Concrete Composite Beams Research Articles

Development of novel shear connectors for cold-formed steel concrete composite beams

The usage of cold-formed steel members as a primary structural element has increased drastically, paving the way for developing cold-formed steel-concrete composite members. The shear connectors are key elements to provide the composite action between steel and concrete. The research on suitable shear connectors for cold-formed steel-concrete composite members has been widely investigated. This study evaluates the behavior of three novel shear connectors. The proposed shear connectors were anchored without welding, making them suitable for light gauge sections by reducing the formation of residual stresses and geometrical imperfections. The first two shear connectors (trapezoidal and hexagonal) were anchored using self-tapping screws. The third one, the prefabricated shear connector, was incorporated by adopting suitable modifications in the beam without external connecting arrangements. The behaviour of connectors was assessed by conducting push-out tests as per Eurocode 4. The shear capacity, characteristic slip, initial stiffness, load-slip relationship, ductility, and energy absorption capacity of the connectors were analysed and presented. It is observed that the prefabricated shear connector has recorded the highest shear capacity and energy absorbing capacity among the proposed connectors.

Flexural and longitudinal shear performance of precast lightweight steel–ultra-high performance concrete composite beam

Flexural and longitudinal shear performance of precast lightweight steel–ultra-high performance concrete composite beam

Analysis of steel–concrete composite beam using Ansys 18.1 Workbench

Composite beams made from more than one material can cover large column-free spaces. Composite construction is faster than cast in-situ concrete as rolled steel and prefabricated components are used. Steel concrete composite beam consists of a steel beam above which a concrete slab with reinforcement is casted using shear connectors. In recent years, steel–concrete composite beams have been employed extensively in structures and on bridges. The concrete act together with steel to create a stiffer, lighter, less expensive structure. The analysis using ANSYS 18.1 Workbench is significant as it provides more accuracy compared to experimental analysis along with being cost efficient and time saving and it uses the principle of finite element analysis. An experimental study was done to study the behavior of composite beam under monotonic load by Bing Wang, Qiao Huang, Xiao ling Liu and Wenxian Li. The study was conducted on eight composite beams with various arrangement of shear connectors to assess their performance under monotonic load and fatigue load. This paper studies the structural behavior of steel concrete composite beam under monotonic load and also compares the experimental results obtained from above mentioned paper with the results obtained for four steel–concrete composite beams analyzed using Ansys 18.1 Workbench. Non-linear static analysis was done on four sets of beams based on the variation in number of studs and stud spacing. SOLID 65 element was used for concrete and LINK180 element for modelling reinforcement. The analysis as per the report generated by the ANSYS software, seems to stop on 156th iteration and the results were then obtained. Load-deformation and ductility index of the beams were obtained from software and were compared with experimental values. Crack pattern was also obtained using linear analysis. The percentage error occurred in terms of ultimate load, total deformation and ductility index is less than 10%. It was found that as the number of shear connector provided was beyond the permissible number there can be crowding which could result in more cracks. Hence, it is advisable to not to use increased number of studs, as that may result in harming the serviceability conditions of structure.

Experimental Study and Numerical Analysis on the Shear Resistance of Bamboo Fiber Reinforced Steel-Wire-Mesh BFRP Bar Concrete Beams.

Bamboo fiber is a natural and environmentally friendly material made from cheap and widely available resources and is commonly selected as the reinforcement material for steel-wire-mesh BFRPbar concrete beams. In this work, the effects of various fiber lengths and fiber volume rates on the shear properties of bamboo-fiber-reinforced steel-wire-mesh basalt fiber composite reinforcement concrete beams were studied through a combination of shear tests and numerical simulations. The findings demonstrate that the addition of bamboo fiber improves the cracking performance of the beam. The improvement effect of 45 mm bamboo fiber mixed with a 1% volume rate was the most obvious at about 31%. Additionally, the test beam's total stiffness was increased, and the deflection was decreased. However, the use of bamboo fiber was found to decrease the concrete's compressive strength, lowering the final shear capacity for the majority of beams. A method for estimating the shear capacity of the bamboo-fiber-reinforced steel-wire-mesh BFRPbar concrete beams is provided and lays the foundation for engineering practice, in accordance with the impact of bamboo fiber and steel wire mesh on beams that suffer shear breaks.

Numerical Modeling and Analysis of Strengthened Steel–Concrete Composite Beams in Sagging and Hogging Moment Regions

Strengthening of composite beams is highly needed to upgrade the capacities of existing beams. The strengthening methods can be classified as active or passive techniques. Therefore, the main purpose of this study is to provide detailed FE simulations for strengthened and unstrengthened steel–concrete composite beams at the sagging and hogging moment regions with and without profiled steel sheeting. The developed models were verified against experimental results from the literature. The verified models were used to present comparisons between the effect of using external post-tensioning and CFRP laminates as strengthening techniques. Applying external post-tensioning at the sagging moment regions is more effective because of the exhibited larger eccentricity. In the form of an initial camber and compressive stresses in the bottom flange prior to loading, this reasonable eccentricity induces reverse loading on the reinforced beams, reducing the net tensile stress induced during loading. Using CFRP laminates on the concrete slab for continuous composite beams is more effective in enhancing the beam capacity in comparison with using the external post-tension. However, reductions in the beam ductility were obtained.

Investigation on interfacial anti-sliding behavior of high strength steel-UHPC composite beams

This paper investigates the anti-sliding behavior of high-strength steel (HSS)-to-ultra-high performance concrete (UHPC) composite beams with perfobond strip connectors (PBLs). The experimental program is comprised of two test series. The first series of push-out tests were performed on six PBLs fabricated using HSS and UHPC. For each PBL, the load-slip curve, load-uplift displacement relationship, strain history, shear stiffness, ultimate resistance, failure modes, and ductility were recorded and discussed. For the second series, three HSS-UHPC composite beams were designed and manufactured. Based on the structural responses of the composite beams under four-point flexural loadings, the interfacial sliding behavior was presented and analyzed. By employing the theory of beams-on-elastic-foundation, expressions for calculating the anti-sliding stiffness of the composite beams were deduced. Experimental results indicate that the uneven load distribution among the multiple PBLs significantly reduced the shear performance of an individual PBL. Compared to a single-hole PBL, providing double holes in the perforated plate reduced the stiffness and strength of the individual PBL by 43% and 18%, respectively, while the corresponding stiffness and strength reductions for the PBL with triple holes were 51% and 19%, respectively. The perforated plates’ end-bearing effect improved the anti-sliding stiffness of the composite beam; however, the early cracking of the UHPC slab caused by the end-bearing led to a reduced yield load of the steel beam. The anti-sliding stiffness calculated from the proposed analytical formulas correlated well with experimental results. The proposed method is anticipated to provide a reference for the anti-sliding design of HSS-UHPC composite beams in practical applications.

Theoretical and Numerical Investigation of Damage Sensitivity of Steel–Concrete Composite Beam Bridges

To investigate the sensitivity of the overall mechanical performance of steel–concrete composite beam bridges (SCCBBs) to different types of damage, this paper proposes a method of analyzing the sensitivity of SCCBBs to damage based on the extremely randomized trees (ET) algorithm in machine learning. A steel–concrete composite continuous beam bridge was used as the engineering basis, and the finite element method was used to analyze the changes in the static and dynamic response of the bridge caused by seven types of damage. The proposed SCCBB damage sensitivity analysis theory was used to explore the sensitivity factors of the seven types of damage. The results show that microcracks in steel beams have the most significant impact on the mechanical performance sensitivity of SCCBBs, followed by the concrete slab stiffness degradation and bridge deck breakage. The sensitivity of the damage caused by transverse diaphragms and bridge pier stiffness degradation is relatively low, while the sensitivity of stud fractures and bearing damage is minimal. The impact factors of damage sensitivity were 0.51, 0.19, 0.13, 0.08, 0.05, 0.03 and 0.01. This research can provide a reference for the damage classification of SCCBBs with multiple damage interlacing.

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 analytical investigation on shear mechanism of steel-UHPC composite T-Perfobond shear connectors

This paper proposed a T-Perfobond shear connectors to increase the end bearing area of the intermittently arranged PBL shear connectors. The failure modes, load-slip curves, and strains of perforating rebar of T-Perfobond shear connectors were discussed. Following that, a finite element analysis (FEA) model was established to investigate the influences of design parameters on the behavior of T-Perfobond shear connectors. A theoretical shear bearing capacity prediction method on T-Perfobond shear connectors was proposed, which can consider the effect of end concrete bearing pressure and the reduction coefficient of welding effect. The results showed that the specimens failed in three stages with bond damage, concrete dowel fracture and end concrete crushing. The shear bearing capacity of T-Perfobond shear connectors increased with the increase of web plate thickness and decreased with the increase of flange plate thickness. The hole diameter weakened the web plate strength and reduced the stability of T-Perfobond shear connectors. The theoretical predictions agreed well with the experimental and numerical calculation results. This study can be used to guide the design and application of shear connectors of steel–concrete composite beams.

Detection of interface flaws in Concrete-FRP composite structures using linear and nonlinear ultrasonics based techniques

Timely and appropriate retrofitting of existing structures holds paramount importance to ensure the structural integrity and sustainability. Fiber Reinforced Polymer (FRP) composites with high corrosion resistance, strength and durability, have been increasingly used in recent years for retrofitting of concrete infrastructure. The effectiveness of retrofitting is primarily dependent on the appropriate integrity at the interface between FRP and concrete substrate. Presence of any interface flaw can jeopardize the structural performance. In the present study, investigations are carried out to detect the early stage flaws at the FRP-concrete interface using ultrasonic waves. Artificial flaws of different size are introduced in the adhesive (epoxy) layer of carbon based FRP composite concrete beam. Rayleigh waves (at different frequencies) are generated for measuring the response from different FRP composite-concrete specimens. The specimens consist of three different types of materials, namely, concrete, epoxy and FRP. Two different input excitation frequencies, i.e., 75 KHz and 250 KHz, are tried out during the experimental investigations. The output signals are processed using different linear and nonlinear ultrasonic methods. Numerical simulations are also performed to better understand the wave signals’ interactions with the multi-layer composite medium. The results showed that the linear ultrasonic methods are not able to provide a consistent information on presence and extent of flaws. Nonlinear ultrasonic methods showed significantly better performance for characterizing both small and large flaws considered in this investigation. Sensitivity analysis reveals that relatively new and promising nonlinear ultrasonic technique, namely, the Sideband Peak Count-Index (SPC-I) performs remarkably well for detection of flaws in FRP-concrete interface.

Fatigue Experiment Study on Internal Force Redistribution in the Negative Moment Zone of Steel–Concrete Continuous Composite Box Beams

Due to the accumulated fatigue damage in steel-concrete continuous composite box beams, a plastic hinge forms in the negative moment zone, leading to significant internal force redistribution. To investigate the internal force redistribution in the negative moment zone and confirm structural safety under fatigue loading, experimental tests were conducted on nine steel-concrete continuous composite box beams: eight of them under fatigue testing, one of them under static testing. The test results showed that the moment modification coefficient at the middle support increases during the fatigue process. When approaching fatigue failure, an increase of 1.0% in the reinforcement ratio or 0.27% in the stirrup ratio results in a reduction of 13% in the moment modification coefficient. Furthermore, a quadratic function model was proposed to calculate the moment modification coefficient of a steel-concrete continuous composite box beam during the fatigue process, which exhibited good agreement with the experimental results. Finally, we verified the applicability of the plastic hinge rotation theory for steel-concrete continuous composite box beams under fatigue loading.

Flexural performance of prefabricated U-shaped UHPC permanent formwork–concrete composite beams reinforced with FRP bars

Flexural performance of prefabricated U-shaped UHPC permanent formwork–concrete composite beams reinforced with FRP bars

Experimental investigation on flexural strength behaviour of reactive powder concrete

The performance of a composite conventional beam and a reactive powder concrete beam with various forms of reinforcement, such as PVC tubes, stainless steel tubes, and normal reinforcement, is compared in this project through an experimental comparison. In this study, experimental research on four specimens of conventional concrete beams and four specimens of reactive powder concrete beams was conducted using the two point loading test method, and mechanical properties such as flexural strength of composite beams were tested for M20 grade of conventional concrete beams and reactive powder concrete beams. The flexural strength of reactive powder concrete beams combined with conventional composite beams. Comparing the composite Reactive powder concrete beam with normal reinforcement to the composite concrete beam with normal reinforcement, the flexural strength is enhanced by 8.78%. Comparing the composite Reactive powder concrete beam with stainless steel reinforcement to the composite concrete beam with stainless steel reinforcement, the flexural strength is increased by 7.58%. When compared to composite concrete with PVC reinforcement, the composite Reactive powder concrete beam has a 5.6% higher flexural strength.

Experimental and theoretical study on flexural behavior of steel–concrete composite beams strengthened by CFRP plates with unbonded retrofit systems

In this paper, the flexural behaviors of steel-concrete composite beams strengthened by prestressed carbon fiber-reinforced polymer (CFRP) plate with unbonded retrofit systems were investigated via four-point bending experiments. Three composite beams were strengthened by two groups of CFRP plate with thickness of 2mm or 3mm and prestress level of 10% or 15%, while one un-strengthened composite beam played a role as reference specimen. CFRP plate was transversely stretched by two scissors-type jacks and fixed on the tension flange of steel girder by an independently designed mechanical anchorage system. The experimental results reveal that the application of prestressed CFRP plate efficiently increased the yielding load and ultimate load of steel-concrete composite beams, but the ultimate deflection of mid-span was little affected. The increase of cross-sectional area of CFRP plates contributes more to stiffness of beams than that of prestress level. The CFRP strength utilization ratios of strengthened beams BS-1 and BS-3 at failure are 80%, under the condition of proper anchorage. Moreover, the prestress loss of CFRP plate was monitored for about 100h before test, which was less than 3%. Furthermore, a theoretical model was proposed to calculate the ultimate flexural resistance of strengthened steel-concrete composite beams with unbonded retrofit systems, which was validated with the experimental results.

Experimental and Analytical Investigation on Flexural Behavior of High-Strength Steel-Concrete Composite Beams

This research investigated the flexural behavior of high-strength steel (HSS)—concrete composite beams. The effect of concrete strength on the load-deflection behavior, flexural capacity, and ductility of HSS—concrete composite beams was investigated. Four full-scale HSS—concrete composite beam specimens were tested under static load. The test results demonstrate that the failure mode of HSS—concrete composite beams is flexural failure of the steel member and compression fracture of concrete at mid-span. The HSS—concrete composite beam exhibits good mechanical performance and deformation behavior. The ultimate bending strength and ductility of HSS—concrete composite beams were improved with the increased concrete strength. The theoretical results demonstrate that the simplified plastic method overestimates the ultimate bending strength of HSS—concrete composite beams. The main reason is that only a small part of the steel beam bottom shows plastic strengthening, which is not enough to make up for the strength loss caused by the steel near the neutral axis failure to yield and the relative interface slip. The nonlinear method based on material constitutive model could predict the load-bearing capacity accurately. After analyzing the ultimate bending capacity of 192 sample beams, the simplified plastic method was modified, and the theoretical method for ultimate bearing capacity of HSS—concrete composite beams was proposed.

Numerical study of steel–concrete composite cellular beam using demountable shear connectors

Steel concrete composite beams have been increasingly used in practice due to their advantages with respect to their structural features and constructability. However, in conventional composite beam systems composite action is applied via shear connectors welded at the top flange of the down-stand steel beam and embedded in the concrete slabs, making it less favourable for the beam system to be disassembled and reused. This paper presents a numerical study of a new composite beam system consisting of a cellular steel beam, metal deck flooring and demountable shear connectors. According to the experimental study, this composite beam system made the demounting, reassembly, and member reuse possible, and did not compromise the loading capacity. In the numerical study presented in the paper, a finite element model was developed and validated against the results obtained from the previous experimental study. The parametric study further examined the effects of concrete strength, shear connector arrangements and asymmetry ratios of steel beam section to the load capacity of the composite beam system. The analysis and comparison provided a deeper insight into the behaviour of this type of shear connector. Through this numerical study, the structural merits of the composite beam system using demountable shear connectors were highlighted. Finally, the mid-span plastic moment of the composite beam was predicted using the direction method provided in SCI publications and compared with the moment–deflection relationship obtained from FE modelling.

Large scale fire resistance tests of prestressed continuous steel–concrete composite beams to evaluate the effects of geometric imperfections

Little attention has been devoted to exploring the effect of geometric imperfections under fire conditions. To bridge this knowledge gap, this paper presents findings from five large scale fire tests on prestressed continuous steel–concrete composite beams (PCCBs) designed to investigate the effect of initial geometric imperfection (IGI) on the fire resistance of PCCBs. The examined parameters include several IGI modes, load levels, and prestress levels. Various fire responses were monitored and recorded during these tests, such as cross-sectional temperature rise, mid-span deflection, prestress in the cable strands, and side-support reactions. The results of these fire tests indicate that PCCBs with the initial mode of flexural–torsional buckling at the middle support applied as an IGI had larger mid-span deflection and lower critical temperature relative to that of the beams without IGI. The same beams also underwent a larger degree of relaxation in prestress levels, thus reaching failure at a faster pace. Our findings also indicate that while the end-support reactions were redistributed when exposed to fire, the side-support reactions decreased at the first stage of fire exposure and then gradually increased toward the final stage of the fire exposure. Evidently, for PCCBs with IGI, the side-support reaction towards the end of the fire tests is larger than the initial reaction. To complement the conducted fire tests, a series of finite element (FE) models were developed to further study the effect of IGIs in terms of the fire response of PCCBs.

Performance analysis of the ultra high performance concrete composite beam subjected to impact loads

Ultra High Performance Concrete (UHPC) has gradually become the most promising high-performance material, and has achieved good results in the field of impact and explosion protection engineering. In general, normal reinforced concrete (NC) beams subjected to impact load are prone to local punching shear failure. Although pure UHPC beams can improve their impact performance, their further application is limited by the high cost. In order to achieve the balance between impact resistance and economy, this study puts forward the design scheme of local replacement and wrapping with UHPC to improve the impact resistance of reinforced concrete beams. In this work, the different research conditions including NC beam, UHPC beam and NC-UHPC composite beam are designed, and the impact resistance of specimens is compared and analyzed. The results show that UHPC local replacement scheme can effectively avoid local punching shear failure of beams. As for the UHPC wrapping scheme, the failure mode of the beam changes from punching shear failure to bending failure. Compared with NC beams, two schemes can effectively reduce the peak displacement and residual displacement in the mid-span. The peak displacement and residual displacement in the mid-span of the UHPC local replacement beam are smaller than that of UHPC wrapping schemes, and the mid-span bearing capacity is better. In this work, it is recommended to take a local replacement length greater than 2 times the beam height to avoid local punching shear failure.

Flexural behaviour of deconstructable composite beams

In order to promote the development of full life-cycle deconstructable steel–concrete composite beams, and to better understanding their flexural behaviour, an experimental study on the flexural performance of a novel deconstructable steel–concrete composite beam is carried out in this paper. With various connector (bolt) diameters (M20, M24) and material strengths (C40, C50 concrete) being incorporated, the failure mode, load–deflection response, load-slip response, strain distribution, ductility, characterised loading capacities and deconstructability are analysed thoroughly base on two-point loading tests. By comparing the test results with that specified in national standards for the flexural capacity and stiffness of the composite beams, new calculation formulae for this new deconstructable composite beams are put forward. By employing the shear-slip constitutive model proposed previously for shear connectors of such deconstructable composite beams, a finite element model is developed and further validate against experimental results. Subsequent parametric analyses are carried out, and the mechanism of shear connection is analysed accordingly. In addition, effects of different parameters (including sectional dimension, strength of concrete and degree of shear connection) on their flexural capacity, stiffness and interface slip are clarified.

Experimental study on the seismic performance of a cold-formed thin-walled steel–concrete composite column-H steel beam frame

For lightweight steel frame structures consisting of steel H-beams and cold-formed steel columns filled with concrete, seismic performance comparison tests and numerical simulation analyses were performed for bare and infilled frames. The effects of the lightweight wall panels, the axial compression ratio and the wall thickness of the steel sections of the columns on the seismic properties of the structure were investigated. The failure of the bare frame was concentrated in the weld fractures at the beam-column joints. When the wall panels were embedded in the frame, the damage was concentrated at the corners and edges of the wall panels and the connectors. The wall panels significantly improved the initial stiffness of the frame, early energy dissipation and resistance, and the wall panel energy dissipation rate was initially as great as 91%. As the axial compression ratio increased, the resistance of the structure significantly decreased. Under monotonic loading, the resistance on the structure with an axial compression ratio of 0.4 was reduced by nearly 44% compared to the structure without axial compression. Increasing the wall thickness of the steel sections of the columns increased the load-bearing capacity of the structure, but the increase diminished with increasing wall thickness.