Hybrid Girder Research Articles

Structural performance of a hybrid FRP composite – lightweight concrete bridge girder

A novel hybrid fibre-reinforced polymer (FRP) composite – lightweight concrete (LWC) girder was developed and implemented in a bridge superstructure as a result of the comprehensive R&D project. The new bridge system is intended to have durable, structurally sound, lightweight, and cost effective hybrid FRP/LWC girders that will take full advantage of inherent and complementary properties of composites and lightweight concrete. The proposed hybrid girder consists of a FRP shell with trapezoidal cross-section and a lightweight concrete slab, reinforced with glass fibre-reinforced polymer (GFRP) rebars and acting compositely with the shell. Before implementation, a test specimen fabricated as a full-scale model of prototype bridge girder was subjected to a series of quasi-static and fatigue loading tests. This paper presents the selected results of research on evaluation of stiffness, strength, ultimate capacity, and global factors of safety against failure. The test results were compared to the performance criteria formulated in the relevant bridge standards. The output of research confirmed that the proposed hybrid bridge girder has an excellent performance from the structural engineering point of view, and fulfils the appropriate standard conditions to be implemented in an actual bridge. Moreover, due to quite high safety factors it seems to be possible to optimize the hybrid girder design by reducing the amount of FRP material required.

Analysis on steel-concrete joint section of hybrid girder cable-stayed bridge

Hybrid girder cable-stayed bridge has some advantages, such as structure mechanism performance and the low cost. In China, more and more cable-stayed bridge with hybrid girder appeared. The steel–concrete joint part is one of the key structures of large span cable-stayed bridge with hybrid girder, the static bearing capacity and fatigue performance of steel–concrete joint part structure is directly related to security and durability of the bridge. Through the finite element simulation calculation, the stress distribution is calculated, and the stress distribution of the steel structure top plate, steel structure baseplate, concrete top plate and concrete baseplate is analysed emphatically. Verify the bearing capacity and safety of the structural design of joint section.

Investigating Flexural Behaviour of Prestressed Concrete Girders Cast by Fibre‐Reinforced Concrete

The main objective of this research was to investigate the effect of adding polypropylene and steel fibres on flexural behaviour of prestressed concrete girders. Although the construction industry is frequently using prestressed concrete to increase the load‐carrying capacity of structures, it can be further enhanced by using fibres. In this paper, experimental work was carried out to encourage the construction industry in utilizing fibres in prestressed concrete members to improve the mechanical properties of these members. As past investigations on fibre‐reinforced prestressed beams were limited, the present work was done on small‐scale fibre‐reinforced I‐shaped prestressed concrete girders. Six small‐scale prestressed concrete girders were cast comprising a control girder, a hybrid girder, two girders with varying percentages of steel fibres, and two girders with varying percentages of polypropylene fibres. These girders were tested by centre point loading up to failure. It was concluded that, by the addition of small volume fraction of fibres, not only the ductility but also the tensile strength and flexural strength of FRC girders could be improved. It also altered the failure pattern positively by enhancing large strains in concrete and steel. Steel fibre‐reinforced concrete showed higher energy absorption and deflection at ultimate loads in comparison to other specimens.

Experimental evaluation of shear connectors using reactive powder concrete under natural curing condition

In hybrid girder bridges, an efficient type of steel-concrete joint, the so called concrete filled steel cells (CFSCs), can be used to transfer forces between the steel and concrete girders. In the CFSCs, where shear connectors embedded in the concrete core, the bearing capacity of shear connectors is significantly affected by the side confinement effects of steel cells. Shrinkage of concrete may change the interfacial restraints from the steel cells. So far, the influence of concrete shrinkage on the behavior of shear connectors in CFSCs has not been deeply addressed. This paper presents an experimental study of the structural response of shear connectors using reactive powder concrete (RPC) encased in CFSCs. To determine the shrinkage effects of RPC, results from two series of experimental programs are discussed: the first series included testing of twelve plug-in type push-out specimens to assess the performance of perfobond strip (PBL) connectors. The second series consists of testing two plug-in type push-out specimens and eight CFSC type push-out specimens to evaluate the behavior of PBL and steel stud connectors. Results indicated that initial cracks due to shrinkage were observed at the steel cell/RPC interface, which was very detrimental to connectors’ stiffness and strengths. Comparing to connectors with exposed RPC, the average ultimate bond strength at the CFSC steel cell/RPC interface dropped by 15%. Results also indicated that failure of steel stud and transverse steel rebar was barely influenced by RPC shrinkage. Furthermore, a comparison between experimental and predicting results was conducted to assess the applicability of the existing analytical models in predicting the behavior of PBL embedded in RPC with shrinkage.

Behavioral characteristics of hybrid girders according to type of steel–concrete connection

The design of the reinforcement in the transition zone of hybrid girders (i.e., girders composed of concrete girders and steel girders) in terms of the resistance to the transferred load is critical to ensure the integrity of the structure. Although the availability of various types of reinforcement in the transition zone, existing design guidelines are insufficient with regard to the various reinforcing methodologies. To address this shortcoming, this paper focuses on the behavioral characteristics of hybrid girders with respect to prestressing and three types of connections. Flexural tests were conducted using nine hybrid girder specimens that were designed and fabricated using different combinations of shear studs, anchors, lap joints, and prestressing techniques to achieve the steel-to-concrete connection. A numerical model also is proposed to predict the nonlinear flexural behavior of hybrid girders based on the test results and conventional strain compatibility. The results are used to evaluate the contribution of each component of the connection and derive the combination that best provides resistance for hybrid girders.

Experimental Study on the Steel-Concrete Composite Girder Joint of a Single Pylon Cable-Stayed Bridge

Hybrid girder cable-stayed bridges have been widely used around the world due to its advantages including the large-span viability of the main span with steel girder and the counterweight effect of the side span with concrete girder. The steel-concrete composite joint in hybrid girder cable-stayed bridges plays an important role in connecting the steel girder with the concrete girder and transferring the internal forces between two segments of different materials. Therefore, the performance and reliability of the composite joint is of great importance to such bridges. In order to examine the performance of the steel-concrete composite joint of a hybrid girder cable-stayed bridge with single pylon, a 1/4 scaled joint model was fabricated in the laboratory and static test was conducted. The stress distribution and the relative slip between concrete and steel under the combined action of axial force and bending moment were investigated. The test results showed that the maximum stresses of the steel and concrete components are within the allowable limits and the internal forces can be transferred smoothly between the steel girder and the concrete girder via the composite joint. The findings from this study provide useful reference and guidance for the design and testing of steel-concrete composite joints in hybrid girder cable-stayed bridges.

Structural Performance of a Hybrid Girder Cable-Stayed Bridge during Rotation Construction

The structure of hybrid girder cable-stayed bridges with single pylon and single cable plane is very complex, which leads to their complicated structural behavior and adds difficulties to their construction. Few studies have been conducted to investigate the structural performance of such bridges under rotation construction. In the present study, the structural performance of a hybrid girder cable-stayed bridge with single pylon and single cable plane during rotation construction is simulated with the Midas/Civil program. The deflection and the stress of the bridge girder and the deformation of the pylon at different construction stages during the rotation construction are investigated and are checked against the bridge design code. The camber for the bridge girder is also studied. The findings from this study provide useful reference for the design of such bridges for rotation construction and the control of the bridges during rotation construction.

Experimental Investigation on Flexural Response of Hybrid Steel Plate Girder

Flexural tests were conducted on five full scale I-shaped steel beams, three hybrid and two homogeneous, with two aims: 1) validate the inelastic flexural behavior of hybrid girder that is manufactured using lower grade steel 2) simplify finite element (FE) analysis procedure, for further parametric studies, by neglecting residual stresses when symmetrical welding sequence is adopted. Effect of material properties and member slenderness on flexural strength, ductility, and failure mode shapes is discussed. It is also found that failure mode shape and expansion of plastic field are mainly influenced by slenderness of member. Load-deflection and moment rotation response in tests are closely matching with non-linear finite element study. Close match is also observed in failure mode shapes and plastic field expansion. Considerable reduction is observed in residual stresses in symmetrically welded sections as compared to sections welded without proper sequence. This validates non-linear FE analysis procedure by neglecting residual stresses. Test results are compared with prediction equations for flexural strength, rotation capacity available in literature. Test results are also compared with provisions in EN 1993-1-1 and IS 800. Moment gradient (3-P) and uniform moment (4-P) loading have been considered to ensure that results are equally applicable in both cases.

Dynamic behaviour of a GFRP-steel hybrid pedestrian bridge in serviceability conditions. Part 2: Numerical and analytical study

The Part 2 of this two-part paper reports numerical and analytical studies concerning the serviceability dynamic behaviour under dynamic human loads of a typical GFRP-steel hybrid girder system for pedestrian bridges. These studies, which focused on the recent St. Mateus footbridge (Portugal), had two main objectives: (i) to assess the ability of conventional numerical models and analytical formulae to simulate the vibration behaviour of GFRP-steel hybrid footbridges; and (ii) to complement the observations and measurements made in the experimental campaign (Part 1), thus providing in-depth understanding of the vibration performance of this type of footbridges. First, a finite element (FE) model was developed and calibrated with the static and modal experimental data. Then, the FE-model was used to evaluate the vibration response of the footbridge for the same pedestrian activities induced in situ. The design formulae available in the literature for predicting the maximum acceleration of structural systems are also reviewed and were applied to evaluate the resonant response of the footbridge for both single and crowded conditions of pedestrian traffic. The results obtained confirmed the adequate structural behaviour of the St. Mateus footbridge under real dynamic (human) pedestrian load cases and show that this innovative GFRP-steel hybrid structural solution is suitable for pedestrian bridges. The results of the different investigations reported in this paper also showed that both numerical and analytical approaches are able to predict the vibration response of GFRP-steel hybrid footbridges with reasonable accuracy.

Experimental investigation of the M-V-F interaction behavior of girders with trapezoidally corrugated web

Steel corrugated webs are likely used in the field of bridges in the last few decades due to their numerous advantages. The most favorable layout is the hybrid girder with upper and lower reinforced concrete slabs and with steel corrugated webs. During incremental launching – without concrete flanges – the steel girder can be subjected by the combination of bending (M), shear (V) and transverse forces (F) which result in a complex stress field and a coupled instability phenomenon may occur. In the international literature there are just a limited number of previous investigations focusing on the M-V-F interaction behavior of girders with corrugated webs. The authors previously developed a proposal for the consideration of the M-V-F interaction behavior of trapezoidally corrugated web girders based on FE simulations, which interaction equation was verified only based on test results found in the international literature. Those test results were mainly related to the investigation of pure bending moment, shear buckling and patch loading capacities and laboratory tests were missing to investigate the M-V-F interaction behavior and to determine the load carrying capacities under coupled instabilities. In the current research the authors designed and executed a complex experimental research program focusing on the M-V-F interaction behavior of girders with trapezoidally corrugated web. The current paper introduces the executed experimental research program, presents the results of the laboratory tests and gives final conclusions to the M-V-F interaction behavior based on test results and numerical simulations.

Structural Performance and Strength Prediction of Steel-to-Concrete Box Girder Deck Transition Zone of Hybrid Steel-Concrete Cable-Stayed Bridges

AbstractBecause a large longitudinal force exists in hybrid girder cable-stayed bridges due to the cable tension, its transfer mechanisms on the steel-concrete combination segment would be an important issue. In this study, experiments and theoretical analysis were conducted to characterize the longitudinal force transfer mechanisms of the steel-concrete combination segment in hybrid girder cable-stayed bridges. Five full-scale local structure specimens were designed and manufactured based on the original design of the steel-to-concrete transition zone according to a completed cable-stayed bridge in China. The specimens were subjected to monotonic loading and tested up to complete failure. The load-slip curves; stress distribution and failure modes, which varied with the thickness of the bearing plate; and the shear connector distribution were obtained. To simulate the test properly, calculation methods for predicting the shear connector capacity and corresponding load-slip curves were proposed based on t...

Design and research on the first polish FRP composite road bridge

Abstract The main goal of the research project was to develop and demonstrate the first Polish FRP composite road bridge, starting from concept design and material research, and going thru manufacturing technique selection, detailed FEM analysis and structural testing of elements. The R&D project comprises also the proof test of the completed bridge as well as structural monitoring in exploitation period. The objective of the paper is the description of the bridge and its structural solutions, i.e. FRP box girders and lightweight concrete deck slab acting compositely. Further the FEM analysis of the girder and the bridge span made on design stage has been presented. The VARTM manufacturing technique was used for girders production. Its main steps have been also presented. Finally the research on the new FRP box girder with LRC slab (hybrid girder) has been briefly showed. The full scale prototype girder with the total length of 22 m was tested to evaluate its carrying capacity, modes of failure, basic dynamic parameters as well as overall behaviour under ultimate static load. The FRP girder met the prescribed serviceability and safety criteria. The FEM model of the girder was validated against testing results and was further used for bridge design. Thanks to R&D project the first Polish FRP bridge is likely to be built late autumn 2015. The output of the research project gives a very promising future for the FRP composite bridge application. The research works showed in the paper have been partially financed by the Polish National Centre for Research and Development in the frame of the research project “ComBridge” (www.com-bridge.pl).

Dynamic analysis of a large span specially shaped hybrid girder bridge with concrete-filled steel tube arches

In the present study, the dynamic property of a specially shaped hybrid girder bridge with concrete-filled steel tube (CSFT) arches is investigated based on experimental and numerical methods, especially under moving vehicles. Before the inauguration of this bridge, a dynamic field test was conducted. A refined three-dimensional finite element model is built to represent the complex structural mechanic property of the bridge. The vehicle-bridge coupled vibration (VBCV) model with a 16 DOF vehicle model is established to simulate the dynamic behavior of the bridge with moving vehicles. The FE model is updated, and the VBCV model for the bridge is verified, taking advantage of the aforementioned measured data. The result indicates that the proposed VBCV numerical model can closely reproduce the measured response and can be used to simulate the dynamic behavior of the bridge under various conditions. The impact effect, ride and pedestrian comfort, and related parameters analysis for the bridge with moving vehicles are studied by numerical simulations and experimental tests. The results indicate that the impact factor formula from design standards significantly underestimates the dynamic impact effect, which may result in an unfavorable influence on the bridge safety. Several conclusions are drawn for this bridge, and further research that is needed for this new bridge type is discussed.

Analysis of auxiliary ribs in steel–concrete joint of hybrid girder

The auxiliary ribs are utilized to reinforce the steel–concrete joints (SCJs) of hybrid girders. However, the demands of the ribs and the design of orthotropic steel decks with the auxiliary ribs are not addressed in design specifications. Solid element models are used to study the auxiliary ribs of the SCJ. The joints with and without auxiliary ribs are analyzed to clarify the demands and the reinforcing effects of the ribs. Stress dispersal efficiency of three typical auxiliary ribs is investigated. The trough–auxiliary rib (TA) joint is analyzed to check the steel deck design assumption and the approach to suppress stress concentration is discussed. The effective length of the auxiliary ribs is studied considering the geometric variations. Results show that the auxiliary ribs enlarge the steel deck and narrow the steel–concrete centroid deviation. The auxiliary ribs disperse about 50% axial force and the stress transmission of the joint is improved. The T-rib inserted in the trough is efficient to reinforce the SCJ with the effective length of 2–4 times the concrete slab thickness. The TA joint with abrupt tip suffers stress concentration and the safety margin of the steel deck is reduced. The joint is improved with about 60% hot spot stress decrease using the gentle tip with crossbeam constraint.

Connection between Concrete Layers with Different Strengths

As part of a research intending to develop steel-concrete hybrid girder using ultra high performance concrete with compressive strength of 80 MPa, this study conducts loading test on this girder to investigate the methods for its composition with a slab using 30 MPa-concrete and the corresponding interfacial behavior. Prior to the loading test, the design formula of the Eurocode for the shear resistance developed in concrete-to-concrete interface is examined for the interface between concrete layers of different strengths. The effect of the surface roughness on the shear resistance is examined using this formula and finite element analysis to verify the applicability of the formula. Based upon the results, loading test is conducted on girder specimens to evaluate the actual behavior with respect to the interfacial surface condition. The test results reveal that the specimen with rough interface could not develop perfectly composite behavior and experienced adhesive failure. In case of simultaneous action of flexure and shear, it appears that conservative design should be applied without consideration of the interfacial condition when determining the arrangement of shear reinforcement.

The Numerical Simulation Analysis Method of Steel-Concrete Joint Section in Hybrid Girder of Cable-Stayed Bridge

The steel-concrete joint section is a critical structure of load transmission in cable-stayed bridge girder. Under the requirement of calculation efficiency, correct numerical simulation is an important method to acquire the inter stress and deflection on the joint section of cable-stayed bridge girder. Taken the steel-concrete joint section finite element analysis of a cable-stayed bridge as an engineering background, the whole process simulation method of cable-stayed bridge steel-concrete joint section is introduced, which considering the nonlinear bond slippage effect and ANSYS program is employed. The effect on mechanical behavior and damage pattern of structures is also compared among different stud constitutive relation. The calculation results show that the numerical results of nonlinear stud joint section FE model are in a good agreement with the model experiment testing data. The equivalent stress of bearing plate from the simulation is relatively high under the ultimate load, and, the crack distribute at the whole concrete section. The calculation results of linear stud FE joint section model are close to the results of nonlinear stud joint section FE model under the design load. Under the ultimate load, the choice of different stud shear stiff model has effect on the concrete at crack initial moment. While after the most concrete crack, there is little difference on the crack distribution between the nonlinear and linear stud joint section FE model.

Influence of Error of Unstressed Cable Length on Mechanical Behavior of Thousand-Meter-Scale Hybrid Girder Cable-Stayed Bridge

AbstractTaking Edong Yangtze River Bridge as the research subject, the influence of error of unstressed cable length on the geometric shape and internal force of super-span hybrid girder cable-stayed bridge during completion is studied on the basis of the geometry control method with full consideration of the structural nonlinear geometrical effect. Moreover, the mechanical behaviors of the center and side spans of the bridge and their control strategies are discussed. The analysis shows that structural differences between the center and side spans exerted an influence on the geometric shape and internal force. The influence of unstressed cable length error on the geometric shape in the center span of the completed bridge is greater than that of the side span, whereas the impact on internal force in the side span is greater than that in the center span. The mechanical behavior is relatively independent between span types. In addition, the percentage change of the girder stress reaches the maximum level in...

Research on the Equivalence and the Mechanical Performance of the Model of Steel-Concrete Joint

The hybrid girder cable-stayed bridge of railway has been applied in the design of the Yongjiang Bridge, it is first used in our country as yet. The mechanical performance of the steel-concrete joint as the key position of the hybrid girder cable-stayed bridge determine its safety and durability. Based on the background of a bridge in Zhejiang Province , the spatial finite-element model of model and actual bridge is developed to study the mechanical performance and verify the feasibility of design method of the model. As it turned out, the model can better reflect the stress of actual bridge. The trend of the stress of the key plates of its is basically identical. The steel-concrete joint can perfectly accomplish the transmission of the stress function. Bearing plate plays a vital role in the stress transfer, the function of the PBL shear connector near the bearing plate is obvious.

Dynamic Characteristics of Hybrid Girder Cable-Stayed Bridge

This paper is made after the dynamic test on Jing hang Channel Bridge in Wujiang, Jiangsu Province. Based on the test on this bridge, we get dynamic characteristics of the bridge span structure. We will analysis the vibration generated from the steel and concrete box girders of the bridge while the car is running on it. Based on the different characteristics of vibration from the two kinds of girders, we can analysis the influence of this hybrid girder on driving comfort.

Experimental and analytical study on stiffened steel segment of hybrid structure

Hybrid structures which innovatively and reasonably combine two different materials in longitudinal direction have been applied world-widely, such as hybrid girder, hybrid pylon and hybrid arch skewback. The hybrid structure segment generally consists of steel stiffened segment, concrete strengthened segment and hybrid joint. In order to investigate ultimate capacity and buckling mode of steel stiffened segment in hybrid structure, model tests on five different specimens have been carried out. The test results indicated that embedded T-reinforcing stiffeners had the best axial stiffness, while the out-plane stiffness, ultimate capacity and local stress concentration of circumscribed π-reinforcing stiffeners were best among the three traditional reinforcing stiffeners. Besides, the methods of extending reinforcing stiffener web and adding diaphragms on the end of reinforcing stiffeners not only obviously improved both axial and out-plane stiffness but also increased ultimate capacity and reduced local stress concentration. Five three-dimensional finite element (FE) models of steel stiffened segments considering initial imperfections and residual stress were established. Theoretical analysis based on the principle of stationary potential energy was carried out. The reduced parameters based on FE analysis results were consistent with those from tests and theoretical analysis and tended to be conservative at a safety level. The presented overall investigation may provide reference for the design and construction of stiffened steel segment in hybrid structure.