• Steel and Composite Structures
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• v.28 no.4
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• pp.449-460
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• 2018

This paper reports the experimental results of three through bolt beam-column connections under pure shear forces using modified push-out tests. The investigated specimens include extended end-plates and six through-bolts connecting square concrete-filled steel tubular column (S-CFST) to steel beams. The main goal of this study is to investigate if and how the mechanical shear connectors, such as steel angles and stud bolts, contribute to the shear transfer mechanisms in the steel-concrete interface of the composite column. The contribution of shear studs and steel angles to improve the shear resistance of steel-concrete interface in through-bolt connections was investigated using tests. The results showed that their contribution is not significant when the beam-column connection is included in the push-out tests. The specimens failed by pure shear of the long bolts, and the ultimate load can be predicted using the shear resistance of the bolts under shear forces. The predicted values of load allowed obtaining a good agreement with the tests results.

• Steel and Composite Structures
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• v.42 no.3
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• pp.407-426
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• 2022

Superior to traditional welded studs, high strength friction-grip bolted shear connectors facilitate the assembling and demounting of the composite members, which maximizes the potential for efficiency in the construction and retrofitting of new and old structures respectively. Hence, it is necessary to investigate the structural properties of high strength friction-grip bolts used in steel concrete composite beams. By means of push-out tests, an experimental study was conducted on post-installed high strength friction-grip bolts, considering the effects of different bolt size, concrete strength, bolt tensile strength and bolt pretension. The test results showed that bolt shear fracture was the dominant failure mode of all specimens. Based on the load-slip curves, uplifting curves and bolt tensile force curves between the precast concrete slab and steel beam obtained by push-out tests, the anti-slip performance of steel-concrete interface and shear behavior of bolt shank were studied, including the quantitative analysis of anti-slip load, and anti-slip stiffness, frictional coefficient, shear stiffness of bolt shank and ultimate shear capacity. Meanwhile, the interfacial anti-slip stiffness and shear stiffness of bolt shank were defined reasonably. In addition, a total of 56 push-out finite element models verified by the experimental results were also developed, and used to conduct parametric analyses for investigating the shear behavior of high-strength bolted shear connectors in steel-concrete composite beams. Finally, on ground of the test results and finite element simulation analysis, a new design formula for predicting shear capacity was proposed by nonlinear fitting, considering the bolt diameter, concrete strength and bolt tensile strength. Comparison of the calculated value from proposed formula and test results given in the relevant references indicated that the proposed formulas can give a reasonable prediction.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.519-528
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• 2008

A simple steel-concrete composite deck is developed for preventing the lateral torsional buckling of girders that are under construction and for reducing the term of works using H-shaped rolled beams as bridge girders. A new type of shear connectors is also developed for the composite behavior between a simple steel-concrete composite deck and the rolled beams by the connecting conditions between the deck and the girders. One is a connector bolt that is lengthened and split or tightened with two nuts and the other is an I-shaped rolled beam welded on a steel plate with a number of holes punched through the web. In this study, to estimate the shear strength of those shear connectors the push-out tests are performed and the test results are compared with that of the previous studies and the codes. The result of the push-out tests of the connector bolts showed that the shear performance is similar to that of the stud connector and revealed that the equation for the shear strength in the Korean Specification of Highway Bridge overestimates the shear capacity of the connector bolt whose diameter is larger than 19mm. From the push-out tests of punched I-shaped rolled beams with varying welding amounts, with the small amount of welding, shear capacity is governed by the shear capacity of welding. On the other hand, shear capacity is governed by the size of the punched I-shaped rolled beams, regardless of the amount of welding.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.122-128
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• 2003

Rock bolts are widely used as a supplementary roof support system in hard-rock mining since a long time. Since the performance of fully grouted passive bolts depends on bond strength, in the present investigation extensive laboratory pull-out as well as push-out tests were conducted varying the bolt diameter, length and cement-water mixing ratios of grout. The load-displacement curves were developed and were verified with the numerical results obtained from finite element analysis using ALGOR software. Numerical models were validated for push-out tests and a detailed analysis was carried out to know the displacement, stress, strain distribution along the bolt.

• Steel and Composite Structures
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• v.2 no.1
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• pp.51-66
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• 2002

Perforated shear connectors currently used in composite steel and concrete structures are described and evaluated. Modifications of the perforated connector suitable for common use injavascript:confirm_mark('abe', '1'); civil and bridge engineering are proposed. The connectors were tested in laboratories of CTU Prague for shear load capacity. Push tests of connectors with 32 mm openings and with 60 mm openings, both in normal and lightweight concrete of different strength characteristics and with different transverse reinforcement, were carried out. The experimental study also dealt with the connector height and parallel arrangement of two connectors and their influence on shear resistance. While extensive tests with static loading were carried out, fatigue tests under repeated loading are still in progress. After statistical evaluation of the experimental results and comparisons with other available data the authors developed reasonable shear resistance formulas for all proposed arrangements.

• Steel and Composite Structures
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• v.9 no.3
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• pp.255-274
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• 2009

This paper presents an experimental study of a newly developed composite floor system, built up from thin-walled C-profiles and upper concrete deck. Trapezoidal sheeting provides the formwork and the fastening of the sheet transmits the shear forces between the C-profiles and the deck. The modified formation of the standard self-drilling screw in the beam-to-sheet connection is applied as shear connector. Push-out tests are completed to study the composite behaviour of the different connection arrangements. On the basis of the test results the behaviour is characterized by the observed failure modes. The design values of the connection stiffness and strength are calculated by the recommendation of Eurocode 4. In the next phase of the experimental study six full-scale composite beams are tested. The global geometry is based on the proposed geometry of the developed floor system. The applied shear connections are selected as the most efficient arrangements obtained from the push-out tests. The experimental behaviour of the composite beams are discussed and evaluated. As a conclusion of the experimental study the Eurocode 4 plastic design method is validated for the developed composite floor.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.101-109
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• 2016

PURPOSE. To investigate the void parameters within the resin cements used for fiber post cementation by micro-CT (${\mu}CT$) and regional push-out bonding strength. MATERIALS AND METHODS. Twenty-one, single and round shaped roots were enlarged with a low-speed drill following by endodontic treatment. The roots were divided into three groups (n=7) and fiber posts were cemented with Maxcem Elite, Multilink N and Superbond C&B resin cements. Specimens were scanned using ${\mu}CT$ scanner at resolution of $13.7{\mu}m$. The number, area, and volume of voids between dentin and post were evaluated. A method of analysis based on the post segmentation was used, and coronal, middle and apical thirds considered separately. After the ${\mu}CT$ analysis, roots were embedded in epoxy resin and sectioned into 2 mm thick slices (63 sections in total). Push-out testing was performed with universal testing device at 0.5 mm/min cross-head speed. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests (${\alpha}=.05$). RESULTS. Overall, significant differences between the resin cements and the post level were observed in the void number, area, and volume (P<.05). Super-Bond C&B showed the most void formation ($44.86{\pm}22.71$). Multilink N showed the least void surface ($3.51{\pm}2.24mm^2$) and volume ($0.01{\pm}0.01mm^3$). Regional push-out bond strength of the cements was not different (P>.05). CONCLUSION. ${\mu}CT$ proved to be a powerful non-destructive 3D analysis tool for visualizing the void parameters. Multilink N had the lowest void parameters. When efficiency of all cements was evaluated, direct relationship between the post region and push-out bonding strength was not observed.

• Steel and Composite Structures
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• v.10 no.4
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• pp.317-329
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• 2010

According to the results of 9 circular concrete filled steel tube (CFT) push-out tests, a new theoretical model for average bond stress versus free end slip curve is proposed. The relationship between verage bond stress and free end slip is obtained considering some varying influential parameters such as slenderness ratio and diameter-to-thickness ratio. Based on measured steel tube strain and relative slip at different longitudinal positions, the distribution of bond stress and relative slip along the length of steel tube is obtained. An equation for predicting the varying bond-slip relationship along longitudinal length and a position function reflecting the variation are proposed. The presented method can be used in the application of finite element method to analyze the behavior of CFT structures.

• Steel and Composite Structures
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• v.43 no.3
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• pp.311-325
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• 2022

For multi-story structural systems, Korean steel industry has fostered development of a steel-concrete composite beam. Configuration of the composite beam is characterized by steel angle shear connectors welded to a U-shaped cold formed-steel beam. Effects of shear connector orientation and spacing were studied to evaluate current application of the angle shear connector design equation in AC495. For the study, interfacial shear resistance behavior was investigated by conducting 24 push-out tests and attuned using unreinforced push-out specimens. Interfacial shear to horizontal slip response was reported along with corresponding failure patterns. Pure shear connector strength was also evaluated by excluding concrete shear contribution, which was estimated in relation to steel beam-slab interface separation or interfacial crack width.

• 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.