Solid concrete slabs are very important structural members in building and construction because traditional slabs reinforced with steel carry the load and transfer it to the beam. However, steel reinforcement corrodes, which affects the integrity of concrete structures by reducing their strength and serviceability, thus leading to failure. For this reason, non-corrosive Glass Fibre Reinforced Polymer (GFRP) bars are an effective alternative reinforcement in concrete slabs. Moreover, concrete slabs are very heavy and make up a high percentage of the dead load in a building structure; this in turn means that more concrete is needed. There is therefore a crucial need for lighter slabs with a better structural performance and this can be provided by Hollow Core Slabs (HCS). However, HCS slabs contain internal voids which cause premature shear failure and the walls to collapse. In response, a hollow Composite Reinforcing System (CRS), with four flanges to improve their bond to concrete, has been developed to stabilise the voids in concrete members. This study investigates the flexural behaviour of concrete slabs reinforced with FRP bars and CRS. Four slabs (a solid slab reinforced by GFRP, a hollow slab reinforced by GFRP, a slab reinforced by GFRP and CRS, and a slab reinforced by steel and CRS) were tested under fourpoint static bending to better understand the structural performance of this new construction system. The results proved that solid and hollow slabs behaved similarly due to the voids located in the areas under compressive stress, and that CRS enhanced the structural performance of hollow core concrete slabs by 85%, while the stiffness of GFRP reinforced hollow slabs and the load carrying capacity increased by 32%. CRS was found to be more compatible with GFRP bars than steel bars due to their similar modulus of elasticity. A theoretical evaluation of the behaviour of concrete slabs reinforced with GFRP bars and CRS using the Fibre Model Analysis was also carried out. This FMA considered the tensile strength of concrete and the flanges of CRS, and found that the predicted failure load was only 13% less than the failure load measured experimentally. Important parameters such as the number of voids, the compressive strength of concrete, and the reinforcement ratio were also analysed with regards to the overall behaviour of the slabs. The results of this study provide useful information for the construction industry on the structural performance of concrete slabs utilising CRS and for the effective and safe design of such a construction system. ii Certification of Thesis This Thesis is entirely the work of Mohammed Baqer Ahmed Al-Rubaye except where otherwise acknowledged. The work is original and has not previously been submitted for any other award, except where acknowledged.
Hollow concrete columns (HCCs) constitute a structurally efficient construction system for marine and offshore structures, including bridge piers and piles. Conventionally, HCCs reinforced with steel bars are vulnerable to corrosion and can lose functionality as a result, especially in harsh environments. Moreover, HCCs are subjected to brittle failure behavior by concrete crushing due to the absence of the concrete core. Therefore, this study investigated the use of glass fiber-reinforced polymer (GFRP) bars as a solution for corrosion and the use of hollow composite-reinforced sections (HCRSs) to confine the inner concrete wall in HCCs. Furthermore, this study conducted an in-depth assessment of the effect of the reinforcement configuration and reinforcement ratio on the axial performance of HCCs. Eight HCCs with the same lateral-reinforcement configuration were prepared and tested under monotonic loading until failure. The column design included a column without any longitudinal reinforcement, one reinforced longitudinally with an HCRS, one reinforced longitudinally with GFRP bars, three reinforced with HCRSs and different amounts of GFRP bars (4, 6, and 8 bars), and three reinforced with HCRSs and different diameters of GFRP bars (13, 16, 19 mm). The test results show that longitudinal reinforcement-whether GFRP bars or HCRSs-significantly enhanced the strength and displacement capacities of the HCCs. Increasing the amount of GFRP bars was more effective than increasing the bar diameter in increasing the confined strength and the displacement capacity. The axial-load capacity of the GFRP/HCRS-reinforced HCCs could be accurately estimated by calculating the load contribution of the longitudinal reinforcement, considering the axial strain at the concrete peak strength. A new confinement model considering the combined effect of the longitudinal and transverse reinforcement in the lateral confinement process was also developed.
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