• Structural Engineering and Mechanics
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• 제84권2호
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• pp.269-283
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• 2022

In this paper, a particular type of all-steel HSS brace members with a locally reduced cross-sectional area was experimentally and numerically investigated. The brace member was strengthened against local buckling with inner and outer boxes in the reduced area. Four single-span braced frames were tested under cyclic lateral loadings. Specimens included a simple steel frame with a conventional box-shaped brace and three other all-steel reduced section buckling-restrained braces. After conducting the experimental program, numerical models of the proposed brace were developed and verified with experimental results. Then the length of the proposed fuse was increased and its effect on the cyclic behavior of the brace was investigated numerically. Eventually, the brace was detailed with a fuse-to-brace length of 30%, as well as the cross-sectional area of the fuse-to-brace of 30%, and the cyclic behavior of the system was studied numerically. The study showed that the proposed brace is stable up to a 2% drift ratio, and the plastic cumulative deformation requirement of AISC (2016) is easily achieved. The proposed brace has sufficient ductility and stability and is lighter, as well as easier to be fabricated, compared to the conventional mortar-filled BRB and all-steel BRB.

• Steel and Composite Structures
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• 제26권6호
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• pp.745-757
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• 2018

The inclusion of a ductile steel bracing as means of repairing an earthquake-damaged bridge bent is evaluated and experimentally assessed for the purposes of restoring the damaged bent's strength and stiffness and further improving the energy dissipation capacity. The study is focused on substandard reinforced concrete multi-column bridge bents constructed in the 1950 to mid-1970 in the United States. These types of bents have numerous deficiencies making them susceptible to seismic damage. Large-scale experiments were used on a two-column reinforced concrete bent to impose considerable damage of the bent through increasing amplitude cyclic deformations. The damaged bent was then repaired by installing a ductile fuse steel brace in the form of a buckling-restrained brace in a diagonal configuration between the columns and using post-tensioned rods to strengthen the cap beam. The brace was secured to the bent using steel gusset plate brackets and post-installed adhesive anchors. The repaired bent was then subjected to increasing amplitude cyclic deformations to reassess the bent performance. A subassemblage test of a nominally identical steel brace was also conducted in an effort to quantify and isolate the ductile fuse behavior. The experimental data from these large-scale experiments were analyzed in terms of the hysteretic response, observed damage, internal member loads, as well as the overall stiffness and energy dissipation characteristics. The results of this study demonstrated the effectiveness of utilizing ductile steel bracing for restoring the bent and preventing further damage to the columns and cap beams while also improving the stiffness and energy dissipation characteristics.

• Steel and Composite Structures
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• 제45권5호
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• pp.683-695
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• 2022

Conventional braces are often used to provide stiffness to structures; however due to buckling they cannot be used as seismic energy dissipating elements. In this study, a seismic energy dissipation device is proposed which is comprised of a bracing member and a steel hysteretic damper made of steel hexagonal plates. The hexagonal shaped designated fuse causes formation of plastic hinges under axial deformation of the brace. The main advantages of this damper compared to conventional metallic dampers and buckling-restrained braces are the stable and controlled energy dissipation capability with ease of manufacture. The mechanical behavior of the damper is formulated first and a design procedure is provided. Next, the theoretical formulation and the efficiency of the damper are verified using finite element (FE) analyses. An analytical model of the damper is established and its efficiency is further investigated by applying it to seismic retrofit of a case study structure. The seismic performance of the structure is evaluated before and after retrofit in terms of maximum interstory drift ratio, top story displacement, residual displacement, and energy dissipation of dampers. Overall, the median of maximum interstory drift ratios is reduced from 3.8% to 1.6% and the residual displacement decreased in the x-direction which corresponds to the predominant mode shape of the structure. The analysis results show that the developed damper can provide cost-effective seismic protection of structures.

• 한국강구조학회 논문집
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• 제27권2호
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• pp.169-180
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• 2015

최근 구조물의 내진설계 기준이 2009년도 개정되면서 내진설계기준이 점차 구체화 되고 있다. 이에 따라 내진설계기준이 반영되지 않았거나 현재의 기준을 만족시키지 못하는 국내 구조물에 대해 재 검토 될 필요가 있다. 특히 중 저층 구조물의 경우 횡력 저항 요소는 대부분 가새에 의해 설계되어 있다. 즉 현재 사용 중인 가새가 반복적인 지진하중에도 전체 구조물의 안정성을 확보할 수 있도록 합리적인 보강방안이 구체화 될 필요가 있다. 본 연구에서는 무용접 냉간성형 강재로 조립된 압축가새의 구조적 성능과 거동을 분석하고자 한다. 실험변수는 보강길이 그리고 보강단면 비를 중점으로 구조실험을 수행하였다. 따라서 본 연구에서는 세장한 H형강 가새의 휨좌 굴을 억제하여 압축내력을 발휘토록 보강방안을 제안하였고, 보강안의 압축거동을 검증하기 위해 세장비와 보강량을 변수로 구조 성능 실험을 수행하여 강도, 강성, 변형성능과 파괴거동의 분석을 수행하였다.

• 전산구조공학
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• 제10권1호
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• pp.201-211
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• 1997

공간뼈대의 구조에 대하여 기하학적 비선형성이 고려될 수 있는 유한요소이론 및 해석법을 제시한다. 이를 위하여 가상일의 원리를 이용하여 대변형효과를 고려한 3차원 연소체의 평형방정식으로부터, 구속된(restrained warping)효과를 무시하고 유한한 회전각의 2차항의 효과를 포함하는 변위장을 도입하여 초기응력을 받는 공간뼈대요소의 증분평형방정식을 유도한다. 공간뼈대구조를 유한요소로 나누어 요소의 변위장을 요소변위 벡터에 관한 Hermitian다항식으로 나타내고 이를 평형방정식에 대입함으로써 탄성 및 가하학적인 강도행렬을 유도한다. 또한 updated Lagrangian co-rotational formulation에 근거하여, 증분변위로부터 강체회전변위와 순수변형성분을 분리시켜서 강체회전은 요소의 방향변화를 결정하고, 순수변형은 부재력증분을 산정하는 불평형하중 산정법을 제시한다. 공간뼈대구조의 횡-비틂좌굴 및 후좌굴 거동에 대한 예제들을 통하여 본 연구에 대한 해석결과와 문헌의 결과를 비교 검토함으로써 본 연구에서 제시된 이론 및 해석방법의 정당성을 입증한다.