Accelerated Bridge Construction Research Articles

Cyclic Tests and Analysis of Corroded Precast Concrete Column-to-Footing Connections Constructed with Accelerated Bridge Construction Methods

Cyclic Tests and Analysis of Corroded Precast Concrete Column-to-Footing Connections Constructed with Accelerated Bridge Construction Methods

Evaluation of seismic performance and damage characteristics of column-footing joints with shallow socket connection

In the background of the high demand for accelerated bridge construction (ABC), more detailed research is still needed on the connection method of prefabricated columns in high-intensity areas to facilitate on-site construction and reduce costs. Therefore, this study proposed a shallow socket connection method suitable for column-footing joints and the Ultra High-Performance Concrete (UHPC) is filled with the gap between the column and footing. A shallow socket connection column and a shallow socket-corrugated pipe hybrid connection column were constructed with a socket depth of 0.6 times the column diameter, and a quasi-static test was conducted to investigate their seismic capability. As a comparison specimen, a cast-in-place (CIP) specimen was also tested, and the scale ratio of all specimens is 1:2. Finally, to predict the damage mode and capacity of the shallow socket column, a simplified strut-and-tie model was developed through mechanical analysis. The proposed shallow socket-corrugated pipe hybrid connection column has the seismic performance not weaker than that of the CIP column and shallow socket connection column, and even performs slightly better in terms of energy dissipation capacity, making it more suitable for moderate and high-intensity areas based on experimental results. The established model of the socket joints could reflect the force characteristics of the shallow socket column and calculate the lateral forces of the column under different damage conditions to determine the modes of failure.

Bond-slip behavior of steel reinforcing bars in ultra-high performance concrete for field-cast connection of precast bridge decks

In Accelerated Bridge Construction (ABC), Ultra-High Performance Concrete (UHPC) is often used for connecting precast concrete bridge components, including deck portions of the Deck Bulb-T girders. An alternative low-cost non-proprietary UHPC has been proposed for use in place of the proprietary UHPC for connecting the precast components. The pullout behavior of steel reinforcing bars in closure pour with typical range for embedment lengths is studied for both proprietary and non-proprietary UHPC materials.

Sustainability and Resiliency Investigation of Grouted Coupler Embedded in RC ABC Bridge Pier at Vehicle Impact

Increased occurrences of natural and man-made dynamic loading caused by high strain rate dynamic impact load have been recently reported. Different statistical results indicate that vehicular impacts occur more frequently compared to the other dynamic loads. However, existing literature primarily focuses on enhancing survivability and determining damage levels specifically in relation to faster bridge construction methods used as an accelerated bridge construction (ABC). In this context, the present study investigates the dynamic behavior of a commonly used connection type in ABC, namely grouted coupler that connects pre-cast elements like bridge piers and foundations. To execute the research, both the static and dynamic performance of grouted couplers embedded in pier foundation subjected to high strain rate loading incurred by high velocity vehicular impact are examined. A representative non-traditional reinforced concrete (RC) bridge pier is selected for the study with the standardized geometry and selected material properties. The use of splice sleeves as coupler materials and specified cross-sectional hollow cast iron cylinders filled with high strength concrete grout is employed for developing Finite Element (FE) modeling, extracting data from published journals. A commercial software, ANSYS, has been utilized to develop FE models to capture post impact respective static and dynamic behaviors, and the simulation results are then compared with the analytical. This also includes determining material performance via FE simulations. By considering dynamic loading, the dynamic impact factor (DIF) has been evaluated for the reinforcing steel bar adjacent and embedded into the coupler. In addition, dynamic simulations, and material modulus in demand to sustain impact are determined. Thus, the research necessitates mesh-independent sensitivity studies to investigate DIF corresponding to the precise outcomes. The findings of this study manifests valuable information that aids to opt for the suitable coupler connections, considering material properties, and adequate post impact execution. Consequently, it will serve as a useful design tool for design offices, structural practitioners, and forensic structural engineers.

Seismic column-to-footing connections reinforced with steel/GFRP bars and GFRP spirals

Hybrid reinforcement is explored for column-to-footing connections in seismic regions constructed with grouted duct connections as an accelerated bridge construction method. Two 38% scale precast concrete column-to-footing specimens were built; the first column was reinforced with hybrid reinforcement using a combination of mild steel and glass fiber reinforced polymer (GFRP) longitudinal bars, and the second with all-steel longitudinal bars. Double layers of GFRP spirals were used to provide improved concrete confinement for both columns; GFRP spirals exert higher levels of confining pressure on the column concrete core as deformation increases due to their elastic nature compared to steel spirals that yield. An equation was developed for the cross sectional area and pitch of a GFRP spiral to provide the same confining pressure as a steel spiral. The purpose of the cyclic load tests was to show that the column reinforced with hybrid reinforcement could reduce residual displacements using the elastic nature of GFRP bars. Pull-out tests of GFRP bars inside grouted ducts were carried out to determine the minimum embedment depth to achieve GFRP bar tensile strength. The seismic performance of both specimens was examined under quasi-static cyclic loads. The hybrid column reached a drift ratio of 9.0% drift ratio when a GFRP longitudinal bar fractured in compression; the all-steel column reached a drift ratio of 11.0% when two longitudinal steel bars fractured in tension. The elastic nature of the GFRP longitudinal bars provided substantial self-centering ability and reduced the residual displacement of the hybrid column compared to the all-steel column, thus enhancing its seismic resilience.

On the collapse of a post-tensioned reinforced concrete truss bridge during the construction phases

On March 2018 a post-tensioned reinforced concrete (RC) truss bridge, built inside a North American university campus using the Accelerated Bridge Construction (ABC) method, collapsed during the construction phase, while the bars of a diagonal member were being re-tensioned. This process was not part of the scheduled construction phases, but it was decided by the designers after having observed several cracks in the structural nodes.This paper aims to analyse the final design of the bridge useful to determine the hypothetical causes of the collapse. Several numerical analyses have been performed to reproduce the behaviour of the different structural elements during the construction phases. In particular, construction stage analyses have been carried out to obtain the internal actions acting on the structural elements and on the nodes during the different construction steps and in order to analyse in detail the critical phases where the occurrence of the collapse has been hypothesized. The collapse mechanism is identified in the shear failure of a node of the concrete truss during the re-tensioning of a diagonal element. In fact, the reapplication of the post-tension had increased the axial force of the diagonal and consequently the shear action on the node. Moreover, the results obtained have shown that the bridge has never been in safe conditions, mainly because the interface surface of the cold joints had not undergone any type of work and remained smooth.

Seismic performance of Fe-SMA prestressed segmental bridge columns with 3D printed permanent concrete formwork

The integration of digital fabrication technology with prestressed segmental column construction offers significant potential for accelerated bridge construction with material-efficient design. This study aims to explore this potential by developing a novel prestressed segmental column system that utilizes permanent 3D printed concrete (3DPC) formwork for column segment fabrication. Prestressing is achieved in the proposed system by using partially bonded iron-based shape memory alloy (Fe-SMA) reinforcement. Large-scale experiments were conducted on two columns under combined gravity and lateral loading to evaluate the seismic performance and feasibility of the proposed system. The ratio of steel to Fe-SMA reinforcement in the column design was the variable considered in this study. The experimental results showed that the columns could withstand lateral drifts of up to 5% without collapse and the permanent 3DPC formwork showed no premature failure or delamination. Furthermore, the columns exhibited self-centering characteristics, maintaining a residual drift of 1% up to a target drift of 4% when the reinforcement ratio of steel to Fe-SMA rebars was 0.3. The results highlight the potential of the proposed prefabrication concept in designing material-efficient and seismically resilient bridge columns with low damage characteristics.

Repairable Precast Concrete Bridge Columns for Seismic Events

In multispan bridges excited by ground shaking, columns are usually the target ductile members. Although current practice is successful in attaining the no-collapse objective for bridges, columns are usually damaged at displacements associated with this performance level. Minor damage can be repaired, but excessive damage is usually beyond repair. A new design paradigm with minimal damage and repair need is gaining interest. The benefits of such a design can be increased if low-damage technologies are combined with accelerated bridge construction techniques. The main goal of the present study was to develop rein¬forced concrete bridge columns that are fully precast concrete, low damage, and repairable through compo¬nent replacement. To achieve the project objectives, 20 repairable precast concrete alternatives were developed and ranked. Subsequently, the top three candidates were designed at 50% scale, constructed at a precast concrete plant, and tested in a laboratory. The precast concrete columns incorporated different exposed fuses, such as stainless steel bars and steel tendons, advanced materials such as ultra-high-performance concrete, a self-centering mechanism, or an accelerated bridge construction socket connection. A reference cast-in-place concrete column was included for comparison. Each precast concrete column was tested twice. It was found that the repair of the precast ultra-high-perfor¬mance concrete columns with exposed tendons was easy,

Evaluation of minimum flexural reinforcement for precast prestressed concrete NEXT beam bridges

The minimum flexural reinforcement requirement has been used in the current bridge design specifications to protect the member from brittle failure after the formation of the first flexural cracks. Several variables have been reported to affect this requirement, such as concrete strength, amount of prestressing in the member, and type of cross section. Recently, the Precast/Prestressed Concrete Institute (PCI) developed a new type of beam section (NEXT beam) to accelerate bridge construction and enhance the sustainability of bridges. As a newly developed beam section, no research on the minimum flexural reinforcement has been reported for NEXT beam bridges. This paper aimed to examine the minimum flexural reinforcement requirements in the current AASHTO LRFD Bridge Design Specifications for NEXT beam bridges. A comprehensive parametric study was analytically conducted with various parameters, including bridge section, beam section, concrete strength, and span length. The results from this study showed that the current minimum flexural reinforcement requirements were met for all bridges examined herein; the concrete strength, beam cross section, and span length could affect the levels of safety against brittle failure after first flexural cracks for NEXT beam bridges.

Numerical analysis of high-strength centrifugal precast RC hollow pipe columns using grouted corrugated duct connection: Confinement effect and ductility evaluation

High-strength centrifugal precast (HSCP) reinforced concrete (RC) hollow pipe columns using grouted corrugated duct connection (GCDC) is a novel structure form in accelerated bridge construction (ABC). Nevertheless, the confinement effect of the HSCP hollow column core concrete provided by single-layer transverse rebar and its impact on ductility is not clear. Therefore, in this paper, the confinement effect and the ductility of hollow columns is studied using finite element analysis (FEA) method. A modified model is established to evaluate the constitutive relation of the core concrete confined by single layer transverse rebar. Based on the modified model, a simplified fiber model for predicting the hysteric response of HSCP hollow pipe column using GCDC, which considers bond-slip effect in GCDC joint was developed. The results indicate that the confinement effect of HSCP hollow pipe column is sensitive to the wall thickness ratio. When the wall thickness ratio decreases, the ultimate strain of the core concrete significantly decreases, while the effect on strength is not significant. The simplified model which considers confinement effect is more accurate in predicting the ductility of HSCP hollow columns. It proves that the weak confinement effects can lead to early cracking of the inner wall of hollow columns, which leads a significant impact on the ductility of HSCP hollow columns. Based on the parametric analysis, the peak load of the hollow column increases by 16.7% when the wall thickness ratio rises from 0.1 to 0.2, but only slightly changes when the wall thickness ratio is increased beyond 0.2. The wall thickness ratio of HSCP hollow pipe columns should be set above 0.2 to ensure the strength and ductility. In addition, a ductility evaluation method and a design example were developed to guide preliminary ductile design of HSCP hollow columns.

Analytical investigation of multi-joint rotation behavior of PTPS-CFDST column under lateral loading

The post-tensioned precast segmental concrete-filled double-skin steel tube (PTPS-CFDST) column is an innovative composite column that has recently been proposed and verified to exhibit excellent seismic resilience performance, being a promising solution for low-damage seismic design in accelerated bridge construction. Under lateral loading, this type of new column behaves with multiple joint rotations with laterally unconstrained post-tensioned (PT) tendons, which cannot be accurately predicted by the existing analytical models. This study firstly presents a new multi-joint rotation analytical model for the PTPS-CFDST column under lateral push-over loading, with the positional influence of PT tendons considered. The proposed model is then validated against experimental and numerical results, demonstrating its accurate prediction of lateral force capacity, global column deformation, and local joint openings. In addition, a comparison between the one-, two- and three-joint analytical models is conducted, and the results reveal that the two- and three-joint analytical models achieve accurate results. Finally, parametric studies considering the initial prestressing force, thickness of steel tube and hollow ratio are performed, which further validates the accuracy, applicability, and versatility of the proposed model. This research enhances the analytical understanding of the multi-joint rotation behavior of the PTPS-CFDST column, which may provide references for the seismic design of this new type of column.

Cyclic performance of prefabricated composite shear stud connectors for accelerated bridge construction

This study examines the cyclic shear-slip performance of a novel prefabricated composite shear stud (PCSS) connector designed for accelerated bridge construction (ABC) of composite structures. An in-depth experimental procedure is employed involving the design and fabrication of four push-out specimens with two different stud configurations. The specimens are then tested under both monotonic and cyclic-to-monotonic loading protocols. Upon completion of the testing phase, a meticulous inspection of the fractography is conducted to delineate and qualify the failure mode of the PCSS connectors. Simultaneously, a comprehensive shear-slip curve is derived from the measured data, enabling a detailed analysis over the mechanical performance. Furthermore, the study calculates a series of deformation-associated indicators from the shear-slip curve, effectively quantifying the ductility, recoverability, and capacity of the PCSS. The test results accentuate a well-deformed and ductile failure mode of the tested PCSS specimens, marked by the stud fracture and crushing of surrounding concrete. This could be attributed to the constraint of vertical plates of the PCSS on the concrete, which improves the capacity and recoverability of the PCSS. Whereas, the performance of the PCSS is also notably influenced by the group nail effect, for which the ductility and per-stud capacity degrade with the increase in the number of studs. Especially, the PCSS specimen exhibits full elastic-to-plastic hysteresis loops under cyclic loads, together with the satisfied ductility, implying an excellent potential of the PCSS to dissipate energy under impact loads. In addition, the PCSS displays a robust stiffness across different cyclic loading blocks. Hence, satisfactory post-damage ductility has still been observed in the PCSS under the monotonic loading after the cyclic loading. In conclusion, this work elucidates the superiority of the PCSS in terms of capacity, ductility, and recoverability, providing a promising basis for their application in the accelerated construction of composite bridges.

Design and Performance Evaluation of the Curved Hengjiang Avenue Pedestrian Bridge: Y-shaped Piers and Mixed Decks

Urban pedestrian bridges should contribute to the improvement of the overall image and function of the place where the footbridge is located. In order to establish a complete pedestrian access area of a Green Belt Park, an elegant pedestrian landscape bridge with Y-shaped piers and mixed decks was designed and built, providing an open and diverse viewing experience. Accelerated bridge construction technologies were adopted to build the footbridge. Finite-element models, including the full bridge model and local model, were established and a continuous rigid frame and continuous girder composite bridge system was proposed after scheme comparison. Preliminary statics and dynamics analysis, as well as detailed calculations for the local stresses of Y-shaped piers and the shear lag effect of the deck, were carried out aiming to demonstrate its safety and suitability.

Experimental-analytical investigation of accelerated bridge construction concrete columns with self-centering Fe-SMA bars subjected to near-fault ground motions

Excessive seismic damage and residual deformation in bridge piers can result in time-consuming post-earthquake repair and replacement, which will adversely affect the recovery and seismic resilience of the transportation infrastructure. Seismic damage or permanent deformation in bridges can be minimized using advanced materials and novel technologies, of which shape memory alloy (SMA) has gained substantial momentum. The goal of this study is to investigate the feasibility of using unbonded iron-based shape memory alloy (Fe-SMA) bars as self-centering elements in accelerated bridge construction (ABC) piers to reduce residual seismic deformation. Shake table testing is performed on a one-third-scale bridge column specimen subjected to near-fault ground motions. A numerical model of the test specimen is developed in OpenSees, and the “pre-test” analysis results are compared with the experimental measurements. Acceptable correlations are observed between the simulated and measured residual drifts, accelerations, forces, and hysteretic responses. Furthermore, the test results are compared to that of a similar conventional cast-in-place RC column without self-centering elements. The maximum residual drift ratio in the tested Fe-SMA column specimen is found to be much smaller than the conventional column specimen highlighting the potential benefits of the proposed design.

Study on Flexural and Shear Behavior of UHPC Rhombus-Strip-Shaped Joint

Accelerated bridge construction (ABC) has many advantages for bridge construction in modern society. While for ABC, the post-cast joint is always the weakest and most critical part. This paper presents a UHPC rhombus-strip-shaped (RSS) joint suitable for ABC. Several model tests were carried out to verify its resistance to flexural and shear. First, large-scale model tests are advanced to confirm its flexural properties. The results show that densified and welded joint interface rebars can significantly improve the ultimate bearing capacity and durability-based cracking stress of the RSS joint beams, and the ultimate bearing capacity can reach 90% of the complete beam. Then the shear-resistance tests were carried out. The results show that the UHPC RSS joint beam has excellent bending-shear mechanical properties and better ductility. Lastly, the ultimate flexural bearing capacity and shear-resistance capacity calculation methods were obtained.

Segments arrangement effect on improvement of self‐centering precast post‐tensioned segmental piers seismic performance

AbstractIn bridge engineering, the use of precast post‐tensioned segmental (PPS) piers is increasingly expanding due to the Accelerated Bridge Construction viewpoint. Recent experimental and numerical researches have studied general seismic performance and nonlinear behavior of PPS piers without much attention to segment arrangements or joint openings. The aim of this paper is to utilize innovative segment arrangements to reduce the residual deformation, without reducing the energy dissipation capacity of PPS piers with internal energy dissipation (ED) bars. For this purpose, nonlinear rocking dynamics of a multiple‐block assembly of tied rigid rocking blocks equipped with ED bars at joints are firstly developed so that uplift moment for each joint is derived to obtain the threshold joint opening height (height above which no joint opens). Then, nonlinear static, quasi‐static, and dynamic analyses are conducted on different segment arrangements of finite element models of PPS piers. It is proposed to place more segments within the threshold joint opening height by using unequal segments so that the total rotation is shared among critical joints (joints that open), and the nonlinear extent of ED bars at the bottom joint is reduced, resulting in the reduced residual deformation. It is also proposed to place a lower ratio of ED bars at the critical intermediate joints or place ED bars of a lower yield stress there so that the intermediate joints can be more effective even with small rotations. Results indicate that using the proposed segment arrangement, enhances both seismic and post‐earthquake performance of PPS piers.

A Fully Precast Pier System for Accelerated Bridge Construction in Seismic Regions

A Fully Precast Pier System for Accelerated Bridge Construction in Seismic Regions

Experimental and Numerical Study on the Seismic Performances of Reinforcement-Embedded RC Column-to-Precast Cap Beams with Socket Connections

Accelerated bridge construction (ABC) has attracted much attention in China as a new and efficient construction method. However, the seismic performance of the connections between precast piers and other structures limits the application of ABC in medium and high seismic zones. In this paper, a quasi-static test was conducted to investigate the seismic performance differences between a cap–column socket connection (PSC) specimen, which reinforced an embedded RC column-to-precast cap beam with a socket connection, and a cast-in-place (CIP) cap–column specimen. A fiber-based finite element model that considers bond slippage between the connection reinforcement and wet joint concrete is proposed. The numerical simulation results compared with the experimental results show an error of about 12% in peak bearing capacity and about 2% in initial stiffness. The experimental and numerical results show that the PSC specimen demonstrates comparable seismic performance to the CIP specimen. Experimental results verified that the finite element model in this paper is adequate to predict the seismic responses of a precast column with a reinforcement-embedded socket connection. A reinforcement-embedded RC column-to-precast cap beam with socket connection can be an effective solution for construction in medium and high seismic areas.

Study on flexural and shear performance of ultra‐high performance concrete prefabricated pi‐beams

AbstractUltra‐high performance concrete (UHPC) prefabricated beams are competitive in accelerated bridge construction. However, their broader application has been hindered by limited large‐scale tests and inaccurate design methods. To fill this gap, the authors conducted an experimental investigation on the shear and flexural performance of UHPC pi‐beams using two full‐scale specimens. One specimen was a precast UHPC beam, while the other was a composite beam with a normal concrete slab on the UHPC beam. The primary focus was on crack propagation, ultimate capacities, and failure modes. To complement the experimental findings, the extended finite element method (XFEM) was developed as a numerical approach. Nevertheless, relying solely on XFEM to understand real structural behavior is prone to misinterpretations. Moreover, the shear and flexural capacities were evaluated using existing codes and compared with the experimental results. The comparisons revealed that the predictions of shear capacities were at least 15% lower than the experimental values, whereas the flexural capacities showed acceptable agreement. To address this, the authors introduced the limit equilibrium method, leading to a more accurate prediction of shear capacity for UHPC beams with a deviation of <2%.

Development of fully dry-connection for prefabricated hollow section CA-RPC pier

To facilitate accelerated bridge construction, a dry-connection was proposed for the prefabricated hollow section coarse aggregate reactive powder concrete (CA-RPC) pier. An enlarged part was designed at the bottom of the pier to tolerate 24 high-strength prestressed reinforcement (HSPR), which were anchored in the cap. By apply the prestress in the HSPR, the prefabricated pier could be fixed on the cap and transfer axial load, shear force and bending moment. To explore the performance of the novel dry-connection, a full-size specimen underwent a pseudo-static test, and specimen delivered satisfactory stiffness, strength and ductility, which was comparable to the in-site casting pier. The failure mode of the specimen and the strain development of the HSPR verify the reliability of the dry-connection. An analytical model was proposed to describe the performance of dry-connected pier. Finally, the design suggestion was derived to guarantee the ductility of the dry-connected hollow CA-RPC pier.