土建外文翻译(编辑修改稿)

土建外文翻译(编辑修改稿)内容摘要：

n time history was scaled by appropriate factors to represent the 10/50 and 2/50 events. Scaling was done by considering the 5% damped Pseudo Spectral Acceleration (PSA) of a SDOF system with period T=1 sec. The scaling factors were determined by equating this spectral acceleration to the corresponding values prescribed in the draft Taiwan seismic code for 10/50 and 2/50 events at a hard rock site. The two resulting time histories have PGA values of and , respectively. For the purpose of frame design and for performing the pushover analysis, the total base shear needs to be distributed over the three floor levels. The force at ith floor was calculated by using the following equation: N d i i i i i i V m m F Σ 1 , (1) where i i m and are the mass and target displacement, respectively, of the ith floor, and d V is the total design base shear. The relative floor forces obtained are as follows: 1st Floor: , 2nd Floor: , and 3rd Floor: DESIGN BASE SHEAR Taiwan Design A brief description of the NCREE procedure to arrive at the design base shear is presented in this section. A detailed description of this procedure can be found elsewhere (Tsai [1]). In the first step, the frame was idealized as a MDOF system with three degrees of freedom. Modal Contribution Factors (MCF) for the three modes, as well as their modal masses and modal story drifts, were then puted. Since, for this particular frame, the contributions from the 2nd and 3rd modes (MCF = and , respectively) were insignificant pared to the contribution from the 1st mode (MCF = ) (Tsai [1]), only the 1st mode was considered for design purposes. Thus, the three floor displacements of the 1st mode were used to obtain an effective system displacement eff associated with the modal target roof drift. In the next step, the ductility demand for the 1st mode of the frame was puted. Because 80% of the seismic force was to be carried by the braced frame, yield drift of the effective system was puted based on the drift at the point of brace yielding and increased by 25% to account for the contribution from the moment frame. From the target maximum story drifts, ductility demand for each story was calculated and a simple average was taken as the effective ductility demand for the system. Using this ductility demand, and from the effective target displacement eff , the effective time period of the system was obtained from the inelastic displacement spectrum of the ground motion considered. Corresponding effective stiffness eff K value of the system was puted from this time period. Finally, the base shear required at the point of target drift was puted by simply multiplying eff K by eff . This ultimate base shear was reduced to the yield base shear by assuming a bilinear loaddisplacement curve with a strain hardening of 5% and the ductility demand as puted earlier. This yield base shear served as the design base shear (Vd) of the frame. Of the two performance criteria, the base shear puted from the second criterion governed and was equal to 415 kips. UM Design The base shear was recalculated by using a procedure developed at UM (Leelataviwat [2], Lee [3]), where a fraction of the peak elastic input energy of an earthquake to a structure is equated to the energy needed by the structure in getting pushed up to the maximum target displacement. The procedure is briefly described below. In the first step, the base shearroof displacement profile of the frame was modeled by an idealized trilinear curve, as shown in Figure 3. This trilinear curve was obtained by considering the base shearroof displacement profiles of the braced frame and the moment frame separately. Both of these profiles were idealized by elasticperfectly plastic responses. Roof drift of the braced frame at yield point can be easily calculated from the geometry of the frame. As mentioned earlier, the base shear carried by the braced frame at this point was assumed as 80% of the total design base shear Vd, which is an unknown at this stage. Based on past analysis results, roof drift of the moment frame at yield was assumed as 2%, carrying the remaining 20% of the total base shear. These two bilinear curves were superimposed to obtain the trilinear loaddisplacement curve of the whole frame (Figure 3). This trilinear curve was further simplified to a bilinear curve (Figure 3) by equating the areas under the two curves. The design ductility demandfor the frame was calculated from this curve. 0 1 0 1 2 3 Roof Drift (%) Base Shear/Vd Figure 3: Idealized frame responses for Collapse Prevention criterion In the next step, the peak input energy was calculated by considering an elastic SDOF system and by using the equation given by Housner [4], as shown below, 2 2 1 E MSv , (2) where M and Sv are the total mass and the pseudo spectral velocity of the system, respectively. However, for an inelastic system, this equation needs to be modified (Figure 4a). Thus, a modification factorwas applied to Eqn. (2) to estimate the energy needed to push the idealized elasticperfectly plastic system to the selected target displacement, as shown in Figure 4a. Applying this modification factor and converting Sv to spectral acceleration C g e , the modified required energy, m E , can be rewritten as, 2 2 2 1 ⎥⎦ ⎤ ⎢⎣ ⎡ m e C T E Wg , (3) where W and T are the total weight and the fundamental period of the system, respectively. e C is the maximum base shear coefficient. Following the seismic provisions of IBC 2020 [5], the value of T for the 3story frame was estimated as sec. Using this period, e C was obtained from the design response spectra given in the Draft Taiwan Seismic C。