Non-linear springs for cyclic analysis of wooden structures

A non-linear spring for modelling of wooden structures under seismic loading condition has been implemented as an external library in OpenSees framework. This element, previously used in the FE code ABAQUS and written in Fortran 77 language, has been interfaced with OpenSees via an ad-hoc routine. The proposed element is used in static and dynamic non-linear models of wooden structures to represent the dissipative capacity of steel connections. An example of a X-lam (cross-lam) wall is presented and a comparison with available experimental results is shown. The model is built with non-linear springs elements and quad elements characterized by linear-elastic behaviour.

This article presents an implementation of a new element in the OpenSees Framework. From version 2.3.0 (release tag 4554), OpenSees supports external libraries (DLL) to adding capabilities to the framework. The available Fortran wrapper has been used to interfacing OpenSees classes to Fortran structured code. The new implemented non-linear spring element models the hysteretic behaviour of a steel connector for X-lam wooden buildings, like the spring element presented in [1]. X-lam panels are schematized with Quad elements associated to elastic material, while the steel connections are modelled using the aforementioned non-linear springs. The model is based on the evidence that energy dissipation of X-lam wooden buildings subjected to earthquake excitation mainly occurs in the connections between panels and with the foundations. With this assumption, the capabilities of the proposed model can be used to carrying out static and dynamic non-linear analyses of X-lam structures with the aim to predict faithfully their seismic performance. In this paper, a first non-linear static analysis of a X-lam wall is presented, and the results are compared to experimental ones.

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This article is part of "Opensees Days Italy" - Modeling, Design and Analysis of Structures in Seismic Areas. Proceedings of the 1st Italian conference - Rome, 24-25 May 2012

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Il presente articolo è tratto dagli atti di "OpenSees Days Italia" - La modellazione, il calcolo e l’analisi delle strutture in zona sismica.
Atti del 1° convegno italiano – Roma, 24-25 maggio 2012

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Il volume può essere richiesto scrivendo a Massimo Grasso -