⼟⽊⼯程（钢结构和钢筋混凝⼟结构）外⽂⽂献翻译
⽂献信息：
⽂献标题：Recent rearch and design developments in steel and composite steel–concrete structures in USA（近期美国在钢结构和钢筋混凝⼟结构研究和设计⽅⾯的发展）
国外作者：Theodore V.Galambos
⽂献出处：《Journal of Constructional Steel Rearch》,2000, 55(1-3):289-303
字数统计：英⽂4718单词，23395字符；中⽂7671汉字
外⽂⽂献：
Recent rearch and design developments in steel and composite steel–concrete structures in USA Abstract A brief review of the status of structural steel rearch in the US at the end of the Twentieth Century is prented in this paper to show that while many problems are being solved, there are new and challenging problems remaining. The chief impetus for continued rearch is that provided by natural disasters, such as earthquakes, tropical storms, tornadoes and floods occurring in denly pop
ulated urban areas. New materials and new experimental and computational technologies also give ri to new and exciting rearch problems.
Keywords: Bridges; Buildings; Design; Rearch; Steel structures; United States of America; Seismic behavior; High-performance materials
1. Introduction
七夕的诗The purpo of this paper is to give a brief overview of the current developments in structural steel rearch in the US, and of the future directions that the structural steel engineering rearch may take in the coming Century. The driving
forces of rearch in this field are the following:
new construction methods and construction products
new materials
economic considerations
natural disasters
Three of the motivations are common to all engineering developments, not just to structural engineering. However, the impetus due to natural disasters is unique to our field. Recent major natural disasters in the US, such as the Northridge earthquake in California and hurricane Andrew in Florida, have spurred much of the current rearch activity.
The prentation here is of necessity incomplete, becau the author is not aware of all rearch going on everywhere in the country and there is not enough space in this prentation. The overview is meant to give a general flavor of the rearch activities, and to show that a significant effort is going on in the US. The following is a list of 10 major topics in steel rearch: 1.Limit States Design for bridges
2.Monitoring of structural performance in the field
3.Design of ismically resistant connections
4.Curved girder bridges
形容雪大的成语
/doc/c0cdca1fb8f67c1cfbd6b81b.html posite columns with high-performance concrete
6.Building frames with mi-rigid joints
7.“Advanced Structural Analysis” for buildings
8.Repair and retrofit of structures
9.Steel structures with high-performance steels
10.Cold-formed steel structures
The next parts of this paper will give brief discussions on some of the topics. Several topics will then be elaborated in more detail. The paper will conclude with a look toward the future of structural steel rearch.
2.Rearch on steel bridges
芹菜的功效The American Association of State Transportation and Highway Officials (AASHTO) is the authority that promulgates design standards for bridges in the US. In 1994 it has issued a new design specification which is a Limit States Design standard that is bad on the principles of reliability theory. A great deal of work went into the development of this code in the past decade, especially on
calibration and on the probabilistic evaluation of the previous specification. The code is now being implemented in the design office, together with the introduction of the Systeme Internationale units. Many questions remain open about the new method of design, and there are many new projects that deal with the reliability studies of the bridge as a system. One such current project is a study to develop probabilistic models, load factors, and rational load-combination rules for the combined effects of liveload and wind; live-load and earthquake; live-load, wind and ship collision; and ship collision, wind, and scour. There are also many field measurements of bridge behavior, using modern tools of inspection and monitoring such as acoustic emission techniques and other means of non-destructive evaluation. Such fieldwork necessitates parallel studies in the laboratory, and the evolution of ever more sophisticated high-technology data transmission methods.
America has an aging steel bridge population and many problems ari from fatigue and corrosion. Fatigue studies on full-scale components of the Williamsburg Bridge in New York have recently been completed at Lehigh University. A probabilistic AASHTO bridge evaluation regulation has been in effect since 1989, and it is employed to asss the future uful life of structures using rational methods that include field obrvation and measurement together with probabilistic analysis. Such an activity also fosters additional rearch becau many issues are still unresolved. One such area
is the study of the shakedown of shear connectors in composite bridges. This work has been recently completed at the University of Missouri.
In addition to fatigue and corrosion, the major danger to bridges is the possibility of earthquake induced damage. This also has spawned many rearch projects on the repair and retrofit of steel superstructures and the supporting concrete piers. Many bridges in the country are being strengthened for earthquake resistance.
One area that is receiving much rearch attention is the strengthening of concrete piers by “jacketing” them by sheets of high-performance reinforced plastic.
The previously described rearch deals mainly with the behavior of existing structures and the design of new bridges. However, there is also a vigorous activity on novel bridge systems. This rearch is centered on the application of high-performance steels for the design of innovative plate and box-girder bridges, such as corrugated webs, combinations of open and clod shapes, and longer spans for truss bridges. It should be mentioned here that, in addition to work on steel bridges, there is also very active rearch going on in the study of the behavior of prestresd concrete girders made from very high strength concrete. The performance and design of smaller bridges usin
g pultruded high-performance plastic composite members is also being studied extensively at prent. New continuous bridge systems with steelconcrete composite gments in both the positive moment and the negative moment regions are being considered. Several rearchers have developed strong capabilities to model the three-dimensional non-linear behavior of individual plate girders, and many studies are being performed on the buckling and post-buckling characteristics of such structures. Companion experimental studies are also made, especially on members built from high-performance steels. A full-scale bridge of such steel has been designed, and will soon be constructed and then tested under traffic loading. Rearch efforts are also underway on the study of the fatigue of large expansion joint elements and on the fatigue of highway sign structures.
西安南湖The final subject to be mentioned is the resurgence of studies of composite steelconcrete horizontally curved steel girder bridges. A just completed project at the University of Minnesota monitored the stress and the deflections in a skewed and curved bridge during all phas of construction, starting from the fabrication yard to the completed bridge. Excellent correlation was found to exist between the measured stress and deformations and the calculated values. The stress and deflections during construction were found to be relatively small, that is, the construction process did not cau vere trauma to the system. The bridge has now been tested under rvice loading, using fully loaded gravel trucks, for two years, and it will continue to
be studied for further years to measure changes in performance under rvice over time. A major testing project is being conducted at the Federal Highway Administration laboratory in Washington, DC, where a half-scale curved composite girder bridge is currently being tested to determine its limit states. The test-bridge was designed to act as its own test-frame, where various portions can be replaced after testing. Multiple flexure tests, shear tests, and tests under combined bending and shear, are thus performed with realistic end-conditions and restraints. The experiments are also modeled by finite element analysis to check conformance between reality and prediction. Finally design standards will be evolved from the knowledge gained. This last project is the largest bridge rearch project in the USA at the prent time.
From the discussion above it can be en that even though there is no large expansion of the nation’s highway and railr oad
system, there is extensive work going on in bridge rearch. The major challenge facing both the rearcher and the transportation engineer is the maintenance of a healthy but aging system, eing to its gradual replacement while keeping it safe and rviceable.
3.Rearch on steel members and frames
There are many rearch studies on the strength and behavior of steel building structures. The most important of the have to do with the behavior and design of steel structures under vere ismic events. This topic will be discusd later in this paper. The most significant trends of the non-ismic rearch are the following: ?“Advanced” methods of structural analysis and design are actively studied at many Universities, notably at Cornell, Purdue, Stanford, and Georgia Tech Universities. Such analysis methods are meant to determine the load-deformation behavior of frames up to and beyond failure, including inelastic behavior, force redistribution, plastic hinge formation, cond-order effects and frame instability. When the methods are fully operational, the structure will not have to undergo a member check, becau the finite element analysis of the frame automatically performs this job. In addition to the rearch on the best approaches to do this advanced analysis, there are also many studies on simplifications that can be easily
utilized in the design office while still maintaining the advantages of a more complex analysis. The advanced analysis method is well developed for in-plane behavior, but much work is yet to be done on the cas where bi-axial bending or lateraltorsional buckling must be considered. Some success have been achieved, but the rearch is far from complete. Another aspect of the frame behavior work is the study of the frames with mirigid joints. The American Institute of Steel constru
ction (AISC) has published design methods for office u. Current rearch is concentrating on the behavior of such structures under ismic loading. It appears that it is possible to u such frames in some ismic situations, that is, frames under about 8 to 10 stories in height under moderate earthquake loads. The future of structures with mi-rigid frames looks very promising, mainly becau of the efforts of rearchers such as Leon at Georgia Tech University , and many others. Rearch on member behavior is concerned with studying the buckling and postbuckling behavior of compact angle and wide-flange beam members by advanced commercial finite element programs. Such rearch is going back to examine the assumptions made in the 1950s and 1960s when the plastic design compactness and bracing requirements were first formulated on a mi-empirical basis. The non-linear finite element computations permit the “re-testing” of the old experiments a nd the performing of new computer experiments to study new types of members and new types of steels. White of Georgia Tech is one of the pioneers in this work. Some current rearch at the US military Academy and at the University of Minnesota by Earls is discusd later in this report. The significance of this type of rearch is that the phenomena of extreme yielding and distortion can be efficiently examined in parameter studies performed on the computer. The computer results can be verified with old experiments, or a small number of new experiments. The studies show a good prospect for new insights into old problems that heretofore were never fully solved.
专题摄影
4.Rearch on cold-formed steel structures
Next to ismic work, the most active part of rearch in the US is on cold-formed steel structures. The reason for this is that the supporting industry is expanding, especially in the area of individual family dwellings. As the cost of wood goes up, steel framed hous become more and more economical. The intellectual problems of thin-walled structures buckling in multiple modes under very large deformations have attracted some of the best minds in stability rearch. As a conquence, many new problems have been solved: complex member stiffening systems, stability and bracing of C and Z beams, composite slabs, perforated columns, standing-am roof systems, bracing and stability of beams with very complicated shapes, cold-formed members with steels of high yield stress-to-tensile strength ratio, and many other interesting applications. The American Iron and Steel Institute (AISI) has issued a new expanded standard in 1996 that brought many of the rearch results into the hands of the designer.
5.Rearch on steel-concrete composite structures颜体
Almost all structural steel bridges and buildings in the US are built with composite beams or girders. In contrast, very few columns are built as composite members. The area of composite column rear
ch is very active prently to fill up the gap of technical information on the behavior of such members. The subject of steel tubes filled with high-strength concrete is especially active. One of the aims of rearch performed by Hajjar at the University of Minnesota is to develop a fundamental understanding of the various interacting phenomena that occur in concrete-filled columns and beam-columns under monotonic and cyclic load. The other aim is to obtain a basic understanding of the behavior of connections of wide-flange beams to concrete filled tubes.
Other major rearch work concerns the behavior and design of built-up composite wide-flange bridge girders under both positive and negative bending. This work is performed by Frank at the University of Texas at Austin and by White of Georgia Tech, and it involves extensive studies of the buckling and post-buckling of thin stiffened webs. Already mentioned is the examination of the shakedown of composite bridges. The question to be answered is whether a composite bridge
girder los composite action under repeated cycles of loads which are greater than the elastic limit load and less than the plastic mechanism load. A new study has been initiated at the University of Minnesota on the interaction between a mi-rigid steel frame system and a concrete shear wall connected by stud shear connectors.
6.Rearch on connections
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Connection rearch continues to interest rearchers becau of the great variety of joint types. The majority of the connection work is currently related to the ismic problems that will be discusd in the next ction of this paper. The most interest in non-ismic connections is the characterization of the monotonic moment-rotation behavior of various types of mi-rigid joints.
7.Rearch on structures and connections subject to ismic forces
The most compelling driving force for the prent structural steel rearch effort in the US was the January 17, 1994 earthquake in Northridge, California, North of Los Angeles. The major problem for steel structures was the extensive failure of prequalified welded rigid joints by brittle fracture. In over 150 buildings of one to 26 stories high there were over a thousand fractured joints. The buildings did not collap, nor did they show any external signs of distress, and there were no human injuries or deaths. A typical joint is shown in Fig. 1.
In this connection the flanges of the beams are welded to the flanges of the column by full-penetration butt welds. The webs are bolted to the beams and welded to the columns. The characteristic features of this type of connection are the backing bars at the bottom of the beam flange, and the cope-holes left open to facilitate the field welding of the beam flanges. Fractures occ
urred in the welds, in the beam flanges, and/or in the column flanges, sometimes penetrating into the webs.
Once the problem was discovered veral large rearch projects were initiated at various university laboratories, such as The University of California at San Diego, the University of Washington in Seattle, the University of Texas at Austin, Lehigh University at Bethlehem, Pennsylvania, and at other places. The US Government under the leadership of the Federal Emergency Management Agency (FEMA) instituted a major national rearch effort. The needed work was deemed so extensive that no single rearch agency could hope to cope with it. Conquently three California groups formed a consortium which manages the work:
1.Structural Engineering Association of California
2.Applied Technology Council
3.California Universities for Rearch in Earthquake Engineering
The first letters in the name of each agency were combined to form the acronym SAC, which is the name of the joint venture that manages the rearch. We shall read much from this agency as the results of the massive amounts of rearch performed under its aegis are being published in the next few years.
The goals of the program are to develop reliable, practical and cost-effective guidelines for the identification and inspection of at-risk steel moment frame buildings, the repair or upgrading of damaged buildings, the design of new construction, and the rehabilitation of undamaged buildings. As can be en, the scope far exceeds the narrow look at the connections only.
The first pha of the rearch was completed at the end of 1996, and its main aim was to arrive at interim guidelines so that design work could proceed. It consisted of the following components:
A state-of-the-art asssment of knowledge on steel connections
A survey of building damage
The evaluation of ground motion
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Detailed building analys and ca studies
A preliminary experimental program
Professional training and quality assurance programs
Publishing of the Interim Design Guidelines
A number of reports were issued in this first pha of the work. A partial list of the is appended at the end of this paper.
During the first pha of the SAC project a ries of full-scale connection tests under static and, occasionally, dynamic cyclic tests were performed. Tests were of pre-Northridge-type connections (that is, connections as they existed at the time of the earthquake), of repaired and upgraded details,
and of new recommended connection details. A schematic view of the testing program is illustrated in Fig. 2. Some recommended strategies for new design are schematically shown in Fig. 3.
The following possible caus, and their combinations, were found to have contributed to the connection failures: Inadequate workmanship in the field welds
Insufficient notch-toughness of the weld metal
