Applied Mechanics and Materials Vols. 578-579

Abstract: For floor serviceability, stiffness and resonance are dominant consideration in the design of long-span floor systems or large-cantilever floor systems, which usually have lower stiffness and smaller dampings. In this paper, a dynamic characteristics test of long-span cantilevered floor systems in Shenyang Culture & Art Center was performed by using pulsating methods to determine the natural frequencis and the dampings, which were compared with those from the numerical modal analysis based on the Midas/gen platform. The research provides a basis for a further study of floor vibrations due to human comfort.

Abstract: This paper study the effects of stress amplitude on the fatigue performance of reinforced concrete (RC) beams strengthened with carbon fibre laminate (CFL). A total of 15 spcimens were tested under three point bending. Three load levels over 60% bending capacity of the strengthened beams with a stress ratio of 0.1 were applied to three groups of five specimens, respectively. The stress amplitudes of groups 2 and 3 are 10% and 15% larger than group 1, respectively. The loads and deflections during the tests were recorded. The fatigue stiffness of the strengthened RC beams with variable stress amplitude was discussed. The experimental results show that the rates of the bending stiffness deterioration of the retrofitted beams, which increase with the load level, under constant fatigue loading are smaller than those under variable fatigue loading.

Abstract: In recent years, with the development of technology and theoretical study of bridge engineering, systematically retrofitting the old, sick and dangerous bridges has been an important content of bridge construction. There are many ways to reinforce bridges, and methods vary because of the form of bridge structure, location and terrain. This paper analyzed several common methods of bridge reinforcement, and made some instructions of the key points .

Abstract: This paper focuses on the characterization of shear behavior of RC beams strengthened with Near-Surface Mounted (NSM) GFRP bars. Based on ABAQUS, the finite element model for the shear behavior is established and the simulated results are compared with the test results. The parameters including spacing and inclination of GFRP bars, mechanical properties of the groove-filling epoxy, stirrup ratio and shear-span ratio of the specimen beams for the shear behavior are discussed. The simulated results show that there has a good agreement with the experiment results. The beams strengthened with NSM GFRP bars have a significant improvement in shear capacity. Further more, the analysis results on the parameters indicate that ultimate shear capacity of the beam strengthened with NSM-GFRP bars gradually increases with the decrease of spacing of GFRP bars. The ultimate bearing capacity increases of the strengthened beam with inclination of 45° is the more larger than those of 60° and 90°. The different types of epoxy adhesive and shear-span ratio have a great influence on the load-deflection curves of the strengthened beams.

Abstract: In this paper, the structural performance of an existing old masonry building constructed in 1963 was detected in filed and assessed. The results indicated that essential strengthening measures should be adopted to improve its stiffness, strength and seismic performance. To keep the original architectural appearance and style of the building due to its particular historical significance, various strengthening technics (e.g. the externally bonded steel plate technic, the adding steel braces to enhance the lateral stiffness, the strengthening with steel mesh reinforced concrete splint method and etc.) were thus designed to repair and strengthen the structure. 10% probability of failure risk was used to determine the earthquake parameters involved in the seismic strengthening design, which has also reduced the engineering cost. The design methods presented in this study and the corresponding seismic construction measures adopted in the project are validated to be effective and feasible, and have achieved the given performance - oriented.

Abstract: Based on experimental research and calculation theory of flexural bearing capacity, a method for calculating the ultimate load bearing of normal section member strengthened with prestressed CFL is proposed. Static load experimental results of two beams show that when prestress level is 20%, the cracking load and yield load of RC beams strengthened with prestressed CFL are 37.5% and 39.3% respectively. It is larger than that of RC beam strengthened with nonprestressed CFL.

Abstract: Based on the calculation method of cracking load for reinforced concrete beam, the formula to calculate cracking load of normal section for concrete beams strengthened with BFRP sheet is established. The cracking load experiment of seven concrete beams strengthened with BFRP and three concrete beams strengthened with CFRP is conducted, and the results showed that fiber sheet layers and fiber sheet types have little effect on cracking load of concrete beams strengthened, the cracking load of beams strengthened mainly depends on the strength of concrete. The comparison between estimated values and test values of concrete beams strengthened indicates that the estimated values are slightly smaller, the formula can be used to calculate the cracking load of concrete beams strengthened.

Abstract: During punching shear failure process, the stress states near slab-column node are complex and nonlinear characters of reinforced concrete make the problems more complicated. In this paper, by considering nonlinear characters of reinforced concrete, punching carrying capacities of slab-column nodes are to analyze by using nonlinear finite element methods, and then the reasonable reinforcement schemes at slab-column nodes have been determined. The slab-column nodes are strengthened by using CFRP sheets. Compare punching bearing capacities of nodes in reinforcement structure with that in unreinforcement structure, the results show that this strengthened method can effectively improve punching resistance bearing capacities of slab-column nodes.

Abstract: A progressive collapse of a RC frame structure may be initiated by an event that damages one member of the structure. FRP is widely used in the field of structural reinforcement for its high strength ratio, convenient construction and corrosion resistance. In this paper, the collapse scene of a RC frame specimen with the failure mid-column in three programs has been simulated by LS-DYNA. We can infer the ultimate bearing capacity of the structure is raised about 10% (retrofitted by CFRP), 15% (retrofitted by GFRP) by comparing the results of finite element analysis.

Abstract: A contrast investigation of the seismic behavior of unreinforced masonry walls with window openings strengthened with Carbon Fiber Reinforced Polymer (CFRP) sheets and sprayed Glass Fiber Reinforced Polymer (GFRP) is presented. Three wall specimens in the scale of 1/2 were tested by the horizontal cyclic loading combined with constant gravity loads. The seismic strengthening effects by two different FRP retrofitting schemes are compared in aspect of the failure modes, shear capacity, hysteresis response, deterioration of rigidity and ability of energy dissipation. The experimental results indicate that the increasing degree of shear capacity and the improvement of seismic behavior of the SGFRP-strengthened wall are significantly superior to that of the wall strengthened with epoxy-based CFRP; and the overcoat of sprayed GFRP can bond tightly and work well together with the masonry to play a critical role in earthquake resistance.