Xiaobin Song

This paper presents the results of a study on the mechanical behavior of concrete columns strengthened with fiber-reinforced polymer (FRP) and subjected to concentric and eccentric compression loading. A numerical analysis model was developed based on the effectively confined concrete area and the stress-strain relationship of the confined concrete established based on compression tests of circular plain concrete columns. The model was verified against the test results of square concentrically loaded plain concrete columns and square eccentrically loaded reinforced concrete columns. An analytical formula of the maximum compression load of square or rectangular fiber reinforced polymer strengthened concrete columns, with respect to the same but nonstrengthened columns, was developed based on the parametric study results by using the verified model. The analytical formula was further verified with the test results of 23 square and rectangular fiber reinforced polymer strengthened columns reported in the literature. Good agreement was achieved. It was found that the increase of the maximum compression load of FRP-strengthened concrete columns, with respect to the same but nonstrengthened columns, increases linearly with the amount of FRP sheets used and decreases linearly with the load eccentricity and exponentially with the concrete compression strength. The last observation implies that the FRP strengthening technique (through wrapping) is most suitable for low-strength concrete buildings.

This paper summarizes the results of an experimental study on the rotational behavior of bolted beam-to-column glulam connections reinforced using locally cross-laminated glulam members. Twenty-two full-scale connection specimens were tested through monotonic and reversed cyclic loading, from which the moment / rotational angle relationships were established. The results indicated that the cross-laminated technique leads to a more ductile failure mode with cross-aligned inner layers of laminas fractured, in contrast to the perpendicular-to-wood-grain tensile failure of unreinforced connections. The connection maximum moment was found to increase by 52% and 46% under monotonic and cyclic loading, respectively; moreover, the deformability ratio evaluated on the basis of the rotation angles corresponding to the yielding and maximum moments of the connections was increased by 94%. Locally cross-laminated connections were also found to dissipate more energy (25%) than unreinforced connections. A comparison of the cross-laminated technique with self-tapping screws indicated that the respective reinforcing effects were comparable with that of the screws being slightly higher. Because the locally cross-laminated technique is readily incorporated into the production of cross-laminated timber products, it may have broad applications in heavy timber-bolted connections.