Design and instability issues of log-house timber panels under in-plane compression loads

Abstract

Log houses are a traditional construction system that is still widely used today for residential homes, vacation cabins, off-grid living, and emergency shelters. While their structural behavior under lateral loads has been extensively studied, in-plane instability under compression due to gravitational loads remains underexplored. Only two modeling approaches have been proposed, both based on classical elasticity theory. However, these models rely on compensatory assumptions or calibrated correction coefficients to approximate actual buckling loads, often leading to significant discrepancies. Log panels share key characteristics with masonry walls: just as masonry has a low tensile strength perpendicular to mortar joints, log panels exhibit weak tensile resistance perpendicular to the grain and at friction-based log-to-log joints. This brittleness causes failure mechanisms similar to those in masonry, where elastic formulations for predicting buckling loads were abandoned since the 1930s in favor of simplified stability models. This study adapts the well-established design approach used for slender masonry walls to log panels by incorporating insights from masonry engineering. The proposed method is developed through an experimental campaign and numerical modeling. The design under in-plane compression, as in masonry, is governed by three key parameters: geometric slenderness, transverse wall stiffening, and load eccentricity. Experimental tests on walls with varying slenderness ratios and load eccentricities have been carried out. Additionally numerical simulations explored the influence of stiffening elements. This research proposes a design framework for log panels under in-plane compression.