Structural health monitoring is an important aspect of maintenance for bridge columns in areas of high seismic activity. In this project, recently developed piezoceramic-based transducers, known as smart aggregates (SA), were utilized to perform structural health monitoring of a reinforced concrete (RC) bridge column subjected to pseudo-dynamic loading. The SA-based approach has been previously verified for static and dynamic loading but never for pseudo-dynamic loading. Based on the developed SAs, an active-sensing approach was developed to perform real-time health status evaluation of the RC column during the loading procedure. The existence of cracks attenuated the stress wave transmission energy during the loading procedure and reduced the amplitudes of the signal received by SA sensors. To detect the crack evolution and evaluate the damage severity, a wavelet packet-based structural damage index was developed. Experimental results verified the effectiveness of the SAs in structural health monitoring of the RC column under pseudo-dynamic loading. In addition to monitoring the general severity of the damage, the local structural damage indices show potential to report the cyclic crack open-close phenomenon subjected to the pseudo-dynamic loading.

A model proposed in the literature for the evaluation of the in-plane shear capacity of unstrengthened and strengthened concrete and clay brick unreinforced masonry (URM) walls was modified and calibrated following the results from an experimental research program. The tested walls were strengthened with grids made from glass fiber-reinforced polymer (GFRP) embedded within a rapid-setting sprayed polyurea. Various GFRP grid reinforced polyurea layouts were investigated, and consisted of strips oriented in either the vertical or horizontal direction and installed on one or both faces. The prediction models proposed in this paper were subsequently evaluated using a probabilistic Monte Carlo simulation (MCS) by considering the uncertainty and variability of the independent variables, which were assumed to follow a truncated normal distribution. Corroborated by the MCS, test results clearly show that the failure modes of the strengthened URM walls were affected by the strengthening scheme. Experimental and si...

This paper presents the basis of a procedure to estimate the explosive charge weight and stand-off distance to impose certain levels of damage on reinforced concrete (RC) structures. A series of experiments were also conducted to confirm its applicability for assessing the blast resistance capacity of RC slabs. Test results showed that the procedure was accurate in predicting the explosive charge weight and stand-off distance to impose a given damage level on the tested RC slabs. This main conclusion was derived because a reasonable agreement was observed between the damage levels selected for assessment and the damage levels observed during testing.

This research investigates the feasibility of using prestressed glass fiber reinforced polymer (GFRP) bars for enhancing the in-plane shear strength of unreinforced masonry (URM) walls. In this application, URM walls were strengthened with prestressed GFRP bars by using the near-surface mounted reinforcement (NSM) technique. Prestressed GFRP bars would be used for repointing/closing wide open cracks in existing masonry structures. In total, eight URM walls were tested under in-plane diagonal compression. Experimental results validated the higher shear capacity of the strengthened URM walls and this increase was more pronounced for walls strengthened with prestressed GFRP bars. Furthermore, the calculated drift ratio in strengthened walls was considerably higher when failure was along stair-stepped diagonal cracks. Experimental results were used to modify and calibrate a theoretical shear friction model for predicting the in-plane shear capacity of strengthened URM walls with NSM prestressed GFRP bars. The model was capable of predicting reasonably well the shear capacity of strengthened URM walls.

The contribution of near-surface mounted (NSM) fiber-reinforced polymer (FRP) bars to the shear strength of unreinforced masonry (URM) walls built with concrete masonry units (CMU) was evaluated, and results are presented in this paper. This evaluation was achieved by reviewing test results from three types of research programs that were previously reported in the literature. Experiments were grouped as follows: (1) pull-out tests of NSM FRP bars embedded in CMUs, (2) pull-out tests of NSM FRP strips in clay brick prisms, and (3) in-plane diagonal compression tests of URM walls strengthened with NSM FRP bars/strips. Experimental results clearly indicate a significant difference in the failure mode observed between pull-out and in-plane diagonal tests, and statistically the maximum strains registered in NSM FRP bars/strips were significantly higher in pull-out type tests. Results from the pull-out tests were subsequently used to develop a bond stress–slip model for NSM FRP bars embedded in concrete masonry. Finally, the contribution of NSM FRP bars to the shear strength of concrete URM walls derived from different approaches is presented in this paper.

In this study, unreinforced masonry (URM) walls constructed from concrete blocks and clay bricks were strengthened using horizontally and vertically oriented glass fiber-reinforced polymer (GFRP) grid strips bonded with sprayed polyurea. The walls were subjected to diagonal compression loading until failure. The results demonstrated a significant improvement in both the shear capacity and pseudo-ductility of the strengthened URM walls compared to their unstrengthened counterparts. The primary conclusions drawn from this research are as follows: (1) the maximum strain in the vertical GFRP strips increased with the higher axial stiffness of the strips; (2) the discrete vertical strips contributed substantially to enhancing the shear capacity and pseudo-ductility of the URM walls; (3) increasing the axial stiffness of the vertical strips can alter the failure mode of the walls, shifting it from joint failure to tension or compression failure of the blocks or bricks; (4) a reduction factor is necessary to account for the potential asymmetrical performance of double-sided strengthening schemes applied to URM walls. The experimental program was reported in a previous publication and additional information is presented in this paper.