PSI - Issue 64

Ravina Sriram et al. / Procedia Structural Integrity 64 (2024) 2051–2058 R. Sriram/ Structural Integrity Procedia 00 (2019) 000–000

2052

2

1. Introduction Flat slab systems are constructed in many parking structures and multi-story office buildings enabling improved layout flexibility and simpler construction execution. However, a major drawback of these systems is their vulnerability to punching shear failure — a brittle failure mechanism that occurs when a concentrated load is applied on a small area (e.g. columns, wall ends). This failure mode often occurs unexpectedly and leads to severe structural damage (Arslantürkoglu & Bärtschi, 2017). Due to increased loading, design and construction deficiencies, or long term degradation of the structural system, many existing structures do not comply with the existing codes and thus need to be retrofitted. There are several techniques for retrofitting flat slab systems against punching shear failure, which can generally be classified based on their intent to increase the slab thickness, enlarge the support area, increase the flexural capacity, increase/introduce shear reinforcement, reduce the acting loading, or a combination of them. Some examples of such systems that have been successfully employed by Baertschi Partner Bauingenieure AG are, (i) prestressed steel frames as support structures (Figure 1), (ii) enlarged column heads and/or increased slab thicknesses with concrete or steel constructions (Figure 2), or (iii) increased reinforcement to the sagging and/or hogging moment regions.

Figure 1: Examples of strengthening against punching shear failure with prestressed steel support frames.

Figure 2: Examples of strengthening against punching shear failure with enlarged column heads and slab thicknesses.