• Steel and Composite Structures
• /
• 제21권4호
• /
• pp.687-702
• /
• 2016

There are many studies in the literature conducted on the subject of ensuring earthquake safety of reinforced concrete and steel structures using steel braced frames, but no detailed study concerning individual behavior of steel braced frames under earthquake loads and strengthening of reinforced concrete structures with out-of-plane steel braced frames has been encountered. In this study, in order to evaluate behaviors of "Concentrically Steel Braced Frames" types defined in TEC-2007 under lateral loads, dimensional analysis of Concentrically Steel Braced Frames designed with different scales and dimensions was conducted, the results were controlled according to TEC-2007, and after conducting static pushover analysis, behavior and load capacity of the Concentrically Steel Braced Frames and hinges sequence of the elements constituting the Concentrically Steel Braced Frames were tested. Concentrically Steel Braced Frames that were tested analytically consist of 2 storey and one bay, and are formed as two groups with the scales 1/2 and 1/3. In the study, Concentrically Steel Braced Frames described in TEC-2007 were designed, which are 7 types in total being non-braced, X-braced, V- braced, $\wedge$- braced, $\backslash$- braced, /- braced and K- braced. Furthermore, in order to verify accuracy of the analytic studies performed, the 1/2 scaled concentrically steel X-braced frame test element made up of box profiles and 1/3 scaled reinforced concrete frame with insufficient earthquake resistance were tested individually under lateral loads, and test results were compared with the results derived from analytic studies and interpreted. Similar results were obtained from both experimental studies and pushover analyses. According to pushover analysis results, load-carrying capacity of 1/3 scaled reinforced concrete frames increased up to 7,01 times as compared to the non-braced specimen upon strengthening. Results acquired from the study revealed that reinforced concrete buildings which have inadequate seismic capacity can be strengthened quickly, easily and economically by this method without evacuating them.

• Structural Engineering and Mechanics
• /
• 제61권6호
• /
• pp.755-763
• /
• 2017

In this study, the susceptibility of different symmetric steel buildings with dual frame system to Progressive Collapse (PC) was assessed. Some ten-story dual frame systems with different type of braced frames (concentrically and eccentrically braced frames) were considered. In addition, numbers and locations of braced bays were investigated (two and three braced bays in exterior frames) to quantitatively find out its effect on PC resistance. An Alternate Path Method (APM) with a linear static analysis was carried out based on General Services Administration (GSA 2003) guidelines. Maximum Demand Capacity Ratio (DCR) for the elements (beams and columns) with highest DCRs ($DCR_{moment}$ and $DCR_{shear}$) is given in tables. The results showed that the three braced bays with concentric braced frames especially X-braced and inverted V-braced frame systems had a lower susceptibility and greater resistance to PC. Also, the results represented that the beams were more critical than columns against PC after the removal of column.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2008년도 정기 학술대회
• /
• pp.319-324
• /
• 2008

In this study the progressive collapse potential of special concentrically braced frames were investigated using the nonlinear static. All of seven different brace types were considered. According to the pushdown analysis results, most braced frames designed according to current design codes satisfied the design guidelines for progressive collapse initiated by loss of a first story mid-column; however most model structures showed brittle failure mode. This was caused by buckling of columns after compressive braces buckled. Among the braced frames considered, the inverted-V type braced frames showed superior ductile behavior during progressive collapse.

• Structural Engineering and Mechanics
• /
• 제4권4호
• /
• pp.365-381
• /
• 1996

Stability equations that evaluate the elastic critical axial load of columns in any type of construction with sidesway uninhibited, partially inhibited, and totally inhibited are derived in a classical manner. These equations can be applied to the stability of frames (unbraced, partially braced, and totally braced) with rigid, semirigid, and simple connections. The complete column classification and the corresponding three stability equations overcome the limitations and paradoxes of the well known alignment charts for braced and unbraced columns and frames. Simple criteria are presented that define the concept of partially braced columns and frames, as well as the minimum lateral bracing required by columns and frames to achieve non-sway buckling mode. Various examples are presented in detail that demonstrate the effectiveness and accuracy of the complete set of stability equations.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2006년도 정기 학술대회 논문집
• /
• pp.733-740
• /
• 2006

Inverted V (or chevron) braced steel frames have been seen as being highly prone to soft story response once the compression brace buckles under earthquake loading. To salvage chevron braced frames. the concept of the zipper column was proposed many years ago such that the zipper column can redistribute the inelastic demand over the height of the building. However. rational design method for the zipper column has not been established yet. In this paper, a new dynamic design method for the zipper column was proposed by combining the refined physical braced model and modal pushover analysis. Inelastic dynamic analysis conducted on 6 story building model showed that the proposed method was more superior to the existing static design method and was very effective in improving seismic performance of chevron braced steel frames.

• Earthquakes and Structures
• /
• 제13권5호
• /
• pp.443-454
• /
• 2017

When eccentrically braced steel frames (EBFs) are in the desired failure mode, links yield at each layer and column bases appear plastically hinged. Traditional design methods cannot accurately predict the inelastic behavior of structures owing to the use of capacity-based design theory. This paper proposes the use of performance-based seismic design (PBSD) method for planning eccentrically braced frames. PBSD can predict and control inelastic deformation of structures by target drift and failure mode. In buildings designed via this process, all links dissipate energy in the rare event of an earthquake, while other members remain in elastic state, and as the story drift is uniform along the structure height, weak layers will be avoided. In this condition, eccentrically braced frames may be more easily rehabilitated after the effects of an earthquake. The effectiveness of the proposed method is illustrated through a sample case study of ten-story K-type EBFs and Y- type EBFs buildings, and is validated by pushover analysis and dynamic analysis. The ultimate state of frames designed by the proposed method will fail in the desired failure mode. That is, inelastic deformation of structure mainly occurs in links; each layer of links involved dissipates energy, and weak layers do not exist in the structure. The PBSD method can provide a reference for structural design of eccentrically braced steel frames.

• Structural Engineering and Mechanics
• /
• 제64권3호
• /
• pp.301-310
• /
• 2017

For further development of passive control systems to dissipate larger seismic energy and prevent the structures from earthquake losses, this paper proposes an innovative two-level control system to improve behavior of chevron braced steel frames. Combining two Knee Braces, KB, and a Vertical Link Beam, VLB, in a chevron braced frame, this system can reliably sustain main shock and aftershocks in steel structures. The performance of this two-level system is examined through a finite element analysis and quasi-static cyclic loading test. The cyclic performances of VLB and KBs alone in chevron braced frames are compared with that of the presented two-level control system. The results show appropriate performance of the proposed system in terms of ductility and energy dissipation in two different excitation levels. The maximum load capacity of the presented system is about 30% and 17% higher than those of the chevron braced frames with KB and VLB alone, respectively. In addition, the maximum energy dissipation of the proposed system is about 78% and 150% higher than those of chevron braced frames with VLB and KB respectively under two separate levels of lateral forces caused by different probable seismic excitations. Finally, high performance under different earthquake levels with competitive cost and quick installation work for the control system can be found as main advantages of the presented system.

• Earthquakes and Structures
• /
• 제6권3호
• /
• pp.267-280
• /
• 2014

Shape Memory Alloy (SMA) braces can be used to reduce seismic residual deformations observed in steel braced Reinforced Concrete (RC) frames. To further enhance the seismic performance of these frames, the use of SMA bars to reinforce their beams is investigated in this paper. Three-story and nine-story SMA-braced RC frames are designed utilizing regular steel reinforcing bars. Their seismic performance is examined using twenty seismic ground motions. The frames are then re-designed using SMA reinforcing bars. Different design alternatives representing different locations for the SMA reinforcing bars are considered. The optimum locations for the SMA bars are identified after analysing the design alternatives. The seismic performance of these frames has indicated better deformability when SMA bars are used in the beams.

• 한국전산구조공학회논문집
• /
• 제23권1호
• /
• pp.111-119
• /
• 2010

여러 연구자들에 의해 최적화 알고리즘을 이용한 최적내진설계에 관한 연구가 컴퓨터의 발달과 더불어 활발히 이루어져 왔다. 하지만 지금까지의 최적내진설계에 관한 연구는 대부분 모멘트저항골조를 대상구조물로 한 연구였다. 가새골조는 모멘트저항골조와 더불어 대표적인 횡력저항시스템이기 때문에 가새골조의 최적내진설계기법 개발을 통해 경제적이며 효율적인 설계가이드라인을 제시할 수 있다면 실무에 미치는 파급효과는 클 것이라 판단된다. 본 논문에서는 가새의 좌굴을 고려한 역V형 특수중심가새골조의 최적내진설계 알고리즘을 제안하고자 한다. 제안된 알고리즘은 구조물의 물량과 에너지 소산량을 목적함수로 설정하고, 강도조건 및 층간변위 조건등의 제약조건으로 설정한다. 알고리즘의 검증을 위해 2D 3층, 9층 역V형 특수중심가새골조 예제를 적용한다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
• /
• pp.231-234
• /
• 2005

Steel braced frames retrofit method has been broadly used due to their effectiveness in both light weight and construction periods. However, steel braced frames retrofit method has difficulties in application on the inner frames of buildings to be retrofitted consequently, there have been demands for the braced frames retrofit method that can be broadly and easily applicable to both inner and outer frames of the buildings. The objective of this study is to develop and evaluate the seismic retrofit method applicable to the inner frame also by dividing the reinforcing frames into three unit. From the cyclic test of specimens, the test results dearly showed that steel brace using HPFRCCs and steel bars ensure the better cyclic compressive performance than the normal braced members.