Pushover analysis features in ETABS include the implementation of FEMA 356 and the hinge and fiber hinge option based on stress-strain. The nonlinear layered shell element enables users to consider plastic behavior of concrete shear walls, slabs, steel plates, and other area finite elements in the pushover analysis. Force-Deformation relations are defined for steel and concrete hinges.
pushover analysis in etabs 2015 keygen
Download File: https://urlca.com/2vGeQN
The fundamental component of PBD is nonlinear dynamic analysis where an attempt is made to capture the real behavior of the structure by explicitly modeling and evaluating post-yield ductility and energy dissipation when subjected to earthquake ground motions. ETABS 2015 introduces new special purpose options and algorithms for the practical and efficient application of these procedures.
Many seismic assessment methods for buildings have been developed in recent years (ATC 1996; FEMA 1998, 2000); however, those methods seldom mention re-evaluating the seismic residual of earthquake-damaged buildings. Di Ludovico et al. (2013) proposed the experiment-based expressions of modification factors for stiffness, strength and displacement capacity as a function of the rotational ductility demand. Additionally, the proposed expressions can be introduced to modify the moment-rotation plastic hinges of RC columns in the buildings of Mediterranean regions with design characteristics non-conforming to present-day seismic provisions. However, how to apply the modification factors for stiffness, strength and displacement capacity in the seismic performance assessment is not mentioned clearly in the paper. The guidelines developed by JBDPA (2001, 2015) for evaluating the residual seismic performance of earthquake-damaged buildings can be used to determine the damage class of a building; however, the procedure is only suitable for the preliminary seismic performance assessment. Restated, a preliminary seismic performance assessment does not provide sufficient data for engineers or users to make decisions on earthquake-damaged buildings. Additionally, for the detailed seismic performance assessment of low-rise RC building structures in Taiwan, engineers need to use the nonlinear static analysis method, which is different with the method proposed in the JBDPA guidelines (2001, 2015). Therefore, a post-earthquake detailed assessment method of seismic performance is needed to evaluate the residual seismic performance of an earthquake-damaged RC building for the post-earthquake maintenance strategy.
In place of the reduction factors that are defined in terms of the energy dissipation capacity, Ito et al. (2015) proposed reduction factors of the strength, deformation, and damping ratio of damaged RC column members for evaluating post-earthquake residual seismic performance. The reduction factors of strength were obtained directly from experimental results. For each selected specimen, Ito et al. (2015) used the damage index model of Park and Ang (1985) to estimate the equivalent ultimate deformation capacity; then, the reduction factors of deformation were calculated from the equivalent ultimate deformation capacity. To evaluate the reduction factor of the damping ratio, Ito et al. (2015) used the equivalent damping ratio to quantify the energy dissipation capacity of damaged RC column members, which was studied using the hysteretic energy under cyclic loading. In the post-earthquake assessment of seismic performance of Ito et al. (2015), their nonlinear statistical analysis considered reduction factors of the strength, deformation and damping ratio of flexural and shear members (Table 3).
Seo et al. (2015) selected a 12-story reinforced concrete moment-resisting frame structure with shear walls to generate a 3D finite element models and evaluate seismic performance using response spectrum analysis and nonlinear time-history analysis approaches on the structure. Beside this, the seismic fragility curves for each floor of the structure were generated to evaluate seismic vulnerability of the structure. Additionally, Mushtaq et al. (2018) take 2D and 3D models of multilayer RC buildings as a case study, and the static cyclic analysis was performed and seismic vulnerability assessment was carried out using the capacity spectrum method. They also concluded that the 3D model is more brittle, cracked earlier, and more susceptible to earthquakes than 2D counterparts. Therefore, this work adopts the 3D model of a multilayer RC building and pushover analysis to simulate its capacity curve, which is the relationship between base shear force VBase and roof displacement ΔR. Additionally, according to the ATC-40 (1996), a constant gravity load combining dead and live loads should be considered in the pushover analysis. The capacity curve is converted to the capacity spectrum, which represents structural performance of the SDOF system for a building by identifying the dynamic characteristics of a structure in terms of the first modal participation factor and the first modal mass coefficient. The ATC-40 (1996) defines the inelastic response of the SDOF system for a building during an earthquake, i.e., acceleration and displacement, as the intersection between its capacity spectrum and its design response spectrum. However, iterative calculations are often needed to find the intersection point. Instead of iterative calculations (NCREE 2009), the capacity spectrum can be transformed into a seismic performance curve according to the design response spectrum modified by the equivalent damping ratio ξeq and equivalent fundamental period Teq (secant period). The curve can then be used to determine the relationship between performance-based ground acceleration and response spectral displacement.
According to the literature (NCREE 2009), infill walls are an efficient way to upgrade the seismic performance of an RC building. In Taiwan, low-rise RC buildings often lack infill walls in the longitudinal direction, which is generally parallel with the corridors. Because of the lack of infill walls, low-rise RC buildings have lower seismic performance in the longitudinal direction than the other direction. Therefore, this case study only assessed the seismic performance of the longitudinal direction for the selected buildings. Figure 23 shows the detailed columns for the pushover analysis. Besides the nonlinear hinge setting described in Sect 5.1, the pushover analysis assumes a rigid diagram in the finite element models. The pushover analysis should be applied to acquire the capacity curves before and after the earthquake (Fig. 24). The seismic capacity before and after the earthquake can be obtained according to the capacity curves and the detailed seismic performance assessment (Table 12). The seismic residual ratios determined using the detailed seismic performance assessment method. Additionally, the peak ground acceleration of earthquake-damaged seismic capacity for the selected building DAp is indeed smaller than the code-required performance AT (Table 12). Therefore, all three buildings require the seismic retrofit.
This work provided reduction factors of seismic capacity for RC columns with various failure modes based on experimental data and the past researches. For an RC column member with seismic damage, besides of the energy dissipation capacity, the residual strength and residual stiffness can be quantified using the suggested reduction factors summarized in Table 13 in this work. According to the damage states of RC columns and their corresponding reduction factors suggested herein, this work proposes the seismic performance assessment method for the residual seismic performance of earthquake-damaged low-rise RC buildings. This work selected one building damaged in the earthquake to demonstrate the post-earthquake assessment of seismic performance. In the future, when many buildings are damaged by a large earthquake, a post-earthquake emergent decision-making procedure for damaged low-rise RC buildings can be conducted using the proposed residual seismic performance assessment method and then determine the strategies for the damaged buildings. However, this work only suggests the reduction factor of damaged column components. Other structural components (such as beam-column joints and walls) will also affect the post-earthquake residual seismic performance of structures in the pushover analysis, and it requires further researches to consider the effects of other components. 2ff7e9595c
Commentaires