Yun Mook Lim

Seismic analysis of base-isolated liquid storage tanks using the BE–FE–BE coupling technique

Abstract A three-dimensional soil–structure–liquid interaction problem is numerically simulated in order to analyze the dynamic behavior of a base-isolated liquid storage tank subjected to seismic ground motion. A dynamic analysis of a liquid storage tank is carried out using a hybrid formulation, which combines the finite shell elements for structures and the boundary elements for liquid and soil. The system is composed of three parts: the liquid–structure interaction part, the soil–foundation interaction part, and the base-isolation part. In the liquid–structure interaction part, the tank structure is modeled using the finite elements and the liquid is modeled using the internal boundary elements, which satisfy the free surface boundary condition. In the soil–foundation interaction part, the foundation is modeled using the finite elements and the half-space soil media are modeled using the external boundary elements, which satisfy the radiation condition in the infinite domain. Finally, above two parts are connected with the base-isolation system to solve the systems behavior. Numerical examples are presented to demonstrate the accuracy of the developed method, and an earthquake response analysis is carried out to demonstrate the applicability of the developed technique. The properties of a real LNG tank located in the west coast of Korea are used. The effects of the ground and the base-isolation system on the behavior of the tank are analyzed.

Dynamic analysis of layered half planes by coupled finite and boundary elements

This study performs dynamic analysis of underground structures on multi-layered half planes in the frequency domain by using the coupled finite and boundary element methods. The near field including the underground structure is modelled with conventional finite elements, while the far field is modelled with the boundary elements which satisfies radiation conditions. To evaluate the dynamic fundamental solutions, the semi-analytical approach to reduce the range of wave number integration is adopted within the boundary elements framework. These solutions satisfy the reflection and transmission conditions of waves at each layer interface, so that the multi-region problem can be analysed. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method.

Three dimensional dynamic response of surface foundation on layered half-space

A dynamic interaction analysis of a surface foundation on a layered half-space is performed in the frequency domain under incident wave excitation. A semi-analytical approach is employed to reduce the integration range of the wavenumber in the fundamental solution for a layered half-space in boundary element (BE) formulations. The present study then adopts a coupling method that combines the finite element (FE) for the surface foundation and the boundary element for the layered half-space. The response of a foundation is decomposed to a free field and a scattered field after the impedance matrix for the foundation system is calculated. Numerical examples are presented to demonstrate the accuracy of the developed method. The examples show the feasibility of an extended application for the complicated dynamic analysis of foundations on layered media under incident wave excitation.

Flexural behaviour of a half-decked bulb tee pre-stressed concrete girder: full-scale test and nonlinear finite element analysis

Abstract A half-deck bulb tee (HBT) girder, which is an unusual concept for pre-stressed concrete girders, was developed and tested for a long span application. The purpose of the test was to simplify the construction process and increase structural performance by optimising the cross sections and improving the efficiency of the tendon profile. In this study, a full-scale HBT girder, with a length of 60 m and depth of 2.3 m, which includes the .1 m depth of the half-deck, was fabricated and tested to analyse its structural performance. The data observed from the flexural loading tests were evaluated by comparing with the results of finite element analysis (FEA). The tested HBT girder specimen was expected to be sufficiently safe for actual bridge design because it satisfied construction code requirements. The initial cracking load observed during the experiment (1400 kN) was accurately predicted by FEA (1420 kN) and theory (1301 kN). Therefore, the developed HBT girder has sufficient and predictable flexural strength.

Analysis of Buried Lifeline Under Seismic Wave Propagation Using Ground Strain Concept

In this study, a modified ground strain model is developed to apply an equivalent earthquake load for the seismic analysis of buried pipelines. The ground strain can be obtained using the ratio of maximum ground velocity to wave propagation velocity. To reflect soil conditions and seismic characteristics, the wave propagation velocity is evaluated by a proposed dispersion curve based on wave energy distribution. In order to verify the developed ground strain model, the results of this study are compared with the observed ground strains of earthquake data. The results of the analyses are compared with those of a dynamic analysis and a response displacement method. Finally various parametric studies considering different properties of pipelines are performed.