The cross laminated timber (CLT) technology is nowadays a well-known construction system, which that can be applied to several typologies of residential and commercial buildings. However some critical issues exist which limit the full development of the CLT construction technology: problems in handling, difficulty in assembling...
This paper investigates the risk of disproportionate collapse following extreme loading events. The methodology mimics a sudden removal of a loadbearing wall of a twelve-storey CLT building. The ductility-demand from the dynamic simulation is checked against the ductility supplied by the structural components and their connections. The analyses focus on rotational stiffness (k) of the joints by considering three different sub-structural idealisations according to the required modelling details and the feasibility of model reductions. To resist the imposed dynamic forces, the required k-values may be too large to be practically achieved by means of off-the-shelf brackets and screw connections. Improved structural detailing as well as adequate thickness of structural elements need to be considered in order to reduce the probability of disproportionate collapse.
This paper related to elimination of the deficiencies. The behaviour of multi-storey buildings braced with cores and CLT shear walls is examined based on numerical analyses. Two procedure for calibrating numerical analysis models are proposed using information from Eurocode 5  and specific experimental test data. This includes calibration of parameters that characterise connections between CLT panels and other CLT panels, building cores and shear walls. The aim is to make the characterizations of behaviours of connections that reflect how those connections perform within complete multi-storey superstructures, rather than in isolation or as parts of substructures. The earthquake action for cases studied was according to Eurocode 8  and using the appropriate behaviour factor (q factor). Results of analyses of entire buildings are presented in terms of principal elastic periods, base shear and up-lift forces. Discussion addresses key issues associated with behaviour of such systems and modelling them. Obtained results permit creation of appropriate guidelines and rules for design of the aforementioned types of hybrid buildings incorporating CLT wall panels.
Project contact is Luca Sorelli at Université Laval
This project aims to develop a new precast wood / concrete floor system that can push the span limits in multi-storey wood buildings. The multidisciplinary methodology includes a finite element analysis technique using the “DDuctileTCS” software developed at CIRCERB, shear tests on connections, bending tests of the composite beam and an extension of technical standards for the design of composite structures. This project will develop solutions to optimize the composite action and vibration of long-span precast and mixed floors. The methodology consists of: (i) analysis of systems and optimization of shapes by numerical finite element techniques; (ii) connection shear tests; (iii) proof of concept on a prototype beam in the laboratory.
Cross Laminated Timber (CLT) structures are nowadays increasingly used worldwide and mostly in Europe where the system originated. However, in spite of this diffusion which led to the construction of a great number of multi-storey buildings all over Europe, still Eurocodes are almost completely missing provisions for CLT designers, especially regarding the seismic design. Nevertheless, Eurocode 8 requires in most cases, due to the regularity criteria being not fulfilled for most of the buildings, the use of the modal response spectrum analysis method, i.e. the linear dynamic analysis. This method requires the correct estimation of the lateral stiffness of the building in order to accurately calculate the design seismic forces in the building, which may be significantly underestimated or overestimated depending on the size of the building and the shape of the design spectrum. This can be done by modelling each connection with different methods that are often based on available test results, which are not easily accessible by a practicing engineer. This paper provides a design approach for dynamic linear modelling of CLT structures using SAP 2000. Equations are proposed based on available design codes and literature references, and used to design a 3-storey case study building. Further provisions for the seismic design of CLT buildings which are not included in Eurocode 8 are also given. Finally, the proposed design model is also compared with the results of the shaking table tests conducted in 2006 in Japan by CNR-IVALSA on a three-storey CLT building.
Previous studies have mainly focused on the behaviour of timber under uniformly distributed compression perpendicular to the grain (CPG) loads. However, there are many practical applications in which timber is loaded by non-uniformly distributed CPG loads. Different design and test codes like the Eurocode 5 (EC5), DIN 1052:2004, ASTM D143- 94 and EN-408:2010 only account for load configurations where timber is subjected to uniformly distributed loads. For specific uniformly distributed load (UDL) configurations the bearing capacity of timber (solid softwood timber or Glulam) in compression is adapted by using a load configuration factor (kc,90) according to EC5, the European code for design of timber structures. EC5 has no guidelines for cross-laminated timber (CLT) under UDL with the exception of the Austrian National Regulations for EC5.
In this work, an experimental and numerical study on the bearing capacity and displacement behaviour of CLT subjected to non-uniformly distributed loading (NuDL) is conducted on eight different load configurations. A steel-CLT connection in which the CLT is partially loaded is used in this study. Finite element modelling, performed using the commercial software Abaqus CAE is used as the numerical simulation of the experimental study and is validated by experimental results. Load configuration factors (kc,90) from experimental results are compared with values from the Swedish CLT handbook (KL-Trähandbok). The outcome of the study shows that load configuration factor for NuDL cases is higher than for UDL cases. Hence, for same load configurations a lower CPG strength is required in NuDL than in UDL. Moreover, numerical results feature overall good congruence with the elastic phase of the experiments and have the potential to augment experiments in further understanding other complex steel-CLT connections
This paper presents the modeling of coupling effect of tension and shear loading on Cross Laminated Timber (CLT) connections using a finite element based algorithm called HYST. The model idealizes the connections as a “Pseudo Nail” - elastoplastic beam elements (the nail) surrounded by compression-only spring elements (steel sheath and wood embedment). A gap size factor and an unloading stiffness degradation index of the spring elements under cyclic loading were integrated into the optimized HYST algorithm to consider the coupling effect. The model was calibrated to compare with 32 configurations of CLT angle bracket and hold-down connections tests: in tension with co-existent constant shear force, and in shear with co-existent tension force. The results showed that the proposed model can fully capture the coupling effect of typical CLT connections, considering strength degradation, unloading and reloading stiffness degradation, and pinching effect. The model provided a useful tool for nailbased timber connections and a mechanism-based explanation to understand the hysteretic behaviour of CLT connections under bi-axial loading.