Seismic behaviour evaluation of CLT horizontal diaphragms on hybrid buildings with reinforced concrete shear walls

In the last years in a worldwide level, the number of CLT buildings in height has been increased. In seismic countries, the design of these buildings is limited because there are still discussions about parameters of wood seismic design such as the modification factor of structural response and the allowed story drift. In this context, a hybrid building shaped by a gravity slab system (CLT) and wood columns combined with a seismic-resistant system of reinforced concrete cores, allow the use of wood in high buildings with fewer restrictions than CLT buildings. Each floor of the hybrid building explained before is composed by a horizontal diaphragm, shaped by CLT panels and connections that provide flexibility to the system. Due to the horizontal diaphragm role in the transfer of seismic loads to the vertical elements, the traditional design expects the diaphragm to behave inside the elastic range. Therefore, the study of the behaviour in a hybrid configuration is taking relevance. A group of four hybrid buildings with different configurations was submitted to three types of analysis (nonlinear static, spectral modal, time-history), which demonstrate an oscillating seismic behaviour among semirigid and flexible. Also, the connections of the models submitted to the time-history analysis were not in the inelastic range, which was justified by the correct choice of the design model. Finally, it was concluded that the correct diaphragm classification is very important because it was demonstrated that increasing the flexibility of the diaphragm increased their demand and decreased the demand on the walls.

Automated summary

The increase in the number of tall CLT buildings worldwide in recent years has raised discussions about wood seismic design parameters; a hybrid building using both CLT and concrete cores was found to have fewer restrictions in high-rise wood utilization. Analysis of four hybrid buildings with different configurations demonstrated oscillating seismic behavior between semi-rigid and flexible, emphasizing the importance of correct diaphragm classification in reducing wall demand.