it remains elastic—that is, the structure is designed to suffer no permanent deformation under the worst expected storm.

The design approach is different for earthquake load resistance. The loads on a building produced by the worst expected earthquake for the location are so large that if the building were designed to remain elastic after the earthquake, it would be prohibitive in cost. Therefore, the earth-quake loads for which a building is designed may be smaller than the maximum earthquake loads expected on it.

The underlying design philosophy is that the building should remain elastic when resisting minor earthquakes. In the event of an intense earth-quake, part of the earthquake’s energy may be dissipated in permanently deforming the building, but the building must otherwise remain intact to provide complete safety to its occupants.

Permanent deformations in a structure are possible only if the structure has the ability to sustain such deformations. Materials that can sustain permanent deformation prior to failure are called   ductile  materials. Ductility is an essential property for buildings located in seismic zones but is not a requirement for resisting wind loads.

A building must not deform permanently even in the most severe windstorm. Additionally, it must be rigid enough to reduce the deflections caused by strong winds. The swaying of the upper floor of tall buildings under wind loads must be controlled to remain within acceptable limits of human tolerance.

The reverse is true for earthquake loads. Buildings must be able to deform, even permanently, to absorb the energy delivered to them by the earthquake. If brittle materials are used, they will fail under earthquake forces. Several reinforced concrete frame buildings with (brittle) unreinforced masonry infill walls between frames have collapsed or suffered serious damage under earthquake forces,  Figure 3.26   . Such buildings would generally be unharmed by violent storms.

Distinct Design Approaches
FIGURE 3.26 A typical pattern of damage to unreinforced masonry infill walls in buildings with a reinforced concrete frame structure. If the infill walls shown in this illustration had been reinforced horizontally and vertically, they would have suffered minor (or no) damage depending on the earthquake’s intensity.

Building Construction and Economy

Careful planning in scheduling the construction operations for a building and in providing the forms can assure the maximum economy in formwork and also the highest efficiency by labor, both of  which will reduce the cost of formwork.

Consider the six-story building in Figure 2-1, to be constructed  with concrete columns, girders, beams, and slabs. The floor area is  large enough to justify dividing the floor into two equal or approx-imately equal areas for forms and concreting. A construction joint through the building is specified or will be permitted. If the structure is symmetrical about the construction joint, the builder will be fortunate. If the building is not symmetrical about the construction joint, some modifications will have to be made in the form procedures presented hereafter.

Each floor will be divided into equal units for construction purposes. Thus, there will be 12 units in the building. One unit will be completely constructed each week, weather permitting, which will include making and erecting the forms; placing the reinforcing steel, electrical conduit, plumbing items, etc., and pouring the concrete. The carpenters should complete the formwork for unit 1 by the end of the third day, after which time some of them will begin the form-work for unit 2 while others install braces on the shores and other braces, if they are required, and check; if necessary, the carpenters will adjust the elevations of girder, beam, and deck forms. One or two carpenters should remain on unit 1 while the concrete is being placed. This will consume one week.
FIGURE 2-1  Construction schedule for concrete frame of building.
FIGURE 2-1  Construction schedule for concrete frame of building.

During the second week, and each week thereafter, a unit will be completed. Delays owing to weather may alter the timing but not the schedule or sequence of operations. Figure 2-1 shows a simplified section through this building with the units and elapsed time indicated but with no provision for lost time owing to weather.

Forms for columns and beam and girder sides must be left in place for at least 48 hours, whereas forms for the beam and girder bottoms, floor slab, and vertical shores must be left in place for at
least 18 days. However, concrete test cylinders may be broken to determine the possibility of a shorter removal time of shores. Form-work will be transferred from one unit to another as quickly as time requirements and similarity of structural members will permit.

Table 2-2 will assist in determining the number of reuses of form units and total form materials required to construct the building illustrated in Figure 2-1. Although the extent to which given form sections can be reused will vary for different buildings, the method of analyzing reusage presented in this table can be applied to any building and to many concrete structures.

If the schedule shown in Table 2-2 will apply, it will be necessary to provide the following numbers of sets of forms: for columns and beam and girder sides, two sets and for beam bottoms, slab decking,
and shores, three sets.
TABLE 2-2  Schedule of Use and Reuse of Formwork for a Building (Continued  )
If structural sections such as columns, girders, beams, and floor panels in odd-numbered units 1 through 11 are similar, and those in the even-numbered units 2 through 12 are similar, but those in units 1 through 11 are not similar to those in units 2 through 12, it will be necessary to move form sections to higher floors above given units. For example, forms for unit 1 cannot be used in unit 2, or those from unit 3 in unit 4, and so on. Under this condition, it will be necessary to provide one set of columns and beam and girder sides for unit 1 and another set for unit 2, which will be sufficient for the entire building.

WIND VERSUS EARTHQUAKE RESISTANCE OF BUILDINGS

As discussed in Section 3.4, many of the structural strategies used for wind load resistance and earthquake resistance are essentially similar. Buildings are, therefore, generally designed to resist either earthquake loads or wind loads, whichever causes the worst effect (greater stresses). This is based on the assumption that there is a negligible probability of maximum wind speeds occurring at the same time as an intense earthquake. In regions of low seismic activity, wind loads govern the design of the lateral resistance of buildings; in regions of intense seismic activity, the reverse is the case.

The design of lightweight envelope components, such as glass curtain walls and roof membranes, is governed by wind loads even in highly seismic regions. (Remember that earthquake loads are influenced by the weight of the component.)  Despite the similarities between the provisions for wind load and earthquake load resistance, there are several differences in the details. An important difference is that as an earth-quake shakes the ground on which the building rests, it affects all components of the building—exterior as well as interior components. Damage to the building’s contents and injury to occupants may occur by falling interior contents,  Figure 3.24   . Thus, all compo-nents, equipment, and fixtures in a building located in a seismically active zone must be adequately anchored to remain intact during an earthquake.

FIGURE 3.24 Effect of earthquake shaking (1989 Loma Prieta earth-quake) on the contents of a building’s interior. Note that the building envelope is intact.
FIGURE 3.24 Effect of earthquake shaking (1989 Loma Prieta earth-quake) on the contents of a building’s interior. Note that the building envelope is intact.
Wind, on the other hand, acts on the building envelope. It is through the envelope that wind loads are transmitted to the building structure. If the envelope remains intact, the building will generally retain its overall structural integrity in a storm. Thus, the wind damage in a building usually begins with the damage to envelope components, such as the roof, exterior walls, exterior doors, windows, and other cladding elements. Once the building changes from fully enclosed to partially enclosed (see  Figure 3.15), the wind loads on the building increase due to the ballooning effect, which may result in additional damage or collapse of the structure, damage to interior contents, and injuries to occupants, Figure 3.25.

FIGURE 3.25 Damage to the glass curtain wall of the 37-story Bank One Building, Fort Worth, Texas, by a forceful tornado on March 28, 2000. As soon as the glass in the curtain wall shattered, substantial damage to the building’s interior (ceiling, drywall, electrical fixtures, etc.)
FIGURE 3.25 Damage to the glass curtain wall of the 37-story Bank One Building, Fort Worth, Texas, by a forceful tornado on March 28, 2000. As soon as the glass in the curtain wall shattered, substantial damage to the building’s interior (ceiling, drywall, electrical fixtures, etc.)

FIGURE 3.15 Ballooning of a building with a relatively large opening in one wall. Such a building is referred to as a partially enclosed building. A building that is not partially enclosed is called an enclosed building. Most buildings belong to the enclosed building category.
FIGURE 3.15 Ballooning of a building with a relatively large opening in one wall. Such a building is referred to as a partially enclosed building. A building that is not partially enclosed is called an enclosed building. Most buildings belong to the enclosed building category. 

BUILDING’S MASS AND DUCTILITY OF THE STRUCTURAL FRAME

From Newton’s second law of motion, the other factor that affects the magnitude of the earthquake load is the weight of the building. Lighter buildings attract a smaller earthquake load than buildings constructed of heavy materials. Thus, concrete frame and masonry structures attract a greater earthquake load than wood frame or steel frame structures. Residential structures with wood siding or stucco finishes attract a smaller earthquake load than those with brick or stone veneer.

Indeed, because of its light weight, the earthquake load on a tent is negligible even in a severe earthquake, Figure 3.22. A tent structure has the additional advantage of its built-in resistance toabsorb structural deformations (ductility)—an important structural property for earthquake regions.
Buildings constructed of heavy materials with little or no capacity to absorb deformations are among the most hazardous buildings in a seismically active zone. Such buildings include those whose structural system consists of unreinforced masonry structures (i.e., bricks, stone or concrete block walls with no vertical rein-forcement), Figure 3.23.

RAIN LOAD

Although roofs are designed to have adequate drainage so that no accumulation of water occurs, loads resulting from accidental accumulation of melted snow or rainwater must be considered as a possibility. Drains may be blocked by windblown debris or hail aggregating on the roof or the formation office dams near the drains.

Long-span, relatively flat roofs are particularly vulnerable to rainwater accumulation because, being flexible, they deflect under the weight of water. This deflection leads to yet more accumulated water, causing additional deflection, which increases accumulation. If adequate stiffness is not provided in the roof, the progressive increase of deflection can cause excessive load on the roof. Water accumulation has been the cause of complete collapse of several long-span roofs.

Generally, roofs with slope greater than 1/4 in. to 1 ft (1:48 or, say, 1:50 slope) are not subjected to accumulated rainwater unless roof drains are blocked. Building codes mandate 1/4 in. to 1 ft as the minimum slope required for roofs, which, apart from providing positive drainage, also helps to increase the life and improve the performance of roof (waterproofing) membranes.

Building codes also require that in addition to primary drains, roofs must be provided with secondary (overflow) drains. The secondary drains must be at least 2 in. above the primary drains so that if the primary drainage system gets blocked, the secondary system will be able to drain the water off the roof,   Figure 3.5.

Water accumulation generally occurs on roofs that are provided with a parapet. In the absence of a parapet, water accumulation will generally not occur. Therefore, secondary drains are not required on unparapeted roofs or on steep roofs.

ROOF LIVE LOAD

The live load on a roof takes into account the weight of repair personnel and temporary storage of construction or repair materials and equipment on the roof. Roof live load is generally given as 20 psf acting on the horizontal projected area of the roof, Figure 3.4.


This applies to a roof that will not be used in the future as a floor. If the building is expected to be extended vertically in the future, the roof live load is the floor live load for the anticipated future occupancy. Additionally, if the roof is to be landscaped, the load due to the growth medium and landscaping elements must be considered as dead load on the roof.

LIVE LOADS IN A BUILDING

While the dead load is a permanent load on the structure,   live load  is defined as the load whose magnitude and placement change with time. Such loads are due to the weights of people (animals, if the building houses animals), furniture, movable equipment, and stored materials. As shown in  Figure 3.1   , live loads are further divided into

• Floor live load
• Roof live load


Floor live load depends on the occupancy and the use of the building. Therefore, it is also called the   occupancy load,  and it is different for different occupancies. For instance, the floor live load for a library stack room is higher than the floor live load for a library reading room, which in turn is higher than the floor live load for an apartment building.

Floor live loads are determined by aggregating the loads of all people, furniture, and movable equipment that may result from the particular occupancy. Safety considerations require that the worst expected situation be considered so that the structure is designed for the maximum possible live load that may be placed on it.

Based on a large number of surveys, floor live loads for various commonly encountered occupancies, such as individual dwellings, hotels, apartment buildings, libraries, office buildings, and industrial structures, have been determined and are contained in building code tables. Table 3.1 gives floor live loads for a few representative occupancies. For instance, the floor live load for a library stack room is 150 psf, for a library reading room is 60 psf, and for an apartment building is 40 psf. Note that these are the minimum floor live loads for which the building must be designed. Even if the actual live load on a floor is smaller, the building must be designed for the minimum live load specified by the building code.

The floor live load values in Table 3.1 are conservative. In most situations, the actual loads are smaller than those given. However, the architect or the engineer must recognize unusual situations that may lead to a greater actual load than the one specified in the code. In such situations, the higher anticipated load should be used.  

Additionally, if the live load for an occupancy not included in building code tables is to be obtained, the architect or the structural engineer must determine it from first principles, taking into account all the loads that may be expected on the structure. Most building codes require that such live load values be approved by the building official.
MINIMUM FLOOR LIVE LOADS FOR  SELECTED OCCUPANCIES

DEAD LOADS IN A BUILDING

Dead loads are always present in a building; that is, they do not vary with time. They include the weights of the materials and components that comprise the structure. The dead load of a component is computed by multiplying its volume by the density of the material. Because both the densities and the dimensions of the components are known with reasonable accuracy, dead loads in a building can be estimated with greater certainty than other load types. Densities of some of the commonly used materials are given in  Table 2.


The dead load for which a building component is designed includes the self-load of the component plus the dead loads of all other components that it supports. For example, the dead load on a column includes the weight of the column itself plus all the dead load imposed on it. In Figure 3.3, the dead load on a column is the weight of the column plus the dead load from the beams and slab resting on it. Similarly, the dead load on a beam is the weight of the beam itself plus the dead load from the slab that it supports. The dead  load on the slab is only the self-weight of the slab. However, if the slab supports a floor finish, ceiling, light fixtures, or plumbing and electrical pipes, their weights must be included in the dead load acting on the slab.

CONSTRUCTION CONTRACT ADMINISTRATION

The general contractor will normally have an inspection process to ensure that the work of all subcontractors is progressing as indicated in the contract documents and that the work meets the standards of quality and workmanship. On smaller projects, this may be done by the project superintendent  . On large projects, a team of quality-assurance inspectors generally assists the contractor’s project superintendent. These inspectors are individuals who, by training and experience, are specialized in their own areas of construction—for example, concrete, steel, or masonry.

CONSTRUCTION CONTRACT ADMINISTRATION

Additional quality control is required by the contract through the use of independent testing laboratories. For instance, structural concrete to be used on the site must be verified for strength and other properties by independent concrete testing laboratories.

Leaving quality control of materials and performance entirely in the hands of the contractor is considered inappropriate. It can render the owner vulnerable to omissions and errors in the work, and it places an additional legal burden on the contractor. Therefore, the owner usually retains the services of the project architect to provide a third-party level of scrutiny to administer the construction contract. If not, the owner will retain another independent architect, engineer, or inspector to provide construction contract administration services. The contracting community favors this third-party oversight of its work.

The architect’s role during the construction phase has evolved over the years. There was a time when architects provided regular supervision of their projects during construction, but the liability exposure resulting from the supervisory role became so adverse for the archi-tects that they have been forced to relinquish this responsibility. Instead, the operative term for the architect’s role during construction is   field observation  of the work.

The observational role still allows the architects to verify that their drawings and specifications are transformed into reality just as they had conceived. It also provides a sufficient safeguard against the errors caused by the contractors’ misinterpretation of contract documents in the absence of the architects’ clarification and interpretation. The shift in the architect’s role to observer of construction also recognizes the important and entirely independent role that the contractor must play during construction. This rec-ognition provides full authority to the general contractor to proceed with the work in the manner that the contractor deems appropriate. This reinforces the earlier statements that:

•    The architect determines the   what  and   where . 
•    The contractor determines the   how  (means and methods) and   when  (sequence) of construction.

In other words, daily supervision or superintendence of construction is the function of the contractor—the most competent person to fulfill this role. The architect provides periodic observation and evaluation of the contractor’s work and notifies the owner if the work is not in compliance with the intent of the contract documents. This under-scores the  division between the responsibilities of the architect and the contractor during construction.

Note that by providing observation, the architect does not certify the contractor’s work. Nor does the observation relieve the contractor of its responsibilities under the contract. The contractor remains fully liable for any error that has not been discovered through the architect’s observation. However, the architect may be held liable for all or part of the work observed, should the architect fail to detect or provide timely notification of work not conforming with the contract documents. This omission is known as failure to detect.
 
Because many components can be covered up by other items over days or hours, the architect should visit the construction site at regular intervals, as appropriate to the progress of construction. For example, earthwork covers foundations and underground plumbing, and gypsum board covers ceiling and wall framing. Observing the work after the components are hidden defeats the purpose of observation.

On some projects, a resident project architect or engineer may be engaged by the architect, at an additional cost to the owner, to observe the work of the contractor. Under the conditions of the contract, the contractor is generally required to provide this person with an on-site office, water, electricity, a telephone, and other necessary facilities.

INSPECTION OF WORK 

There are only two times during the construction of a project that the architect makes an exception to being an observer of construction. At these times, the architect inspects the work. These inspections are meant to verify the general contractor’s claim that the work is (a) substantially complete and (b) has been completed and hence is ready for final payment. These inspections, explained in Section 1.10, are referred to as:

•     Substantial  completion   inspection
•    Final  completion  inspection

PAYMENT CERTIFICATIONS 

In addition to construction observation and inspection, there are several other duties the architect must discharge in administering the contract between the owner and the contractor. These are outlined in the box “Summary of Architect’s Functions as Construction Contract Administrator.” Certifying (validating) the contractor’s periodic requests for payment against the work done and the materials stored at the construction site is perhaps the most critical of these functions. An application for payment (typically made once a month unless stated differently in the contract) is followed by the architect’s evaluation of the work and necessary documentation to verify the contractor’s claim. Because the architect is not involved in day-to-day supervision, the issuance of the certificate of payment by the architect does not imply acceptance of the quality or quantity of the contractor’s work. However, the architect has to be judicious and impartial to both the owner and the contractor and perform within the bounds of the contract. 

CHANGE ORDERS 

There is hardly a construction project that does not require changes after construction has begun. The contract between the owner and the contractor recognizes this fact and includes provisions for the owner’s right to order a change and the contractor’s obligation to accept the   change order  in return for an equitable price adjustment. Here again, the architect performs a quasi-judicial role to arrive at a suitable agreement and price between the owner and the contractor.    

CONSTRUCTION PHASE

Once the general contractor has been selected and the contract awarded, the construction work begins, as described in the   contract documents  . The contract documents are virtually the same as the bidding documents, except that the contract documents are part of a signed legal contract between the owner and the contractor. They generally do not contain Division 00 of the MasterFormat.

In preparing the contract documents, the design team’s challenge is to efficiently produce the graphics and text that effectively communicate the design intent to the construction professionals and the related product suppliers and manufacturers so that they can do the following:

  •    Propose accurate and competitive bids
  •    Prepare detailed and descriptive submittals for approval
  •    Construct the building with a minimum number of questions, revisions, and changes
   
SHOP DRAWINGS

The construction drawings and the specifications should provide a fairly detailed delineation of the building. However, they do not describe it to the extent that fabricators can produce building components directly from them. Therefore, the fabricators generate their own drawings, referred to as   shop drawings , to provide the higher level of detail necessary to fabricate and assemble the components.

Shop drawings are not generic, consisting of manufacturers’ or suppliers’ catalogs, but  are specially prepared for the project by the manufacturer, fabricator, erector, or subcontractors. For example, an aluminum window manufacturer must produce shop drawings to show that the required windows conform with the construction drawings and the specifications. Similarly, precast concrete panels, stone cladding, structural steel frame, marble or  granite flooring, air-conditioning ducts, and other components require shop drawings  before they are fabricated and installed.

Before commencing fabrication, the fabricator submits the shop drawings to the general  contractor. The general contractor reviews them, marks them “approved,” if appropriate, and then submits them to the architect for review and approval. Subcontractors or   manufacturers cannot submit shop drawings directly to the architect.

The review of all shop drawings is coordinated through the architect, even though they may actually be reviewed in detail by the appropriate consultant. Thus, the shop drawings pertaining to  structural components are sent to the architect and then to the structural consultant for review and approval. The fabricator generally begins fabrication only after receiving the architect’s review of the shop drawings.

The review of shop drawings by the architect is limited to checking that the work indicated therein conforms with the overall design intent shown in the contract documents. Approval of shop drawings that are later discovered to deviate from the  contract documents does not absolve the general contractor of the responsibility to comply with the contract documents for quality of materials, workmanship, or the dimensions of the fabricated components,  Figure  1.9.


MOCK-UP SAMPLES

In addition to shop drawings, full-size mock-up samples of one or more critical elements of the building may be required in some projects. This is done to establish the quality of materials and workmanship by which the completed work will be judged. For example, it is not unusual for the architect to ask for a mock-up of a  typical area of the curtain wall of a high-rise building before the fabrication of the actual curtain wall is undertaken. Mock-up samples go through the same approval process as the shop drawings.

OTHER SUBMITTALS

In addition to shop drawings and any mock-up samples, some other submittals required from the contractor for the architect’s review are:

•   Product  material  samples 
•   Product  data 
•   Certifications
•   Calculations

DBB METHOD—INVITATIONAL BIDDING

Invitational bidding, also called   closed bidding , is another variation of the DBB method that is generally used for quasi-public and some private projects. In this method, the owner preselects general contractors who have demonstrated, based on their experience, resources, and financial standing, their qualifications to perform the work. The selected contractors are then invited to bid for the project, and the contractor with the lowest bid is then awarded the contract. The architect (as the owner’s representative) may be involved in the prescreening process.

DBB METHOD—COMPETITIVE SEALED PROPOSAL

This method is very similar to competitive sealed bidding and is commonly used for publicly funded projects. The difference between competitive sealed bidding and competitive sealed proposal methods is that the owner’s selection of the general contractor is not based on price alone but also on such other criteria as the contractor’s past experience, safety record, proposed personnel, project schedule, and so on. To ensure fairness, the advertisement and bidding documents must provide the details of the selection criteria, with relative weightings assigned to each criterion.  

DBB METHOD—COMPETITIVE SEALED BIDDING

On several publicly funded projects, the award of a construction contract to the general contractor is based on   competitive sealed bidding , also called   open bidding . This refers to the process by which qualified contractors are invited to bid on the project. The invitation is generally issued through advertisements in newspapers, trade publications, and other public media.

The advertisement for bids includes a description of the project, its location, where to obtain the bidding documents, the price of the bidding documents, the bid opening date and location, and other important information. The purpose of the advertisement is to notify and thereby attract a sufficient number of contractors to compete for the construction contract.

The general contractor’s bid for the project is based on the information provided in the bidding documents . The bidding documents are essentially the construction document set with such additional items as the instructions to bidders, requirements with respect to the  financial and technical status of bidders (see the information on surety bonds in the box  “Expand Your Knowledge”), and the contract agreement form that the successful bidder  will sign when the contract is awarded. Because these additional items are text items, they  are bound together as a project manual, Figure 1.8.

  FIGURE 1.8  The project manual in the bidding document set includes specifications and
  Division 00. After the general contractor has been selected, the project manual (in the contract
document set) generally excludes Division 00.




In the competitive sealed bidding method, the bidding documents are generally given only to contractors who are capable, by virtue of their experience, resources, and financial standing, to bid for the project. Therefore, the architect (as the owner’s representative) may prescreen the bidders with respect to their reputation and ability to undertake the project.


An exception to prescreening for the release of bidding documents involves projects funded by the federal, state, or local government, for which almost anyone can access the bidding documents. However, even in this kind of project, the number of contractors who can actually submit the bids is practically limited. This limitation is generally the result of the financial security required from the bidders, known as a   bid bond . The bidder must obtain a bid bond from a surety company in the amount specified in the bidding documents. This bond is issued based on the contractor’s experience, ability to perform the work, and financial resources required to fulfill the contractual obligations.

Whether or not the release of the bidding documents is restricted, the procedure stated earlier ensures that all the bidders are similarly qualified with respect to financial ability, experience, and technical expertise. Because all bidders receive the same information and are of the same standing, the competition is fair; therefore, the contract is generally awarded to the lowest qualified bidder.    

DESIGN-BID-BUILD PROJECT DELIVERY METHOD

In the design-bid-build method, the general contractor is selected through competition. The owner obtains multiple bids for the project from which the general contractor, who provides the “best value for money,” is selected. Within this overall approach, several  versions are available to suit the requirements of the project and the particular needs of  the owner. Collectively, these delivery versions are referred to as the   design bid-build  (DBB) method because in this version, the design, bid, and construction phases of a  project are sequential, and one phase does not begin until the previous phase has been  completed,  Figure 1.7 . Following are three commonly used versions of the DBB method  of delivery:

  •    DBB method—competitive sealed bidding (open bidding)
  •    DBB method—competitive sealed proposal
  •    DBB  method— invitational  bidding   (closed  bidding)  

  FIGURE 1.7  Sequence of operations in the design-bid-build (DBB) method of project delivery. Note that the owner’s approval is required before proceeding from one phase or stage to the next.

GENERAL CONTRACTOR AND PROJECT DELIVERY METHODS

Selecting the general contractor is a crucial part of a project. A number of selection methods exist. The method used in selecting the general contractor, its timing, and the contractor’s obligations under the contract distinguishes one project delivery method from the other. Some of the most commonly used delivery methods are:

•    Design-bid-build  method
•    Design-negotiate-build  method
•    Construction manager as agent method
•     Construction  manager  at  risk   method
•    Design-build  method
•    Integrated  project  delivery  method

The design-bid-build method is the oldest and most familiar method of project delivery. This method is covered first. Because the essential features of construction and postconstruction phases are almost identical in all delivery methods, a discussion of what is included in these two phases is presented next. Subsequently, other methods are discussed in terms of how they differ from the design-bid-build method. The table “Project Delivery Methods at a Glance” provides a synopsis of these methods.

GENERAL CONTRACTOR AND PROJECT DELIVERY METHODS

CONSTRUCTION-RELATED INFORMATION

The preconstruction phase generally begins after the construction drawings and specifications have been completed and culminates in the selection of the construction team. The construction of even a small building involves so many specialized skills and trades that the work cannot normally be undertaken by a single construction firm. Instead, the work is generally done by a team consisting of the   general contractor  and a number of specialty subcontractors .

Thus, a project may have roofing; window and curtain wall; plumbing; and heating, ventilation, and air-conditioning (HVAC) subcontractors, among others, in addition to the general contractor. The general contractor’s own work may be limited to certain components of the building (such as the structural components—load-bearing walls, reinforced concrete beams and columns, roof and floor slabs, etc.), with all the remaining work subcontracted.

In contemporary projects, however, the trend is toward the general contractors not performing any actual construction work but subcontracting the work entirely to various sub-contractors. Because the subcontractors are contracted by the general contractor, only the general contractor is responsible and liable to the owner.

In some cases, a subcontractor will, in turn, subcontract a portion of his or her work  to another subcontractor, referred to as a   second-tier subcontractor, Figure 1.6. In  that  case, the general contractor deals only with the subcontractor, not the second-tier subcontractor.

Whether the general contractor performs part of the construction work or subcontracts  the entire work, the key function of the general contractor is the overall management of  construction. This includes coordinating the work of all subcontractors, ensuring that the  work done by them is completed in accordance with the contract documents, and ensuring  the safety of all workers on the site. A general contractor with a good record of site safety  not only demonstrates respect for the workers but also improves the profit margin by lowering the cost of construction insurance.

  FIGURE 1.6  Members of the construction team and their interrelationships with each other and
the owner. A solid line in this illustration indicates a contractual relationship between parties. A
dashed line indicates a communication link, not a contract. The relationships shown here are not
absolute and may change with the nature of the project.

RECOLLECTING THE MASTERFORMAT DIVISION SEQUENCE

Architectural design typically involves Divisions 2 to 14 of the Facilities Construction Subgroup. Although the basis for sequencing the Divisions in this subgroup is far more complicated, the first few divisions (those that are used in virtually all buildings) may be deduced by visualizing the sequence of postearthwork operations required in constructing the simple building shown in  Figure 1.5. The building consists of load-bearing masonry walls, steel roof joists, and wood roof deck.

  FIGURE 1.5  A simple load-bearing masonry wall building with steel roof trusses and wood roof
deck used as an aid to recalling the sequence of the first few (architecturally important) divisions of
the MasterFormat.




The first operation is the foundations for the walls. Because foundations are typically made of concrete,   Concrete  is Division 03. After the foundations have been completed, masonry work for the walls can begin. Thus,   Masonry  is Division 04. After the walls are completed, steel roof joists can be placed. Thus, Division 05 is   Metals . The installation of the wood roof deck follows that of the steel joists. Hence,   Wood, Plastics, and Composites is Division 06.


After the roof deck is erected, it must be insulated and protected against weather. Therefore,   Thermal and Moisture Protection  is Division 07. Roofing and waterproofing (of basements) are part of this division, as are wall insulation and joint sealants. The next step is to protect the rest of the envelope; hence, Division 08 is   Openings . All doors and windows are part of this division, regardless of whether they are made of steel, aluminum, or wood.

With the envelope protected, finish operations, such as those involving the interior dry- wall, flooring, and ceiling, can begin. Thus, Division 09 is   Finishes . Division 10 is Specialties , which consists of several items that cannot be included in the previous divisions, such as toilet partitions, lockers, storage shelving, and movable partitions.

Obviously, the building must now receive all the necessary office, kitchen, laboratory, or other equipment. Thus, Division 11 is   Equipment . Division 12 is   Furnishings ,  followed  by Special Construction  (Division 13) and   Conveying Equipment   (Division  14).   

Before any construction operation can begin, there must be references to items that apply to all divisions, such as payment procedures, product-substitution procedures, contract-modification procedures, contractor’s temporary facilities, and regulatory requirements imposed by the city or any other authority having jurisdiction. This is Division 01, General Requirements  . Division 00 (  Procurement and Contracting  Requirements  ) refers to the requirements for the procurement of bids from prospective contractors.

RECOLLECTING THE MASTERFORMAT DIVISION SEQUENCE

Architectural design typically involves Divisions 2 to 14 of the Facilities Construction Subgroup. Although the basis for sequencing the Divisions in this subgroup is far more complicated, the first few divisions (those that are used in virtually all buildings) may be deduced by visualizing the sequence of postearthwork operations required in constructing the simple building shown in  Figure 1.5   . The building consists of load-bearing masonry walls, steel roof joists, and wood roof deck.

  FIGURE 1.5 A simple load-bearing masonry wall building with steel roof trusses and wood roof
deck used as an aid to recalling the sequence of the first few (architecturally important) divisions of
the MasterFormat.

The first operation is the foundations for the walls. Because foundations are typically  made of concrete,   Concrete  is Division 03. After the foundations have been completed, masonry work for the walls can begin. Thus,   Masonry  is Division 04. After the walls are completed, steel roof joists can be placed. Thus, Division 05 is   Metals . The installation of the wood roof deck follows that of the steel joists. Hence,   Wood, Plastics, and Composites is Division 06.

After the roof deck is erected, it must be insulated and protected against weather. Therefore,   Thermal and Moisture Protection  is Division 07. Roofing and waterproofing (of basements) are part of this division, as are wall insulation and joint sealants. The next step is to protect the rest of the envelope; hence, Division 08 is   Openings . All doors and windows are part of this division, regardless of whether they are made of steel, aluminum, or wood.

With the envelope protected, finish operations, such as those involving the interior dry-wall, flooring, and ceiling, can begin. Thus, Division 09 is   Finishes . Division 10 is   Special-
ties , which consists of several items that cannot be included in the previous divisions, such
as toilet partitions, lockers, storage shelving, and movable partitions.

Obviously, the building must now receive all the necessary office, kitchen, laboratory, or other equipment. Thus, Division 11 is   Equipment . Division 12 is   Furnishings ,  followed  by  Special Construction  (Division 13) and   Conveying Equipment   (Division  14).   

Before any construction operation can begin, there must be references to items that  apply to all divisions, such as payment procedures, product-substitution procedures, contract-modification procedures, contractor’s temporary facilities, and regulatory requirements imposed by the city or any other authority having jurisdiction. This is Division 01, General Requirements  . Division 00 (  Procurement and Contracting  Requirements  ) refers to the requirements for the procurement of bids from prospective contractors.

THE CONSTRUCTION DOCUMENT SET

Just as the construction drawings are prepared separately by the architect and each consultant for their respective portions of the work, so are the specifications. The specifications from various design team members are assembled by the architect in a single document called the   project manual . Because the specifications consist of printed (typed) pages (not graphic images), a project manual is a bound document—like a book.

The major component of a project manual is the specifications. However, the project manual also contains other items, as explained later in this chapter.

The set of construction drawings (from various design team members) and the project manual together constitute what is known as the   construction document set, Figure 1.3. The construction document set is the document that the owner and architect use to invite bids from prospective contractors.

FIGURE 1.3 A construction document set consists of a set of architectural and consultants’ construction drawings plus the project manual. The project manual is bound in a book format. 

CONSTRUCTION SPECIFICATIONS

Buildings cannot be constructed from drawings alone, because there is a great deal of information that cannot be included in the drawings. For instance, the drawings will give the locations of columns, their dimensions, and the material used (such as reinforced concrete), but the quality of materials, their properties (the strength of concrete, for example), and the test methods required to confirm compliance cannot be furnished on the drawings. This information is included in the document called   specifications. 

Specifications are written technical descriptions of the design intent, whereas the drawings provide the graphic description. The two components of the construction documents—the specifications and the construction drawings—complement each other and generally deal with different aspects of the project. Because they are complementary, they  are supposed to be used in conjunction with each other. There is no order of precedence between the construction drawings and the specifications. Thus, if an item is described in  only one place—either the specification or the drawings—it is part of the project, as if  described in the other.

For instance, if the construction drawings do not show the door hardware (hinges, locks, handles, and other components) but the hardware is described in the specifications, the owner will get the doors with the stated hardware. If the drawings had precedence over the specifications, the owner would receive doors without hinges and handles.

Generally, there is little overlap between the drawings and the specifications. More importantly, there should be no conflict between them. If a conflict between the two documents is identified, the contractor must bring it to the attention of the architect promptly. In fact, construction contracts generally require that before starting any portion of the project, the contractor must carefully study and compare the drawings and the specifications and report inconsistencies to the architect.

If the conflict between the specifications and the construction drawings goes unnoticed initially but later results in a dispute, the courts have in most cases resolved it in favor of the specifications—implying that the specifications, not the drawings, govern the project. However, if the owner or the design team wishes to reverse the order, it may be so stated in the owner-contractor agreement.