دانلود رایگان مقاله انگلیسی مقررات استاندارد سختی بتن مسلح و ساختمان دیوار برشی - الزویر 2016

abstract

The accuracy of the lateral stiffness provisions of international standards is examined for concrete buildings. The stiffness provisions of American, Japanese, Canadian, New Zealand, and European standards are evaluated. Standard stiffness estimates are compared with the experimentally derived lateral stiffnesses of a four-story, full-scale, reinforced concrete building tested under multi-directional seismic motions on the Japanese E-Defense shaking table. The structure was designed to Japanese seismic design requirements and met most U.S. design requirements for regions of high seismicity. The building had moment frames resisting lateral loads in one direction and shear walls in the other. Building stiffness was found to degrade substantially with increasing lateral drifts and relate to prior deformation history. In general, standard stiffness values were higher than those of the building. Standard provisions produced more accurate stiffness estimates for frame members than for walls. All standard provisions produced substantially larger stiffness estimates than experimental values for shear walls. Study results therefore indicate that improvements in the stiffness provisions of all investigated standards for concrete buildings may be warranted.

5. Stiffness comparison between standards and experiments

The three-dimensional models for each standard were subjected to all components of the JMA-Kobe 50% motion recorded at the foundation of the building. Secant story stiffnesses were extracted from the computational models as was done from experimental data. The average of the model secant story stiffnesses are compared in Fig. 7 with experimental story stiffnesses measured at various testing stages. The experimental and analytical secant stiffnesses shown in Fig. 7 were obtained at the end of each of the JMAKobe motions scaled to 10%, 25%, and 50%. For comparison purposes, the cumulative story-stiffness error (CSSE) is defined as the sum of the analytical story stiffnesses divided by the sum of the experimentally derived story stiffnesses (CSS) minus one. Likewise, the first story stiffness error (FSSE) is defined as the analytical story stiffnesses of the first story divided by the experimentally derived first story stiffnesses (FSS) minus one. Table 9 summarizes the experimental cumulative story-stiffnesses (CSS), the experimental first story stiffnesses (FSS), the CSSE, and the FSSE for all standards considered at various stages of the testing protocol. As can be seen in Fig. 7 and Table 9, no stiffness provisions captured the stiffness of the test building at all lateral drift levels. Standard stiffness values are fixed for given component properties, while the stiffness of the building was observed to decrease markedly as the lateral drifts increased, even at low drift levels (Figs. 5– 7). To aid in the comparison between experimental and computational stiffnesses, the secant stiffness values for all lateral drift cycles are plotted in Fig. 8, with arrows linking them in the order the stiffnesses occurred during the JMA-Kobe 50% motion. Fig. 8 highlights the stiffness reductions of the first and second stories with increasing peak prior drift demands. In Fig. 8, the story stiffness values derived using the various standards are introduced as well.