• Earthquakes and Structures
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• v.13 no.4
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• pp.409-419
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• 2017

In order to analyze the vibration control effect of viscous damper in the concrete archaized buildings with lintel-column joints under seismic action, 3 specimens were tested under dynamic excitation. Two specimens with viscous damper were defined as the controlled component and one specimen without viscous damper was specified as the non-controlled component. The loading process and failure patterns were obtained from the test results. The failure characteristics, skeleton curves and mechanical behavior such as the load-displacement hysteretic loops, load carrying capacity, degradation of strength and rigidity, ductility and energy dissipation of the joints were analyzed. The results indicate that the load-bearing capacity of the controlled component is significantly higher than that of the non-controlled component. The former component has an average increase of 27.4% in yield load and 22.4% in ultimate load, respectively. Meanwhile, the performance of displacement ductility and the ability of energy dissipation for the controlled component are superior to those of the non-controlled component as well. Compared with non-controlled component, equivalent viscous damping coefficients are improved by 27.3%-30.8%, the average increase is 29.0% at ultimate load for controlled component. All these results reflect that the seismic performance of the controlled component is significantly better than that of the non-controlled component. These researches are helpful for practical application of viscous damper in the concrete archaizing buildings with lintel-column joints.

• Structural Engineering and Mechanics
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• v.14 no.3
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• pp.287-306
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• 2002

The assessment of structural performance of transfer structures under potential seismic actions is presented. Various seismic assessment methodologies are used, with particular emphasis on the accurate modelling of the higher mode effects and the potential development of a soft storey effect in the mega-columns below the transfer plate (TP) level. Those methods include response spectrum analysis (RSA), manual calculation, pushover analysis (POA) and equivalent static load analysis (ESA). The capabilities and limitations of each method are highlighted. The paper aims, firstly, to determine the appropriate seismic assessment methodology for transfer structures using these different approaches, all of which can be undertaken with the resources generally available in a design office. Secondly, the paper highlights and discusses factors influencing the response behaviour of transfer structures, and finally provides a general indication of their seismic vulnerability. The representative Hong Kong building considered in this paper utilises a structural system with coupled shear walls and moment resisting portal-frames, above and below the TP, respectively. By adopting the wind load profile stipulated in the Code of Practice on Wind Effects: Hong Kong-1983, all the structural members are sized and detailed according to the British Standards BS8110 and the current local practices. The seismic displacement demand for the structure, when built on either rock or deep soil sites, was determined in a companion paper. The lateral load-displacement characteristic of the building, determined herein from manual calculation, has indicated that the poor ductility (brittle nature) of the mega-columns, due mainly to the high level of axial pre-compression as found from the analysis, cannot be effectively alleviated solely by increasing the quantity of confinement stirrups. The interstorey drift demands at lower and upper zones caused by seismic actions are found to be substantially higher than those arising from wind loads. The mega-columns supporting the TP and the coupling beams at higher zones are identified to be the most vulnerable components under seismic actions.

• Earthquakes and Structures
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• v.24 no.6
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• pp.415-428
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• 2023

Low-cost techniques with seismic isolation performance and excellent resilience need to be explored in the case of rural low-rise buildings because of the limited buying power of rural residents. As an inexpensive and eco-friendly isolation bearing, scrap tire pads (STPs) have the issue of poor resilience. Thus, a seismic isolation system under a column (SISC) integrated with STP needs to be designed for the seismic protection of low-rise rural buildings. The SISC, which is based on a simple exterior design, maintains excellent seismic performance, while the mechanical behavior of the internal STP provides elastic resilience. The horizontal behaviors of the SISC are studied through load tests, and its mechanical properties and the intrinsic mechanism of the reset ability are discussed. Results indicate that the average residual displacement ratio was 24.59%, and the reset capability was enhanced. Comparative experimental and finite element analysis results also show that the load-displacement relationship of the SISC was essentially consistent. The dynamic characteristics of isolated and fixed-base buildings were compared by numerical assessment of the response control effects, and the SISC was found to have great seismic isolation performance. SISC can be used as a low-cost base isolation device for rural buildings in developing countries.

• Earthquakes and Structures
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• v.23 no.1
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• pp.101-113
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• 2022

A new type of fabricated subway station construction technology can effectively solve these problems. For a new type of metro structure form, it is necessary to clarify its mechanical properties, especially the seismic performance. A soil-structure elastoplastic finite element model is established to perform three-dimensional nonlinear dynamic time-history analysis based on the first fabricated station structure-Yuanjiadian station of Changchun Metro Line 2, China. Firstly, the nonlinear seismic response characteristics of the fabricated and cast-in-place subway stations under different seismic wave excitations are compared and analyzed. Then, a comprehensive analysis of several important parameters that may affect the seismic response of fabricated subway stations is given. The results show that the maximum plastic strain, the interlayer deformation, and the internal force of fabricated station structures are smaller than that of cast-in-place structure, which indicates that the fabricated station structure has good deformation coordination capability and mechanical properties. The seismic responses of fabricated stations were mainly affected by the soil-structure stiffness ratio, the soil inertia effect, and earthquake load conditions rarely mentioned in cast-in-place stations. The critical parameters have little effect on the interlayer deformation but significantly affect the joints' opening distance and contact stress, which can be used as the evaluation index of the seismic performance of fabricated station structures. The presented results can better understand the seismic responses and guide the seismic design of the fabricated station.

• Earthquakes and Structures
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• v.9 no.4
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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.

• Journal of Korean Association for Spatial Structures
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• v.6 no.2 s.20
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• pp.93-105
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• 2006

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of twelve one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The specimens adopted are two-dimensional (2D) hollow concrete block masonry walls with different parameters such as shear span ratio, inflection point and percent of reinforcement in confining columns and walls. Test results obtained for each specimen include cracking patterns, load-deflection curve, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.2
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• pp.77-83
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• 2024

The design shear strength equations of RC shear walls have been developed based on their performance under in-plane (IP) loads, thereby failing to account for the potential performance degradation of shear strength when subjected to simultaneous out-of-plane (OOP) loading. Most of the previous experimental studies on RC walls have been conducted in one direction under quasi-static conditions, and due to the difficulty in experimental planning, there is a lack of research on cyclic loading and results under multi-axial loading conditions. During an earthquake, shear walls may yield earlier than their design strength or fail unexpectedly when subjected to multi-directional forces, deviating from their intended failure mode. In this paper, nonlinear analysis in finite element models was performed based on the results of cyclic loading experiments on reinforced concrete shear walls of auxiliary buildings. To investigate the reduction trend in IP shear capacity concerning the OOP load ratio, parametric analysis was conducted using the shear wall FEM. The analysis results showed that as the magnitude of the OOP load increased, the IP strength decreased, with a more significant effect observed as the size of the opening increased. Thus, the necessity to incorporate this strength reduction as a factor for the OOP load effect in the wall design strength equation should be discussed by performing various parametric studies.

• Structural Engineering and Mechanics
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• v.51 no.3
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• pp.487-502
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• 2014

In buildings structures, the flexural stiffness reduction of beams and columns due to concrete cracking plays an important role in the nonlinear load-deformation response of reinforced concrete structures under service loads. Most Seismic Design Codes do not precise effective stiffness to be used in seismic analysis for structures of reinforced concrete elements, therefore uncracked section properties are usually considered in computing structural stiffness. But, uncracked stiffness will never be fully recovered during or after seismic response. In the present study, the effect of concrete cracking on the lateral response of structure has been taken into account. Totally 120 cases of 3 Dimensional Dynamic Analysis which considers the real and accidental torsional effects are performed using ETABS to determine the effective structural system across the height, which ensures the performance and the economic dimensions that achieve the saving in concrete and steel amounts thus achieve lower cost. The result findings exhibits that the dual system was the most efficient lateral load resisting system based on deflection criterion, as they yielded the least values of lateral displacements and inter-storey drifts. The shear wall system was the most economical lateral load resisting compared to moment resisting frame and dual system but they yielded the large values of lateral displacements in top storeys. Wall systems executes tremendous stiffness at the lower levels of the building, while moment frames typically restrain considerable deformations and provide significant energy dissipation under inelastic deformations at the upper levels. Cracking found to be more impact over moment resisting frames compared to the Shear wall systems. The behavior of various lateral load resisting systems with respect to time period, mode shapes, storey drift etc. are discussed in detail.

• Earthquakes and Structures
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• v.26 no.6
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• pp.477-487
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• 2024

The interaction between multiple structures through the supporting soil media, known as structure-soil-structure interaction (SSSI), has become an increasingly important issue due to rapid urbanization. There is a need to investigate the effect of SSSI on the structural response of buildings compared to non-interaction analysis (NIA) and soil-structure interaction (SSI) analysis. In the present study, two identical 4-bay×4-bay, three-story RCC buildings are modeled adjacent to each other with a soil domain beneath it to investigate the effect of SSSI on the forces experienced by footings under gravity and seismic load cases. The ANSYS software is used for modeling various non-interaction and interaction models which work on the principle of FEM. The results indicate that in most of the footings, the SSSI effect causes a significant redistribution of forces compared to SSI and NIA under both gravity and seismic load cases. The maximum interaction effect is observed on the footings that are closer to the adjacent building. The axial force, shear force and bending moment values on these footings show that SSI causes a significant increase in these values compared to non-interaction analysis but the presence of adjacent building relieves these forces significantly.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.9
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• pp.862-873
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• 2007

Energy dissipation devices can be considered as an alternative for the seismic performance enhancement of existing structures based on the strengthened seismic design code. In this study, seismic response mitigation effects of friction dampers are investigated through the shaking table test of a full scale 3 story building structure. Frist, the bilinear force-displacement relationship of a structure-brace-friction damper system and the effect of brace-friction damper on the increase of frequency and damping ratio are identified. Second, frequency, displacement, and torque dependent characteristics of the friction damper are investigated by using harmonic load excitation tests. Finally, the shaking table tests are performed for a full scale 3 story steel frame. System identification results using random signal excitation indicated that brace-friction damper increased structural damping ratio and frequency, and El Centro earthquake test showed that brace-friction damper reduced the peak displacement and acceleration significantly. In particular, it was observed that the damping effect due to friction damper becomed obvious when the structure was excited by more intensive load causing frequent slippage of the friction dampers.