Search

• Shaking table tests of a scaled three-story indoor substation were conducted. • Two different isolation techniques were applied and corresponding isolation effect were discussed. • Influence of the far-field earthquake and near-fault earthquake was investigated. • Scaled electrical equipment was also prepared and the influence of the equipment-structure interaction were discussed. In order to investigate the seismic performance of indoor RC substations with combined base isolation technique under far-field earthquakes and near-fault earthquakes, a 1/4 scaled three-story RC frame model was prepared for shaking table tests. Three different model configurations were considered, namely the non-isolated model (control model), the mono-isolated model (model with lead rubber bearings), and the combined isolated model (model with lead rubber bearings and viscous dampers). Scaled transformers and GISs were also installed on the model floors to consider the influence of the electrical equipment. Typical far field and near fault seismic waves, in this study the El Centro wave and the ChiChi wave, respectively, up to a PGA of 0.44 g were used as excitations. It was found that LRBs worked desirably for the RC model under the El Centro wave while less effective under the ChiChi wave. The acceleration responses (roof), the inter-story shear force (1F) and the inter-story drift (2F) were reduced by use of the LRBs at most by 21%, 51% and 26%, respectively, with respect to the non-isolated model under the El Centro wave. However, under the ChiChi wave irregular torsional behavior was observed and the isolation layer displacement reached 88% of the limit value. Combined use of LRBs and VDs effectively reduced the seismic responses of the RC model under the ChiChi wave. In particular, the isolation layer displacement was reduced by 15% and the torsional displacement ratio was reduced to less than 1.15, with respect to the model with LRBs only. Considerable equipment-structure interaction was found in the RC indoor substations and increased the acceleration and the displacement responses by up to 21% and 22%, respectively, given the position and mass of the equipment in this study. Besides, the LRBs and VDs were found to be effective to reduce the equipment-structure interaction. [ABSTRACT FROM AUTHOR]

To improve the resilience performance of precast concrete frame structure, a novel self-centering prefabricated concrete beam-column joint with controllable plastic hinge (PJ-CPH) is proposed in this manuscript. Controllable plastic hinge is an innovative connection configuration composed by pin shaft, rotational friction damper and disc spring self-centering devices. The rotational friction damper is used for withstanding bending moment and dissipating seismic energy. The disc spring self-centering device is used for withstanding bending moment and providing restoring force, while the pin shaft is merely used for withstanding shear force. A detailed design procedure was presented by introducing self-centering ratio α and moment amplification factor β. A flag-shaped hysteretic model of PJ-CPH was proposed, simultaneously, a numerical model was developed based on the OpenSees computational platforms. The numerical simulation analysis was carried out for four PJ-CPH models with different parameters and one cast-in-situ beam-column joint model under low cyclic loading. Analysis results indicate that the hysteretic curve obtained by theoretical calculation are in good agreement with the numerical simulation results. Consequently, the effectiveness of the established hysteretic model was verified. Compared with the cast-in-situ beam-column joint, PJ-CPH achieves the damage-free connection and exhibits the superior resilience performance. The simulation results suggest that self-centering ratio α values should be assumed approximately in the range 1.00–1.30, moment amplification factor β values in 1.30–1.40, which can induce damage to concentrate in controllable plastic hinge, protect the main structure from damage and reduce repair costs. • A design procedure of PJ-CPH is proposed. • A hysteretic model of PJ-CPH is presented. • A numerical model of PJ-CPH is developed. [ABSTRACT FROM AUTHOR]

• Methods to define the sub-structure range and its boundary conditions are proposed. • A damage index for damage assessment of RC frame structure subjected to blast loads is defined based on energy conservation and could be derived through progressive collapse analysis of RC frames under close-in explosions. • The substructure-based method for damage assessment of RC frame structure is proposed and proved to be accurate, reliable and more efficient as compared to conventional method. Few studies are available in the literature on damage assessment of frame structures under blast loads although local damage of the structural components and even progressive collapse of building structures have been observed in terrorist or accidental explosions. In this paper, considering the initial damage of adjacent structural components under blast loading, a substructure based method for damage assessment of RC frame structures is proposed, including the proposal of the damage criterion, the principles for substructures selection and the calculation of the boundary conditions of the substructures. The accuracy and reliability of the proposed method are verified by comparing the results for damage assessment of a typical 5-story frame structure under different blast scenarios with the conventional method and the proposed method. The results indicated that the proposed method could rapidly and accurately predict the damage levels of the RC frame structure under a given blast load, especially when the building structures are damaged under close-in explosion. [ABSTRACT FROM AUTHOR]

This study explores the collapse process of a reinforced concrete (RC) frame structure subjected to earthquake shakings, by applying the shaking table test on a three-story, one-bay, 1/5-scaled RC structural model. The frame specimen transformed from an elastic state to a highly nonlinear state, then experienced dynamic instability, and finally collapsed to the ground. The structural responses that have been monitored in the presented test include the specimen’s dynamic properties, displacements, and accelerations. The data collected from this benchmark test program can be used for the verification of existing analytical and numerical simulation methods, especially for cases involving the large displacement and rotation or collapse process simulation of RC frame structures. It is observed from the test that: (1) the frame survived when the maximum story drift ratio and the residual drift ratio reached 12.51% and 9.60% respectively, indicating that the RC frame structure may have a much high ductility capacity; (2) the collapse of the 1 st , 2 nd , and 3 rd stories was due to failure of the plastic hinges at columns; and (3) during the collapse process, the collisions and the damage-induced local oscillation can generate very large horizontal and vertical acceleration responses. More specifically, the collapse of the 1 st story was the result of the failure of plastic hinges, caused by seismic excitation, while collapse of the 2 nd and 3 rd stories resulted from the combined results of plastic hinge failures and punching shear failures in the slab due to impact effects. [ABSTRACT FROM AUTHOR]

Highlights: [•] Impulse-based impact models for collisions between fractured components are proposed. [•] A DEM-based collapse simulation system with impact models is developed for RC frames. [•] Visual collapse simulation of two frames in an earthquake and controlled explosion. [•] Collapse mechanism, including impacts and debris distribution, is presented. [•] Proposed simulation system can facilitate collapse simulation of RC frames. [Copyright &y& Elsevier]

• Local inelastic demands in the probabilistic assessment of structural pounding risk. • Different types of structural pounding between adjacent RC structures. • Local and global PSDMs against pounding using linear and bilinear regression models. • Compounded fragility-based solution on evaluating the structural pounding risk. • New performance levels thresholds against pounding between adjacent RC structures. The aim of this study is to incorporate the local inelastic demands of a multistory reinforced concrete (RC) frame structure for the first time in the probabilistic seismic assessment of the pounding risk. Two distinct types of structural pounding are examined: a) the floor-to-floor structural pounding - Type A, and b) the inter-story (floor-to-column) structural pounding - Type B. Three different initial gap distances d g between the adjacent structures are considered. The seismic performance of the RC frame structure without the pounding effect is also estimated. The probabilistic evaluation of the pounding effect is performed through fragility curves in terms of global and local engineering demand parameters (EDPs) as a function of the peak ground acceleration (PGA). The first part of this research is focused on the development of global and local probabilistic seismic demand models (PSDMs) against pounding risk. For this purpose, linear and bilinear regression models have been used. Afterwards, the fragility assessment of the RC frame against pounding is performed (a) as a function of the separation gap distance d g , (b) based on the global seismic performances, and (c) based on the local seismic performances. A compounded fragility-based solution on evaluating the pounding risk at different performance levels is also presented and new performance levels thresholds are introduced. Results indicate that the local performances of the columns of the RC structure are crucial demand parameters for the probabilistic assessment of the pounding risk. The type of the structural pounding (Type A or Type B) that is occurred between the adjacent structures significantly alters the results of the probabilistic assessment when the local performances are considered. The compounded evaluation of the pounding risk clearly indicates that the RC frame structure exceeds the examined performance levels at a lower value of PGA when subjected to pounding in comparison to the corresponding cases without pounding. Finally, a decision method is presented as an approach to estimate the minimum separation gap distance d g,min between adjacent structures when global and local performances are incorporated in the fragility assessment process. [ABSTRACT FROM AUTHOR]