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Multi-spiral rectangular column is composed of two central interlocking large spirals that are interlocked with four small spirals in the corners to match a rectangular cross-section. Compared to conventional tied column, the multi-spiral column can provide better confinement and its spiral cage can be automatically fabricated and pre-assembled in a factory. Two large-scale rectangular bridge columns were constructed and tested in this study to examine the constructability of multi-spiral reinforcement and the cyclic performance of columns subjected to strong-axis cyclic loading. The test program was also served as a pioneering demonstration of the new bridge column system to boost construction automation that was recently applied to a highway bridge construction project in Taiwan. Test results indicate that the multi-spiral column exhibits superior ductile behavior compared to the conventional tied column, even though the former has only 73% of the total weight of transverse reinforcement of the latter. The parameters of the smooth hysteresis model identified from the test results further indicate that the multi-spiral column can very closely imitate the hysteresis behavior of the conventional tied column despite its slightly greater stiffness degradation. In addition, incremental dynamic analysis of two idealized bridges with conventional tied column and multi-spiral column show that, when the former bridge reached damage index, DI = 1.0 (i.e. having 20% strength deterioration) at S a(T n) = 39.4 m/s2 for far-field ground motions and at S a(T n) = 16.4 m/s2 for near-fault ground motions, the corresponding DI s of the latter bridge are approximately 0.74 and 0.71, respectively, even without strength deterioration. [ABSTRACT FROM AUTHOR]

Nonlinear finite-element model updating (FEMU) is a promising approach for post-event damage assessment of civil structures. This paper conducted FEMU for a full-scale reinforced concrete bridge column tested under a sequence of earthquakes and examined the evolution of seismic damage across different earthquake ground motions. It was found that using experimental data, FEMU can be applied to identify unknown key model parameters (e.g. bond-slip and core concrete parameters) and damage of the columns as represented by the change of the key parameters. In addition, the updated models demonstrated their ability to better predict the system response for future earthquakes. [ABSTRACT FROM AUTHOR]

Five rectangular tie-reinforced bridge columns were tested in this study to investigate the effects of longitudinal reinforcement ratio, aspect ratio, and confining mechanism on their deteriorated hysteresis behaviors. Results were compared with another five spiral-reinforced circular bridge columns reported in the literature; the identified deterioration characteristics of columns indicated that the stiffness degradation and pinching effect of a column would increase as its longitudinal reinforcement ratio decreased. In contrast, the aspect ratio of a column had negligible influence on its stiffness degradation, but its pinching effect increased as the aspect ratio decreased. Due to the better confining mechanism, the severity of deterioration in circular columns was lower than in rectangular columns. The failure in rectangular columns was initiated by the hook loosening of closed hoops and crossties, resulting in gradual strength deterioration, while the failure in circular columns was triggered by the fracture of spirals, resulting in significant strength drops. [ABSTRACT FROM AUTHOR]

The rehabilitation of reinforced concrete (RC) bridge columns subjected to chloride‐induced corrosion is addressed in the present paper. The proposed strategy is based on the replacement of the original external layer made of normal‐strength concrete (NSC) with ultra‐high performance fiber reinforced concrete (UHPFRC), and it additionally involves the substitution of the existing corroded longitudinal reinforcement with new machined steel rebars. This repair technique aims at restoring strength, stiffness, and ductility of the original column in a short time without altering its cross‐section dimensions. Because of the high compactness of the UHPFRC, it also serves at improving its durability. The main contribution of the present work is a numerical investigation carried out in order to identify how the design decisions about the repair strategy influence the behavior of the restored column. The parametric investigation reveals that the length of the zone in which NSC is replaced by UHPFRC as well as the machined index (i.e., ratio between turned and original rebar cross‐section area) must be properly selected to make the intervention effective. Numerical results also highlight that the main design issue to deal with is the relocation of the plastic hinge from the repaired zone towards the weak unrepaired part of the column. Practical design recommendations are finally formulated. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fundamental to the performance-based seismic design is the accuracy of predicted responses under earthquake excitations. This study evaluates the accuracy and uncertainty of predicted maximum and residual displacements of concrete bridge columns subjected to different types of ground motions. A series of nonlinear time-history analyses considering a wide range of element formulations and model parameter combinations was performed to reproduce measured responses from previous shake table tests. Variations in element formulation had little influence on the accuracy and uncertainty of predicted maximum displacements. The gradient inelastic force-based element, however, predicted bar tensile strain profiles across the plastic hinge with higher resolution, but at a higher computational cost than displacement-based and beam with hinges elements. Models with tangent stiffness-based Rayleigh damping produced the most accurate predictions of the maximum drift ratios with an RMSE of 0.011, indicating that the maximum displacement (or drift ratio) can be predicted with reasonable accuracy. Residual displacements, on the other hand, were predicted with unreasonable levels of error and uncertainty. A data-driven model was thus proposed to correct predicted residual displacement. Following correction, the RMSE of the predicted residual drift ratios was reduced by 43 % to 0.006. • The effect of modeling parameters on predicted maximum and residual drifts of RC bridge columns is evaluated. • The most effective modeling combination is identified. • A correction factor for predicted residual drifts is proposed. • Uncertainty of predicted maximum and residual drifts is quantified. [ABSTRACT FROM AUTHOR]

The effects of enhanced confinement on the proposed bridge columns under lateral cyclic loading were investigated in this research by testing large-scale column specimens. The proposed column used nonprestressed partially unbonded seven-wire strands as elastic elements to increase the post-yield stiffness of the column to reduce the residual displacement under seismic loads. The enhanced confinement included rectilinear transverse reinforcement with an increased amount (specimen CSCR) and reduced spacing or innovative five-spiral reinforcement (specimen CSCS). Test results showed that all the specimens exhibited a positive post-yield stiffness ratio of 3.5–6.4 %. However, the enhanced confinement reduced the post-yield stiffness by 42–45 % but increased the lateral strength of the column, which is beneficial for controlling the residual displacement. The enhanced confinement did not affect the drift ratio when the positive post-yield stiffness ended (6 %) but significantly increased the deformation capacity by 15–31 % and the energy dissipation capacity by 37–63 % of the column. Even with a smaller amount of transverse reinforcement, the specimen with the innovative five-spiral reinforcement showed deformation and energy dissipation capacities better than the other specimens with conventional rectilinear transverse reinforcement. A pushover analysis model was developed and modified to better account for the effect of the enhanced confinement and the strand slip, and to consider the end point of positive post-yield stiffness. The comparison with the test result showed that the proposed pushover model well captured the envelope responses of the specimens. Finally, a simplified method was proposed for estimating the moment strength of the proposed column. • Nonprestressed partially unbonded seven-wire steel strands as elastic elements. • Enhanced rectilinear confinement and innovative five-spiral reinforcement. • Large-scale column specimens tested using cyclic loading. • Pushover analysis model and simplified moment strength equation. [ABSTRACT FROM AUTHOR]

The mainshock (MS) is often accompanied by a number of aftershocks (AS). The existence of AS may cause the seismic demand to be greater than the MS. In order to better evaluate the impact of AS, this paper takes RC columns as the research object and performs incremental dynamic analysis (IDA) on the actual recorded mainshock-aftershocks (MS-AS). The Park–Ang model and incremental damage index are used to quantify the effect of the MS and AS, respectively. The damage and fragility analysis of the parameters such as reinforcement ratio, axial compression ratio and shear-span ratio are carried out respectively. The results show that the seismic demand of the MS-AS is greater than the MS. Besides, the damage of the column gradually increases with the increase of axial compression ratio and shear-span ratio, and gradually decreases with the increase of the reinforcement ratio. When the seismic design grade is 7, 8, and 9 degree, the maximum increase rate of additional damage caused by aftershocks is 7, 13, and 15% of the MS, respectively. When the column is in a medium damaged and a severely damaged state, the growth rate of additional damage can be estimated to be 12.7 and 11% of the MS, respectively. The fragility of columns in different damage states under the action of MS-AS is greater than that of MS. Reducing the axial pressure ratio can greatly reduce the damage probability of columns in different damage states. The effect of the MS-AS can be comprehensively considered to select appropriate design parameters in the design, and the additional damage caused by the AS can be estimated according to the damage condition of the column. [ABSTRACT FROM AUTHOR]

In this study, seven one-third-scale bridge column specimens are tested via a quasi-static cyclic test to understand seismic performance differences between cast-in-place (CIP) and precast bridge columns with various shear span-to-depth ratios and connection design details. The columns are designed based on practical engineering application, which aims to provide design reference for the seismic behavior of real-world bridge structures with varying column heights, such as bridge ramps. Based on the test results, it was found that column height exceeding the plastic hinge region is of combined bending and shear failure and that the full development of the plastic hinge region of these columns yields the same damage progression. However, short columns that are lower than the height of the plastic hinge are subjected to pure shear failure, and they are also of the same level of seismic performance except for displacement-related indices. Though the strengthening effect of the grouted splice sleeve connections is observed and damage is more concentrated at the joint for precast bridge columns, the difference of overall seismic performance between CIP and precast bridge columns is less than 5% in terms of ductility and energy dissipation. The addition of shear keys or change of bond material help improve the structural integrity, while the increase of seismic performance is still limited. [ABSTRACT FROM AUTHOR]

In order to improve the applicability of precast bridge columns in high intensity zones, a precast segmental column, equivalent to the cast-in-place(CIP) column was proposed, in which the ultra-high-perfornce concrete (UHPC) was used to connect precast column components. Two 1/4-scale precast segmental bridge columns assembled with UHPC and one monolithic CIP circular column with the same dimensions were designed and tested by applying cyclic quasi-static loading. Test and analysis results show that the UHPC-connected precast columns have the same typical characteristics as a conventional monolithic CIP column with respect to plastic hinge forming mechanism, failure mode, hysteretic behavior and energy dissipation capacity. There were no noteworthy cracks and damages observed around the UHPC connection areas, which may validate that the CIP column components can be firmly and reliably connected using UHPC due to its remarkable bond and confinement performance. Finally, a set of key parameters included by the Bouc-Wen-Baber-Noori (BWBN) model were identified based on the data recorded in the test. By means of the established BWBN model, the cyclic loading responses were recalculated, which matched well those from the test. This model can be further used for the seismic time- history analysis of bridge structural systems that include the UHPC connected precast columns proposed in this paper. [ABSTRACT FROM AUTHOR]

This paper numerically investigates the dynamic behavior of bridge piers reinforced with shape-memory alloy (SMA) rebar when subjected to lateral impact loads. Performance of SMA reinforced pier is compared with column reinforced by conventional steel rebar by performing finite-element (FE) simulations in LS-DYNA. The impact performance of the columns is evaluated by considering variations in different structural- and loading-related parameters including the type of SMA rebar, the length of SMA rebar (LSMA), the impact velocity (Vimp), and the axial load ratio (ALR). From the FE simulations, it is found that the use of SMA rebars at the plastic hinge regions and the impact loading height of the columns significantly enhances the impact resistance and the recoverability of the columns by reducing their damage levels and residual displacements. Also, the failure modes of the columns tend to govern by flexure by using SMA rebars, and the columns reinforced with Cu-based (Cu–Al–Mn) SMA rebars are more likely to fail in flexural modes compared to those reinforced with Ni-based (Ni–Ti) SMA rebars. However, the negative influences of SMA rebars on the impact resistance of the columns are found when LSMA exceeds 0.5 under impact loads with velocities greater than 15 m/s. In addition, an ALR greater than 0.1 considerably increases the impact resistance of the columns. [ABSTRACT FROM AUTHOR]

Despite the numerous advantages high-strength reinforcement (HSR) and high-strength concrete (HSC) offer over conventional materials, the practical use of these materials for bridge column design in seismic zones has somewhat been limited. This is due to the insufficient research data and guidelines for the seismic design of bridges using HSC and HSR and the lack of a reliable analytical model. Therefore, to address this issue and promote the application of HSR and HSC, this paper investigates high-strength bridge columns' seismic performance experimentally and numerically. Six large-scale reinforced concrete (RC) bridge columns and one multi-column bent frame were tested under a quasi-static cyclic loading with constant axial compression. The primary design parameters were axial load ratio, longitudinal and transverse reinforcement yield strength, and transverse reinforcement spacing. The failure pattern of high-strength columns was similar to conventional RC columns and satisfied the requirements for seismic design in terms of failure mode, hysteresis behavior, ductility, and energy dissipation capacity. The experimental ductility values of the high-strength columns were satisfactory and capable of meeting the ductility demand of most codes. Furthermore, a numerical model was built using the OpenSees program to predict the seismic performance of the specimens and then verified by comparing them with the test results of 12 columns. The numerical model's results were in good agreement with the experimental results. The results suggested that numerical modeling techniques commonly used for normal strength concrete (NSC) columns can be used for HSC bridge columns by incorporating a proper material model. [ABSTRACT FROM AUTHOR]

With the expected replacement of deteriorated reinforced concrete bridges to occur in the next several decades, an opportunity exists to design more economic bridge columns in seismically active regions which are rapidly constructed while having enhanced crack resistance for extended service life. A precast hybrid fiber-reinforced concrete (HyFRC) tube, which contains a column's steel reinforcement, is proposed for accelerating construction and is to be filled with plain concrete at the construction site. An experimental column was subjected to static, uni-directional, cyclic loading and utilized a base-rocking design for further ductility enhancement. At the conclusion of the test, the column reached a peak drift ratio of 13.1% and showed minor damage, including elimination of cover spalling. The HyFRC tube column design contributed effective resistance against longitudinal reinforcing bar buckling, allowing the column to maintain 93% of its peak load capacity at 9.5% drift. Compared to a monolithic HyFRC column, the precast HyFRC tube column was constructed with less HyFRC volume while having similar seismic performance, making it a more sustainable alternative.

This study introduced a new design of the grouted corrugated duct connection (GCDC), which improves the structure integrity, bond strength and ease of constructability. A two-phase experimental program was performed to fully understand the connection behaviour. Phase I focused on the pull-out tests of 32 specimens in two batches with various conditions. It indicates that a connection length of 30 times of the rebar diameters would guarantee the bond strength. Phase II compared the 1/3-scale precast bridge column with its cast-in-place reference via quasi-static cyclic test. It showed that the precast column behaved similarly to that of the CIP column. [ABSTRACT FROM AUTHOR]

A shear strength model is proposed for reinforced concrete bridge columns with multispiral transverse reinforcement. The proposed model consists of a proposed discrete computational shear strength model for multispiral reinforcement and shear strength models for concrete and axial load adopted from the literature. The proposed discrete computational model calculates shear strength from each discrete location of the interception between the shear crack and multispiral reinforcement. Furthermore, the model considers the critical location of the shear crack, shear crack angle, direction of shear, and effect of the compression zone. The proposed model together with the Caltrans SDC model, Sezen's model, and Priestley's model are used to predict the shear strength of multispiral columns tested in the literature. Comparison between the prediction and test result shows that the proposed shear strength model produces the best prediction in terms of the mean and standard deviation of the ratio of experimental to predicted shear strength. Based on analysis and test observations, equations to estimate the compression depth of multispiral columns at the ultimate condition and the shear crack angle are proposed to be used in the proposed discrete computational shear strength model. [ABSTRACT FROM AUTHOR]

This study presents the results of a refined numerical investigation meant at understanding the time‐dependent cyclic behavior of reinforced concrete (RC) bridge columns under chlorides‐induced corrosion. The chloride ingress in the cross‐section of the bridge column is simulated, taking into account the effects of temperature, humidity, aging, and corrosion‐induced cover cracking. Once the partial differential equations governing such multiphysics problem are solved through the finite‐element method, the loss of reinforcement steel bars cross‐section is calculated based on the estimated corrosion current density. The nonlinear cyclic response of the RC bridge column under corrosion is, thus, determined by discretizing its cross‐sections into several unidirectional fibers. In particular, the nonlinear modeling of the corroded longitudinal rebars exploits a novel proposal for the estimation of the ultimate strain in tension and also accounts for buckling under compression. A parametric numerical study is finally conducted for a real case study to unfold the role of corrosion pattern and buckling mode of the longitudinal rebars on the time variation of capacity and ductility of RC bridge columns. [ABSTRACT FROM AUTHOR]

This paper aims to explore the seismic performance of a novel earthquake-resilient bridge column with replaceable elements, including external ultra-high-performance concrete (UHPC) cover plates and internal steel dissipaters, based on a numerical model including local and overall levels. The overall model was established to assess the seismic behavior of the bridge columns considering the buckling behavior of steel dissipaters adopting the modified material constitutive relationship, of which the parameters were determined according to the results of the local model. The numerical model was verified with reported experimental results. A parametric analysis was conducted to investigate the effects of three parameters. The results show that the numerical model can effectively evaluate the seismic performance of the bridge columns. The buckling behavior of steel dissipaters dominates lateral deformation capacity of the bridge columns. The steel dissipater's initial defect direction and gap gradient can accelerate the failure of cover plates. Reasonable upper and lower limits are required for the length-to-diameter ratio of the fuse part as well as the gap between the fuse part and surrounding concrete, while only a suitable lower limit is needed for the thickness of cover plate to ensure the superior seismic performance of the bridge columns. [ABSTRACT FROM AUTHOR]

Using residual displacement as a measurable indicator can reduce subjectivity and uncertainties in postearthquake assessments. However, the accuracy of analytical models in predicting displacements, particularly residual displacement, has always been an obstacle in this field. This paper aims to fill the gap in the literature on a proper method to enhance the analytical predictions. A comprehensive parametric investigation on the accuracy of distributed plasticity models was carried out, with a focus on bridges under near-field motions. These parameters include influential nonlinear modeling parameters, loading history, viscous damping, and strain rate. The results of the 20 considered models are compared with the six available shake table test results, and two methods are proposed to enhance the displacement predictions for practical cases. In the first method, actual maximum and residual displacements can be determined with the desired confidence level. In the second method, nonlinear regression analysis based on many influential parameters is conducted to enhance the accuracy of analytical residual displacement. This method considerably reduces the model error compared to the available methods in the literature. [ABSTRACT FROM AUTHOR]

The mainshock (MS) is often accompanied by a number of aftershocks (AS). The existence of AS may cause the seismic demand to be greater than the MS. In order to better evaluate the impact of AS, this paper takes RC columns as the research object and performs incremental dynamic analysis (IDA) on the actual recorded mainshock-aftershocks (MS-AS). The Park–Ang model and incremental damage index are used to quantify the effect of the MS and AS, respectively. The damage and fragility analysis of the parameters such as reinforcement ratio, axial compression ratio and shear-span ratio are carried out respectively. The results show that the seismic demand of the MS-AS is greater than the MS. Besides, the damage of the column gradually increases with the increase of axial compression ratio and shear-span ratio, and gradually decreases with the increase of the reinforcement ratio. When the seismic design grade is 7, 8, and 9 degree, the maximum increase rate of additional damage caused by aftershocks is 7, 13, and 15% of the MS, respectively. When the column is in a medium damaged and a severely damaged state, the growth rate of additional damage can be estimated to be 12.7 and 11% of the MS, respectively. The fragility of columns in different damage states under the action of MS-AS is greater than that of MS. Reducing the axial pressure ratio can greatly reduce the damage probability of columns in different damage states. The effect of the MS-AS can be comprehensively considered to select appropriate design parameters in the design, and the additional damage caused by the AS can be estimated according to the damage condition of the column.

Despite the numerous advantages high-strength reinforcement (HSR) and high-strength concrete (HSC) offer over conventional materials, the practical use of these materials for bridge column design in seismic zones has somewhat been limited. This is due to the insufficient research data and guidelines for the seismic design of bridges using HSC and HSR and the lack of a reliable analytical model. Therefore, to address this issue and promote the application of HSR and HSC, this paper investigates high-strength bridge columns’ seismic performance experimentally and numerically. Six large-scale reinforced concrete (RC) bridge columns and one multi-column bent frame were tested under a quasi-static cyclic loading with constant axial compression. The primary design parameters were axial load ratio, longitudinal and transverse reinforcement yield strength, and transverse reinforcement spacing. The failure pattern of high-strength columns was similar to conventional RC columns and satisfied the requirements for seismic design in terms of failure mode, hysteresis behavior, ductility, and energy dissipation capacity. The experimental ductility values of the high-strength columns were satisfactory and capable of meeting the ductility demand of most codes. Furthermore, a numerical model was built using the OpenSees program to predict the seismic performance of the specimens and then verified by comparing them with the test results of 12 columns. The numerical model’s results were in good agreement with the experimental results. The results suggested that numerical modeling techniques commonly used for normal strength concrete (NSC) columns can be used for HSC bridge columns by incorporating a proper material model.

This article presents a new protection device using aluminum foam to enhance the impact resistance of bridge columns. First, the protection device is designed according to the characteristics of aluminum foam material. The geometric configuration and structure of the device are described. Second, the impact performance of bridge column is analyzed, including impact force analysis, damage analysis, and the influence of axial load. Third, three-dimensional solid element models of columns with and without the protection device are developed in order to verify the effect of the protection device. By comparing dynamic responses of vehicle impact on columns with and without the protection device, it is considered that the protection device has certain protection effect: after installing the protective device, the peak value of impact force reduces by 37.5%, the maximum displacement of column top reduces by 23.7%, the maximum stress at column bottom reduces by 51.6%, the maximum stress at column bottom reduces by 51.6%, the maximum acceleration of the vehicle reduces by 40.6%, and 86.84% of the impact energy is absorbed by the protection device. Finally, the devices with different foam thicknesses and porosities are comparatively analyzed to investigate the influence of these design parameters on impact performance. The results show that the increase in the thickness of aluminum foam has positive effects on the protection capability. The protection capability improves with aluminum foam porosity increasing when the porosity is less than 60%. [ABSTRACT FROM AUTHOR]

There has been significant research effort on seismic-resistant precast bridge columns; however, the research results have not been transferred into the industry to achieve their full potential. This review provides a summary of the research development and challenges for both researchers and practitioners. Applications of new materials in rocking columns are briefly discussed. Three types of rocking columns are reviewed: emulative column, simple rocking column, and hybrid rocking column. It is believed that hybrid rocking columns are the most prominent option when compared with the other two types. Its design recommendations with respect to energy dissipating bars, axial load ratios, and tendons are concluded based on the review data. The amount of energy dissipating bars should be such that its contribution to total bending moment capacity is less than 50%. In most of the cases, the energy-dissipating bar ratios are less than 1.7% of the column sectional area. Upon a careful review of existing experimental test results, an effective stiffness ratio of 20%–40% can be suggested for design. To further facilitate engineering designs, regression equations predicting residual drift to maximum drift ratios, as well as viscous damping ratios are proposed. [ABSTRACT FROM AUTHOR]

Confinement enhances mechanical properties of concrete, especially the strain capacity. As a result, confined reinforced concrete (RC) members usually exhibit higher displacement capacities compared to unconfined members. Even though the behavior of concrete confined with external jackets has been extensively investigated in the past, confined properties of polyureajacketed concrete are largely unknown and were investigated in the present study. Thirty concrete cylinders were tested under slow uniaxial compression to investigate mechanical properties of polyurea-confined concrete and to establish stress-strain behavior. It was found that polyurea does not increase the strength of the confined sections under static loads. However, the compressive strain capacity of polyurea-confined concrete is more than 10%, equal to or higher than the reinforcing steel bar tensile strain capacity. Two uniaxial stress-strain models were developed for polyurea-confined concrete with circular sections under static loads. Analytical studies showed that the displacement ductility capacity of low-ductile bridge columns can be doubled using polyurea jackets. This unique property may make this type of confinement a viable retrofit or rehabilitation method to increase the displacement capacity of low-ductile members and structures in seismic regions. [ABSTRACT FROM AUTHOR]

The feasibility that the transverse reinforcements in steel-reinforced Engineered Cementitious Composites (ECC) columns could be reduced or even totally eliminated has been experimentally demonstrated. However, due to the effect of the tie volume ratio in ECC plastic hinges on the seismic performance of RC composite bridge columns not being fully clarified as of yet, a numerical study was carried out. In this study, the analytical models based on the fiber element method, by considering the superposition of different lateral confinements resulting from ties and the ECC cover, were used to correlate with a target hybrid-loading experiment. Load-displacement hysteresis, strains in extreme fibers and longitudinal bars in analytical results correlated well with the experiments, verifying the accuracy of the analytical models proposed in this study. Based on the analytical results, it was found that the volume tie ratio had little effect on the stress-strain hysteresis of the ECC cover, but a lower volume tie ratio resulted in more significant nonlinear behavior longitudinally. Finally, the pushover analysis was conducted to investigate the effect of volume tie ratios on the seismic design parameters, and the results showed that a higher volume tie ratio resulted in a limited increase in the maximum allowable displacement for design.

SUMMARY Capacity‐based inelastic displacement spectra that comprise an inelastic displacement ratio (CR) spectrum and the corresponding damage index (DI) spectrum are proposed in this study to aid seismic design and evaluation of reinforced concrete (RC) bridges. Nonlinear time history analyses of single‐degree‐of‐freedom (SDOF) systems are conducted using a versatile smooth hysteretic model when subjected to far‐field and near‐fault ground motions. It is demonstrated that the Park and Ang damage index can be a good indicator for assessing the actual visible damage condition of columns regardless of its loading history, providing a better insight into the seismic performance of bridges. The computed spectra for near‐fault (NF) ground motions show that as the magnitude of pulse period ranges increases from NF1 (0.5‐2.5 seconds) to NF2 (2.5‐5.5 seconds), the spectral ordinates of the CR and DI spectra increase moderately. In contrast, the computed spectra do not show much difference between NF2 and NF3 (5.5‐10.5 seconds) when the period of vibration Tn≤ 1.5 seconds, after which the spectral ordinates of NF3 tend to increase obviously, whereas those of NF2 decrease with increasing Tn. Moreover, when relative strength ratio R = 5.0, nearly all of the practical design scenarios could not survive NF3. On the basis of the computed spectra, CR and DI formulae are presented as a function of Tn, R, and various design parameters for far‐field and near‐fault ground motions. Finally, an application of the proposed spectra to the performance‐based seismic design of RC bridges is presented using DI as the performance objective. [ABSTRACT FROM AUTHOR]

Bridges located at moderately or highly aggressive environments can be subjected to different levels of deterioration. Deterioration can be observed as cracking or spalling of concrete and corrosion of reinforcement. Among them corrosion of reinforcement is the main concern in capacity reduction due to loss of steel area and reduction in yield strength. Corrosion may even induce total collapse of bridge. In many cases, reinforced concrete bridges constructed over rivers exposed to reinforcement corrosion at splash zone of pier. Service life of these deteriorated bridges can be reduced significantly due to some loss in load carrying capacity which can also negatively affect the future seismic performance. Focus of these research has been given to investigate reduction of capacity in seismic behavior of bridges subjected to moderately aggressive environmental effects and to propose a condition factor to be used in future bridge analysis. Different deterioration models have been studied and a proper model has been modified to estimate loss in load capacity for a series of standard highway bridges. A condition factor, representing an equivalent deterioration, has been proposed for evaluation and design of bridges at moderately aggressive environment. Use of such condition factor in design can compensate future loss in capacity resulting some overdesign at early years of bridge. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • A new earthquake resilient precast segmental UHPC bridge column was proposed. • Cyclic loading tests were conducted on three specimens and their repaired specimens. • The lateral bending failure of cover plates and coupler failure of dissipaters were found. • The repaired specimens have similar seismic behavior except initial stiffness. Abstract A new earthquake resilient ultra-high-performance concrete (UHPC) bridge column was proposed and fabricated with precast segmental construction. The bottom segment was divided into two parts: core zone and four replaceable surrounding UHPC plates, between which replaceable dissipaters were employed. Rapid repair was completed with substitutions of damaged replaceable components, including UHPC plates and dissipaters, after an earthquake. Cyclic loading tests were conducted on three 1:3 scaled specimens and their corresponding repaired specimens. The research parameters included post-tensioning (PT) force level and usage of replaceable dissipaters. The test results showed that both the construction and repair times could be decreased owing to the use of proposed bridge column. The damage to replaceable dissipaters and cover plates was significant, but the damage to core concrete was minimal. The original repaired specimens presented displacement capacities of at least 5% and 4% drift, respectively. All specimens showed excellent self-centering and had less than 0.8% residual drift until failure. Two different failure modes were found: cover plate failure in lateral bending failure, which significantly reduced the lateral load, and dissipater coupler failure, which caused dissipaters to work inefficiently and decreased energy dissipation. Compared with the original specimens, which failed in the same failure mode, the repaired specimen had similar lateral load and displacement capacities, but a lower initial stiffness. All PT tendons were elastic and no yield or rupturing was found, but the stress loss was significant. The rotation of the bottom joint dominated the lateral deformation, and the contribution of joint sliding can be neglected. [ABSTRACT FROM AUTHOR]

Reinforced concrete bridge columns often endure significant damages during earthquakes due to the inherent deficiencies of conventional materials. Superior properties of the new materials such as shape memory alloy (SMA) and ultra-high-performance concrete (UHPC), compared to the reinforcing steel and the normal concrete, respectively, are needed to build a new generation of seismic resistant columns. Application of SMA or UHPC in columns has been separately studied, but this paper aims to combine the superelastic behavior of NiTi SMA and the high strength of UHPC, in order to produce a column design with minimum permanent deformation and high load tolerance subjected to strong ground motions. Additionally, the excellent corrosion resistance of NiTi SMA and the dense and impermeable microstructure of UHPC ensure the long-term durability of the proposed earthquake resistant column design. The seismic performance of four columns, defined as steel reinforced concrete (S-C), SMA reinforced concrete (SMA-C), SMA reinforced UHPC (SMA-UHPC), and reduced SMA reinforced UHPC (R-SMA-UHPC) is analyzed through a loading protocol with up to 4% drift cycles. The use of NiTi SMA bars for the SMA reinforced columns is limited to the plastic hinge region where permanent deformations happen. All the columns have 2.0% reinforcement ratio, except the R-SMA-UHPC column that has a 1.33% reinforcement ratio to optimize the use of SMA bars. Unlike the S-C column that showed up to 68% residual deformation compared to peak displacement during the last loading cycle the SMA reinforced columns did not experience permanent deformation. The SMA-C and R-SMA-UHPC columns showed similar strengths to the S-C column, but with about 5.0- and 6.5-times larger ductility, respectively. The SMA-UHPC column showed 30% higher strength and 7.5 times larger ductility compared to the S-C column.

In this article, an application of superelastic shape memory alloy strands for improving the seismic performance of unbonded prestressed reinforced concrete bridge column is proposed. In the reinforced concrete column with unbonded prestressing steel-shape memory alloy strands, superelastic shape memory alloy strands are put in series with unbonded steel strands, and the loading plateau of shape memory alloy is exploited to limit the increase in the axial load of column under an earthquake. Quasi-static analysis and seismic analysis were conducted to compare the seismic performance of conventional reinforced concrete column, reinforced concrete column with unbonded prestressing steel strands, and the proposed reinforced concrete column with unbonded prestressing steel-shape memory alloy strands. Result shows that reinforced concrete column with unbonded prestressing steel-shape memory alloy strands has larger ultimate displacement capacity than reinforced concrete column with unbonded prestressing steel strands in the quasi-static analysis. In the seismic analysis, reinforced concrete column with unbonded prestressing steel-shape memory alloy strands suffers from smaller earthquake residual displacement than reinforced concrete column and reinforced concrete column with unbonded prestressing steel strands. Furthermore, parametric analysis was carried out to investigate the effects of unbonded steel strand ratio, prestressing force ratio, bonded longitudinal reinforcement ratio, and maximum tensile force ratio (area of shape memory alloy strands) on the ultimate displacement and quasi-static residual displacement of reinforced concrete column with unbonded prestressing steel-shape memory alloy strands. Results show that increasing the prestressing force ratio and the maximum tensile force ratio within certain ranges can improve the self-centering capability of column. Increasing the area of bonded longitudinal reinforcement and unbonded steel strand ratio results in larger residual displacement. [ABSTRACT FROM AUTHOR]

In this study, six 1/3-scale short bridge column specimens are investigated for shear strength under the same quasi-static cyclic loading protocol. The specimens consist of one cast-in-place (CIP) reference column and five precast columns, and the precast columns are designed with different connection approaches. The test includes the comparison between the specimens with or without shear keys, bonded or unbonded prestressing tendons, and column or footing embedment. Test results show that the shear strengths of precast columns using only mild reinforcement are emulative of the CIP column. Shear keys employed in the connection do not retain significant improvement in terms of hysteretic behavior, while specimens with prestressing tendons possess higher shear strength but lower ductility. The unbonded prestressing tendon provides unique self-centering capability with good energy dissipation. Finite element models of the columns were created with ANSYS by considering the bond-slip effect between reinforcement and concrete, contact behavior of connection surface, and material nonlinearity, depending on different structural details. The models can effectively simulate damage development under monotonic loading, and the load-displacement curves are in good agreement with the backbone curves of the test results. [ABSTRACT FROM AUTHOR]

Accelerated bridge construction (ABC) is being increasingly used in new bridge construction and repair. For bridge substructure elements, ABC typically requires connections, such as mechanical couplers, between prefabricated elements where moment demands are largest. Grouted sleeves (GSs) offer good construction tolerances and load transfer between precast concrete elements. Therefore, they have gained interest for use in ABC in seismic regions. Large-scale precast column models using GS splices were designed and tested using a shifted plastic hinge (SPH) concept to minimize the damage in the footing and retain the column ductility. The testing matrix considered aspect ratio, moment gradient, and splicing details. Results showed that SPH can be used for flexural and flexural-shear columns; plastic hinging formed above the sleeve region and footing dowels remained elastic to minimize footing damage. Each precast column exhibited good ductility and energy dissipation, and formed slightly shorter SPH length compared with conventional columns. [ABSTRACT FROM AUTHOR]

The high amount of confining lateral steel required by seismic design provisions for rectangular bridge columns can cause steel congestion which may hinder the placement of conventional concrete (CC). Self-consolidating concrete (SCC) eliminates or reduces concrete placement and consolidation issues; however, there is limited data on the seismic performance of SCC bridge columns. This study encompassed experimental investigations to assess the stress-strain relationships of SCC mixes and the seismic performance of rectangular SCC bridge columns. SCC and CC rectangular columns were tested. Experimental results showed that the strain at strength and the ultimate strain of SCC are higher than those of CC, while concrete ductility and the elastic modulus of SCC are lower than those of CC. Experimental results of the column tests showed that the use of SCC reduces displacement ductility and energy dissipation but increases drift ratio at failure. The SCC column performance under inelastic cyclic lateral loading was found to be satisfactory and comparable to that of CC columns. [ABSTRACT FROM AUTHOR]

In this study, seven 1/3-scale bridge column specimens are investigated under the same quasi-static cyclic loading protocol both experimentally and numerically. The specimens consist of one cast-in-place (CIP) reference column and six precast columns. The precast columns are designed with different connection details, and they are tested for the feasibility study of the urban viaducts of highway S6 in Shanghai, China. The seismic performance of the precast columns needs to be investigated and verified prior to the practical application of these connection designs. Based on the experimental results, the precast specimens solely using mild reinforcement exhibit similar hysteretic behavior to the CIP reference column, though various grouted connection approaches are employed. The differences between these precast specimens and the CIP reference column are less than 15% for all indices. The precast specimens with bonded tendons (prestressing strands or prestressing bars) retain higher strength, but no less than 30% decrease of energy dissipation capacity is found. The bonded prestressing strands give at least 10% increase in strength compared with the CIP reference column, while the bonded prestressing bars provide approximately 50% improvement. The precast specimen utilizing unbonded tendon (prestressing strands) shows unique self-centering capability with equivalent energy dissipation capacity of the CIP reference column, but it has 33% lower ductility. Finite element modeling is performed and calibrated with the test data. Bond-slip behavior near column-to-footing interface is modeled by using a ZeroLength element at the interface. Buckling, fatigue and strength reduction of reinforcement are also considered in the model. Hysteretic behaviors of the specimens can be effectively simulated, and differences of ultimate strengths between the experimental and numerical results are less than 9%. [ABSTRACT FROM AUTHOR]

This paper reports the numerical simulation of earthquake-damaged circular columns repaired with the combination of near-surface-mounted (NSM) basalt fiber reinforced polymer (BFRP) bars with external BFRP sheets jacketing at quasi-static loading. The numerical modeling was carried out with the nonlinear OpenSees software platform by using the BeamWithHinges element. In the simulations, the effect of the previous earthquake damage on the behavior of the repaired columns was taken into account, and a simple and effective material damage-accumulation model is proposed to modify the constitutive of materials in the unrepaired regions of the repaired columns. The developed numerical models were validated by comparing their quasi-static findings with those obtained from a previous experimental program, and a good agreement can be observed. Furthermore, the efficiency of the repair technique used in tests is evaluated via the developed numerical model.

With the expected replacement of deteriorated reinforced concrete bridges to occur in the next several decades, an opportunity exists to design more economic bridge columns in seismically active regions which are rapidly constructed while having enhanced crack resistance for extended service life. A precast hybrid fiber-reinforced concrete (HyFRC) tube, which contains a column’s steel reinforcement, is proposed for accelerating construction and is to be filled with plain concrete at the construction site. An experimental column was subjected to static, uni-directional, cyclic loading and utilized a base-rocking design for further ductility enhancement. At the conclusion of the test, the column reached a peak drift ratio of 13.1% and showed minor damage, including elimination of cover spalling. The HyFRC tube column design contributed effective resistance against longitudinal reinforcing bar buckling, allowing the column to maintain 93% of its peak load capacity at 9.5% drift. Compared to a monolithic HyFRC column, the precast HyFRC tube column was constructed with less HyFRC volume while having similar seismic performance, making it a more sustainable alternative. [ABSTRACT FROM AUTHOR]

First, cyclic loading tests were conducted on scaled-down bridge column models using normal- and ultra-strength fiber-reinforced concrete made with polyvinyl alcohol fibers (PVA-UFC) and normal- and ultrahigh-strength rebars. The experimental results were compared, focusing on the relation between load and displacement, skeleton, crack distribution, and failure modes. Second, in order to evaluate the reproducibility of the cyclic loading test by finite element (FE) analysis, trace analyses were carried out. The FE analyses investigated the applicability of the conventional analytical model of concrete for PVA-UFC. Compared with the experimental results, overall hysteresis loops and maximum strength responses were reproduced with sufficient accuracy by using adequate analytical models. Lastly, parametric analyses were conducted on varying cross-sectional areas of columns, and the extent to which cross-sectional areas could be reduced by using UFC was investigated. [ABSTRACT FROM AUTHOR]

Both the peak dynamic force (PDF) and the equivalent static force (ESF) of a vehicle collision with reinforced concrete bridge columns were examined as part of an extensive finite element (FE) analyses study. An extensive parametric study of 13 parameters, including the concrete material model, the unconfined concrete compressive strength f c ′ , the material strain rate, the percentage of longitudinal reinforcement, the hoop reinforcement, the column span-to-depth ratio, the column diameter, the top boundary conditions, the axial load level, the vehicle’s velocity, the vehicle’s mass, the roadside distance between errant vehicle and unshielded bridge column, and the soil depth above the top of the column footing was conducted. Three approaches were used to investigate the ESF. The ESF in the first (stiffness-based) approach was defined as the static force producing the same maximum displacement that is produced by a vehicle collision at the point of impact. The ESF examined in the second approach was calculated according to the Eurocode. The ESF studied in the third approach was defined as the Peak of the Twenty-five Milli Second moving Average (PTMSA). The different ESFs were compared to the ESF in the American Association of State Highway and Transportation Officials-Load and Resistance Factor Design (AASHTO-LRFD; 2670 kN [600 kips]). In general, the ESF calculated according to the Eurocode presented the lower bound while those from the stiffness-based approach presented the upper bound. Furthermore, the recommended ESF of the AASHTO-LRFD was found to be non-conservative for heavy and/or high speed vehicle impacts; it was found to be too conservative for light and/or slow vehicle impacts. Hence, rather than a constant design impact force, a variable design impact force should be used. An equation was developed to calculate a design impact force, which is the function in the vehicle’s mass and velocity. A simplified equation based on the Eurocode equation of the ESF was proposed. These equations, however, do not require cumbersome FE analyses. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of concrete columns reinforced by steel basalt-fiber composite bars (SBFCBs) and steel basalt-fiber hybrid stirrups (SBFHSs) as innovative hybrid reinforcements. Four RC columns were cast; one column, which was reinforced longitudinally and transversely with traditional steel bars, served as a reference. Three columns were constructed with varying amounts of a basalt fiber-reinforced polymer (BFRP) material in the SBFCBs; the postyield stiffness ratio of the hybrid reinforcement was 0.1, 0.3, or 0.5. All the columns were subjected to a constant axial load and lateral cyclic loading. Several parameters affecting the columns' responses, such as the BFRP reinforcement ratio and the ratio between the postyield and elastic stiffness of the longitudinal bars, were examined. The experimental results showed that the failures of all four columns were flexural, and the postyield stiffness of the longitudinal reinforcement had a significant effect on the stiffness, bearing capacity, residual deformation, and amount of energy dissipated by the test columns. [ABSTRACT FROM AUTHOR]

In order to evaluate the behavior of reinforced concrete columns with rectangular hollow section subjected to axial compression and biaxial bending, the calculation formula of load capacity and moment-curvature relationship are derived according to the distribution type of neutral axis in this paper. The load capacity and rotation ductility of the bottom control section of three reinforced concrete specimen bridge columns with rectangular hollow section under different axial compression ratio, reinforcement ratio and stirrup ratio are analyzed based on these calculation formulae. The Mx–My interaction curves and moment-curvature curves of bridge column specimens derived from the theoretical calculation show good agreement with the experimental data obtained by cyclic testing of three specimens under axial compression and biaxial bending. The results show that the P–Mx–My interaction has considerable effects on the behavior of the reinforced concrete bridge columns with rectangular hollow section. If these interaction effects are ignored, then the load capacity and deformation are overestimated and this fact can be crucial from the viewpoint of design.