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Chungche Chou - One of the best experts on this subject based on the ideXlab platform.

  • two plastic hinge and two dimensional finite element models for post tensioned precast concrete Segmental Bridge columns
    Engineering Structures, 2013
    Co-Authors: Hao Jan Chang, Chungche Chou, Joshua T Hewes
    Abstract:

    Abstract Recent studies have confirmed that unbonded post-tensioned (PT) precast concrete Segmental Bridge columns are capable of undergoing large lateral deformation with negligible residual drift. To provide a clear guideline for the modeling of the columns for practicing engineers as well as researchers, this paper presents two types of numerical models: (i) a two-plastic-hinge model using the sectional moment–curvature analysis procedure at two segment interfaces and (ii) a two-dimensional (2D) finite element model using truss and beam-column elements in the computer program PISA. Three unbonded PT precast concrete-filled tube Segmental Bridge column specimens are cyclically tested. Two specimens have mild steel bars crossing to different column heights for studying the effects of anchorage position on the hysteretic energy dissipation (ED) capacity. The test results show that (1) the mild steel bars (“ED bars”) can increase hysteretic energy dissipation, and Specimens 1–3 have equivalent viscous damping of 6.5–8.8%, (2) a plastic hinge length in the first or second segment varies with anchorage position of ED bars and lateral displacement, and (3) an equivalent unbonded length along which the strain in the ED bar is assumed uniformly distributed on each of the two sides is 5–6 bar diameter. A 2D finite-element model is utilized to predict the cyclic behavior of the specimens. Parametric studies using finite-element models are also conducted to investigate the effects of ED bar area, initial strand force, and aspect ratio on the cyclic behavior.

  • hysteretic model development and seismic response of unbonded post tensioned precast cft Segmental Bridge columns
    Earthquake Engineering & Structural Dynamics, 2008
    Co-Authors: Chungche Chou
    Abstract:

    The study investigated the cyclic behavior of unbonded, post-tensioned, precast concrete-filled tube Segmental Bridge columns by loading each specimen twice. Moreover, a stiffness-degrading flag-shaped (SDFS) hysteretic model was developed based on self-centering and stiffness-degrading behaviors. The proposed model overcomes the deficiency of cyclic behavior prediction using a FS model, which self-centers with fixed elastic and inelastic stiffnesses. Experimental and analytical results showed that (1) deformation capabilities of the column under the first and second cyclic tests were similar; however, energy dissipation capacities significantly differed from each other, and (2) the SDFS model predicted the cyclic response of the column better than the FS model. Inelastic time-history analyses were performed to demonstrate the dynamic response variability of a single-degree-of-freedom (SDOF) system using both models. A parametric study, performed on SDOF systems subjected to eight historical earthquakes, showed that increased displacement ductility demand was significant for structures with a low period and low-to-medium yield strength ratio and reduced displacement ductility demand in these systems was effectively attained by increasing energy dissipation capacity. Copyright © 2008 John Wiley & Sons, Ltd.

  • hysteretic model development and seismic response of unbonded post tensioned precast cft Segmental Bridge columns
    IABSE Symposium Weimar 2007. Improving Infrastructure WorldwideInternational Association for Bridge and Structural Engineering, 2007
    Co-Authors: Chungche Chou
    Abstract:

    The aim of this research was to investigate experimentally the durability of the unbonded posttensioned, precast concrete-filled tube (CFT) Segmental Bridge columns subjected twice to cyclic loading. In addition, a stiffness degrading flag shaped (SDFS) model was developed based on self-centering capability and stiffness degradation of the columns. The SDFS model overcomes the deficiency of prediction using a flag shaped (FS) mode, which self-centers with constant stiffness. The experimental and analytical results show that (1) the deformation of the column in two tests is similar but energy dissipation of that is significantly reduced in the second test, and (2) the SDFS model can predict the cyclic response of the column better than that using the FS model. A parametric study, performed on systems subjected to earthquake records, shows that increase of displacement ductility is significant for structures with low period and medium yield strength ratio.

  • cyclic tests of post tensioned precast cft Segmental Bridge columns with unbonded strands
    Earthquake Engineering & Structural Dynamics, 2006
    Co-Authors: Chungche Chou, Yuchih Chen
    Abstract:

    Two ungrouted post-tensioned, precast concrete-filled tube (CFT) Segmental Bridge columns were tested under lateral cyclic loading to evaluate the seismic performance of the column details. The specimens included a load stub, four equal-height circular CFT segments, and a footing. Strands were placed through the column and post-tensioned to provide a precompression of the column against the footing. One specimen also contained energy-dissipating devices at the base to increase the hysteretic energy. The test results showed that (1) both specimens could develop the maximum flexural strength at the design drift and achieve 6% drift with small strength degradation and residual displacement, (2) the proposed energy-dissipating device could increase energy dissipation in the hysteresis loops, and (3) the CFT Segmental columns rotated not only about the base but also about the interface above the bottom segment. This study proposed and verified a method to estimate the experimental flexural displacement using two plastic hinges in the Segmental column. Copyright © 2005 John Wiley & Sons, Ltd.

Yuchih Chen - One of the best experts on this subject based on the ideXlab platform.

  • cyclic tests of post tensioned precast cft Segmental Bridge columns with unbonded strands
    Earthquake Engineering & Structural Dynamics, 2006
    Co-Authors: Chungche Chou, Yuchih Chen
    Abstract:

    Two ungrouted post-tensioned, precast concrete-filled tube (CFT) Segmental Bridge columns were tested under lateral cyclic loading to evaluate the seismic performance of the column details. The specimens included a load stub, four equal-height circular CFT segments, and a footing. Strands were placed through the column and post-tensioned to provide a precompression of the column against the footing. One specimen also contained energy-dissipating devices at the base to increase the hysteretic energy. The test results showed that (1) both specimens could develop the maximum flexural strength at the design drift and achieve 6% drift with small strength degradation and residual displacement, (2) the proposed energy-dissipating device could increase energy dissipation in the hysteresis loops, and (3) the CFT Segmental columns rotated not only about the base but also about the interface above the bottom segment. This study proposed and verified a method to estimate the experimental flexural displacement using two plastic hinges in the Segmental column. Copyright © 2005 John Wiley & Sons, Ltd.

Yu-chen Ou - One of the best experts on this subject based on the ideXlab platform.

  • pseudodynamic testing and inelastic displacement ratios of self centering precast concrete Segmental Bridge columns
    Journal of Structural Engineering-asce, 2018
    Co-Authors: Yu-chen Ou, Ade Yuniati Pratiwi, Jianwei Song
    Abstract:

    AbstractThree unbonded post-tensioned Segmental Bridge columns were tested in this research using pseudodynamic loading. The loading consisted of three consecutive ground motions representing two d...

  • hysteretic modeling of unbonded posttensioned precast Segmental Bridge columns with circular section based on cyclic loading test
    Journal of Bridge Engineering, 2016
    Co-Authors: Z.y. Bu, Yu-chen Ou, Jianwei Song
    Abstract:

    AbstractThe seismic performance of unbonded posttensioned (PT) precast Segmental Bridge columns (PSBCs) with circular sections was investigated. Two precast Segmental columns with/without energy dissipation (ED) bars were tested under quasi-static cyclic loading. Their damage patterns and hysteretic curves were compared. Three single-degree-of-freedom hysteretic models were formulated with the key parameters identified from the tests. Cyclic loading analyses of the two tested specimens were conducted using these hysteretic models. Time history analyses were also conducted utilizing the proposed three hysteretic models to observe their applicability in modeling the dynamic responses of PSBCs. Finally, parametric analyses of PSBCs were performed under the excitation of an ensemble of 20 history ground motions to study the influences of relative yield force, elastic period, and energy dissipation coefficient on the earthquake responses of displacement ductility demand, maximum absolute acceleration, and maxi...

  • cyclic loading test of unbonded and bonded posttensioned precast Segmental Bridge columns with circular section
    Journal of Bridge Engineering, 2016
    Co-Authors: Z.y. Bu, Yu-chen Ou, Jianwei Song, Nasi Zhang
    Abstract:

    Four 1/4-scale precast Segmental Bridge columns (PSBC) with different reinforcement types and arrangements and one monolithic reference column (MRC) were designed and tested under cyclic quasi-static loading. Both UPC (PSBC with unbonded tendons only) and UPCE (PSBC with unbonded tendons and bonded mild steel bars) use unbonded posttensioned (PT) strands to connect the segments. Bonded energy dissipation (ED) bars were added in UPCE to increase the ED ability of unbonded PSBC. Specimens BPC (PSBC with fewer bonded PT bars) and BPCII (PSBC with more bonded PT bars) use bonded PT bars to combine the segments together. The unbonded length was set in ED bars to delay the low-cycle fatigue damage. Test results showed PSBC only has minor concrete cracks or crushing at lower joints. The unbonded PT PSBC with ED bars had higher lateral strength, lower residual drift, and comparable ED with MRC. The bonded PT bar PSBC with appropriate bar arrangement also showed high lateral strength and medium energy-dissipation ability. However, bonded PT PSBC experienced large PT stress loss, which leads to a residual drift of 3% when unloading from 6% drift.

  • Experimental Investigations of Precast Segmental Bridge Columns Seismically Isolated with Lead-Rubber Bearings
    2008
    Co-Authors: Yu-chen Ou, Mu-sen Tsai, Ping-hsiung Wang, Kuo-chun Chang
    Abstract:

    This paper presents a United States-Taiwan cooperative research project on seismic performance of Segmental Bridge columns for accelerated Bridge construction, jointly supported by the Federal Highway Administration (FHWA) and the National Center for Research on Earthquake Engineering (NCREE) in Taiwan. Precast Segmental Bridge column construction is an effective approach in accelerating on-site Bridge construction. However, in the current design practice of Segmental Bridge columns, mild steel longitudinal reinforcement is normally discontinued at the segment joints for ease of on-site erection. This leads to columns with significantly lower lateral strength and hysteretic energy dissipation capacity than conventional monolithic column for a given column size. To address this issue, the authors examine the use of seismic isolation bearings in Segmental Bridge columns to decrease the seismic demand. Among typical seismic isolation bearings, the use of lead-rubber bearings is first investigated. Large-scale specimens of Segmental Bridge columns seismically isolated with lead-rubber bearings will be tested to investigate their seismic performance. The tests will include quasi-static cyclic loading and bidirectional pseudo-dynamic loading with a spectrum-compatible earthquake. The experimental program is in progress and expected to be completed by the end of 2008.

  • Seismic-Resistant Connections for Prefabricated Segmental Bridge Columns
    2006
    Co-Authors: Yu-chen Ou, Ping-hsiung Wang, Kuo-chun Chang
    Abstract:

    Prefabricated Bridge construction has recently gained increased attention in the United States. The advantages of using prefabricated Bridge construction include accelerating Bridge construction, minimizing traffic disruption, lessening the environmental impact, improving safety in work zones and decreasing the life-cycle cost of Bridges. However, the use of Segmental Bridge columns is very limited in regions of high-seismicity such as the state of California. One of the main reasons is the lack of design information to ensure the seismic resistance of connections between two precast units. This paper describes a joint project between the Multidisciplinary Center for Earthquake Engineering Research (MCEER), University at Buffalo, and the National Center for Research on Earthquake Engineering (NCREE), National Taiwan University, on the development of seismic resistant connections in precast Segmental Bridge columns. The analytical study carried out at MCEER, funded by FHWA, identified several critical parameters. These parameters were used as the basis for the design of a series of connection tests conducted at NCREE.

Z.y. Bu - One of the best experts on this subject based on the ideXlab platform.

  • Seismic Performance of Precast Segmental Bridge Columns on the Basis of Bouc-Wen Hysteresis Model
    2020 International Conference on Intelligent Transportation Big Data & Smart City (ICITBS), 2020
    Co-Authors: Hanhui Ye, Z.y. Bu
    Abstract:

    In order to study the seismic performance and hysteresis behavior of precast Segmental columns, the Bouc-Wen hysteresis model was improved, considering the strength degradation, stiffness degradation and pinching effect of precast Segmental columns. By reasonably selecting the parameters, hysteretic curves of different shapes were obtained to simulate the nonlinear hysteresis characteristics of the piers in actual engineering. Three circular section columns with a scale ratio of 1:3.5 were tested under quasi-static cyclic loading to determine the control parameters that affect the hysteresis characteristics of the model, which are monolithic reinforced concrete columns (MRC), unbonded prestressed precast Segmental columns (PSC) and unbonded prestressed precast Segmental columns with energy dissipation bars (PSCE). Finally, the Simulink module in Matlab was used to solve the differential equations, and the three tested specimens were simulated respectively. The predicted results were in good agreement with the force-displacement hysteretic curves obtained by the quasi-static test, which proves the improved hysteresis model proposed in this paper can accurately predict the nonlinear hysteretic response of precast Segmental columns under cyclic loading protocols.

  • inter shear transfer of unbonded prestressing precast Segmental Bridge column dry joints
    Engineering Structures, 2018
    Co-Authors: Z.y. Bu, Weiye Wu
    Abstract:

    Abstract The shear performance of precast Segmental Bridge column (PSBC) epoxy-free dry joints was investigated. Ten PSBC dry joint specimens were tested under monotonic direct shear loading. The design parameters include sectional shape, with or without shear keys, key number and geometry, and confining stress. The shear resistance-relative vertical displacement curves were recorded. The damage patterns and failure mechanism of tested specimens were analyzed. Shear strength formulas for prismatic, castellated, and flat dry joint were derived through data regression. The applicability of proposed formulas together with those from literature was investigated. Finally a finite element (FE) model was calibrated to study the friction contribution to shear capacity at various confining stresses.

  • cyclic performance and simplified pushover analyses of precast Segmental concrete Bridge columns with circular section
    Earthquake Engineering and Engineering Vibration, 2016
    Co-Authors: Z.y. Bu, Rongyue Zheng, Jianwei Song
    Abstract:

    In recent years, precast Segmental concrete Bridge columns became prevalent because of the benefits of accelerated construction, low environmental impact, high quality and low life cycle costs. The lack of a detailed configuration and appropriate design procedure to ensure a comparable performance with monolithic construction has impeded this structural system from being widely used in areas of high seismicity. In this study, precast Segmental Bridge column cyclic loading tests were conducted to investigate the performance of unbonded post-tensioned Segmental Bridge columns. One monolithic and two precast Segmental columns were tested. The precast Segmental column exhibited minor damage and small residual displacement after the maximum 7% cyclic drift; energy dissipation (ED) can be enhanced byadding ED bars. The experimental results were modeled by a simplified pushover method (SPOM), as well as a fiber model (FIBM) finite element method. Forty-five cases of columns with different aspect ratios, axial load ratios and ED bar ratios were analyzed with the SPOM and FIBM, respectively. Using these parametric results, a simplified design method was suggested by regressive analysis. Satisfactory correlation was found between the experimental results and the simplified design method for precast Segmental columns with different design parameters.

  • hysteretic modeling of unbonded posttensioned precast Segmental Bridge columns with circular section based on cyclic loading test
    Journal of Bridge Engineering, 2016
    Co-Authors: Z.y. Bu, Yu-chen Ou, Jianwei Song
    Abstract:

    AbstractThe seismic performance of unbonded posttensioned (PT) precast Segmental Bridge columns (PSBCs) with circular sections was investigated. Two precast Segmental columns with/without energy dissipation (ED) bars were tested under quasi-static cyclic loading. Their damage patterns and hysteretic curves were compared. Three single-degree-of-freedom hysteretic models were formulated with the key parameters identified from the tests. Cyclic loading analyses of the two tested specimens were conducted using these hysteretic models. Time history analyses were also conducted utilizing the proposed three hysteretic models to observe their applicability in modeling the dynamic responses of PSBCs. Finally, parametric analyses of PSBCs were performed under the excitation of an ensemble of 20 history ground motions to study the influences of relative yield force, elastic period, and energy dissipation coefficient on the earthquake responses of displacement ductility demand, maximum absolute acceleration, and maxi...

  • cyclic loading test of unbonded and bonded posttensioned precast Segmental Bridge columns with circular section
    Journal of Bridge Engineering, 2016
    Co-Authors: Z.y. Bu, Yu-chen Ou, Jianwei Song, Nasi Zhang
    Abstract:

    Four 1/4-scale precast Segmental Bridge columns (PSBC) with different reinforcement types and arrangements and one monolithic reference column (MRC) were designed and tested under cyclic quasi-static loading. Both UPC (PSBC with unbonded tendons only) and UPCE (PSBC with unbonded tendons and bonded mild steel bars) use unbonded posttensioned (PT) strands to connect the segments. Bonded energy dissipation (ED) bars were added in UPCE to increase the ED ability of unbonded PSBC. Specimens BPC (PSBC with fewer bonded PT bars) and BPCII (PSBC with more bonded PT bars) use bonded PT bars to combine the segments together. The unbonded length was set in ED bars to delay the low-cycle fatigue damage. Test results showed PSBC only has minor concrete cracks or crushing at lower joints. The unbonded PT PSBC with ED bars had higher lateral strength, lower residual drift, and comparable ED with MRC. The bonded PT bar PSBC with appropriate bar arrangement also showed high lateral strength and medium energy-dissipation ability. However, bonded PT PSBC experienced large PT stress loss, which leads to a residual drift of 3% when unloading from 6% drift.

Andre Filiatrault - One of the best experts on this subject based on the ideXlab platform.

  • large scale seismic testing of a hybrid sliding rocking posttensioned Segmental Bridge system
    Journal of Structural Engineering-asce, 2014
    Co-Authors: Petros Sideris, Amjad J Aref, Andre Filiatrault
    Abstract:

    AbstractIn this paper, a novel precast concrete Segmental Bridge system is introduced and experimentally investigated. The system consists of Segmental members incorporating hybrid sliding-rocking (HSR) joints and internal unbonded posttensioning (PT). The HSR joints are plane interfaces that are oriented normal to the member axis and do not include shear keys or epoxy adhesives. The HSR joints are designed to exhibit sliding (slip-dominant, SD) or rocking (rocking-dominant, RD) to mitigate the applied seismic loading and reduce damage. The joint response is affected by the PT system, which can include straight or curved tendons. Two types of HSR members are developed and investigated: (1) members with SD joints and straight tendons, intended for substructure columns (HSR-SD columns), and (2) members with RD joints and curved tendons, intended for superstructure girders (HSR-RD girders). The SD joints are shown to offer energy dissipation with low damage through sliding in addition to moderate self-center...

  • cyclic performance of precast concrete Segmental Bridge columns simplified analytical and finite element studies
    Transportation Research Record, 2006
    Co-Authors: Yu-chen Ou, Amjad J Aref, Methee Chiewanichakorn, Stuart S Chen, Andre Filiatrault
    Abstract:

    The cyclic performance of an unbonded precast concrete Segmental Bridge column system is examined in this paper. This system uses unbonded posttensioning to enhance the self-centering capability and mild steel reinforcement extended across the segment joints to enhance the energy dissipation capability. A simplified analytical method for the system under lateral load is established, and the simplified analytical results are compared with those obtained from the three-dimensional (3-D) finite element method (FEM). On the basis of the simplified analytical method, suggestions are made about both the height of the column to which the mild steel should be continued from the foundation and the limitation of the steel ratio to minimize residual displacement. With the steel ratio varied, the correlation between the energy dissipation capability and the self-centering capability of this system is investigated by means of the 3-D FEM. From simulation results, it was found that both the energy dissipation and the r...