Sung-Hwan Yun

Thermal-Structure Interaction Parallel Fire Analysis for Steel-Concrete Composite Structures under Bridge Exposed to Fire Loading

The objective of this research is to evaluate of global and local damage for steel-concrete composite structures under highway bridge exposed to fire loading. To enhance the accuracy and efficiency of the numerical analysis, the proposed transient nonlinear thermal structure interaction(TSI) parallel fire analysis method is implemented in ANSYS. To validate the TSI parallel fire analysis method, a comparison is made with the standard fire test results. The proposed TSI parallel fire analysis method is applied to fire damage analysis and performance evaluation for Buchen highway bridge. The result of analysis, temperature of low flange and web are exceed the critical temperature. The deflection and deformation state show good agreement with the fire accident of buchen highway bridge.

Behavior of Columns Due to Variation of Performance Influencing Factors Based on Performance Based Design

The performance evaluation of reinforcement concrete structure is carried out as a function of the following performance influencing factors: (1) the strength of concrete, (2) longitudinal reinforcement, (3) transverse reinforcement, (4) aspect ratio, and (5) axial force. With various values of the five parameters, eigenvalue analysis and non-linear static analysis were performed to investigate the structural yield displacement, yield basis shear force, and static performance of ductility ratio. In addition, the performance evaluation is carried out according to the modified capacity spectrum method (FEMA-440) using the results of non-linear static analysis, and the effect of each parameter on performance point is analyzed. Based on the result of eigenvalue analysis and non-linear static analysis indicates, that the natural period and the ductility ratio are affected more by the structural properties than the material properties. In case of the analysis of the criterion of performance points, the effect of section shape is one of the important factors together with natural period and ductility ratio.

Constitutive Model of Laterally Confined High Strength Concrete

Since existing constitutive models developed for confined normal strength concrete overestimate ductility when they are applied to confined high strength concrete, these models cannot be directly applied to confined high strength concrete. In an effort to solve this problem, an accurate stress-strain relationship of the hihg strength concrete needs to be formulated by examining the confinement effects due to increase of the concrete strength. In this study, a constitutive model is developed to express the stress-strain relationship of confined high strength concrete by carrying out regression analysis of the main parameters affection strength and ductile behavior of reinforced high strength concrete columns. Twenty-five test specimens were chosen from the reported experimental studies in the literature. The experimental results of stress-strain relationships of show a good agreement with results of the stress-strain relationships of suggested high strength concrete, covering a strength range between 60 and 124 MPa.

Multi-Physics Blast Analysis for Steel-Plated and GFRP-Plated Concrete Panels

The blast damage behaviors of steel-plated and glass fiber reinforced polymer (GFRP)-plated concrete panels exposed to explosive are investigated. In order to improve efficiency and accuracy of numerical analysis, the multi-physics method of coupled Eulerian-Lagrangian discretization is used. To enhance the reliability of the simulation results, the equation of state, strength, and failure model of materials are implemented in an explicit program, AUTODYN. In particular, the implemented formulation includes the strain rate-dependent plasticity for concrete and a transversely isotropic elastic constitutive model for GFRP. The retrofitted concrete panels are compared to non-retrofitted concrete panels, and the deflection and deflection ratio are reduced by steel and GFRP plates. To validate the implemented material models and analysis method, a comparison is made with the reported experimental results. The maximum deflection of the panel from the numerical analysis agrees closely with the results of the experiments. Finally, a discussion of the numerical results with respect to code criteria and energy absorption capacity is presented.

Flexural Behavior of Prestressed Dual Concrete Beams

Cracks due to low tensile strength in prestressed concrete (PC) beams may decrease rigidity and structural performance, resulting in excessive deflection. In an effort to solve this problem, in this research, prestressed dual concrete (PDC) has been proposed, consisting of normal strength concrete in compression zone, and high performance steel fiber reinforced concrete(HPSFRC) with a partial depth in tensile zone. Three PDC beams with different depths of HPSFRC and two PC beams were cast for experiments. Analytical models at each stage, i.e., precracking, postcracking, and ultimate, were proposed for analysis of flexural behavior in PDC beams. The experimental results agree well to the analytical ones. Crack formation and its propagation are controlled by the HPSFRC in PDC beams. The initial cracking and service limit loads are increased along with the load carrying capacity and flexural stiffness.