Tae-Sung Eom

Secant Stiffness for Direct Inelastic Earthquake Design of Reinforced Concrete Structures

For safe and economical design to provide strong earthquake resistance, the moment redistribution and plastic rotation of structures and their members needs to be evaluated. To achieve this, an earthquake design method was developed using secant stiffness analysis. To address the variation of member stiffness due to plastic rotation and moment redistribution, a structure was modeled with a beam-column element with non-rigid end connections (NREC element). Secant stiffness for the NREC element was determined based on the ductility demands of the structure and members. By performing a conventional linear analysis for the secant stiffness model, redistributed moments and plastic rotations of the members were computed. The proposed method was applied to a moment frame and two dual systems. The design results were verified using detailed nonlinear analyses.

Applications of Construction Sequence Analyses to Prototype Models of Twisted Tall Buildings

Abstract With regard to complex-shaped tall buildings whose plans and constructions have been gradually on the increase, this study was aimed to analyze their structural behaviors during construction by applications of construction sequences analyses to prototype models. For twisted tall buildings, total 18 models of with three conditions of a lateral load-resisting system, a twisting angle, and a construction method were selected. A diagrid system and a braced tube system were applied as a lateral load-resisting system. For each lateral load-resisting system, three types of plan with 0, 1, and 2twisting angles and three construction methods with construction sequences of exterior tube and interior frame were assumed. The structural performances of tall buildings under constructions were analyzed with results of lateral displacements from construction sequence analyses. Also, construction performances of the construction period and the maximum lift weight were compared. Keywords :tall building, complex-shape, construction sequence analysis, construction, twisted shapes

Shear Design of Concrete Belt Walls Reinforced with Post-Tensioning Bars

In the present study, shear design methods for concrete belt walls reinforced with pre-stressing steel bars (PS belt walls) were developed. For diagonally reinforced PS belt walls, a strut-and-tie model based on strain-compatibility was proposed to evaluate the shear strength and maximum deformation. For vertically and horizontally reinforced PS belt walls, on the other hand, shear strengths and deformations at concrete cracking and ultimate state were evaluated based on the Compression Field Theory. Design examples for PS belt walls were illustrated and the aspects of the load-transfer and design considerations were discussed. The results showed that diagonally reinforced PS belt walls exhibited brittle shear failure due to concrete crushing before yielding of PS bars. In addition, since the concrete strut rather than PS bars carries significant shear, attention should be paid on the detailing of the nodal zone. On the other hand, vertically and horizontally reinforced PS belt walls failed due to the yielding of PS bars before concrete crushing. However, the number of PS bars for shear design was increased and the reduction in the stiffness after shear cracking was significant.

Evaluation of Deformation Capacity of Slender Reinforced Concrete Walls with Thin Web

Dept. of Architectural Engineering, Kwangwoon University, Seoul 139-701, KoreaABSTRACT In the present study, the deformation capacity of slender shear walls with thin web subject to inelastic deformationafter flexural yielding was studied. Web-crushing and rebar-fracture were considered as the governing failure mechanisms of walls.To address the effect of the longitudinal elongation on web-crushing and rebar-fracture, the longitudinal elongation was predictedby using truss model analysis. The failure criteria by web-crushing and rebar-fracture were defined as a function of the longitudinalelongation. The proposed method was applied to 17 shear wall specimens with boundary columns, and the prediction results werecompared with the test results. The results showed that proposed method predicted the maximum deformations and failure modesof the wall specimens with reasonable precision.Keywords : deformability, web crushing, reinforcement fracture, shear wall, reinforced concrete