Epoxy bonded fibre reinforced polymer (FRP) composites are widely used for the retrofit of ailing reinforced concrete structures, for both shear and flexure. The behaviour of retrofitted concrete structures is governed by the bond strength and the material characteristics of the epoxy bonded FRP and the concrete. Previous studies show that lightweight concrete (LWC), which uses Pulverised Fuel Ash (Lytag) instead of coarse granite aggregates, has significantly lower tensile strength and aggregate interlock compared to normal weight concrete. Performance of shear retrofitted concrete elements is primarily governed by the aggregate interlock and tensile strength. Thus the study of FRP enhancement techniques in LWC is paramount for limit state design. Many studies have been conducted to understand the bond-slip behaviour between normal weight concrete (NWC) and FRP composites, where the increasing interfacial (shear) and normal stresses with increasing plastic deformation lead to FRP debonding and/or FRP rupture failures. This paper presents the experimental pull-off test results obtained from lightweight concrete prisms with various configurations of epoxy bonded Carbon FRP (CFRP) sheets. The experimental results show that the LWC can successfully be applied in the strengthening of lightweight concrete structures. However, the lightweight concrete prisms failed due to a diagonal crack within the concrete materials. This was due to a lower tensile strength compared 2 to normal weight concrete specimens where peeling or rupture of FRP is the dominant failure mechanism.

Reinforced concrete structures may be vulnerable to progressive collapse due to lack of sufficient continuous reinforcement. In most guidelines, general structural integrity requirements to reduce progressive collapse have been introduced, but the design of structures against progressive collapse has not been a major consideration. A mitigation scheme is proposed to increase resistance against progressive collapse. This involves the provision of additional reinforcement bars in the mid-layer of reinforced concrete beams. In the research reported here, four specimens were designed and tested subject to quasi-static loading conditions for a column removal scenario. One test specimen was made with conventional steel reinforcement and three specimens were made with additional steel reinforcement at the mid depth of the beam. The quasi-static behaviour of the test specimens were converted to a dynamic representation using an energy balance approach to obtain the progressive collapse load. Test results show that the proposed scheme significantly improves the ductility and collapse load of concrete beams subject to a column removal scenario.

Ti t l eValid a tio n of a finit e el e m e n t m o d elli n g a p p r o a c h o n s oilfo u n d a tio n

This paper presents the experimental results obtained from lightweight and normal concrete beams with closed and U-shaped configurations of epoxy bonded Carbon FRP (CFRP) reinforcement in order to compare the shear resisting mechanisms between lightweight and normal concrete beams. The experimental results show that the CFRP can successfully be applied in the strengthening of lightweight concrete beams and the shear strength gained due to CFRP reinforcement for lightweight samples is less than the normal weight concrete samples while the mode of failures are the same. In contrast, diagonal shear cracks propagate through the lightweight aggregate compared to cracks around normal aggregate in the concrete matrix. Furthermore, the numerical study shows that the design guidelines to estimate the CFRP contribution, which do not differentiate the concrete types, overestimate the U-shaped CFRP contribution on lightweight concrete beams where the effective bond length of CFRP could not be achieved due to lower tensile strength of lightweight concrete.

The progressive collapse behaviour of reinforced concrete (RC) structures requires consideration of material and\ud geometric non-linearity, concrete crushing and rebar fracture. Compressive arch action (CAA) and catenary action\ud (CTA) are the main resisting mechanisms against progressive collapse following a column loss. Hence, many studies\ud have concentrated on the development of CAA and CTA in RC beams, but without considering the effect of bar\ud fracture and the reduction in beam effective depth due to concrete crushing. Taking these additional factors into\ud account, an analytical model to predict the structural behaviour of RC beams under a column removal scenario was\ud developed. The proposed model was evaluated and validated with the available experimental results. The evaluation\ud and validation indicate that the proposed model can provide a reliable assessment of RC beam capacity against\ud progressive collapse