Abstract
The use of cross-laminated timber (CLT) in multi-story buildings is increasing due to the potential of wood to reduce green house gas emissions and the high load-bearing capacity of CLT. Compression perpendicular to the grain (CPG) in CLT is an important design aspect, especially in multi-storied platform-type CLT buildings, where CPG stress develops in CLT floors due to loads from the roof or from upper floors. Here, CPG of CLT wall-to-floor connections are studied by means of finite element modeling with elasto-plastic material behavior based on a previously validated Quadratic multi-surface (QMS) failure criterion. Model predictions were first compared with experiments on CLT connections, before the model was used in a parameter study, to investigate the influence of wall and floor thicknesses, the annual ring pattern of the boards and the number of layers in the CLT elements. The finite element model agreed well with experimental findings. Connection stiffness was overestimated, while the strength was only slightly underestimated. The parameter study revealed that the wall thickness effect on the stiffness and strength of the connection was strongest for the practically most relevant wall thicknesses between 80 and about 160 mm. It also showed that an increasing floor thickness leads to higher stiffness and strength, due to the load dispersion effect. The increase was found to be stronger for smaller wall thicknesses. The influence of the annual ring orientation, or the pith location, was assessed as well and showed that boards cut closer to the pith yielded lower stiffness and strength. The findings of the parameter study were fitted with regression equations. Finally, a dimensionless ratio of the wall-to-floor thickness was used for deriving regression equations for stiffness and strength, as well as for load and stiffness increase factors, which could be used for the engineering design of CLT connections.
Highlights
The orthogonal orientations of timber lamellae in cross-laminated timber (CLT) enhance the load-bearing potential of timber as a structural wood-based product and provide a possibility of using timber as a two-dimensional load-bearing element
The numerical investigations of Compression perpendicular to the grain (CPG) in CLT wall-to-floor connections in this study are based on a recent experimental analysis by Schweigler et al [39], which is summarized in the following
Validation of the finite element model rests on the comparison of model predictions with experimental data that include the effect of several influence parameters on CPG
Summary
The orthogonal orientations of timber lamellae in cross-laminated timber (CLT) enhance the load-bearing potential of timber as a structural wood-based product and provide a possibility of using timber as a two-dimensional load-bearing element. Due to the renewable and sustainable characteristics of timber and numerous advantages of building with CLT over solid wood and glued laminated timber (GLT), CLT became an alternative to non-renewable construction materials in multi-story buildings. As a comparatively new engineered wood-based product, its load-bearing behavior, as a function of its layup and intrinsic material characteristics of wood, is not yet fully exploited for a more efficient production as well as for engineering design rules. In a multi-storied CLT building with traditional platform-type construction, CPG stress develops in CLT floors due to loads from the roof and from upper floors
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