Erich Hugi

Gypsum Board in Fire — Modeling and Experimental Validation

The thermal behavior of a commercially widespread gypsum board (810 kg/m 3) under fire condition has been investigated. For this purpose two 12 mm thick gypsum boards are subjected to the standard fire ISO 834 and the temperature distribution within them is measured by means of thermocouples placed at different depths in the samples. The results hereof are used to validate a numerical model based on the density, thermal conductivity, and effective heat capacity of the gypsum board as functions of temperature. The effects of dehydration/calcination and decomposition on these properties are determined by using thermogravimetric analysis, conductivity measurements after different heat treatments, and differential scanning calorimetry under air flow, respectively.

Four Types of Gypsum Plaster Boards and their Thermophysical Properties Under Fire Condition

Four different commercially available gypsum plaster boards are investigated experimentally at fire temperatures with respect to their thermophysical properties i.e., thermal conductivity, effective heat capacity and density. It is shown that depending on different ingredients (carbonates) different endothermic reactions occur between room temperature and 900°C. These reactions strongly influence the temperature dependence of the mentioned properties which in turn affect the response of the material to fire. Based on these experimental results the thermal reaction of a gypsum-protected steel column in fire is modeled for the four types of gypsum. The results of numerical simulations demonstrate clearly the advantages caused by certain ingredients of the chemical composition of gypsum plaster boards.

Vapor Convection in Gypsum Plasterboard Exposed to Fire: Numerical Simulation and Validation

This article investigates the contribution of water vapor convection to heat transfer through gypsum plasterboard exposed to fire. The vapor is generated as a product of the endothermic dehydration reaction in gypsum, and it is then expelled from the material through the pore network by its own pressure, thereby taking part in the heat transfer from the fire-exposed to the cold surface of plasterboard. The gas permeability values of plasterboard core and paper liner are obtained experimentally. The results of simulations are validated against the temperature measurement data obtained for two types of commercial plasterboard tested in the standard fire ISO 834. It is shown that vapor convection plays an essential role in heat transfer through plasterboard during the initial stage of fire. The amount of condensate developing in the pores of the material is found to be low, which allows it to be neglected in engineering calculations.

Fire Behavior of Thin CFRP Pretensioned High-Strength Concrete Slabs

More sustainable precast concrete structural elements are emerging from the research community utilizing high-strength, self-consolidating fiber-reinforced concrete (HPSCC) reinforced with noncorroding prestressed carbon-fiber-reinforced polymer (CFRP). An example of this is a new type of precast CFRP pretensioned HPSCC panel intended as load-bearing beams or columns for use in building envelopes. Such elements have recently been applied to architectural facade elements in Europe. A key issue in the implementation of these elements as load-carrying members in buildings is demonstrating satisfactory performance in fire. It is well known that the bond between FRP reinforcing bars and concrete deteriorates at elevated temperatures. It is also known that high-strength concrete is susceptible to explosive spalling when subjected to fire. Reductions in FRP reinforcement tensile and bond strength during fire, effects on the load-bearing capacity of prestressed concrete structures, and the explosive spalling response of HPSCC during fire all remain largely unknown. This paper provides insights into the fire behavior of CFRP prestressed HPSCC slabs through an experimental study on thin slabs exposed to a standard fire while subjected to sustained service loads. It is shown that the fire resistance of these elements is governed by fire-induced spalling or, if spalling is prevented by the use of high dosages of polypropylene microfibers in the concrete, by thermal splitting-crack-induced bond failure of the CFRP tendons in their prestress transfer zone. Neither reductions in tensile strength of the tendons nor reductions in bond strength due to resin softening at high temperature appeared to play critical roles for the tests described in this paper. Key areas for future research are highlighted.

Correlation between charring rate and oxygen permeability for 12 different wood species

The charring rates of 12 different wood species originating from Europe and the tropics with densities ranging from 350 to 750kg/m3 were investigated to obtain clues on their fire resistance behavior. This was done by measuring the thickness of the charred layer after a 30-min exposure to the standard fire ISO 834-1. No correlation was observed between charring rate and density. In search of another physical property that could be used as an indicator of fire resistance, the oxygen permeabilities of the selected wood types were measured. A strong correlation between oxygen permeability perpendicular to the wood fiber direction and charring rate was found, which is quite straightforward given that oxygen is the necessary component to enable smoldering and ignition, both affecting the charring rate. It seems that oxygen permeability is potentially more suitable as a parameter to evaluate the fire resistance of char-sensitive wooden constructions, rather than density. No general preference of the tree ring orientation from 0° (tangential) to 45° and 90° (radial) was found for these measurements.

Experimental Analysis of the Fire Behavior of Finger-Jointed Timber Members

AbstractFire design models for timber structures usually consider both the loss in cross section attributable to charring and the temperature-dependent reduction of strength and stiffness of the uncharred residual cross section. For bonded timber elements such as glued laminated timber beams, it is assumed that the adhesive in use does not significantly influence the resistance of structural timber beams. To investigate the influence of adhesives in bonded timber elements, a comprehensive research project is currently in progress. The aim of this project is the development of a simplified design model for the fire resistance of bonded structural timber elements, taking into account the behavior of the adhesive at elevated temperature. The paper presents the results of an extensive test series on finger-jointed timber members loaded in tension and exposed to a transient ISO 843 standard fire. The fire tests were performed with different adhesives that fulfill current approval criteria for the use in load-b...

Investigation of heat transfer in gypsum plasterboard exposed to fire for three nominal fire scenarios

The present article is concerned with modelling of heat transfer through a plasterboard panel exposed to fire. Two commercial plasterboard materials are tested for three nominal fire scenarios in a certified furnace, and the obtained temperature measurements are used to test and to validate a numerical model of plasterboard developed recently by Shepel et al. with the ultimate goal of exposing the model to a wider range of fire conditions. Overall, the agreement between the obtained numerical predictions and experimental data is found to be good. Some discrepancies observed at the early and late stages of the dehydration reaction are shown to be caused by the high local heating rate of the material during those stages.

Fire resistance tests on timber beam-to-column shear connections

Purpose This paper aims to present the results of an extensive experimental programme on the fire behaviour of timber beam-to-column shear connections, loaded perpendicularly to the grain. Design/methodology/approach The experimental programme comprised tests at normal temperature and loaded fire resistance tests on beam-to-column connections in shear. Twenty-four full-scale tests at normal temperature were performed covering nine different connection typologies, and 19 loaded fire resistance tests were conducted including 11 connections typologies. Findings The results of the fire resistance tests show that the tested typologies of steel-to-timber dowelled connections reached more than 30 and even 60 minutes of fire resistance. However, aspects such as a wider gap between the beam and the column, reduced dowel spacing, and the presence of reinforcement with self-drilling screws all have a negative influence on the fire resistance. Originality/value The experimental programme addressed the fire behaviour of timber beam-to-column shear connections loaded perpendicularly to the grain in a systematic way testing a wide range of common connection typologies significantly enlarging their experimental background.

Fire Performance of Water-Cooled Cellular GFRP Columns

Structural fire endurance experiments were conducted on full-scale cellular glass fiber reinforced (GFRP) columns under axial compression and subjected to ISO 834 fire exposure from one side. Unprotected columns could resist fire for more than 30 min, which is sufficient for occupants to be evacuated from smaller buildings. The closed cellular cross section prevented the rapid heating of the webs, which could therefore continue stabilizing the face sheet on the cold side against buckling. Water cooling was proved to offer an effective active fire protection system. The structural function of the column could be maintained for two hours. Previously developed models were capable of predicting the time-dependent temperature responses, modulus degradation and time-to-failure.