Experimental and numerical analysis of in-plane compressed unprotected log-haus timber walls in fire conditions

The paper presents an experimental and Finite Element (FE) numerical analysis of the behavior of unprotected log-haus timber walls in fire conditions under in-plane compressive loads. The aim is to assess their overall structural performance and to provide possible design suggestions. In doing so, the main results derived from a full-scale experimental test of a log-haus specimen subjected to the standard fire curve and loaded in-plane in compression are first described. FE numerical simulations are then carried out, to further assess the test results and to perform - based on the rather close correlation between test and FE results - a parametric study on the examined structural system. The effects of several influencing parameters are then investigated, including the presence of an initial geometrical out-of-plane global curvature, the possible exposure to fire of orthogonal logs and carpentry joints acting as lateral outriggers for the main log-haus wall, and the compressive loading ratio acting in combination with the fire loading. The most significant effects of such influencing parameters are highlighted in terms of overall buckling resistance and failure mechanisms for the examined walls in fire conditions, providing evidence for the reduction of their actual load carrying capacity. In conclusion, aiming to derive useful design suggestions, a possible extension to log-haus systems of the “Reduced Cross-Section Method” (RCSM) currently in use for the verification of fire exposed timber members is proposed.