Description
A Master of Science thesis in Civil Engineering by Haider H. Hasan entitled, “Shear Behavior of One-Way Reinforced Concrete Hollow Slabs Voided with PET Void Formers”, submitted in May 2023. Thesis advisor is Dr. Sami Tabsh. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Abstract
In residential reinforced concrete structures, the slab constitutes the largest concrete volume. Reducing its concrete content leads to significant cost savings and environmental benefits. Furthermore, Polyethylene Terephthalate (PET) bottles, which account for approximately 22% of all plastic packaging products globally, are non-biodegradable and release toxic chemicals when buried in landfills or incinerated. This research aimed to evaluate the structural and construction feasibility of utilizing PET bottles as void formers in slabs. Previous studies lacked comprehensive investigations into the use of PET bottles as void formers and their effects on slab’s shear performance. To accomplish this study’s objectives, 13 full-scale, shear critical reinforced concrete one-way slabs with a width of 600 mm were tested under a 3-point loading configuration at AUS. The experimental program featured varying concrete compressive strengths (30 and 50 MPa), steel reinforcement ratios (0.66, 0.88, and 1.4%), presence of top steel layer, slab thicknesses (180 and 230 mm), shear span-to-effective depth ratios (1.49, 2.97, and 3.95), and void percentages (0, 17, 22, and 29%). In addition to the experimental investigation, theoretical studies were conducted to predict the shear strength using North American and European structural design codes. A novel analytical shear strength model was developed, and its accuracy was validated using a dataset of 55 slabs from various researchers. The findings indicated that voided to solid shear strength ratios ranged between 0.61 and 1.04, while shear stress ratios varied between 0.82 and 1.29. Voided slabs demonstrated comparable overall behavior without displaying drastic decrease in ductility. The compressive strength and reinforcement ratio had less pronounced effect on increasing the strength of voided slabs. Void percentage alone was not a suitable metric for evaluating the shear strength, as beyond a certain percentage, the influence of void area on shear strength diminished. The proposed model prediction ratios were within 10% of the experimental results, indicating good agreement and outperforming design codes like ACI 318, BS 8110, and Eurocode 2 prediction ratios, which deviated by more than 100%. By optimizing design parameters and employing precise analysis procedures, the performance of voided slabs can be enhanced, resulting in efficient and cost-effective structures.