钢连接毕业论文外文翻译.doc

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1、外文文献翻译Steel Connections1 GeneralIn the design of a steel structural system connections are often relegated to a secondary status when compared to the selection and arrangement of the main structural elements. Connection design is easily oversimplified which can lead to, on opposite ends of the desig

2、n consideration spectrum, unsafe conditions and member inefficiencies (Thornton 1995). While the function of steel connections is fundamentally to serve as a load conduit from intersecting components of a structural system, achieving this transfer while taking into account all geometrical, strength,

3、 and serviceability considerations can prove quite complex.Ultimately a connection design will comprise connection elements (angles, structural tees, gusset plates, etc.) and a means of fastening them to the intersecting members: bolts, welds, or some combination of the two. However a clear understa

4、nding of the properties interaction, and function of every constituent element is essential to the design and application of any connection, rendering many connections anything but “typical”.Steel connections can be categorized in several ways depending on their intended.function, geometry, or metho

5、d in which they are employed. Generally, connections can be separated into tension, compression, or framing shear types, with several subsets of each.Tension connections often manifest themselves as splices or hanger types, while compression connections are generally found when splicing or anchoring

6、 columns. Framing connections refer to beam-to-column or beam-to-girder web connections. AISC (1999) defines two classifications of framing connections: partially restrained (PR), and fully restrained (FR).PR (pinned) or simple shear connections are intended to carry only the end reaction of the bea

7、m and are assumed to provide no rotational resistance, or in other words they exhibit infinite flexibility. FR and PR (moment) connections are moment resisting and, as their names indicate, refer to thepr amount of rotational resistance provided by each. FR connections possess sufficient rigidity to

8、 preserve the original angles of intersecting members during loading while developing the required strength of the intersecting beam. PR refers to the spectrum of connections offering some degree of moment resistance while allowing for connection rotation. Full PR connections can develop the full pl

9、astic moment of the connecting strength beam while at the same allowing some connection rotation. Rex and Goverdhan (2000) report that although PR buildings have potential advantages of quicker erection and reduced steel weight, they are rarely utilized due to a lack of design guidance and relevant

10、software. Alternatively, AISC (1999) allows the use of flexible moment connections, which are not technically PR connections but offer a more straightforward design.However recent work to understand the applicability and limitations of PR connections as well as to provide design recommendations coul

11、d initiate an industry wide change in attitude.1.1 Bolted Connections in TensionConnecting elements can be joined by welds, high-strength bolts, or the two used in conjunction. Shop welding efficiently produces a high-quality weld, however field welding can be awkward, expensive, and time consuming.

12、 Although ease of erection is not the only consideration in connection design, bolting offers a faster, easier erection. The majority of bolted connections utilize bolt groups loaded in shear. While the design of bolts in shear is often as simple as selecting an appropriate number of bolts to resist

13、 the beam end reaction, the design of connections in which bolts are subjected to tensile forces is complicated by a phenomenon known as prying. Prying results from the deformation of elements within the grip of a bolted connection in tension and induces additional bolt forces above those imposed by

14、 the direct tensile force. Prying action can be prevented; however, it is not always necessary to do so (AISC 1999). The treatment of prying acti on in connection design will be addressed in more detail later in this chapter.1.2 End-Plate ConnectionsThe end-plate moment connection is one example of

15、a bolted connection in which the bolts are subjected to tensile loads. End-plate connections consist of a plate shopwelded to the end of a beam and then bolted to either a column flange or another end-plate as a means of splicing beams. This type of connection consists of two main categories, flush

16、and extended (Sumner 2003). Flush end-plates terminate at the outside edges of the connecting beam flanges and all constituent bolt rows are contained within the same flanges. Alternatively, extended end-plate connections feature end-plates that extend outside the connecting beam flanges with at lea

17、st one bolt row outside the beam flanges. For end-plate connections subject to load reversals, the connection is symmetric about the beam centerline, and consequently both beam flanges are designed for tension. End-plate connections are also differentiated by the arrangement and number of bolts at t

18、he tension flange (Sumner 2003). These connections tend to be strong and stiff and this robustness allows them to be designed as either PR or FR. 1.3 T-Stub and Flange Angle ConnectionsT-stubs and flange-angles (clip-angles) can be completely bolted connections that,like end-plates, feature bolt gro

19、ups loaded in tension. While the absence of welds is certainly advantageous from an erection and quality control perspective, these PR connections generally offer less stiffness and strength than end-plates. T-stub connections consist of structural tees bolted through their web to the connecting bea

20、m flange and through their flange to the column flange. Flange-angles are structural angles that are bolted through both legs to the flanges of the intersecting beam and column. Both connections employ bolted structural angles between the beam web and column flange to carry the shear force of the co

21、nnection. FEMA (2000a) prequalifies t-stub connections for use with smaller connecting beams in high seismic regions provided the connection meets a “full strength/partial stiffness” criterion. Due to their inherently low stiffness and strength flange-angle connections are not recommended for use in

22、 high seismic areas, and may have limited applicability to low seismic regions (FEMA2000i).1.4 HSS Flange-Plate SplicesHollow Structural Sections (HSS) are commonly used as structural elements of trusses due to their light weight and high strength-to-weight ratios. Often it is necessary to splice th

23、ese sections to increase their span and the use of bolted flange plates is an attractive option to accomplish this task. This method of splicing can be applied to circular, rectangular, and square HSS sections and involves shop-welding a flange plate to the end of two sections and then bolting the f

24、lange plates together. Splicing in this manner not only allows a designer to overcome span limitations imposed by transportation and fabrication but also to change cross-sections while ensuring continuity. Flange-plate splices are generally described by the type of HSS section being spliced and the

25、number of bolts in the connection. Though this connection is not moment resisting, it is still subject to the same design considerations regarding the use of bolts in tension as the previously discussed framing connections.2 Motivation for Recent Research Concerning Bolts in TensionAfter the accepta

26、nce of high-strength bolts as viable structural fasteners by the Bolt Council in 1951, the performance of bolted moment connections in high seismic regions was not fully understood, comprehensively codified, or extremely relevant due to the perceived advantages of welds. Research in bolted connectio

27、ns focused on the prying phenomenon and its affect on different configurations of bolt rows. Beginning in the 1960s designers began to favor welded moment connections, especially in large and important structures. These welded connections appeared to offer economic, strength, and ductility advantage

28、s over their bolted counterparts (FEMA 2000e). By 1988 flange-welded, web-bolted connections were “prequalified” by the Uniform Building Code (UBC) (Malley, 2000). However, failure of welded moment connections in the 1994 Northridge earthquake in California and the 1995 Kobe earthquake in Japan serv

29、ed as industry wide catalysts to reexamine welded moment connections.2.1 SAC Joint VentureThe 1994 Northridge and 1995 Kobe earthquakes revealed brittle fractures of supposedly ductile welded connections in numerous steel buildings. Although no buildings collapsed, these failures served as the impet

30、us for a reevaluation of steel moment connections as a whole. In late 1994 three concerned entities, SEAOC, ATC, and CUREe, joined together to form the SAC Joint Venture. This organization proceeded to enlist FEMA to fund the majority of the six year, two-phase, $12 million SAC Steel Project. Phase

31、I of the project dealt with inspection, repair, and upgrade of existing vulnerable buildings as well as recommending future design changes. Phase II was a comprehensive evaluation of several bolted and welded steel moment connections including full scale connection tests of endplate, t-stub, and fla

32、nge-angle connections (FEMA, 2000i). The goal of the SAC Steel Project with respect to bolted moment connections was to evaluate their suitability for service in intermediate and high seismic zones and to present a rational design philosophy for such applications. The physical product of Phase II wa

33、s FEMAs publication of six state-ofthe- art reports and four seismic design guides to assist engineers in the design of steel moment connections. A complete understanding of the strength and deformation capacity of high-strength bolts loaded in axial tension has become significant as a result of the

34、 loss of favor of welded moment connections combined with an improved understanding of the abilities of bolted connections to accommodate large plastic rotations associated with service in high seismic regions.2.2 Increasing HSS SpansThe importance of a good understanding of the performance of high-

35、strength bolts in tension manifests itself in flange-plate splices. As previously discussed, the primary utility of HSS flange-plate splices is to increase the tube span. Fabricated member lengths can be limited by their ability to be transported. However large trusses and space frames require these

36、 sections to be spliced together. This splice can be accomplished in a couple of ways,one being a welded connection where a plate is placed along the sections axis into precut notches. However, this method requires field welding on at least one side of the splice,meaning a bolted solution would be l

37、ess time consuming. Recent work with bolted flangeplates has focused on the number and arrangement of the flange bolts (Willibald 2003,Willibald et al. 2003). Knowledge of the load-deformation properties of the tension bolts is central to developing a comprehensive connection model capable of accura

38、tely predicting the bolt forces when the connection is loaded, particularly in overload scenarios.2.3 Fully Threaded BoltsHigh-strength steel bolts (ASTM A325 and ASTM A490) are manufactured with astandard thread length dependent on the diameter of the bolt. This can lead to the specification of sev

39、eral different lengths of the same diameter bolts on a project. Acomplicated bolt schedule is susceptible to ordering and installation errors and therefore requires more supervision. Consequently the use of a single, fully threaded fastener on an entire structure could reduce costs on many fronts (O

40、wens, 1992). The use of a single fastener would provide adequate strength for all its applications as well as having enough length to accommodate the grip of all connections. While the performance of such fasteners in shear would be very similar to normal high-strength bolts, their use in tension wo

41、uld require a thorough understanding of their load-deformation capacity. For example the use of these bolts in PR moment connections would require them to offer the same acceptable strength under plastic connection deformation that their standard counterparts do. While the use of fully threaded bolt

42、s could simplify both steel design and construction, more information about their performance in tension is required.3 Heavy Hex Structural BoltsHigh-strength bolts are threaded mechanical fasteners with hexagon shaped heads used in structural steelwork to join intersecting elements. The use of bolt

43、s as fasteners was first seriously considered in the 1940s and refined over the next two decades. Bolts eventually supplanted rivets as the preferred method of fastening due to ease of installation and their ability to provide a reliable clamping force within steel connections (Kulak, 2002). In 1947

44、 the entity which is today known as the Research Council on Structural Connections (RCSC) was founded to serve as a governing body to supervise the acceptance and use of high-strength bolts. Four years later the RCSC published the first edition of its specification.Today RCSC (2004) provides guideli

45、nes for the proper use, installation, and inspection of high-strength bolts and the components required for their installation.3.1 Characterization of High-Strength BoltsRCSC (2004) references, both directly and implicitly, several specifications to completely define high-strength bolts, their compo

46、nents, and their use in structural joints.These specifications address chemical composition, manufacturing, strength, geometry,ordering, washers, and nuts. An overview of the principal bolt specifications is containedherein.3.2 Strength GradesThe current edition of the RCSC Specification recognizes

47、two primary grades of heavy hex structural bolts, ASTM A325 and ASTM A490. These grades are referred to by the American Society for Testing and Materials (ASTM) specifications which define their respective material and mechanical properties. Both grades of bolts can be specified as either Type I (me

48、dium carbon steel) or Type III (weathering steel). The two bolt grades differ fundamentally in chemical composition and this variation manifests itself for structural applications in the resulting minimum tensile strength of each grade. ASTM (2004b) specifies that A325 bolts of diameters less than o

49、r equal to 1 in. meet a minimum tensile stress of 120 ksi while diameters larger than 1 in. must be at least 105 ksi. ASTM (2004a) requires A490 bolts to meet the requirements of a minimum tensile stress of 150 ksi and a maximum tensile stress of 170 ksi. The commentary of RCSC (2004) explains this maximum limitation is imposed on A490 bolts because steels approaching 200 ksi become unacceptably brittle for use as fasteners due to their susceptibility to the presence of hydrogen. Therefore A490 bolts offer more strength than identica