Experimental Investigation of Load Redistribution in a Historic-Type Timber Roof Segment Under Progressive Tie-Beam Weakening
This study examines how progressive loss of tie-beam stiffness redistributes deformation demand and internal force within an experimentally verified historic timber roof segment. A three-frame laboratory model was evaluated by close-range photogrammetry, inductive displacement sensing, post-test bending tests, and finite-element modelling. The measurements revealed clear frame-to-frame stiffness asymmetry, a distinct pre-cut settlement phase under sustained load, and accelerated deformation once the residual tie-beam section was substantially reduced. A refined model using member-specific elastic parameters reproduced the global loading response more accurately than a uniform-stiffness model. The damaged zone could also be represented by an equivalent rotational spring, although the fitted spring values remained response-dependent. The results indicate that lathing acted as a temporary redundancy path after severe weakening and that a nearly hinged residual section was not mechanically equivalent to a fully severed member within the tested configuration.