Strength Of Studs Research Articles

Mechanical performance of shear studs and application in steel-concrete composite beams

This work experimentally investigates the effects of shear stud characteristics on the interface slippage of steel-concrete composite push-out specimens. ABAQUS is used to establish a detailed 3D finite element (FE) model and analyze the behavior of push-out specimens. The modeling results are in good agreement with the experimental results. Based on parametrical analysis using the validated FE approaches, the effects of important design parameters, such as the diameter, number, length to diameter ratio, and yield strength of studs, concrete strength and steel transverse reinforcement ratio, on the load-slip relationship at the interface of composite beams are discussed. In addition, a simplified approach to model studs is developed using virtual springs with an equivalent stiffness. This approach is demonstrated to be able to predict the load-displacement response and ultimate bearing capacity of steel-concrete composite beams. The predicted results show satisfactory agreement with experimental results from the literature.

Shear force of headed shear studs, high-strength shear studs and steel plate embedded in concrete: an experimental study

Diverse shear studs and steel plate are frequently installed within engineering structures to increase resistance of external shear force at steel frame and reinforced concrete joints. In the current study, tests were undertaken in order to compare both variable shear stud strength (normal-strength shear studs and high-strength shear studs) and type (normal shear studs and headed shear studs) with steel plate. Results have been evaluated in the context of experimental data, finite element analyses results and the current ACI318-11 code.

Experimental and numerical study of end anchorage in composite slabs

Composite steel-concrete slabs are widely used in floor construction in steel-framed buildings where the connection between the steel beam and the concrete slab through shear connectors exploits the best combination of each component. The end anchorages in combination with other shear transfer mechanisms play an important role into the strength, stiffness and ductility of composite slabs. In this paper, a series of tests were carried out on both solid and profiled composite slabs to investigate the effect of end anchorage on the ultimate load carrying capacities and failure modes. The test programme consisted of eight composite slab specimens under restrained and unrestrained conditions. The load-deflection relationships and failure modes of all slabs are presented. The test results showed that end anchorage has a positive effect on the ultimate strength of both solid and composite slabs irrespective of the long term loading conditions. A three-dimensional finite element model is developed to simulate the behaviour of composite slabs with end anchorages. The model was validated against experimental results for its accuracy and a parametric study was conducted to investigate the influence of concrete strength, shear stud strength and profiled steel sheeting thickness in profiled composite slabs. The results showed that the effect of concrete strength and sheeting thickness on the load-deflection behaviour is significant. However, the shear bond stress-slip rather than the strength of the shear studs governs the contribution of the end anchorage to the shear bond capacity of composite slabs.

Strength of composite slabs with end anchorages. Part II: Parametric studies

Results of parametric studies on steel-deck-reinforced composite slabs with end anchorages provided by welded shear stud connectors are presented. The studies are based on the analytical model described in the companion paper. Effects of the number of studs, longitudinal shear strength, deck height, steel thickness, deck yield strength, concrete cover depth, concrete compressive strength, and deck span conditions on strength of the composite slabs and the stud strength mobilization were investigated. Simplified formulas for the determination of the minimum number of welded shear studs required to achieve the full moment of the section were developed. The formulas account for deck height, slab depth, concrete cover depth, steel thickness, steel yield strength, longitudinal shear strength, and slab span length, and predict the required number of studs with reasonable accuracy.

Parametric push-out analysis on group studs shear connector under effect of bending-induced concrete cracks

Arranging shear studs in group is known for the constructional and economical advantages in steel and concrete composite structures. Nowadays, many composite bridges are constructed with wide transverse concrete cantilevers and web spacing, leaving resulted transverse bending-induced residual tensile concrete cracks. Its effect on group studs has not been fully clear. In this case, a parametric push-out FEM analysis with damage plasticity models has been executed. It concerned the mechanical performance of group studs under effect of bending-induced concrete cracks. In this study, bending-induced concrete cracks, concrete compressive strength, stud dimension were the parameters. It mainly showed that bending-induced concrete cracks caused stud shear stiffness reduction since the shear load transfer from stud to concrete during push process had been unfavorably affected by these cracks. Furthermore, the relationship between bending-induced concrete cracks and stud shear stiffness reduction has been described by equation from regressing the analysis results. Together with the proposed simplified analytical method of evaluating concrete crack depth, the study provided a possible way for engineering design and maintenance dealing with bending-induced concrete crack effect on stud shear connector. Finally, stud strength comparison between FEM results and evaluations based on several specifications indicated that engineers should pay attention to the effect of bending-induced concrete cracks.

친환경시멘트 콘크리트를 사용한 강판콘크리트구조의 압축거동

강판콘크리트(SC)구조에 관한 국내의 연구는 내력을 많이 요구하는 원전건물을 중심으로 연구가 진행되었다. 또한 SC구조는 공장생산과 모듈화시공을 통한 공기단축이 가능한 장점을 가지고 있다. 본 연구에서는 중 저층의 일반건물에서 낮은 강도로 사용 할 수 있는 SC구조의 토대를 마련하고자 하였다. 강도를 저감시키는 방법으로 친환경재료인 황토와 시멘트를 조합하여 중요도가 낮은 건물에 사용이 가능하도록 하였다. 본 연구에서는 중심압축하중을 받는 기둥부재를 대상으로 압축거동, 유효길이계수, 좌굴하중, 강판좌굴 및 스터드의 성능을 검증하였다. The domestic research of the steel plate concrete structures have been focused on the nuclear structures requiring much strong resistance. There are many advantages in the steel plate-concrete structures such as the possibility of prefabricated production and modular construction. This research tried to establish some basic design information of SC structures toward mid to low-rise general buildings with low strength. To reduce the strength mentioned, the some of the cement in weight was replaced by the soils which are traditional and environmental oriented material where the new system can be used to general buildings. This paper studied on the compressive characteristics, effective length factors, buckling loading, steel plate buckling, and stud strength using the compression member subjected to the concentrated compression loadings.

SFRCCと密に配置した鋼製スタッドによる接合の耐力評価

A series of push-out tests are conducted to propose shear connectors in steel-concrete composite construction that uses newly developed steel fiber reinforced cement composites (SFRCC). The tests are conducted with the pitch length (Dp) and gauge length (Dg) as the major test parameters. It is found that (1) the studs arranged densely with a pitch length of 3.5 times the stud diameter (d) can possess the shear strength (per stud) not smaller than 85% of the shear strength of a single stud; (2) the group effect caused by stud spacing in gauge direction remains the same when Dg/d changed from 0.46 to 0.23. Even the studs are arranged in a gauge spacing of the minimum spacing for stud installation, no significant reduction on per stud strength is observed; and (3) when studs are closely arranged in an area with the minimum stud spacing (7.5d×5d) stipulated in current design codes, the per stud strength decreases as the studs spacing especially that in the pitch direction decreases, but the total maximum shear resistance of the connection is still significantly larger than that with normal studs spacing.

Studies of the lifetime of cyclically loaded steel-concrete composite bridges

In current German and international standards for composite structures of steel and concrete, the determination of the ultimate load capacity and the fatigue life of headed shear studs is carried out with separate and independent verifications at the ultimate, serviceability and fatigue limit states. The fatigue resistance is verified in a similar way to steel structures, based on a nominal stresses concept and linear damage accumulation according to Palmgren-Miner. The effect of pre-damage due to fatigue loading at both the ultimate and serviceability limit states is not considered. Because cyclic loading of headed shear studs leads to a decrease in the static strength of stud connectors, the assumptions for independent limit states are not given and the reliability index of steel-concrete composite structures subjected to fatigue loading may fall below the target values in codes. This paper deals with the results of a comprehensive programme of experimental work with more than 90 standard EC4 push-out test specimens and two full-scale beam tests which consider the crack propagation through the stud foot and the local damage to the concrete surrounding the studs as relevant consequences of highcycle loading. Based on the results of the push-out tests, new design methods were developed to predict the fatigue life and the residual strength of headed shear studs after high-cycle loading. Considering the interaction between the local damage and the behaviour of the global structure, these research results were taken as the basis for simulating the cyclic behaviour of composite beams by means of a damage accumulation method.

Outrigger Beam–Wall Connections. II: Subassembly Testing and Further Modeling Enhancements

Adequate strength of headed studs under cyclic loads is a prerequisite for satisfactory performance of outrigger beam–core wall connections that commonly use multiple headed studs. Previous studies have typically not investigated the effects of reinforcement around studs, and have not accounted for the effects of cracking, damage, and yielding of reinforcement on the strength of studs. To remedy these deficiencies, two 1/4-scale subassemblies that contain a cantilever wall and two outrigger beams with and without floor diaphragms were subjected to cyclic loading. The wall reinforcement around the connection was selected according to the anticipated level of cracking and plastic hinge formation. The design methodology followed in this research resulted in connections that could develop and exceed the design forces despite extensive cracking and yielding of wall reinforcement around the headed studs. The presence of heavily confined wall boundary elements around headed studs increases the capacity. Simple methods to account for the influence of cracks and strengthening effects of boundary elements were developed. The resulting analytical model was able to accurately establish the expected mode of failure and capacity of outrigger beam–wall connections. For the outrigger beam–wall connection detail selected, the outrigger beam was found to transfer the majority of diaphragm forces directly to the core wall with negligible participation by the floor. Therefore, floor slab–wall connections can be based on simple details that resist only gravity loads unless the connections are specifically designed to transfer the diaphragm forces to the wall.

Cyclic shear force–slip behavior of studs under alternating and pulsating load condition

The objective of this study is to investigate the maximum strength and the fatigue strength of studs subjected to the alternating load as well as the pulsating load. First, in order to conduct a series of static and fatigue test of studs under both the load conditions, we devise a new specimen to which the alternating shear force can be applied easily by general fatigue testing machines. Employing the devised specimens, the shear force–slip behavior, the maximum strength and the fatigue strength of studs under the alternating load condition are investigated and are compared with those under the pulsating load condition.

Push-out tests on studs in high strength and normal strength concrete

Some test results from push-out tests of studs in normal and high strength concrete are presented. It is found that the concrete compressive strength significantly affects the strength of the stud connections. Increase of the transverse reinforcement in the concrete slabs has a negligible effect when high strength concrete is used and some effect when normal concrete is used. The present design code is not adequate to estimate the shear strength of studs embedded in high strength concrete and it is suggested that a design formula that takes account of the interaction between the studs and the surrounding concrete should be used.

Behaviour of headed studs in composite beams: push-out tests

This paper briefly summarizes the results of tests conducted on 18 full-size push-out specimens and 4 pull-out specimens. The objective of the project was to study the behaviour of headed studs in composite beams with ribbed metal decks perpendicular and parallel to the steel beam. The longitudinal spacing of the headed studs and the rib geometry of the metal decks were the principal experimental parameters.Five of the push-out specimens had solid concrete slabs, in five specimens the ribbed metal deck was placed parallel to the steel beam, and in the remaining eight specimens the metal deck was perpendicular to the steel beam. In most cases 38 mm deck and 16 × 76 studs were used.Test results obtained by the authors appear to indicate that with some exceptions the current Canadian Standards Association and Load and Resistance Factor Design codes are able to predict stud strength correctly for specimens with solid slabs and with parallel ribbed slabs only when failure occurs owing to stud shearing, i.e., when the studs are spaced sufficiently apart. It is recommended that these codes include a provision to check the possibility of concrete-related failures when the longitudinal stud spacing approaches or falls below six times the stud diameter for solid and parallel ribbed slabs.Stud pull-out was the principal mode of failure in the specimens with perpendicular ribbed metal decks. An equation recently proposed by Hawkins and Mitchell appears to underestimate the capacity for specimens with 38 mm deck. For specimens with 76 mm deck, their equation overestimates the stud capacity. The authors have proposed two separate but similar empirical equations for specimens with 38 and 76 mm deck. Key words: composite beam, headed stud, stud shear capacity, stud pull-out failure, minimum stud spacing, perpendicular deck, parallel deck.

EFFECT OF DIRECTIONS OF CONCRETE PLACING ON BEHAVIOR OF HEADED STUD SHEAR CONNECTORS IN PUSH-OUT TESTS

Headed studs are exclusively used as shear connectors in various steel-concrete composite constructions. The directions of concrete placing in relation to stud connectors in fabrication of composite constructions influence static and fatigue strength of studs and the composite action between steel and concrete. They can be classified to four cases. In most of the past studies, however, the effect of directions of concrete placing have not been sufficiently given consideration except the one by J. W. Fisher. The present paper discusses the effects based on the results obtained by push-out type test series and proposes design formulas for static and fatigue strength of stud shear connectors.

The strength of stud shear connectors at low temperatures

The effect of temperature on the ultimate strength of shear connections consisting of headed stud shear connectors embedded in a normal weight concrete slab is examined by means of pushout tests conducted at temperatures of +20, −10, and −20 °C. The strength of the shear connection with 13 mm diameter studs was found to be lower at −20 °C than at room temperature, whereas the strength of the shear connection with 19 mm diameter studs was found to be greater at −20 °C than at room temperature. This is explained in terms of increased concrete strength and reduced stud strength with decreased temperature, causing a change in the mode of failure. Keywords: composite construction, shear strength, shear connection, stud shear connectors, low temperature pushout tests.