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Construction and Structural Design Systems Research in the United States: An Overview Executive Summary This study viewed construction and structural design as prin- cipal components of the profession of civil engineering. A review of the history of each component discloses that research has re- ceived less attention in construction than in structural design, although there are a number of instances in which past research ac- complishments have profoundly influenced construction practice. Traditionally, the role of the federal government in sponsoring re- search in the fields covered by this pane] has been disappointingly limited; recent trends in this support are very promising. In further probing the status of research support in these fields, the pane] found that the key factors influencing the degree of support relate to the nature of the product (i.e., it is one of a kind), the university status of the discipline (which is generally weak for construction), the relatively small amount of industrial support, and the indifferent attitudes on the part of the public and in the industry itself concerning research on construction and structural design. The question of the adequacy of new research talent is also explored. It is found that, overall, the supply of research-oriented graduates is sufficient to carry out the current level of research. As we look at research areas directed toward the use of advanced technologies such as robotics, however, it is evident that there is an undersupply of research-oriented graduates. Moreover, a general shortage of research talent would result if funding for research 115

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116 DIRECTIONS IN ENGINEERING RESEARCH increased to levels comparable to those in other engineering fields and to levels needed to meet the challenges posed by important new research opportunities. Within this generally discouraging climate, a number of im- portant research thrusts are not receiving adequate attention. Those identified by the pane! as being of highest priority (see the next section) are (1) construction robotics, (2) computer-aided de- sign, (3) rapid excavation, (4) mixed structural systems (involving the use of a combination of structural materials e.g., structural steed and reinforced concrete acting together to resist Toads), and (5) marine construction. These research areas encompass a broad range of applica- tions, in some cases overlapping the goals and technological scope of other panels of the Engineering Research Board. They hold out the promise of advances in the efficiency, rationality, and com- petitiveness of modern construction and structural design practice in the United States. Such advances would not only improve the quality of life of most Americans, but would also enhance the po- sition of American companies in the increasingly competitive and technology-intensive construction industry worldwide. Finally, the pane! believes that the research thrusts identified in this report over a realistic hope of obtaining the support of public agencies and industry. Recommendations Measured against annual U.S. construction expenditures of some $200 billion, federal support of construction and structural design research is extremely limited. Therefore, the pane! recom- mends that: . Federal funding for engineering research in construction and structural design should be substantially increased. Such research should be supported through new programs within the federal mission agencies as well as through the National Science Foundation (NSF). A suitable approach would be to establish centers for construction research, perhaps along the lines of the NSF's Engineering Research Centers. The existing capacity of

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 117 federal and national laboratories for construction-related research should also be more fully utilized. The nature of research is such that achievements of profound long-range importance often result only from the vision of an individual who is not allied with the mainstream of the industrial process or current thinking. Relatively small but highly innovative research investigations are essential to the health of research in this or any other field of engineering. Therefore: . The funding of large research centers should not disrupt the continuity of funding for novel, individual research efforts. In particular, the general scheme of NSF sponsorship should continue to provide mechanisms to support this type of research. The construction/design industry is fragmented, as it com- prises a very large number of (mostly small) firms. Given this structure and the "one-of-a-kind" nature of projects, there has traditionally been little support for long-range research within the industry. Yet the advent of new technologies and increased in- ternational competition for the global and domestic construction market over both an opportunity and a challenge that demand more attention to research. As a result, the pane! recommends that: . The professional societies and trade associations should inform their membership as to the need for research and should attempt to organize sponsorship and support for industry-wide collaborative research efforts. Such research might be performed at regional R&D centers and could include applied research aimed at making research advances more directly applicable to the in- dustry's needs. In general, the supply of doctoral researchers in construction and structural design is sufficient to carry out the current level of research. However, there is a shortage of researchers able to adapt new technologies such as robotics to the special needs of the field. In addition, if research funding were to increase significantly, the supply of researchers would quickly prove inadequate. Therefore: . More students especially U.S. residents must be attract- ed into the high-technology aspects of construction and structural engineering research. The primary means of doing this would be to increase the funding of research. In order to attract more students

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118 DIRECTIONS IN ENGINEERING RESEARCH into graduate study in the field, graduate student stipends should be raised to approximately $15,000 per year, in 1986 dollars. Part of the reason for the traditionally low support for research in this field is the widespread public perception that design, con- struction, and maintenance are unsophisticated, Tow-technology endeavors. Thus, the pane! recommends that: . The professional societies and trade associations should increase their public relations effort devoted to informing the pub- lic of the intellectual challenges and achievements represented by modern construction projects of every kind. The panel identified the following important or emerging areas of construction and structural design research as being especially worthy of support: . construction robotics extending and expanding the func- tions and capabilities of industrial robots to meet the needs of the construction environment; . computer-aided designachieving the potential that com- puter-aided design offers for structural design in such areas as improving nonlinear behavior and analysis, modeling geometrical complexity, enabling better coordination of analysis and experi- ment, improving realism in design analysis, advancing interactive computer graphics, and extending computer-aided design through the fabrication phase; rapid excavation increasing the speed of tunneling and improving the systems by which ground is classified; mixed constructionimproving our basic understanding of the characteristics and uses of mixed construction (especially reinforced concrete in various combinations with structural steel); and . marine construction finding new and better ways to build coastal structures of all kinds and to protect them from the severe coastal environment. Introduction and Background The fields of construction and structural design are comple- mentary elements of the profession of civil engineering. Construc-

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 119 ton is strongly associated with the management of people and resources and deals with the actual environment, whereas modern structural design is founded in mathematical analysis and is based on a modeling of the presumed environment. These fields are drawn together at the interface between construction and design, and again during the subsequent construction process whenever the model and reality are at odds. Moreover, the trend in re- lated engineering research driven by developments in computers, sensors, and robotics is toward a greater unification of the de- sign/construction process than has heretofore prevailed. Construction has had, on the surface, less of a tie to re- search than has structural design. Yet certain research has af- fected construction profoundly. Concepts of ready-mixed concrete and prestressed concrete, of cold-formed, light-gage steel, and of connections in steel, to mention just a few, were transformed into routine practice only after theoretical and laboratory tests had established their feasibility, criteria, and operational procedures. Nevertheless, measured against the vast annual U.S. construction expenditures estimated by some sources to be $200 billion per year construction research budgets are miniscule. In addition, there are only a handful of construction research centers in the United-States, such as the U.S. Army Corps of Engineers' Con- struction Engineering Research Laboratory and Waterways Ex- periment Station at Vicksburg, Mississippi; the National Bureau of Standards' Center for Building Technology at Gaithersburg, Maryland; and the U.S. Navy's Naval Civil Engineering Labora- tory at Pt. Hueneme, California. The relatively low level of construction research in the United States can be compared with the much higher level in some other countries. For example, each of the six largest architec- tural/engineering/construction firms in Japan maintains a large engineering laboratory; there are no U.S. counterparts to these laboratories. Reportedly, the Japanese government suggested to these companies that they apply a certain percentage of their rev- enues to research. The largest of these laboratories has a work force of 40~500 people and excellent research and testing equip- ment. The rapid use of its own R&D makes the parent company more receptive to the developments of others. Each major com- pany has a technical staff that offers a client all required services, from initial concept to completed structure.

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120 DIRECTIONS IN ENGINEERING RESEARCH Research by Japanese government agencies is mainly of an applied nature. However, the government also devotes significant efforts to fundamental research, and the results of this research are implemented rapidly. New construction research national labora- tories have recently been built in Japan. One large construction research facility was built at Tsukuba during the late 1970s. This facility covers research on buildings, bridges, etc., and is prepared to do large-scale testing. The facility is reported to have cost $350 million. In addition, in the early 1980s the Nuclear Power Engineering Test Center was constructed in the city of Tadotsu, in Shikoku. The dominant feature of this facility is a large-scale, high-performance vibration table, which can shake a specimen weighing 1,000 tons with acclerations comparable to strong earth- quakes. This facility is reported to have cost in excess of $200 million. It is anticipated that construction research carried out in these two Japanese facilities will have an important influence on the construction industry in Japan, as well as on the field of structural engineering generally.* Structural design research, on the other hand, has a long his- tory of activity, even if organized support for it floes not. It is built on centuries of experience and empiricism, predating Roman times, so that even the most modern structure rests in part on this early Research in design. Design thus involves a combina- tion of experience and innovation, with (today) experiment and mathematical analysis providing both inspiration and backup. Modern structural design analysis had its beginnings early in the nineteenth century. Since that time, progress has advanced on a wide front, both geographically and topically, and there are many research groups. Important contributions can be made by such small groups and individuals, so thousands of individuals la- bor at structural design research throughout the world. The role of mathematics and computation in structural engineering has pro- gressed from one of just analysis into an active role in design, for example, in the proportioning of members. Yet it is widely recog- nizect that the latter capability is in its infancy when consideration is given to the overall goal of efficient, reliable, and economical de- sign. Now, as in the past, the first steps in design the choice of type of structure and construction material are the keys to good *National Research Council. Earthquake Engineering Research 1982. Washington, DC: National Academy Press, 1982.

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CONSTRUCTION AND STRUCTU~4L DESIGN SYSTEMS 121 design. Concepts of design theory and expert systems that could permit improved preliminary designs have barely surfaced. The history of research sponsorship in construction and struc- tural design has been similar for both disciplines. Prior to the First World War, research in both areas was essentially unspon- sored. Achievements were recorded by individuals in universities or private practice out of intellectual curiosity, as part of the ex- pected work of a professor, or in pursuit of a potentially profitable idea. After that time, industry took a greater interest through trade and professional associations such as the Reinforced Con- crete Research Council, the Welding Research Council, the Struc- tural Stability Research Council, the American Iron and Steel Institute, the American Institute of Steel Construction, the Pre- stressed Concrete Institute, and the Portland Cement Association. Government also got involved through such agencies as the U.S. Army Corps of Engineers, the Federal Highway Administration, the National Bureau of Standards, the Bureau of Reclamation, the National Aeronautics and Space Administration, and the research offices of the respective branches of the armed forces. Government and industry R&D was a mixture of work supported at universities and internal research in units such as the Portland Cement As- sociation Laboratories, U.S. Steel's Monroeville Laboratory, and Bethlehem Steel's Homer Laboratory. It is fair to say that none of these sponsoring units can be classified as large in either the size of their research expenditures or the intrinsic value of the supported projects. Much of the work that was done was also supported indirectly by universities or individuals. A major source of support at least for structural (resign has arisen in the past 20 years via the NSF. Still other support has come from such agencies as the Office of Naval Research, the Air Force Office of Scientific Research, and the Army Research Office, although to a more limited extent than in fields directly related to the missions of these agencies. In construction, an extensive amount of R&D has been done by individual companies, often on a relatively short-range basis. In order to solve an immediate problem, companies frequently develop innovative ideas son the job." Lightweight, nonshrink, expansive structural concrete, the slurry trench wall method of supporting sidewalls during excavation, tunneling machines, and the application of prestressing and pretensioning to concrete piles

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122 DIRECTIONS IN ENGINEERING RESEARCH were all developed in this manner by individual American com- panies. Although this pragmatic approach suffers from high costs and a high incidence of very expensive failures, the disadvantages have often been offset by the advantages of immediately transfer- ing R&D into actual practice. As noted previously, structural design supports subsequent construction activity on projects such as tall buildings, manu- facturing plants, dikes, roads, dams, bridges, tunnels, and fixed marine structures. The role of structural design in such fields as automotive, ship, and aerospace design is extensive; work in these areas has often been the starting point for research that eventually proved to be critically important to other applications, including construction. Moreover, the structural design of mechan- ical devices for operation under severe environments and loading conditions has spawned research with a beneficial side-effect on structural design related to civil engineering construction. This panel has, for the most part, limited its attention to the traditional applications of structural design; it has also sought, however, to identify research issues and directions that are broadly applicable to structural engineering. The pane] did this because it supports the objective of the Engineering Research Board to em- phasize, among many needed specific research directions, a limited number of major thrusts. The pane] received suggestions from over 100 individuals and organizations, including engineering deans, re- search laboratory directors, and Presidential Young Investigators. These external inputs described specific needs and also some re- search avenues of key importance to the vitality of construction and structural design research in general; thus, these inputs were valuable aids in identifying specific major thrusts. Policy Issues Regarding Federal Support of Research Laboratories of government agencies, or laboratories with close ties to the federal government, such as those cited earlier, are well-established contributors to research in construction and structural design. When specific major thrusts In engineering re- search are adopted as national objectives, the policy should be to

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 123 effect the full participation of existing federal laboratories whose research emphases are relevant to those thrusts. A different role is played by federal executive agencies, known as "missions agencies (e.g., the Department of Defense and the National Aeronautics and Space Administration) in their interface with independent research laboratories and universities engaged in research. Unfortunately, construction and structural design have had Tow visibility within the mission agencies. This may be due to the fact that, whereas many agencies are involved in construction, construction is not the central mission of any agency. Therefore, there is less sponsorship from the mission agencies for construction research than there is for other fields of research. It should be emphasized, however, that the mission agencies have demonstrated the effectiveness of their support of construc- tion research especially in the case of projects whose success depended on the field experience and data collection opportuni- ties that can be found only on-site. Results from these research projects eventually had, in many cases, a strong impact on pre- vailing construction procedures. During the past few years the NSF, whose role in the support of basic research is vitally important, has given emphasis to the sponsorship of projects that feature partnerships between univer- sities and industry. This is currently evidenced in the Engineering Research Centers (ERCs) program. Because such centers are the basis for the type of major programs recommended in this report, it follows that the ERCs concept has the panel's support. Indeed, one or more ERCs directed specifically at research in construction and structural design would do much to fill a notable gap in the nation's overall engineering research effort. Nevertheless, the pane! is concerned about the continuity of funding for innovative research investigations that generally in- volve the efforts of an individual investigator and just one or only a few graduate students. As this report was being written, word was received of a new NSF program, entitled Expedited Awards for Novel Research, established to fund innovative research. This program provides modest funding for such investigations on a 1-year basis without having to go through the normal proposal process. This Is an excellent initiative and the panel hopes it will be given every chance for success. The nature of research is such that certain accomplishments of profound long-range importance often result only from the vision

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124 DIRECTIONS IN ENGINEERING RESEARCH of an individual who is not allied with the mainstream of the industrial process or current thinking. The continued existence of a mechanism to support this type of research is a key to the health of the overall research environment. Consequently, in respect to federal policy issues, it is urged that the general scheme of NSF sponsorship continue to provide mechanisms that encourage the individual researcher. Furthermore, the clustering of research resources to programs of the type described the section on Especially Important Areas of Construction and Structural Design Systems Research should be designed so as not to eliminate opportunities for a nationwide range of institutions to contribute to the success of engineering research. With emerging interactive techniques for networking, teleconferencing, etc., there is ample opportunity to involve mul- tiple institutions in clustered, synergistic research efforts. Issues that Determine the Health of the Field THE ADEQUACY OF NEW RESEARCH TALENT As in other fields, the health of research in construction and structural design is fundamentally dependent on the existence of the human talent needed to identify research projects and success- fully complete them. Civil engineering is the primary discipline from which re- searchers and practitioners in this field are drawn. Undergraduate enrollments in civil engineering have been declining, relative to virtually all other branches of engineering, for the past 10 years. Recent indicators show a decline of enrollments in absolute terms as well. This might suggest that the future availability of research manpower is threatened. However, that is not necessarily the case. In engineering, when job opportunities in a certain field be- come less attractive at any time, there is a tendency for students either to go into another branch of engineering or to continue on into graduate studies rather than enter the work force. As a consequence of the latter tendency, graduate enrollments in civil engineering have risen in recent years.

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 125 The most significant rise has been in master's degree enroll- ments. Yet, although graduates at this level contribute to research to a certain extent, in general they do not contribute to the pool of research talent per se. The necessary exposure to research takes place mainly at the next level, as a result of doctoral studies. The number of doctoral degree recipients in construction and struc- tural engineering has increased moderately. It can be said that, as a result of this increase and the decrease in undergraduate enroll- ments, the "crisis" seen in other fields (e.g., electrical engineering) with regard to the number of Ph.D.s available for research and teaching is not present in civil engineering. The supply of doctoral researchers would appear to be sufficient to carry out the current level of research in construction and structural design. However, an examination of the adequacy of new talent in a field that is based principally on the overall output of advanced degree recipients and on trends in the size of that output misses a key point. The research directions defined in the next sec- tion identify specific technologies in which research specialists are scarce. A field such as construction robotics, for example, obvi- ously demands expertise in both construction and robotics. It is well known that graduate education is producing too few research specialists in robotics, among whom are only a miniscule num- ber whose interests (let alone their studies) are oriented toward construction. Thus, the challenge is to attract more students into the special, high-technology aspects of construction and structural engineering research. Fundamentally, the basis of attraction must be the existence of programs that hold out the promise of excit- ing careers. The research recommended the next section would certainly be a basis for such programs. Concomitantly, the attitudes of civil engineering students to- ward advanced research of this type need to be shaped in a positive way. The long-term health of the field demands that the educa- tion of civil engineers include extended experience with computers and with technology related to computers, not merely computer programming. Given the one-of-~kind nature of constructed sys- tems, civil engineers must have sufficient knowledge of the new technology to use and modify it in ways appropriate for design and construction. Curricula should be designed to enable the next generation of civil engineers to make appropriate technical choices and to develop solutions that integrate computers and operational

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 131 largely on advanced technology, places a new and urgent emphasis on research in this field. Especially Enportant Areas of Construction and Structural Design Systems Research As noted in the introduction, the panel benefited from a wealth of suggestions about lines of research that ought to be pursued. From its own deliberations, and taking these suggestions into consideration, the panel identified the following major thrusts: construction robotics; computer-aided design; rapid excavation; onyxes construction; and marine construction. The rationale for these thrusts, along with their detailed features, is presented in the following discussion. CONSTRUCTION ROBOTICS The construction industry is one of the largest segments of the economy, yet it has chronically the lowest productivity rate among major industrial segments. This is because every facility built is not only custom-designed for its specific intended purpose, but also custom-built, largely on-site. Consequently, the industry is labor-intensive, and that labor operates in a hazardous envi- ronment, exposed to weather and other factors that all tend to reduce productivity and affect the quality of the work produced. With human labor still a major source of energy for such opera- tions as lifting and installation, the size of components installed is governed by human physical capacity. Construction robotics has the prorn~se of significantly altering the construction workplace. The primary effect of construction robotics cannot be a simple one-to-one replacement of workmen by robots doing the same task. Rather, construction robotics must achieve several of the following objectives:

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132 DIRECTIONS IN ENGINEERING RESEARCH . extend vision (i.e., sensing) capabilities into new domains (e.g., underground, inside bulk concrete, inside small-diameter pipes); . provide high-quality and highly controllable work (e.g., au- tomatic welding with self-diagnosis and self-inspection capabilities, automatic drills with controls that minimize overshoot); . extend the workplace of construction workers (e.g., under- ground, underwater, and into cold regions); increase the safety of and reduce health hazards faced by workers in all construction environments; provide mobility coupled with a very high degree of dimen- siona] control over large, changing job sites; ~ provide lifting and accurate positioning capabilities for very large payloads; and . provide versatility over a wide range of functions, project sites, and project sizes. Some of the requisite functions, notably sensing, control feed- back, etc., are Inheritable from industrial robotics. Many other functions are diametrically opposite to the needs of industrial robots (e.g., mobility, flexibility, and high payload-to-weight ra- tio). Therefore, significant research is needed to proceed from the present state of industrial robotics to the first generation of construction robots. The first phase of research that will be needed is to iden- tify, develop, and construct prototypes of classes of construction robots with the requisite capabilities. The next (or, perhaps, a concurrent) phase will be to investigate the feedback from such tools that is, to develop modified design concepts and methods, as well as new construction materials and methods, that exploit the radically new construction processes that can be provided by robotics. COMPUTER-AIDED DESIGN The phrase "computer-aided designs has been used so widely and loosely of late that it is now almost a cliche. This is unfor- tunate because computer-aided design is a serious activity that is becoming and will remain a central part of structural design. What has been accomplished so far is only the primitive begin- ning of what should eventually be a natural, engineer-controDed,

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 133 computer-assisted design technology. Realizing the computer's po- tential for design will require a large amount of both goal-oriented engineering research and problem-oriented science research. The following discussion emphasizes engineering research. Computer-aided design in structural engineering extends from a computerized sketch pad (a digitizing tablet and a dynamic graphics screen that an engineer and his client can use in exploring concepts and schemes) to the automated control of fabrication. Construction control and maintenance lie beyond this definition except to the extent that they involve redesign. Among the reasons advanced for the use of computer-aided design are the following: it facilitates the study of alternatives; it frees the engineer from the burden of routine calculation and is essential to the use of advanced analysis; ~ it can be an aid, through visualization via computer graph- ics, to the understanding of structural behavior; ~ it can facilitate the use of experimental data and proba- bilistic considerations in actual design; . it can be effective in the integration of the entire design process from concept to the fabricated structure; it can be cost effective; and . it can facilitate migration from present computation-orient- ed algorithmic approaches to future knowledge-based, reasoning- oriented heuristic approaches. In general, these qualities remain pursuable goals rather than commonly achieved actualities. To make the potential reality, the following areas of research must be pursued. No ntin ear Beh avio ~ a n ~ A n alysis Prior to failure, structures evidence nonlinear behavior due to plastic deformation of the material and large deflections. Much computer-related research is required before thorough nonlinear analysis of structures can become the profession's norm. Existing advanced methods of analysis can cope with nonlinear behavior, but they enjoy only limited application in practice. This type of analysis, however, has scope for further theoretical development, with the objective of making its results ever more faithful to reality.

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134 DIRECTIONS IN ENGINEERING RESEARCH Proportioning of Elements of Structural Systems Many computerized design aids can be routine commercial developments, but others such as those that treat the effects of semirigid connections on system stability require bona fide re- search. Aids for the treatment of these problems would be sophis- ticated programs (probably with graphics) that would assist the engineer in understanding and translating reliable information on structural behavior into physical dimensions. Coordination of Analysis and Experiment Significant advances in design philosophy have been made in recent years; but more research is needed to produce truly rational designs. These designs must account for loads due to environmen- tal conditions, such as wind and snow, that are not constant and uniformly distributed, but rather have a statistical, time-varying nature. The variation of size and material properties of the as-buiTt structure also requires consideration. Probability theory must be brought to bear. Much of what is required can be described as computer-aided design research in which a comprehensive view of the whole analysis/design process is taken including the facts that certain types of design procedures go with certain types of analyses and that applied loads and the resistance of the con- structed structure may not be completely independent variables. Realism in Design Analysis There is a continuing need to advance the art of three-dimen- sional analysis and our ability to mode! geometrical effects wher- ever they occur from elements with unsymmetrical cross-sections, through cross-section distortional effects, to gross system geom- etry complexities. This applies to structures of every size. For example, no one has ever analyzed a tall building (e.g., one of 70 stories) in its entirety for the full effects of earthquake, wind, or even gravity loads. Further, the chances are that in the foreseeable future no design office wiD be able to do so, even with advanced analysis methods, given the costs of computation and the limits on the capacity of the computers available to practitioners. Such buildings are being built, however, even though their response to an event such as a major earthquake is not well understood. Therefore, it is important to society that as supercomputers be- come available at research centers, one of their applications should

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 135 be the study of the behavior, up through failure, of very large three-dimensional structural systems. If current expections are re- alized, sup ercomputers could become national resources that could yield an understanding of large structural systems unattainable in any other way. Interactive Computer Graphics This topic has been the subject of active research for some time. Still, it is desirable to reaffirm that interactive graph- ics should continue to be the key to much of the most effective computer-aided design techniques, and that further engineering research is needed to advance such areas as the visual interpre- tation of nonlinear and dynamic behavior and the use of color in three dimensions. Fabrication Carrying computer-aided design through fabrication (the structural engineering equivalent of manufacturing) is another vi- ta] activity. Many developments in this direction are taking place commercially. The engineering research component comes more under the heading of project-wide integration. Synthesis of Alternatives Analysis-based computer-aided design tools are usable only after promising structural alternatives have been identified. Yet the key decisions are made and the major innovations are intro- duced at the earlier, conceptual stages of design when alternatives are first synthesized. Concepts from the newly emerging area of Design Theory and Methodologies of Knowledge-Based Expert Systems can be brought to bear on this task. Research is needed to expand these concepts and methodologies to meet the require- ments of structural design. RAPID EXCAVATION The estimated annual cost of domestic tunneling is between $0.5 billion and $1 billion. The 90 largest tunnels planned or under construction worldwide represent an investment of at least $74 billion (NeustadtI, 1986~. Improved techniques derived from research could lead to substantial savings. Research to increase

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136 DIRECTIONS IN ENGINEERING RESEARCH the speed of excavation should be a key objective.* The main driver here are interest rates, which (although they are currently relatively low) have escalated from 4 to 12 percent and even higher in the past 30 years. There needs to be an integrated approach to tunneling accom- plished by blending the knowledge and objectives of engineering geologists, designers, experienced tunnel contractors, and equip- ment manufacturers. Presently there is a widespread lack of un- derstanding across the boundaries of these four disciplines. A central problem to be resolved is the classification of the ground, including its rock content. With the four groups of en- gineers working together, the ground can be classified with much greater certainty than it was as recently as 15 years ago. The designer can customize his or her ideas of permanent support or lining according to the ground conditions. This can be done so that the system of construction designed for the ground by the machinery contractor can be used. Machinery construction sys- tem designs to fit classification of ground can be foreseen that will remarkably speed up tunnel construction. Preconstruction classification of ground into ~10 categories can be visualized with designs and contractor's systems and ma- chinery to fit them. Thus, in rock-tunneling machines with greater thrust, the speed of rotation will be dependent on the size of the tunnel and the degree of jointing; faster machines can reduce sup- port problems. Much time is lost in installing supports during excavation. Preciassifying the ground, and customizing the ~le- sign, system, and machinery is an answer to this problem. Various means have been developed to install the tunnel liner immediately behind the advancing shield or excavation. Precast tunnel liners are mechanically installed in some Japanese systems. In other cases, fiber-reinforced concrete is extruded, or shotcrete applied, by a robot Gun. In order to develop such a classification system, a major re- search effort is needed, entailing contributions by university labm ratories, engineering geologists, and machinery manufacturers and *For example, the use of the new "earth-pressure-balance" method of tunneling enabled a Japanese firm to bid $5 million below the engineer's estimate for a sewer contract in San Francisco, and to complete the tunnel 3 months ahead of schedule (Moavenzadeh, 1985~.

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 137 tunneling contractors. Projects must be selected to test the cias- sification system. For best efficiency this program will require the guidance of a central laboratory or research center. MIXED CONSTRUCTION Mixed steel/concrete structural elements and systems are not new. Ordinary reinforced and prestressed concrete structures are, of course, forms of mixed construction. Concrete-fi~led pipe columns, composite bridges, and composite floor decks have been around for a long time. Turbine pedestals in conventional power plants sometimes consist of a structural steel framework embedded in rather massive concrete foundations. In less developed coun- tries one finds crucle latticeworks of light, open steel beams and columns that provide staging support during construction and in- tegral reinforcement for the completed building after encasement in concrete. In Japan this type of building has become a highly developed method of engineered construction. Recently, however, mixed construction- that is, systems that involve reinforced concrete and structural steel components that together resist all gravity and lateral forces has taken on a new connotation. It is being used in new, innovative ways in high-rise buildings, bridges, and offshore structures to take advantage of the best attributes of both reinforced concrete and structural steel. Mixed construction possesses structural efficiency and economy, versatility, as well as structural stiffness and flexibility (in both the structural and architectural senses) where required. An example is the use of concrete shear walb or framed tubes for lateral load resistance, combined with steel floor framing. Modern mixed construction is an example of practice outpac- ing theory. Creative engineers and builders have seen the advan- tages of mixing structural steel and reinforced concrete and are using this approach. Developments in research, codification, and professional and academic organizations have lagged. Much think- ing is still conditioned by administrative, financial, and emotional ties to Concrete (meaning ordinary reinforced or prestressed concrete) or "steed, without realizing that each is just a building material to be used naturally where it best meets the needs of a design problem. A primary need is to break down the artificial barriers that impede the development of mixed construction. This goes well

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138 DIRECTIONS IN ENGINEERING RESEARCH beyond research, but research is an important factor, for there are uncertainties in the interaction of steel and concrete that can be resolved only by intensive study. Dr. H. Tyengar has listed the main research needs for mixed construction in buildings. The following is an outline of his list, contained in a paper presented before the 1984 Tall Buildings Council Meeting: . development of inelastic design methods for mixed systems . In seismic areas; development of design criteria for concrete shear wall-steel space frame systems; ~ mechanism of local transfer between steed and concrete in compression elements; . evaluation of relative shortening between steed and concrete vertical elements; behavior of connections, and design methods for propor- tioning them; and . development of a superior, rational design method for steel- concrete composite columns, such as the Structural Stability Re- search Council Subcommittee's method. In addition, the durability of steel and concrete as construction materials requires research attention. The durability of construc- tion materials is a broad issue that affects all types of structural designs. Progress in construction requires making the best use of steed and concrete in any situation and in any combination. A large body of engineering research must be accomplished before this can be done rationally and with confidence. MARINE CONSTRUCTION The pace of construction along the coasts of the United States is accelerating, because of such factors as population growth, de- mographic changes, and urban concentration along the coastlines. At the same tune, the yearly damage to existing structures (both public and private) from storms, tsunamis, and landsTide/erosion is many billions of dollars. If the sea level should rise, the severity of this damage will increase exponentially. Coastal construction is growing rapidly in terms of numbers of structures, exposure to more severe environments, and costs. It includes wastewater outfalIs, power plant intakes and discharges,

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS 139 petroleum pipelines and terrn~nals, fishing and recreational piers, seawalIs, breakwaters, groins, etc. The coastal environment is the most severe of all, in that both land and sea elements interact in a highly dynamic fashion. Coastal engineering and construction is emerging as a more criti- cal national issue than offshore construction, because spectacular developments have already taken place in the offshore industry. A host of research challenges have been identified, encom- passing needs in such related fields as structures, geotechnical engineering, hydrodynamics, and naval architecture. The most outstanding of these needs are port; resolution of the problems of sand infix] and sediment trans- . prediction of the response of floating structures and pipe- lines on the ocean floor in the shallow-water and surf zones; . the identification of approaches to the stabilization of beach- es during and after construction; placement and surveying techniques for rock placement; . the extension of drilling techniques for placing pipelines and cables through the surf zone; . material and structure problems of special concern in ma- rine construction, such as the behavior of confined concrete under overload and the response of structures to impact loads from ship collisions and ice; and . the improvement of seafloor soils, which involves both con- struction techniques and an understanding of geotechnica] behav- ior. Examples of this are cement stabilization and freezing.

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140 DIRECTIONS IN ENGINEERING RESEARCH Appendix Responses to the Engmeer~ng :Research Board's Request for Assistance from Universities, Professional Societies, and Federal Agencies and Laboratories Requests for assistance were sent by the Engineering Research Board to a number of universities, recipients of Presidential Young Investigator awards, professional societies, and federal agencies and laboratories in order to obtain a broader view of engineering research opportunities, research policy needs, and the health of the research community. Some of the responses included comments on engineering research aspects of construction and structural design; these were reviewed by this pane! to aid in its decision process. The pane} found the responses most helpful and wishes that it were possible to individually thank all those who took the time to make their views known. Because that is not practical, we hope nevertheless that this small acknowledgment might convey our gratitude. Responses on aspects of construction and structural design were received from over 100 individuals representing 37 different organizations (Table Am. Whereas most of the responses ad- dressed priority research needs, several respondents did reflect on policy issues. Although many of the research needs and issues of policy and health addressed by the respondents were similar to those noted by pane} members, the broadened perspective pro- vided by the responses to the survey was most beneficial in the panel's deliberations.

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CONSTRUCTION AND STRUCTURAL DESIGN SYSTEMS TABLE A-1 Organizations Responding to Information Requests Relevant to Construction and Structural Design Systems Research UNIVERSITIES Clarkson University Cornell University Duke University Illinois Institute of Technology Lehigh University North Carolina State University Northwestern University Old Dominion University Princeton University Purdue University Texas A&M University University of California, Los Angeles University of Hawaii University of Houston University of IllinoisUrbana/ Champaign University of Kansas University of Michigan University of Minnesota University of Oklahoma University of Pennsylvania University of Texas at Austin PROFESSIONAL ORGANIZATIONS American Institute of Aeronautics and Astronautics American Institute of Chemical Engineers American Society of Civil Engineers American Society of Mechanical Engineers Institute of Industrial Engineers Industrial Research Institute Society of Engineering Science, Inc. AGENCIES AND LABORATORIES Air Force Institute of Technology Air Force Office of Scientific Research Army Materials and Mechanical Research Center Brookha~ren National Laboratory NASA Goddard Space Flight Center NASA Jet Propulsion Laboratory NASA Langley Research Center Office of Naval Research Oak Ridge National Laboratory 141