| Author: | Shen, Minhui |
| Title: | Structural behaviour of shear connection in composite structures under complex loading conditions |
| Degree: | Ph.D. |
| Year: | 2013 |
| Subject: | Concrete slabs -- Testing Bolts and nuts -- Testing Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xix, 360 p. : ill. ; 30 cm. |
| Language: | English |
| Abstract: | This research project aims to examine the structural behaviour of stud shear connections with both solid concrete slabs and composite slabs using local concrete aggregates through the use of standard and modified push-out tests. A total of 20 push-out tests are carried out to provide the test data of typical stud shear connections for practical design in Hong Kong. It should be noted that modified push-out tests are proposed in which the stud shear connections are subjected to co-existing shear and tension forces. Moreover, advanced finite element models using ABAQUS have also been established and calibrated carefully against the test data. Therefore, these models are able to predict the nonlinear load-slippage characteristics of the stud shear connections. Furthermore, a comprehensive parametric study is carried out using various material properties of the concrete and the headed shear studs with welding collars, and various geometrical dimensions of the profiled steel decking. The shear resistances are tabulated for the practical design of the composite structures in Hong Kong. Experimental Investigation: A total of 20 push-out tests on various stud shear connections have been carried out to examine their deformation characteristics, and Figure I illustrates the configurations of the specimens. These push-out tests are divided into the following four series: a) Test Series SS are standard push-out tests with concrete solid slabs which are conducted according to the recommended procedures in EN 1994-1-1. All the stud shear connections are under simple shear forces. b) Test Series SC are standard push-out tests with composite slabs. The configurations of these test specimens are similar to those in Series SS, except that the trapezoidal profiled steel deckings are used. c) Test Series MS are modified push-out tests in which the steel-concrete interfaces are inclined 15{493} from the vertical. They are devised in such a way that the stud shear connections are under co-existing shear and tension forces under vertically applied loads. d) Test Series MC are modified push-out tests with composite slabs. The configurations of these test specimens are similar to those in Series MS, except that the trapezoidal profiled steel deckings are used. Key test results of the experimental investigation include the load-slippage curves and the failure modes of various stud shear connections. The shear resistances of all stud shear connections are normalized to a concrete cube strength, fcu, at 35 N/mm2 for direct comparison. The reduction factors in the shear resistances, which are brought on by the presence of the profiled steel decking as well as the effect of the co-existing shear and tension forces, are also obtained from the experiment. Numerical Investigation: Four advanced finite element models have been established with the finite element package ABAQUS. Dynamic explicit analysis is used for the highly non-linear analyses to prevent both the global mass and the global stiffness matrices that result from the extensive forming and inverting during the computation. Therefore, each increment becomes relatively efficient when they are compared to the conventional implicit analysis method. Figure II presents the finite element models of Series SS, Series SC, Series MS, and Series MC. All these models have been calibrated carefully against the test data using the measured geometrical dimensions and mechanical properties of the test specimens as well as measured deformation characteristics of the stud shear connections. It should be noted that both the welding collars of the shear studs and the stiffening folds at the middle of the troughs of the deckings have been carefully incorporated into the models based on measured geometrical dimensions and mechanical properties. Moreover, a comprehensive numerical investigation into various failure modes, such as shear stud yielding and concrete crushing and cracking, are successfully identified in the finite element modeling. These failure modes are found to be consistent with those that are identified from the experimental investigations. A comprehensive parametric study is conducted based on the four finite element models. The parameters include the compressive strengths of the concrete, the dimensions and tensile strengths of the headed shear studs with welding collars, and the geometrical dimensions of the profiled steel deckings with stiffening folds. The shear resistances of the practical stud shear connections with various geometrical dimensions and mechanical properties have been obtained and are then tabulated for the practical design of the composite structures. Key Findings and Significance of the Project: Experimental Investigation: Based on the test results of the standard push-out tests, the shear resistances of the stud shear connections in both solid concrete and composite slabs are found to be larger than the design values which are determined in accordance with the current Hong Kong Steel Code with 1.0 partial safety factors, although the Young{174}s modulus of the local aggregates is only 70% to 80% of the values in EC2. Moreover, the presence of tension forces in the stud shear connections is found to reduce the shear resistances of the shear resistances of the stud shear connections from 0.9 to 0.76. Hence, it is important to incorporate the effect of co-existing shear and tension forces in the stud shear connections in design. Numerical Investigation: After carefully calibrating them against the test data, the cross-sectional geometry and dimensions of the profiled steel are found to produce considerable effects on the structural behaviour of the stud shear connections, particularly on the stiffening folds and their heights in the troughs of the profiled steel decking. Moreover, the welding collars at the shank roots of the headed shear studs must be accurately incorporated into the design. The concrete crushing and cracking, as well as the dowel mechanism of the stud shear connections, have also been studied systematically, to obtain the structural behaviours of the stud shear connections in terms of load-slippage curves, yielding of headed shear studs, concrete crushing and cracking, and the internal force and moment distributions within the headed shear studs. These findings provide deeper understanding on the structural behaviour of the stud shear connections under simple shear force and co-existing shear and tension forces. Design data: The design data on the shear resistances of stud shear connections with practical material specifications and geometrical dimensions are obtained based on the test results and numerical data from the experimental and numerical investigations. The design data are readily adopted into the local code of practice of steel and concrete structure design by incorporating the mechanical properties of local concrete. Project Significance: The research project provides important test data on the structural behaviour of stud shear connections with solid concrete and composite slabs under co-existing shear and tension forces, particularly the load-slippage curves with the shear resistances and the slippage capacities. These data allow the shear resistances of stud shear connections in solid concrete slabs to be directly compared with those of the stud shear connections in composite slabs, as well as to directly compare the stud shear connections under shear forces with the stud shear connections under combined shear and tension forces. These data may be used as a definitive reference for both practical design application and calibration of the finite element models. Moreover, after carefully calibrating the advanced finite element models, their capability to simulate all typical failure modes of the stud shear connections that are identified from the experimental investigation is demonstrated. Various concrete compression and tensile responses are plotted to illustrate the distinctive local crushing and cracking patterns in the different parts of the concrete slabs. The small geometrical dimensions in the stud shear connections, such as the height of the stiffening folds in the troughs of the profiled steel deckings and the height of the welding collars at the shank roots of the headed shear studs, are shown to be crucial in order to accurately model the stud shear connections. Therefore, these geometrical dimensions must be clearly specified in the design as they considerably affect the structural behaviour of the stud shear connections. Through its experimental and numerical investigations, this research project contributes by developing our understanding of the structural behaviour of stud shear connections with solid concrete and composite slabs under co-existing shear and tension forces. Moreover, this research project provides the design data on the shear resistances of stud shear connections with typical material specifications and geometrical dimensions to facilitate the practical design of steel-concrete composite structures in Hong Kong. |
| Rights: | All rights reserved |
| Access: | open access |
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| File | Description | Size | Format | |
|---|---|---|---|---|
| b26818048.pdf | For All Users | 10.77 MB | Adobe PDF | View/Open |
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