Observations on Two Seismic Strengthening Schemes for Concrete Frames

Bush, Thomas D.; Wyllie, Loring A.; Jirsa, James O.

doi:10.1193/1.1585640

Cited by 15 publications

(8 citation statements)

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“…The strengthened frame was exposed to lateral and gravity loadings and its displacements were allowed to increase by one fiftieth of the frames' original height (allowable drift). The strengthened inside frame by a ductile steel bracing demonstrated considerably better behavior than the preliminary reinforced concrete frame [11] or applied from outside the frame [12].…”

Section: Study Literaturementioning

confidence: 90%

Seismic Behavior of Steel Off-Diagonal Bracing System (ODBS) Utilized in Reinforced Concrete Frame

Ramin

2014

Journal of Structures

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The introduction of an eccentricity in this system results in a geometric nonlinearity behavior. The midpoint of the diagonal member is connected to the corner joint using a brace member with a relatively low stiffness, thus forming a three-member bracing system in each braced panel. An iterative method of analysis has been developed to study the nonlinear load-deflection behavior of ODBS. The results indicate that the load-deflection behavior of this system follows a nonlinear stiffness-hardening pattern with two yielding points, which reflect the tensile failure of different bracings; the present study aims to investigate the efficiency of applying off-diagonal steel braces to reinforced concrete frames. To achieve this, three types of 2-story, 6-story, and 15-story structures without and with X-bracing and off-center bracing systems were modeled using SAP2000 software, and for micromodeling ANSYS software was used to achieve finite element results for an exact comparison between various retrofitting systems. The results showed that the structures strengthened by toggle bracing system revealed better behavior for low oscillation periods. Moreover, this type of bracing system is quite suitable for 10-story structures but not for higher ones. Its main problem, which requires special contrivances to solve, is the existence of a soft ground floor.

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Section: Study Literaturementioning

confidence: 90%

Seismic Behavior of Steel Off-Diagonal Bracing System (ODBS) Utilized in Reinforced Concrete Frame

Ramin

2014

Journal of Structures

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“…The strengthened frame was exposed to lateral and gravity loads and its displacements were allowed to increase by one fiftieth of the frame's Original height (inter-story drift). The strengthened inside frame by a ductile steel brace, demonstrated better behavior considerably than the preliminary reinforced concrete frame (Masri and Goel 1996) or applied from outside the frame (Bush et al 1991).…”

Section: Research Backgroundmentioning

confidence: 90%

Finite Element Modeling and Nonlinear Analysis for Seismic Assessment of Off-Diagonal Steel Braced RC Frame

Ramin¹,

Fereidoonfar²

2014

Int J Concr Struct Mater

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The geometric nonlinearity of off-diagonal bracing system (ODBS) could be a complementary system to covering and extending the nonlinearity of reinforced concrete material. Finite element modeling is performed for flexural frame, x-braced frame and the ODBS braced frame system at the initial phase. Then the different models are investigated along various analyses. According to the experimental results of flexural and x-braced frame, the verification is done. Analytical assessments are performed in according to three dimensional finite element modeling. Nonlinear static analysis is considered to obtain performance level and seismic behaviour, and then the response modification factors calculated from each model's pushover curve. In the next phase, the evaluation of cracks observed in the finite element models, especially for RC members of all three systems is performed. The finite element assessment is performed on engendered cracks in ODBS braced frame for various time steps. The nonlinear dynamic time history analysis accomplished in different stories models for three records of Elcentro, Naghan and Tabas earthquake accelerograms. Dynamic analysis is performed after scaling accelerogram on each type of flexural frame, x-braced frame and ODBS braced frame one by one. The base-point on RC frame is considered to investigate proportional displacement under each record. Hysteresis curves are assessed along continuing this study. The equivalent viscous damping for ODBS system is estimated in according to references. Results in each section show the ODBS system has an acceptable seismic behaviour and their conclusions have been converged when the ODBS system is utilized in reinforced concrete frame.

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“…In some other researches, the use of wing walls, attached to two sides of columns was investigated. The systems strengthened with wing walls exhibited ductile behaviour (Higashi et al 1982;Bush et al 1991).…”

Section: Introductionmentioning

confidence: 97%

“…Bracing can either be implemented inside the frame (Masri & Goel 1996) or applied from outside the system (Bush et al 1991). Post-tensioned steel bracing is also an efficient alternative for vulnerable framed buildings (Gilmore et al 1996) and it compensates structural irregularities.…”

Section: Introductionmentioning

confidence: 99%

Seismic strengthening of RC structures with exterior shear walls

Kaplan

Yılmaz

Çetinkaya

et al. 2011

Sadhana

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Vulnerable buildings and their rehabilitation are important problems for earthquake regions. In recent decades the goal of building rehabilitation and strengthening has gained research attention and numerous techniques have been developed to achieve this. However, most of these strengthening techniques disturb the occupants, who must vacate the building during renovation. In this study, a new strengthening alternative for RC structures, namely exterior shear walls, has been experimentally investigated under reversed cyclic loading. Using the proposed technique, it is possible to strengthen structures without disturbing their users or vacating the building during renovation. In this technique, shear walls are installed in parallel to the building's exterior sides. It has been observed that the usage of exterior shear walls considerably improve the capacity and sway stiffness of RC structures. The experimental results have also been compared and found to be in agreement with the numerical solutions. Post attached exterior shear walls behaved as a monolithic member of the structure. Design considerations for the exterior shear wall-strengthened buildings have also been discussed in the paper.

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Observations on Two Seismic Strengthening Schemes for Concrete Frames

Cited by 15 publications

References 0 publications

Seismic Behavior of Steel Off-Diagonal Bracing System (ODBS) Utilized in Reinforced Concrete Frame

Seismic Behavior of Steel Off-Diagonal Bracing System (ODBS) Utilized in Reinforced Concrete Frame

Finite Element Modeling and Nonlinear Analysis for Seismic Assessment of Off-Diagonal Steel Braced RC Frame

Seismic strengthening of RC structures with exterior shear walls

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