Principal Tensile Direction Research Articles

Behaviors of steel-plate and concrete in steel-concrete-steel panels subjected to biaxial tension-compression

With the increasing application of steel–concrete-steel (SCS) composite structures in engineering constructions, the mechanical behaviors of steel plates and concrete in SCS structures are becoming increasingly important. This study aimed to evaluate the individual smeared behaviors of the steel plate and concrete from some tested SCS panels and analyze the main characteristics of the plates and concrete. An incremental step analysis method was used to analyze prior experimental research, in which seven SCS panels were subjected to proportional biaxial tension–compression loading. This method is based on Navier’s three principles (stress equilibrium, strain compatibility, and the constitutive laws of materials). Using this method, the smeared behaviors of the steel plates and concrete were evaluated. Through analysis, it was found that these smeared behaviors exhibit the following characteristics: When plastic flow occurs, the smeared stress state of steel plates flows on the yield surface after yielding, which results in an increasing principal tensile stress and a decreasing principal compressive stress. For the concrete in the principal compressive direction of the SCS panels, confinement and softening effects may coexist. The concrete in the principal tensile direction of the SCS panels exhibits two different behaviors, and an unexpected compressive stress may be generated. These findings will provide a clearer understanding of the mechanical behaviors of concrete and steel plates in SCS panels in future research.

Concrete behavior in steel-concrete-steel panels subjected to biaxial tension compression

Steel-Concrete-Steel (SCS) composite wall is being used for different purposes for its improved performances. Some analytical and finite element models have been presented in the past to predict the behavior of such walls. In this paper, an attempt is made to develop an iterative membrane model to analyze SCS wall panels subjected to in-plane membrane forces in the principal directions. The model accounts for the post-cracking Poisson effects of concrete as the Zhu/Hsu ratio.Individual behaviors of concrete and steel plates in an SCS panel are studied in which confinement in principal tensile direction accompanied by negative uniaxial tensile strain in concrete is observed. To explain this behavior, a detailed perspective for uniaxial strain in principal tensile direction is proposed and the conventional stress-strain trajectory of concrete in tension is extended to incorporate any confinement developed in the concrete. Constitutive law of concrete in compression is also modified to incorporate the observed confining behavior of the concrete.

Debonding failure and size effects in micro-reinforced composites

Failure in micro-reinforced composites is investigated numerically using the strain-gradient plasticity theory of Gudmundson [Gudmundson, P., 2004. A unified treatment of strain gradient plasticity. Journal of the Mechanics and Physics of Solids 52 (6) 1379–1406] in a plane strain visco-plastic formulation. Bi-axially loaded unit cells are used and failure is modeled using a cohesive zone at the reinforcement interface. During debonding a sudden stress drop in the overall average stress–strain response is observed. Adaptive higher-order boundary conditions are imposed at the reinforcement interface for realistically modeling the restrictions on moving dislocations as debonding occurs. It is found that the influence of the imposed higher-order boundary conditions at the interface is minor. If strain-gradient effects are accounted for a void with a smooth shape develops at the reinforcement interface while a smaller void having a sharp tip nucleates if strain-gradient effects are excluded. Using orthogonalization of the plastic strain gradient with three corresponding material length scales it is found that, the first length scale dominates the evaluated overall average stress–strain response, the second one only has a small effect and the third one has an intermediate effect. Finally, studies of reinforcement having elliptical cross-sections show rather significant gradients of stress which is not seen for the corresponding circular cross-sections. Also, an increased drop in the overall load carrying capacity is observed for cross-sections elongated perpendicular to the principal tensile direction compared to the corresponding circular cross-sections.