Boquan Liu

Experimental Investigation of Reinforced Concrete T-Beams Strengthened with Steel Wire Mesh Embedded in Polymer Mortar Overlay

The application of steel wire mesh (SWM) and polymer mortar composites to the surface of reinforced concrete (RC) members as external reinforcement is a promising and recent new technique for strengthening and rehabilitating damaged concrete elements. Five one-third-scale simply supported RC T-beams were tested during this study. Four-point bending flexural tests were conducted up to failure on one control beam and on four strengthened beams with different load histories. The objectives of this investigation were to study the effectiveness of SWM and polymer mortar composites in increasing the flexural strength of concrete beams and to study the construction technology for further development. The main test parameters included the amount of longitudinal SWM reinforcement and the load history. The results demonstrate the feasibility of rehabilitating and strengthening RC members with SWM composites and indicate that the ultimate strength of RC T-beams, strengthened with SWM composites, is almost the same regardless of the load history at the time of strengthening. A design procedure is presented with aim to predict the flexural strength of T-beams strengthened with SWM composites. Good agreement between experiment and predicted values was achieved.

Experimental Study on Bond Behavior between Plain Reinforcing Bars and Concrete

To evaluate the bond behavior between the reinforcing bar and surrounding concrete, a total of six-group pullout specimens with plain steel bars and two-group specimens with deformed steel bars, serving as a reference, are experimentally investigated and presented in this study. The main test parameters of this investigation include embedment length, surface type of reinforcing bars, and bar diameter. In particular, the bond mechanism of plain steel reinforcing bars against the surrounding concrete was analyzed by comparing with six-group pullout specimens with aluminium alloy bars. The results indicated that the bond stress experienced by plain bars is quite lower than that of the deformed bars given equal structural characteristics and details. Averagely, plain bars appeared to develop only 18.3% of the bond stress of deformed bars. Differing from the bond strength of plain steel bars, which is based primarily on chemical adhesion and friction force, the bond stress of aluminium alloy bars is mainly experienced by chemical adhesion and about 0.21~0.56 MPa, which is just one-tenth of that of plain steel bars. Based on the test results, a bond-slip model at the interface between concrete and plain bars is put forward.

Calculation of Axial Compression Capacity for Square Columns Strengthened with HPFL and BSP

The load carrying capacity and failure mechanism of 8 square columns strengthened with high-performance ferrocement laminate (HPFL) and bonded steel plates (BSP) were analyzed on the basis of experiments on the axial compression performance of these columns. Results show that the reinforcing layer worked together with the original columns as a whole, and the load-bearing capacity significantly increased. When failure of the strengthened column occurred, the mortar and concrete were crushed and bulged outward in the middle of the columns, the angle bars and longitudinal steel bars buckled, and some stirrups were pulled out. The chamfering of angle bar momentously affected the primary damage of steel strand. The values of the strength reduction factor and pressure effective utilization coefficient of the mortar were suggested. Based on the experiments and existing tests of 35 columns strengthened with HPFL, equations for the axial compression bearing capacity were proposed and all calculation results agreed well with testing results. Therefore, the calculation method could be used in the capacity design of axial compression strengthened columns.