MECHANICAL PROPERTIES OF GYPSUM BOARD AT ELEVATED TEMPERATURES
Gypsum board is a common fire barrier used in house and general building construction. Recently, evaluation of the collapses of the World Trade Center Towers highlighted the potential role and failure of gypsum board in containing the fires and resisting damage. The use of gypsum board as primary fire protection of light-flame wood or steel construction is ubiquitous. Yet knowledge of the common engineering mechanical properties of this construction product is nearly nonexistent. Gypsum board is used in a prescriptive manner with little or no rational design. Summarized here are the results of a study examining the mechanical properties of Type X gypsum board at elevated temperatures. These properties are needed to contemplate the engineering design of gypsum board fire barriers. Tests were undertaken with a small oven within a test machine measuring mass loss, shrinkage, bending strength and modulus of elasticity at elevated temperatures to 400°C. The research showsthat shrinkage and calcination of the gypsum board appear complete between 20 to 30 minutes of exposure at a uniform 400°C. Only after complete calcination, where all moisture is driven off, does the bending strength approach 0. Strength appeared to decrease linearly with increasing temperature. Mass loss and modulus of elasticity exhibited similar trends with the greatest decreases occurring from 100°C to 200°C followed by more gradual decrease to 400°C. The surface paper plays significant stiffening and strengthening roles up to 60 minutes at temperatures as high as 200°C.
Computational Nonlinear Thermomechanical Model of Large Light Partition Walls Based on Experimental Analysis and Probabilistic Models
Abstract:  This article is devoted to the construction of a computational nonlinear thermomechanical model of large light partition walls made up of cardboard‐plasterboard‐cardboard (CPC) plates screwed to a metallic frame, and is submitted to mechanical and thermal loadings induced by fire. The computational model, based on experimental analysis and a probabilistic modeling, is developed for the prediction of a large light partition wall for (1) its linear thermal behavior, (2) its nonlinear mechanical behavior, and (3) its nonlinear thermomechanical behavior.
Modelling of heat and mass transfer in wood structures during fire
Abstract One fundamental prerequisite for analytical treatment of the design process for wood structures exposed to fire is the development of an analytical model for the essential physical process in heated wood material. The model must be capable of treating transient temperature and moisture states in both uncharred and charred portions of the cross-section, as well as the growth of the charred layer in combination with its oxidation at the surface due to variable thermal action. Material data for such a model must also be produced. The calculations in this work are based on the model developed by the author. Simulations have been made with the one-dimensional computer program WOOD1. The input data which have been varied in the calculations are the thickness, density, moisture content and thermal exposure of the material. These few and simple input data are of a type that are known in conjunction with a fire engineering design. The results of all calculations are presented in diagrams in which the three different calculated quantities have been set out as a function of the distance from the surface exposed to fire at different times. The presentation comprises temperature profile, density distribution and moisture profile. Assessment of the fire resistance of the board material is based on the same performance requirements as those set out in the internationally accepted test method, ISO 834, or its Swedish counterpart SIS 02 48 20. This implies for the calculations that the fire resistance is taken to be the time when the insulation requirement is no longer complied with, i.e. when the rise in temperature on the unexposed face exceeds 140°C. A comparison of the calculated fire resistances and those measured in the tests shows very good agreement. The maximum difference between the tests and the calculations is only about 1 min for boards. For the wall constructions the maximum difference is larger, but normally not more than 10 min.