Adjacent Girders Research Articles

Improved theoretical calculation method for the transverse load distribution of wide bridges considering torsion and distortion

An improved theoretical calculation method was proposed to determine the transverse load distribution of airport and highway bridges under heavy loads using the rigid-joint girder (RJG) method. The effects of torsion, distortion, and vertical inclination of the adjacent box girder joints under an eccentric heavy load were considered. The coefficients and influence lines of a taxiway bridge and a highway bridge were calculated using the proposed method, the RJG method, and the modified RJG methods. The accuracies of the three methods were evaluated by the refined finite element model, and the cosine similarity and peak deviation rate were used as quantitative indices. The results showed that the cosine similarity obtained from the proposed method for the taxiway bridge was 0.996 compared with the finite element method (FEM). The maximum peak deviation rate of the transverse load distribution coefficient for the proposed method was 14.88 % and obviously lower than 34.74 % for the RJG method. For the highway bridge, the cosine similarity of the influence line derived from the proposed method was 0.995, and the maximum peak deviation rate of the transverse load distribution coefficient for the proposed method was 6.66 % and lower than 16.14 % for the RJG method. The results indicate that the proposed method can be used to calculate the transverse load distribution of wide box girder bridges accurately and efficiently.

Shaking table test of the seismic performance for railway simply-supported girder bridge isolated by self-centering bearing

In order to solve the problem of the residual displacement of a railway simply-supported girder bridge and realize the aim of a rapid recovery in traffic after earthquake events, we designed a self-centering seismic isolation bearing and created a typical simply-supported girder bridge model with 1/10 ratio. Three peak ground acceleration (PGA) shaking table tests were performed, with the test procedures further described in detail. The test results show that the bearing provides an overall good self-centering performance. Other than the case of a 0.5 g transverse earthquake, where the bearing remains outside of the sliding surface and therefore cannot be self-centering, all the tests show that the bearing is completely self-centering. At the same time, during all the earthquake scenarios, the main structure of the bridge was not damaged in any discernable way, the longitudinal frequency did not change, and the transverse frequency decreased given that the bearing remained outside of the sliding surface. In addition, it was found that the large bearing displacement in the longitudinal direction may lead to a collision of adjacent girders, resulting in a sharp increase in the acceleration of the girders. In cases without collisions between the girders, the acceleration of the girder is effectively reduced compared with the acceleration of the pier top. The results also show that the pier can be effectively protected by the self-centering bearing, as well as indicating that the reinforcement strain of the pier does not reach the yield value under all tests. Due to the large displacement of the bearing, it is necessary to increase the allowable displacement or install a limiting device. Finally, the finite element model (FEM) of the test model is established, with the calculation results compared with the test results, in this way proving the correctness of the FEM and providing a reference for designing the seismic isolation of the railway simply-supported girder bridge.

Effects of wind barriers on the aerodynamic characteristics of twin-separated parallel decks for a long-span rail-cum-road bridge

The aerodynamic characteristics of twin-separated parallel decks for long-span rail-cum-road bridges with various wind barriers clamped at railway girder are more complicated because of aerodynamic interference. Experimental investigations on aerodynamic coefficient and wind pressure coefficients of twin girders under different incoming flow directions were conducted using wind tunnel tests. Three different heights ( H) varying from 2 m to 4 m and four different ventilation ratios ( R) varying from 20% to 50% for wind barriers were examined. Results indicated that the aerodynamic coefficients were affected significantly by the incoming wind direction, which must be considered, and the railway wind barrier affected the aerodynamic characteristics of the railway girder when it is located both upstream and downstream, but the laws are not the same. Due to the aerodynamic interference effect of the twin parallel girders, the aerodynamic characteristics of the adjacent highway girders were also affected by the wind barrier along the railway girder, especially when the highway girders were located downstream. While, the highway girders were less affected when located upstream. The influence of wind barrier height and ventilation ratios on the adjacent highway girders was completely different. Most importantly, the parameters optimization of wind barriers clamped at railway girders should be determined after a comprehensive evaluation of the aerodynamic characteristic of both the railway and highway girders.

Investigating UHPC in deck bulb-tee girder connections, part 2: Full-scale experimental testing

Deck bulb-tee girders constitute an excellent precast concrete bridge element system for medium- to longspan bridges. The precast concrete girders are transported to the jobsite, where they are placed adjacent to each other. The girders are connected using field-cast longitudinal joints. When required, a continuity diaphragm over the pier is used to create moment continuity; however, there is a risk of cracking of the field-cast joints and construction can be difficult when adjacent girders have different camber profiles. Given these challenges, adoption of the deck bulb-tee girder systems has been limited. Analytical investigation performed in part 1 of this series of papers indicated that using ultra-high-performance concrete (UHPC) can improve the performance of the field-cast joints and help overcome construction difficulties. This paper describes full-scale experimental testing performed as a follow-up to the analytical investigation. Longitudinal joints grouted with UHPC were tested under a combination of thermal and live load. A continuity diaphragm with partial UHPC was also tested under positive and negative moments over the pier.

Theoretical Method to Predict Internal Force of Crossbeam in Steel–Concrete Composite Twin I-Girder Bridge under Torsional Loading

During the operational phase of a bridge, the crossbeam, acting as a supporting member, plays an important role in keeping the cross-sectional shape constant in addition to resisting against various lateral and longitudinal loads and distributing the dead and the live loads to the adjacent main girders. The complex functional requirements lead to a complex internal force composition of the crossbeam. When subjected to torque, the two main beams of the twin I-girder bridge will have deformation in opposite longitudinal directions (known as warping deformation) to counteract the torque. The existing research has not considered the impact of main beam warping deformation on the internal force of the crossbeam. Based on the existing research, this article further considers the impact of main beam warping deformation on the internal force of the crossbeam, making the calculation of the internal force of the crossbeam more accurate. The results show that the torsional characteristics of the continuous twin I-girder bridge can be calculated using Vlasov’s theory of thin-walled structures combined with the displacement method. As for the effect of the crossbeam on the torsional stiffness of the structure, it can be managed by making the crossbeam stiffness continuous; however, in general, the equivalent stiffness is small compared to the stiffness of the main beam and it can be ignored. The crossbeam can be simplified to a bar with two solid ends for the internal force calculation whose formula is proposed in this paper, based on the existing frame model, and it can further consider the influence of warping deformation of the main beam on the internal force of the beam, and the calculation accuracy is high.

Simplified design method of pounding-unseating-prevention device for LRB isolated continuous girder bridge

Although cable restrainer and pull rod restrainer can reduce the seismic response of bridge structures to a certain extent, they cannot have good restrain and anti-pounding functions simultaneously. This paper proposes a simplified design method of a pounding-unseating-prevention device composed of rubber buffer block and steel block. The iterative design method of the device based on the pounding force response spectrum is studied according to the two-dimensional simplified analysis model of the isolated continuous girder bridge. The simplified design method considers the influence of factors, such as the difference in the dynamic characteristics of adjacent structures, ground motion characteristics and site conditions, through the pounding force response spectrum. To evaluate the effectiveness of the design method, nonlinear time history analysis is conducted on the lead rubber bearing (LRB) isolated continuous girder bridge with pounding-unseating-prevention device. The effectiveness of the device and the rationality of the design method are verified by comparing the relative displacement of the pier-girder and the maximum pounding force. Results show that the device designed using this simplified design method can reduce the pounding response of the structure and avoid the pounding of adjacent girders and unseating effectively.

Study on the Structural Performance of UHPC Pavement and Hinge Joint Reinforcement for Hollow Slab Girder Bridges

To address the problem of structural performance degradation caused by hinged joints and pavement damage, we utilized actual engineering to conduct a construction study on the overall replacement of pavement and hinge joint reinforcement in ultra-high-performance concrete (UHPC) hollow slab girder bridges. A replacement and reinforcement design was developed and reconstruction was undertaken. By using UHPC and reinforcement bars, the adjacent slab girders were designed to work together under specific construction process guarantees for the characteristics of UHPC. The corresponding interface treatment and a combination of planting bars and steel mesh were necessary. According to the strain and deflection monitoring results, the overall performance of the bridge after pavement and hinge joint reinforcement was verified. The strain amplitude of the reinforcement was approximately 10 με, and that of the concrete was approximately 5 με. The deflection difference of the adjacent girder was similar, which proved that the hinge joints connect girders and transfer force effectively. All the results clearly demonstrated the positive overall effect of the UHPC replacement method. The conclusions could provide a reference for the reinforcement and reconstruction of similar projects.

Flexural Behavior and Ultimate Capacity of Adjacent Box Girders with Expansion Joint in the Parapet

Flexural Behavior and Ultimate Capacity of Adjacent Box Girders with Expansion Joint in the Parapet

Joint deterioration detection based on field‐identified lateral deflection influence lines for adjacent box girder bridges

Joint deterioration detection based on field‐identified lateral deflection influence lines for adjacent box girder bridges

Control of Difference of Seismic Response across Different Spans of high-speed railway multi-spans simply supported bridge

In this paper, the Difference of Seismic Response across Different Spans (DSR) in the longitudinal distribution of High-Speed Railway Multi-spans Simply Supported Bridge (HSRSB) under longitudinal earthquake excitation is investigated, and an evaluation method which can intuitively reflect the difference of seismic response is proposed. A feasible way to strengthen the connection stiffness between adjacent girders is proposed to control DSR. The rationality of the finite element model used is verified by comparing the numerical results with the experimental ones, showing a satisfactory agreement. Comparing the seismic response of a bridge model considering the subgrade-track constraints (BCTM) and a bridge model without subgrade-track constraints (BWTM), it is found that the DSR in the longitudinal distribution causes some new disadvantages, which are neglected in BWTM. The BCTM considering the Difference Level Controller (DLC) generates a model called BCDM. The effect of the number of span on DSR are studied based on BCDM. The analysis of this model showed that DLC suppresses the DSR and reduces the seismic response of most bridge components. It also transfers the seismic disadvantage from the bridge part to the subgrade-track structure. As it is more convenient and cost-effective to repair the base plate of the subgrade than the bridge components after earthquake seismic event, this disadvantage transfer is in favor of forming a new anti-seismic system that subgrade-track structure is used to protect the bridge part.

Moment modification factor for link slab with single beam model in jointless bridges

Link slab is the portion of bridge deck that connects two adjacent simply-supported girders. In the practical design of link slabs, the determination of their internal forces is based on the single-beam model in which the clear span is the length of deboned link slab on top of beams. It can lead to detune moments of link slabs due to the eccentricity of link slab and girders, and the interaction between link slab and girders through the deboned layer. In this paper, a numerical analysis model is established based on finite element method to investigate moment performance of link slabs. Then, moment modification factors for link slab with single beam models are suggested to allow engineers to make better decisions on the detailing of link slabs.

Moment modification factor for link slab with single beam model in jointless bridges

Link slab is the portion of bridge deck that connects two adjacent simply-supported girders. In the practical design of link slabs, the determination of their internal forces is based on the single-beam model in which the clear span is the length of deboned link slab on top of beams. It can lead to detune moments of link slabs due to the eccentricity of link slab and girders, and the interaction between link slab and girders through the deboned layer. In this paper, a numerical analysis model is established based on finite element method to investigate moment performance of link slabs. Then, moment modification factors for link slab with single beam models are suggested to allow engineers to make better decisions on the detailing of link slabs.

Experimental and numerical investigation on optimized ultra-high performance concrete shear key with shear reinforcement bars

Over the last decade, ultra-high performance concrete (UHPC) has been used in highway bridge connections between deck panels and girders due to its superior compressive and tensile strengths, significant tensile toughness, and excellent long-term durability. However, there are limited studies and discussions on the UHPC shear key's design with or without shear reinforcement bars (SRBs) applied for adjacent girder bridges. This study aimed to numerically and experimentally investigate the effectiveness and functionality of SRBs used in an optimized UHPC shear key connection (abbreviated as OPT-SK) developed by the authors in a previous study. To this end, a finite element (FE) direct shear model for Federal Highway Administration (FHWA) shaped shear key (abbreviated as FHWA-SK) was developed and calibrated first. Then, the validated FE model was extended to investigate the OPT-SK's shear behavior with SRBs. To experimentally measure the ultimate load capacity of the OPT-SK, a push-off direct shear (P-ODS) test was carried out on the OPT-SK with SRBs in both pre-crack and post-crack status. The results showed that the OPT-SK with SRBs exhibited a higher carrying load capacity, a more evenly distributed stress, and a lower stress magnitude than the FHWA-SK with SRBs. The cracks or damage mainly initiated and developed in the high strength concrete (HSC) components and the interface between the UHPC and HSC components. The P-ODS test's load-displacements or strains were reported to highlight the SRBs' effectiveness and functionality in the OPT-SK.

Behavior of steel girder bridges damaged by vehicular collision

Vehicles often collide with girders of low-clearance bridges, yet there is a knowledge gap in understanding the behavior of damaged steel girders. This paper addresses this gap by performing non-destructive field testing on four damaged steel girder bridges. The focus is on two- and three-span continuous multi-girder steel bridges for which an exterior girder has sustained Category T damage, i.e., torsion about the longitudinal direction. The behavior of damaged girders, symmetric undamaged girders, and adjacent girders under quasi-static truck loading is monitored using digital image correlation (DIC). Specifically, the measured strains of damaged girders are compared to the strains of corresponding symmetric undamaged girders to investigate the effect of the damage on behavior for each bridge. Strain gauges were used to monitor the behavior of one bridge under quasi-static truck loading, as well as speed and crawl tests. The strain gauge readings are also used to validate DIC strain measurements for field monitoring of bridges. The measured strains are used to validate finite element (FE) numerical models. A parametric study investigates the effect of varying shapes and locations of damage on the load-deflection behavior of a single girder as well as two- and three-span continuous bridges. Overall, this study found that measured strains in all girders are less than 200 microstrain or approximately 40.0 MPa (5.80 ksi). Results indicate that vehicular damage may affect composite behavior, bridge railings participate in carrying live load, damaged girders may have increased live load amplification factors, and damage at the center of a span with a large rotation angle of the web results in the greatest loss of stiffness.

Comparative study of numerical simulation methods for seismic pounding of adjacent girder of curved girder bridges

Under seismic action, non-uniform collision will occur between the main beams of curved beam bridge, which may lead to local damage of front beam or rear beam. At present, the research on collision effect is mainly based on straight beam bridge, and there is still a lack of relevant research on seismic collision of curved beam bridge. Taking two adjacent typical curved bridges as examples, this paper establishes contact elements (linear elastic model, Kelvin model and Hertz model) and solid elements (three-dimensional contact friction model) which can fully reflect the physical characteristics of seismic collision of curved bridges. By comparing the numerical simulation methods of seismic collision, the advantages and disadvantages of the existing numerical simulation methods in the seismic response analysis of curved bridges are evaluated. The results show that the calculation results of Kelvin model and three-dimensional contact friction model have the least error and high calculation efficiency, and are suitable for the seismic analysis of curved beam bridges.

Analytical Solutions for Girder Distribution Factor in Steel-Concrete Composite Girders with the Effect of Parapets

The existing studies have shown that parapets have great influence on the girder distribution factor (GDF) of bridges. However, there is no method in the design guide to estimate the GDF considering the effect of parapets. This research aims to develop a simplified method for estimating the GDF by considering the effect of parapets. First, a simply supported steel-concrete composite girder bridge was tested to investigate the effect of parapets on the GDF. Then, finite-element (FE) model was established and verified by the field test data of strain and deflection. In addition, error study showed that the bending stiffness of the bridge was increased by about 92% and 19.1%, respectively, due to the effects of parapet and continuous layer. As the effect of the continuous layer on each girder was relatively uniform, the simplified method was optimized only considering the effect of the parapet. Finally, the effect of the parapet on the GDF was compared and discussed. Considering the effect of the parapet, the GDF of the exterior girder calculated by the simplified method and FE analysis decreased by about 26.92% and 23.53%, respectively, and the adjacent interior girder decreased by about 15.22% and 12.77%, respectively. Comparing the GDF calculated by the AASHTO LRFD specifications, the GDF calculated by the simplified method decreased by about 30.77% in the exterior girder and 41.30% in the interior girder, respectively. The results indicate that the method of calculating the GDF without considering the effect of the parapet in AASHTO LRFD specifications is conservative. The GDF calculated by the simplified method was basically close to the field test results, meaning that the proposed simplified method considering the effect of the parapet was relatively accurate.

The Response of a Highly Skewed Steel I-Girder Bridge with Different Cross-Frame Connections

Braces in straight bridge systems improve the lateral-torsional buckling resistance of the girders by reducing the unbraced length, while in horizontally curved and skew bridges, the braces are primary structural elements for controlling deformations by engaging adjacent girders to act as a system to resist the potentially large forces and torques caused by the curved or skewed geometry of the bridge. The cross-frames are usually designed as torsional braces, which increase the overall strength and stiffness of the individual girders by creating a girder system that translates and rotates as a unit along the bracing lines. However, when they transmit the truck’s live load forces, they can produce fatigue cracks at their connections to the girders. This paper investigates the effect of using different details of cross-frames to girder connections and their impacts on girder stresses and twists. Field testing data of skewed steel girders bridge under various load passes of a weighed load vehicle incorporated with a validated 3D full-scale finite element model are presented in this study. Two types of connections are investigated, bent plate and pipe stiffener. The two connection responses are then compared to determine their impact on controlling the twist of girder cross-sections adjacent to cross-frames and also to mitigate the stresses induced due to live loads. The results show that the use of a pipe stiffener can reduce the twist of the girder’s cross-section adjacent to the cross-frames up to 22% in some locations. In terms of stress ranges, the pipe stiffener tends to reduce the stress range by 6% and 4% for the cross-frames located in the abutment and pier skew support regions respectively.

Shake table experimental study of curved bridges with consideration of girder-to-girder collision

It is well-known that curved bridges are vulnerable to girder unseating during strong earthquakes. This is mainly attributed to its irregular geometry and seismic pounding. In this paper, a shake table experiment was designed and conducted on a 1/25-scale model to investigate the influence of collision between adjacent girders on the seismic response of curved bridges. For this purpose, two curved bridges with an expansion joint in-between were taken as the engineering background. Three historical records including a near-fault pulse-like record, a non-pulse-like record and a far-field ground motion were used to excite the test model. The seismic responses of the tested curved bridges were discussed in detail. Impact forces were measured by three load cells installed at the expansion gap joint. To begin with, the model was excited by the near-field pulse-like record in a variety of input directions without seismic collision to identify the most unfavorable input angle of the ground motions. It was found that for the test model, the secant direction of the adjacent two piers of the single-span segment is the most unfavorable input angle for seismic excitations. It was also found that the collision frequently occurred at the corners of the girders and was non-uniform along the contact surface. In addition, the girder-to-girder collision could induce significantly large in-plane rotation of the adjacent bridges, which could substantially increase the global displacement demands of the bridges. Furthermore, the maximum total impact forces increased with the gap size from 1 mm to 2 mm and then decreased with the gap size from 2 mm to 4 mm. However, the maximum in-plane rotation decreased with the gap size from 1 mm to 4 mm regardless of the input motions. Compared with the non-pulse-like near-fault motions, the pulse-like near-fault motions can result in higher in-plane rotation and force demands due to their velocity pulses and hence are more detrimental to curved bridges.

Influence of Expansion Joints in Deck Parapets on Localized Cracking in Adjacent Box Girders

Abstract Concrete adjacent box girders are widely used in short- and medium-span highway bridges. Effects of bridge accessories, such as curbs and parapets, on the structural performance are common...

Ultra-High-Performance Concrete Shear Keys in Concrete Bridge Superstructures

This research investigated the use of locally produced, non-proprietary ultra-high-performance concrete (UHPC) as a grouting material to repair deteriorated shear keys. Shear keys are used in adjacent girder superstructures to produce monolithic behavior and load transfer across the structure. Shear key degradation can jeopardize the integrity of the structure. Transportation agencies have reported that 75% of distress in adjacent girder bridges is because of cracking and de-bonding along shear keys. Previous research has shown that locally produced UHPC has excellent mechanical and durability properties. UHPC has also been shown to have good bonding characteristics that are desirable in a potential grouting material. Bond strength between UHPC grout and substrate concrete was evaluated using slant-shear and direct tension tests. Results showed that adequate bond was achieved at 7 days. Low strengths at 28 days were observed because of low strength of the substrate concrete. Shrinkage of UHPC grout was also investigated. Shrinkage at 28 days was less than 600 µstrain which is acceptable for repair practices. Full-scale testing was used to evaluate load-deflection behavior of channel girder assemblages with grouted shear keys. Results showed that UHPC grout and non-shrink grout had similar mechanical performance. Excellent bond was achieved with all grouts, even with minimal surface preparation. The similar performances of the non-shrink grout and the UHPC grout indicates that UHPC grout does not provide a mechanical benefit over the non-shrink grout.