土木外文文獻及翻譯-建筑結構(編輯修改稿)

　

【文章內容簡介】 was taken as rad per Note 3 in [6], Table . Shear hinge load load–deformation model points C, D and E are based on Table [6], 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 moment–axial load interaction [6]: where MCE is the expected moment strength, ZRBS is the RBS plastic section modulus (in3), is the 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 the 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 pared with the bending moment, although they must be considered in design. The qualita tive distribution of internal forces 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. Inelastic static pushover analysis was carried out by applying monotonically increasing 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 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 ponent, a long transition (consequence 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 from 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 rad: Fyf was substituted for Ry?Fy [8], where Ry is used to account for the differ ence between the nominal and the expected yield strengths (Grade 50 steel, Fy=345 MPa and Ry = are used). 3. Experimental program The experimental setup for studying the behavior of a connection was based on Fig. 6(a). Using the plastic displacement dp, plastic rotation gp, and plastic story drift angle qp shown in the figure, from geometry, it follows that:And: in which d and g include the elastic ponents. Approximations as above are used for large inelastic beam deformations. The diagram in Fig. 6(a) suggest that a sub assemblage with displacements controlled in the manner shown in Fig. 6(b) can represent the inelastic behavior of a typical beam in a CGMRF. The test setup shown in Fig. 8 was constructed to develop the mechanism shown in Fig. 6(a) and (b). The axial actuators were attached to three 2438 mm 1219 mm 1219 mm (8 ft 4 ft 4 ft) RC blocks. These blocks were tensioned to the laboratory floor by means of twentyfour 32 mm diameter dywidag rods. This arrangement permitted replacement of the specimen after each test. Therefore, the force applied by the axial actuator, P, can be resolved into two or thogonal ponents, Paxial and Plateral. Since the inclination angle of the axial actuator does not exceed ?, therefore Paxial is approximately equal to P [4]. However, the lateral ponent, Plateral, causes an additional moment at the beamto column joint. If the axial actuators press the specimen, then the lateral ponents will be adding to the lateral actuator forces, while if the axial actuators pull the specimen, the Plateral will be an opposing force to the lateral actuators. When the axial actuators undergo axial actuators undergo a lateral displacement _, they cause an additional moment at the beamtocolumn joint (P△ effect). Therefore, the moment at the beamto column joint is equal to: where H is the lateral forces, L is the arm, P is the axial force and _ is the lateral displacement. Four fullscale experiments of beam column connections were conducted. The member sizes and the results of tensile coupon tests are listed in Table 2 All of the columns and beams were of A572 Grade 50 steel (Fy MPa). The actual measured beam flange yield stress value was equal to 372 MPa (54 ksi), while the ultimate strength ranged from 502 MPa ( ksi) to 543 MPa ( ksi). Table 3 shows the values of the plastic moment for each specimen (based on measured tensile coupon data) at the full crosssection and at the reduced section at midlength of the RBS cutout. The specimens were designated as specimen 1 through specimen 4. Test specimens details are shown in Fig. 9 through Fig. 12. The following features were utilized in the design of the beam–column connection: The use of RBS in beam flanges. A circular cutout was provided, as illustr ated in Figs. 11 and 12. For all specimens, 30% of the beam flange width was removed. The cuts were made carefully, and then ground smooth in a direct tion parallel to the beam flange to minimize notches. Use of a fully welded web connection. The connection between the beam web and the column flange was made with a plete joint peration groove weld (CJP). All CJP welds were performed according to AWS Structural Welding Code Use of two side plates welded with CJP to exterior sides of