Search Results (24)

Arch beams are widely used in bridge construction due to their ability to withstand much greater loads than horizontal beams. The utilization of composite construction has also increased due to its tendency to optimize the utilization of construction materials, leading to significant savings in steel costs. In this research, a detailed experiment work on a simply supported arch composite beam under a positive moment was presented; then, a numerical model was created using ABAQUS to simulate its nonlinear behavior. The beams were formed from a concrete slab attached to steel beams by means of perfobond shear connectors (PSCs). A good agreement between the model and experiment was obtained. A parametric study was developed to identify the influence of the initial prestressing, rise to span ratio, and beam length on the behavior of the arch composite beam. It was found that the presence of tendons enhances the serviceability behavior, increases the ultimate load by 40% compared to the control beam, and equilibrates the horizontal thrust of the arch, even in the absence of initial prestressing. In addition, the beam exhibits a clear tied arch behavior due to the large eccentricity as the rise-to-depth ratio increases. Furthermore, the prestress force was found to be more effective in the longer span and the incremental stress in tendons more remarkable. Full article

To enhance the uplift capacity and facilitate the installation of multi-row perfobond connectors at shallow burial depths, this study puts forward a novel notched T-perfobond connector. The design incorporates an integrated flange at the bottom of the connector and a notch at the edge of the hole. Through pull-out model tests on four notched T-perfobond connectors, this research investigates their failure mechanisms and pull-out capacities. Utilizing the explicit dynamics method in ABAQUS, a finite-element model of the pull-out resistance test for notched T-perfobond connectors is established and verified against experimental data. Furthermore, a detailed parametric analysis involving 54 models is conducted, examining crucial parameters such as rib dimensions, hole geometry, flange size, notch width, bar diameter, and material properties. Based on the combined experimental and numerical results, this paper assesses the suitability of current formulas for calculating the pull-out capacity of perfobond connectors and proposes a refined calculation method specifically for notched T-perfobond connectors. All the findings reported in this paper can serve as a reference in the design and construction of composite structures. Full article

Traditional stud and perfobond leiste (PBL) shear connectors are commonly used as load-transferring components in steel-concrete composite structures. Composite shear connectors fully utilize the advantages of traditional stud and PBL shear connectors. In order to maximize the advantages of composite shear connectors, a novel shear connector for complex environments was proposed. The steel-FRP composite bars (SFCBs) with excellent fatigue resistance and corrosion resistance were introduced to replace the steel bars. This study discussed the failure modes, load–slip curves, and load–strain curves of the composite shear connector. In addition, a finite element analysis (FEA) model was developed to analyze the influence of various factors on its shear behavior. Results showed that compared with traditional composite shear connectors, the introduction of SFCB resulted in a promotion of 7.85% in shear stiffness, and it also led to a significant increase of 63.61% in ductility, further enhancing the mechanical performance. Meanwhile, FEA models were well fitted to the test results, and parametric analysis showed variate effects on shear bearing capacity. In the end, an equation was established to calculate the shear capacity of composite shear connectors, which could provide a reference for further research and engineering applications. Full article

Based on the existing research on connectors, a web-embedded composite shear connector was proposed in this paper. Further, six types of push-out specimens were carried out on static push-out and low-cycle repeated load tests. The failure forms, load–slip curves, and load–strain curves of the tests are analysed. On the basis of the experiment, the finite element analysis is also carried out to enlarge the parameters of the specimens. The results showed that the shear stiffness of the web-embedded composite shear connector was larger than that of pure stud shear connector or perfobond rib shear connector, the slip limit was smaller, and ductility was good. A parameter analysis showed that penetrating steel rebars have the greatest impact on ultimate shear bearing capacity, reaching 43.82% of ultimate shear bearing capacity. Following repeated loading, the ultimate shear bearing capacity of the specimen decreased, the ultimate slip increased, and the ductility decreased. Based on the experimental results of this study, a new calculation equation for the ultimate shear bearing capacity of a web-embedded composite shear connector was proposed with a finite element model for verification. Full article

Steel–concrete composite decks are commonly employed in narrow-width steel box composite girder bridges to augment their lateral spanning capabilities, while the concurrent omission of longitudinal stiffeners leads to a substantial reduction in the number of components, thereby yielding a structurally optimized bridge configuration. This paper delineates the structural design parameters of a narrow-profile steel box composite girder bridge and assess the mechanical behavior of its incorporated steel–concrete composite deck under static and fatigue loading conditions. To this end, two full-scale segment specimens from the composite bridge decks were subjected to equal amplitude cyclic fatigue tests. The investigation specifically concentrated on the impacts of two types of shear connectors—namely, perforated steel plates combined with shear studs and perfobond rib shear connectors (PBL connectors)—on the static and fatigue performance, including fatigue stiffness, of the steel–concrete composite bridge decks. The results indicate that, under the static bending condition, the composite deck specimen equipped with stud connectors demonstrates superior overall flexural stiffness in comparison to the specimen featuring PBL connectors. Furthermore, the flexural stiffness of the steel–concrete composite specimens experiences a negligible alteration across two million fatigue loading cycles. Upon the completion of two million fatigue loading cycles, the composite deck specimens incorporating the shear connectors composed of perforated steel plates and shear studs exhibit relatively wider crack widths under the static peak load. Both configurations of the steel–concrete composite bridge deck specimens manifest evident interfacial detachment, signifying insufficient tensile pull-out stiffness of the shear connectors. It is recommended to increase the quantity of the shear connectors or select the pertinent types in order to enhance the interface shear resistance. Full article

In order to study the influence of steel fibers on the mechanical properties of Perfobond Leiste (PBL) shear connectors and improve the utilization of steel fibers in this structure, four push-out test specimens and eight finite element numerical models were produced to study PBL-type shear connector specimens with different steel fiber blending amounts and blending forms. The results show that in this structure, when the blending amount of steel fiber was 0.5% to 1.5%, the ultimate bearing capacity of the specimen improved linearly, and the steel fiber helped to give full play to the performance of the PBL shear connector. The steel fibers distributed in the Z-direction have a significant impact on the mechanical properties of the PBL shear connector, and the steel fibers distributed in this direction have a significant effect on increasing the ultimate bearing capacity of the specimen. Steel fibers distributed in the Y-direction can greatly improve the plasticity of concrete. In addition, the effective action area of steel fibers is the triangular area from the bottom of the PBL shear connector to the two tops of the concrete. Full article

Seismic-resilient buildings are increasingly designed following low-damage and free-from-damage design strategies that aim to protect the structure’s primary load-bearing systems under ultimate-level seismic loads. With this scope, damping devices are located in accessible and easy-to-inspect sites within the main structural frames where the damage concentrates, allowing the primary structure to remain mostly undamaged or easily repairable after a severe earthquake. This paper analyses the effects of friction-damping devices in structural joints of RC buildings endowed with hybrid steel-trussed concrete beams (HSTCBs) and standard RC columns. The study proposes innovative solutions to be adopted into RC moment-resisting frames (MRFs) at beam-to-column connections (BCCs) and column-base connections (CBCs). The cyclic behaviour of the joint is analysed through 3D finite element models, while pushover and non-linear time history analyses are performed on simple two-storey and two-span MRFs endowed with the proposed devices. The main results show that the BCC endowed with curved slotted holes and Perfobond connectors is the most effective in preventing the damage that might occur in beam, column, and joint, and it is adequate to guarantee good dissipative properties. For CBCs, the results showed that the re-centering system with friction pads is the most effective in containing the peak and residual drifts, preventing the plasticization of the column base. Full article

In terms of load transfer, the design of the joints in concrete-filled steel tubular (CFST) arch bridges is more critical than that in buildings due to the higher likelihood of steel–concrete-interface debonding. To improve the contact at the steel–concrete interface, a novel arch rib was manufactured by longitudinally welding perfobond-rib-shear connectors to the inner surface of a steel tube and then filling the tube with concrete. In this study, extensive numerical and analytical investigations on the mechanism of introducing loads into CFST arch ribs through perfobond-rib-shear connectors were carried out. A deck CFST arch bridge, namely, the Shuangbao Bridge in China, was selected as a typical application location. The design parameters, including the geometric dimensions of the perfobond-rib-shear connector and the arrangement of the perfobond rib along the cross-section and longitudinal section of the arch rib, were evaluated. The design flow for the joint with perfobond-rib-shear connectors between the vertical columns and the CFST arch ribs was proposed. To improve the load-transfer efficiency, the design scheme of the joint in the Shuangbao Bridge was optimized by replacing the weld studs with perfobond ribs. Significant increases of 1.84–4.02 in the shear resistance were found for the perfobond ribs compared to the welded studs. Additionally, the fabrication of the perfobond ribs was more convenient compared to that of the welded studs. Full article

In order to improve the shear resistance and structural ductility of the perfobond rib (PBL) connector, a new PBL connector with steel–rubber tenon is proposed in this study, which aims to increase the shear load capacity of the connector while improving the ductility of the connector. First, models of new PBLs are established based on the validated finite element method, and their mechanical properties are compared with other shear connectors. The results show that the stiffness and shear load capacity of the proposed connector can be effectively improved when the steel ring is added, where the shear stiffness can be reduced, and the deformation capacity of the specimen can be improved when the rubber ring is added. When a steel ring with a thickness of 5 mm and a rubber ring with a thickness of 5 mm are involved, the shear load capacity of the connector with steel–rubber tenon is increased by 13.7%, and the shear stiffness is reduced by 37.3% compared to the conventional concrete tenon connector, while the ductility is increased by 75.1% compared to the connector with steel ring tenon. Subsequently, as for the connectors with steel–rubber tenon, the effects of the thickness of the steel ring, the thickness of the rubber ring, the diameter of perforated rebar, the strength of concrete and the strength of perforated steel plate are analyzed based on the finite element model of a PBL. The results show that an increase in the thickness of the steel ring, the diameter of the perforated rebar and the strength of the concrete will cause an increase in the shear stiffness and shear load capacity of the connector; however, an increase in the thickness of the rubber ring can cause a decrease in the shear stiffness and shear load capacity of the connector, while a change in the strength of perforated steel plate has little effect on the shear stiffness and shear load-carrying capacity. Finally, based on the finite element parametric analysis results and the damage mechanism of the proposed connector, a calculation equation applicable to the PBL connector with steel–rubber tenon is presented to predict the shear load capacity of the connector. Full article

In order to make full use of the advantages of welded stud and perfobond rib shear connectors, a new type of composite shear connector is proposed. Studs are welded to the perforated steel plate of the PBL connectors. Six specimens were designed and tested to investigate the shear behaviour of the composite connectors. The effects of the hole number, welded stud number, and end-bearing modes on the shear behaviour of the composite connectors were discussed. In addition, the composite connectors were compared with the conventional welded stud and perfobond rib connectors to analyse the difference in shear performance. The composite connectors’ shear behaviours are significantly better than those of welded stud connectors and PBL connectors. The experimental results show that increasing the number of welded studs and perforated holes and end-bearing concrete can significantly improve the shear performance of composite connectors. Secondly, a finite element model was established considering the nonlinearity of the structure and was validated based on the experimental results. Finally, the effects of reinforcement diameter, welded stud diameter, and concrete strength on the shear performance of composite connectors were analysed. The shear resistance increases as the penetrating rebar diameter, welded stud diameter, and concrete strength increase. Moreover, the overall damage level of the concrete can be significantly affected. Full article

The difference between the shear performances of Perfobond Leiste (PBL) shear connectors embedded in steel fiber-reinforced cementitious composite (SFRCC) structure and normal strength concrete (NC) structure was investigated by push-out tests and finite element (FE) simulations. Push-out tests were carried out on nine steel-SFRCC specimens and nine steel-NC specimens. The mechanical behavior of the PBL shear connector was examined according to the failure modes, load-slip curves, and strain distribution laws of the push-out specimens. Experimental results revealed that the extension of cracks in SFRCC was hindered by steel fibers, and the number and width of cracks in SFRCC were smaller than those in NC. The failure mode of the steel-SFRCC specimens and the single-hole steel-NC specimens was the shear failure of the penetrating reinforcement, whereas that of the multi-hole NC specimens was concrete slab cracking. The ultimate shear bearing capacity of PBL shear connectors in the steel-SFRCC specimens was 47.8% greater than that in the steel-NC specimens. Furthermore, an FE model verified by the test results was established to conduct parametric analyses. It was found that the hole diameter and thickness of the steel plate and the yield strength of the penetrating rebar greatly affected the shear bearing capacity of PBL shear connectors. Finally, based on the experimental and FE simulation results, an expression for calculating the ultimate shear bearing capacity of PBL shear connectors in the steel-SFRCC composite structure was developed by considering the bearing effects of concrete dowels, penetrating rebars, and end parts. Full article

The PBL (Perfobond Leiste) shear connector has the advantages of high bearing capacity and strong constraint ability; however, the traditional PBL shear connector has strong and weak axis problems, and its stiffness is large, resulting in weak deformation ability. To this end, this paper proposes a new type of flange triple-web shear key and obtains the new shear key’s mechanical properties and failure mechanism through the push-out test. The results show that the failure mode of the new shear key is the deformation of the steel plate on the web and the edge of the opening, which has a high bearing capacity, outstanding deformation ability, and good integrity with concrete, showing obvious semi-rigid characteristics. Through numerical analysis, the effects of flange width, web height, and steel plate thickness on the mechanical properties of shear keys are obtained. Based on the fitting analysis method, the calculation formula of shear key bearing capacity is proposed. Finally, the horizontal seismic performance of the shear key is numerically simulated. It is found that the hysteretic curve of the shear key is full and shows good energy dissipation capacity. Full article

Superposed perfobond connectors are a type of connector used in composite structures. When the construction conditions are limited to increase the diameter of the opening, the shear capacity of the connector can be improved by enhancing the confining effect of the concrete dowel. In this study, 12 superposed perfobond connectors were fabricated to investigate the influence of lateral constraints on their shear behavior. The effects of hole area and holes’ number, diameter of the perforating rebar, concrete compressive strength, and the number of transverse reinforcements were investigated via the failure modes and load–slip curves. The results indicate that double-sided shear failure occurs in connectors with perfobond rib thicknesses exceeding 9 mm, and the connectors featuring strong lateral constraints not only exhibited higher bearing capacities but also superior load-holding capacities after peak load. Finally, an equation for the shear capacity of multi-hole perfobond connectors, considering lateral constraints, was proposed according to the double-sided shear theory. Full article

A series of full-scale pushed out tests were performed on the Perfobond rib shear connector. The tests were designed to examine the performance of the Perfobond rib shear connector under different rib hole sizes and shapes, reinforcing bar sizes, rib thicknesses, as well as the presence of lateral forces. It has been revealed from the test results that the rib hole size and reinforcement diameter may not act independently, and the influence of one’s size is actually dependent on the size of the other one. The lateral forces also affect the performance of the shear connector; for example, the capacity of the shear connector would be larger under compression than under tension. The existence of transverse pretension stress accelerated the cracking of concrete, leading to the strength and stiffness of concrete, perforated plate, and reinforcing rebars unable to fully exert their effect. In addition, the constraint effect of transverse stress improved the strength and stiffness of concrete and delayed the concrete cracking, bringing the strength and stiffness of concrete, perforated plate, and reinforcing rebars into full play, and resulting in a significant improvement in the shear capacity of Perfobond rib shear connectors. Full article

The steel–concrete composite structures consist of two different material parts, which are connected with reliable shear connectors to enable the combined action of the steel and concrete members. The shear connectors may experience either one-directional repeated cyclic loadings or fully reversed cyclic loadings depending on the structural functions and acting loadings. It is essential for structural engineers to estimate the residual shear strength of the shear connectors after action of repeated loads. The characteristics of deteriorating shear capacities of Y-type perfobond rib shear connectors under repeated loads were investigated to estimate the energy dissipating capacity as well as the residual shear strength after repeated loads. To perform the repeated load experiments four different intensities of repeated loads were selected based on the monotonic push-out tests which were performed with 15 specimens with five different design variables. The selected load levels range from 35% to 65% of the representative ultimate shear strength under the monotonic load. In total, 12 specimens were tested under five different repeated load types which were applied to observe the energy dissipating characteristics under various load intensities. It was found that the dissipated energy per cycle becomes stable and converges with the increasing number of cycles. A design formula to estimate the residual shear strength after the repeated loads was proposed, which is based on the residual shear strength factor and the nominal ultimate shear strength of the fresh Y-type perfobond rib shear connectors. The design residual shear strength was computed from the number of repeated loads and the energy dissipation amount per cycle. The reduction factor for the design residual shear strength was also proposed considering the target reliability level. The various reduction factors for the design residual shear strength were derived based on the probabilistic characteristics of the residual shear strength as well as the energy dissipation due to repeated loads. Full article