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CONTENTS
Volume 16, Number 1, January 2019
 

Abstract
To provide a simplified method for the base isolation design of LNG tanks, such as 16x104 m3 LNG tanks, we conducted a derivation and calculation example analysis of the dynamic response of the base isolation of LNG storage tanks, using dynamic response analysis theory with consideration of pile-soil interaction. The ADINA finite element software package was used to conduct the numerical simulation analysis, and compare it with the theoretical solution. The ground-shaking table experiment of LNG tank base isolation was carried out simultaneously. The results show that the pile-soil interaction is not obvious under the condition of base isolation. Comparing base isolation to no isolation, the seismic response clearly decreases, but there is less of an effect on the shaking wave height after adopting pile top isolation support. This indicates that the basic isolation measures cannot control the wave height. A comparison of the shaking table experiment with the finite element solution and the theoretical solution shows that the finite element solution and theoretical solution are feasible. The three experiments are mutually verified.

Key Words
LNG storage tank; base isolation; pile-soil; vibration table experiment

Address
Jiangang Sun, Lifu Cui, Xiang Li, Zhen Wang, Weibing Liu: College of Civil Engineering, Dalian Minzu University, Dalian, China
Yuan Lv: Institute of Road and Bridge Engineering, Dalian Maritime University, Dalian, China

Abstract
This article investigates the response of Integral Abutment Bridges (IAB) when subjected to a sequence of seasonal thermal loading of the deck followed by ground seismic shaking in the longitudinal direction. Particular emphasis is placed on the effect of pre-seismic thermal Soil-Structure Interaction (SSI) on the seismic performance of the IAB, as well as on the ability of various backfills configurations, to minimize the unfavorable SSI effects. A series of two-dimensional numerical analyses were performed for this purpose, on a complete backfill-integral bridge-foundation soil system, subjected to seasonal cyclic thermal loading of the deck, followed by ground seismic shaking, employing ABAQUS. Various backfill configurations were investigated, including conventional dense cohesionless backfills, mechanically stabilized backfills and backfills isolated by means of compressive inclusions. The responses of the investigated configurations, in terms of backfill deformations and earth pressures, and bridge resultants and displacements, were compared with each other, as well as with relevant predictions from analyses, where the pre-seismic thermal SSI effects were neglected. The effects of pre-seismic thermal SSI on the seismic response of the coupled IAB-soil system were more evident in cases of conventional backfills, while they were almost negligible in case of IAB with mechanically stabilized backfills and isolated abutments. Along these lines, reasonable assumptions should be made in the seismic analysis of IAB with conventional sand backfills, to account for pre-seismic thermal SSI effects. On the contrary, the analysis of the SSI effects, caused by thermal and seismic loading, can be disaggregated in cases of IAB with isolated backfills.

Key Words
bridge; long-span; integral abutment; thermal loads; seismic; soil-structure interaction

Address
Grigorios Tsinidis: Department of Engineering, University of Sannio, Piazza Roma 21, Benevento, 82100, Italy; Vienna Consulting Engineers ZT GmbH, Untere Viaduktgasse 2, 1030, Vienna, Austria
Maria Papantou: AECOM, Structures & Bridges, One Trinity Gardens, Broad Chare, Newcastle upon Tyne, NE1 2HF, UK
Stergios Mitoulis: Department of Civil and Environmental Engineering, FEPS, University of Surrey, Guildford, GU2 7XH, UK

Abstract
A three-step screening process is presented in this article for selection of consistent earthquake records in which number of suitable ground motions is quickly screened and reduced to a handful number. Records that remain at the end of this screening process considerably reduce the dispersion of structural responses. Then, an effective method is presented for spectral matching and modification of the selected records. Dispersion of structural responses is explored using different statistical measures for each scaling procedure. It is shown that the Uniform Design Method, presented in this study for scaling of earthquake records, results in most cases in the least dispersion measure.

Key Words
ground motion selection; screening process; modification; nonlinear time history analysis; scatter of response

Address
Farhad Behnamfar: Department of Civil Engineering, Isfahan University of Technology, Isfahan 8415683111, Iran
Mehdi Talebi Velni: Senior Structural Engineer, Chaloos, Iran

Abstract
Reinforced Concrete (RC) shear walls are widely used in Nuclear power plants as effective lateral force resisting elements of the structure and these may experience nonlinear behavior for higher earthquake demand. Short shear walls of aspect ratio less than 1.5 generally experience combined shear flexure interaction. This paper presents the results of the displacement-controlled experiments performed on six RC short shear walls with varying aspect ratios (1, 1.25 and 1.5) for monotonic and reversed quasi-static cyclic loading. Simulation of the shear walls is then carried out by Finite element modeling and also by macro modeling considering the coupled shear and flexure behaviour. The shear response is estimated by softened truss theory using the concrete model given by Vecchio and Collins (1994) with a modification in softening part of the model and flexure response is estimated using moment curvature relationship. The accuracy of modeling is validated by comparing the simulated response with experimental one. Moreover, based on the experimental work a multi-linear hysteretic model is proposed for short shear walls. Finally ultimate load, drift, ductility, stiffness reduction and failure pattern of the shear walls are studied in details and hysteretic energy dissipation along with damage index are evaluated.

Key Words
short shear walls; hysteretic model; cyclic; ductility; experiments

Address
T. Nagender, Y.M. Parulekar: Reactor Safety Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India
G. Appa Rao: Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu-600036, India

Abstract
The finite solutions of deflection and the corresponding in-plane stress values of the graded sandwich shallow shell structure are computed in this research article via a higher-order polynomial shear deformation kinematics. The shell structural equilibrium equation is derived using the variational principle in association with a nine noded isoprametric element (nine degrees of freedom per node). The deflection values are computed via an own customized MATLAB code including the current formulation. The stability of the current finite element solutions including their accuracies have been demonstrated by solving different kind of numerical examples. Additionally, a few numerical experimentations have been conducted to show the influence of different design input parameters (geometrical and material) on the flexural strength of the graded sandwich shell panel including the geometrical configurations.

Key Words
functionally graded sandwich panels; HOSDT; variational principle; FEM

Address
Sushmita Dash: Department of Mechanical Engineering, GITA, Bhubaneswar, 752054, Odisha, India
Kulmani Mehar: Mechanical Engineering Department, MITS, Madanapalle, Andra Pradesh, India
Nitin Sharma: School of Mechanical Engineering, KIIT, Bhubaneswar, 751024, Odisha, India
Trupti Ranjan Mahapatra: Department of Production Engineering, Veer Surendra Sai University of Technology (VSSUT), Burla, 768018, Odisha, India
Subrata Kumar Panda: Department of Mechanical Engineering, NIT, Rourkela, 769008, Odisha, India

Abstract
As the residual displacement and/or drift demands are commonly used for seismic assessment of buildings, the estimation of these values play a very critical role through earthquake design philosophy. The residual displacement estimation of fixed base structures has been the topic of numerous researches up to now, but the effect of soil flexibility is almost always omitted. In this study, residual displacement demands are investigated for SDOF systems with period range of 0.1-3.0 s for nearfield and far-field ground motions for both fixed and interacting cases. The elastoplastic model is used to represent nondegrading structures. Based on time history analyses, a new simple yet effective equation is proposed for residual displacement demand of any system whether fixed base or interacting as a function of structural period, lateral strength ratio and spectral displacement.

Key Words
residual displacement; soil structure interaction; spectral displacement; lateral strength ratio

Address
Müberra Eser Aydemir and Cem Aydemir: Department of Civil Engineering, Istanbul Aydin University, Istanbul, Turkey

Abstract
The seismic behavior of PRC coupling beam-hybrid coupled shear wall system is analyzed by using the finite element software ABAQUS. The stress distribution of steel plate, reinforcing bar in coupling beam, reinforcing bar in slab and concrete is investigated. Meanwhile, the plastic hinges developing law of this hybrid coupled shear wall system is also studied. Further, the effect of coupling ratio, section dimensions of coupling beam, aspect ratio of single shear wall, total height of structure and the role of slab on the seismic behavior of the new structural system. A fitting formula of plate characteristic values for PRC coupling beams based on different displacement requirements is proposed through the experimental date regression analysis of PRC coupling beams at home and abroad. The seismic behavior control method for PRC coupling beam-hybrid coupled shear wall system is proposed based on the continuous connection method and through controlling the coupling ratio, the roof displacement, story drift angle of hybrid coupled shear wall system, displacement ductility of coupling beam.

Key Words
PRC coupling beam-hybrid coupled shear wall system; coupling ratio; finite element analysis; seismic behavior; displacement-based seismic design method

Address
Jianbo Tian, Youchun Wang, Zheng Jian, Shen Li and Yunhe Liu: of Civil Engineering and Architecture, Xi\'an University of Technology, Xi\'an Beilin District, Jinhua Road No. 5, 710048, China; State Key Laboratory Base of Eco-hydraulic Engineering in Arid Area, Xi\'an University of Technology, Xi\'an Beilin District, Jinhua Road No. 5, 710048, China

Abstract
The frame structures investigated in this paper is composed of Concrete encased columns with L-shaped steel section and steel beams. The seismic behavior of this structural system is studied through experimental and numerical studies. A 2-bay, 3-story and 1/3 scaled frame specimen is tested under constant axial loading and cyclic lateral loading applied on the column top. The load-displacement hysteretic loops, ductility, energy dissipation, stiffness and strength degradation are investigated. A typical failure mode is observed in the test, and the experimental results show that this type of framed structure exhibit a high strength with good ductility and energy dissipation capacity. Furthermore, finite element analysis software Perform-3D was conducted to simulate the behavior of the frame. The calculating results agreed with the test ones well. Further analysis is conducted to investigate the effects of parameters including concrete strength, column axial compressive force and steel ratio on the seismic performance indexes, such as the elastic stiffness, the maximum strength, the ductility coefficient, the strength and stiffness degradation, and the equivalent viscous damping ratio. It can be concluded that with the axial compression ratio increasing, the load carrying capacity and ductility decreased. The load carrying capacity and ductility increased when increasing the steel ratio. Increasing the concrete grade can improve the ultimate bearing capacity of the structure, but the ductility of structure decreases slightly.

Key Words
frame structure; concrete encased column; L-shaped steel section; seismic behavior

Address
Lei Zeng, Wenting Ren, Zhengtao Zou, Yiguang Chen, Wei Xie and Xianjie Li: School of Urban Construction, Yangtze University, Jingzhou, Hubei, China

Abstract
This study, analyses the seismic response for a rigid massless square foundation resting on a viscoelastic soil layer limited by rigid bedrock. The foundation is subjected either to externally applied forces or to obliquely incident seismic body or surface harmonic seismic waves P, SV and SH. A 3-D frequency domain BEM formulation in conjunction with the thin layer method (TLM) is adapted here for the solution of elastodynamic problems and used for obtained the seismic response. The mathematical approach is based on the method of integral equations in the frequency domain using the formalism of Green\'s functions (Kausel and Peck 1982) for layered soil, the impedance functions are calculated by the compatibility condition. In this study, The key step is the characterization of the soil-foundation interaction with the input motion matrix. For each frequency the impedance matrix connects the applied forces to the resulting displacement, and the input motion matrix connects the displacement vector of the foundation to amplitudes of the free field motion. This approach has been applied to analyze the effect of soil-structure interaction on the seismic response of the foundation resting on a viscoelastic soil layer limited by rigid bedrock.

Key Words
BEM-TLM; soil structure interaction; soil layer; harmonic waves

Address
Salah Messioud: LGCE, University of Jijel, BP 98 Ouled Aissa, 18000 Jijel, Algeria
Badredine Sbartai: Department of Civil Engineering, University of Badji Mokhtar-Annaba, Algeria
Daniel Dias: School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei, China;
Geotechnical Expert, Antea Group, 92160 Antony, France

Abstract
When a structural wall is subjected to multi-directional ground motion, torsion-induced cracks degrade the stiffness of the wall. The effect of torsion should not be neglected. As a main lateral load resisting member, reinforced concrete (RC) structural wall has been widely studied under the combined action of bending and shear. Unfortunately, its seismic behavior under a combined action of torsion, bending and shear is rarely studied. In this study, torsional performances of the RC structural walls under the combined action is assessed from a comprehensive parametrical study. Finite element (FE) models are built and calibrated by comparing with the available experimental data. The study is then carried out to find out the critical design parameter affecting the torsional stiffness of RC structural walls, including the axial load ratio, aspect ratio, leg-thickness ratio, eccentricity of lateral force, longitudinal reinforcement ratio and transverse reinforcement ratio. Besides, to facilitate the application in practice, an empirical equation is developed to estimate the torsional stiffness of RC rectangular structural walls conveniently, which is found to agree well with the numerical results of the developed FE models.

Key Words
reinforced concrete; rectangular structural walls; finite element model; torsional stiffness

Address
Da Luo: College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, P.R. China
Chaolie Ning: Shanghai Institute of Disaster Prevention and Relief, Tongji University, Shanghai 200092, P.R. China
Bing Li: School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore


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