Linlin Xie

Experimental Study and Numerical Model Calibration for Earthquake-Induced Collapse of RC Frames with Emphasis on Key Columns, Joints, and the Overall Structure

A thorough investigation of earthquake-induced collapse of reinforced concrete frames is presented. The inherent correlation between the nonlinear behavior of key components and the collapse mechanism of overall frame is examined through concurrent collapse tests of both frame and key components. Important issues in the component models are investigated through calibration against experiments, leading to a comprehensive structural system model. Both test and simulation indicate that the seismic performance are predominately governed by the key columns, whereas the energy dissipation capacity is somewhat affected by the joints. This study offers systematic experimental data and numerical models for future collapse assessments.

Experimental study and numerical model calibration of full-scale superimposed reinforced concrete walls with I-shaped cross sections

The superimposed reinforced concrete wall in which both the walls and slabs are semi-precast superimposed reinforced concrete components has been widely used to construct high-rise residential buildings in some seismic regions of China. This article aims to investigate the seismic performance and reveal the inherent damage mechanism of this wall. Quasi-static tests of two full-scale superimposed reinforced concrete walls with I-shaped cross sections, consisting of the walls in orthogonal directions and two T-shaped cast-in-place boundary elements, were conducted. Through the test, the behavior of the horizontal joints between the wall panels and the foundation; the behavior of the vertical connections between the wall panels of orthogonal direction; the reliability of the connections between precast and cast-in-place concrete; and the lateral load, deformation, and energy dissipation capacities of the specimens are evaluated. In addition, a refined numerical model based on the multi-spring model was adopted to assess the seismic performance of the superimposed reinforced concrete walls with I-shaped cross sections. The reliability of this model was validated through comparison with the experimental data. This study offers valuable experimental data and numerical model references for future seismic performance assessments of superimposed reinforced concrete wall structures.

Multi-Layer Shell Element for Shear Walls in OpenSees

Reinforced concrete (RC) shear walls is one of the most widely used lateral force-resisting members of high-rise buildings. This research developed a multi-layer shell element on an open-source FE code of OpenSees for shear walls. The multi-layer shell element can simulate the coupled in-plane/out-of-plane bending as well as the in-plane shear and coupled bending-shear behavior of RC shear walls, and it comprehensively reflects the spatial mechanical behavior of the shell structures. The simulation of rectangular walls, flanged walls and coupled walls under pseudo-static loading was conducted. The simulated results agree well with the experimental results, which validates the rationality and reliability of the proposed model. The nonlinear seismic analyses of a super-tall building, namely Shanghai Tower with a height of 632 m, were conducted based on the fiber beam and multi-layer shell elements, and good agreement was achieved between the analytical results of OpenSees and MSC.Marc. The outcome of this study provides an effective tool and a useful reference for the simulation of high-rise buildings using OpenSees.

A High-Performance Quadrilateral Flat Shell Element for Seismic Collapse Simulation of Tall Buildings and Its Implementation in OpenSees

ABSTRACT Shear walls are important lateral force-resistant components of tall buildings. Hence, a reliable numerical model that can accurately represent the mechanical characteristics and large deformations of shear walls is critical for realistic collapse simulation of tall buildings. Based on the theory of generalized conforming element, a high-performance quadrilateral flat shell element, NLDKGQ, accounting for the large deformation using the updated Lagrangian formulation, is proposed herein and implemented in OpenSees. The reliability of NLDKGQ is validated using classical benchmark problems and reinforced concrete specimens. In addition, its capability in simulating the collapse of a tall building is also demonstrated.

Experimental Study on the Seismic Performance of Superimposed RC Shear Walls with Enhanced Horizontal Joints

ABSTRACT The seismic performance of superimposed reinforced concrete (RC) shear walls is decreased by rocking behavior and damage concentration at the horizontal joint. An enhanced horizontal joint method is proposed to improve the corresponding seismic performance. To validate the reliability of the proposed method, three full-scale superimposed walls and a cast-in-place shear wall (for comparison) are designed and tested under the quasi-static load. The test results indicate that the rocking phenomenon can be prevented using the proposed method, and the seismic performance of superimposed RC shear walls with enhanced horizontal joints is comparable to that of the cast-in-place RC shear walls.

Earthquake-induced Collapse Simulation of a Super Long Span Cable-Stayed Bridge Based on an Open Source FE Program

Currently, the seismic performance assessments of long span bridges are generally conducted using commercial finite element (FE) software packages, which to some extent limit the in-depth investigation of associated topics. A numerical model system is proposed to simulate a super long span cable-stayed bridge with a maximum span of 1500 m based on an open source FE software package (i.e., OpenSees). The seismic performance of this bridge is investigated. The simulation results of OpenSees and the commercial software MSC.Marc are compared with a good agreement. Furthermore, a collapse simulation of the bridge is also successfully performed and the corresponding collapse mechanism is revealed. The research outcome could provide a reference for further studies on the seismic performance of super long span cable-stayed bridges based on open source FE programs.

GPU-Powered High-Performance Computing for the Analysis of Large-Scale Structures Based on OpenSees

Numerical simulations using various finite element (FE) software packages have been widely adopted to investigate the seismic performance of large-scale important structures, such as super-tall buildings and large-span bridges. Among these FE software packages, Open System for Earthquake Engineering Simulation (OpenSees), as an open-source FE software program, has increasingly become one of the most influential packages. However, the computational efficiency of the solvers for linear systems of equations (SOE) in OpenSees, which use the direct method, cannot satisfy the demand for numerical simulation of large-scale structures. Consequently, two new parallel-iterative solvers for the sparse SOE are proposed and implemented in OpenSees, based on two graphics processing unit (GPU)-based libraries, CuSP and CulaSparse. The time history analysis of a 141.8 m frame-core tube building and a super-tall building (the Shanghai Tower with a height of 632 m) are performed using the proposed solvers. The speed-up ratio of the proposed solvers is up to 9 to 15, with high accuracy in results when compared with the efficiency of the existing central processing unit (CPU)-based SparseSYM solver in OpenSees. This research outcome can provide an effective computing technology for the numerical analysis of the seismic behavior of large-scale structures.

Experimental investigation on the mechanical behaviour of a new superimposed RC exterior basement wall with socket base

Abstract A new superimposed RC exterior basement wall with socket base is proposed here. To investigate the mechanical behaviour and failure mode, nine such basement walls and one cast-in-place basement wall were tested under the monotonic lateral load. The test results indicated that crack distributions and the corresponding loads of the superimposed basement walls under the serviceability limit state, which is the critical state that controls the design of the basement wall, are approximately identical with those of their cast-in-place counterpart. The failure of this new basement wall is generally dominated by the failure of the diagonal compression struts in the wall embedded in the socket base, whereas the failure mode of its cast-in-place counterpart is shear-compression failure near the bottom of the wall. Furthermore, the effects of four critical parameters were investigated: embedded length, thickness of the exterior lateral wall of socket base, longitudinal reinforcement ratio and roughness of the interface. The outcome of this study will provide systematic experimental data and conceptual understanding for the design of superimposed RC exterior basement walls with socket bases.

Collapse Simulation of Building Structures Induced by Extreme Earthquakes

Research development has demonstrated that numerical simulation is becoming one of the most powerful tools for collapse analysis of building structures in addition to the conventional laboratory model tests and post-earthquake investigations. In this paper, a finite element (FE) method based numerical model encompassing fiber-beam element model, multi-layer shell model and elemental deactivation technique is proposed to predict the collapse process of buildings subjected to extreme earthquake. The potential collapse processes are simulated for several different types of buildings. The analysis results indicate that the proposed numerical model is capable of simulating collapse process of buildings by identifying potentially weak components of the structure that may induce collapse. The study outcome will be beneficial to aid further development of optimal design philosophy.