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OCR for page 115
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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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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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 design—achieving 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 construction—improving 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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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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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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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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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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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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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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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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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 Illinois—Urbana/
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
Representative terms from entire chapter:
civil engineering
