Repair and Retrofit of Non-Ductile Reinforced Concrete Frames with Diagonal Steel Compression Struts

Title: Repair and Retrofit of Non-Ductile Reinforced Concrete Frames with Diagonal Steel Compression Struts
Authors: Caron, Frederic
Date: 2010
Abstract: Reinforced concrete frames built before the 1970s were designed prior to the enactment of seismic codes. These frames were designed with strong beams and weak columns, which is contradictory to the capacity design philosophy currently employed. These frames lack sufficient shear and confinement reinforcement. The joints, columns, and beams are susceptible to shear failures, thus preventing these frames from reaching their full flexural capacity. Such premature failures have no warning and are characterised by inadequate ductility, which is one of the key performance indicators in seismic design. There are two general methods to rehabilitate a concrete frame. The first would be to add new structural elements such as infill walls or steel bracing, and the second would be to strengthen the structural elements: the joints, beams, and columns. The latter has been studied using fibre reinforced polymers (FRP) and steel jackets. The main objective for this research is to evaluate the response of repaired and retrofitted non-ductile reinforced concrete frames which are vulnerable to earthquake loading. The main focus is to investigate a quick, easy and inexpensive retrofit method that could be used before or after a structure is damaged. The retrofit method utilizes diagonal X-bracing fabricated from square steel hollow sections, which are designed as compression struts to retrofit non-ductile reinforced concrete frames in an attempt to increase stiffness and lateral load capacity. The advantage is the elimination of costly and detailed connections necessary to exploit the tension capacity of the brace. Two, single-storey, one-bay, non-ductile reinforced concrete frames were first repaired. One frame was tested to assess the seismic performance of the repair strategy and the second frame was retrofitted with steel X-bracing. Experimental and analytical results for both the retrofitted and repaired frames are presented. Code prescribed calculations and finite element analyses were performed to evaluate the frames and to provide comparisons between code-expected performance and advanced modelling predictions.
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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