3.7 Geotechnical Engineering Investigation
Since construction is site specific, it is very important to investigate the subsurface conditions which often influence the design of a facility as well as its foundation. The uncertainty in the design is particularly acute in geotechnical engineering so that the assignment of risks in this area should be a major concern. Since the degree of uncertainty in a project is perceived differently by different parties involved in a project, the assignment of unquantifiable risks arising from numerous unknowns to the owner, engineer and contractor is inherently difficult. It is no wonder that courts or arbitrators are often asked to distribute equitably a risk to parties who do not perceive the same risks and do not want to assume a disproportionate share of such risks.
Example 3-10: Design of a tie-back retaining wall
This example describes the use of a tie-back retaining wall built in the 1960's when such construction was uncommon and posed a considerable risk. The engineer designing it and the owner were aware of the risk because of potentially extreme financial losses from both remedial and litigation costs in the event that the retaining wall failed and permitted a failure of the slope. But the benefits were perceived as being worth the risk--benefits to the owner in terms of both lower cost and shorter schedule, and benefits to the engineer in terms of professional satisfaction in meeting the owner's needs and solving what appeared to be an insurmountable technical problem.
The tie-back retaining wall was designed to permit a cut in a hillside to provide additional space for the expansion of a steel-making facility. Figure 3-9 shows a cross section of the original hillside located in an urban area. Numerous residential dwellings were located on top of the hill which would have been prohibitively costly or perhaps impossible to remove to permit regrading of the hillside to push back the toe of the slope. The only realistic way of accomplishing the desired goal was to attempt to remove the toe of the existing slope and use a tie-back retaining wall to stabilize the slope as shown in Figure 3-10.
Figure 3-9: Typical Cross Section of Hillside Adjoining Site
Figure 3-10: Schematic Section of Anchored Steel Sheet Pile Retaining Wall
A commitment was made by both the owner and the engineer to accomplish what was a common goal. The engineer made a commitment to design and construct the wall in a manner which permitted a real-time evaluation of problems and the ability to take mitigating measures throughout the construction of the wall. The owner made a commitment to give the engineer both the professional latitude and resources required to perform his work. A design-construct contract was negotiated whereby the design could be modified as actual conditions were encountered during construction. But even with all of the planning, investigation and design efforts, there still remained a sizable risk of failure.
The wall was successfully built--not according to a pre-devised plan which went smoothly, and not without numerous problems to be resolved as unexpected groundwater and geological conditions were encountered. Estimated costs were exceeded as each unexpected condition was addressed. But there were no construction delays and their attendant costs as disputes over changed conditions and contract terms were reconciled. There were no costs for legal fees arising from litigation nor increased interest costs as construction stopped while disputes were litigated. The owner paid more than was estimated, but not more than was necessary and not as much as if he had to acquire the property at the top of the hill to regrade the slope. In addition, the owner was able to attain the desired facility expansion in far less time than by any other method.
As a result of the success of this experience and others, the use of tie-back retaining walls has become a routine practice.
3.8 Construction Site Environment
While the general information about the construction site is usually available at the planning stage of a project, it is important for the design professionals and construction manager as well as the contractor to visit the site. Each group will be benefited by first-hand knowledge acquired in the field.
For design professionals, an examination of the topography may focus their attention to the layout of a facility on the site for maximum use of space in compliance with various regulatory restrictions. In the case of industrial plants, the production or processing design and operation often dictate the site layout. A poor layout can cause construction problems such as inadequate space for staging, limited access for materials and personnel, and restrictions on the use of certain construction methods. Thus, design and construction inputs are important in the layout of a facility.
The construction manager and the contractor must visit the site to gain some insight in preparing or evaluating the bid package for the project. They can verify access roads and water, electrical and other service utilities in the immediate vicinity, with the view of finding suitable locations for erecting temporary facilities and the field office. They can also observe any interferences of existing facilities with construction and develop a plan for site security during construction.
In examining site conditions, particular attention must be paid to environmental factors such as drainage, groundwater and the possibility of floods. Of particular concern is the possible presence of hazardous waste materials from previous uses. Cleaning up or controlling hazardous wastes can be extremely expensive.
Example 3-11: Groundwater Pollution from a Landfill
The presence of waste deposits on a potential construction site can have substantial impacts on the surrounding area. Under existing environmental regulations in the United States, the responsibility for cleaning up or otherwise controlling wastes generally resides with the owner of a facility in conjunction with any outstanding insurance coverage.
A typical example of a waste problem is illustrated in Figure 3-11. In this figure, a small pushover burning dump was located in a depression on a slope. The landfill consisted of general refuse and was covered by a very sandy material. The inevitable infiltration of water from the surface or from the groundwater into the landfill will result in vertical or horizontal percolation of leachable ions and organic contamination. This leachate would be odorous and potentially hazardous in water. The pollutant would show up as seepage downhill, as pollution in surface streams, or as pollution entering the regional groundwater.
Figure 3-11: Cross-Section Illustration of a Landfill
Before new construction could proceed, this landfill site would have to be controlled or removed. Typical control methods might involve:
The excavation and reburial of even a small landfill site can be very expensive. For example, the estimated reburial cost for a landfill like that shown in Figure 3-11 was in excess of $ 4 million in 1978.
3.9 Value Engineering
Value engineering may be broadly defined as an organized approach in identifying unnecessary costs in design and construction and in soliciting or proposing alternative design or construction technology to reduce costs without sacrificing quality or performance requirements. It usually involves the steps of gathering pertinent information, searching for creative ideas, evaluating the promising alternatives, and proposing a more cost effective alternative. This approach is usually applied at the beginning of the construction phase of the project life cycle.
The use of value engineering in the public sector of construction has been fostered by legislation and government regulation, but the approach has not been widely adopted in the private sector of construction. One explanation may lie in the difference in practice of engineering design services in the public and private sectors. In the public sector, the fee for design services is tightly monitored against the "market price," or may even be based on the lowest bid for service. Such a practice in setting professional fees encourages the design professionals to adopt known and tried designs and construction technologies without giving much thought to alternatives that are innovative but risky. Contractors are willing to examine such alternatives when offered incentives for sharing the savings by owners. In the private sector, the owner has the freedom to offer such incentives to design professionals as well as the contractors without being concerned about the appearance of favoritism in engaging professional services.
Another source of cost savings from value engineering is the ability of contractors to take advantage of proprietary or unusual techniques and knowledge specific to the contractor's firm. For example, a contractor may have much more experience with a particular method of tunneling that is not specified in the original design and, because of this experience, the alternative method may be less expensive. In advance of a bidding competition, a design professional does not know which contractor will undertake the construction of a facility. Once a particular contractor is chosen, then modifications to the construction technology or design may take advantage of peculiar advantages of the contractor's organization.
As a final source of savings in value engineering, the contractor may offer genuine new design or construction insights which have escaped the attention of the design professional even if the latter is not restrained by the fee structure to explore more alternatives. If the expertise of the contractor can be utilized, of course, the best time to employ it is during the planning and design phase of the project life cycle. That is why professional construction management or integrated design/construction are often preferred by private owners.
3.10 Construction Planning
The development of a construction plan is very much analogous to the development of a good facility design. The planner must weigh the costs and reliability of different options while at the same time insuring technical feasibility. Construction planning is more difficult in some ways since the building process is dynamic as the site and the physical facility change over time as construction proceeds. On the other hand, construction operations tend to be fairly standard from one project to another, whereas structural or foundation details might differ considerably from one facility to another.
Forming a good construction plan is an exceptionally challenging problem. There are numerous possible plans available for any given project. While past experience is a good guide to construction planning, each project is likely to have special problems or opportunities that may require considerable ingenuity and creativity to overcome or exploit. Unfortunately, it is quite difficult to provide direct guidance concerning general procedures or strategies to form good plans in all circumstances. There are some recommendations or issues that can be addressed to describe the characteristics of good plans, but this does not necessarily tell a planner how to discover a good plan. However, as in the design process, strategies of decomposition in which planning is divided into subproblems and hierarchical planning in which general activities are repeatably subdivided into more specific tasks can be readily adopted in many cases.
From the standpoint of construction contractors or the construction divisions of large firms, the planning process for construction projects consists of three stages that take place between the moment in which a planner starts the plan for the construction of a facility to the moment in which the evaluation of the final output of the construction process is finished.
The estimate stage involves the development of a cost and duration estimate for the construction of a facility as part of the proposal of a contractor to an owner. It is the stage in which assumptions of resource commitment to the necessary activities to build the facility are made by a planner. A careful and thorough analysis of different conditions imposed by the construction project design and by site characteristics are taken into consideration to determine the best estimate. The success of a contractor depends upon this estimate, not only to obtain a job but also to construct the facility with the highest profit. The planner has to look for the time-cost combination that will allow the contractor to be successful in his commitment. The result of a high estimate would be to lose the job, and the result of a low estimate could be to win the job, but to lose money in the construction process. When changes are done, they should improve the estimate, taking into account not only present effects, but also future outcomes of succeeding activities. It is very seldom the case in which the output of the construction process exactly echoes the estimate offered to the owner.
In the monitoring and control stage of the construction process, the construction manager has to keep constant track of both activities' durations and ongoing costs. It is misleading to think that if the construction of the facility is on schedule or ahead of schedule, the cost will also be on the estimate or below the estimate, especially if several changes are made. Constant evaluation is necessary until the construction of the facility is complete. When work is finished in the construction process, and information about it is provided to the planner, the third stage of the planning process can begin.
The evaluation stage is the one in which results of the construction process are matched against the estimate. A planner deals with this uncertainty during the estimate stage. Only when the outcome of the construction process is known is he/she able to evaluate the validity of the estimate. It is in this last stage of the planning process that he or she determines if the assumptions were correct. If they were not or if new constraints emerge, he/she should introduce corresponding adjustments in future planning.
3.11 Industrialized Construction and Pre-fabrication
Another approach to construction innovation is to apply the principles and organizational solutions adopted for manufacturing. Industrialized construction and pre-fabrication would involve transferring a significant portion of construction operations from the construction site to more or less remote sites where individual components of buildings and structures are produced. Elements of facilities could be prefabricated off the erection site and assembled by cranes and other lifting machinery.
There are a wide variety and degrees of introducing greater industrialization to the construction process. Many components of constructed facilities have always been manufactured, such as air conditioning units. Lumber, piping and other individual components are manufactured to standard sizes. Even temporary items such as forms for concrete can be assembled off-site and transported for use. Reinforcing bars for concrete can also be pre-cut and shaped to the desired configuration in a manufacturing plant or in an automated plant located proximate to a construction site.
A major problem in extending the use of pre-fabricated units is the lack of standardization for systems and building regulations. While designers have long adopted standard sizes for individual components in designs, the adoption of standardized sub-assemblies is rarer. Without standardization, the achievement of a large market and scale economies of production in manufacturing may be impossible. An innovative and more thorough industrialization of the entire building process may be a primary source of construction cost savings in the future.
Example 3-12: Planning of pre-fabrication
When might pre-fabricated components be used in preference to components assembled on a construction site? A straightforward answer is to use pre-fabricated components whenever their cost, including transportation, is less than the cost of assembly on site. As an example, forms for concrete panels might be transported to a construction site with reinforcing bars already built in, necessary coatings applied to the forms, and even special features such as electrical conduit already installed in the form. In some cases, it might be less expensive to pre-fabricate and transport the entire concrete panel to a manufacturing site. In contrast, traditional construction practice would be to assemble all the different features of the panel on-site. The relevant costs of these alternatives could be assessed during construction planning to determine the lowest cost alternative.
In addition to the consideration of direct costs, a construction planner should also consider some other aspects of this technology choice. First, the planner must insure that pre-fabricated components will satisfy the relevant building codes and regulations. Second, the relative quality of traditional versus pre-fabricated components as experienced in the final facility should be considered. Finally, the availability of components at the required time during the construction process should also be considered.
Example 3-13: Impacts of building codes
Building codes originated as a part of the building regulatory process for the safety and general welfare of the public. The source of all authority to enact building codes is based on the police power of the state which may be delegated by the state legislature to local government units. Consequently, about 8,000 localities having their own building codes, either by following a national model code or developing a local code. The lack of uniformity of building codes may be attributed to a variety of reasons:
The lack of uniformity in building codes has serious impact on design and construction as well as the regulatory process for buildings. Among the significant factors are:
3.12 Computer-Aided Engineering
In the past twenty years, the computer has become an essential tool in engineering, design, and accounting. The innovative designs of complicated facilities cited in the previous sections would be impossible without the aid of computer based analysis tools. By using general purpose analysis programs to test alternative designs of complex structures such as petrochemical plants, engineers are able to greatly improve initial designs. General purpose accounting systems are also available and adopted in organizations to perform routine bookkeeping and financial accounting chores. These applications exploit the capability for computers to perform numerical calculations in a pre-programmed fashion rapidly, inexpensively and accurately.
Despite these advances, the computer is often used as only an incidental tool in the design, construction and project management processes. However, new capabilities, systems and application programs are rapidly being adopted. These are motivated in part by the remarkable improvement in computer hardware capability, the introduction of the Internet, and an extraordinary decline in cost. New concepts in computer design and in software are also contributing. For example, the introduction of personal computers using microcircuitry has encouraged the adoption of interactive programs because of the low cost and considerable capability of the computer hardware. Personal computers available for a thousand dollars in 1995 have essentially the same capability as expensive mainframe computer systems of fifteen years earlier.
Computer graphics provide another pertinent example of a potentially revolutionary mechanism for design and communication. Graphical representations of both the physical and work activities on projects have been essential tools in the construction industry for decades. However, manual drafting of blueprints, plans and other diagrams is laborious and expensive. Stand alone, computer aided drafting equipment has proved to be less expensive and fully capable of producing the requiring drawings. More significantly, the geometric information required for producing desired drawings might also be used as a database for computer aided design and computer integrated construction. Components of facilities can be represented as three dimensional computer based solid models for this purpose. Geometric information forms only one component of integrated design databases in which the computer can assure consistency, completeness and compliance with relevant specifications and constraints. Several approaches to integrated computer aided engineering environments of this type have already been attempted.
Computers are also being applied more and more extensively to non-analytical and non-numerical tasks. For example, computer based specification writing assistants are used to rapidly assemble sets of standard specifications or to insert special clauses in the documentation of facility designs. As another example, computerized transfer of information provides a means to avoid laborious and error-prone transcription of project information. While most of the traditional applications and research in computer aids have emphasized numerical calculations, the use of computers will rapidly shift towards the more prevalent and difficult problems of planning, communication, design and management.
Knowledge based systems represent a prominent example of new software approaches applicable to project management. These systems originally emerged from research in artificial intelligence in which human cognitive processes were modeled. In limited problem domains such as equipment configuration or process control, knowledge based systems have been demonstrated to approach or surpass the performance of human experts. The programs are marked by a separation between the reasoning or "inference" engine program and the representation of domain specific knowledge. As a result, system developers need not specify complete problem solving strategies (or algorithms) for particular problems. This characteristic of knowledge based systems make them particularly useful in the ill-structured domains of design and project management. Chapter 15 will discuss knowledge based systems in greater detail.
Computer program assistants will soon become ubiquitous in virtually all project management organizations. The challenge for managers is to use the new tools in an effective fashion. Computer intensive work environments should be structured to aid and to amplify the capabilities of managers rather than to divert attention from real problems such as worker motivation.
3.13 Pre-Project Planning
Even before design and construction processes begin, there is a stage of "pre-project planning" that can be critical for project success. In this process, the project scope is established. Since construction and design professionals are often not involved in this project scope stage, the terminology of describing this as a "pre-project" process has arisen. From the owner's perspective, defining the project scope is just another phase in the process of acquiring a constructed facility.
The definition of a project scope typically involves developing project alternatives at a conceptual level, analyzing project risks and economic payoff, developing a financial plan, making a decision to proceed (or not), and deciding upon the project organization and control plan. The next few chapters will examine these different problems at some length.
The danger of poor project definition comes from escalating costs (as new items are added) or, in the extreme, project failure. A good definition of scope allows all the parties in the project to understand what is needed and to work towards meeting those needs.
Example 3-14: The Project Definition Rating Index (PDRI) for Building Projects The Construction Industry Institute has developed rating indexes for different types of projects to assess the adequacy of project scope definitions. These are intended to reflect best practices in the building industry and provides a checklist for recommended activities and milestones to define a project scope. The rating index is a weighted sum of scores received for a variety of items on the scope definition checklist. Each item in the checklist is rated as "not applicable" (0), "complete definition" (1), "minor deficiencies" (2), "some deficiencies" (3), "major deficiencies" (4) or "incomplete or poor definition" (5). Lower scores in these categories are preferable. Some items in the checklist include:
- Au, T. and P. Christiano, Structural Analysis, Prentice-Hall, Inc., Englewood Cliffs, NJ, 1987.
- Building Research Advisory Board, Exploratory Study on Responsibility, Liability and Accountability for Risks in Construction, National Academy of Sciences, Washington, D.C., 1978.
- Drucker, P.F., Innovation and Entrepreneurship: Practice and Principles, Harper and Row, New York, 1985.
- Gaylord, E., and C. Gaylord (Editors), Structural Engineering Handbook, McGraw-Hill Book Co., New York, 1979.
- Levitt, R.E., R.D. Logcher and N.H. Quaddumi, "Impact of Owner-Engineer Risk Sharing on Design Conservatism," ASCE Journal of Professional Issues in Engineering, Vol. 110, 1984, pp. 157-167.
- Simon, H.A., The Science of the Artificial, Second Edition, MIT Press, Cambridge, MA, 1981.
- Tatum, C.B., "Innovation on the Construction Project: A Process View," Project Management Journal, Vol. 18, No. 5, 1987, pp. 57-67.
- Pre-Project Planning Research Team, Pre-Project Planning Handbook Construction Industry Institute, Publication 39-2, April 1995.