Fire resistance of reinforced concrete columns with structural fire retardance

PURPOSE. One of the significant requirements for buildings and constructions is providing fire safety, which includes standardization of building structures fire resistance. The experience in applying thin-walled elements has shown high efficiency, technological and operational advantages. Bearing significant power loads, reinforced concrete columns often have low fire resistance (R30... R60), which poses certain risks in case of fire and limits their application in construction industry. To increase structures fire resistance, structural fire retardance is applied. The purpose of this work is to set the fire resistance limits of reinforced concrete columns protected by non-combustible Knauf Fireboard gypsum slabs of various thicknesses on a steel frame and obtain the generalized tabular data based on this research. METHODS. Model fire tests of spun reinforced concrete columns with structural fire retardance have been carried out, as well as simulation of heating a series of hollow and solid section reinforced concrete columns with structural fire retardance in ANSYS finite element analysis system. FINDINGS. Experimental data have been obtained on heating spun reinforced concrete columns of an annular section with an external diameter of 560 mm with a wall thickness of 55 mm and a protective concrete layer thickness of 20 mm for longitudinal reinforcement (12 mm diameter) protected by non-combustible Knauf Fireboard gypsum slabs with 12.5 mm, 20 mm and 40 mm thickness on a steel frame, and unprotected ones (without applying a power load). ANSYS finite element analysis system design models have been developed and the heating of a series of spun annular sections and vibration-compacted solid sections of reinforced concrete columns protected by structural fire retardance have been simulated. For these structures, fire resistance ratings have been calculated at a load-bearing capacity utilization factor of 0.7. Based on a certain array of values of fire resistance limits of reinforced concrete columns, tabular data have been obtained to assess the fire resistance of these structures with structural fire retardance. RESEARCH APPLICATION FIELD. The obtained results can be applied by design bureaus, state fire supervision authorities and state construction expertise in assessing fire resistance ratings of reinforced concrete spun columns of annular section and vibration-compacted solid section protected by structural fire retardance as well as in selecting parameters for these structures that provide specified fire resistance rating without carrying out a series of time-consuming calculations. CONCLUSIONS. Fire tests combined with simulation in ANSYS finite element analysis system make it possible to carry out a lot of calculations and obtain tabular data on assessing fire resistance of reinforced concrete columns with structural fire retardance which significantly reduces labor costs at designing building structures.