• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.5 s.39
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• pp.35-43
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• 2004

Small-scale models have been frequently used for seismic performance tests because of limited testing facilities and economic reasons. However, there are not enough studies on similitude law for analogizing prototype structures accurately with small-scale models, although conventional similitude law based on geometry is not well consistent in the inelastic seismic behavior. When fabricating prototype and small-scale model of reinforced concrete structures by using the same material, added mass is demanded from a volumetric change and scale factor could be limited due to aggregate size. Therefore, it is desirable that different material is used for small-scale models. Thus, a modified similitude law could be derived depending on geometric scale factor, equivalent modulus ratio and ultimate strain ratio. In this study, compressive strength tests are conducted to analyze the equivalent modulus ratio of micro-concrete to normal-concrete. Then, equivalent modulus ratios are divided into multi-phase damage levels, which are basically dependent on ultimate strain level. Therefore, an algorithm adaptable to the pseudodynamic test, considering equivalent multi-phase similitude law based on seismic damage levels, is developed. Test specimens, consisted of prototype structures and 1/5 scaled models as a reinforced concrete column, were designed and fabricated based on the equivalent modulus ratios already defined. Finally quasistatic and pseudodynamic tests on the specimens are carried out using constant and variable modulus ratios, and correlation between prototype and small-scale model is investigated based on their test results. It is confirmed that the equivalent multi-phase similitude law proposed in this study could be suitable for seismic performance tests on small-scale models.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.1
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• pp.17-29
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• 2003

This paper preliminarily investigates the effectiveness of various control systems, such as passive, active, semiactive and hybrid control, for seismic protection of cable-stayed bridges by examining the ASCE first generation benchmark problem for a cable-stayed bridge. This benchm.0.00000ark problem considers the cable-stayed bridge that is scheduled for completion in Missouri, USA In 2003. Seismic considerations were strongly considered in the design of this bridge due to location of the bridge and its critical role as a principal crossing of the Mississippi River. Based on detailed drawings of this cable-stayed bridge, a three-dimensional linearized evaluation model has been developed to represent the complex behavior of the bridge. A set of eighteen evaluation criteria has been developed to evaluate the capability of each control system. In this study, four passive control systems, one active control system, two semiactive control systems and three hybrid control systems are considered. Numerical simulation results show that all the control systems are effective in reducing the responses of the benchmark cable-stayed bridge under the historical earthquakes. To get good performance, however, the passive control systems need quite large control forces compared to other control systems. The simulation results also demonstrate that the passive, semiactive and hybrid control systems are robust to the stiffness uncertainty of the structure. Therefore, the semiactive and hybrid control systems are more appropriate in real applications for full-scale civil infrastructures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.52-58
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• 2016

Recently, interest in structural stability has increased due to earthquakes. Isolation systems can improve seismic ability without harming the functions and appearance of existing and new constructions, and they have established efficiency in foreign country that have experienced earthquakes. In this study, an isolation system is suggested using a natural rubber bearing (NRB) on a stainless water tank for stability assurance in an earthquake. A shaking table test was carried out to evaluate the seismic capacity of a non-isolated water tank and an isolated tank. Displacement meters in the water tank measured the behavior characteristics of the tanks, which were compared using artificial seismic waves of 0.154 g, 0.231 g, 0.341 g, and 0.348 g with water levels of 0.0 m, 1.5 m, and 2.5 m. At 2.5 m, a decrement effect was generally shown in the isolated water tank, and a bigger displacement occurred in the non-isolated water tank than in the isolated one at water levels of 0.0 m and 1.5 m. It is interpreted that the weight of different water levels affects the decrement effect. If seismic reinforcement is done, the isolated bearing should be designed while considering the fluid storage level.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.41-49
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• 2006

Through the 1982 Urahawa-ohi and the 1995 Kobe earthquakes, a number of bridge columns were observed to develop a flexural-shear failure due to the bond slip as a consequence of premature termination of the column longitudinal reinforcement. Because the seismic behavior of RC bridge piers is largely dependent on the performance of the plastic hinge legion of RC bridge piers, it is desirable that the seismic capacity of RC bridge pier is to evaluate as a curvature ductility. The provision for the lap splice of longitudinal steel was not specified in KHBDS(Korea Highway Bridge Design Specification) before the implementation of 1992 seismic design code, but the lap splice of not more than 50%, longitudinal reinforcement was newly allowed in the 2005 version of the KHBDS. The objective of this research is to investigate the distribution and ductility of the curvature of RC bridge column with the lap splice of longitudinal reinforcement in the plastic hinge legion. Six (6) specimens were made in 600 mm diameter with an aspect ratio of 2.5 or 3.5. These piers were cyclically subjected to the quasi-static loads with the uniform axial load of $P=0.1f_{ck}A_g$. According to the slip failure of longitudinal steels of the lap spliced specimen by cyclic loads, the curvatures of the lower and upper parts of the lap spliced region were bigger and smaller than the corresponding paris of the specimen without a lap splice, respectively. Therefore, the damage of the lap spliced test column was concentrated almost on the lower part of the lap spliced region, that appeared io be failed in flexure.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.483-491
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• 2008

There has been much focus on the strong axis steel moment connections after the Northridge earthquake in 1994. However, research studieson the seismic behavior of weak axis moment connections could be hardly found despite the fact that these connection details have been frequently used as seismic details of MRF in Korea. Therefore, the objective of this research is to provide better knowledge on the seismic behavior of weak-axis steel moment connections, which can be widely applicable to many structures with similar characteristics. For this purpose, an experimental program was designed and performed with twotypes of weak-axis steel moment connections, namely the bracket type and WUF-B type, based on the survey of existing field data and literatures. Using the experimental results obtained from the quasi-static cyclic testing of these specimens, structural performances of the joints such as hysteretic curves, maximum strength capacities and the strain of reinforced bars were investigated. From the test results, the bracket-type connection was shown to have more than a 5% story drift capacity, compared with the WUF-B type connection's 4%. These specimens were also shown to have higher strength capacities than the nominal design strength. The bracket-type connection showed a slow strength degradation after maximum strength was researched. However,the WUF-B type connection showed a rapid strength degradation that caused brittle behavior.

• Steel and Composite Structures
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• v.34 no.5
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• pp.743-767
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• 2020

Due to the impressive flexural performance, enhanced compressive strength and more constrained crack propagation, Fibre-reinforced concrete (FRC) have been widely employed in the construction application. Majority of experimental studies have focused on the seismic behavior of FRC columns. Based on the valid experimental data obtained from the previous studies, the current study has evaluated the seismic response and compressive strength of FRC rectangular columns while following hybrid metaheuristic techniques. Due to the non-linearity of seismic data, Adaptive neuro-fuzzy inference system (ANFIS) has been incorporated with metaheuristic algorithms. 317 different datasets from FRC column tests has been applied as one database in order to determine the most influential factor on the ultimate strengths of FRC rectangular columns subjected to the simulated seismic loading. ANFIS has been used with the incorporation of Particle Swarm Optimization (PSO) and Genetic algorithm (GA). For the analysis of the attained results, Extreme learning machine (ELM) as an authentic prediction method has been concurrently used. The variable selection procedure is to choose the most dominant parameters affecting the ultimate strengths of FRC rectangular columns subjected to simulated seismic loading. Accordingly, the results have shown that ANFIS-PSO has successfully predicted the seismic lateral load with R² = 0.857 and 0.902 for the test and train phase, respectively, nominated as the lateral load prediction estimator. On the other hand, in case of compressive strength prediction, ELM is to predict the compressive strength with R² = 0.657 and 0.862 for test and train phase, respectively. The results have shown that the seismic lateral force trend is more predictable than the compressive strength of FRC rectangular columns, in which the best results belong to the lateral force prediction. Compressive strength prediction has illustrated a significant deviation above 40 Mpa which could be related to the considerable non-linearity and possible empirical shortcomings. Finally, employing ANFIS-GA and ANFIS-PSO techniques to evaluate the seismic response of FRC are a promising reliable approach to be replaced for high cost and time-consuming experimental tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.88-98
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• 2011

Masonry structure is a style of building which has been widely applied as residential facilities of low and middle stories, commercial and public facilities etc. But it is possible to destroy by loss of adhesive strength or sliding when lateral forces, such as earthquake, occurs. This study proposes a seismic retrofit method for masonry structure and its seismic performance is demonstrated by shaking table test. Two specimens per each shaking direction were made, having out-of-plane(weak axis) and in-plane(strong axis) direction. External load of 1 ton was also applied for each specimen during the test, to model the behavior of reinforced masonry wall. As a result of shaking table tests, it is shown that the specimen applying the proposed seismic retrofit method showed acceptable behaviors in both of Korea building design criteria(0.14g) and USA seismic criteria suggested by IBC(0.4g). However, it was observed that stiffness of the specimen toward out-of-plane was rapidly decreasing when seismic excitations over 0.14g were loaded. In comparison of relative displacements, maximum relative displacement of specimens which were accelerated toward out-of-plane with 0.4g at once was 29~31% of maximum relative displacement when specimens were gradually accelerated from 0.08g to 0.4g, while the maximum relative displacement of specimens accelerated toward in-plane has similar value in both cases. Therefore, it is concluded that the wall accelerated toward out-of-plane is more affected by hair crack or possible fatigues caused by seismic excitation.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.617-625
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• 2005

The brace is often used to resist lateral force such as that exerted by an earthquake. Because of buckling at bifurcation load, the brace shows unstable hysteretic characteristics in the plastic zone. Therefore, in this study, the brace with damper that consists of slit plates were suggested on the purpose of preventing buckling and increasing plastic deformation capacity. The experimental results regarding the brace member were analyzed and the feasibility was also examined.

• Structural Engineering and Mechanics
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• v.42 no.5
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• pp.645-675
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• 2012

An effective design technique for symmetrical coupled shear walls is presented. Proposed formulation including assumptions and steps with mathematical formulation has been elaborated to make the design technique. An example has been considered to validate the technique with the DRAIN-3DX (1993) and SAP V 10.0.5 (2000) nonlinear programs. Parametric study has also been considered to find out the limitations along with remedial action of this technique. On the other hand, nonlinear static analysis is considered to determine the response reduction factor of coupled shear walls. Finally, it has been concluded in this paper that the proposed design technique can be considered to design the coupled shear walls under seismic motion.

• Structural Engineering and Mechanics
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• v.39 no.5
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• pp.683-701
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• 2011

In this study, inelastic displacement ratios and ductility demands are investigated for SDOF systems with period range of 0.1-3.0 s. with elastoplastic behavior considering soil structure interaction. Earthquake motions recorded on different site conditions such as rock, stiff soil, soft soil and very soft soil are used in analyses. Soil structure interacting systems are modeled with effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by step time integration was adapted in an in-house computer program. Results are compared with those calculated for fixed-base case. A new equation is proposed for inelastic displacement ratio of interacting system ($\tilde{C}_R$) as a function of structural period of interacting system ($\tilde{T}$), strength reduction factor (R) and period lengthening ratio ($\tilde{T}/T$). The proposed equation for $\tilde{C}_R$ which takes the soil-structure interaction into account should be useful in estimating the inelastic deformation of existing structures with known lateral strength.