Probabilistic Study of the Resistance of a Simply-Supported Reinforced Concrete Slab According to Eurocode Parametric Fire

Mohammad Heidari,Fabienne Robert,Guillermo Rein,David Lange

doi:10.1007/s10694-018-0704-4

Abstract

We present the application of a simple probabilistic methodology to determine the reliability of a structural element exposed to fire when designed following Eurocode 1-1-2 (EC1). Eurocodes are being used extensively within the European Union in the design of many buildings and structures. Here, the methodology is applied to a simply-supported, reinforced concrete slab 180 mm thick, with a standard load bearing fire resistance of 90 min. The slab is subjected to a fire in an office compartment of 420 m2 floor area and 4 m height. Temperature time curves are produced using the EC1 parametric fire curve, which assumes uniform temperature and a uniform burning condition for the fire. Heat transfer calculations identify the plausible worst case scenarios in terms of maximum rebar temperature. We found that a ventilation-controlled fire with opening factor 0.02 m1/2 results in a maximum rebar temperature of 448°C after 102 min of fire exposure. Sensitivity analyses to the main parameters in the EC1 fire curves and in the EC1 heat transfer calculations are performed using a one-at-a-time (OAT) method. The failure probability is then calculated for a series of input parameters using the Monte Carlo method. The results show that this slab has a 0.3% probability of failure when the compartment is designed with all layers of safety in place (detection and sprinkler systems, safe access route, and fire fighting devices are available). Unavailability of sprinkler systems results in a 1% probability of failure. When both sprinkler system and detection are not available in the building, the probability of failure is 8%. This novel study conducts for the first time a probabilistic calculation using the EC1 parametric curve, helping engineers to identify the most critical design fires and the probabilistic resistance assumed in EC1.

Highlights

Performance based design for fire has been incorporated into legal frameworks around the world [1] and allows designers to employ a rational engineering approach to the provision of fire safety in the built environment [2].The fundamental principles of performance based fire engineering for structures are outlined in multiple guidance codes [3, 4]
The work applies a simple, but powerful, structured methodology to: (1) identify the most important parameters that need to be considered during fire safety engineering, and (2) to determine the reliability of a structural element exposed to fire when designed following Eurocode 1-1-2 (EC1)
The methodology was applied to a -supported reinforced concrete slab 180 mm thick; with a standard load bearing fire resistance of 90 min; subjected to a fire in an office building compartment of 420 m2 floor area and 4 m height

Summary

Introduction

Performance based design for fire has been incorporated into legal frameworks around the world [1] and allows designers to employ a rational engineering approach to the provision of fire safety in the built environment [2]. The fundamental principles of performance based fire engineering for structures are outlined in multiple guidance codes [3, 4]. Designers should define the input variables required for design using any number of sources. This can lead to a significant variability in the design fires used, and inconsistent levels of safety for buildings [5]

Methods

Results

Conclusion