• Structural Engineering and Mechanics
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• v.83 no.6
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• pp.789-798
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• 2022

The stud shear connector is the main force transfer member in the steel-concrete composite member, and the mechanical behavior is very complicated in the concrete. The concrete around the stud is subjected to the pry-out local pressure concentration of the stud, which can easily produce splitting mirco-cracks. In order to solve the problem of pry-out local splitting of stud shear connector, a kind of stud shear connector with constraint measure is proposed in this paper. Through the push-out test, the interface shear behavior of the new stud shear connector between steel and concrete flange plate was studied, and the difference between the new stud shear connector and the traditional stud connector was compared. The results show that the stud shear connector with constraint measure can effectively avoid the adverse effect of local pressure splitting by relying on its own constraint measure. The shear stiffness of the interface between steel and concrete flange plates is greatly improved, which provides a theoretical basis for the design of strong connection coefficient of steel-concrete composite structures.

• Steel and Composite Structures
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• v.42 no.4
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• pp.477-487
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• 2022

The shear stiffness of headed-stud shear connectors has no unified definition due to the nonlinear characteristics of its load-slip relationship. A unified framework was firstly adopted to develop a general expression of shear load-slip equation for headed-stud shear connectors varying in a large parameter range based on both force and energy balance. The pre- and post-yield shear stiffness were then determined through bilinear idealization of proposed shear load-slip equation. An updated and carefully selected push-out test database of 157 stud shear connectors, conducting on studs 13~30mm in diameter and on concretes 30~180 MPa in cubic compressive strength, was used for model regression and sensitivity analysis of shear stiffness. An empirical calculation model was also established for the stud shear stiffness. Compared with the previous models through statistical analysis, the proposed model demonstrates a better performance to predict the shear load-slip response and stiffness of the stud shear connectors.

• Steel and Composite Structures
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• v.27 no.3
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• pp.355-370
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• 2018

In steel-concrete composite beams, longitudinal shear forces are transferred across steel flange-concrete slab interface by means of shear connectors. The connector behavior is highly non-linear and involves several complex mechanisms. The design resistance and stiffness of composite beams depends on the shear connection behavior and the accuracy in the connector resistance prediction is essential. However determining the stud shear resistance is not an easy process: analytical methods do not give an adequate response to this problem and it is therefore necessary to use experimental methods. This paper present a summary of the main procedures to predict the resistance of the stud shear connectors embedded in solid slab, and stud shear connectors in composite slab using profiled steel sheeting with rib perpendicular to steel beam. A large number of experimental studies on the behavior of stud shear connectors and reported in the literature are also summarized. A comparison of the stud shear resistance prediction using six reference codes (AISC, AASHTO, Eurocode-4, GB50017, JSCE and AS2327.1) and other procedures reported in the literature against experimental results is presented. From this exercise, it is concluded that there are still inaccuracies in the prediction of stud shear resistance in all analysed procedures and that improvements are needed.

• Steel and Composite Structures
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• v.51 no.1
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• pp.9-24
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• 2024

In order to study the shear mechanical behavior of prefabricated and assembled multi-key group stud connectors, this paper conducted push-out tests on 10 prefabricated and assembled multi-key group stud connectors, distributed in 5 groups, and detailed the failure modes of each specimen. Based on the finite element software, a total of 22 models of this type of stud connector are established, and validated the finite element models using the push-out tests. Furthermore, the effects of stud diameter, number of key groups, and spacing of key groups on the shear resistance of prefabricated and assembled multi-key group stud connectors are analyzed. Combined with the test and finite element, the force analysis is carried out for the stud and first-pouring and post-pouring concrete. The results show that the spacing and number of key groups have a significant impact on the shear capacity and shear stiffness of the specimen. For a single stud, the shear force is transferred to the surrounding concrete via the stud's root. When the stud is finally cut, the steel and the concrete plate are separated. Under vertical shear force, the top row of studs experiences the highest shear, while the middle row has the least. Based on statistical regression, a formula of assembled multi-key group stud connectors is proposed.

• Advances in concrete construction
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• v.9 no.4
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• pp.413-421
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• 2020

For steel-concrete girders made composite using shear studs, initial damage on studs induced by weld defect, unexpected overloading, fatigue and others might degrade the service performance and even threaten the structural safety. This paper conducted a numerical study to investigate the static behavior of damaged stud shear connectors that were embedded in ultra high performance concrete (UHPC). Parameters included damage degree and damage location. The material nonlinear behavior was characterized by multi-linear stress-strain relationship and damage plasticity model. The results indicated that the shear strength was not sensitive to the damage degree when the damage occurred at 2/3d (d is the stud diameter) from the stud root. An increased stud area would be engaged in resisting shear force as the distance of damage location from stud root increased and the failure section becomes inclined, resulting in a less reduction in the shear strength and shear stiffness. The reduction factor was proposed to consider the degradation of the shear strength of the damaged stud. The reduction factor can be calculated using two approaches: a linear relationship and a square relationship with the damage degree corresponding to the shear strength dominated by the section area and the nominal diameter of the damaged stud. It was found that the proposed method is preferred to predict the shear strength of a stud with initial damage.

• Steel and Composite Structures
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• v.47 no.6
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• pp.729-741
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• 2023

As the most popular shear connection in composite structures, mature concrete has been widely investigated by considering mechanical properties of stud connectors (SCs) embedded. To further enhance the fabrication efficiency of composite structures and solve the contradiction between construction progress and structural performance, it is required to analyze the shear performance of stud connections of composite structures with different concrete ages. 18 typical vertical push-out tests were carried out on stud shear connectors at concrete ages of 7 days, 14 days, and 28 days. Also, the effects of concrete age, stud spacing and stud diameter on the shear capacity, connection stiffness and failure mode of the connectors were studied. A new relationship expression of load-slip for SCs with various concrete ages was proposed. The existing design code for the SCs shear strength was evaluated according to the experimental data, and a more practical prediction equation for the shear capacity of SCs with different concrete ages was established. A great agreement was observed between the experimental and theoretical results, which can provide a reference for engineering practices.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1369-1389
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• 2015

In order to investigate the behaviour of lying multi-stud connectors in cable-pylon anchorage zone, twenty-four push-out tests are carried out with different stud numbers and diameters. The effect of concrete block width and tensile force on shear strength is investigated using the developed and verified finite element model. The results show that the shear strength of the lying multi-stud connectors is reduced in comparison with the lying single-stud connector. The reduction increases with the increasing of the number of studs in the vertical direction. The influence of the stud number on the strength reduction of the lying multi-stud connectors is decreased under combined shear and tension loads compared with under pure shear. Yet, due to multi-stud effect, they still can't be ignored. The concrete block width has a non-negligible effect on the shear strength of the lying multi-stud connectors and therefore should be chosen properly when designing push-out specimens. No obvious difference is observed between the strength reductions of the studs with 22 mm and 25 mm diameters. The shear strengths obtained from the tests are compared with those predicted by AASHTO LRFD and Eurocode 4. Eurocode 4 generally gives conservative predictions of the shear strength, while AASHTO LRFD overestimates the shear strength. In addition, the lying multi-stud connectors with the diameters of 22 m and 25 mm both exhibit adequate ductility according to Eurocode 4. An expression of load-slip curve is proposed for the lying multi-stud connectors and shows good agreement with the test results.

• Steel and Composite Structures
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• v.26 no.6
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• pp.759-769
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• 2018

This paper studies shear and tensile behaviors of headed stud connectors in double skin composite (DSC) structure. Firstly, 11 push-out tests and 11 tensile tests were performed to investigate the ultimate shear and tensile behaviors of headed stud in DSC shear wall, respectively. The main parameters investigated in this test program were height and layout of headed stud connectors. The test results reported the representative failure modes of headed studs in DSC structures subjected to shear and tension. The shear-slip and tension-elongation behaviors of headed studs in DSC structures were also reported. Influences of different parameters on these shear-slip and tension-elongation behaviors of headed studs were discussed and analyzed. Analytical models were also developed to predict the ultimate shear and tensile resistances of headed stud connectors in DSC shear walls. The developed analytical model incorporated the influence of the dense layout of headed studs in DSC shear walls. The validations of analytical predictions against 22 test results confirmed the accuracy of developed analytical models.

• Steel and Composite Structures
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• v.35 no.4
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• pp.475-494
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• 2020

Presented are experimental results from 24 full-scale push test specimens to study the behaviour of composite beams with trapezoidal profiled sheeting laid transverse to the beam axis. The tests use a single-sided horizontal push test setup and are divided into two series. First series contained shear loading only and the second had normal load besides shear load. Four parameters are studied: the effect of wire mesh position and number of its layers, placing a reinforcing bar at the bottom flange of the deck, normal load and its position, and shear stud layout. The results indicate that positioning mesh on top of the deck flange or 30 mm from top of the concrete slab does not affect the stud's strength and ductility. Thus, existing industry practice of locating the mesh at a nominal cover from top of the concrete slab and Eurocode 4 requirement of placing mesh 30 mm below the stud's head are both acceptable. Double mesh layer resulted in 17% increase in stud strength for push tests with single stud per rib. Placing a T16 bar at the bottom of the deck rib did not affect shear stud behaviour. The normal load resulted in 40% and 23% increase in stud strength for single and double studs per rib. Use of studs only in the middle three ribs out of five increased the strength by 23% compared to the layout with studs in first four ribs. Eurocode 4 and Johnson and Yuan equations predicted well the stud strength for single stud/rib tests without normal load, with estimations within 10% of the characteristic experimental load. These equations highly under-estimated the stud capacity, by about 40-50%, for tests with normal load. AISC 360-16 generally over-estimated the stud capacity, except for single stud/rib push tests with normal load. Nellinger equations precisely predicted the stud resistance for push tests with normal load, with ratio of experimental over predicted load as 0.99 and coefficient of variation of about 8%. But, Nellinger method over-estimated the stud capacity by about 20% in push tests with single studs without normal load.

• Steel and Composite Structures
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• v.48 no.2
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• pp.131-143
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• 2023

The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.