外文翻譯-近期美國在鋼結構和鋼筋混凝土結構研究和設計方面的發(fā)展

1、<p>　　中文5370字，3300單詞，17900英文字符</p><p>　　出處：Galambos T V. Recent research and design developments in steel and composite steel–concrete structures in USA[J]. Journal of Constructional Steel Research, 200

2、0, 55(s 1–3):289-303.</p><p><b>　　外 文 譯 文</b></p><p>　　學 院 建筑工程學院 </p><p>　　專業(yè)班級 土木工程 </p><p>　　學生姓名

3、 </p><p>　　學 號 </p><p>　　Recent Research and Design Developments in Steel and Composite Steel-concrete Structures in USA</p><p>　　T

4、he paper will conclude with a look toward the future of structural steel research.</p><p>　　1. Research on steel bridges</p><p>　　The American Association of State Transportation and Highway Off

5、icials (AASTHO) 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 based on the principles of reliab

6、ility 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 impleme<

7、/p><p>　　America has an aging steel bridge population and many problems arise from fatigue and corrosion. Fatigue studies on full-scale components of the Williamsburg Bridge in New York have recently been compl

8、eted at Lehigh University. A probabilistic AASTHO bridge evaluation regulation has been in effect since 1989, and it is employed to assess the future useful life of structures using rational methods that include field ob

9、servation and measurement together with probabilistic analysis. Such an activit</p><p>　　In addition to fatigue and corrosion, the major danger to bridges is the possibility of earthquake induced damage. Thi

10、s also has spawned many research 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 th

11、at is receiving much research attention is the strengthening of concrete piers by "jacketing" them by sheets of high-performance reinforced plastic.</p><p>　　The previously described research deals

12、 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 research is centered on the application of high-performance steels

13、for the design of innovative plate and box-girder bridges, such as corrugated webs, combinations of open and closed shapes, and longer spans for truss bridges. It should be mentioned here that, in addition to work on ste

14、el bridges, there is </p><p>　　The final subject to be mentioned is the resurgence of studies of composite steel concrete horizontally curved steel girder bridges. A just completed project at the University

15、of Minnesota monitored the stresses and the deflections in a skewed and curved bridge during all phases of construction, starting from the fabrication yard to the completed bridge.~ Excellent correlation was found to ex

16、ist between the measured stresses and deformations and the calculated values. The stresses and deflectio</p><p>　　From the discussion above it can be seen that even though there is no large expansion of the

17、nation's highway and railroad system, there is extensive work going on in bridge research. The major challenge facing both the researcher and the transportation engineer is the maintenance of a healthy but aging syst

18、em, seeing to its gradual replacement while keeping it safe and serviceable.</p><p>　　2. Research on steel members and frames</p><p>　　There are many research studies on the strength and behavio

19、r of steel building structures. The most important of these have to do with the behavior and design of steel structures under severe seismic events. This topic will be discussed later in this paper. The most significant

20、trends of the non-seismic research are the following:</p><p>　　"Advanced" methods of structural analysis and design are actively studied at many Universities, notably at Cornell, Purdue, Stanford,

21、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, s

22、econd-order effects and frame instability. When these methods are fully operational, the structure will not have to undergo a member check, becaus</p><p>　　Another aspect of the frame behavior work is the st

23、udy of the frames with semirigid joints. The American Institute of Steel Construction (AISC) has published design methods for office use. Current research is concentrating on the behavior of such structures under seismic

24、 loading. It appears that it is possible to use such frames in some seismic situations, that is, frames under about 8 to 10 stories in height under moderate earthquake loads. The future of structures with semi-rigid fram

25、es looks </p><p>　　Research on member behavior is concerned with studying the buckling and post buckling behavior of compact angle and wide-flange beam members by advanced commercial finite element programs.

26、 Such research 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 semi-empirical basis. The non-linear finite ele

27、ment computations permit the "re-testing" of the old experiments and the performing of new c</p><p>　　3. Research on cold-formed steel structures</p><p>　　Next to seismic work, the mos

28、t active part of research 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

29、, steel framed houses 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 resea

30、rch. As a consequence, many new</p><p>　　4. Research on steel-concrete composite structures</p><p>　　Almost all structural steel bridges and buildings in the US are built with composite beams or

31、 girders. In contrast, very few columns are built as composite members. The area of composite Column research is very active presently to fill up the gap of technical information on the behavior of such members. The subj

32、ect of steel tubes filled with high-strength concrete is especially active. One of the aims of research performed by Hajjar at the University of Minnesota is to develop a fundamental unde</p><p>　　Other majo

33、r research 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 Whit

34、e 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 wh

35、ether a composite bridge girder loses composite ac</p><p>　　5. Research on connections</p><p>　　Connection research continues to interest researchers because of the great variety of joint types.

36、 The majority of the connection work is currently related to the seismic problems that will be discussed in the next section of this paper. The most interest in non-seismic connections is the characterization of the mono

37、tonic moment-rotation behavior of various types of semi-rigid joints. </p><p>　　6. Research on structures and connections subject to seismic forces</p><p>　　The most compelling driving force for

38、 the present structural steel research 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 prequalifie

39、d 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 collapse, nor did they show any external signs of distress, an

40、d there were no human i</p><p>　　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

41、. 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 occurred in the

42、 welds, in the beam flanges, and/or in the column flanges, sometimes penetrating into the webs.</p><p>　　Once the problem was discovered several large research projects were initiated at various university l

43、aboratories, 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 Govern

44、ment under the leadership of the Federal Emergency Management Agency (FEMA) instituted a major national research effort. The needed work was deemed so extensive that no single re</p><p>　　(1) Structural Engi

45、neering Association of California.</p><p>　　(2) Applied Technology Council.</p><p>　　(3) California Universities for Research in Earthquake Engineering.</p><p>　　The first letters i

46、n the name of each agency were combined to form the acronym SAC, which is the name of the joint venture that manages the research. We shall read much from this agency as the results of the massive amounts of research per

47、formed under its aegis are being published in the next few years. </p><p>　　The goals of the program are to develop reliable, practical and cost-effective guidelines for the identification and inspection of

48、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 seen, the scope far exceeds the narrow look at

49、 the connections only. The first phase of the research was completed at the end of 1996, and its main aim was to arrive at interim guidelines so that</p><p>　　~ A state-of-the-art assessment of knowledge on

50、steel connections.</p><p>　　~ A survey of building damage.</p><p>　　~ The evaluation of ground motion.</p><p>　　~ Detailed building analyses and case studies.</p><p>　　

51、~ A preliminary experimental program.</p><p>　　~ Professional training and quality assurance programs.</p><p>　　~ Publishing of the Interim Design Guidelines.</p><p>　　A number of r

52、eports were issued in this first phase of the work. A partial list of these is appended at the end of this paper.</p><p>　　During the first phase of the SAC project a series of full-scale connection tests

53、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

54、, and of new recommended connection details. A schematic view of the testing program is illustrated in Fig. 2.2.2 Some recommended strategies for new design are schematically shown in Fig</p><p>　　

55、Fig. 2.2.3 some recommended improvements in the interim guidelines</p><p>　　The following possible causes, and their combinations, were found to have contributed to tile connection failures:</p><

56、;p>　　~ Inadequate workmanship in the field welds.</p><p>　　~ Insufficient notch-toughness of the weld metal.</p><p>　　~ Stress raisers caused by the backing bars.</p><p>　　~ Lack

57、 of complete fusion near the backing bar.</p><p>　　~ Weld bead sizes were too big.</p><p>　　~ Slag inclusion in the welds.</p><p>　　While many of the failures can be directly attrib

58、uted to the welding and the material of the joints, there are more serious questions relative to the structural system that had evolved over the years mainly based on economic considerations.' The structural syste

59、m used relatively few rigid-frames of heavy members that were designed to absorb the seismic forces for large parts of the structure. These few lateral-force resistant frames provide insufficient redundancy. More rigid-f

60、rames with smal</p><p>　　As can be seen, there are many possible reasons for this massive failure rate, and there is blame to go around for everyone. No doubt, the discussion about why and how the joints fai

61、led will go on for many more years. The structural system just did not measure up to demands that were more severe than expected. What should be kept in mind, however, is that no structure collapsed or caused even superf

62、icial nonstructural damage, and no person was injured or killed. In the strictest sense the struct</p><p>　　7. Future directions of structural steel research and conclusion</p><p>　　The future h

63、olds many challenges for structural steel research. The ongoing work necessitated by the two recent earthquakes that most affected conventional design methods, namely, the Northridge earthquake in the US and the Kobe

64、 earthquake in Japan, will continue well into the first decade of the next Century. It is very likely that future disasters of this type will bring yet other problems to the steel research community. There is a profound

65、change in the philosophy of design for disasters</p><p>　　Another major challenge will be the emergence of many new materials such as high-performance concrete and plastic composite structures. Steel structu

66、res will continually have to face the problem of having to demonstrate viability in the marketplace. This can only be accomplished by more innovative research. Furthermore, the new comprehensive limit-states design codes

67、 which are being implemented worldwide, need research to back up the assumptions used in the theories.</p><p>　　Specifically, the following list highlights some of the needed research in steel structures: &l

68、t;/p><p>　　Systems reliability tools have been developed to a high degree of sophistication. These tools should be applied to the studies of bridge and building structures to define the optimal locations of mon

69、itoring instruments, to assess the condition and the remaining life of structures, and to intelligently design economic repair and retrofit operations.New developments in instrumentation, data transfer and large-scale co

70、mputation will enable researchers to know more about the response of structures u</p><p>　　The state of knowledge about the strength of structures is well above the knowledge about serviceability and durabil

71、ity. Research is needed on detecting and preventing damage in service and from deterioration.</p><p>　　The areas of fatigue and fracture mechanics on the one hand, and the fields of structural stability on t

72、he other hand, should converge into a more Unified conceptual entity.</p><p>　　The problems resulting from the combination of inelastic stability and low-cycle fatigue in connections subject to severe cyclic

73、 loads due to seismic action will need to be solved.</p><p>　　The performance of members, connections and connectors (e.g., shear connectors) under severe cyclic and dynamic loading requires extensive new re

74、search, including shakedown behavior. </p><p>　　The list could go on, but one should never be too dogmatic about the future of such a highly creative activity as research. Nature, society and economics will

75、provide sufficient challenges for the future generation of structural engineers.</p><p>　　本文出自：https://www.researchgate.net</p><p>　　近期美國在鋼結構和鋼筋混凝土結構研究和設計方面的發(fā)展</p><p>　　這篇文章將總結對鋼結構的

76、研究展望. </p><p>　　1.鋼結構橋梁的研究</p><p>　　美國國家運輸和公路官員協(xié)會(AASTH0)是為美國橋梁發(fā)布設計標準的權威。1994年它發(fā)行了一個新的設計規(guī)范，這是一個限定性規(guī)范，它是以可靠性理論為基礎而建立的。在過去10年中的大量工作促 使了該規(guī)范的發(fā)展，尤其是在對原有規(guī)范的校準和概率性評估方面。連同國際單位制的引入，目前該規(guī)范已經應用于各個設計事務所。這種新

77、的設計方法還存在許多問題，對橋梁擎體系統(tǒng)的可靠性研究還有很多新的課題。一個目前的課題就是研究并發(fā)展概率模型、荷載系數(shù)以及合理的荷載組合法則，以處理活載和風載；活載和地震；活載、風和船只碰撞；船只碰撞、風和沖刷作用這些共同作用對橋的影響。此外，還通過利用現(xiàn)代監(jiān)控工具，例如聲傳播技術和其他非破壞性測試方法，對橋體進行現(xiàn)場測量。這些現(xiàn)場工作不僅需要并行的試驗室研究相配合，還需要快速發(fā)展高科技數(shù)據傳輸方法。</p><p&g

78、t;　　美國有數(shù)量眾多的年代久遠的鋼橋，許多問題是由疲累和腐蝕引起的。最近里海大學完成了對紐約Williamsburg大橋足尺構件的抗疲勞研究。AASTHO的橋體概率評估規(guī)定自1989年起開始生效，它通過結合現(xiàn)場監(jiān)測和概率分析等合理方法對結構未來使用時間進行評估。由于許多問題還未得到解決，這樣的活動同樣促進了進一步的研究工作。其中之一是對混合結構橋受剪連接部件強制破壞的研究。這項工作最近已經在密蘇里大學完成了。 </p>

79、<p>　　除了疲累和腐蝕，橋梁的主要危險是地震引起的潛在的破壞。這也引發(fā)了對鋼橋上部構造和混凝土橋墩的修理和新式設計的諸多研究。國內的許多橋梁正在進行加固以抵抗地震。其中一個引起廣泛研究興趣的領域是用一層層的高性能加固塑料“圍裹”住混凝土柱，以增強其性能。</p><p>　　前述的研究工作主要是針對現(xiàn)有結構的性能和新橋梁的設計。然而，對新穎橋梁結構的研究也充滿活力。這方面的研究主要圍繞將高強鋼應

80、用于新型板式支架和箱式支架橋梁，例如波形網格、開口和封閉結合的形式及更長跨度的桁架橋。在此必須指出，除了對鋼橋的工作，還有一個非常活躍的研究領域，那就是對超高強混凝土預應力梁性能的研究。目前，對使用高性能塑性混合元件的小型橋梁的性能和設計也有廣泛研究。對使用鋼筋混凝土分段的連續(xù)橋體系，在正彎矩和負彎矩區(qū)域都得到了考慮。一些研究者發(fā)展了高強模型來模擬獨立板梁的三維非線性表現(xiàn)，并且對這種結構彎曲前及彎曲后的性能進行了許多研究。此外還進行了伴

81、隨試驗，特別是針對高性能鋼建造的部件。一座實物大小使用這種鋼材的橋已經被設計出來，并且很快就將建造，然后進行交通荷載測試。對于大膨脹連接元件及高速公路標志結構的疲勞研究也在進行中。</p><p>　　最后要提到的是鋼筋混凝土水平彎曲鋼架橋研究的興起。明尼蘇達大學剛完成的一個項目，他們對一座歪斜彎曲的橋梁在施工各個階段——從預制工場到建造完畢——的應力和變形進行了監(jiān)控。測量到的應力和變形與計算值吻合得相當好。施工

82、階段的應力和變形相對很小，這表明施工過程對橋系統(tǒng)并不產生嚴重損壞。目前這座橋正在接受使用荷載試驗，通過滿載沙礫的卡車施加荷載，這個過程要持續(xù)兩年，之后三將繼續(xù)對橋在使用荷載長期作用下性能的變化進行研究。一個主要的測試項目已經在位于華盛頓的聯(lián)邦高速公路管理局試驗室展開，一座1／2比例的彎曲混合梁橋目前正在測試以確定其極限狀態(tài)。這座試驗橋被設計為自身的試驗框架，測試后不同的部件可以被更換。在真實邊界條件和約束下進行了各種柔性試驗、剪切試驗和

83、彎剪共同作用試驗。還通過有限元分析給這些試驗建模，以檢查真實值和預測值的一致性。根據獲得的認識來完善最終的設計規(guī)范。這是目前美國最大的橋梁研究項目。</p><p>　　從上述討論可以發(fā)現(xiàn)，盡管全國的高速公路和鐵路系統(tǒng)并未大規(guī)模擴張，但在橋梁領域卻開展了廣泛研究。對于研究人員和交通工程師而言，主要的挑戰(zhàn)是對雖然老化但仍可正常使用的結構的維護，應在保持其安全和可用性的前提下考慮逐步替換它們。</p>

84、<p>　　2．鋼構件和鋼框架結構的研究</p><p>　　目前有很多關于鋼結構建筑的強度和性能的研究。其中最重要的與劇烈地震時鋼結構的性能和設計有關。這個話題將在接下來的內容中討論。非地震領域中最重要的研究趨勢如下。 許多大學中都展開了對結構分析與設計中的“先進”方法的積極研究，最著名的如康納爾大學、普度大學、斯坦福大學和喬治亞理工大學。這些分析方法是用于決定結構在即將失效或失效后荷載——變形

85、之間的性能，包括非彈性性狀、內力重分布、塑性鉸的形成、二級影響和框架失穩(wěn)。當這些方法完全運作時，結構無需再經過元件校核，因為對框架的有限元分析自動完成了這個工作。除了對應用這種高級分析的最佳方法的研究外，還有很多關于簡化方法的研究工作，這些簡化方法可以在設計事務所中輕易地應用，同時還保持了復雜分析的優(yōu)勢。對于平面內的性能，這種高級分析方法已發(fā)展得很完善，但對于考慮雙軸向彎曲或水平扭轉翹曲的情形還需進一步研究。目前雖已取得了一定成果，但研

86、究還遠末完成。</p><p>　　框架行為另外一方面的工作就是對有半剛性節(jié)點框架的研究。美國鋼結構學會(AISC)已經發(fā)布了用于事務所的設計方法。目前的研究主要集中于地震荷載下這類結構的行為。有結果表明在地震情況下可以使用這類框架，即8—10層中等地震荷載作用下的建筑。使用半剛性連接框架的結構前景廣闊，這主要得益于像喬治亞理工大學的Leon及其他研究者的努力。</p><p>　　對構件

87、性能的研究主要是應用高級商業(yè)有限元軟件對密集角和寬翼緣梁構件的分析。這種研究是對20世紀50年代和60年代的一些假設的檢驗，那時塑性設計的簡潔性和對支撐的要求是基于半經驗的基礎形成的。非線性有限元計算允許對已有試驗進行“重新測試”，并對新型元件和新型鋼種進行新的計算機試驗。喬治亞理工大學的懷特是這方面的先鋒之一。這篇文章后邊還將提及美國軍事學院和明尼蘇達大學的Earls目前進行的研究工作。此類研究的重要性在于：可以通過在計算機上進行參數(shù)

88、研究對極端屈服和變形現(xiàn)象進行有效的檢驗。計算機所得的結果可以通過原有試驗和少量新試驗來進行校核。這些研究對那些至今未得到完全解決的老問題帶來了希望。</p><p>　　3．對冷加工鋼結構的研究</p><p>　　在地震之后，目前美國最活躍的研究領域就是冷加工鋼結構。原因是相關支柱產業(yè)正在擴大，特別是在獨立家庭住宅領域。隨著木材價格上漲，鋼結構房屋顯得越來越經濟。多模式大變形情況時薄壁結

89、構的翹曲問題引起了穩(wěn)定研究領域種的一些最優(yōu)秀人才的關注。由此，許多問題得到了解決：如復雜單元增強結構，C型和Z型梁的穩(wěn)定性及支撐，混合板，穿孔柱，穩(wěn)定焊接屋頂系統(tǒng)，復雜形狀梁的穩(wěn)定性及支撐，使用高應力高抗拉比鋼材的冷加工元件，及其他許多有趣的應用。美國鋼鐵學會(AISl)在1996年發(fā)布了新的擴張標準，使得上述許多研究結果能被設計人員所利用。</p><p>　　4．鋼筋混凝土混合結構的研究</p>

90、<p>　　美國幾乎所有的結構性鋼橋和建筑都是使用梁或桁架混合建造的。相反，很少有柱是混合構件。當前對混合柱的研究非?；钴S，這將填補此類構件技術信息的空缺。鋼管中填充高強混凝土的課題研究尤其活躍。明尼蘇達大學的HaUar對此進行了研究，他的一個研究目標就是對單調荷載和循環(huán)荷載下混凝土填充柱和梁柱發(fā)生的各種相互作用建立一個基本的了解。另一個目標是獲得對寬翼梁與混凝土填充管連接的性能的基本認識。</p><p

91、>　　其他主要的研究工作涉及同時承受正負彎矩作用的寬翼橋桁架裝配的性能和設計。該工作由得克薩斯大學的費蘭克和喬治亞理工的懷特展開，工作包括了對薄壁加勁腹板翹曲和翹曲后深入廣泛的研究。前邊提到了對混合橋強制破壞的檢驗。需要解決的問題是在大于彈性極限荷載而小于塑性機理荷載的循環(huán)荷載作用下，是否橋桁架會失去混合作用的能力。一項新的研究已經在明尼蘇達大學展開，它對由螺栓剪切連接的半剛性鋼架系統(tǒng)和混凝土剪力墻間的相互作用進行了研究。<

92、/p><p><b>　　5，對連接的研究</b></p><p>　　連接形式的多樣性使研究者對連接問題的研究很感興趣。目前大部分的連接工作主要與本文下一節(jié)要討論的地震問題相關。對非地震連接的最大興趣在于各類型的半剛性連接單一彎曲扭轉特性的研究。</p><p>　　6．地震力作用下結構及其連接的研究</p><p>　　

93、目前美國對結構性鋼研究所作的努力主要動力來源于1994年1月17日Northridge，加利福尼亞，洛杉磯北部的地震。鋼結構的主要問題是滿足條件的剛性連接脆性破裂導致的結構大規(guī)模失效。在超過150幢1～26層的建筑中有上千個破壞的連接部分。建筑物并未倒塌，它們也沒有出現(xiàn)任何外部龜裂，此外也沒有人員傷亡。一個典型的連接如圖2．2，1所示。</p><p>　　在該連接中，梁翼緣通過完全對接焊透與柱焊接。腹板與梁拴接

94、，與柱焊接。這類連接的特征是梁翼緣底部的支撐鋼筋，以及為方便梁翼緣焊接施工留下的處理孔。出現(xiàn)在焊縫中、梁翼緣中及柱翼緣上的裂縫有時會進入腹板。</p><p>　　這個問題被發(fā)現(xiàn)后，許多大型研究項目在各大學試驗室展開，如加利福尼亞大學的圣·地亞哥分校、西雅圖的華盛頓大學、奧斯汀的得克薩斯大學、賓夕法尼亞的里海大學伯利恒分校，等等。在聯(lián)邦應急管理局(FEMA)指導下美國政府展開了一個全國性的主要研究工作。

95、這項工作被認為是非常龐大，沒有任何獨立研究機構能夠單獨完成。從而三個加利福尼亞團體成立了一個協(xié)會以管理這項工作，它們是：</p><p>　　(1)加利福尼亞結構工程協(xié)會。</p><p>　　(2)應用科技理事會。</p><p>　　(3)加利福尼亞大學地震工程研究所。</p><p>　　三個機構名稱的首字母形成了縮寫詞SAC，這就是該

96、聯(lián)合協(xié)會的名稱。在該協(xié)會的支持下，大量的研究工作得以開展，并且在接下來的幾年中發(fā)表了很多成果。</p><p>　　這個項目的目標是建立可靠、可行及經濟的指導原則，以識別和檢測危險鋼結構建筑，維修和升級破壞建筑，設計新建筑結構，對未破壞建筑的翻新。很明顯，它的影響范圍遠遠超出了連接問題。</p><p>　　研究的第一階段在1996年底完成，它的主要目標是達成一個過渡性的指導原則，以使設計

97、工作得以繼續(xù)。它包括了以下內容：</p><p>　　·在目前技術水平下對鋼連接知識的評估。</p><p>　　·對建筑破壞的調查。</p><p>　　·對地面運動的評估。</p><p>　　·詳細的建筑分析和案例研究。</p><p><b>　　·初

98、步試驗項目。</b></p><p>　　·專業(yè)訓練和質量保證項目。</p><p>　　·《臨時設計指導原則》的發(fā)表。</p><p>　　在第一階段工作中發(fā)表了許多報告。這篇文章末尾列舉了其中的一部分。</p><p>　　在SAC項目的第一階段，進行了一系列靜載或有時循環(huán)動載作用下的足尺連接試驗。有關于先

99、Northridge型的連接(即地震發(fā)生時已存在的連接)，有已修復和升級的部件，還有新的建議使用的連接部件。圖2；2．2是該試驗項目示意性說明。圖2．2．3是一些建議使用的新設計策略。</p><p>　　接下來是一些導致連接失效的可能原因，可能是單獨影響，也可能是共同影響：</p><p>　　·現(xiàn)場焊接時人工的不足。</p><p>　　·焊

100、接材料刻痕硬度不足。 </p><p>　　·支撐鋼筋的應力集中發(fā)生點。</p><p>　　·載支撐鋼筋附近未焊透。</p><p><b>　　·焊頭過大。</b></p><p><b>　　·焊縫中有焊渣。</b></p><

101、p>　　許多失效可直接歸咎于焊接或連接材料，但這些年來更嚴重的與結構體系相關的I司題主要是基于經濟上的考慮。結構體系采用了相對較少的重型剛性框架構件，這些構件是設計用來吸收作用于結構大部件上的地震力的。這些較少的抗水平力框架不能提供足夠的儲備。使用更多的小型構件框架可以提供一個更強更柔的結構體系。還存在一個尺寸影響：使用小型構件連接的試驗未經過足夠的試驗驗證就推向了使用大型構件連接。一個大型初始脈沖效應可能引發(fā)了動荷載，引起包含了