Behavior Of Girders Research Articles

Experimental and theoretical investigation on flexural behavior of concrete-filled tubular flange girders

Concrete-filled tubular flange (CFTF) girders offer superior torsional stiffness compared to traditional I-shaped plate girders, providing enhanced flexural performance. To accurately assess the flexural capacity of CFTF girders, both flexural tests and theoretical analyses were conducted on specimens with and without concrete decks. The experimental data were meticulously analyzed to understand the flexural mechanism, yielding sequence, interface slip, strain distribution, and confinement effect of CFTF girders. Subsequently, finite element models were then utilized to analyze the influence of cross-section dimensions and material optimization on the flexural behavior of CFTF girders. Comparative analyses with I-shaped girders were also performed to highlight the structural advantages of CFTF girders. The proposed flexural calculation formulas were validated against both experimental and analytical results, demonstrating a fitting accuracy between 95 % and 98 % for the yield moment and between 96 % and 98 % for the ultimate moment. The method proposed in this paper provides a reliable and accurate approach for evaluating the flexural capacity of CFTF girders, significantly contributing to the advancement of design and analysis practices in structural engineering.

Transverse Analysis of Box Girders with Corrugated Steel Webs

The utilisation of box girders with corrugated steel webs (CSWs) represents an innovative approach to bridge superstructure design that has garnered substantial popularity worldwide, with a notable prevalence in both Asia and Europe. Compared with traditional box girders, they avoid web cracking, improving the prestressing efficiency and bridge spanning ability. As an innovative box girder, a corrugated web can increase the cantilever length and transverse stiffness, and at the same time, it reduces the dead weight of the bridge deck. However, little research has been conducted on the mechanical properties of this novel spine-like box girder with CSWs, especially its transverse performance, although it has been used in many applications. In this paper, the effect of the web form on the behaviour of box girders is introduced. Therefore, three representative three-dimensional (3D) finite-element models (i.e., corrugated web box girder, flat web box girder, and ordinary equivalent concrete web box girder) have been established to quantitatively investigate the influence of corrugated web stiffness on transverse stress under the action of gravity and vehicle loads. Generally, significant differences in the mechanical performance of box girders with CSWs have been observed compared with conventional box girders with concrete webs. Additionally, parametric studies to investigate the influences of the corrugation dimensions (in term of the corrugation height, web thickness, panel width, web height and elastic modulus) on the transverse stiffness of such bridges are analyzed. The results show that a new stiffness formula can be put forward to consider the effect of web height, and a high-strength steel web needs to be developed urgently for box girders with CSWs in the near future. Overall, the results of this investigation can be used as a reference for transverse designing and segmental construction of similar projects.

Experimental and numerical studies on the ultimate bending moment of welded plate girder with perforated web

ABSTRACT Combined opening girders with high stiffener webs used in the superstructure areas of passenger ships are prone to complex buckling phenomena under combined longitudinal and vertical loads caused by overall longitudinal bending and vertical forces from the deck cargo. In addition, the deformation and stress induced during structural assembly and welding make the buckling behaviour more difficult to predict. In response to this situation, thermal elastic–plastic and nonlinear finite element methods were used to simulate the welding and loading process and related experiments were conducted to provide a comparison. We further extended the investigation of the buckling behaviour of girders to the combined opening plate frame and investigated the buckling behaviour using experiments. This research on the buckling behaviour of combined opening girders and plate frames could provide a reference for the optimal design of these members in actual ship structures.

Finite-Element-Based Study on Girder Behavior and Load-Sharing of Shear-Connected Multigirder Prestressed Concrete Bridges

Finite-Element-Based Study on Girder Behavior and Load-Sharing of Shear-Connected Multigirder Prestressed Concrete Bridges

Modelling of fire behavior of RC girders strengthened by external prestressing

Since the 1950s, external post-tensioning has been a powerful tool for retrofitting existing bridges. In unbonded prestressing, the post-tensioning tendons are positioned outside the concrete cross-section, and the prestressing forces are transferred to the girder through end anchorages, deviators, or saddles. This implies that these could be critical elements for the bridge performance against fire. This paper examines reinforced concrete bridges strengthened by external prestressing and subjected to fire, using a mixed experimental and analytical approach. Initially, load tests are conducted on a model of a bridge beam strengthened by external prestressing to assess the effectiveness of the intervention until failure. The ultimate limit state (ULS) capacity of the beam is then evaluated both before and after rehabilitation. Subsequently, the fire performance is investigated through different scenarios defined by the fire load curves of Eurocode, evaluating the cross-sectional temperatures resulting from fire, estimating the loss of external prestressing efficiency, and assessing the beam’s overall fire resistance. This methodology is then applied to a real girder bridge with adjacent beams of the same type, extending the approach used on the experimental scaled beam to an actual bridge deck. Results are presented in terms of performance levels for different traffic load values and residual capacity over time from fire ignition, providing a safety assessment of girder bridges under fire exposure. The procedure is straightforward and immediately applicable to many existing reinforced bridges. The findings demonstrate how quickly external prestressing degrades, leaving the beam unprotected, and highlight the fundamental importance of the protective sheath for external tendons in limiting this degradation. Evaluating load levels based on exposure time also allows engineers to estimate the service time before rescue arrives, given the expected traffic level.

An advanced assessment framework for seismic resilience of railway continuous girder bridge with multiple spans considering 72h golden rescue requirements

Given the common sense that people in danger could survive with high probability in the golden rescue time of 72 h after earthquakes, railway bridges that are important transportation hubs and the lifelines for earthquake relief have been required to satisfy the necessities of safe passage and fast traffic for emergency response personnel in this critical period. To ensure the post-earthquake temporary functionality of the railway bridges to a sufficient safety level in golden rescue scenario, an advanced resilience assessment framework, including seismic resilience determinations for individual bridge components based on residual responses with respect to the plastic capacities originated from performance limit state definitions, definitions of three recovery levels considering repair efficiency for different recovery phases, and the series-parallel and parallel-serial system resilience models developed in temporal and spatial domains, was established. A commonly constructed irregular railway multi-span continuous girder bridge was chosen to verify the practicability of the aforementioned framework. The finite-element model of the illustrative bridge was developed taking abutment-girder interaction effects and nonlinear seismic behaviors of girder into account. Average spectral acceleration was taken as the intensity measure (IM) to consider the response variations originated from higher modes and natural period extension during earthquakes, and the site-matched and IM-based scaled ground records were adopted in the multiple stripe analysis to obtain instantaneous peak and residual seismic responses. Based on the framework, post-event resilience characteristics of bridge components were discussed, four recovery strategies were proposed for bridge system, and the seismic resilience of the illustrated bridge was assessed at system level. The research shows that the response contribution of fundamental dominant mode is only 64.37 %, indicating the dynamic response contributions from higher modes are considerable and the case bridge can show a strong irregularity during seismic events. Obvious nonlinear seismic behaviors occur to the superstructure where material strain in girder critical sections can increase to 0.00422 during earthquakes, which illustrates the inaccuracy of girder modeling only taking elastic behavior into consideration. Also, the prestress loss after earthquakes can reach 31.14 % and attention should be paid to the prestress recovery in subsequent repair works. Most components can satisfy the easy recovery resilience level, and the resilience is closely related to ground intensities and repair-waiting time; earthquake-induced functionality reduction can be 46.57 %, and resilience can increase by 25.35 % if the waiting time is shortened by 5 h. System resilience is influenced by the similar factors with component and varies in cases of different repair sequences due to the accumulation effect of repair-waiting time for various subsystems.

Experimental study on mechanical behavior of steel truss-reinforced concrete box girders

This paper proposes a new design concept for a steel truss-reinforced concrete box girder which incorporates a steel truss instead of longitudinal bars and stirrups. A comprehensive assessment of the flexural and shear behavior of the proposed steel truss-reinforced concrete box girders was conducted through the testing of twelve girders until failure. All test specimens had the same concrete depth and width of 400 mm and 300 mm, but the length of concrete in the shear and flexural specimens were 3300 mm and 3100 mm, respectively. Moreover, the reinforcing steel truss configuration and member sizes were different. The effects of the angle steel size of the lower chord, vertical webs spacing, shear span ratio and presence of diagonal webs on the cracking, yield and ultimate loads, crack patterns, failure modes, vertical load-deflection curves and strain distribution of these steel truss-reinforced concrete box girders were studied. The test results showed that the flexural capacity of the steel truss-reinforced concrete box girder increases with the increase of angle steel size of the lower chord. Moreover, the spacing of vertical webs and presence of diagonal webs have little effect on the flexural capacity of steel truss-reinforced concrete box girders tested. With the decrease of the shear span ratio and vertical webs spacing, the shear capacity of the steel truss-reinforced concrete box girder increases. Finally, simplified formulae for calculating the flexural and shear capacities of steel truss-reinforced concrete box girders were proposed, showing good agreement with the experimental results.

Behavior of steel box bridge girders subjected to hydrocarbon fire and bending-torsion coupled loading

This paper presents an experimental together with numerical investigation on behavior of steel box bridge girders under hydrocarbon (HC) fire and bending-torsion coupled loading conditions. Four test bridge girders fabricated utilizing single-box configured with twin-chamber supporting thin concrete slabs, taking into consideration sectional features and loading methods, were simultaneously subjected to HC fire exposure and bending-torsion coupled loading to analyze thermal and structural response. A numerical model established through program ANSYS, validated dependent on measured data generated from fire tests, was used to conduct a parametric analysis. Results show that significant discrepancies of temperature occur in mid-web and side-web of test bridge girders exposed to HC fire. Steel top flange has a significant influence on heat accumulation and transfer inside steel box, escape of water vapour in concrete slab and also fire resistance of steel box bridge girders. Deflection difference in transverse section of test bridge girders subjected to bending-torsion coupled loading gradually become predominant with fire exposure time. Test bridge girders without steel top flange experience a wide longitudinal crack in concrete slabs instead of excessive flexural deflection through entire fire exposure duration. Increasing longitudinal stiffeners in mid-web and bottom flange can effectively enhance fire resistance of steel box bridge girders. Timely evacuation of applied loads enforced on bridge girders during fire exposure can greatly delay deflection progression. The post-fire residual bearing capacity in test bridge girders can recover more than 80 % of initial bearing capacity after HC fire exposure. The experienced maximum temperature and fire exposure time has a predominant influence on post-fire recovery ability of steel box bridge girders under ventilation cooling conditions.

Residual shear behaviour of steel-concrete composite girders after fire exposure: Experimental and numerical study

Steel-concrete composite girders are widely used for their superior mechanical performance. However, research on the shear behaviour of composite girders after fire exposure is limited. This study attempts to reveal the effects of high temperatures and cooling methods on the shear behaviour of composite girders. With heating temperatures (200 °C, 400 °C and 600 °C) and cooling methods (natural cooling and water cooling) as variables, 7 composite girders were designed. First, the composite girders were placed in the fire furnace and heated to simulate fire exposure. Subsequently, the residual shear performance of the cooled composite girders was tested and discussed. The test results show that there is a significant temperature gradient along the height of the girders during heating. High temperatures of no more than 600 °C have a more pronounced effect on the properties of concrete than steel, resulting in a progressive deterioration in the synergistic working property of the concrete slab and steel beam as the temperature increases. The deterioration of the shear performance of composite girders with natural cooling is similar to those with water cooling, probably due to the neutralization of the positive effect of water on the hydration reaction of concrete and the negative effect of the rapid reduction in temperature of the structure caused by water cooling. Further, finite element models of the composite girders were developed and thermal-mechanical coupling analysis was performed to simulate the effects of fire exposure. The parametric analysis conducted show that the steel beam web thickness is highly effective in enhancing the residual shear performance of the composite girders after fire, while the effect of the concrete slab width is relatively minor.

Fatigue behavior of girder with flange thickness transitions and cope holes ‐ tests and simulations

AbstractThe fatigue behavior of steel girders with flange thickness transition and cope hole has been experimentally analyzed with two large‐scale cyclic tests. Special attention is paid to the arising and interacting local effects. The fatigue tests have been conducted in a four‐point bending setup. Both girders have shown fatigue‐induced failure at the flange butt welds at the thickness transition. The experimental results are presented in terms of fatigue life, differentiating the initiation and propagation life, as well as observed crack position and shape. Moreover, an advanced fatigue life prediction using the Two‐Stage‐Model is applied to the tested girders. The Two‐Stage‐Model applies the Strain‐Life and the Crack Propagation Approach to assess the total fatigue life. Thereby, the number of cycles as well as the crack shape show a good agreement with the experimental results and proves the applicability of the Two‐Stage Model for an advanced fatigue assessment.

Experimental validation of DFOS monitoring system for a bridge girder made of wind turbine blade

AbstractThe relatively new fibre optic measurement technique: distributed fibre optic sensing (DFOS) is provided to control strains and displacements, used in the structural health monitoring of a decommissioned wind turbine blade (WTB) bridge girder. The DFOS system is characterized by the following features: accurate, reliable and continuous strain measurements, possibility of assessing shape and displacements, detection of local damages, high durability. Exemplary results of DFOS measurements performed under laboratory conditions on the full‐scale WTB bridge girder are presented. The paper describes the concept of the WTB bridge girder with integrated DFOS monitoring system to control the girder's behavior under loading. Exemplary data of DFOS efficiency were presented and the overall accuracy and reliability of the DFOS measurement system were revealed.

Strength and Behavior of Glass Fiber-Reinforced Polymer-Reinforced Concrete Box Girders without Web Reinforcement under Pure Torsion

Strength and Behavior of Glass Fiber-Reinforced Polymer-Reinforced Concrete Box Girders without Web Reinforcement under Pure Torsion

A Case Study Based Analysis for the Behaviour and Optimum Design of Steel Concrete Composite Bridge Girders

A Case Study Based Analysis for the Behaviour and Optimum Design of Steel Concrete Composite Bridge Girders

Numerical Modeling of Steel‐Concrete Composite Girders Exposed to Web Shear Buckling

AbstractAssessment of the structural behaviour of steel and steel‐concrete composite plate girders exposed to web shear buckling is essential when it comes to their implementation involving heavy loads and/or long spans. In this paper, numerical model of a benchmark steel‐concrete composite girder capable of capturing this phenomenon has been developed using the ABAQUS software. The developed finite element model, based on a series of large‐scale girders planned to be tested in the future, has been evaluated and elaborated on. That includes the implementation of appropriate analysis procedures, element types and contact behaviour in the study of the post‐critical buckling behaviour of steel and steel‐concrete composite plate girders. The advantages and disadvantages as well as recommendations for the future use of the investigated modelling strategies have been scrutinized. In the end, this study demonstrates the parameters with the most significant influence on the structural behaviour of composite girders exposed to shear loading.

Investigation of the shear behavior of ultra-high performance concrete girder by simulation approach

The present study investigates the shear behavior of the Ultra High Performance Concrete girder strengthened by steel bars and stirrups by simulation approach. Utilizing the Concrete Damage Plasticity model that involves strength reduction and nonlinear behavior of the material, 3D simulation models are established and analyzed by the commercial software Abaqus. The numerical simulation model is verified by comparing the test data to ensure reliability. Numerical simulation models were then developed to investigate the relationship of shear force with parametric studies of shear span to depth ratio, steel bar ratio and stirrups spacing. Based on the obtained results, the simulation model and test results show a good agreement. The relation between the shear capacity of UHPC girder and parametric studies was also enlightened.

Analytical study on flexural behavior of steel composite girder using truss element for shear connectors with different types and layouts

The key to improve the accuracy of behavior analysis of the steel composite girder lies in the reasonable modelling the intergration between the reinforced concrete slab and the steel girder. Based on design requirements and construction methods, the type and layout of the shear connectors between the concrete slab and the steel girder are different, significantly affecting the behavior of the composite girder. This study is conducted to (i) investigate the applicability of a truss element available in the popular simulation software Abaqus in modelling the shear connectors of composite girders, (ii) compare the flexural behavior of composite girders with different types and layouts of shear connectors. Two types of shear connectors considered in the study are headed studs and perfobond strips, and their layout corresponds to the construction methods using the cast-in-place and precast concrete slabs. The study results show that a truss element can be used to simulate the shear connector behavior through reasonable assignment of its shear force-slip relationship. With the design principle that the total shear capacity of the shear connector per unit length remains constant, the nonlinear behavior of the composite girder is significantly affected by the type and layout of the shear connectors.

Transfer Length and Prestress Losses of a Prestressed Concrete Box Girder with 18 mm Straight Strands

Despite the potential advantages of 18 mm strands, the limited research on the behavior of girders with larger-diameter strands hinders the application in bridges. Transfer length and prestress losses are two important indicators. In this research, a 32.6 m long prestressed concrete box girder with 18 mm straight strands and 15 mm harped strands was produced, and the transfer length and the prestress losses were studied. The transfer length was calculated based on the existing equations in codes and previous research. Three beam specimens were fabricated, and strain gauges were pasted on the concrete surface to measure the transfer length of 18 mm strands. It indicated that the average measured transfer length was 700 mm. This value was smaller than the transfer lengths predicted by AASHTO LRFD 2017 and ACI 318-19, while Mitchell’s equation offered the closest prediction to the average measured transfer length. Additionally, the prestress losses at different stages were evaluated. A one-end stressing test was conducted to analyze the effect of strand harping on the loss of tensile force. In comparison with the actual measured loss based on the concrete strain and the longitudinal shortening, the instantaneous prestress loss calculated using the AASTHO LRFD 2017 alternative equation was appropriate. The time-dependent prestress losses due to shrinkage, creep, and relaxation were predicted using two different methods addressed in AASHTO LRFD 2017. The time-dependent predicted losses of 69.2 MPa at 28 d using the refined method were 37% higher than the measured losses 47.4 MPa at 28 d, indicating an overestimation of AASHTO LRFD 2017. The accumulation of the total losses over time revealed that the prestress losses developed in the first two months occupied the majority of the total losses in the long term. The research may provide guidelines for the design of a pretensioned concrete box girder with 18 mm strands.

Experimental behaviour of plate girders in steel – Internal forces in intermediate transverse stiffeners

Economical design of steel plate girders usually adopts slender web panels sometimes combined with large panel aspect ratio, which determines the elastic stability of the web panel. The adoption of transverse stiffeners is one efficient strategy to retard the web buckling due to shear. The primary role of intermediate transverse stiffener is clear: divide the web into panels providing lateral support to the web plate along the span – This increases the shear strength of the web. However, FprEN 1993-1-5: 2022 [1] stiffener design approach is based mainly on direct compressive forces resulting from the tension filed action in post buckling phase. According to multiple investigations, this area requirement is much higher than that found in laboratory testing and numerical simulations. The findings of experimental testing on eight plate girders with thin webs and two configurations of transverse stiffeners under ultimate load are presented. Using the web and stiffener measure strains, the internal stiffener forces are calculated past the shear failure of the plate girders. These results show that the axial compression and bending moment measured in the intermediate transverse stiffeners are considerably lower than those specified for the design by the FprEN 1993-1-5: 2022 [1].

Theoretical calculation of bending capacity of a steel beam - ultra high performance concrete slab composite girder

The composite girder, which combines a steel beam with an ultra-high-performance concrete (UHPC) slab, has gained significant attention in recent years as a new type of bridge structure. However, accurately estimating the bending capacity of such girders remains a challenge, as practical methods are limited. In this article, the authors propose a theoretical approach based on the Euler-Bernoulli beam theory to determine the bending capacity of composite girders. This approach considers the assumptions of plane sections remaining plane and infinitesimal strains during bending. By applying this theoretical approach, the authors derive a formula that allows engineers to calculate the bending capacity of the composite girder. The formula takes into account the dimensions and properties of both the steel beam and the UHPC slab. The derived formula serves as a valuable tool for evaluating the structural behavior and performance of composite girders. To validate its accuracy, the authors compare the results obtained from their calculations with numerical simulations of composite girder failures caused by bending. The close agreement between the theoretical calculations and the numerical simulation results confirms the reliability and applicability of the proposed formula. This research significantly contributes to the field of composite girder design by providing a practical and reliable method for estimating the bending capacity of steel beam-UHPC slab composite girders. The proposed theoretical approach, validated through numerical simulations, offers valuable insights for the design and optimization of these composite girders in various engineering applications.

Calculation Method for Flexural Bearing Capacity of Composite Girders with CFST Truss Chords

To study the flexural behavior of composite girders with concrete-filled steel tubular (CFST) truss chords under positive and negative bending moments, model tests, and theoretical analysis were carried out to investigate the evolution of their flexural behavior and the flexural bearing capacity. The results showed that the web members and joints of composite girders with CFST truss chords subjected to positive and negative bending moments had high strength and rigidity, which ensured that joint failures did not occur before the failure of the entire cross section. The longitudinal strains along the member axis changed linearly along the cross-sectional height, which confirmed the correctness of the plane-section assumption. The failure mode was due to the yield of the steel tube used in the chord and the rebars in the concrete slab under positive and negative bending moments, respectively. The contributions of the web members to the flexural bearing capacity under positive and negative bending moments were 12.5% and 8.6%, respectively. Calculation methods considering the contributions of the web members to the flexural bearing capacity under positive and negative bending moments were proposed. The deviation between the results of the proposed calculation methods and the test and the results of the finite-element parametric studies was less than 8.1%.