Sanin Dzidic

By Sanin Dzidic

A fire can happen anytime and anywhere. That is why the fire resistance of our structures is important. Adequate fire resistance enables the evacuation of people and material goods, fire-fighting intervention, but also the possibility of reusing the building after the fire with minor or major retrofitting works. Our structures are made of different construction materials, and these materials behave differently in fire conditions, while we build our structures to last 50, 100, or 200 years. That is why the selection of structural and other construction materials is extremely important. Concrete is not combustible, does not transmit flame, does not release toxic gases in a fire and is not a fire load. However, fire has a negative impact on concrete structures as well, especially since concrete is a composite material, so there is a reduction in the mechanical properties of both concrete and the embedded steel. The most sensitive reinforced concrete elements in a fire situation are thin-walled elements such as RC slabs, which have a thin concrete cover. In this research, using four world famous methods, we try to figure out the factors influencing the fire resistance of RC slabs as the most sensitive reinforced concrete elements to fire.

Part of the book: Reinforced Concrete Structures

By Sanin Dzidic and Aldin Mahmutovic

The design of concrete structures and elements in Europe and wider is conducted according to EN 1992-1-1. Among other design assumptions, the Eurocode 2 assumes the design value of the modulus of elasticity E_s of reinforcing steel to be 200 GPa. However, what happens in the RC beam if the actual modulus of elasticity is significantly reduced. Does it affect the flexural bearing capacity of RC beam and to what extent? Another logical question is how to determine the actual flexural bearing capacity of the RC beam reinforced with reinforcing steel with a reduced modulus of elasticity and which design model to use for such determination. This study tries to answer such questions using an experimental approach and assumed calculation model with a comparison of experimental and calculation results. The experimental research from this showed that test RC beams reinforced by steel with reduced modulus of elasticity have significantly reduced flexural capacity in comparison with the designed flexural capacity of beams reinforced by steel with “normal” modulus of elasticity. In this regard, it is recommended to test the mechanical properties of the steel reinforcement prior to the installation at the site and not to rely on the producer’s factory production control certificate only. Additional issues considered in this research are observed effects of the reduced modulus of elasticity of reinforcing bars to Serviceability Limit States (stress limitation, crack width, and deflection control). Answers to such questions can inform decisions if retrofit is needed, is it feasible and if yes—which retrofit method to be used. This study does not discuss the reasons for the reduced modulus of elasticity in reinforcing steel.

Part of the book: Advances in Structural Integrity and Failure