•Sliding achievable by yielding of base shear connections can act as an energy dissipation mechanism.•Two types of connections were tested: one to yield in fasteners and the other one within a ...perforated zone.•The strength, stiffness, ductility, and failure mechanisms were determined.•Perforated connections provided 3 to 5 times greater ductility than the ones yielded in fasteners.•Perforated base shear connections could be used to achieve moderately ductile connections.
When cross-laminated timber (CLT) shear wall is designed for seismic loads, the Canadian timber design standard recognizes rocking as the sole energy dissipation kinematic mechanism to meet the capacity design requirement. The sliding mechanism, achievable by yielding of the base shear connections of CLT shear walls, is currently excluded. The focus of this research was on the yielding mechanism of base shear connections for mass timber shear walls as potential source for dissipating energy during major seismic events through sliding. Two types of base shear connections were evaluated: one was designed to exhibit ductile behavior through fastener yielding and the other was designed to yield within a perforated zone of steel bracket that was connected to the timber member with over-designed fasteners (i.e., capacity protected). In both cases, self-tapping screws (STS) were used as fasteners. Monotonic and cyclic tests were performed. The strength, stiffness, ductility, over-strength, and failure mechanisms were determined to investigate the use of these connections as reliable energy dissipating mechanisms. It was found that perforated steel plates provide a reliable yield mechanism with predictable yield and ultimate strength and displacement, and that damage in timber elements can be avoided when the fuses are combined with capacity-protected dowel-type fasteners. Both types of base shear connections under consideration behave in a ductile manner with some limitations under cyclic loading. While the perforated plate detail has the potential to qualify as moderately ductile connection, the other connection with fastener yielding mechanism may only exhibit limited ductility. An analytical model for predicting the yield and ultimate strengths, and ultimate deformation of the perforated plate was developed.
•Reviewed the four manufacture techniques for FRP profiles.•Reviewed six types of shear connections from the database of FRP-concrete shear connections.•Reviewed three typical failure modes of ...FRP-concrete hybrid sections.
Development of durable, cost-effective bridges is a pressing research topic. Previous research and field applications have shown that fiber reinforced polymer (FRP)-concrete hybrid sections, including beams and decks, are attractive options for bridge superstructures. To date, there have been many experimental results, analytical approaches, and field applications scattered in the literature. This paper aims to review and evaluate FRP-concrete hybrid sections in the context of bridge engineering. Two databases of flexural tests and push-out tests of shear connections are developed, respectively. The paper is organized as follows: First, the characteristics of materials and structural configurations are introduced according to the database of flexural tests. Then, six typical types of shear connections from the database of push-out tests of FRP-concrete shear connections are compared. Next, three typical failure modes and deformation of FRP-concrete hybrid sections are separately analyzed with necessary design equations. Finally, case studies and perspective future development are discussed.
An external ENTA damper system or steel frame seismic retrofit approach was investigated for historic reinforced concrete (RC) buildings. RC frame specimens were evaluated under cyclic lateral ...loading to confirm the external retrofit approach. The investigation involved an examination and comparison of hysteresis-based behaviors, such as strength, ductility, and energy dissipation, with the aim of gaining a deeper comprehension of the distinct impacts of external retrofit systems on seismic performance. The experimental findings indicate that the implementation of the external ENTA damper system and steel frame effectively enhanced the stiffness and durability of vulnerable RC moment frames, while maintaining their deformation capacity. The enhancement of the energy-dissipation capacity was achieved by the use of measures to prevent premature failure of the RC beam-column joints. On the basis of the experimental results, the failure mechanism of the RC frame was discussed, considering the shear connection behavior. In order to further validate the experimental results, analytical modeling of the undamaged specimens was carried out using the LS-DYNA program. The test strengths of the frame specimens were evaluated and compared to the anticipated values derived from a simple plastic mechanism.
•The ENTA damper systems increased the load-bearing capacity of the RC frame structures.•ENTA damper systems significantly improved the stiffness resistance and energy absorption of RC frame structures.•The ENTA damper systems prevented serious damage to the beam-column joints in RC frame structures.•The FE model appropriately predicted shear, ductile and behavior concrete failure in RC frame and retrofitted RC frame.
•A finite element model of steel–concrete composite beam was developed and validated.•A parametric study was performed to evaluate the minimum degree of shear connection.•A conditional reduction of ...the allowed utilization factor of the beam is proposed.
This manuscript presents a numerical study on simply supported propped composite beams with ductile shear connectors subjected to uniformly distributed load. The aim is to assess the performance of the revised rules for the minimum degree of shear connection (CEN/TC250/SC4.T3) with respect to the occurring slip. First, a non-linear 3D finite element model was developed through the software ABAQUS 2017 and validated against analytical and full-scale beam test results. Then, 91 configurations were analysed for different degrees of shear connection η = 0.2, 0.4, 0.6, 0.8 and 1.0. The span ranges from 6 to 25 m while the geometrical and mechanical properties varied within their typical field of applicability. According to both current and revised rules, 16 configurations with relatively deep beam and “weak” concrete slab exhibited allowable slip values smax significantly higher than 6 mm. Therefore, the authors proposed a reduction of the maximum degree of utilization to these special cases. If the proposed reduction is included in the revised rules, none of the considered cases exhibit a slip smax higher than 8 mm while few cases have smax between 6 and 8 mm. For the ease of use, a design proposal is reformulated as a conditional reduction of the plastic bending resistance of the composite section.
To successfully facilitate the construction sector's transition toward sustainability, there is an urgent need for alternatives to the existing practices which are not sustainable. Steel-timber ...composite (STC) beams, which combine a down-standing steel beam and a timber slab for flooring systems, show large potential as sustainable alternative to conventional steel-concrete composite systems. In STC systems the shear connection is a key element that keeps the elements together and ensures effective composite action. This study presents a comprehensive experimental assessment of novel shear connections for demountable STC beams and flooring systems. The research focused on three newly developed bolted shear connector types: SCT-1, SCT-2, and SCT-3, each incorporating a different shear connection device designed to protect the timber and enable the attainment of the required preload for high-strength bolts. These novel shear connections represent a robust and sustainable alternative to conventional connections, offering superior protection to structural elements. The connections were tested in a double-symmetric push-out test setup, implementing laminated veneer lumber (LVL) plates connected to HEB steel profiles. Their performance was assessed in terms of their load-slip responses, stiffness, and failure mode. The load-slip responses were found to be nonlinear, and the connectors exhibited a significant deformation capacity (greater than 40 mm slip). The results of this study indicate load-bearing capacities per shear connector at a 6 mm slip of 95.7 kN, 104.4 kN, and 120.2 kN for SCT-1, SCT-2, and SCT-3, respectively. Additionally, the maximum loads per shear connector were recorded as 161.4 kN for SCT-1, 173.1 kN for SCT-2, and 163.8 kN for SCT-3. Furthermore, the shear connections introduced in this study offer ease of installation and facilitate the assembly and disassembly of components.
•Three novel STC shear connectors enhance assembly/disassembly of the components.•The new STC connectors allow the attainment of the preload for high strength bolts.•The connectors show nonlinear load-slip response and significant deformation capacity.•The connections are a robust, sustainable alternative to conventional connections.•Load capacities per shear connector exceed 95 kN at a 6 mm slip.
The AISC 360-16 Specification recommends that the design shear force between parts of a composite column in the load introduction area shall be calculated based on the force allocation at ultimate ...limit state. Applicability of this straightforward method to the load levels that usually arise in slender composite columns is questionable, as this capacity-based force allocation is only true when the axial force is equal to the plastic resistance of the composite cross-section. Next, the number of required shear connectors is calculated as a quotient of the design shear force and the strength of a single shear connector. We demonstrate that: first, for the lower load levels, the stiffness-based force allocation gives a more accurate estimate of the shear force; second, the number of shear connectors satisfying the strength requirement can lead to insufficient force transfer between parts of the composite cross-section. To investigate the shear transfer mechanism in composite columns, we derive an analytical model with linear elastic constitutive relations both for steel and concrete and three types of shear force slip laws: elastic, elastic plastic, and rigid plastic. The case studies carried out for different shear transfer scenarios demonstrate the importance of the shear connection stiffness on the effectiveness of the load introduction. The remaining portion of the shear force is transferred outside the load introduction area, which hampers the column’s ability to withstand shearing from varying bending moments or incipient buckling. To control the shear force transfer efficiency by enhancing the shear connection stiffness, we propose an original Stiffness Method and provide design charts as an aid in the design process.
•Force allocation in composite columns revisited.•The axial stiffness of column parts drives force distribution for typical columns.•Closed-form solutions for shear transfer between cross-section parts.•Shear connection stiffness affects the effectiveness of load introduction.•Proposed stiffness method allows controlling the force transfer effectiveness.
•Repeated seismic loadings reduce resisting capacity of beam–slab shear connection.•Pull–push test specimen was constructed with a stubby Y-type perfobond-rib.•Specimen was evaluated in monotonic and ...fully reversed cyclic loading tests.•Specimen showed better hysteretic performance than conventional stud shear connection.
In the composite frame of a building structure in an earthquake-prone area, the shear connection between a concrete slab and a steel beam plays a very important role in distributing the load of the structure and preventing collapse. A shear connection with high stiffness evenly disperses the inertial force created by an earthquake load throughout a pillar to increase the resisting capacity of the structure. In addition, after receiving the seismic loading, the residual strength of the shear connection delays separation of the slab from the beam, thus preventing secondary accidents. However, a beam–slab shear connection of a composite structure that is subjected to frequent seismic excitation receives repeated loadings far exceeding design loadings, thereby greatly reducing its resisting capacity from the level in the original design. The Y-type perfobond-rib shear connector belongs to the new generation of shear connectors developed to overcome the disadvantages of the conventional stud shear connector and the perfobond-rib shear connector. In order to analyze the behavior of the shear connection, fully reversed cyclic loading tests were carried out on a stubby Y-type perfobond rib shear connection and a stud shear connection. Using the test results, the amount of energy absorbed by the connections and changes in their stiffness were verified, which also showed that the former exhibited better hysteretic performance.
Existing composite floor design approaches require technical data on strength and ductility of shear connectors, which can be defined only by shear tests. The article discusses the failure modes of ...composite floor shear connection, made of powder-actuated shear connectors. The influence assessment of the main detailing parameters on the strength and deformability of shear connectors was executed. The database for analysis included the results of shear tests performed by both the authors and other researchers. According to the results of the study, the dependence of the strength and deformability of shear connectors on their height, orientation relative to the shear force vector, the strength of the concrete slab and the geometric parameters of the profiled flooring was estimated.
A novel shear connection system for GFRP box-concrete composite girder was proposed and experimentally and analytically investigated in this paper. The novel connection system consists of T-bolts and ...sand coating, and can be easily installed at the GFRP box section with closed shape. The proposed connection system can improve the slip stiffness of GFRP box-concrete interface, and provide sufficient shear resistance and ductility. The effects of low temperatures (T = 20, −30, −60, and −80 ℃), longitudinal spacing of T-bolts (SL=100, 150, and 200 mm), aspect ratio (hef/d=3.2, 5.2, and 7.2), and GRRP-concrete interface type (IT=combined connectors with T-bolts and sand coating, sand coating, T-bolts, and blind-bolts) on interfacial shear behaviours were evaluated through twenty-four push-out tests. Failure modes and load-slip/strain curves at different temperatures were plotted. Experimental results showed that decreasing temperature from 20 to − 80 ℃ increased the shear resistance of sand coating and slip stiffness of push-out testing specimens, but exhibited little effects on their ultimate shear resistances. Analytical equations to predict the ultimate shear resistances of push-out testing specimens have been developed and validated by the test results. Besides, load-slip modes for specimens with different interface types were also proposed with good accuracy.
•Combined connectors with T-bolt and sand coating are proposed for composite girder.•Combined connectors improve the slip stiffness, shear resistance and ductility.•Low temperature increases the interfacial shear resistance and slip stiffness.•Analytical models predict well the ultimate shear resistance and load-slip curves.
•UHTCC can achieve high toughness and excellent cracking resistant performance.•Application of UHTCC in composite bridge decks is explored via five flexural tests.•Nonlinear finite element models are ...established and validated against test results.•A parametric study is conducted to reveal the flexural behavior.•Existing formula for flexural resistance is modified with improved accuracy.
Traditional steel–concrete composite bridge deck (CBD) is prone to crack in the concrete layer, which reduces its flexural capacity and durability. Due to the excellent crack resistance behavior and characteristic of tensile strain hardening, ultra-high toughness cementitious composite (UHTCC) has become a promising material to solve this problem. In this study, the flexural performance of bridge decks composed of steel and UHTCC using shear studs is analyzed by means of experimental research and finite element (FE) analysis. Five steel-UHTCC CBDs with different shear connection degrees and rib dimensions were fabricated and tested. Then, FE models of steel-UHTCC CBDs were established by ABAQUS, involving FE examples for comparing with the tests and 10 groups of models to conduct a parametric study. The flexural resistant performance of steel-UHTCC CBDs was studied concerning the key design parameters, including stud number, span length, rib dimension, thickness of UHTCC and longitudinal reinforcement ratio. The effect of shear connection degree on the flexural resistance of CBDs was discussed in detail. Finally, a modified theoretical formula was proposed for predicting the flexural resistance of steel-UHTCC CBDs.
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