Characterisation of the rigid diaphragm conditions for cross laminated timber floors

This paper presents a comprehensive numerical study aimed at defining the conditions for which Cross-Laminated Timber (CLT) floor diaphragms of platform-type CLT buildings can be assumed rigid in linear seismic analyses. Numerical analyses are conducted on a regular CLT archetype within a framework of parametric analyses, in which different geometrical and mechanical parameters including the stiffness of the floor panel-to-panel connections, the stiffness of the floor-to-wall connections, the floor span, the distance between two consecutive shear-walls, the lateral stiffness of the shear-walls, and the number of storeys are varied. The conditions to ensure a rigid diaphragm behaviour are derived by calculating the discrepancies in terms of floor displacements, distribution of lateral forces in the shear-walls, and fundamental vibration period of the structure, between numerical models where the floor is modelled with its actual deformability and as rigid. The discrepancies are compared with threshold values given in Eurocode 8 and used to derive the conditions for which CLT floor diaphragms can be assumed rigid. The study reveals that the behaviour of the floor tends toward the rigid diaphragm condition by increasing the stiffness of the floor panel-to-panel connections and the number of storeys, and by decreasing the stiffness of the floor-to-wall connections, the ratio between the distance between two consecutive shear-walls and the floor span, and the stiffness of the shear-walls. Specific threshold values ensuring a rigid diaphragm behaviour are determined for the properties of the system, delivering the geometrical and mechanical conditions for rigid CLT floor diaphragms

An innovative shear-tension angle bracket for Cross-Laminated Timber structures: Experimental tests and numerical modelling

An experimental testing programme on an innovative metal angle bracket for Cross-Laminated Timber structures is presented in this paper. The main novelty of the angle bracket is the use of fully-threaded screws to improve mechanical properties in tension direction. Monotonic tests to evaluate mechanical properties of the wall-to-floor connection in tension and shear directions are presented and discussed. A detailed three-dimensional finite element model, implemented in ABAQUS, which considers the typical non-linear behaviour of fasteners in timber element, is presented and used to reproduce the experimental results. The group effect and strength domain of the fasteners are also analysed. The finite element model can predict experimental results when the group effect and strength domain of the fasteners are taken into account. Finally, the finite element model was used to numerically analyse the effect of inclined loads and evaluate the strength domain of the innovative angle bracket. © 201

Tensile and shear behaviour of an innovative angle bracket for CLT structures

In this paper, experimental tests and numerical analyses conducted on an innovative angle bracket for Cross-Laminated Timber (CLT) structures subjected to tension and shear loads are presented. Such angle bracket represents an improvement of the available angle brackets manufactured by Rotho Blaas and was designed to increase the tensile capacity by adding inclined fully-threaded screws. Results of experimental tests carried out at Laboratory of Earthquake and Dynamic Engineering (LEDA) of the Enna Kore University are presented in terms of force-displacement curves. All the experimental tests are then simulated fusing a numerical model implemented in the FE solver ABAQUS. The influence of the mechanical behaviour of screws and nails on the angle bracket performance was then investigated, considering stiffnesses and strengths from both experimental programmes and codes of practice, and evaluating the importance of the Group Effect. The obtained force-displacement curve is compared with the experimental curves, showing a good accuracy of the proposed FE model. Experimental tests confirmed that fully-threaded screws increased the tensile capacity of the angle bracket. © WCTE 2018 Committee

CLT Shear Walls Anchored with Shear-Tension Angle Brackets: Experimental Tests and Finite-Element Modeling

Due to the high in-plane stiffness and strength capacity of cross-laminated timber (CLT) panels, the mechanical behavior of CLT shear walls is mainly influenced by the mechanical performances of the connections. Several calculation models have been proposed considering the mechanical anchors effectiveness only along their primary direction. However, recent studies showed a relatively high stiffness and capacity of new typologies of angle brackets when subjected to uplift vertical loads, such as for the wall-to-floor Titan V (TTV) angle bracket, developed to obtain high mechanical performances along both the vertical-tensile and horizontal-shear direction. In this paper a study on CLT shear walls anchored with TTV angle bracket is presented. The aim of the work is to investigate the effects of the coupled shear-tension behavior of the connections at the wall level and the effectiveness of TTV as an alternative to traditional mechanical anchors. The paper presents results from full-scale experimental tests and finite-element (FE) numerical analyses in SAP2000, where an innovative macroelement has been developed to model the TTV coupled shear-tension behavior. The effects of the plastic load redistributions of the TTV angle bracket on the global mechanical behavior of the CLT shear wall are discussed