• Earthquakes and Structures
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• 제17권4호
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• pp.411-424
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• 2019

In this study, a numerical model of a shield tunnel with an assembled segmental lining was built. The seismic response of the segmental lining of the section of the shield tunnel in Line 1 of the Chengdu Metro is analyzed as it passes through the interface of sand-cobble and mudstone layers. To do so, the node-stress seismic-motion input method was used to input the seismic motion measured during the 2008 Wenchuan earthquake, and the joint openings and dislocations associated with the earthquake action were obtained. With reference to the Ethylene-Propylene-Diene Monomer (EPDM) sealing gaskets used in the shield tunnels in the Chengdu Metro, numerical simulation was applied to analyze the contact pressure along the seepage paths and the waterproof property under different joint openings and dislocations. A laboratory test on the elastic sealing gasket was also conducted to study its waterproof property. The test results accord well with the numerical results and the occurrence of water seepage in the section of the shield tunnel in Line 1 of the Chengdu Metro during the 2008 Wenchuan earthquake was verified. These research results demonstrate the deformation of segmental joint under earthquake, also demonstrate the relationship between segmental joint deformation and waterproof property.

• Structural Engineering and Mechanics
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• 제90권6호
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• pp.577-590
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• 2024

Considering the Column-Supported Group Silos (CSGSs) often arranged by rows in practical applications, earthquake responses will be affected by group effect. Since group effect presenting uncertainties, establishing the analytic model and evaluating characteristics of CSGSs seems necessary. This study aimed at providing a simplified method to evaluate seismic performances of the CSGSs. Firstly, the CSGSs with different storage granule heights are used as numerical examples to derive the base shear formula for three-particle dynamic analytical model. Then, the base shear distribution coefficient is defined as the group effect index. The simplified calculation method of the group silos based on the distribution coefficients is proposed. Finally, based on the empty, half, and full granular storage conditions, the empirical design parameters for the group silos system are given by combining finite element simulation with shaking table test. The group effect of storage granule heights of group silos on its frequency and base shear are studied by comparative analysis between group silos and independent single silo. The results show that the frequency of CSGSs decreases with the increasing weight of the stored granule. The connection between the column top and silo bottom plate is vulnerable, and structural measures should be strengthened to improve its damage resistance. In case of different storage granule heights, distribution coefficients are effective to reconstruction the group effect. The complex calculations of seismic response for CSGSs can be avoided by adopting the empirical distribution coefficients obtained in this study. The proposed method provides a theoretical reference for evaluation on the seismic performances of the CSGSs.

• Structural Engineering and Mechanics
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• 제48권2호
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• pp.151-171
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• 2013

The current paper presents the numerical blind prediction of nonlinear seismic response of two full-scale, three dimensional, one-story reinforced concrete structures subjected to bidirectional earthquake simulations on shaking table. Simulations were carried out at the laboratories of LNEC (Laboratorio Nacional de Engenharia Civil) in Lisbon, Portugal. The study was motivated by participation in the blind prediction contest of shaking table tests, organized by the challenge committee of the 15th World Conference on Earthquake Engineering. The test specimens, geometrically identical, designed for low and high ductility levels, were subjected to subsequent earthquake motions of increasing intensity. Three dimensional nonlinear analytical models were implemented and subjected to the input base motions. Reasonably accurate reproduction of the measured displacement response was obtained through appropriate modeling. The goodness of fit between analytical and measured results depended on the details of the analytical models.

• Earthquakes and Structures
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• 제7권5호
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• pp.627-645
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• 2014

Using OpenSees as a framework, constitutive models of reinforced, prestressed and prestressed steel fiber concrete found by the panel tests have been implemented into a finite element program called Simulation of Concrete Structures (SCS) to predict the seismic behavior of shear-critical reinforced and prestressed concrete structures. The developed finite element program was validated by tests on prestressed steel fiber concrete beams under monotonic loading, post tensioned precast concrete column under reversed cyclic loading, framed shear walls under reversed cyclic loading or shaking table excitations, and a seven-story wall building under shake table excitations. The comparison of analytical results with test outcomes indicates good agreement.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.473-480
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• 1998

The substructuring pseudodynamic test is a hybrid testing method consisting of a numerical simulation of the earthquake response of an analytical model and a loading test of a specimen. The substructuring pseudodynamic testing technique has been applied to various seismic experiments since it has advantages over the shaking table test to study dynamic behaviors of relatively large scale structures. However, experimental errors are inevitable in substructuring pseudodynamic testing. Some of these errors can be monitored during the test, but, due to limitations in control system, they cannot be eliminated. For example, one cannot control exactly the displacements that are actually imposed on the structures at each time step. This paper focuses on a technique to minimize the cumulative effect of such control errors for MDOF system. For this purpose, the modified posterior adjustment of the time increment from a target value $\Delta$t$_{n}$ to an adjusted value is performed to minimize the effect of the control errors for MDOF system.for MDOF system.

• Earthquakes and Structures
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• 제9권4호
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• pp.699-718
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• 2015

The effect of reinforcing concrete members with high strength steel bars with yield strength up to 600 MPa on the overall seismic behavior of concrete moment frames was studied experimentally and numerically. Three geometrically identical plane frame models with two bays and two stories, where one frame model was reinforced with hot rolled bars (HRB) with a nominal yield strength of 335 MPa and the other two by high strength steel bars with a nominal yield strength of 600 MPa, were tested under simulated earthquake action considering different axial load ratios to investigate the hysteretic behavior, ductility, strength and stiffness degradation, energy dissipation and plastic deformation characteristics. Test results indicate that utilizing high strength reinforcement can improve the structural resilience, reduce residual deformation and achieve favorable distribution pattern of plastic hinges on beams and columns. The frame models reinforced with normal and high strength steel bars have comparable overall deformation capacity. Compared with the frame model subjected to a low axial load ratio, the ones under a higher axial load ratio exhibit more plump hysteretic loops. The proved reliable finite element analysis software DIANA was used for the numerical simulation of the tests. The analytical results agree well with the experimental results.

• Earthquakes and Structures
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• 제6권6호
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• pp.627-646
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• 2014

Adobe is one of the oldest construction materials that is still used in many seismic countries, and different construction techniques are found around the world. The adobe material is characterized as a brittle material; it has acceptable compression strength but it has poor performance under tensile and shear loading conditions. Numerical modelling is an alternative approach for studying the nonlinear behaviour of masonry structures such as adobe. The lack of a comprehensive experimental database on the adobe material properties motivated the study developed here. A set of a reference material parameters for the adobe were obtained from a calibration of numerical models based on a quasi-static cyclic in-plane test on full-scale adobe wall representative of the typical Peruvian adobe constructions. The numerical modelling, within the micro and macro modelling approach, lead to a good prediction of the in-plane seismic capacity and of the damage evolution in the adobe wall considered.

• Smart Structures and Systems
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• 제22권4호
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• pp.441-457
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• 2018

Characteristic parameter values of seismic isolators deviate from their nominal design values due to uncertainties and/or errors in their material properties and element dimensions, etc. Deviations may increase over service life due to environmental effects and service conditions. For accurate evaluation of the seismic safety level, all such effects, which would result in deviations in the structural response, need to be taken into account. In this study, the sensitivity of the probability of failure of the structures equipped with nonlinear base isolation systems to the uncertainties in various isolation system characteristic parameters is investigated in terms of various isolation system and superstructure response parameters in the context of a realistic three-dimensional base-isolated building model via Monte Carlo Simulations. The inherent record-to-record variability nature of the earthquake ground motions is also taken into account by carrying out analyses for a large number of ground motion records which are classified as those with and without forward-directivity effects. Two levels of nominal isolation periods each with three different levels of uncertainty are considered. Comparative plots of cumulative distribution functions and related statistical evaluation presented here portray the potential extent of the deviation of the structural response parameters resulting from the uncertainties and the uncertainty levels considered, which is expected to be useful for practicing engineers in evaluating isolator test results for their projects.

• Structural Engineering and Mechanics
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• 제51권4호
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• pp.663-683
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• 2014

In order to study the dynamic failure mechanism and aseismic measure for high concrete gravity dam under earthquake, the comparative models experiment on the shaking table was conducted to investigate the dynamic damage response of concrete gravity dam with and without the presence of reinforcement and evaluate the effectiveness of the strengthening measure. A new model concrete was proposed and applied for maintaining similitude with the prototype. A kind of extra fine wires as a substitute for rebar was embedded in four-points bending specimens of the model concrete to make of reinforced model concrete. The simulation of reinforcement concrete of the weak zones of high dam by the reinforced model concrete meets the similitude requirements. A tank filled with water is mounted at the upstream of the dam models to simulate the reservoir. The Peak Ground Acceleration (PGA) that induces the first tensile crack at the head of dam is applied as the basic index for estimating the overload capacity of high concrete dams. For the two model dams with and without strengthening tested, vulnerable parts of them are the necks near the crests. The results also indicate that the reinforcement is beneficial for improving the seismic-resistant capacity of the gravity dam.

• Steel and Composite Structures
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• 제31권1호
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• pp.53-67
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• 2019

This study presents finite element analysis (FEA) on a Y-type perfobond rib shear connection using Abaqus software. The performance of a shear connection is evaluated by conducting a push-out test. However, in practice, it is inefficient to verify the performance by conducting a push-out test with regard to all design variables pertaining to a shear connector. To overcome this problem, FEA is conducted on various shear connectors to accurately estimate the shear strength of the Y-type perfobond rib shear connection. Previous push-out test results for 14 typical push-out test specimens and those obtained through FEA are compared to analyze the shear behavior including consideration of the design variables. The results show that the developed finite element model successfully reflects the effects of changes in the design variables. In addition, using the developed FEA model, the shear resistance of a stubby Y-type perfobond rib shear connector is evaluated based on the concrete strength and transverse rebar size variables. Then, the existing shear resistance formula is upgraded based on the FEA results.