土木工程建筑外文文献及翻译-英语论文.doc
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1、土木工程建筑外文文献及翻译-英语论文土木工程建筑外文文献及翻译Cyclic behavior of steel moment frameconnections under varying axial load and lateraldisplacementsAbstractThis paper discusses the cyclic behavior of four steel moment connections tested under variable axial load and lateral displacements. The beam specim- ens consiste
2、d of a reducedbeam section, wing plates and longitudinal stiffeners. The test specimens were subjected to varying axial forces and lateral displace- ments to simulate the effects on beams in a Coupled-Girder Moment-Resisting Framing system under lateral loading. The test results showed that the spec
3、im- ens responded in a ductile manner since the plastic rotations exceeded 0.03 rad without significant drop in the lateral capacity. The presence of the longitudin- al stiffener assisted in transferring the axial forces and delayed the formation of web local buckling.1. Introduction Aimed at evalua
4、ting the structural performance of reduced-beam section(RBS) connections under alternated axial loading and lateral displacement, four full-scale specimens were tested. These tests were intended to assess the performance of the moment connection design for the Moscone Center Exp- ansion under the De
5、sign Basis Earthquake (DBE) and the Maximum Considered Earthquake (MCE). Previous research conducted on RBS moment connections 1,2 showed that connections with RBS profiles can achieve rotations in excess of 0.03 rad. However, doubts have been cast on the quality of the seismic performance of these
6、connections under combined axial and lateral loading.The Moscone Center Expansion is a three-story, 71,814 m2 (773,000 ft2) structure with steel moment frames as its primary lateral force-resisting system. A three dimensional perspective illustration is shown in Fig. 1. The overall height of the bui
7、lding, at the highest point of the exhibition roof, is approxima- tely 35.36 m (116ft) above ground level. The ceiling height at the exhibition hall is 8.23 m (27 ft) , and the typical floor-to-floor height in the building is 11.43 m (37.5 ft). The building was designed as type I according to the re
8、qui- rements of the 1997 Uniform Building Code.The framing system consists of four moment frames in the EastWest direct- ion, one on either side of the stair towers, and four frames in the NorthSouth direction, one on either side of the stair and elevator cores in the east end and two at the west en
9、d of the structure 4. Because of the story height, the con- cept of the Coupled-Girder Moment-Resisting Framing System (CGMRFS) was utilized.By coupling the girders, the lateral load-resisting behavior of the moment framing system changes to one where structural overturning moments are resisted part
10、ially by an axial compressiontension couple across the girder system, rather than only by the individual flexural action of the girders. As a result, a stiffer lateral load resisting system is achieved. The vertical element that connects the girders is referred to as a coupling link. Coupling links
11、are analogous to and serve the same structural role as link beams in eccentrically braced frames. Coupling links are generally quite short, having a large shear- to-moment ratio.Under earthquake-type loading, the CGMRFS subjects its girders to wariab- ble axial forces in addition to their end moment
12、s. The axial forces in theFig. 1. Moscone Center Expansion Project in San Francisco, CAgirders result from the accumulated shear in the link.2.Analytical model of CGMRFNonlinear static pushover analysis was conducted on a typical one-bay model of the CGMRF. Fig. 2 shows the dimensions and the variou
13、s sections of the model. The link flange plates were 28.5 mm 254 mm (1 1/8 in 10 in) and the web plate was 9.5 mm 476 mm (3 /8 in 18 3/4 in). The SAP 2000 computer program was utilized in the pushover analysis 5. The frame was characterized as fully restrained(FR). FR moment frames are those frames
14、for 1170土木工程建筑外文文献及翻译which no more than 5% of the lateral deflections arise from connection deformation 6. The 5% value refers only to deflection due to beamcolumn deformation and not to frame deflections that result from column panel zone deformation 6, 9. The analysis was performed using an expect
15、ed value of the yield stress and ultimate strength. These values were equal to 372 MPa (54 ksi) and 518 MPa (75 ksi), respectively. The plastic hinges loaddeformation behavior was approximated by the generalized curve suggested by NEHRP Guidelines for the Seismic Rehabilitation of Buildings 6 as sho
16、wn in Fig. 3. y was calcu- lated based on Eqs. (5.1) and (5.2) from 6, as follows: PM hinge loaddeformation model points C, D and E are based on Table 5.4 from 6 for y was taken as 0.01 rad per Note 3 in 6, Table 5.8. Shear hinge load- loaddeformation model points C, D and E are based on Table 5.8 6
17、, Link Beam, Item a. A strain hardening slope between points B and C of 3% of the elastic slope was assumed for both models.The following relationship was used to account for momentaxial load interaction 6:where MCE is the expected moment strength, ZRBS is the RBS plastic section modulus (in3), is t
18、he expected yield strength of the material (ksi), P is the axial force in the girder (kips) and is the expected axial yield force of the RBS, equal to (kips). The ultimate flexural capacities of the beam and the link of the model are shown in Table 1.Fig. 4 shows qualitatively the distribution of th
19、e bending moment, shear force, and axial force in the CGMRF under lateral load. The shear and axial force in the beams are less significant to the response of the beams as compared with the bending moment, although they must be considered in design. The qualita- tive distribution of internal forces
20、illustrated in Fig. 5 is fundamentally the same for both elastic and inelastic ranges of behavior. The specific values of the internal forces will change as elements of the frame yield and internal for- ces are redistributed. The basic patterns illustrated in Fig. 5, however, remain the same.Inelast
21、ic static pushover analysis was carried out by applying monotonicallyincreasing lateral displacements, at the top of both columns, as shown in Fig. 6. After the four RBS have yielded simultaneously, a uniform yielding in the web and at the ends of the flanges of the vertical link will form. This is
22、the yield mechanism for the frame , with plastic hinges also forming at the base of the columns if they are fixed. The base shear versus drift angle of the model is shown in Fig. 7 . The sequence of inelastic activity in the frame is shown on the figure. An elastic component, a long transition (cons
23、equence of the beam plastic hinges being formed simultaneously) and a narrow yield plateau characterize the pushover curve. The plastic rotation capacity, qp, is defined as the total plastic rotation beyond which the connection strength starts to degrade below 80% 7. This definition is different fro
24、m that outlined in Section 9 (Appendix S) of the AISC Seismic Provisions 8, 10. Using Eq. (2) derived by Uang and Fan 7, an estimate of the RBS plastic rotation capacity was found to be 0.037 rad:Fyf was substituted for RyFy 8, where Ry is used to account for the differ- ence between the nominal and
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