As mentioned above, information on the strength of SCS sandwich shells (or curved SCS sandwich plates) are quite limited. In order to achieve full composite action at the interface of the steel and concrete, mechanical connectors are used. The newly developed ULCC is chosen as the core material to achieve a lightweight structure. So far, structural behaviors of SCS sandwich structures with new mixture-ULCC have not been investigated. Moreover, the shear and tensile strengths of the proposed J-hook connector have not been systematically studied. The structural performances of the SCS sandwich composite structure with the mechanical shear connectors and ULCC should be studied for the flat panels. The relationship among the strength of the structure and strength of the connectors were shown in Fig. 1.5. The research objectives are listed below:
1) To carry out feasibility study on mechanical connectors for the SCS sandwich shell structures and to recommend suitable connectors for curved sandwich structure.
2) To systematically study the shear and tensile strength of the J-hook connectors embedded in different concrete mixtures including NWC, LWC and ULCC; to obtain the strengths of the J-hook connectors subjected to shear, tension and combined shear and tension loads. To develop design formulae on prediction of these strengths.
3) To experimentally investigate the ultimate strength behavior of the proposed
‐ 7 - sandwich beams with the newly developed mixture ULCC. To develop FE and analytical models to predict the strength of these SCS sandwich beams with the mechanical connectors and ULCC.
4) To carry out experimental study on the SCS sandwich shells with mechanical connectors and ULCC. These experimental studies are set to investigate the structural performances of sandwich shells under patch loading.
5) To develop analytical methods to predict the punching shear strength of the SCS sandwich shell structures with mechanical connectors and ULCC.
To achieve the above objectives, the research scopes are as follows:
1) In order to find the suitable shear connectors to be used in the SCS sandwich shell structure, several types of novel shear connectors were developed and proposed. The performances of the selected connectors were investigated through the tests on the prototype SCS sandwich composite beams with them. Through the comparative studies, recommendations on the most suitable connectors are made for the further research.
2) To investigate the shear strength, tension capacity and strength of the J-hook connectors under combined shear and tension forces of the proposed J-hook shear connectors, a series of push-out tests, tension tests and finite element analysis are conducted, respectively. Parametric studies are carried out to investigate the influences of different variables on the shear and tension capacity. All these test programs are focused on the strength of the J-hook connectors embedded in different concrete mixtures especially in the ULCC.
3) Ultimate strength of SCS sandwich beams with the ULCC is also one of the research scopes. Structural behaviors of the SCS sandwich beams with ULCC are investigated
‐ 8 - through a series of three-point or four-point bending tests. The tests are also carried out to investigate the influences of different parameters on the strength of sandwich beams. Analytical models are proposed and compared with finite element (FE) method to predict the strength of SCS sandwich beams. The experimental results are used to verify the developed analytical model and FE model.
4) Finally, the ultimate strength behavior of SCS sandwich composite shell is investigated. A two-phase experimental programme is carried out to investigate the structural behavior of the SCS sandwich shells under concentrated loading. In the test program, the bond enhancement by the connector, thickness of the steel shell, strength of the concrete, spacing of the connectors, curvature of the shell are considered. The tests focus on the strength of the shell under point load.
Experimental results are used to verify the analytical method to predict the strength of the SCS sandwich shell.
The research work reported in this thesis aims to fill the missing information on SCS sandwich composite shell structures with shear connectors. Design guidelines are proposed to predict the strength of the SCS sandwich composite shell structure under local concentrated loading. The developed design guides to calculate the strengths of J- hook connectors will supplement the existing design approaches on the shear connectors used in SCS sandwich composite structure. Nevertheless, this developed design guides enlarge the application scopes of the formulae for connectors embedded in more types of core concrete. Therefore, these researches clear the obstacles of applying the SCS sandwich composite structure with the J-hook connectors. The ultimate strength behaviors of the SCS sandwich composite beams with mechanical shear connectors and new core material ULCC will be investigated through the test on these sandwich beams.
‐ 9 - The design approaches are hopefully developed for the SCS sandwich composite beams with mechanical shear connectors and ULCC. Finite element model will also be developed to analyze the structural performances of the SCS sandwich beams with the J- hook connectors and ULCC.