Publications

This study investigates the influences of three types of locally available low-cost Fiber Reinforced Polymers (FRP) wraps and two concrete mix designs on the axial behavior of FRP confined concrete. The experimental program comprised four unconfined (control), four glass FRP Matt Strand (GFRP-MS) confined concrete, four glass FRP Rowing (GFRP-R) confined concrete and four carbon FRP (CFRP) confined concrete specimens with a diameter of 150 mm and a height of 300 mm tested under axial compression. The specimens were prepared using two normal strength concrete mix designs, i.e., Mix-A and Mix-B. The experimental results exhibited that an increase in the confined concrete strength per unit cost ratio of a single layer of GFRP-MS was about two times of a single layer of CFRP wrap, whereas the increase in confined concrete strength per unit cost ratio of single layer of GFRP-R was about four times of a single layer of CFRP wrap. GFRP-MS and GFRP-R wraps can exhibit similar confined strengths as CFRP wrap with six and twelve times lower costs, respectively, than CFRP wrap. Mix-B concrete specimens exhibited higher confined concrete strengths but lower confined concrete strain than Mix-A concrete specimens. A database of 140 FRP confined concrete specimens was developed based on a set of specific criteria to develop a design-oriented model to predict the FRP confined concrete strength. The predicted confined concrete strengths matched well with the experimental confined concrete strengths. The two layers of GFRP-R exhibited similar confined concrete strength as CFRP wrap. In addition, GFRP-R exhibited high cement strength index (CSI) and low embodied CO2 index (CI).

Sulfate ions in saltwater can considerably deteriorate the strength and durability of reinforced concrete (RC). To date, there has been no study that systematically investigates the effects of a sulfate attack on the capacity of mid-/large-scale RC columns confined with carbon fiber–reinforced polymer (CFRP). The capacity of CFRP-confined concrete columns subjected to sulfate attacks with various schemes and durations (up to 210 days) was examined in this study. The primary objectives of this study were to (1) examine the effect of a sulfate attack on the structural properties of midscale RC columns confined with CFRP; (2) quantify the contribution of the sulfate-damaged concrete core and CFRP confinement to the load-carrying capacity of the columns; and (3) propose a new formula to estimate the compressive strength of FRP-confined sulfate-damaged concrete considering the exposing time, number of FRP layers, and concrete strength. The experimental results showed that the sulfate attack significantly reduced the initial axial stiffness of the column up to 36% and increased its ultimate axial displacement up to about 40%. These influences in the CFRP-strengthened columns were slightly lower than those of unstrengthened ones. The sulfate attack considerably reduced the strength of the unstrengthened columns (up to 29.4%), but it only slightly affected the capacity of the strengthened columns with a 3.7% reduction. The strength reduction increased with the number of wet–dry cycles. CFRP confinement effectively mitigated the penetration of sulfate ions into the concrete core and, thus, slowed the degradation of the strength up to 90%. An empirical formula was proposed to estimate the strength of the CFRP-confined concrete subjected to a sulfate attack with close predictions regarding the experimental results.

This paper presents the findings from the experimental programme and Finite Element (FE) analysis performed to study the behaviour of polyurea coated RC panels subjected to blast effects. The overall findings of the research, including detailed experimental findings of three of the tested panels (one un-retrofitted and two polyurea coated panels), and the subsequent FE analysis performed to simulate the blast trials, are discussed in this paper. All 3 panels had dimensions of 1700 (L) x 1000 (W) x 60 (T) mm. Among the retrofitted panels, one panel was subjected to a 4mm polyurea coating on the non-blast facing face, whereas the other was coated with a 4 mm polyurea coating on both faces. All the panels were subjected to blast loads resulting from the detonation of 1.0 kg Ammonite charge placed at a 1.0m stand-off. Identical panels were then modelled and analysed using the explicit solver of the non-linear FE code, LS-DYNA. The results from both experimental programme and FE analysis suggest that while the polymer coating technique does enhance the resistance of the RC panels to the applied blast load, a higher level of protection is provided when the protective coating is applied on the blast facing face of the structure. © 2014 Taylor & Francis Group.