Fire Safety Journal最新文献

It is an essential requirement for all building products to ensure durability of their fire safety. Throughout the working life of products, intumescent coatings are aged by certain climatic factors. To predict a lifetime of several years, generally the behaviour of the intumescent coating is extrapolated based on accelerated artificial ageing. The established German and European procedures to assess the durability assume a working life of at least 10 years. For a longer period, additional evidence is required; yet the procedure and the specifications to justify this are not described. In addition to addressing this formal lack, from a scientific point of view it is necessary to investigate the degradation of intumescent coatings in detail and to propose a reliable test concept to assess durability for more than 10 years. This paper summarises the existing knowledge about the ageing of intumescent coatings. The results of various demanding weathering approaches are presented for two intumescent coatings tested in a joint research project. Moreover, formulations with a reduced amount of functionally relevant components were analysed to gain insight into the associated effects. Derived from these research results and knowledge, recommendations are proposed to assess the durability of intumescent coatings for more than 10 years based on a combination of verifications.

The performance of a water mist system to suppress shielded fires is analyzed experimentally in this work. The diesel pool fire is used as the fire source in an enclosure with 2.4 m × 2.4 m × 3.1 m measurements, and a mechanism is designed to provide different shielding conditions by changing the obstacle size and height. The characteristics of a low-pressure multi-orifice nozzle including the drop diameter and the velocity are studied by a Phase Doppler Particle Analyzer (PDPA) system. In total, 10 cases with diverse shielding conditions are defined and different parameters including the temperature distribution, the gas concentrations, and the extinguishing time are measured. Based on the present data, mist droplets in some shielded fire scenarios were able to bypass the obstacle, overcome the fire plume thrust, and suppress the fire. In fire scenarios with the same obstruction size, the reduction of the distance between the obstacle and the nozzle led to an increased block ratio and consequently, the extinguishing time was decreased. It was found that the temperatures in the central axis above the fire and the lateral temperatures declined quickly in cases with short suppression time.

This paper presents numerical analyses of the thermo-mechanical behavior of restrained square concrete-filled steel tubular (CFST) columns subjected to standard fire. It is found that the behavior is significantly influenced by the load ratio and axial restraint level. The collapse of restrained columns in fire conditions can be defined as the axial force in columns reaching 0 or the axial contraction deformation reaching a hundredth of column length. Three collapse modes are discovered, i.e., the expansion deformation collapse mode, contraction deformation collapse mode, and load-bearing capacity loss collapse mode. Under a low load ratio, three distinct modes of collapse are possible. Conversely, at a high load ratio, only the contraction deformation collapse mode and the load-bearing capacity loss collapse mode are observed. Through analytical and numerical approaches, a method for identifying the collapse mode based on geometric dimensions, axial restraint level, and load ratio has been established. This identification method can significantly contribute to optimizing fire protection strategies for CFST columns in structural designs.

With the climate crisis and pursuit of efforts to reduce embodied carbon impacts in the built environment, steel-timber hybrid structures have emerged as a sustainable form of framed construction which offer numerous benefits over the widely used and well-established steel-concrete hybrid structures. However, there are major concerns about the structural fire performance of such systems among various stakeholders in the construction industry, particularly for the design implications in terms of the lateral-torsional buckling behaviour and the degree of lateral restraint mobilised in the steel-to-timber connections. The screws that connect cross-laminated timber slabs to steel beams may provide a certain degree of restraining action in fire. However, further investigations are required to quantify the slip characteristics of such connections. In this study, it was found from existing literature that at the fire limit state, the continuous elastic lateral stiffness available to restrain the beam varies between approximately 500 kN/m/m and 2000 kN/m/m. Relying entirely on the screws and using this practical range of stiffness, a parametric study using Eurocode 3 design buckling resistance equations on 9 m simply supported span steel beams and beam-columns with span-to-depth ratios of about 10, 15, 20 and 25 was performed. The results indicate that designing such members as fully restrained in fire conditions may lead to unrealistic assumptions and unsafe structures.

Vehicles that are powered by gaseous fuel, e.g., compressed natural gas (CNG) or hydrogen (H₂), may, in the event of fire, result in a jet flame from a thermally activated pressure relief device (TPRD), or a pressure vessel explosion. There have been a few incidents for CNG vehicles where the TPRD was unsuccessful to prevent a pressure vessel explosion in the event of fire, both nationally in Sweden and internationally. If the pressure vessel explosion would occur inside an enclosure such as a road tunnel, the resulting consequences are even more problematic. In 2019 the authors investigated the fire safety of CNG cylinders exposed to localized fires. One purpose of the tests conducted in 2021 reported in this paper is to investigate whether extinguishment with water, e.g., from a tunnel deluge system, may compromise the safety of vehicle gas cylinders in the event of fire. Steel cylinders handles the situation with localizde fire and/or cooling with water well. Composite tanks can rupture if the fire exposure degrades the composite material strength, and the TPRD is not sufficiently heated to activate, e.g., if the fire is localized or if the TPRD is being cooled by water, which prevents its activation.

In the built environment, often too much focus is put on compliance instead of seeking the optimal fire-safety solution for the building. Because of a lack of tangible incentives for building owners, the benefits of implementing fire safety measures and their societal contribution are often not recognized and therefore, not considered. By means of a literature review and a survey, we have indicated necessary fire-safety related attributes and tool features and analyzed the currently available fire risk assessment tools. This study shows that a limited number of these tools can provide a partial fire risk analysis of a building. A total of 26 tools were found. No tools were found that included all the identified fire consequence-related attributes to ensure fire-safe buildings. However, we did identify 11 tools that have the potential to assess between 32 % and 52 % of the found attributes of building fire safety. To stimulate the development of such tools, this paper provides 12 factors by which to assess fire risk assessment tools – quantifying the overall ‘quality’ of the assessment tool – which can incentivize industry to refine the existing ones with enhanced predictability of the potential consequences of fire incidents.

Recent design guides include charring models for cross-laminated plane timber (CLT) members. When the bond line integrity is not maintained, charring is illustrated as a combination of sequenced phases. Significant research has been conducted on the charring behaviour of CLT panels, and the criterion of 300 °C has been an accepted definition for the char front line. The charring rate of a solid wood-based panel is determined by the char depth divided by the time to reach the char depth. In the CLT structure, this method can be applied to the first lamella layer. However, due to the char fall-off, it cannot be directly applied to the lamella layers behind the first layer. In this research, eight fire tests were conducted to investigate how charring rates of different lamella layers can be determined from measured temperatures. An assessment method based on the mean char depth development determined from experimental temperature distributions of CLT panels is introduced. Also, the effects of thermocouple positioning and specimen orientation on the assessment results were analysed. The charring rates determined for both horizontal and vertical specimens align well with the results calculated using the European Charring Model and a post-protection factor k₃ of 2.

The aim of this study was to investigate experimentally the influence of fuel moisture content on the fire behaviour of Cistus monspeliensis, when exposed to a fire front spreading across a fuel bed. Shrubs of Cistus monspeliensis with leaf moisture contents ranging between 10 and 100 % were placed under a Large Scale Heat Release Calorimeter and a bed of wood wool was used before and under the branches to mimic an ignition from an underneath burning herbaceous layer. Mass loss, heat release rate (HRR) and total heat release (THR) were measured. The peak of HRR, the THR and the effective heat of combustion decreased linearly with the leaf moisture content. Two thresholds, characteristics of the fire behaviour of Cistus monspeliensis, were obtained. The ignition threshold, equals to 85 %, is the maximum leaf moisture content at which the cistus will ignite. The spreading threshold, equals to 55 %, is the maximum leaf moisture content at which the flame front will spread through the branches.