BS/EN 15269-11-2018 pdf download.Extended application of test results for fire resistance and/or smoke control for door, shutter and openable window assemblies, including their elements of building hardware Part 11: Fire resistance for operable fabric curtains.
Curtain systems are different from typical door systems due to their not rigid closure element typically made of thin walled materials as for instance woven or knitted fabrics and foils. These closure elements are not able to carry significant loads normal to their surface (e.g. caused by pressure load) due to their characteristic lack of bending stiffness. That’s why it is assumed that curtain systems can only conduct tensile forces by tensile stress in-plane to their surface. It is assumed that compressive forces are not conducted in-plane to their surface.”
It is assumed that the stresses In the fabric curtain can be approximated by a model of a thin-walled sphere under inner pressure where the stresses follow the vessel formula.
To be able to calculate scaling possibilities of textile assemblies in a consistent and handy way, the assemblies are reduced to a simplified model as EXAP calculation basis, For curtain assemblies having a modular overlapping closure element or a system without a retaining system at the side guides it is assumed that the loads on the textile curtain being caused by pressure are mainly carried in vertical direction by the weight or the lifting force of the fabric and the bottom bar.
Due to the practical limitation in dimensions of full scale fire tests according to EN 1634-1 overlapping modular assemblies are limited within this scope to a maximum of three modules and two overlapping zones.
C.2 Calculation principles
The general methodology for checking the proposed specifications is based on accepted engineering first principles which may be modified only in accordance with adjustments given in the following clauses.
The values for material properties such as Young’s Modulus shall be taken from EN 1993-1-2:2005 for temperatures measured for the load bearing components at the required classification time. II temperatures of components have not been measured then the furnace temperature according to EN 1363-1 at the required classification time shall be used unless otherwise stated.
C.3 Calculation method increasing curtain width and height
Up scaled systems have to be constructed so that as a minimum requirement the integrity of the curtain is guaranteed in case of fire. Due to the fact that in case of fire the curtain is not only exposed to very high temperature but also to variable and high pressure, the deflection behaviour of the pressurized curtain needs special attention in order to predict the behaviour of a up scaled system.
The main components of a fire curtain are its casing, barrel, curtain, bottom bar and side guides. The fabric is held at its edges into a more or less stable position by at least some of these components. Because the textile curtain on its own is a deflectable membrane clamped between its edges, it forms when pressurized a shape mainly defined by the degree of freedom of its edges.
As a result from this modelling method up scaled modular systems or closed systems without side guides or retaining system have to be able to carry higher loads, especially in vertical direction, to withstand the higher pressure load. Therefore they need especially sufficient bottom bar or curtain weight, sufficient form stability of the coiling mechanism and its supports, as well as sufficient vertical tensile strength of the fabric to balance the vertical lifting force caused by the pressurized curtain.
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BS EN 15269-11:2018
EN 15269-11:2018 (E)
While modular systems or systems without retaining system in the side guides do not carry significant load in horizontal direction according to the calculation model they do not need overcapacity of fabric strength or additional strength of side guides for up scaling in horizontal direction. The overcapacity in the curtain components needed for up scaling in vertical direction are determined in a small scale fire tests as defined in Figure A.8.
Shrinking of curtain material during a fire test may change the theoretical bow length and radius of the curtain shape resulting in failure of an up scaled system due to increased tensile tension inside the fabric and the casing or lifting of the bottom bar. Therefore the shrinkage of the curtain has also to be determined.
— In a first step the shrinking of the curtain material is calculated based on measurements during full scale fire test according to C.5.
— In a second step the vertical bow shape of the approved up scaled curtain is calculated based upon the vertical textile slack from which fallows the vertical pulling force and the stress in vertical direction according to C.6.
— In a third step the horizontal bow shape of the approved up scaled curtain is calculated from which follows the necessary horizontal textile slack in horizontal direction according toC7.
— In a fourth step the calculated stress is compared to the maximum stress which was measured in the additional small scale test for vertical direction according toC.8.
— In a fifth step the overlapping zone and end modules are scaled according toC.9.BS/EN 15269-11-2018 pdf download.