Strengthening flat slabs at corner columns against punching shear using fibre reinforcing polymer (FRP)

UoM administered thesis: Phd

  • Authors:
  • Bassam Abdulrahman

Abstract

Using Fibre Reinforcing Polymer (FRP) composites for strengthening and rehabilitation of reinforced concrete structures has been a viable technique for more than two decades. Strengthening by FRP composites is often preferred to other strengthening techniques like steel plates due to the former’s special features, for example, it is lightweight, non-corrosive, easy to install, has high tensile strength, and its use results in only minimal changes to the external appearance of the structure. Additionally, the labour costs are lower when using this material. The main objectives of this study are: (1) to investigate the punching shear behaviour of slabs at corner column connections strengthened by externally bonded FRP sheets using both modelling and experimental methods. The study concentrates mainly on slabs without shear reinforcement that fail initially due to punching shear; this is in order to enhance their serviceability and ultimate loading capacity; (2) to investigate slabs at corner column connections with openings; and (3) to increase understanding of the behaviour of such slabs and provide recommendations for strengthening. None of the current standards’ specifications - like the ACI-440, Concrete Society Technical Report TR55 and the Japanese Society of Civil Engineers JSCE - give the required information for the design of concrete slab-column connections to withstand punching shear. Furthermore, all the previous studies about the strengthening of slab-column connections have dealt with interior columns; none have investigated the strengthening of slabs at the corner column. Thus, this study is the first to investigate, both experimentally and numerically, the effectiveness of strengthening slabs at the corner column connection by using carbon fibre reinforcing polymer (CFRP) sheets. The experimental programme comprises casting and testing four full-scale slabs that have been designed and fabricated in order to simulate exterior slab-column connections. One of them is the control specimen, which has been designed without any opening or strengthening. One is similar to the control specimen but strengthened by CFRP sheets around the corners. The last two slabs are designed similar to the control specimen but they have openings close to the column. In addition to the openings, they are strengthened by CFRP sheets. In addition to the experimental programme, three-dimensional nonlinear finite element models have been developed and validated against the experimental results. The comparison between the experimental and the numerical results is based on deflections, ultimate punching shear capacity, total strains of steel and CFRP reinforcements, crack pattern and the failure mode. Results are also compared to the Eurocode 2, ACI and the JSCE to predict the punching shear strength. It is concluded that bonding CFRP sheets to strengthen a slab at the corner column can increase both the serviceability and the ultimate strength by (11-21) % depending on the slab size. This limited increase is associated with the small thickness of the CFRP sheets used in the study, which means that there is only a small CFRP area resisting the tensile stresses; CFRP with a small width is used due to the practical constraints.

Details

Original languageEnglish
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Award date1 Aug 2018