Concrete Bridge Piers Research Articles

Enhanced Strategies for Seismic Resilient Posttensioned Reinforced Concrete Bridge Piers: Experimental Tests and Numerical Simulations

Recent studies have proposed and investigated the use of unbonded posttensioned (PT) bars in bridge substructure systems to improve their self-centering behavior. However, the lateral loading resistance and self-centering capacities of reinforced concrete (RC) piers with PT bars (i.e., the posttensioned RC bridge piers: PRC piers) could be easily compromised by early crushing of the base compression toe during a seismic event. Hence, in order to enhance the pier base integrity, the present study proposes and experimentally investigates three simple strategies for enhancing the seismic-damage resistance of PRC piers based on the use of (1) a steel tube to encase the PRC pier’s end segment; (2) ultrahigh performance concrete at the PRC pier’s end segment; and (3) engineered cementitious composite mortar bed underneath the pier bottom. The performance of these three PRC piers was assessed by comparing them with a conventional PRC pier under cyclic loading and considering the damage evolution and the cyclic force-displacement response. The comparison shows that the proposed enhanced PRC solutions allow improving the seismic performance of the system sustaining large lateral drifts with good self-centering behavior. Moreover, based on the test results, finite element models accounting for PT force loss and the rocking characteristics were validated to reproduce the piers’ cyclic response, thus highlighting the importance of considering PT force loss during numerical simulations.

Probabilistic seismic assessment of innovative concrete bridge piers with Engineered Cementitious Composites (ECC) by different types of shape memory alloys (SMAs) bars

Critical role of bridges in post-earthquake rescue activities has made their seismic safety a major concern of structural engineers. While preventing collapse is one of essential requirements in bridge engineering, recent earthquakes have shown that bridges may also cease functionality due to residual deformations. To address this, shape memory alloys (SMAs) have received wide attentions according to their ability to recover the initial shape even after large plastic deformations. Two types of SMAs (NiTi and Cu–Al–Mn) are used in this paper to reinforce nine different concrete bridge piers in which Engineered Cementitious Composite (ECC) is also used for enhancing ductility in plastic hinge region. Each of the piers is subjected to 56 near field ground motions and collapse capacity of the piers is evaluated probabilistically using incremental dynamic analysis. The comparative results indicate that simultaneous use of steel and NiTi reinforcement in a plastic hinge area filled with ECC concrete can lead to a 30% improvement in median collapse capacity of the studied pier.

Experimental and finite element investigations on hydration heat and early cracks in massive concrete piers

The concrete hydration heat and different construction methods directly affects the early crack resistance of massive concrete structures and may lead to concrete cracks. In this work, the hydration heat test and finite element simulation were conducted to investigate the early cracking resistance and the main influencing factors of the massive concrete bridge pier. The size of the bridge pier was 8 m (length) × 4 m (width) × 22.5 m (height), and the pier was poured in two layers (8.5 m/14 m) with an interval of 37 h. The internal temperature of the pier was tested 16 days after the concrete pouring using pre-buried temperature sensors, and the crack expansion on the surface of the pier was continuously observed during the test period. The test obtained a maximum concrete temperature of 64.25 °C after 100 h after the concrete pouring, and 3 cracks were found on the surface of the pier. The pier simulation model is established according to the actual situation in the test, The maximum temperature inside the bridge pier obtained from the simulation is 61.73 ℃, and the temperature field development pattern and the crack expansion on the pier surface were basically consistent with the test, which confirmed the reliability of the simulation method. Besides, the simulation process found that the maximum main tensile stress on the surface of the bridge pier was 2.77 MPa, which was mainly distributed near the interface of the 2 layers, indicating that the layered pouring scheme adopted in the test was improper. The effect of layered casting schemes on the early cracking resistance of massive concrete has rarely been discussed, and further simulations revealed that: the maximum main tensile stress can be reduced by gradually improving the number of layers, layer height and interval between each layer. By changing the original layered pouring scheme to 3 layers with an interval of 3 days between each layer, the maximum principal tensile stress is reduced to 1.50 MPa, and early cracking of the bridge pier can be avoided. This work provides a general numerical analysis method with high accuracy, parameterization and quantification for early crack control of massive concrete structures in a multi-factor complex environment.

Comparative study on seismic performance of concrete-filled double skin tubular piers and hollow concrete piers: Experimental and analytical

Hollow bridge piers with concrete-filled double skin tubular (CFDST) section could offer more efficient fabrication and better confinement effect, but increase construction cost with the use of steel tubes if compared to regular hollow concrete bridge piers. Although hollow concrete piers and CFDST piers have been the focus of the existing experimental and numerical studies, there is limited information available regarding to the seismic performance comparisons of the two systems while considering the cost perspective. Therefore, a comparative study was carried out in the current study to compare the seismic performance of the two designs quantitatively, while considering the cost effectiveness. The experimental results of the two designs were compared in terms of lateral force bearing capacity, deformation capacity, energy dissipation, stiffness degradation, residual displacement, and performance per cost ratio. It has been found that the lateral force bearing capacity, the displacement ductility, the effective pier flexural stiffness and the performance per cost ratio of CFDST pier increased by 50.2%, 16.7%, 22.9% and 36.5%, respectively, while the residual drift ratio reduced by 33.3% at a large drift ratio of 3.0%. In addition, the seismic performance of another two CFDST piers with different diameter-to-thickness ratio of outer steel tubes and hollow ratio was studied through cyclic lateral loading tests. A verified finite element model was also developed to further conduct parametric study to fully investigate the influence of the diameter-to-thickness ratio of outer steel tubes and hollow ratio on the seismic performance of CFDST piers. Experimental and numerical results have found that the diameter-to-thickness ratio of outer steel tubes is one of the most important factors that influences the seismic performance of CFDST piers. In contrast, the hollow ratio significantly influences the deformation capacity of CFDST piers without significantly affecting the lateral force bearing capacity. The diameter-to-thickness ratio of outer steel tubes is suggested to take between 60 and 150, and the hollow ratio is suggested to take between 0.5 and 0.7 for cost effectiveness and ductile seismic design purposes of CFDST bridge piers.

Application of elastic wave tomography method for damage evaluation in a large-scale reinforced concrete structure

Quality control of construction works and characterization of defects in newly built reinforced concrete structures is an important issue. Usually, these kinds of defects can be evaluated by means of visual inspection, however, there are cases, in which damage cannot be reliably evaluated visually. In this situation, Non-Destructive Testing methods can be used. In this study we report the results of application of Elastic Wave Tomography method for evaluation of a defect in a newly built reinforced concrete bridge pier. A large void located inside the bridge pier was detected using Elastic Wave Tomography method. Due to the presence of the large defect the structure was demolished. Elements of the demolished bridge pier were visually observed, which allowed to confirm the results of Elastic Wave Tomography method.

Seismic vulnerability assessment of reinforced concrete bridge piers with corroded bars

AbstractReinforced concrete (RC) structures located in aggressive environment, for example, RC bridge piers close to the sea and experiencing chloride attacks, may be exposed to an increased seismic vulnerability. This requires practical yet effective safety assessment strategies aimed to determine the seismic behavior by incorporating corrosion deterioration phenomena. An easy‐to‐use phenomenological model is here developed to describe the seismic behavior of corroded RC elements based on a fiber hinge formulation wherein the corrosion‐induced mechanical degradation of concrete and steel is implemented through appropriate constitutive laws at the fiber level. The developed fiber hinge formulation is first validated against experimental cyclic tests of corroded RC columns from the literature. Then, the proposed approach is used for the seismic vulnerability assessment of the Zappulla multi‐span viaduct (southern Italy), whose RC bridge piers (with a box‐shaped, two‐cell hollow rectangular cross section) are exposed to carbonation and chloride‐induced corrosion. A comprehensive in‐situ testing campaign is conducted for the mechanical characterization of the materials in the RC piers. Corrosion potential mapping, carbonation tests and tensile tests on corroded bars extracted from RC piers are critically interpreted to calibrate the constitutive laws of the fiber‐hinge model. Motivated by experimental findings, numerical seismic analyses (including linear dynamic, nonlinear static and nonlinear dynamic analyses) are performed under two different corrosion scenarios to quantify the impact of corrosion on the resulting seismic vulnerability conditions of bridge piers with corroded bars. The proposed approach is characterized by low computational cost and lends itself to large‐scale seismic vulnerability assessment of other existing RC bridges placed in corrosive environment.

Efficiency of an Improved Grouted Corrugated Duct (GCD) Connection Design for Precast Concrete Bridge Pier: Numerical and Parametric Study

In this study, finite element analysis (FEA) has been conducted for an improved grouted corrugated duct (GCD) connection design with a reserved recess in bridge footing. This study aims to understand the damage progression mechanism and to evaluate the contribution of each component in the improved GCD connection design. Numerical model based on the experimental results are first created, validated and calibrated. It is found that the confining effect (support and friction force) provided by recess sidewall keeps the connection in good integrity. It also prevents early deformation and early development of transverse cracks along the connection interface, which further avoids the damage concentration at connection joint, transfers the plastic hinge region. Parametric study is then carried out by considering different recess depths, cushion thicknesses, recess diameters, and mortar strengths. The effect of recess details on mechanical behavior is thus studied. Recess depth can be designed as 6–20% of the column section size to ensure a higher upper limit of overall strength and ductility, and it also influences the stress distribution area of the joint local. The stiffness and strength of recess control the local damage, while has limited impact on the overall performance. In addition, preliminary suggestions on the GCD design of recess depth, thickness of mortar cushion, recess diameter, the strength of mortar are proposed.

Hysteretic model of reinforced concrete bridge piers based on earthquake damage and corrosion from saline soil

A hysteretic model of reinforced concrete (RC) bridge piers in saline soil environment, incorporating corrosion-induced overall structural degradation, is obtained based on earthquake damage by applying damage parameter. A damage analysis of the observed 13 RC bridge piers tested under cyclic loading including cracks evolution, residual deformation, relative unloading degradation, cyclic unloading stiffness degradation and strength deterioration is presented. A quantification approach for seismic damage considers the sources of deterioration: i.e., number of loading cycles and controlled displacements and incorporates a deterioration parameter aiming to control the deterioration modes. The skeleton model consists of three segments and is determined by simplifying the experimental skeleton curve. Yield strength reduction and sectional loss of reinforcement are computed to characterize the corrosion-induced degradation. It is determined that the equivalent skeleton model could match the experimental results. The applicability as well as accuracy of proposed model in simulating the hysteretic behaviours are calibrated by comparing the model with the experimental curves. The model is capable to approximate the complete hysteretic response.

Evaluation of hybrid NSM-CFRP technical bars and FRP sheets for seismic rehabilitation of a concrete bridge pier

Seismic retrofit is a cost-effective and sustainable solution for improving bridge structures in seismic zones. Fiber Reinforced Polymer (FRP) is commonly used to replace steel components in retrofit projects due to their light weight, high strength, and high corrosion resistance. The fabrication of novel hybrid structures from FRP and concrete is the next step researchers are addressing. In this context, the present study focuses on numerical modeling of the experimentally determined response of a hybrid FRP and concrete bridge pier subjected to quasi-static tests. The results from FEM showed strong agreement with the experimental response in terms of load-displacement curve and failure mode. After validating the model, alternative designs (changing the height of the CFRP slab, changing the height and compaction of the CFRP bar, and concrete encasement with and without CFRP slab) were numerically tested to investigate the effects of each model on the load capacity. With the conventional concrete encasement, the bearing capacity of the bridge pier can be rehabilitated, but with the CFRP plate in the above system, the bearing capacity of the bridge pier is increased by more than 60%. Therefore, it can be concluded that seismic strengthening techniques with CFRP sheets and mounted NSM-CFRP bars are suitable for concrete bridge piers.

Optimization of critical factors responsible for prestressed concrete bridge pier collapse

In this research, the Taguchi approach has been used to identify the crucial factors responsible for the failure of a reinforced concrete bridge pier in India. The Taguchi method’s orthogonal array L27 examines the effect of material dynamic response factors on the pier damage level. According to Taguchi’s design of experiments, five input criteria relating to reinforced concrete bridge materials properties have been chosen as controllable factors: concrete strength, rebar strength, damping ratio, isolator pier stiffness, and abutment stiffness. The nonlinear time history approach uses Midas- Civil for a 3-D finite element model of an existing bridge at Sangli, India. The research included bridge pier collapse as a performance criterion. The analysis of variance revealed that stiffness of abutment, stiffness of pier, and damping ratio for pier deck significantly impacted the pier collapse performance. The result shows that concrete strength and damping ratio are the essential parameters, with 42% and 41% of the total contribution to pier displacement, respectively. Therefore, it is concluded that the most critical material factors for pier collapse are abutment stiffness and pier stiffness, with a contribution of 53 % and 23%, respectively.

Machine Learning-based Seismic Fragility Curves for RC Bridge Piers

A significant part of ongoing studies in the field of earthquake engineering is directed toward the seismic risk assessment of buildings and infrastructures at a territorial scale. This task is usually accomplished by grouping the structures into homogenous classes in terms of typology, for which seismic fragility curves are then obtained for different limit states via numerical simulations or from the statistical analysis of observational data when available. Particularly, the development of typological fragility curves for bridges under earthquake is useful for assessing the reliability and resilience of transportation networks in seismic areas and can be also effective decision-making support. Within this framework, the proposed study establishes a machine learning-based paradigm for the closed-form prediction of the main statistical parameters required to obtain relevant seismic fragility curves for reinforced concrete bridge piers. Initially, a huge training dataset has been obtained by Monte Carlo simulations and displacement-based bridge pier assessments by assuming data representative of the Italian highway transportation network. Next, symbolic nonlinear regression formulae for estimating the main statistical parameters of seismic fragility curves have been generated. With the aid of those formulae, the effort of calculating the seismic fragility curves is greatly reduced since the corresponding main statistical parameters can be directly calculated from a set of commonly available attributes. Therefore, the proposed study provides a helpful tool for the rapid preliminary assessment of damage and risk level of existing highway transportation networks exposed to seismic hazards.

Influence of spatially heterogeneous deterioration patterns on strength and ductility of corroded reinforced concrete bridge piers

This work reports on some preliminary results obtained within the framework of a wide research project aimed to study the influence of the corrosion of in Reinforced Concrete (RC) piers on the overall seismic performances of bridges. In this context, after the statistical evaluation of a large database of real structures, a consistent set of bridges and piers has been selected as a sample representative of typical bridge profiles, pier heights and cross-sections as well as of material properties. In the first part of the project, pushover analyses of isolated piers with different corrosion patterns and intensity are carried out to evaluate the residual strength and ductility of corroded piers. In the second part, nonlinear static and dynamic seismic analyses of bridges with corroded piers are carried out to evaluate the influence of the deterioration on the overall seismic performance. Due to specific environmental conditions exposure or to water percolation from the superstructures, it is often the case that corrosion is non-uniformly distributed over piers producing non-homogeneous spatial deterioration patterns. The nonlinear modeling of this type of situations represents specific challenges related to the description of the deterioration patterns and the calibration of material properties. To this end, a multi-level modeling approach based on fiber-based finite elements has been developed and implemented in a specific OpenSeesPy software that allows users to accurately model RC piers subject to arbitrary corrosion patterns, up to their ultimate limit states. In this work, a specific case study of a typical RC rectangular hollow bridge extracted from the mentioned above database subject to different corrosion intensity and patterns is studied. In particular, the influence of the corrosion-induced deterioration on residual strength and ductility are studied. Results show that depending on the intensity and on the patterns significant variations of both strength and ductility can be observed with respect to the undamaged conditions.

Seismic vulnerability assessment of reinforced concrete bridge piers exposed to chloride-induced corrosion

Existing reinforced concrete (RC) bridge piers located near the sea are vulnerable to corrosion phenomena that might negatively affect the load-bearing capacity of the overall bridge, especially under seismic loading. It is of primary importance to assess the seismic vulnerability of existing RC bridge piers under different corrosion scenarios, in order to quantify the reduction of the seismic structural safety induced by these frequent material degradation phenomena. This contribution deals with an experimental-numerical procedure for the seismic vulnerability assessment of corroded bridge piers. The procedure is illustrated in the context of the Zappulla multi-span viaduct (Sicily, Italy), whose RC piers are experiencing chloride-induced corrosion. A comprehensive quality control is conducted, including carbonation tests, corrosion potential mapping and extraction of corroded steel bars for tensile tests, in conjunction with SonReb tests and concrete coring. The test results are critically interpreted to calibrate a numerical fiber-hinge model of the bridge pier, through which numerical seismic analysis is performed under two different corrosion scenarios. It has been found that the seismic safety margin of pier structures is reduced of up to 20-40% by taking into account a mass loss in percentage of the steel bars equal to 20-30%, as suggested by experimental findings.

Performance of UHPC bridge piers subjected to heavy vehicle collisions and probability analysis of damage level

Heavy vehicle collisions have been reported as one of the major causes of normal concrete (NC) bridge pier failure due to its low crashworthiness. Ultra-high performance concrete (UHPC), which has been demonstrated as a promising engineering material to resist high strain rate loadings, is deemed as an alternative material to improve the collision performance of bridge piers that would be impacted by heavy vehicles. In this study, the performance of the UHPC pier subjected to heavy vehicle collisions is investigated by using the finite element (FE) modelling approach. Firstly, the damage and energy absorption characteristics of NC and UHPC piers are comparatively studied. The results show that the NC pier is dominated by plastic failure, whereas the UHPC pier essentially presents brittle damage. The kinetic energy of the vehicle is mainly dissipated by the steel reinforcement for UHPC piers whereas by the concrete for NC piers. Then, a comprehensive parametric analysis, with respect to the vehicle weight and velocity, pier diameter, and longitudinal and transverse reinforcement ratios, is performed to investigate the impact performance of UHPC piers. An analysis of the Pearson correlation coefficient for the involved parameters shows that the vehicle weight and velocity are key influential parameters to the peak impact force. Finally, to facilitate the evaluation of the bridge column subjected to heavy vehicle collisions, three regression surrogate models, SVR (support vector regression), kriging, and RBF (radial basis function), are established to predict the equivalent static force (ESF) of the peak impact force on UHPC piers with promising accuracy. Among the presented five damage levels, the probabilities of slight and moderate damages are remarkably larger when UHPC piers are impacted by heavy vehicles. This study can provide guidance for the revision of AASHTO and future engineering practices with considering UHPC piers subjected to heavy vehicle collisions.

Non-parametric and parametric damage indices through a case-study of a reinforced concrete bridge pier

Parametric indices are empirically related to two or more response parameters with a combination coefficient and do not conform to a physical definition of damage. The combination parameter is expected to be contingent on the loading and the state of calibration other than failure. Damage is also defined as the ‘deterioration of a physical quantity’ and the resulting non-parametric index does not involve any empirical constant. However, the non-parametric indices saturate much before unity. This paper first aims to assess the performance of some of the existing non-parametric indices. Experimental response until failure of a circular RC bridge pier under cyclic loading is numerically simulated for this purpose. A new physical-definition based non-parametric damage index is proposed. Setting this alternate definition as the benchmark, performance of parametric Park-Ang index, some of its variants and other non-parametric indices are studied at levels other than failure through a damage progression analysis using cyclic and seismic excitations. A parametric index and its simplified form consistent with that physical-definition are next proposed with weighted-hysteretic-energy and normalized-deformation as parameters. The same calibrated model is used in subsequent assessment. Associated combination-coefficient exhibits a stable relationship with peak drift and a loading-independent functional form is proposed.

Experimental study on the seismic performance of self-centering bridge piers incorporating ECC and superelastic SMA bars in the plastic hinge regions

The seismic performance of pier columns is important to the safety of bridge structures. To improve the deformation capacity and energy dissipation, reduce the residual deformation and plastic damage, and resume normal functions with no or minimal repair after an earthquake, an innovative pier column with self-centering capability based on shape memory alloy (SMA) and engineered cementitious composites (ECC) was proposed. In the plastic hinge region of the pier column, SMA bars and ECC were used to replace the ordinary longitudinal reinforcements and concrete. The superelasticity of SMA can be used to achieve the self-centering function of the pier column; the strain hardening characteristic of ECC can improve the energy dissipation capacity of the pier column and reduce damage. Five specimens were produced, i.e., ordinary reinforced concrete bridge pier (R/C-BP), reinforced ECC bridge pier (R/ECC-BP), steel strand reinforced concrete bridge pier (SS/C-BP), steel strand reinforced ECC bridge pier (SS/ECC-BP) and SMA bar ECC bridge pier (SMA/ECC-BP). After low cycle repeated loading tests, the seismic performances of different piers, such as failure mode, bearing capacity, ductility and energy dissipation capacity, were compared and analyzed. The test results show that SMA material can significantly improve the deformation ability and ductility of the structure and reduce the residual deformation of the structure; ECC material can effectively improve the ductility and energy dissipation capacity of the structure and reduce the speed of cracking. Compared with ordinary reinforced concrete specimens, SMA/ECC pier columns were less damaged with better ductility and self-centering effects and exhibited excellent seismic performance.

Investigation of the performance of grouted couplers in vehicle impacted reinforced concrete ABC bridge piers

Increased dynamic impact on bridge piers caused by seismic events, blasts, and vehicular impact have become increasingly common. Recent research efforts indicate that code provisions for designing reinforced concrete members to withstand such dynamic loads are inadequate and need additional insights for this purpose. Numerous works have been undertaken to investigate reinforced concrete (RC) traditional bridge pier performance on high strain rate loading. However, little attention has been given to evaluate the performance of connections used in present day bridges including accelerated bridge constructions (ABC) to withstand vehicle impacts, and hence, is relatively unknown. In this study, the use of grouted couplers to contain the unbalanced moments resulting from vehicular impact forces exceeding the moment capacity of the reinforced concrete piers and avoiding extensive damage to the piers is investigated. A representative column, typical of those specified by state departments of transportation, is studied to determine the performance. The performance of the coupler is investigated for both dynamic and static combined stresses. Quasi-static to dynamic strain rates of steel reinforcement connected to the couplers is also evaluated. Quantifying the stresses and strains developed at coupler region from dynamic impact can help coupler manufacturers to optimize the strength properties, thus improving serviceability. This study investigated utilizing splice sleeves in mitigating the formation of plastic hinges, as well as addressing the essential properties of coupler sections required to adequately carry out this function, and will provide a useful design tool for the manufacturers, forensic structural engineers, and practitioners.

Damage characterization and resilience optimization of reinforced concrete bridge piers under vehicle impact

Vehicle impact creates a dynamic loading condition at high strain rate exhibiting a unique interaction with the resisting structural members’ material properties. This interaction results in an increase in the material’s strength properties, a behavior captured in analysis via the computation of a strength factor known as the dynamic increase factor (DIF). In reinforced concrete (RC) bridge piers, the concrete cover receives the initial impact from the vehicle, causing damage to this exterior surface. This makes the DIF related to the concrete material (i.e., the compressive DIF) particularly important in this initial phase of the crash scenario; thus, requiring an in-depth analysis into its effect on the performance of the pier during and after the impact event. This study initiates an investigation into the influence of the compressive DIF on the performance of RC piers under impact from vehicles classes. Of particular interest is estimating a post impact residual capacity for the pier, while also determining concrete strength parameters (compressive strength) that offers a good tradeoff between the shear capacity which primarily resists the impact loads, and the axial capacity which controls the principal serviceability of the pier. The resulting analyses, using a representative test pier, show that an optimal compressive strength of concrete will minimize loss in the residual capacity of the pier. The effect of the compressive DIF on other important design parameters, i.e., bond strength and development length is also scrutinized. This study will aid forensic structural engineers in scrutinizing the post impact concrete behavior and serviceability.

Dynamic Behavior of Rocking Concrete Bridge Piers Subjected to Vehicle Collisions

Dynamic Behavior of Rocking Concrete Bridge Piers Subjected to Vehicle Collisions

Dynamic Behavior of Rocking Concrete Bridge Piers Subjected to Vehicle Collisions

Dynamic Behavior of Rocking Concrete Bridge Piers Subjected to Vehicle Collisions