Experimental Study on Mechanical Performance of UHPC Formwork-RC Composite Cap Beam

Shear connectors are required to build composite (concrete and steel) beams. They are placed at the interface of concrete and steel to transfer shear and normal forces between two structural components. Such composite beams are sensitive to provide structural integrity when exposed to fire as they loss strength, stiffness, and ductility at elevated temperature. The present study is designed to investigate the shear resistance and the failure modes of the headed stud shear connectors at fire exposure and post-fire exposure. The study includes ordinary concrete and concrete with carbon nanotubes (CNTs) to build composite (concrete-steel) beams with structural steel. Experimental push tests were conducted on composite beams at ambient and elevated temperatures, such as 200, 400 & 600℃. Moreover, push tests were performed on the composite beams after being exposed to 200, 400 & 600℃. Push test results illustrated the reduction of ultimate shear capacity and stiffness of headed stud shear connectors as the temperature increased. Although similar values of ultimate shear were obtained for the headed stud connectors in both ordinary and CNT concrete, the CNT modified concrete reduced the concrete spalling and cracking compared to ordinary concrete and was observed to be effective at temperatures greater than 400°C. All specimens showed a lower shear resistance at fire exposures compared to the corresponding post-fire exposures. Moreover, numerical simulation by Finite Element (FE) analyses were carried out at ambient temperature and at fire conditions. The FE analysis results show a good agreement with the experimental results. In the experimental studies, failure of all specimens occurred due to shear failure of headed stud, which was later validated by FE analyses using ABAQUS.

This work deals with the behavior of structural continuous composite steel-concrete beams. In the present study, an experimental work has been done by casting and testing two simply supported composite beams, (with and without steel fibers) and two continuous composite beams (with and without steel fibers) up to failure to examine its behavior under static loads. The steel fiber volumetric percentage was 0.5 %. Also, cubic and cylindrical specimens have been cast and tested to determine the concrete compressive and tensile strengths. A high range water reducing admixture (HRWRA) and silica fume (SF) have been used as additives to enhance the fiber concrete properties. So, several trial mixes have been cast and tested to determine the better ratio of these mixtures with respect to the concrete mechanical properties. In the present research, available experimental tests on composite steel-concrete beams are theoretically analyzed using the finite element technique based on one dimensional model. The adopted one dimensional model is able to simulate the overall flexural behavior of composite beams, this covers; load-deflection behavior, longitudinal slip at the steel-concrete interface, and distribution of shear studs. Comparison between the experimental results (for deflection and loads of failure) with those obtained from the proposed finite element model indicates acceptable agreement. It is found that the difference in deflection value between experimental results and theoretical results for no-fiber simply supported composite beam reach 11%, and at 0.5 % steel fibers percentage reach 13 %. While in the continuous composite beam for plain concrete the difference in results may be 9 %, and at 0.5 % steel fibers percentage may be 12 %.

Introduction: The current research focuses on the vibration and buckling behaviors of composite cantilever beams using both numerical and analytical approaches: The need for precise structural analysis of advanced engineering applications. ANSYS is utilized to perform finite element simulations, and semi-analytical models based on classical beam theories are developed to verify the numerical results. Results indicate that increasing the fiber volume fraction (from 40% to 60%) causes an increase of 22.5% in the fundamental frequency and an enhancement of 35.8% in the critical buckling load. Moreover, with an increase of 10 to 20 in aspect ratio, natural frequency increases by 17.3%, while it leads to a decrease of 12.6% in buckling resistance. Statistical regressions analysis show strong nonlinear correlations (R² = 0.92) between shifts in frequency and compressive loads applied. The experimental data presented in this work highlights the significance of endeavoring to directly and geometrically optimize composites when enhancing the dynamic stability of composite beams, contributing insights relevant to aerospace and mechanical systems domains. 8 that DOI: The results obtained through this study serve as a solid foundation for experimental studies and future developments of composite structure engineering Objectives: This research aims to characterize fractures' effects on composite beams' natural frequencies, assess their stability under different loading circumstances, and suggest crack detection inspection methods. Fibre fracture depth, location, and direction affect beam modal characteristics. Methods: This research compares the quantitative and qualitative data of vibration and buckling behaviours of composite cantilever beams. This, coupled with finite element modeling analysis, the application of the classical beam theory and physical testing, offers a complete perspective of the structural response of the epoxy beams with differing fiber fractions and ratios. In addition, several correlation analyses are carried out between the changes of frequency and compressive load to enhance the validation of the proposed models as well. Results: This research corroborates all three hypotheses and brings deep insight into the vibration and buckling characteristics of composite cantilever beams. Both the numerical and analytical methods assisted in the fundamental frequency and buckling load associated with the first hypothesis (H1), H1. Conclusions: Further research needs to include verifying the numerical and analytical models with real composite beam specimens. Also, sophisticated nonlinear material finite element analysis combined with more advanced loading patterns will yield better results. Broader ranges of fiber volume fractions and fiber aspect ratios could be added to the statistical model, thus making it more useful for diverse engineering problems.

Compared with straight steel–concrete composite beams, curved composite beams exhibit more complicated mechanical behaviors under combined bending and torsion coupling. There are much fewer experimental studies on curved composite beams than those of straight composite beams. This study aimed to investigate the combined bending and torsion behavior of curved composite beams. This paper presents static loading tests of the full elastoplastic process of three curved composite box beams with various central angles and shear connection degrees. The test results showed that the specimens exhibited notable bending and torsion coupling force characteristics under static loading. The curvature and interface shear connection degree significantly affected the force behavior of the curved composite box beams. The specimens with weak shear connection degrees showed obvious interfacial longitudinal slip and transverse slip. Constraint distortion and torsion behavior caused the strain of the inner side of the structure to be higher than the strain of the outer side. The strain of the steel beam webs was approximately linear. In addition, fine finite element models of three curved composite box beams were established. The correctness and applicability of the finite element models were verified by comparing the test results and numerical calculation results for the load–displacement curve, load–rotational angle curve, load–interface slip curve, and cross-sectional strain distribution. Finite element modeling can be used as a reliable numerical tool for the large-scale parameter analysis of the elastic–plastic mechanical behavior of curved composite box beams.

Purpose This paper will study the flexural performance of multi-beam steel-hybrid fiber-reinforced concrete (HFRC) composite box beams, exploring the differences in the flexural performance of this type of composite beam under various shear connection forms and different types of loading conditions. Design/methodology/approach Flexural loading tests were conducted on two multi-beam composite beams, one with stud connectors and the other with Perfobond Leiste (PBL) connectors, under various types of loading conditions. Through comparative analysis of the failure modes, load-bearing capacity, ductility, shear lag effects, cross-sectional and rebar stresses, as well as relative slips of composite beams, the flexural performance of this type of composite beam was ultimately evaluated. Findings Under flexural loading, both specimens ultimately exhibited typical flexural failure characteristics and were consistent with the assumption of plane section. The composite beam specimens with stud connectors exhibited slightly higher flexural bearing capacity and average ultimate deflection of each main beam compared to those with PBL connectors, with increases of 1.13 and 10.05% in bearing capacity and deflection, respectively. Meanwhile, the composite beam specimens with stud connectors exhibit relatively better ductility, with displacement ductility coefficients of 3.63 and 3.36 for the two specimens, respectively. There were differences in both the magnitude of relative interface slip and the location where maximum slip occurred between the two specimens, with the maximum slip occurring at the support cross-section and L/4 cross-section, respectively. Furthermore, the differences in the influence of various types of loading conditions on the flexural performance of composite beams were determined through a comparative analysis method. Originality/value In this paper, HFRC is applied to composite beam structures, realizing a combination of high-performance materials and structures. Meanwhile, this study also considered different shear connection forms, the structural forms of bridges during actual service and operation and the stress states under various types of loading conditions. The corresponding conclusions derived from the analysis conducted in this study can provide certain reference for the design and application of practical engineering projects in the future.

The objective of this research was to develop a new composite material/system in structural civil engineering. To use of mechanical properties of bamboo-based panel and cold-formed steel, this study composite two kind of materials above-mentioned together utilizing structural adhesives. The research developed various of bamboo/steel composite members, such as composite slabs, composite walls, composite beams and composite columns. And the paper emphasized mechanical performance of bamboo/steel composite slabs and composite beams. Experimental studies on flexural behavior of 6 composite slabs and 9 composite beams were carried out and the failure process, failure modes and failure mechanism were investigated. Experiment results indicates that the bamboo plywood and cold-formed steel can form an excellent composite cross-section; Load vs. mid-span deflection curves of composite slabs and composite beams show linear on serviceability limit state. The maximum ultimate strength of composite slabs and beams have reached 30.0 kN•m and 36.13 kN•m respectively. The study shows that bamboo-steel composite members have good prospects in building structures of China.

Experimental and theoretical study on longitudinal shear behavior of steel-concrete composite beams

A dynamic instability analysis of fiber reinforced composite cantilever beams has been carried out in this study. Both experimental and numerical studies are performed to estimate the flutter speeds. Three different types of composite beams [namely, glass fiber reinforced plastics, aluminum fiber reinforced (glass reinforced aluminum), and multifunctional carbon fiber reinforced composites] have been considered in the analysis. A graphite fiber reinforced polymer matrix composite laminate with dimensions of is used in the experiments. The fibers are oriented along 0 deg: that is, along the direction of major dimension of the laminate. The experiments are conducted on three such beams by clamping one end of the beam to a heavy steel frame and leaving the other end free. The natural frequencies, mode shapes, and structural damping characteristics of each beam are estimated using the modal analysis through the fast Fourier transform analyzer. Variation of the damping and the frequency with wind velocity for each beam is illustrated through the and plots. The modal assurance criterion is also verified. Experiments are further continued to perform a dynamic instability analysis by clamping the beam inside the test chamber of a low-speed suction-type wind tunnel. The beam response at various wind speeds is captured through an accelerometer mounted at the tip. Based on the experiments, the flutter speed of the tested beams is estimated to be around . A numerical analysis framework is developed using the ZAERO code to perform the modal and flutter analyses. Numerical results are compared to the experimental results and are found to be in excellent agreement. Therefore, the numerical framework has been further extended to carry out the flutter analysis of the multifunctional composite beams, such as glass reinforced aluminum and plastic lithium–ion battery embedded composite beams. The multifunctional laminated composite beams are observed to have better dynamic stability as compared to the glass fiber reinforced polymer composite beams.

Experimental and theoretical study on mechanical properties of steel–concrete double-sided composite cantilever beams

An experimental study of simply supported ferrocement timber composite members is presented in this paper. An adhesively bonded connection is examined. Sikadur 31 thixotropic epoxy resin adhesive is used as a shear connector layer. The main purpose of the research is generating data and providing information about the structural behaviour of proposed ferrocement timber composite (FTC) beams. Several parameters studied including thickness, and width of timber beams, the number of wire mash layers of ferrocement slab and the presence and absence of a bonding layer of the shear connector and the effect of sag and hog bending moment. Ferrocement-timber composite (FTC) beams are a relatively new civil engineering solution and their behaviour should be investigated to develop relevant methods for calculating their resistance. The slip and the pinnacle load limit for connector were resolved tentatively in two push-out tests. The authors examined the stiffness and the strength of the connection used to join a ferrocement slab with a timber beam. These parameters are fundamental for planning composite beam, on the grounds that the conduct of a composite beam framework is relied upon the solidness and the quality of its associations. The composite beams specimens were subjected to a three-point loading test. Measurements also show that the connection could be considered perfect as the slip remains very little during the test (except at failure). Tests disclosed excellent loading capacity of the suggested beams relative to their weight. The use of epoxy resin can be providing appropriate bonding between the two layers. The energy absorption increases with increasing dimensions of timber. The maximum increase in load with increasing the depth of timber (72.5%) when the thickness of timber Change from (85 to 190) mm.

A comparative experimental study of prestressed continuous steel-concrete composite beams was carried out. Two continuous composite beams were tested, one of which was plain continuous steel-concrete composite beam, while the other was a composite beam prestressed with external tendons. Cracking behavior and the load carrying capacity of the beams were investigated experimentally. Full plasticity was developed in the mid-span section each beam, the maximum moments attained at the internal support sections however were governed by local buckling which was related to the slenderness of composite section. It was found that in hogging moment regions, the ultimate resistance of an externally prestressed composite beam would be governed by either distortional lateral buckling or local buckling, or interactive mode of these two buckling patterns. The results show that exerting prestressing on a continuous composite beam with external tendons will increase the extent of internal force and moment redistribution in the beam. The influences of local and distortional buckling on the behaviors of the composite continuous beams are discussed. The Moment redistribution and the load carrying capacity of the prestressed continuous composite beams are evaluated, and it is found that at the ultimate state, the moment redistribution in the prestrssed continuous composite beams is greater than that in non-prestressed composite beams.

The lateral torsional buckling (LTB) of steel-timber composite (STC) beam with partial interaction was investigated in this paper. The composite beam is constructed by connecting the timber to both flanges of the H-shaped steel with bolts or screws. Twelve push-out specimens were designed to evaluate the shear performance of bolt or screw connectors. It was shown that the slip stiffness and the shear bearing capacity of the connectors increased with the thickness of timber increasing. Then, eight full-scale composite beams with lengths of 6000 mm were studied through bending tests and compared to a bare steel beam. The experimental behaviors of the specimens were identified, including the failure mode, load-deflection relationship and load-strain response. The LTB phenomenon and composite action were discussed by analyzing the strain distribution, stiffness and strength. The results demonstrated that the STC beams fastened with bolts or screws displayed partial composite action. Although the stiffness of the composite beam showed little augmentation, the maximum strength of the composite beam substantially increased by suppressing the LTB phenomenon. A finite element analysis was conducted to reveal the failure mechanism of the specimens with different geometric and physical parameters, including the number of timber layers, the interface shear stiffness and the initial imperfection. It was found that increasing the number of timber layers in the upper flange suppressed the lateral torsional buckling, and the interface shear stiffness was the key factor to control the stiffness and failure modes of STC beams.

Ultra high performance concretes (UHPFRC) are characterized by a dense matrix and a high fibre content. These materials exhibit exceptional mechanical and durability properties making them an ideal material for rehabilitating existing structures. The primary interest in UHPFRC focuses on their uniaxial tensile performance. When they applied in a cast in place overlay configuration, they provide increased rigidity to the global element and localized protection to the steel reinforcement embedded in the concrete core during the service by minimizing surface cracking and inhibiting the diffusion of aggressive agents. At the ultimate state, and under certain configurations UHPFRC significantly improves the element's carrying capacity. The overall goal of this research is to study the UHPFRC tensile behaviour (hardening and softening behaviours) of characteristic test specimen and to apply this knowledge in analyzing the structural response of various composite elements. The objectives related to this study are: To determine the factors influencing the UHPFRC uniaxial tensile test specimen behaviour To illustrate the importance of UHPFRC tensile hardening and softening responses in UHPFRC structural plates and UHPFRC-reinforced concrete composite beams. To determine the rupture mechanism and overall contribution a UHPFRC overlay offers to a composite UHPFRC-reinforced concrete slab loaded to failure in flexural/punching shear. To study the parameters influencing the UHPFRC uniaxial behaviour in tensile composite structural elements. The behaviour of specimen with different configurations and compositions were studied in uniaxial tensile tests. The variables significantly influencing the fibre orientation were isolated by studying the fibre orientation at localized cuts in the various specimen. These controlling variables include: mixture viscosity, casting method, casting direction, fibre aspect-ratio and element geometry. Furthermore, a meso-level model was developed to predict the uniaxial tensile behaviour and was validated against the experimental test results. With the help of this model, the influence of the main fibre characteristics (Vf, Lf, df) on the resultant fibre orientation and matrix quality were examined. This model has determined that the extent of hardening does not increase linearly with the quantity of fibres but rather follows an asymptotic curve converging to a maximum possible hardening. A second model was developed to randomly orient and place fibres. This model has helped to explain the uniaxial tensile response variability of different mixtures ranging from conventional Fibre Reinforced Concrete (FRC) to UHPFRC. A finite element program has been employed to study the influence the UHPFRC softening behaviour has on the composite structural beam and UHPFRC plate responses. For a flexural plate (length 500mm, width 200mm, height 30mm), the bearing capacity was significantly increased by the very pronounced UHPFRC softening behaviour. Additionally, the UHPFRC layer noticeably increased the rigidity of the composite beam and slab. For example the UHPFRC layer increased the slab bearing capacity by 40% in comparison to a purely reinforced concrete slab by bridging the punching shear mechanism with a UHPFRC membrane effect. The structural responses of the two element types were then further analyzed using a finite element analysis program. An inverse analysis methodology was employed to obtain the UHPFRC tensile material laws in respective composite elements. These findings documented that a similar materials exhibited significantly different responses when applied in different applications. This analysis documents that the UHPFRC layer in a slab closely follows the uniaxial tensile test specimen response, while the UHPFRC layer in a composite beam exhibits a significantly reduced performance. The primary reasons for these variances are: the relative fibre distribution, the interface rugosity, the internal residual stresses and the extent of the maximum stress zone. Recommendations are made concerning the implementation of UHPFRC and the influence the fibre aspect ratio and volume (Vf, Lf, df) imposes on the resulting fibre orientation in different applications. Finally, a method for determining the UHPFRC characteristic curve which is required to design a composite UHPFRC-reinforced concrete element is presented.

The aim of this study is to examine the behavior of protected and unprotected steel–concrete composite I-beams with large cell diameters (D0/H = 0.7) and closely spaced cell configurations under the ISO 834 fire curve. Previous studies on experimental full-scale fire performances of cellular beams have been somewhat limited under vertical service loads and different insulation properties. To address this limitation, a total of four composite beams, two unprotected (one beam with a solid web, and one cellular beam) and two protected cellular beams (60 min fire resistance with implementation of water and solvent-based intumescent coatings) were tested. As outputs of the tests, the failure modes observed, such as web buckling, the Vierendeel effect, the slab behavior, including the mechanism of concrete cracking, the overall displacement behavior (i.e., deflected shapes) up to collapse at very large deflections, and temperature changes in the steel elements are discussed. It was concluded that the quality of the intumescent coating applied is crucial in achieving the desired fire resistance. Experiments showed that unprotected trapezoid deck voids did not have a decisive influence on the behavior of the beams for up to 60 min of fire testing. At high temperatures, similar crack patterns occurred in the composite slabs of the protected and unprotected steel–concrete composite cellular beams. In the protected beams, the behavior of reactive coatings was significant and resulted in a non-uniform temperature distribution in these beams’ web and flanges.

Damage of shear connectors in steel-concrete composite (SCC) beams affects the composite action and appears as abnormalities in the shear slip between the composite components. The shear slip at the composite interface causes nonlinearity in the global composite beam response which is an issue beyond the inherent complexity of the composite system. This paper presents a novel approach for damage detection of SCCs by variational mode decomposition (VMD) of shear slip data. Numerical and experimental studies were conducted on steel-concrete composite beams to generate noise-contaminated shear slip data from undamaged and damaged states of the structure. The VMD algorithm is employed to decompose shear slip signals into intrinsic mode functions (IMFs) and then, the center frequency of each mode is captured. The higher center frequency realized in the second mode is taken as a damage sensitive feature. Because IMFs curves are extracted from the signal splines interpolated between the average of the peaks and troughs, the change of energy in the center frequencies of the undamaged and damaged states can be defined as a damage index. Welch power spectral densities of the IMFs are calculated to further investigate changes in the center frequencies of IMFs obtained using the VMD algorithm. The empirical mode decomposition (EMD) technique is also utilized to decompose shear slip signals into IMFs for comparison purposes. The results show that the EMD is not able to detect abnormalities in the shear slip signals affected by damage because of losing information through several mode decompositions and a phenomenon termed mode mixing. However, when the VMD was set to decompose the signal into two IMFs, it was found that it is more efficient in maintaining the frequency content of the shear slip signal. According to the results, the proposed method has been proved successful in detecting damage of composite beams and can be employed as a reliable and robust technique.