Applied Mechanics and Materials Vols. 166-169

Abstract: The method of strain-based fatigue analysis is applied on the study of fatigue behavior of reinforced concrete (RC) beams strengthened with fiber reinforced polymer (FRP) laminates in this paper. Based on the investigation of fatigue performance of RC beams strengthened with FRP laminates presented in the published literatures, the values of stress concentration factors and the coefficients in Neuber’s rule are suggested. The exponent of fatigue strength in Manson-Coffin formula is discussed so as to having a general stain-life curve which is suitable for the fatigue behavior prediction of RC beam strengthened with FRP laminates. The S-N curves of different stress ratios can be developed and the fatigue lives of the strengthened beams are pointed out.

Abstract: Based on the experimental results of twenty three high strength concrete-filled square steel tubular (HCFT) columns subjected to cyclic lateral load, the restoring force model of square HCFT columns is established. Through theoretical analysis and experimental results, the main parameters of the restoring force model which are axial load ratio, confinement effect coefficient as well as slenderness ratio are discussed. The theoretical method is put forward. The results show that the relation of elastic stiffness to degraded stiffness, the relation of ultimate bearing capacity to yielding loads are proportional with confinement effect coefficient, and inversely with axial load ratio as well as slenderness ratio. Many various influential factors are considered in the restoring force model of square HCFT columns. The model is close to the experimental results which can be conveniently applied for nonlinear dynamics analysis of composite structures.

Abstract: With different original status including crack, controlled stretching stress and reinforcement ratio, five reinforced concrete box beams strengthened with external prestressed tendons were designed. The stress increment of external tendons was studied by indoor test and Finite Element Method analysis. The study shows that the less the controlled stretching stress is, the more rapidly the prestressed stress increment increases. There is no clear difference between the beam with original crack and without crack. In the test, the measured ultimate stress of external prestressed tendon agrees with the calculated result based on deflection method, and the stress in serviceability stage agees with the result based on structural mechanics method. In Finite Element model, the change of effective prestress, concrete strength, the area and depth of external tendons will result in a little change of stress in serviceability stage, but obvious change in ultimate status. the change of tendons lateral distance to the web results in litlle change of stress in the whole loading stage , no matter it is inside or outside the box at cross section.

Abstract: Use of hollow material in slab can reduce self-weight and deflection than solid slab with GFRP reinforcement. In this study, bending tests were carried out to evaluate the bending performance of void slabs with GFRP reinforcements. Test results showed that bearing capacity at the compression zone seriously affected the ultimate bending strength of void flexural members. For a design of the void flexural members with GFRP bars, it needs to use the higher concrete strength and to arrange the void foams considering of the crushing failure and distribution of strains and stresses.

Abstract: Due to the particularity, the reinforcement and reconstruction of steel structures should adopt a unique way. Combined with practical engineering, this paper introduces the program of Laizhou department store building reinforcement project. According to the specific requirements of the reinforcement and reconstruction, we analyze the original structure, introduce structure designs of the adding three layers as well as the reinforcement of bottom two layers, which makes construction more convenient and faster, and achieves the purpose of economic and appliance. The reinforcement of steel columns decide the period and cost. This paper expounds the reinforcement method of steel columns, and obtains the force of the bolt through the finite element analysis.

Abstract: Bond of corroded reinforcement in concrete wrapped with CFRP was investigated experimentally. An electrolyte corrosion technique was used to accelerate reinforcement corrosion. Wrapped specimens were strengthened with one layer of CFRP. The experimental parameters were investigated include: corrosion level and the mode of CFRP wrapped. The results of the experiment indicate that: ultimate bond stress of wrapped specimens is greater than that of unwrapped specimens. The CFRP confinement proved more effectively at the higher corrosion rate. These results are helpful to evaluate the strength and residual life of CFRP strengthened the reinforced concrete structures.

Abstract: Finite element analysis model of reinforced concrete beam with CFRP by ANSYS were built in this paper. Through finite element method analysis of comparing the concrete beam with and without CFRP , some conclusions are given in the paper; the Fatigue Mechanism was studied , and obtained the raise the level of fatigue life of reinforced concrete beam with CFRP .The result shows CFRP can increase greatly its fatigue life and improve effectually the ductility of the structure.

Abstract: This article describes test and results of long term effect by sulphate environment on new designed crystalline technology based material with fly-ash as partly cement substituent. At this article are presented results of new developed modification, which was the most effective and suitable for further commercial production during long term physical and mechanical tastings. Main aim of the experiment was to analyze ability of this new material to develop crystalline structure in capillary system and proof effectiveness of new developed crystalline structure in concrete pore system affected by long term sulfur medium attack.

Abstract: A hybrid coupling beam is developed in this study to render the reinforced concrete (RC) shear wall structure a higher seismic performance. As the first protection from earthquake, the coupling beam is able to dissipate more energy when combined in series with a metallic damper. The strength of the metallic damper is carefully selected so that the RC part of the coupling beam remains elastic, while all plasticity goes into the metallic damper. This mechanism protects the RC part from seismic damage. And the metallic damper can be quickly replaced once it is damaged. This significantly enhances the reparability of entire structure, making it possible to be immediately functioned after earthquakes. The stiffness of the hybrid coupling beam is similar as the traditional RC coupling beam, so that the dynamic characteristics are almost unchanged. In this study, one hybrid coupling beam and one traditional RC beam are experimentally examined. The seismic dissipation capability of the hybrid beam is approximately twice of the traditional beam, and the damage of the RC part of the hybrid beam is very limited.

Abstract: This paper introduces a stressed member which is composited of GRC enhanced reinforcement template combined with post-pouring concrete structure. The GRC template is as a permanent template combining with concrete into a composite beam. The surface of the template is respectively dealed in different ways. Through contrasting the results of stress performance experiment with ordinary beam,studing the cooperative performance between GRC templates and post-pouring concrete, as well as the effect of bearing stress of composite beams with templates in different treatment ways. The optimal size is diameter 15mm, depth 5mm from the experiment.