• Smart Structures and Systems
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• v.4 no.3
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• pp.319-342
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• 2008

Identification of the nonlinear hysteretic behavior of a reinforced concrete (RC) bridge pier subjected to earthquake loads is carried out based on acceleration measurements of the earthquake motion and bridge responses. The modified Takeda model is used to describe the hysteretic behavior of the RC pier with a small number of parameters, in which the nonlinear behavior is described in logical forms rather than analytical expressions. Hence, the modified extended Kalman filter is employed to construct the state transition matrix using a finite difference scheme. The sequential modified extended Kalman filter algorithm is proposed to identify the unknown parameters and the state vector separately in two steps, so that the size of the problem for each identification procedure may be reduced and possible numerical problems may be avoided. Mode superposition with a modal sorting technique is also proposed to reduce the size of the identification problem for the nonlinear dynamic system with multi-degrees of freedom. Example analysis is carried out for a continuous bridge with a RC pier subjected to earthquake loads in the longitudinal and transverse directions.

• Structural Monitoring and Maintenance
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• v.7 no.4
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• pp.319-344
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• 2020

Inverse analysis of non-linear reinforced concrete bridge pier using recursive Gaussian filtering for in-situ condition assessment is the main theme of this work. For this purpose, minimum variance unbiased estimation using unscented sigma points is adopted here. The uniqueness of this inverse analysis lies in its approach for strain based updating of engineering demand parameters, where appropriate bound and constrained conditions are introduced to ensure numerical stability and convergence. In this analysis, seismic input is also identified, which is an added advantage for the structures having no dedicated sensors for earthquake measurement. First, the proposed strategy is tested with a simulated example whose hysteretic properties are obtained from the slow-cyclic test of a frame to investigate its efficiency and accuracy. Finally, the experimental test data of a full-scale bridge pier is used to study its in-situ condition in terms of Park & Ang damage index. Overall the study shows the ability of the augmented minimum variance unbiased estimation based recursive time-marching algorithm for non-linear system identification with the aim to estimate the engineering damage parameters that are the fundamental information necessary for any future decision making for retrofitting/rehabilitation.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.121-124
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• 2008

Fast construction of bridge substructures is a new trend of bridge design. A precast pier system with bonded prestressing bars was proposed. In this paper, quasi-static tests on precast prestressed piers were conducted to evaluate the seismic behavior of the precast piers with bonded prestressing bars. In order to strengthen the shear strength of the joints between column segments, steel tubes filled with mortar were used. Displacement ductility and energy dissipation capacity of the precast piers were evaluated. The suggested precast pier system showed better seismic performance than the required ductility. Based on the research results, an example bridge pier for light-railway lines was designed and design considerations were discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.63-66
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• 2005

Six RC pier were tested under a constant axial load and a cyclically reversed horizontal load to investigate the performance of RC piers used in the high strength concrete and the high strength rebar. It is designed with a hollow section according to the Korean Bridge Design Standard. The variables of the test were concrete strength, rebar strength, a ratio of lap splice and a ratio of transvere rebar. The test results show that the performance of a RC Pier; failure mode, crack pattern, maximum load and ductility.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.147-157
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• 2018

The basis of capacity design has been explicitly or implicitly regulated in most bridge design specifications. It is to guarantee ductile failure of entire bridge system by preventing brittle failure of pier members and any other structural members until the columns provides fully enough plastic rotation capacity. Brittle shear is regarded as a mode of failure that should be avoided in reinforced concrete bridge pier design. To provide ductility behavior of column, the one of important factors is that flexural hinge of column must be detailed to ensure adequate and dependable shear strength and deformation capacity. Eight small scale circular reinforced concrete columns were tested under cyclic lateral load with 4.5 aspect ratio. The test variables are longitudinal steel ratio, transverse steel ratio, and axial load ratio. Eight flexurally dominated columns were tested. In all specimens, initial flexural-shear cracks occurred at 1.5% drift ratio. The multiple flexural-shear crack width and length gradually increased until the final stage. The angles of the major inclined cracks measured from the vertical column axis ranged between 42 and 48 degrees. In particular, this study focused on assessing transverse reinforcement contribution to the column shear strength. Transverse reinforcement contribution measured during test. Each three components of transverse reinforcement contribution, axial force contribution and concrete contribution were investigated and compared. It was assessed that the concrete stresses of all specimen were larger than stress limit of Korea Bridge Design Specifications.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.533-542
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• 2014

In design standards such as AASHTO LRFD and Korea Highway Bridge Design, the dynamic behaviors under the impact loading has not been considered and it recommends of using a static force for designing bridge column against vehicle collisions. Accordingly, in this study, models of vehicle collisions to concrete bridge column were developed with various boundary conditions in order to take into account dynamic behaviour of the column. Cargo trucks of 10tons, 16tons and 38tons were selected and a typical type of concrete bridge pier column along the Kyungbu highway in Korea was selected for this study. Results from this study indicate that the static load specified in the design standards are too small compared to results obtained in this study. It was also found that a consideration of the bridge superstructure allowed smaller damages of concrete bridge pier column under truck impact loadings. Furthermore, a comparison study of direct impact analysis of vehicle to bridge-column with in-direct impact analysis using load-time history functions was performed. The in-direct impact analysis shows that the use of load-time history graph improves the computational cost up to 92% and predict the behaviors of the bridge column under the impact loadings well. The obtained load-time history graph could be easily applied to several existing models.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.671-676
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• 1999

Because of relatively heavy dead weight of concrete itself and unavoidable heat of massive concrete in bridge piers, circular hollow columns are widely used in Korean highway bridges. Since the occurrence of 1995 Kobe earthquake, there have been much concerns about seismic design for various infrastructures, inclusive of bridge structures. It is, however, understood that there are not much research works for nonlinear behavior of circular hollow columns subjected to earthquake motions. The ultimate of this experimental research is investigate nonlinear behavior of circular hollow reinforced concrete bridge piers under the quasi-static cyclic load, and then to enhance their ductility by strengthening the plastic hinge region with glassfiber sheets. It is concluded from quasi-static tests for 7 bridge piers that energy dissipation capacity and curvatures for a given displacement ductility factor $\{\mu}=frac{\Delta}{\Delta_y}$are about 20% higher for the seismically designed columns and about 70% higher for the retrofitted piers than the nonseismically designed columns in a conventional way.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.69-72
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• 2008

The so-called Pier-Shafts system which consists of the continuous column and shaft is often used to support the highway bridge structure because of advantages in easy construction and low cost. In the earthquake region, the Pier-Shafts system undergoes large displacements and represents a nonlinear behavior under the lateral seismic loading. The soil-pile interaction should be considered for more accurate analysis of the Pier-Shafts system. In this study, a transverse response of a reinforced concrete Pier-Shafts system inside multi-layered soil medium is predicted using a finite element program which adopts an elasto-plastic interface model for the interface behavior between the shaft and the soil. Then, seismic analysis is performed to evaluate the performance of Pier-Shafts system under strong ground motion and their results are verified with experimental data.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.328-335
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• 2000

The substructure of Light Rail Transit is mainly built on elevated structure that is composed of pier, girder and bridge deck. The bridge deck mostly has been made by field formed reinforced concrete so far. The objectives of the study are to find a method for design and construction of the new bridge deck. I-beam is fabricated to make grid and concrete is poured on it at factory. This type can be used for maintenance of duty line by advantages such as good quality control and short construction time.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.1
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• pp.23-31
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• 2002

The purpose of this study is to investigate the size effect on inelastic behavior of reinforced concrete bridge piers. A computer program, named RCAHEST(reinforced concrete analysis in higher evaluation system technology), for the analysis for reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, local discontinuous deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The effect of number of load reversals with the same displacement amplitude has been also taken into account to model the reinforcing steel. To determine the size effect on bridge pier inelastic behavior, a 1/4-scale replicate model was also loaded for comparison with the full-scale bridge pier behavior.