• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.499-507
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• 2003

As the load is increased on the steel-concrete composite structure, its interface begins to show nonlinear behavior due to the reduction of interaction, micro-crack, slip and separation, and it causes slip-softening, Therefore, it is essential to consider the partial-interaction analysis technique. Until now, however, full-interaction or, in some instances, the linear-elastic model, which are insufficient to simulate accurate behavior, are assumed in the analysis of composite structure since the analysis method and nonlinear model for interface are very difficult and complicated. Therefore, the design of composite structure is followed by the experimental method which is inefficient-because a number of tests have to be carried out according to the design environments. In this study, we carried out the nonlinear analysis according to various interface nonlinear models by interaction magnitude, and analyzed more accurate structural behavior and performance by maximum tangential traction and slip-softening at the interface. As a result of this study. we were able to prove that the nonlinear model of interface more exactly represents behavior after yielding, such as ultimate load: that initial tangential stiffness of interface has a significant effect on the yielding load of structural members or part: and that the maximum tangential traction and slip-softening mainly effects structural yielding and ultimate load. Therefore, the structural performance of composite structure is highly dependent on the steel-concrete interface or interaction, which may result in initial tangential stiffness, maximum tangential traction and slip-softening in nonlinear model.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.249-263
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• 2017

The expansion behavior of inflatable steel pipe rockbolt shows geometric nonlinearity due to its ${\Omega}-shaped$ section. Previous studies on the anchoring behavior of inflatable steel pipe rockbolt were mainly performed using theoretical method. However, those studies oversimplified the actual behavior by assuming isotropic expansion of inflatable steel pipe rockbolt. In this study, the anchoring behavior of the inflatable steel pipe rockbolt were investigated by the numerical method considering the irregularity of pipe expansion and other influencing factors. The expansion of inflatable steel pipe rockbolt, the contact stress distribution and the change of the average contact stress and the contact area during installation were analyzed. The contact stresses were developed differently depending on the constitutive behavior of rocks. Small contact stresses occurred in steel pipes installed in elasto-plastic rock compared to steel pipes installed in elastic rock. Also, the anchoring behaviors of the inflatable steel pipe rockbolt were different according to the stiffness of the rock. The steel pipe was completely unfolded in the case of the stiffness smaller than 0.5 GPa, but it was not fully unfolded in the case of the stiffness larger than 0.5 GPa for the given analysis condition. When the steel pipe is completely unfolded, the contact stress increases as the rock stiffness increases. However, the contact stress decreases as the rock stiffness increases when the steel pipe is not fully expanded.