Continuous Composite Girder Research Articles

Experimental study of prestressed steel-HFRC composite girders under hogging moment

To alleviate cracks in the hogging region of continuous steel-concrete composite girders, the hybrid fiber reinforced concrete (HFRC) and prestressing technique were introduced to exploit a novel type of composite girders (prestressed steel-HFRC composite girders). Four specimens with different concrete slabs (normal concrete (NC) slab, prestressed NC slab, HFRC slab, prestressed HFRC slab) were tested under hogging moment to investigate their mechanical properties. The test results showed that the prestressed steel-HFRC composite girder could take advantage of the synergy of the prestressing technique and HFRC and, therefore, its ultimate capacity, cracking load and stiffness were the biggest while the crack width was the smallest among the specimens investigated. In addition, practical equations of ultimate/crack moment and crack width were obtained based on the test results. The proposed equations could provide the reference in the design of prestressed continuous steel-HFRC composite girders.

Shear Performance Study of Sleeved Stud Connectors in Continuous Composite Girder.

In order to reveal the mechanism of sleeved stud connectors, 15 push-out specimens were designed, and static loading tests were conducted to evaluate the mechanical performance. The shear performance differences between the novel sleeved studs and conventional welded studs were compared. Referring to the experimental results, an Abaqus nonlinear finite element model was established to study the shear mechanism of sleeved stud connectors. Parametric analysis was conducted to investigate the effects of stud height, sleeve filling material, and sleeve diameter on the mechanical performance of the connectors. The experimental and finite element analysis results indicated that the ultimate shear bearing capacity and shear stiffness of the sleeved stud connectors were higher than those of ordinary welded studs, and the maximum slip was relatively small. Compared to conventional welded studs, the ultimate bearing capacity of sleeved studs increased by 4% to 8%, and the shear stiffness increased by 25% to 35%. Since the shear behavior of sleeved studs mainly occurred at the base of the studs, the influence of stud height on shear performance was relatively small. However, sleeve and stud diameter have a great influence on bearing capacity and stiffness. As the Ultra-High Performance Concrete (UHPC) near the base of the stud effectively enhanced the shear carrying capacity of the sleeved stud connectors, the shear carrying capacity and shear stiffness increased with the increase in the sleeve diameter.

Flexural performance of precast segmental continuous box girders with corrugated steel webs

Due to the existence of joints, the flexural performance of segmental assembled girders is different from that of monolithic cast girders. In order to study the flexural performance of precast segmental assembled box girder with corrugated steel webs, a static failure test on a precast segmental assembled continuous box girder with corrugated steel webs and variable cross-section and a monolithic cast continuous box girder with corrugated steel webs of the same size was carried out. The influence of the existence of joints on the deflection, strain, and prestress increment of precast segmental continuous girder with corrugated steel webs was analyzed. The parameter analysis was further carried out by the finite element method. The results showed that, at the initial loading stage, the joint had little effect on the displacement, and the deflection of the segmental assembled girder changed more rapidly than that of the monolithic cast girder. In the monolithic girder, cracks mainly occurred at the middle-support position of the middle span and pure bending sections. In the segmental beam, cracks were concentrated in the concrete on both sides of the joint. The number of cracks was relatively small and concentrated in the concrete on both sides of the joints of the loading segment and the middle support segment. The trends in the strain growth in the segmental beam and MB01 were consistent, and the values were similar. The strain growth trend of the segmental girder and the monolithic girder was consistent, and the values were similar at the initial loading stage. The external prestressed tendons in the segmental girder had a greater role in the loading process than those in the monolithic girder, and the normal stress in the segmental girder increased more rapidly during the bending process. In the ultimate loading state, the external prestressing force of the segmental girder was 2.01% higher than that of the monolithic girder. The number of segments was inversely proportional to the flexural capacity of the structure. Excessive thickness of the adhesive layer would adversely affect the crack resistance of the structure. This study will contribute to the engineering application of continuous composite box girders with corrugated steel webs.

Cracking performance in the hogging moment region of HSS-UHPC continuous composite girder bridges

To elucidate the cracking performance of concrete slabs at the negative bending moment region of high strength steel (HSS)-ultra high performance concrete (UHPC) continuous composite girder bridges, eight scale-reduced steel-concrete composite beams, constructed using HSS and UHPC that varying parameters of UHPC slab thickness and width and shear connection degree at the steel-concrete interface were prepared and tested. The composite beams' cracking pattern, bending stiffness, load-deflection curve, steel-concrete interfacial slippage, and strain history were presented and discussed. The test results show that the HSS-UHPC composite beams subjected to negative bending moments exhibited favorable cracking performance. With the UHPC slab width increasing from 450 mm to 550 mm, the composite beams' initial cracking moment, bending stiffness, and flexural ductility increased by 33.4%, 20.5%, and 39.8%, respectively. The utilization of a thick UHPC slab benefited the performance of the composite beams under negative bending moments. Replacing the 80 mm-thick slab with a 110 mm-thick slab improved the structure’s cracking moment and bending stiffness by 15.0% and 21.4%, respectively. Additionally, as the shear connection degree increases from 0.64 to 1.02, the initial cracking and ultimate failure moments of the composite beam were improved by 7.2% and 1.6%, respectively. In contrast, the bending stiffness of the beams with a shear connection degree of 1.02 was 12.4% smaller than those of 0.64. A comprehensive comparison between the formula-predicted cracking performance and current experimental results was performed to examine the capability of existing design approaches in calculating the HSS-UHPC composite beams. The flexural resistance algorithm proffered by Xu exhibits favorable alignment with test results, thereby providing a compelling methodology for designing HSS-UHPC continuous composite girder bridges.

Vehicle–Bridge Interaction Dynamic Analysis of Continuous Rigid Frame Composite Box Girder Bridge with Corrugated Steel Webs under Seismic Excitation

To study the vehicle–bridge interaction (VBI) of highway bridges under seismic excitation, a vehicle–bridge couple analysis method based on Ansys is proposed. The 1/2 vehicle model and space beam element model were established to analyze the VBI response of Lanzhou Xiaoshagou bridge. The self-excited excitation of the system is represented by road surface irregularity randomness, while the external excitation is represented by an earthquake. The impact of seismic types, seismic direction, seismic intensity, vehicle speed, and road surface irregularity on the bridge vibration under the vehicle–bridge coupling during an earthquake is thoroughly analyzed. The results reveal that the type of earthquake significantly influences the dynamic response of the bridge, showing a minimum difference of 31.4%. The intensity of the earthquake is positively correlated with the dynamic response of the bridge. Longitudinal and vertical earthquakes have a more noticeable effect on the bridge’s vertical vibration compared to lateral earthquakes. The ratio of the bridge response under vertical or longitudinal seismic excitation to the response of lateral earthquakes ranges from 1.50 to 26.61. Vehicle speed, road irregularity grade, and randomness have a negligible impact on the dynamic response of vehicle–bridge interaction under an earthquake, accounting for less than 3%. These findings indicate that the analysis of earthquake-bridge vibration can simplify the VBI analysis for continuous rigid frame composite box girder bridges with corrugated steel webs under seismic conditions.

Cracking control technique for continuous steel-concrete composite girders under negative bending moment

Cracking control technique for continuous steel-concrete composite girders under negative bending moment

Multi-span composite girders with composite dowels – Experimental investigations and design approach to account for the beneficial effect of shear force redistribution along the composite interface

The broad use of composite dowels as shear connectors in multi-span steel and concrete composite members is currently hindered by insufficient regulations for hogging moment regions, where the connectors are located in cracked concrete slabs and have reduced shear resistance. This paper reports on the results of three beam tests that illustrate the ability of continuous steel and concrete composite beams with composite dowels to redistribute shear forces from impaired connectors located in hogging bending regions to intact connectors in sagging bending regions. The effect of concrete cracking on the load-bearing behaviour of composite dowels is analysed with regard to their strength, stiffness and ductility by means of three full-scale member tests. This paper proofs the existence of a beneficial shear force redistribution process along the interface of multi-span composite members and quantifies the shear force transfer occurring between connectors in sagging and hogging bending regions. In addition, the paper provides an economical design method for continuous composite girders. Previously developed models regarding the shear resistance of single composite dowels in cracked concrete are refined aiming to provide both safety and ease of use. These models are subsequently extended into a comprehensive design strategy that allows us to consider the beneficial shear force redistribution processes along the interface when designing the shear connection of multi-span composite beams with composite dowels.

Experimental and Numerical Study on the Mechanical Behavior of Prestressed Continuous Composite I-Girder Bridges with Partial Connection

A partial connection–prestressing (PCP) method is proposed in this paper to decrease the prestress that was transferred to steel girders in the negative moment region of steel–concrete composite bridges. The partial connection is achieved by the application of rubber-sleeved studs (RSS) in the prestressed concrete slab in the negative moment region. Since there is no experimental research on the PCP method in continuous composite girders, to the best of the authors’ knowledge, two continuous composite girders were tested under a four-point static load to evaluate their mechanical performance. The test results showed that without decreasing the ultimate strength and overall stiffness of the steel–concrete composite girders, the PCP method enhanced the cracking load (Pcr) 3.1 times. In addition, 12.5% of the prestressing force was transferred into the steel girder at the internal support section with the PCP method, and the girder without the PCP reached 25.9%. Then, to elucidate the partial interaction effect and prestressing effect on continuous girders’ mechanical behavior, numerical models were developed and calibrated with the test results. From the numerical analysis, compared with normal composite girders, the application of RSS or prestressing could improve Pcr by 11.8% and 157.0%, respectively, and the value increases to 234.3% when RSS and prestressing are applied at the same time. The results indicate that the application of RSS in the negative moment region could effectively increase the prestressing efficiency in the concrete slab and enhance the bridge's durability.

The bearing capacity parameter analysis and heat energy storage loss test of concrete composite box girder

In order to study the relationship between the bearing capacity of the structure and the damage degree, the author proposed the bearing capacity parameter analysis and the heat storage loss test of the concrete composite box girder. Taking the five-span prestressed concrete composite box girder as an example, different degrees of damage are simulated by reducing the bending stiffness of different parts, and the modal strain energy method and flexibility difference method are used to diagnose the structural damage. The test results show that for the first span, the sum of the structure can meet the corresponding specification requirements under the condi?tion of dense traffic and less than 20% damage. When the damage is greater than 20%, the first span beam cannot meet the driving requirements. Under general traffic conditions, when the damage is less than 30%, the structure can basically meet the driving requirements, and the second and third spans still have a high safety factor. In the case of 30% damage of the first span, although ? it does not meet the requirements, but RF > 0.9. Each monitoring point has good estimation accuracy, and the error between the maximum temperature occurrence time of each monitoring point and the maximum temperature occurrence time of the mon?itoring point is within ? 10 hours . For continuous composite box girder structure, the flexibility difference method is superior to the modal strain energy method.

Experiment Analysis on Crack Resistance in Negative Moment Zone of Steel–Concrete Composite Continuous Girder Improved by Interfacial Slip

Due to the strong interface effect of continuous steel-concrete composite beams with conventional shear connectors, the efficiency of applying pre-stress in the negative moment zone is greatly reduced, which leads to a difficulty of anti-cracking design in the negative moment zone of pre-stressed steel-concrete composite box girder. In order to study the feasibility and the working mechanism of improving the crack resistance of continuous steel-concrete composite bridges by releasing the interfacial slip effect within the negative bending moment region, two groups of model tests were carried out in the paper. Two steel-concrete composite beams were used for model test, one of them using the conventional stud shear connectors, another one using the new shear connectors, named uplift-restricted and slip-permitted shear connectors. The results show that, compared with the composite beam with conventional shear studs, the composite beams with uplift-restricted and slip-permitted shear connectors have a higher pre-stress application efficiency, and the new connector could release the interface slip, which can make the tensile stress distribution in concrete slab more uniform within the negative moment zone, thus increasing the cracking load of concrete slab and reducing the subsequent crack width effectively. This study is helpful to understand the relationship between the interface slip and the anti-crack characteristics in negative moment zones, and a new anti-crack design method is proposed for the design of continuous composite girder.

Application of Partial Shear Connection in Steel–Concrete Semi-Continuous Composite Girder Bridges

In the hogging moment regions of steel–concrete composite continuous girder bridges, a detrimental condition appears such that concrete slab bears tensile stress and the steel girder bears compressive stress. Decreasing the shear connection in the hogging moment regions helps to improve the mechanical performance for steel–concrete continuous composite girder bridges. In this paper, analytical models for the calculation of composite girders considering partial shear connection (PSC) action are discussed. A project case of Qiwu Bridge in Jiangxi Province using partial shear connection action is introduced. A nonlinear finite element model of Qiwu Bridge is established through ABAQUS® to simulate and predict the mechanical properties and structural performance. Based on the finite element method results, the influence of PSC on various parameters is analysed by performing a parametric analysis. Numerical results show that arranging a partial shear connection region can effectively reduce the crack region and disperse areas having high stress concentration, but shear stiffness mutation can significantly increase the stress level at the edge of the partial shear connection region.

Research on bridge structure SAM based on real-time monitoring

To study the problems of frequent omissions and false alarms in the early warning system due to defects in the safety assessment method (SAM) of the existing bridge health monitoring systems (BHMS). In this paper, the current safety evaluation methods of BHMS are deeply studied through fuzzy comprehensive evaluation method and derive a new type of bridge health monitoring system SAM based on the safety evaluation vector. At the same time, combined with the concept of membership function, the result vector is accurately quantified, and a specific evaluation method for evaluating the safety level of the bridge structure is obtained. Combining the data of the three bridge health detection systems of 3 × 30 m continuous girder bridge, simply supported beam bridge, and steel–concrete composite girder bridge in the Beijing Metro Line 5 project, the daily and monthly safety assessment results of the three BHMS were verified. The research results show that the structural SAM proposed in this paper can accurately and in real-time evaluate the safety status of small and medium-span simply supported bridge structures. However, for the evaluation of continuous girder bridges and composite girder bridges, it is necessary to make specific judgments based on the actual conditions of the bridges. Moreover, the research in this paper can also consolidate the theoretical foundation for establishing the bridge structure monitoring data, early warning model. The research method in this paper can promote the further development of the bridge structural health monitoring system.

Slip analysis of prestressed steel-concrete continuous composite beam

To analyze the horizontal shear resistance participation degree of the shear studs on the web and diaphragm flange in the negative moment area of the steel–concrete continuous composite box girder, the steel–concrete composite girder specimen was designed and manufactured based on the existing codes. The shear deformation of the two parts of the studs in the composite box girder is studied by the finite element parameter analysis of the nonlinear shear deformation of the studs and the stress analysis of the diaphragm. The results show that web flange studs provide the horizontal shear capacity of the steel–concrete composite box girder. The installation of baffle flange studs cannot improve the shear connection degree of composite beams. Removal of the flange stud from the diaphragm can relieve the force on the diaphragm and provide a theoretical basis for reducing the stiffeners of the diaphragm.

Numerical Investigation of Performance of Continuous Composite Girders with UHPC slab at Hogging Moment

This paper intends to investigate the behavior of continuous composite girders with of ultra-high-performance concrete (UHPC) slab at hogging moment zone utilizing the nonlinear finite element (FE) modeling. A nonlinear three-dimensional FE model of the continuous composite girder was developed utilizing the commercial software ABAQUS. The model considers both material and geometric nonlinearities. Behavior of normal concrete (NC) and UHPC was modeled utilizing damage plasticity model. Tied, normal friction behavior, embedded contacts were used to simulate the interfacial zones between contacted elements. Four different models were developed and validated with experimental results. The verified model showed satisfactory behavior and is capable of predicting the loading history for continuous composite girders. The model can capture the modes of failure either in normal concrete slab at sagging moment zone or delaminating of UHPC layer at hogging moment zone. A parametric study was carried out to investigate the effect of length of UHPC slab at hogging moment zone on the behavior of the continuous composite girders. The findings of the parametric study showed that the length of UHPC slab slightly affects the ultimate capacity, yielding load, and stiffness of the composite girders. However, significant enhancement in cracking loads was obtained as increasing the length of UHPC slab.

Stressing state analysis of multi-span continuous steel-concrete composite box girder

This paper uses the theory of structural stressing state to study the working characteristics of three multi-span continuous steel-concrete composite box girder (SCCBG) models with different prestress levels. Firstly, the generalized strain energy density (GSED) is constructed to reveal the working state of the structure based on the experimental strain data, the Mann-Kendall (M-K) criterion is applied to distinguish the leap characteristics load points (P and Q) of the structural stressing state and defined as the “failure load”. It is used to update the existing structural “destruction” load to more clearly reflect the entire structural failure process. Then, the working state parameters of the cross-section are described (strain distribution mode, midspan deflection, crack width, etc.) to analyze the working behavior of the box girder model. Finally, the non-sample point interpolation method (NPI) is used to reasonably expand the experimental strain data, to verify the rationality of the characteristic load points, and the stressing state characteristics of box girders with different prestressed levels are further discussed.

Shear performance and dimension rationalization study on the rubber sleeved stud connector in continuous composite girder

Wrapping rubber sleeve around a stud shank near the root makes a low level of shear connection between the steel girder and concrete slab in a composite girder. It helps to reduce the concrete tensile stress and steel compressive stress in the hogging moment region. However, the specific mechanical effects of the rubber dimension and modulus on the connector performance have not been understood, which hinders the application in practice. To this end, 15 push-out tests on studs wrapped with rubber sleeves were conducted for the investigation. And a push-out parametric analysis with damage plasticity models was executed for dimension rationalization. The test results showed an obviously lower stiffness and larger bending deformation of rubber-sleeved stud as compared with a normal stud, while the strength varied little. The analysis results showed that the efficient rubber thickness and length for a 22 mm-diameter and 220 mm-high stud could be 4 mm and 50 mm in terms of the stiffness reduction extent. It also showed an obvious stiffness reduction occurred when the wrapping material modulus was 10% lower than concrete. Furthermore, the connector stiffness effect on the stress distribution along with a continuous composite girder was analyzed and quantified, showing a 39% reduction of concrete slab stress in the hogging moment region and a 13% increase of steel stress on the top flange.

Fire response of horizontally curved continuous composite bridge girders

This paper presents an approach for investigating fire response of horizontally curved continuous composite bridge girders under localized hydrocarbon fire exposure conditions, considering flexural-torsional-shear coupling effect. A three-dimensional nonlinear finite element model, established using computer program ANSYS and validated through experimental data generated from fire tests, is utilized to analyse the effects, including curvature radius, fire position along bridge span and fire exposed different steel girders, on fire response of a typically horizontally curved three-span continuous composite bridge girder. The predicted results including mid-span deflection, axial displacement and web out-of-plane displacement in different steel girders, are used to quantitatively evaluate fire resistance of horizontally curved continuous composite bridge girders. Findings from analysis results show that curvature radius, fire position along bridge span and fire exposed different steel girders have a significant influence on fire resistance of horizontally curved continuous composite bridge girders. Horizontally curved composite bridge girder with smaller curvature radius presents a lower fire resistance. The outer steel girder governs failure of horizontally continuous composite curved bridge girders subjected to simultaneously hydrocarbon fire and structural loading. Web buckling-based failure criterion is suited to determine failure of horizontally curved continuous composite bridge girders under fire conditions. Therefore, prevention of the outer steel girder from fire can highly improve fire resistance of horizontally curved continuous composite bridge girders.

Static behavior of a steel-ultra high performance concrete continuous composite box girder

To improve the crack-resisting behavior of normal-strength concrete (NC) bridge deck and to reduce the deadweight of conventional steel-concrete composite girders, a new steel-ultrahigh performance concrete (UHPC) continuous composite box girder was proposed. Aiming to reveal the static behavior of the proposed structure, including the load-deflection response, the strain distribution, the crack development, the moment redistribution and the failure mode, a comparative experimental study was conducted on two types of the composite girder, namely a steel-UHPC continuous composite girder (SUCG) and a prestressed steel-concrete continuous composite girder (SCCG). The test results indicated that the ultimate loading capacity of the SUCG was 20.4% higher than that of SCCG; the nominal cracking strength of the SUCG was 22.9 MPa, and its corresponding cracking moment was 2.1 times higher than the conventional one; the crack development mode of UHPC slab were significantly different from the SCCG, the cracks appeared in UHPC slab dominated by microcracks with smaller length were numerous and intensive. It is also shown that the SUCG has smaller degree of moment redistribution. Thus, the current study verified the SUCG could be one of effective solutions for long-span continuous composite girder bridges.

Fire Performance of Continuous Steel-Concrete Composite Bridge Girders

This paper presents a detailed investigation in to fire resistance along with failure mode in continuous steel-concrete composite twin I-shaped bridge girders under different localized fire through considering fire severity and fire exposure positions namely; mid-span zone in one of the two span, hogging moment zone and side-support zone. A 3-D finite element (FE) model, built utilizing the computer program ANSYS, is used to track structural fire performance in a typical two span of continuous composite twin I-shaped bridge girders (fabricated with twin I-shaped plates supporting a concrete slab) dependent on thermomechanical coupled analysis. The model validation is undertook through comparison of temperature and deflection response attained from a scaled composite single I-shaped girder tested exposed to ISO834 fire. The numerical analysis results show that the developed model can be favorably used to analyze the behavior and failure mode of continuous steel-concrete composite twin I-shaped bridge girders during entire range of fire exposure. Fire severity and fire exposure positions present critical influence in to the fire resistance of continuous composite bridge girders. Fire exposure prevention on hogging moment zone can significantly extend failure time of continuous girders, and further hold back progressive structural collapse. Web buckling based failure criterion can be applicable to calculate fire resistance of realistic continuous girders under simultaneous structural loading together with localized fire. Continuous composite bridge girders subjected to localized fire present highly significant local deformation response in the fire exposed bridge girder span.

Temperature Field and Gradient Effect of a Steel‐Concrete Composite Box Girder Bridge

To study the effect of the temperature field and gradient of a steel‐concrete composite box girder bridge, a 5 × 35 continuous composite box girder bridge is used as the research object. The temperature measuring point is set by selecting a typical cross section, and the temperature change data are measured. The temperature field of the different positions in the composite box girder bridge is studied, the global and local temperature differences are compared, and the law of temperature distribution and the main factors affecting the temperature field are formulated. The most unfavourable expression function of the vertical temperature gradient of the section is simulated using the measured data, the existing standard temperature gradient mode is compared, the finite element model of the bridge is established, and the influence of the actual temperature gradient mode on the stress and deformation of the composite girder is further analysed. The conclusions show that the temperature differences of different azimuth sections and the local temperature differences between the steel and concrete joint parts of the steel‐concrete composite box girder bridge are not significant. The temperature gradient heating and cooling model fitted by the measured temperature field can be used as a reference for the structural design of similar local bridges.