Abstract
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.
Highlights
The earthquake catastrophe is one of the primary reasons for destruction of buildings, engineering infrastructures, and social systems [1]
This study expects that the amount of lateral forces being transmitted from earth to upper levels, which have been strengthened with steel X-bracing system, and subsequently the effect of impact will decrease as a result of high energy absorption capacity of offdiagonal bracing system (ODBS) system in lower floors of the structure
Macromodeling method was used to analyze the nonlinear behavior of reinforced concrete frame strengthened by steel bracing system
Summary
The earthquake catastrophe is one of the primary reasons for destruction of buildings, engineering infrastructures, and social systems [1]. Earthquake is known as the most common natural disaster since a large number of earthquakes of various magnitudes, which have caused serious damages, have been recorded in historical documents According to these recorded earthquakes, the death toll is estimated to be around 800,000 people far [2]. The total number of killed people was estimated to be 80,000 Such catastrophes happen because of the large magnitude of earthquakes and as a result of nonstandard structures and weak buildings. The use of reinforced concrete structures increases in Iran Factors such as availability of required materials, simpler construction procedure, and possibility for creation of larger spaces persuade designers and engineers to employ this system [6, 7]. It is worth understanding if application of offdiagonal bracing system (ODBS), which earns steel structures more ductility, makes reinforced concrete structures more ductile or not
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