Jung-Han Yoo

Analytical Investigation for Improved Design Models of Chevron Braced Frames

Steel Braced frames are a commonly-used seismic resisting system, and chevron steel braced frames are a frequently used type of steel braced frame. Recent research has indicated that the seismic performance of braced frames can be improved by designing the braced frame gusset plate connections in a manner that direct reflects seismic deformation demands, and by permitting yielding in the gusset plate at select performance levels. A parametric study using Finite Element (FE) models was conducted to examine the influence of the gusset plate and framing elements on the seismic performance of chevron braced frames, and to calibrate and develop improved design models. The impact of the frame details, including frame sizes, clearance requirements, gusset plate thickness and tapered plate, was explored. The results suggested that proper detailing of the connection can result in a significant improvement in the frame performance. The results also show that the gusset plate thickness has a significant impact on frame performance.

Evaluation of Seismic Behavior in Non-Seismic Concentrically Braced Frames

SCBFs (Special Concentrically Braced Frames) have been praised for considerable strength, high lateral stiffness, economic feasibility and good performance of seismic loads, which make engineers widely use SCBF as lateral-load resisting systems in buildings and have researchers develop design requirements. Compared to the extensive research of SCBF, comparatively little information is currently available on the performance of SCBFs designed and constructed before the early 1990’s. Before the early 1990’s, CBFs (Concentrically Braced Frames) design requirements were substantially less restrictive. As a result, many existing structures designed to these requirements may not exhibit desirable behavior in a seismic event. Existing CBFs that do not meet modern SCBF criteria shall be referred to herein as NCBFs (Non-Seismic Concentrically Braced Frames). In this study, FE (Finite Element) analysis was carried out. The detailed inelastic FE models were verified, which are based on the preceding research. Finally, these models were compared to evaluate the seismic performance of NCBFs.

Local Buckling Behaviors of Built-Up Box Columns Fabricated with High-Performance Steel under Concentric Axial Loading

Recently, high-performance steel has been increasingly used for structural materials in buildings and bridges with the demand for high-rise and long-span of main structures. This paper is a series of basic study for the design specification of structural members using high performance steel, material properties of HAS800(High-performance rolled Steel for building structures). HSA800 was compared with the requirements of Korean Standards(KS). Built-up box stub columns with variables of width-to-thickness ratios are planned in order to investigate the local buckling behaviors and check the current design limit of width-to-thickness ratio. In addition, the buckling behaviors of stub columns obtained finite element analysis were compared with those of test results.