• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2005.04a
• /
• pp.619-627
• /
• 2005

An initial member sections of steel structures is selected by experience of expert building structural designers. And appropriate member section is designed by repeat calculation through structural analysis. Therefore an initial assumption of member section is necessary for saving the time for structural design and is important to acquire safety of building structures. Also brace damper are generally used to prevent or decrease structural damage by its hysteretic behavior in building structures subjected to strong earthquake. Based on plastic design, the initial section of members for architectural steel structures with brace hysteretic dampers is presented and seismic effect of structural behavior by the ratio of damper stiffness to structural story stiffness is estimated in this paper.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.10a
• /
• pp.288-295
• /
• 2004

Concentrically braced steel frames are considered as being quite pone to soft-story response due to the degradation in brace compressive resistance after buckling under severe ground motions. When combined with the system P-Delta effects, collapse of the concentrically brsced frames by dynamic instability becomes highly probable. In this stidy, a new, relatively simple dynamic instability coefficient was proposed for diagonally braced steel flames by explicitly considering the strength degradation of the brace after buckling. Nonlinear dynamic analysis results showed that the dynamic instability coefficient proposed in this study predicted collapse limit state more consistently than the conventional one which ignores the strength degradation of the brace.

• Journal of Korean Association for Spatial Structures
• /
• v.22 no.1
• /
• pp.51-57
• /
• 2022

In this paper, based on the finite element analysis model verified in previous studies, a new model of a buckling restrained brace reinforced with a steel plate was proposed. A design formula was proposed for the new model to dissipate energy without buckling the steel core under load protocol, and the performance of the model satisfying the design formula was evaluated by comparing it with the previous model through the results of hysteresis loop, bi-linear curve, cumulative energy dissipation capacity, and equivalent viscous damping.

• Journal of Korean Society of Steel Construction
• /
• v.27 no.3
• /
• pp.261-271
• /
• 2015

Steel concentrically braced frame is an efficient system that can acquire resistance against the lateral force of buildings with the least amount of quantity. In this study is intended to proceed on the research of schemes for reinforcement by supplementing previously installed H-formed brace with non-welded cold-formed plastic stiffening materials restricting the flexure and buckling and acquire a consistent strength on the tensile and compressive force. As for the measures of supplementing previously-installed inverted V-formed braced frame, stiffening materials in the previous studies were converted to weak-axial supplementing materials to suggest a specific scheme evaluating the structural function through an experiment of members, interpretation of members, and frame-focused experiment. Reinforced brace satisfied the requirement to be prevent AISC brace from being ruptured due to imbalanced strength in the beam.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.4
• /
• pp.65-72
• /
• 2022

Recently, damage to buildings due to earthquakes in Korea occurred mainly in school buildings and Piloti-type multi-family houses, highlighting the need for seismic retrofit for buildings of the same type. In the early days of the seismic retrofit project for school facilities, various patented methods using dampers as a ductile seismic retrofit method were applied without sufficient verification procedures. However, in 「School Facility Seismic Performance Evaluation and Retrofit Manual, 2021」, when the patented method is applied, it must be applied through a separate strict verification procedure, and instead, the strength/stiffness retrofit method was induced as a general method. In practice,when evaluating seismic performance for retrofit by infilled steel frame with brace, the analysis model is constructed by directly connecting only the steel brace to the existing RC member. However, if the frame is removed from the analysis model of the infilled steel frame with brace, the force reduction occurring on the existing RC member near the retrofit is considered to be very large, and this is judged to affect the review of whether to retrofit the foundation or not. Therefore, in this study, preliminary analysis with variables such as whether or not steel frame is taken into account and frame link method for the analysis model of RC school building retrofitted by infilled steel frame with brace and nonlinear analysis for actual 3-story school building was performed, and basic data for rational analysis model setting were presented by comparing preliminary analysis and pushover analysis results for each variable.

• Journal of the Korean Institute of Rural Architecture
• /
• v.16 no.2
• /
• pp.1-8
• /
• 2014

In the past, Korea was classified as a region not affected by earthquakes. However, recent increase of earthquakes has forced to strengthen standards of earthquake resistant designs of structures to minimize seismic damage. In addition, it was thought that masonry infill walls in buildings are only acting as partitions, so these walls are not considered in analyzing building structures. But it was found that when seismic loads are applied to a structure with masonry infill walls, the walls affect the structure. Accordingly, this study conducted nonlinear static analyses for a structure constructed before applying earthquake resistant designs in two cases: when considering masonry walls and when not. The result showed that the seismic performance of the structure is insufficient. Thus, the structural resistance of the structure was also studied in two cases: when reinforcing with steel plate braces and when using carbon fiber braces. In the two cases reinforcing two different stiffeners, it was appeared that the behaviors of the structure were similar, though the cross-section area of a carbon fiber brace used to reinforcing the structure is only 12.6% of a steel plate brace, and its weight is only 2.8%. Thus, the reinforcing effect of the thin, light-weighted carbon fiber brace is much larger than that of the steel plate brace, when considering usability and constructability of both materials.

• Steel and Composite Structures
• /
• v.19 no.1
• /
• pp.173-190
• /
• 2015

This study presents an analytical investigation on the seismic response of a medium-rise buckling-restrained braced frame (BRBF) under the near-fault ground motions. A seven-story BRBF is designed as per the current code provisions for five different combinations of brace configurations and beam-column connections. Two types of brace configurations (i.e., Chevron and Double-X) are considered along with a combination of the moment-resisting and the non-moment-resisting beam-to-column connections for the study frame. Nonlinear dynamic analyses are carried out for all study frames for an ensemble of forty SAC near-fault ground motions. The main parameters evaluated are the interstory and residual drift response, brace displacement ductility, and plastic hinge mechanisms. Fragility curves are developed using log-normal probability density functions for all study frames considering the interstory drift ratio and residual drift ratio as the damage parameters. The average interstory drift response of BRBFs with Double-X brace configurations significantly exceeded the allowable drift limit of 2%. The maximum displacement ductility characteristics of BRBs is efficiently utilized under the seismic loading if these braces are arranged in the Double-X configurations instead of Chevron configurations in BRBFs located in the near-fault regions. However, BRBFs with the Double-X brace configurations exhibit the higher interstory drift and residual drift response under near-fault ground motions due to the formation of plastic hinges in the columns and beams at the intermediate story levels.

• Steel and Composite Structures
• /
• v.31 no.2
• /
• pp.149-158
• /
• 2019

The force-deformation behavior, strain distribution and failure modes of a variable damping self-centering brace (VD-SCB) are theoretically analyzed, experimentally studied, and numerically simulated to guide its design. The working principle of the brace is explained by describing the working stages and the key feature points of the hysteretic curve. A large-scale brace specimen was tested under different sinusoidal excitations to analyze the recentering capability and energy dissipation. Results demonstrate that the VD-SCB exhibits a full quasi-flag-shaped hysteretic response, high ultimate bearing capacity, low activation force and residual deformation, and excellent recentering and energy dissipation capabilities. Calculation equations of the strain distribution in different parts of the brace are proposed and are compared with the experimental data and simulated results. The developments of two failure modes are compared. Under normal circumstances, the brace fails due to the yielding of the spring blocking plates, which are easily replaced to restore the normal operating conditions of the brace. A brief description of the design procedure of the brace is proposed for application.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.1
• /
• pp.35-42
• /
• 2020

Torsional behavior due to the plane irregularities of the piloti building can cause excessive story drift in the torsionally outermost column, which can lead to shear failure of the column. As a seismic retrofit method that can control the torsional behavior of the piloti building, the expansion of RC wall, steel frame or steel brace may be used, but such methods may hinder the openness of the piloti floor. Therefore, in this study, linear dynamic analysis and nonlinear static analysis for piloti buildings retrofitted by knee brace were performed, and seismic performance evaluation and torsion control effect of knee brace were analyzed. The results showed that the shear force of the column increased when the piloti building retrofitted by knee brace, but it was effective in controlling the torsional deformation. In case of retrofit between knee brace and column by 30°, the shear force of the column increased less than that of 60°, and the lateral displacement of column was decreased in the order of □, ◯ and Ｈ in cross-section.

• Journal of Korean Society of Steel Construction
• /
• v.27 no.2
• /
• pp.207-217
• /
• 2015

A concentrically braced steel frame is a very efficient structural system because it requires relatively smaller amount of materials to resist lateral forces. However, primarily developed as a structural system to resist wind loads based on an assumption that the structure behaves elastically, a concentrically braced frame possibly experiences the deterioration in energy dissipation after brace buckling and the brittle failure of braces and connections when earthquake loads cause inelastic behavior. Consequently, plastic deformation is concentrated in the floor where brace buckling occurs first, which can lead to the rupture of the structure. This study suggests reinforcing H-shaped braces with non-welded cold-formed stiffeners to restrain flexure and buckling and resist tensile force and compressive force equally.