Non linear modelling of the three and seven storey X-lam buildings tested within the SOFIE Project, LS Wann, AE Weyman, H Feigenbaum

Tags: Guillaume Herve Poh, numerical models, Giovanni Rinaldin, Italy, shaking table, SOFIE Project, numerical model, University of Trieste, experimental data, University of Sassari, Giovanni Rinaldin1, Massimo Fragiacomo, seismic behaviour, experimental results, NON-LINEAR ANALYSES, shell elements, parametric studies, component approach, Piecewise-linear, non-linear, types of buildings, shaking table tests, Fragiacomo M., multi-storey buildings, Ceccotti A. Strength, dynamic analyses
Giovanni Rinaldin1, Guillaume Herve Poh'sie2, Massimo Fragiacomo3, Claudio Amadio4
ABSTRACT: The seismic behaviour of cross-lam (cross-laminated, X-lam in the following) buildings has been analysed using the Experimental results provided by SOFIE Project [1] on three and seven storey structures tested on shaking table. Two numerical models have been developed using the component approach presented in [2], where all the wooden parts are considered as elastic and the connectors are modelled with elastic-plastic springs with a predefined hysteretic rule. The developed springs can take into account stiffness and strength degradation, pinching, the friction effect and axial-shear strength interaction. Non-linear dynamic analyses have been carried out on the models, and the results compared with the experimental data, showing an overall good agreement. KEYWORDS: cross-lam, X-lam, seismic behaviour, non-linear model, hysteretic spring, FE modelling
1 INTRODUCTION 123 A growing interest on seismic behaviour of cross-lam (Xlam) buildings arose in the last decade. The SOFIE project [1], carried on by the CNR-IVALSA Trees and Timber Institute in Italy, achieved some important results on the seismic behaviour of multi-storey X-lam buildings. In particular, several shaking table tests were carried out in Japan on three and seven storey buildings (Fig. 1). Based on these experimental results, a proposal for the behaviour factor of these buildings was made [3]. The experimental data available in literature have been used in this work to validate a non-linear numerical model representing the multi-storey structures tested on shaking table. The aim is to develop a representative numerical model that can be used in parametric studies to investigate the seismic vulnerability of X-lam buildings. 1 Giovanni Rinaldin, Post-doc Research Fellow, University of Sassari, Palazzo del Pou Salit, Piazza Duomo 6, Alghero, SS, Italy. Email: [email protected] 2 Guillaume Herve Poh'sie, PhD candidate, University of Trieste, Piazzale Europa 1, Trieste, TS, Italy. Email: [email protected] 3 Massimo Fragiacomo, Associate Professor, University of Sassari, Palazzo del Pou Salit, Piazza Duomo 6, Alghero, SS, Italy. Email: [email protected] 4 Claudio Amadio, Full Professor, University of Trieste, Piazzale Europa 1, Trieste, TS, Italy. Email: [email protected]
Figure 1: Photos of the 3-storey (left) and 7-storey (right) X-lam buildings tested on shaking table (copyright CNR-IVALSA) 2 NUMERICAL MODELLING The main assumption is that, in X-lam buildings, the dissipative capacity is only due to the steel connectors, such as angle brackets, hold-downs and screws. Each connector has been schematized by a non-linear spring with a proper hysteretic behaviour; such springs have been calibrated upon experimental tests carried out on single connections of the same type and with the same number of
nails. Finally, the models were implemented in the general FEM solver ABAQUS. 2.1 X-LAM PANELS The X-lam panels have been modelled as 4-node linear elastic shell elements (type S4R in ABAQUS) with reduced integration. The material used is isotropic, and the Young's modulus has been evaluated averaging the one of each layer that composes the panel with their thickness. 2.2 NON-LINEAR SPRINGS The springs developed schematise the shear and the axial behaviour of one connector (angle bracket, hold-down or screw) with two different piecewise laws, presented in Figures 2 and 3, for shear and axial component, respectively.
3 NON-LINEAR ANALYSES OF THE BUILDINGS The model is an assemblage of shell elements and nonlinear springs (Figure 4). Several dynamic analyses with the accelerograms used during the shaking table tests were carried out. An overall good accuracy of the model was found, which can then be effectively used to perform parametric studies on these types of buildings.
Figure 2: Piecewise-linear law of shear spring component Figure 3: Piecewise-linear law of axial spring component The springs can account for strength and stiffness degradation and for the friction effect. Moreover, a strength domain between the axial and the shear components has been implemented. Finally, the springs have been calibrated using data provided in [4]. A complete description on the non-linear springs is given in [2].
Figure 4: Three-dimensional view of the developed model for 7-storey building 4 CONCLUSIONS The presented model allows the user to predict the seismic response of multi-storey X-lam buildings with good accuracy. The dynamic analyses carried out confirm the validity of the component approach for the non-linear characterisation of this type of structures, with an overall good agreement on the time-history responses recorded during shaking table tests. REFERENCES [1] IVALSA-CNR Trees and Timber Institute. Sofie Project ­ new architecture with wood,, 2008. [2] Rinaldin G., Amadio C., Fragiacomo M. (2013) A Component approach for the hysteretic behaviour of connections in cross-laminated wooden structures, Earthquake Engineering and Structural Dynamics, in print, DOI: 10.1002/eqe.2310. [3] Ceccotti A., Follesa M., Lauriola MP., Sandhaas C., Minowa C., Kawai N., Yasumura M. Which seismic behaviour factor for multi-storey buildings made of cross-laminated wooden panels. Meeting 39 of the Working Commission W18-Timber Structures, CIB; 2006, Florence (Italy), August 28-31. [4] Gavric I, Fragiacomo M, Ceccotti A. Strength and deformation characteristics of typical X-lam connections. Proceedings of WCTE 2012, World Conference on Timber Engineering, Auckland, New Zealand, 16-19 July 2012, DVD.

LS Wann, AE Weyman, H Feigenbaum

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