Hong-Gun Park

Hysteresis Model of Thin Infill Plate for Cyclic Nonlinear Analysis of Steel Plate Shear Walls

A hysteresis model for thin infill steel plates was developed to evaluate the nonlinear cyclic behavior of steel plate shear walls. Nonlinear finite-element analysis was performed for thin steel plates with a rigid boundary frame. Based on the analysis results, the hysteretic behavior of the infill steel plate was simplified as an equivalent uniaxial stress-strain relationship in the direction of tension-field action. The proposed hysteresis model was implemented in macroscopic analysis models for infill steel plates, i.e., the tension strip model and equivalent tension brace model. The proposed method was applied to existing test specimens with various design parameters and loading conditions. The prediction results were compared with the test results.

Cyclic Loading Test for Reinforced Concrete Frame with Thin Steel Infill Plate

An experimental study was performed to investigate the cyclic behavior of walls that are composed of reinforced concrete boundary frames and thin steel infill plates. For this purpose, three-story steel plate infilled walls (SPIW) were tested. The parameters in this test were the reinforcement ratio of the columns and opening in the infill plates. A reinforced concrete infilled wall (RCIW) and a reinforced concrete frame (RCF) were also tested for comparison. The deformation capacity of the SPIW specimens was significantly greater than that of the RCIW specimen, though the specimens exhibited an identical load-carrying capacity. Similar to the steel plate walls with steel boundary frames, the SPIW specimens showed excellent strength, deformation capacity, and energy dissipation capacity. Furthermore, by using the steel infill plates, shear cracking and failure of the column-beam joints were prevented. By using the strip model, the strength and initial stiffness of the SPIW specimens were predicted. The pr...

Elongation of Reinforced Concrete Members Subjected to Cyclic Loading

Longitudinal elongation develops in reinforced concrete members that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the members. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams and the effects of various design variables on the elongation. The results showed that residual tensile plastic strain of the longitudinal reinforcement in the plastic hinge is the primary factor causing the member elongation and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the elongation mechanism found by truss model analysis, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions.

Concrete-Filled Steel Tube Columns Encased with Thin Precast Concrete

AbstractAn experimental study was performed to investigate the axial-flexural load-carrying capacity of concrete-filled steel tube columns encased with thin precast concrete (PC). Six eccentrically loaded columns and one concentrically loaded column were tested. To prevent the premature failure of the concrete encasement, various reinforcement details such as studs, steel fiber, welded wire mesh, and cross ties were used. The maximum axial loads of the specimens agreed with the strengths predicted by current design codes, although in some specimens, the load-carrying capacity decreased immediately after the peak strength owing to early spalling of the concrete encasement. On the basis of the test results, the use of fiber-reinforced concrete is recommended to increase the ductility of columns by restraining the spalling of the concrete encasement.

Seismic Resistance of Cast-In-Place Concrete-Filled Hollow PC Columns

Two types of cast-in-place concrete-filled hollow PC (HPC1, HPC2) columns were developed to reduce lifting load of heavy-weight PC columns and to improve the structural integrity of joints. To form the hollow PC columns, a couple of prefabricated PC panels was used for HPC1, and special hoops were used for HPC2. Lateral pressure of wet concrete on PC faces was measured while placing the concrete inside the columns. To evaluate the seismic resistance, full scale specimens of two HPC columns and a conventional RC column were tested under combined axial compression and lateral cyclic loading. The test results showed that the structural performance of the proposed HPC columns such as intial stiffness, maximum strength, and displacement ductility was comparable to that of the conventional RC column, but the energy dissipation of HPC2 slightly decreased after rebar-buckling. However, all the test specimens satisfied the energy dissipation requirement specified in ACI 374.

Longitudinal Reinforcement Ratio for Performance-based Design of Reinforced Concrete Columns

The longitudinal reinforcement ratio for the performance-based design of columns was studied. Unlike the existing design codes using uniform minimum reinforcement ratio and effective stiffness for all columns, the longitudinal reinforcement ratio of columns was defined as the function of various design parameters. To evaluate the minimum reinforcement ratio, two conditions were considered: 1) prevention of passive yielding of compression re-bars due to the creep and shrinkage of concrete under sustained service loads; and 2) ultimate flexural strength greater than the cracking moment capacity to maintain the ductility of columns for earthquake design. In addition, the effective flexural stiffness of columns for structural analysis was determined according to the longitudinal reinforcement ratio. The design method addressing the three criteria was proposed. The proposed method was applied to a design example.