ASPID: An asymmetric pinching damaged hysteresis model for timber structures

• Published in: Construction & building materials Vol. 404; p. 133106
• Main Authors: Chacón, M.F., Guindos, P.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 10.11.2023
• Subjects: Asymmetrical behavior; Cross-laminated timber; Light-frame timber walls; Low-cycle fatigue; Phenomenological hysteretic model; Pinching effect; Strength and stiffness degradation; Timber joint model; Pinching effect; Low-cycle fatigue; Phenomenological hysteretic model; Timber joint model; Cross-laminated timber; Light-frame timber walls; Strength and stiffness degradation; Asymmetrical behavior
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2023.133106

This paper presents a new high-fidelity phenomenological-based hysteretic model called ASPID that includes asymmetry, pinching, and strength/stiffness degradation for timber members. To capture asymmetry, one force–displacement envelope and ten physical-based hysteretic parameters are used for each loading direction. Pinching is added with an unloading–reloading monotone smooth piecewise function composed of two quadratic Bézier polynomials and one linear segment. Strength degradation at target displacement is taken using a novel fatigue law based on the maximum displacement and hysteretic dissipated energy. Exponential stiffness degradation of pinching and reloading phases is adopted in terms of their maximum displacement, whereas irreversible damage is captured using two threshold displacements independent of each loading direction. The update force algorithm is included for their computational implementation, and a Python version can be downloaded for free. The model is validated using six experimental benchmark tests of mass and lightweight timber connections and assemblies with symmetric/asymmetric behavior, where an optimized parameter identification process is considered. Moreover, the model test responses are compared with three well-known hysteretic models: SAWS, Pinching4, and DowelType. The ASPID model’s test results show an error less than 7.6% for the capacity and 2.9% for the cumulative dissipated energy as well as fits with high precision the force and dissipated energy history, getting a Normalized Root Mean Square (NRMS) error less than 4.3% and 2.8%, a Normalized Mean Absolute (NMA) error less than 2.7% and 1.5%, and a coefficient of determination R2 over 94.88% and 99.09%, respectively. Finally, comparing the four hysteretic models, the ASPID model gives the highest R2 values in all tests and has the smallest NRMS and NMA errors regarding force history and the smallest NMA errors for the dissipated energy history. •A new high-fidelity hysteretic model is proposed to simulate timber structures.•Fine simulations of asymmetry, pinching, and stiffness/strength degradation are achieved.•Energy-displacement-based evolution law drives the strength/stiffness degradation and fatigue.•The model is validated with a wide variety of timber connections/assemblies benchmarks.•Updated force algorithm in Python codes can be freely downloaded under the MIT license.