Advanced Materials Research Vols. 163-167

Abstract: A reinforcing method is introduced, concerning the inclined and cantilever features in the structure of the Palms together dagoda in the Famen Monastery and the cracking in the floor slab of 54 meters high. According to the actual situation, the welding of the strengthened metal and the structure on the nodes is difficult to achieve. In order to make some improvement, we use bolt connection run throng the wall body instead of steel belt and steel bone welding, which will make the transmission of the structure more clear, shorten the construction period and ensure the engineering quality effectively. This method can also be used for the reinforcement in concrete structures of large span and tall buildings. Therefore, the discussion of processing technology dealing with the combination of the structural cracks in floor which this article focuses on, has some reference value on similar projects.

Abstract: Steel-concrete interface skid resistance properties have been studied by orthogonal test. Three factors are considered, including glue amount, silicon carbide mesh, and amount of silicon carbide. For each factor, five levels are selected. Through comparative analyses of the experiment results for each factor and the combinations of the levels of the factors, the combination with the optimal interface skid resistance was obtained. The friction coefficient with consideration of glue cohesive force was also determined. The research results provide references for structure strengthening using adhered steel plates and external prestressing.

Abstract: Pointed to character of flexible support of cave dwelling on prestressed anchor for geotechnical engineering, rheological mechanics was used to analyze support effects,and a new viso-elasto-plastic rheological model was built with locked minimum load formula abtained.Such is the property that bonding soil,surrounding soil,bolts and arc surface were studied.And the finite difference method(FLAC^3D) with C++ and inline FISH program were applied to analyze stress, anchor,plastic state,shear strain rate and displacement distribution.Based on calculated results and investigation on spot, plenty of key parameters on whole bonged and prestressed bolt were studied. The numerical calculation is coincident with testing factors.So the theory basis is provided for effective support engineering.

Abstract: The effectiveness of strengthening reinforced concrete (RC) beams with prestressed near- surface mounted (NSM) carbon fiber reinforced polymer (CFRP) rods has been investigated. The RC beams are tested under monotonic loading. The stressing process, failure capacity, flexural capaticy, displacement ductility and deformation are systematically studied. The text results show that the new strengthening technique with prestressed NSM CFRP rods can enhance the first-crack load, steel-yielding load of beams compared to the control beam. It is worth noting that the prestress can limit the crack width all the way up to failure, reduce the midpoint deflection, and improve the service performance of the strengthened beams. The strengthening method offers an alternative way to existing strengthening method. The results provide a reference for engineering application.

Abstract: Un-reinforced masonry (URM) structures may fail and collapse under out-of-plane loads generated by seismic forces or explosions. Adding a ferrocement overlay onto the URM walls is an effective solution in increasing the ultimate load capacity and ductility. This paper deals with the numerical and experimental studies on the out-of-plane behavior of un-reinforced masonry walls strengthened with ferrocement. The material parameters considered are the volume fraction of reinforcement and the loading area. A numerical model was proposed to simulate the experimental results. The employed material model for masonry wall is based on the theory of Drucker-Prager plasticity taking into account the tension softening behavior, while the ferrocement is modeled as a composite material with linear strain hardening followed by ideal plasticity. The proposed model simulates the load-deflection behavior of the strengthened wall well.

Abstract: This template Based on cracks observation and finite element analysis of real engineering projects as well as bridge load test after reinforcement, causes and types of cracks in prestressed concrete box girder bridges and treating measurements are systematically studied. The results obtained from the calculation are presented to demonstrate the effect of sensitive factors, such as arrangement of longitudinal prestressed tendons, the magnitude of vertical prestressed force, temperature gradient, etc. The results show that the arrangement of longitudinal prestressed tendons and the magnitude of vertical prestressed force take key roles in cracks control of box girder webs. Lots of treating measurements are presented in accordance with different types of cracks, some of them are applied to a reinforcement engineering of a long span pretressed concrete continuous box girder bridge with cracks. Load test after reinforcement of the bridge demonstrates the reasonability of the treating measurements. Several design recommendations and construction measures about reinforcements and some sensitive factors mentioned above are proposed to control cracks.

Abstract: This paper presents a phase of the research program to determine the feasibility of a proposed CFRP retrofit method to strengthen the corroded concrete filled steel tube columns. This method is wrapping the corroded concrete filled steel tube column with CFRP material. Eight concrete filled steel tube columns were tested in the laboratory with four of them strengthened using the proposed technique. All specimens were notched in the center zone to simulate the loss of section due to corrosion the four of them were wrapped with CFRP composite tubes in the damage area. All specimens were axially loaded to failure while strain and displacement were measured to demonstrate the validity of this repair concept. This paper presents the experimental results and discusses the findings with preliminary conclusions on the feasibility of the proposed strengthening method.

Abstract: The research of this paper focused on bond characteristics of overlay-substrate interface in ultra-thin white topping(UTW), aim at ultra-thin concrete overlay on old concrete. Compressive and shear stress have been considered in the structural analysis and experimental research. Bonding behaviors of several surface pretreatments to old concrete have been investigated. A shear-peel test device has been developed to imitate brake-load of wheels at the plate boundary of UTW, and its analytical calculate principle have been discussed to simulate the mechanical theory of the shear peel test. Structural analysis and experimental research results indicate that various flaws are accumulated remarkably in the transition layer at overlay-substrate interface in UTW. Different surface pretreatments of the old concrete will influence on the bonding characteristics of overlay-substrate interface, chiseling treatment for interface has more contribution to working together with the new concrete, but interface adhesive agent enhances the coordination between the interface and the old concrete layer. The treatment combination of chiseling and brushing interface adhesive can effectively improve the strength of the weak interface transition layer. Shear-peel test results indicate that the interlocking influence generated by chiseling treatment is prior to brushing interface adhesive. It is necessary turn to account suitable measure to prevent ultra-thin concrete overlay peeling off from old concrete.

Abstract: Shrinkage experiments were done to determine the influence of the volume fraction of steel fiber-reinforcement on the bonding behavior between new concrete and old concrete. The mechanics of the model of restricted shrinkage upon the adherence of new steel fiber reinforced concrete to old concrete are described. The results demonstrate that the difference of shrinkage between the new and the old concrete can been reduced by adding steel fiber to the new concrete. The decrease of shrinkage difference reduces the shrinkage force at the adhesive interface, which improves the adhesion of new concrete to old concrete and the magnitude of the decrease of shrinkage difference is correlated to the steel fiber volume fraction.

Abstract: Based on analysis of the hysteretic experimental results of the concrete filled square CFRP-steel tubular (S-CFRP-CFST) beam-columns, it shows that the steel tube and the CFRP material can work concurrently both in longitudinal and transverse directions, the longitudinal strain and the transverse strain at a same point have opposite action. Additionally, the deflection curves of all the specimens are close to half sinusoidal shape. Analysis indicates that there is some strength degradation. The axial compression ratio and strengthening factor of the longitudinal CFRP can enhance the strength and the stiffness of the members and they can also delay the stiffness degradation. However, they will decrease the accumulated energy dissipation of the members. The axial compression ratio is beneficial to seismic behaviors to some extent.