Summary of the fire protection foundation report - fire safety challenges of tall wood buildings

Abstract

Buildings constructed from engineered timber are becoming more prevalent globally as building designers, owners and architects realize the sustainability opportunities with timber construction and the overall aesthetic of a completed timber building. As timber buildings are planned to be taller than many model codes permit, the National Fire Protection Association (NFPA) Fire Protection Foundation commissioned research entitled "Fire Safety Challenges of Tall Wood Buildings", with the aim of understanding where the current gaps in knowledge are and how the research agenda should be prioritized. With new engineered timber products such as cross-laminated timber becoming more prevalent, this study evaluated the current knowledge of tall timber construction to identify gaps in knowledge, and where if fulfilled, will provide a better understanding of the potential fire safety performance of tall timber buildings. The study identified a number of knowledge gaps, of which most were related directly to the new technology of engineered timber products that have resulted from the use of CLT. These included system-level fire testing, use of composite assemblies, CLT char fall-off and construction fire safety. The study concluded that the priority for future research should target three areas of research, being the contribution of exposed timber to room fires; connections between timber components and timber composite assemblies; and penetrations for building services.

Flame extinction and burning behaviour of timber under varied oxygen concentrations

“…not protected with nonflammable materials) presents a new challenge that must be addressed before structural timber can be used with the same confidence as other building materials and systems. In the event of a fire, exposed timber inside of a compartment will contribute to the fire growth, intensity, duration, and eventual decay of the fire [1]. In order to ensure structural integrity, achieving the cease of flaming combustion after burnout of the original fuel load within the compartment is critical.…”

Energy‐based time equivalent approach for evaluating the fire resistance of timber components exposed to realistic design fire curves

“…[45][46][47][48][49] When the unprotected surface is relatively small and eventually self-extinguishing, the influence of the extra heat released by the unprotected surface on the design fire models can be ignored. [50,51] Due to the large cross-section and higher density of the load-bearing timber components, the timber burns only on the surface in a fire and forms a thick charring layer. The charring layer not only dramatically reduces the heat transfer rate to the virgin timber, resulting in a rapid decline in the pyrolysis rate, [52] but also the timber will eventually self-extinguish once the incident heat flux is below a certain level (heat flux is below 45 kW/m 2 [[48]] ).…”

“…Hence, the exposed load-bearing timber components hardly contribute to the overall compartment fire due to the smaller exposure area, slower heat release rate, and self-extinguishing characteristics. [46][47][48][49][50][51][52][53] This provides an opportunity for the time equivalent approach based on design fire models to be applied to the fire-resistant design of exposed load-bearing timber components. While the time equivalent approaches are valid for the fire resistance of timber building with limited exposure, including load-bearing components, they offer the most benefit for timber-concrete composite floor structures.…”

Estimation of Credibility of the Results of Measuring Temperature within Specimens of Wood Columns Obtained During Fire Tests

“…In particular, some methods for the determination of fire resistance rating of wood bars and slabs were developed based on conduction of ap-propriate experimental studies. Studying wood has been conducted by the following foreign scientists: White, Frangi et al [11]. But up to now specific features of wood columns having been subjected to fire retardant treatment were not considered to the full, and no method of full value exists for the determination of fire resistance rating of wood columns with fire retardant coating based on OSB slabs, in particular, the one to use tabulated values.…”