Strengthening of new flat slab structures for progressive collapse

• Main Author: Yeo, Shaun Lee Shen.
• Other Authors: Li Bing
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Civil engineering::Structures and design
• Online Access: http://hdl.handle.net/10356/49041
• Institution: Nanyang Technological University

Explosions, vehicle collisions, and foundation failure are anomalous loading events not taken into consideration in typical structural designs. The localized damage resulting from these low-probability loads may propagate to a sequential reaction of structural element failure that may eventually lead to a partial or full collapse of a structure, otherwise known as progressive collapse. The Ronan Point Tower collapse in London in 1968 and the Alfred P. Murrah Fedural Building collapse in Oklahoma City in 1995 have both established the catastrophic consequences of a progressive collapse resulting from extreme loading events. Accommodating the initial local damage and developing an alternative load-path to sustain the redistributed loads are characteristics a structure must exhibit in the event of such extreme loadings. Recent years has seen many noteworthy laboratory experiments involving the studied response of a beam-column substructure when subjected to a scenario loss of an interior or exterior column. Interestingly, the loss of a corner column in an act of terrorism is more likely to induce a progressive collapse as compared to the scenario loss of an interior column, with the latter relying on lesser secondary resistant branches such as catenary and membrane action to mitigate the effect of progressive collapse. In addition, flat slabs are more susceptible to progressive collapse in comparison to two-way slabs. Having understood the disastrous effects of a structural progressive collapse, it is of utmost importance that practicing engineers take into account the effects of progressive collapse in any structural design. However, limited related experimental and analytical studies pertaining to the strengthened performance of reinforced concrete flat slabs when subjected to a corner column loss scenario have been conducted. For this very purpose, this Final Year Report study investigates four flat slabs with top reinforcement continuity and varying slab reinforcement ratio pertaining to the strengthened performance of new RC flat slab structures for progressive collapse. The test results indicated that punching failure in the lost corner column region and diagonal flexural failure on the top slab passing through both adjacent enlarged columns were two major failure mechanisms. By increasing the amount of reinforcement in a slab, there is an increased in loading corresponding to the first yield of the top reinforcement and peak capacity achieved by 50% and 60% respectively. However, there is little increase of 8% in the loading corresponding to the attainment of tensile membrane action. Further ensuring the continuity of top reinforcement increases the loading corresponding to the first yield of the top reinforcement and peak capacity achieved by 40% and 33% respectively. There is also a significant increase of 50% in the loading corresponding to the attainment of tensile membrane action. A companion study on the strengthened performance of existing RC flat slab structures for progressive collapse is conducted by a fellow FYP student.