Experimental and numerical investigation of plastic hinging of fasteners in CLT balloon-frame connections: insights from the WOODWISE large-scale compartment fire tests
| Authors: | Nicolas Coello, Erica C. Fischer, David Barber, Laura Hasburgh, Kara Yedinak |
| Year: | 2026 |
| Type: | Full Proceedings |
| Station: | Forest Products Laboratory |
| Source: | Proceedings from The 14th International Conference on Structures in Fire, Queen’s University/ York University, Canada. |
Abstract
Connections in mass timber buildings degrade during fire due to charring and temperature-dependent material reduction, leading to significant fastener deformation. This study develops a temperature-dependent Beam-on-Foundation (BoF) formulation for CLT balloon-frame connections exposed to the WOODWISE large-scale compartment fire. The ambient-temperature BoF model was first validated against embedment and single-shear tests from the literature, followed by development and validation of a heat transfer model using thermocouple data from WOODWISE Test #3. The validated temperatures were sequentially coupled to the mechanical model, incorporating temperature-dependent degradation and progressive removal of timber springs to represent charring. Results show that the predicted global force–displacement response follows the increase in char depth and spring removal. The framework also provides local force–deformation and stress–strain histories, enabling investigation of thermo-mechanical degradation mechanisms in CLT connections under fire.