Showing papers by "Payam Shafigh published in 2011"

Assessing the strength of reinforced concrete structures through Ultrasonic Pulse Velocity and Schmidt Rebound Hammer tests

Abstract: The experimental studies using Ultrasonic Pulse Velocity and Schmidt Rebound Hammer as Non-Destructive Tests (NDT) were presented in this paper to establish a correlation between the compressive strengths of compression tests and NDT values. These two tests have been used to determine the concrete quality by applying regression analysis models between compressive strength of in-situ concrete on existing building and tests values. The main members of an existing structure including column, beam and slab were included in the study. The relationship between compression strength of concrete collected from crashing test records and estimated results from NDT’s records using regression analysis was compared together to evaluate their prediction for concrete strength. The test results show that the rebound number method was more efficient in predicting the strength of concrete under certain conditions. A combined method for the above two tests, reveals an improvement in the concrete strength estimation and the latter shows better improvement. Applying combined methods produces more reliable results that are closer to the true values. The resulting strength calibration curves estimation was compared with other results from previous published literatures. Key words: Non Destructive testing (NDT), Schmidt Rebound Hammer (SRH); Ultrasonic Pulse Velocity (UPV), NDT combined method, compressive strength, regression analysis.

An investigation of the flexural behaviour of reinforced lightweight concrete beams

Abstract: This paper presents an investigation of the flexural behaviour of reinforced lightweight concrete beams made from lightweight expanded clay aggregate (LECA). Nine reinforced concrete beams were fabricated and tested using the symmetrical two-point loads test. The concrete strength and steel bar reinforcement were two important parameters examined during the beam tests. The paper compares flexural performance of the tested beams for example failure modes, load deflection response, and ultimate moment capacity with those of the theoretical analysis. The experimental results suggest that the ultimate moment of beams made with LECA lightweight concrete could be predicted satisfactorily using the equation provided by the ACI 318 building code. However, the maximum section bars for restraining brittle compression failure should be reduced in the beams. Key words: Lightweight concrete, reinforced concrete beam, flexural behaviour, failure mode, ultimate moment.

An experimental study on shear reinforcement in RC beams using CFRP-bars

Abstract: Fibre reinforced polymer (FRP) as an alternative to steel in reinforced concrete (RC) beams has become increasingly popular. The merits of FRP include high strength to weight ratio and corrosion resistance, and its advantages cannot be ignored in civil engineering. Consequently, FRP has attracted considerable interest from researchers. In this research, the effects of using CFRP bars as shear reinforcement instead of stirrups in RC beams have been investigated. All beams were cast using a high strength concrete (HSC), which was also a self-compacting concrete (SCC). For this new idea, modes of failure for seven laboratory specimens, including a comparison of the ultimate moment capacity of beams, load-deflection control, load of first crack, crack width and position of the neutral axis (N.A.) were analysed. The results show that using carbon fibre reinforced polymer (CFRP) shear reinforcement can be an acceptable alternative for normal stirrups in RC beams.