Filtern
Erscheinungsjahr
Dokumenttyp
Sprache
- Englisch (15) (entfernen)
Referierte Publikation
- ja (15) (entfernen)
Schlagworte
Organisationseinheit der BAM
A systematic approach was used to investigate the weathering-induced degradation of a common water–based intumescent coating. In this study, the coatings are intended for humid indoor applications on steel substrates. The coating contains ammonium polyphosphate, pentaerythritol, melamine, and polyvinyl acetate. By replacing each ingredient with a less water-soluble substance, the most vulnerable substances, polyvinyl acetate and pentaerythritol, were identified. Furthermore, the weathering resistance of the system was improved by exchanging the ingredients. The coatings were stressed by artificial weathering tests and evaluated by fire tests. Thermogravimetry and Fourier-transform infrared spectroscopy were used to study the thermal decomposition. This study lays the foundation for the development of a new generation of water-based intumescent coatings.
The phenomenon of creep of structural steel in fire engineering is gaining more and more interest. Due to shortcomings of the EC3 constitutive model and other approaches based on classical creep theory an alternative approach mainly based on the ideas of Krempl is proposed. Due to this so-called operator approach the material as well as the constitutive model is looked upon as an operator. The application of this view serves as a guide through the analysis of the relationship between experimental facts and constitutive theory especially in the context of transient creep.
Most of the previous studies on reinforced concrete columns with elastically restrained thermal elongation were carried out on square, rectangular or '+'-shaped cross sections. The number of fire resistance tests on circular reinforced concrete columns with elastically restrained thermal elongation is still very small. In order to examine the influence of several parameters on the behaviour in fire of this type of columns several fire resistance tests were carried out. The parameters tested were the load and restraint level, slenderness of the column and longitudinal reinforcement ratio. In the fire resistance tests the specimens were exposed to the ISO 834 standard fire curve and the critical time (fire resistance) and temperature and failure modes were determined. The test results showed that the spalling phenomenon may occur in circular columns and so reducing its fire resistance. The increasing of the load level led to a reduction while the increasing of the longitudinal reinforcement ratio or the decreasing of the slenderness of the columns led to an increasing of their fire resistance. The restraint level might not be much relevant on the fire resistance of circular reinforced concrete columns.
The fire stability of carbon fiber reinforced polymer (CFRP) shell structures was investigated using an intermediate-scale test setup. The shell specimens are representative of typical load-bearing CFRPs in modern civil aviation. The CFRP shell specimens were exposed to a fully developed fire with direct flame impingement to one side at a heat flux of 182 kW/m2. Specimens were simultaneously loaded with constant compressive force equal to 40% of the ultimate failure load. CFRP shells and four different fire retarding configurations, using integrated protective layers, were investigated. Unprotected CFRP specimens failed after just 27 s. Specimens with integrated protective layers with low heat conductivity and high burn-through resistance showed the most promising results. An integrated titanium foil decelerated the decomposition of the epoxy matrix and increased the time to failure by 68% compared to the unprotected CFRP shell.
Fire stability of glass-fibre sandwich panels: The influence of core materials and flame retardants
(2017)
Fire resistance has become a key property for structural lightweight sandwich components in aviation, shipping, railway vehicles, and construction. The development of future composite materials and components demands adequate test procedures for simultaneous application of compression and fully developed fire. Therefore an intermediate-scale approach (specimen size = 500 mm x 500 mm) is applied with compressive loads (up to 1 MN) and direct application of a burner to one side of the specimens, as established in aviation for severe burn-through tests. The influence of different core structures (polyvinylchloride foam, polyisocyanorate foam reinforced by stitched glass bridges, and balsa wood) was investigated for glass-fibre-reinforced sandwich specimens with and without flame retardants applied on the fabrics, in the matrix, and on surface for each specimen at the same time. Times to failure were increased up to a factor of 4. The intumescent coating prolongs the time to failure significantly.
What is more, using the intrinsic potential of the front skin together with the core to protect a load bearing back skin in sandwich panels, the design of the core – here using the wood core – is the most promising approach.
The fire behaviour of light-weight material used in structural applications is regarded as the main challenge to be solved for mass transportation. The task is to perform realistic experiments, including a mechanical test scenario under fully developed fires, to improve the material's reliability in structural applications. Our approach utilises an intermediate-scale test set-up (specimen size 500 × 500 mm) to apply realistic compressive loads and fully developed fires directly to one side of a carbon-fibre-reinforced sandwich composite. Three different intumescent coatings were applied to sandwich structures and compared to a bench-scale study. The results emphasise intumescent coatings as a promising method to sustain fire resistance, multiplying the time to failure. Nevertheless, the realistic intermediate-scale test using severe direct flame application underlines the extremely short failure times when the actual composite components are tested without any additional insulation.
The recommendation is based on the co-authors’ work organized by the RILEM TC 256-SPF “Spalling of concrete due to fire: testing and modelling”. It aims to provide useful information, guidance and best practices in fire spalling assessment to laboratories that perform large-scale tests based on fire resistance test standards. It provides guidance on the spalling observation techniques during testing, as well as post-test spalling quantification/assessment methods. This document is intended to be used in conjunction with the fire resistance test standards, e.g. EN 1363-1 and ISO 834-1.