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51.
Response of masonry walls to out-of-plane excitation is a complex, yet inadequately addressed theme in seismic analysis. The seismic input expected on an out-of-plane wall (or a generic “secondary system”) in a masonry building is the ground excitation filtered by the in-plane response of the walls and the floor diaphragm response. More generally, the dynamic response of the primary structure, which can be nonlinear, contributes to the filtering phenomenon. The current article delves into the details and results of several nonlinear dynamic time-history analyses executed within a parametric framework. The study addresses masonry structures with rigid diaphragm response to lateral loads. The scope of the parametric study is to demonstrate the influence of inelastic structural response on the seismic response of secondary systems and eventually develop an expression to estimate the seismic input on secondary systems that explicitly accounts for the level of inelasticity in the primary structure in terms of the displacement ductility demand. The proposed formulation is discussed in the companion article. 相似文献
52.
The seismic response of base-isolated benchmark building with variable sliding isolators like variable friction pendulum system (VFPS), variable frequency pendulum isolator (VFPI), and variable curvature friction pendulum system (VCFPS), along with conventional friction pendulum system (FPS), was studied under the seven earthquakes. The earthquakes are applied bi-directionally in the horizontal plane ignoring vertical ground motion component. The shear type base-isolated benchmark building is modeled as three-dimensional linear elastic structure having three degrees of freedom at each floor level. Time domain dynamic analysis of the benchmark building was carried out with the help of constant average acceleration Newmark-Beta method and nonlinear isolation forces was taken care by fourth-order Runge-Kutta method. The base-isolated benchmark building is investigated for uniform isolation and hybrid isolation in combination with laminated rubber bearings through the performance criteria and time history response of important structural response parameters like floor accelerations, base displacement, etc. It is observed that variable sliding isolators performed better than conventional FPS due to their varying characteristic properties which enable them to alter the isolator forces depending upon their isolator displacements thus improves the performance of the structure. The VFPS efficiently controls large isolator displacements and VFPI and VCFPS improve super structural response on the cost of isolator displacement. It is also observed that the hybrid isolation is relatively better in comparison to the uniform isolation for the benchmark building. 相似文献
53.
The nonlinear seismic response of base-isolated framed buildings subjected to near-fault earthquakes is studied to analyze the effects of supplemental damping at the level of the isolation system, commonly adopted to avoid overly large isolators. A numerical investigation is carried out with reference to two- and multi-degree-of-freedom systems, representing medium-rise base-isolated framed buildings. Typical five-story reinforced concrete (RC) plane frames with full isolation are designed according to Eurocode 8 assuming ground types A (i.e., rock) and D (i.e., moderately soft soil) in a high-risk seismic region. The overall isolation system, made of in-parallel high-damping-laminated-rubber bearings (HDLRBs) and supplemental viscous dampers, is modeled by an equivalent viscoelastic linear model. A bilinear model idealizes the behavior of the frame members. Pulse-type artificial motions, artificially generated accelerograms (matching EC8 response spectrum for subsoil classes A or D) and real accelerograms (recorded on rock- and soil-site at near-fault zones) are considered. A supplemental viscous damping at the base is appropriate for controlling the isolator displacement, so avoiding overly large isolators; but it does not guarantee a better performance of the superstructure in all cases, in terms of structural and non structural damage, depending on the frequency content of the seismic input. Precautions should be taken with regard to near-fault earthquakes, particularly for base-isolated structures located on soil-site. 相似文献
54.
M. S. Günay 《Journal of Earthquake Engineering》2013,17(5):623-649
An equivalent linearization procedure is developed for predicting the inelastic deformations and internal forces of capacity-designed structures under earthquake excitations. The procedure employs response spectrum analysis, and mainly consists of the construction of an equivalent linear system by reducing the stiffness of structural members that are expected to respond in the inelastic range. These members are well defined in structures designed with capacity principles. Maximum modal displacement demands of the equivalent linear system are determined either from the equal displacement rule, or from independent nonlinear response history analysis of SDOF systems representing inelastic modes. Predictions obtained from the proposed equivalent linearization procedure are evaluated comparatively by using the results of nonlinear response history analysis as benchmark, linear elastic response spectrum analysis and conventional pushover analysis. The deformations and capacity controlled actions of a 12-story symmetrical plan concrete frame and a 6-story unsymmetrical plan concrete frame are obtained by each method under 96 strong ground motions. It is observed that the proposed procedure results in better accuracy in estimating the inelastic seismic displacement response parameters and capacity controlled forces than the other two approximate methods. 相似文献
55.
Using representative numerical models of eight code-designed steel moment-resisting frame buildings and several ground motions, time-history analyses are performed and a critical evaluation of Peak Horizontal Floor Acceleration (PHFA) demands is conducted. The frames are modeled alternatively as linear and nonlinear systems to isolate the effect of building nonlinearity on PHFA. In most cases, PHFA is reduced when nonlinear behavior of a building is considered; however, in some cases, significant amplification of PHFA is observed. Results from the numerical study provide insight into the trend of modal response modification factors presented taking ground motion spectral shape into account. 相似文献
56.
Iunio Iervolino Giuseppe Maddaloni Edoardo Cosenza 《Journal of Earthquake Engineering》2013,17(8):1125-1152
57.
Georgia E. Thermou Amr S. Elnashai Stavroula J. Pantazopoulou 《Journal of Earthquake Engineering》2013,17(5):743-770
This article presents a novel approach for deriving Retrofit Design Spectra (RDS) that are intended for use in preliminary development and assessment of seismic upgrading scenarios of existing structures. The new spectral representation relates the characteristics of the intervention method chosen as the core of the upgrading strategy, with the ductility and strength demand of the retrofitted structure. The methodology utilized for the derivation of the RDS is based on the Capacity Spectrum Method where the capacity curve is described by relationships for global and local intervention methods that are parameterized in terms of fundamental response quantities. The proposed spectra provide direct insight into the complex interrelation between the characteristics of the intervention method and the implications of the upgrading scenario on demand. Alternative retrofit solutions are thus assessed in an efficient way. A case study is used to illustrate practical application of the new approach. 相似文献
58.
A complete structural analysis of the bell tower of Santa Maria del Carmine in Naples (Italy) has been developed by using a 3D FE model based on the results of detailed experimental investigations in situ. Linear analysis for gravity loads, linear modal analysis, and nonlinear static analysis (Push Over) were carried out in order to assess the seismic capacity of the structure. A check of local out-of-plane failure mechanisms was also performed to verify if the structure is able to attain a global behavior. Problems and solutions related to the different methods are presented and discussed. 相似文献
59.
This article presents a Lyapunov-based analysis/redesign approach for the optimal seismic design of added viscous dampers in 3D framed structures. The optimal solution minimizes the total added damping while the mean squared drifts at the peripheral frames are constrained to allowable values under a white noise excitation. The proposed approach uses Lyapunov equation for analysis and an optimality criterion that dictates “fully stressedness” for redesign. Hence, the design process is actually comprised of an iterative solution of a set of algebraic equations. Three examples are solved so as to highlight the advantages of the proposed approach — a 3-story shear frame, an 8-story, 3-bay by 3-bay setback frame, and a 10-story industrial frame. 相似文献
60.
Biao Wei Peng Wang Menggang Yang Lizhong Jiang 《Journal of Earthquake Engineering》2013,17(2):325-342
This article attempted to improve the isolation performance of a rolling isolation system by assuming that the rolling friction force gradually and linearly increased with the relative displacement between the isolator and the ground. After the rolling isolation system under different ground motions was calculated by a numerical analysis method, it obtained more regular results than that of other uneven friction distributions. Results shows that the considered concavely distributed friction force can not only dissipate the earthquake energy, but also change the structural natural period. These functions improve the seismic isolation efficiency of the structural relative displacement in comparison with the general uniform distribution of rolling friction coefficient. 相似文献