Numerical simulation of the shear behaviour of reinforced concrete rectangular beam specimens with or without FRP-strip shear reinforcement
The successful validation of a numerical model is presented that can realistically approximate the shear behaviour of reinforced concrete (R/C) rectangular beams strengthened against shear with externally applied open hoop fibre reinforcing polymer (FRP) strips. For this purpose, the measured load-deformation response of ten (10) full-scale R/C beam specimens is utilised. These specimens were loaded monotonically in a four-point bending arrangement up to failure. Open hoop FRP strip shear reinforcement was applied externally to upgrade the shear capacity of eight (8) R/C beam specimens. Four of these specimens had these FRP strips without anchorage, whereas for the other four the FRP strips were attached together with novel anchoring devices. This successful numerical simulation predicts with a very good degree of approximation the observed load-deformation behaviour and the ultimate shear capacity of all these specimens as well as the observed modes of failure including diagonal concrete cracking, debonding of the FRP strips in the case of no anchoring, or the plastification of parts of the anchoring devices plus the adjacent crushing of the concrete.
Experimental study on FRP-to-concrete bonded joints
The behaviour of bond between FRP and concrete is a key factor controlling the behaviour of concrete structures strengthened with FRP composites. This article presents an experimental study on the bond shear strength between FRP and concrete using a near-end supported (NES) single-shear pull test. The test results are found to be in close agreement with the predictions of Chen and Teng’s [J. Struct. Eng. 127(2001) 784] bond strength model, which mutually verifies the reliability of both the test method and the Chen and Teng model in general. The NES single-shear pull test, given its simplicity and reliability, is therefore a good candidate as a standard bond test. The test results also showed that Chen and Teng’s [J. Struct. Eng. 127(2001) 784] bond strength model is slightly conservative when the FRP-to-concrete width ratios are at the two extremes, but this small weakness can be easily removed when more test results of good quality become available. q 2004 Elsevier Ltd. All rights reserved.
Centrifuge modelling of effects of shield tunnels on existing tunnels in soft clay
With the rapid development of the subway network,the phenomena of shield tunnels going across the adjacent tunnels are becoming more and more common.The interaction between shield tunneling and nearby tunnels is more complicated than the ordinary shield tunneling in intact soil strata.Based on the project of Shanghai Bund Passage crossing Metro Line 2,the method of centrifuge modeling together with the field measurement is employed to study the effects shield tunneling on nearby strata and existing tunnels.In centrifugal model tests,the effects simulation techniques considering the unloading of excavation,ground loss and grouting are developed to analyze the longitudinal settlement of the shield tunnel and the existing tunnel induced by the shield tunneling.Besides,the deformation distribution and settlement curves of the existing tunnels during shield construction are studied by using the monitoring data.