Advanced Materials Research Vols. 133-134

Abstract: The historical masonry buildings form widespread spectrum of existing buildings in IRAN. destruction on structures illustrate that historical masonry buildings have maximum damages due earthquake, in addition they don't actuate properly about seismic behavior (the main reason of this is lack of proper ductility). Shear of the masonry walls, is the only structural element of these type buildings, undertake gravity load and lateral load. This is the main reason that leads to researchers think over techniques about improvement and strengthening the walls, and also leads to experiencing real samples and scaled models. In this essay, at the beginning was introduced a method about modeling finite elements unreinforced masonry (URM) wall by using of software (ANSYS). In order to verifying the correctness of modeling, it's require to do experimental test on a sample of wall and then that wall should be modeled by illustrated method. Then correctness of modeling method and analyzing method should be verified by comparing the result of numerical modeling with the result of modeling experimental. The experimental model has been examined at Shiraz University. The result of numerical modeling and analyzing illustrate that lateral load-displacement curve is stiffer than experimental curve. And lateral load carrying capacity has precision about 99.28 percent, and lateral displacement has precision about 94.1 percent. also the numerical results agree reasonably well with the experimental results. In the next stage the masonry walls are strengthened with Carbon Fiber Reinforced Polymer sheets (CFRPs). five different strengthening methods have been used with different thickness. The strengthened walls are affected by vertical loads and in-plane shear. It is found that the critical loads, the critical displacement, the ultimate loads, the ultimate displacements and the ductile coefficients of the masonry walls strengthened with CFRPs improve remarkably.

Abstract: Many studies showed that FRP bonded to the concrete beams and column surface can effectively enhance the mechanical properties of members, and FRP reasonably bonded to the beam-column joint area can significantly improve the seismic performance, but not enough studies have been carried out on the overall mechanical properties in structure after the framework members are partially covered with FRP. In this Paper, based on the seismic demand analysis of the concrete frame structure, as well as FRP seismic enforcement strategy, a fiber attachment method has been proposed for FRP seismic reinforcement framework. Taking a two-layer dual-span plane framework as an example, nonlinear static analysis has been carried out on FRP-reinforced framework, the capacity spectrum method has been adopted to assess the seismic performance of reinforced framework and the impact of different FRP-reinforced methods on structural seismic performance has been discussed. The results showed that the method of moderate shear-resistance reinforcement in the joint core area, as well as the beam-column plastic hinge area, can effectively improve the seismic performance of the framework, the application of GFRP reinforcement features higher cost-performance ratio, and the FRP bonding at ± 45º in the joint core area can better the reinforcement effect.

Abstract: Recently, laminates of multi-directional carbon fiber reinforced polymers (MDL-CFRP) have been developed for Civil Engineering applications. A MDL-CFRP laminate has fibers in distinct directions that can be arranged in order to optimize stiffness and/or strength requisites. These laminates can be conceived in order to be fixed to structural elements with anchors, resulting high effective strengthening systems. To evaluate the strengthening potentialities of this type of laminates, pullout tests were carried out. The influence of the number of anchors, their geometric location and the applied pre-stress are analyzed. The present work describes the carried-out tests and presents and analyzes the most significant obtained results.

Abstract: In this paper the behavior and the collapse mechanism of single leaf vaulted structures undergoing seismic loads are discussed, and an innovative technique based on the use of lightweight ribs is proposed. The efficiency of the solution is verified by means of non linear numerical analyses on a strengthened single leaf vaulted structure. The numeric model is validated through comparison with the results of experimental tests performed on lightweight ribs subjected to cyclic, unsymmetrical load conditions.

Abstract: A three-story old building made up of masonry and wood will be retrofitted to be a new 14-story building, retaining two exterior walls and removing all internal members. To prevent the retained walls form deforming severely or collapse during the retrofit is necessary. The finite element analysis software, ANSYS, is used to calculate the responses of the retaining walls under possible loading conditions. The original retrofit proposal for the old building is refined based on the calculation results.

Abstract: The building of the formerly Yihe Spinner Factory in Shanghai is a protected. To ensure its serviceability, appropriate retrofitting is necessary. Structural analysis based on the inspection result was performed. It is shown that the bearing capacity or the ductility of some members in the original structure as well as the retrofit proposal are inadequate. Strengthening design was then performed. The effect of the subsequent retrofitting process on the strengthened structure was analyzed. The historical building is then properly protected and the new manufacturing requirements are meet through the retrofitting and strengthening design. The proposed methods can serve as references for relative research or engineering practices.

Abstract: The use of high-strength composites in the reinforcement of structural timber has been documented to enhance the strength and stiffness of wood structural members. Global reinforcement is applied over the entire surface of the reinforced member. Local reinforcement is a targeted strengthening of highly-stressed zones susceptible to failure. Both types of reinforcement enhance the capacity of the reinforced members and mitigate brittle failure modes. This paper presents an overview of the application of fiber-based composites in the reinforcement of beams, columns and connections of timber structures and discusses the state-of-the-art technologies in reinforcement. The applications are illustrated on the reinforcement of beams, arches, frames and beam-to-column connections.

Abstract: The high seismic vulnerability of several monumental masonry buildings can be ascribed to the low strength of the materials employed, to the presence of wide openings and slender panels and to the high stress due to both vertical and horizontal seismic forces. A new upgrading system, named DIS-CAM (DISsipative Active Confinement of Masonry) was proposed to design the seismic upgrading of the tambour of the dome of the S. Nicolò’s church in Catania (Italy). The technique, that can be considered reversible and a not invasive, is based on a rocking-damper system, in which the rocking and the re-centring capacity are provided by the behaviour of masonry panels, while the dissipation capacity is mainly relied upon hysteretic elements stressed in flexure beyond their elastic limit. In this paper, the design of the scaled model’s seismic upgrading is presented and the main outcomes of preliminary numerical analyses carried out on the tambour, without any reinforcement and retrofitted with the DIS-CAM system, are discussed.

Abstract: The 6th of April 2009 a strong earthquake (rated 5.8 on the Richter scale) struck the Abruzzo region in central Italy, causing hundreds of casualties and devastating the historical city of L’Aquila and several small towns in the area. The toll in terms of structural damage was enormous, also considered that a vast amount of buildings was made of poorly arranged masonry composed by round pebbles and mortar of scarce mechanical characteristics. In particular, the buildings belonging to cultural heritage (e.g. churches and monumental buildings) were between the structures that suffered more from seismic damage, considered their dimensions, mass and general lack of adequate connections. Few weeks after the seismic event, a church in the historical city centre of L’Aquila, the S. Marco church, was “adopted” by the Italian Veneto Region, which paid and provided the necessary technical support for the first necessary provisional structural interventions. The paper describes the steps undertaken in order to provide the building with the minimum safety conditions necessary to face the aftershocks, and to survive without further collapses to be subsequently retrofitted. A static and dynamic structural monitoring system was also installed in the church since the beginning of the works, in order to control the safety conditions of the area during the execution of the interventions and to assess the damage progression or stationariness.

Abstract: The purpose of this research is to determine the mechanical properties of historic masonry walls retrofitted with Glass Fiber Reinforced Polymer (GFRP) under axial load through experimental method. Four ancient masonry wall specimens were tested under axial load acted at the top surface. Two wall specimens were served as reference without retrofitting. The third wall was retrofitted with GFRP on full surface before loading. The forth wall was strengthened with three GFRP strips before loading. The behaviors of historic masonry walls in Thailand were particular because of their special bond manner and dimension. The tested results demonstrated that the bearing capacity of historic masonry walls was distinctly improved after GFRP strengthening.