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44 MATERIALS MAR/APR 2026 FDM ASIA | www.fdmasia.com

johannes@buldmann.de thermal decomposition process that results in the formation
of a char layer.
This charring significantly affects the fire resistance of wood
components. The char layer develops between the exposed
surface and the pyrolysis front, which is commonly associated
with the 300 deg C isotherm.

Due to its low thermal conductivity, the char acts as an
insulating shield, protecting the underlying uncharred wood
from further heat exposure and thereby reducing the rate at
which heat penetrates the material.
While extensive research has been conducted on the fire
width, and can be produced in lengths up to 50 m. resistance of solid timber and Glulam, CLT presents distinct
This manufacturing flexibility allows Glulam to be produced challenges arising from its layered configuration and adhesive
in large sizes or curved geometries to meet both structural interfaces.
and architectural design requirements. Existing design standards often generalise charring rates and

Glulam exhibits a very high strength-to-weight ratio, which residual strength parameters based on homogeneous materials,
makes it stronger than structural steel when compared by without adequately accounting for the effects of delamination,
weight, and it is therefore ideal for long span and load-bearing adhesive degradation, and interlaminar heat transfer.
applications. These oversights contribute to discrepancies between
Contemporary mass timber construction often employs experimental observations and code-based predictions. The
hybrid systems that combine Glulam and CLT to enhance motivation for this study stems from the need to address
overall structural efficiency. In these configurations, Glulam these limitations through a detailed comparative investigation

beams and columns form the primary load-bearing skeleton, of Glulam and CLT fire performance, with the aim of improving
while CLT panels function as horizontal diaphragms for floor the predictive reliability of major international design standards.
and roof assemblies. From a practical design standpoint, a direct comparison
This integrated approach leverages the high bending and between Glulam and CLT is necessary because their fire
axial strength of Glulam members complemented by CLT's response is governed by fundamentally different mechanisms.
inherent dimensional stability and ease of installation, resulting Glulam behaves largely as a laminated but directionally
in a robust and streamlined building system. homogeneous section, for which residual section approaches
are commonly applied.
Problem Statement In contrast, CLT has a layered layup and adhesive bond

A major challenge associated with timber construction, when lines that introduce interface phenomena, including heat-induced
compared to conventional materials such as concrete and steel, delamination and char fall-off that can expose fresh wood
is its inherent vulnerability to fire, a concern that becomes and alter the progression of damage in ways not captured by
more critical in tall buildings due to extended evacuation times. assumptions derived from homogeneous or simply laminated
Understanding the fire performance of mass timber structures members.
is essential for ensuring safety and resilience. When timber is This distinction has immediate implications for performance-
subjected to elevated temperatures, it undergoes pyrolysis, a based fire design. When designers rely on charring-based