• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.749-757
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• 2006

Many losses of life and extensive damage of social infrastructures have occurred due to moderate and strong earthquakes all over the world. In this research various design parameters have been evaluated to develop a rational seismic design code of rectangular reinforced concrete(RC) bridge piers. It was confirmed from this study that the axial force ratio and longitudinal steel ratio were most influencing design parameters on the seismic displacement ductility from experimental results of 54 rectangular RC bridge piers, which were tested at domestic and foregin countries. However, these important parameters are not considered in the confinement steel ratio of Korea Highway Bridge Design Specification(KHBDS). The objective of this study is to propose a rational design provision for the transverse reinforcement of rectangular RC bridge piers. New confinement steel ratio is proposed by reflecting the effect of the axial force and longitudinal steel into the current code of KHBDS. furthermore, minimum transverse confinement steel ratio is also proposed to avoid a probable buckling of longitudinal reinforcing steels of RC bridge piers with a relatively low axial force. New practical code can alleviate the rebar congestion in the plastic hinge region of RC bridge pier, which contributes to construct RC bridge piers in a simple and economic way.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.667-673
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• 2010

The near fault ground motion (NFGM) is characterized by a single long period velocity pulse with large magnitude. NFGMs have been observed in recent strong earthquakes, Northridge (1994), Japan Kobe (1995), Turkey Izmit (1999), China Sichuan (2008), Haiti (2010) etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the far field ground motion (FFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this research is to investigate and analyze the seismic response of reinforced concrete bridge piers subjected to near-fault ground motions. The seismic performance of six RC bridge piers depending on three confinement steel ratios and three superstructure mass was investigated on the shaking table. From these experimental results, it was confirmed that the reduction of seismic performance was observed for test specimens with lower confinement steel ratio or more deck weight. The displacement ductility of RC bridge piers in terms of the stiffness degradation is proposed based on test results the shaking table.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.451-458
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• 2008

The near-fault ground motion (NFGM) is characterized by a single long period velocity pulse of large magnitude. NFGM's have been observed in recent strong earthquakes, Izmit Turkey (1999), Kobe Japan (1995), Northridge USA (1994), etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the near-fault ground motion (NFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this study is to investigate and analyze the effect of near-fault ground motions on reinforced concrete (RC) bridge piers with lap-spliced longitudinal reinforcing steels. The seismic performance of four RC bridge piers under near-fault ground motions was investigated on the shake table. In addition, a RC bridge pier is subjected to pseudo-dynamic loadings. Test results showed that large residual displacements were observed in RC bridge piers under NFGM. RC specimens on the shake table failed at relatively low displacement ductility, compared with the displacement ductility of RC bridge pier subjected to pseudo-dynamic loadings.

• Structural Engineering and Mechanics
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• v.24 no.4
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• pp.429-446
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• 2006

Experimental investigation was conducted to evaluate the seismic ductility of earthquake-experienced concrete columns with an aspect ratio of 2.5. Eight circular concrete columns with a diameter of 600 mm were constructed with three test parameters: confinement ratio, lap-splice of longitudinal bars, and retrofitting with Fiber Reinforced Polymer (FRP) materials. The objective of this research is to examine the seismic performance of RC bridge piers subjected to a Quasi static test (QST), which were preliminary tested under a series of artificial earthquake motions referred to as a Pseudo dynamic test (PDT). The seismic enhancement effect of FRP wrap was also investigated on these RC bridge piers. Six specimens were loaded to induce probable damage by four series of artificial earthquakes, which were developed to be compatible with earthquakes in the Korean peninsula by the Korea Highway Corporation (KHC). Directly after the PDT, six earthquake-experienced columns were subjected to inelastic cyclic loading under a constant axial load of $0.1{f_c}^{\prime}A_g$. Two other reference specimens without the PDT were also subjected to similar quasi-static loads. Test results showed that specimens pre-damaged by moderate artificial earthquakes generally demonstrated good residual seismic performance, which was similar to the corresponding reference specimen. Moreover, RC bridge specimens retrofitted with wrapping fiber composites in the potential plastic hinge region exhibited enhanced flexural ductility.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.284-291
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• 2005

A RC column-bent pier represents one of the most popular piers used in highway bridges. Seismic performance of reinforced concrete (RC) column-bent piers under bidirectional seismic loadings was experimentally investigated. Six column bent-piers were constructed with two circular supporting columns which were made in 400mm diameter and 2,000mm height. Test parameters are different transverse reinforcement and loading pattern. These piers were tested under lateral load reversals with the axial load of $0.1f_{ck}A_g$. Three specimens were subjected to bidirectional lateral load cycles which consisted of two main longitudinal loads and two sub transverse loads in one load cycle. Other three specimens were loaded in the opposite way. Test results indicated that lateral strength and ductility of the latter three specimens were generally bigger than those of the former three specimens. Plastic hinges were formed with the spall of cover concrete and the fracture of the longitudinal reinforcing steels in the bottom plastic hinge of two supporting columns for the former three specimens. Similar behavior was observed in the top and bottom parts of two supporting columns for the latter three specimens.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.17-24
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• 1992

It would be much effective that single column type pier is used in concrete slab bridges rather than ${\Pi}$ or gravity type pire is used. To determine the longitudinal benging moment in concrete slab bridges supported by single column type piers, the concept of effective width is applied. By elastic plate theory cooperated with finite element method, the distribution of the longitudinal moment of the slab supported by single column type piers is studied. The main variables are span, width. thickness of the slab, and column section size. The analytical results obtained are summarized and analysed to evaluate the maximum longitudinal negative moment, then a simplified method for calculating the longitudinal moment is proposed.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.1
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• pp.21-31
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• 2016

This study investigates the seismic performance of new hollow reinforced concrete (RC) bridge piers with triangular reinforcement details. The developed triangular reinforcement details are economically feasible and rational, and facilitate shorter construction periods. We tested a model of new hollow RC bridge piers with triangular reinforcement details under a constant axial load and a quasi-static, cyclically reversed horizontal load. We used a computer program, Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST), for analysis of RC structures. The used numerical method gives a realistic prediction of seismic performance throughout the loading cycles for several hollow pier specimens investigated. As a result, developed triangular reinforcement details for material quantity reduction was equal to existing reinforcement details in terms of required performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.93-96
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• 2008

This paper deals with the shaking table test(STT), the Quasi-Static Test(QST), and the Pseudo-Dynamic Test(PDT) to evaluate the seismic performance of RC bridge piers under near fault ground motion. Five scaled specimens were constructed the weight of the superstructure was applied through the prestressing strand at the centroid of the column section during the QST and PDT. However, the STT was simulated. The lateral inertia force of the superstructure by the mass frame which was linked with the pier because of the limited payload of shaking table. Particularly for the STT, friction underneath the mass frame was minimized by special details and it was verified by a series of pre-load test. Scale factor of the RC piers was 4.25.

• Structural Engineering and Mechanics
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• v.15 no.1
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• pp.115-134
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• 2003

The Ting Kau Bridge in Hong Kong is a cable-stayed bridge comprising two main spans and two side spans. The bridge deck is supported by three towers, an end pier and an abutment. Each of the three towers consists of a single reinforced concrete mast which reduces its section in steps, and it is strengthened by transverse cables and struts in the transverse vertical plane. The bridge deck is supported by four inclined planes of cables emanating from anchorages at the tower tops. In view of the threat from typhoons, the dynamic behaviour of long-span cable-supported bridges in the region is always an important consideration in their design. This paper is devoted to the ambient vibration measurements of the bridge for evaluation of dynamic characteristics including the natural frequencies and mode shapes. It also describes the modelling of the bridge. A few finite element models are developed and calibrated to match with the field data and the results of subsequent structural health monitoring of the bridge.

• Structural Engineering and Mechanics
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• v.12 no.6
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• pp.685-698
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• 2001

In this paper, a general method for the automatic search for Strut-and-Tie (S&T) models representative of possible resistant mechanisms in reinforced concrete elements is proposed. The representativeness criterion here adopted is inspired to the principle of minimum strain energy and requires the consistency of the model with a reference stress field. In particular, a highly indeterminate pin-jointed framework of a given layout is generated within the assigned geometry of the concrete element and an optimum truss is found by the minimisation of a suitable objective function. Such a function allows us to search the optimum truss according to a reference stress field deduced through a F.E.A. and assumed as representative of the given continuum. The theoretical principles and the mathematical formulation of the method are firstly explained; the search for a S&T model suitable for the design of a deep beam shows the method capability in handling the reference stress path. Finally, since the analysis may consider the structure as linear-elastic or cracked and non-linear in both the component materials, it is shown how the proposed procedure allows us to verify the possibilities of activation of the design model, oriented to the serviceability condition and deduced in the linear elastic field, by following the evolution of the resistant mechanisms in the cracked non-linear field up to the structural failure.