Residual displacement estimation of the bilinear SDOF systems under the near-fault ground motions using the BP neural network

This paper presents a comprehensive study of residual displacements of the bilinear single degree of freedom (SDOF) systems under the near-fault ground motions (NFGMs). Five sets of NFGMs were constructed in this study, in which the natural ones as well as the synthesized ones were both considered. By way of the nonlinear time history analyses, three different residual displacement spectrums were obtained and analyzed in detail. Utilizing the calculated data, a back propagation (BP) neural network was established to predict the residual displacements of the bilinear SDOF systems under the NFGMs. The results show that the structural parameters, including the strength reduction factor and the post-yield strength ratio, have significant and relatively consistent impacts on the residual displacement spectrum. However, the ground motion characteristics, including the fault type, the closest distance from the site to the fault rupture, the earthquake magnitude, and the site soil condition, exhibit more complex effects on the residual displacement spectrum. In addition, the proposed BP neural network can fully incorporate the parameters affecting the residual displacements of the bilinear SDOF systems under the NFGMs, while having a fairly good accuracy in predicting the residual displacements.

Prestressed concrete wall system with friction devices: Seismic performance and direct displacement–based seismic design

It is convenient to use the inelastic displacement ratio spectra and residual displacement ratio spectra to predict the maximum inelastic displacement and residual displacement of building structures based on linear elastic analysis directly. The prestressed concrete wall system with friction devices (PCW-FD system) can be simulated by single-degree-of-freedom (SDOF) model with self-centering behavior. To investigate the seismic performance of PCW-FD system, the SDOF models with fully and non-fully self-centering behavior are analyzed firstly, and it is concluded that the hysteresis parameters (strength reduction coefficient, post-yield stiffness coefficient, energy dissipation coefficient, and period) have significant influence on the seismic responses (such as constant relative strength inelastic displacement ratio, constant relative strength residual displacement ratio, maximum absolute acceleration, the hysteretic energy, and site classifications) during short period, and the trends of the seismic responses are similar at different site classifications. Then a large amount of the result data is summarized, and the constant relative strength inelastic displacement ratio spectra and the constant relative strength residual displacement ratio spectra with enough precision (the correlation coefficients are 0.957 and 0.947, respectively) are established by conducting regression analysis. Finally, the direct displacement–based seismic design method is improved and verified to be suitable for PCW-FD system.

Seismic Behavior of RC Moment Resisting Structures with Concrete Shear Wall under Mainshock-aftershock Seismic Sequences

A structure may subject to several aftershocks after a mainshock. In many seismic design provisions, the effect of the seismic sequences is not directly considered or underestimated. This paper studies the seismic behavior of RC moment-resisting structures with concrete shear wall under seismic sequences. Two three-dimensional structures of short and medium height were designed and analyzed. The former models were studied under a group of real mainshock-aftershock seismic sequences. The models were loaded and designed according to the fourth edition of the Iranian seismic code of standard no. 2800 and ACI-318 respectively. Furthermore, the non-linear dynamic time-history finite element analysis of models was performed via the explicit method. The parameters of maximum displacement, inter-story drift ratio, residual displacement, and finally the effect of the ratio of aftershock acceleration to mainshock acceleration were investigated and assessed. Due to the high lateral stiffness of shear walls, parallel with the complete elastic behavior, aftershocks cause no growth in inter-story drift ratio and relative displacement in the short structure model. In contrast, compared to the structure under the solely mainshock, the medium height structure model under seismic sequences showed significant growth in the amount of relative displacement (even more than 50% growth), inter-story drift ratio, plastic strain, and residual displacement (almost 30% growth). Furthermore, unlike the moment-resisting frame structures, models showed no significant growth in the drift ratio with the height. Assessments indicated that the ratio of aftershock to mainshock acceleration is a determinative parameter in structural behavior under seismic sequences.

Numerical Investigation of Residual Displacement of Rocking Self-Centering Columns Under Cyclic Loading

Well-designed rocking self-centering (RSC) columns are capable of achieving small residual displacement. However, few studies conducted the quantitative analysis for the residual displacement of RSC columns. The residual displacement is the product of the struggle between the self-centering (SC) capacity and the energy dissipation (ED) capacity. In this study, a SC factor and an ED parameter were defined to reflect the SC and ED capacity of the RSC column, respectively. The influence of eight common design parameters on the SC factor and the ED parameter was explored using factorial analysis. Parametric analysis was performed to investigate the tendency of the SC factor and the ED parameter with the increase of maximum drift. According to the results of the parametric analysis, the effect of the SC factor and the ED parameter on the distribution of the residual drift was researched statistically. A simplified formula was proposed to calculate the upper limit of the residual drift. What is more, a set of predictive regression formulas was established to estimate the actual residual drift, these regression formulas have an applicable condition that the ED parameter should be larger than 0.75. When the ED parameter was less than 0.75, the residual drift is approximate to zero.

Post-earthquake fast damage assessment using residual displacement and seismic energy: Application to Mexico City

The simplicity, timeliness, and reliability of a post-earthquake assessment are fundamental for decision-makers in emergency management. An adequate risk assessment will help during the recovery and, therefore, increases the resilience of the community. Although within this context, the walk-down damage survey with the correct filling of evaluation forms and use of processing-data tools make possible a pertinent post-earthquake assessment, it is desirable to have measurable parameters that can complement the visual field evaluation with quantitative information. In some cases, basic quantitative measures, such as crack width, are not enough to make pertinent structural damage assessments. This article presents a fast and simple methodology to estimate the median maximum displacement and plastic energy demands on simple single-degree-of-freedom systems from the residual displacement they exhibit after being subjected to ground motions generated in the lakebed zone of Mexico City. Based on this, a discussion is offered on how a post-earthquake assessment can be improved by complementing the visual and measured information gathered on an existing structural system after an intense ground motion, with estimates of its maximum and cumulative plastic deformation demands derived from its residual deformation.

Preliminary study on the threshold stiffness and residual displacement of the multangular-pyramid concave friction system (MPCFS) for seismic isolation

In this research, the threshold stiffness and residual displacement of the MPCFS are both investigated. The MPCFS has a higher threshold (breakaway) stiffness and no residual displacement after earthquakes or ambient vibrations, which makes it different from the conventional Curved Surface Slider (CSS). These two features can enable the MPCFS to be more stable when experiencing micro-to-small shakings, and always restore to its central point after earthquakes. With the aim of testifying the two features, a series of analytical simulations are conducted on a four-storey building model equipped with MPCFS. The analytical results are compared with that obtained with CSS. The simulation results validate the aforementioned virtues of MPCFS over the CSS. This indicates that MPCFS has great potential in the engineering practice of seismic isolation.