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.
This paper presents the first results of the flanksound project, a study promoted by Rotho Blaas srl regarding flanking transmission between CLT panels jointed with different connection systems. The vibration reduction index Kij is evaluated according to the EN ISO 10848 standard by measuring the velocity level difference between CLT panels. The performance of the X-RAD connection system is compared to the performance of a traditional connection system made of shear angle bracket and hold-down, both the configurations being tested with and without a resilient material placed between the construction elements. Concerning the traditional system, the influence of the difference sizes and types of fasteners - including the method of nailing or screwing - was also evaluated. The results of the measurements exposed in this work will hopefully contribute to the development of the acoustic design of timber buildings by providing a solid database of Kij values, which can be used to forecast the acoustic performance of the building according to the prediction models proposed in EN 12354-1.
International Conference on Structural Health Assessment of Timber Structures
September 9-11, 2015, Wroclaw, Poland
A timber building made of cross-laminated timber (CLT) panels is a modular system where all panels are pre-cut in factory. On site, the single components are then assembled connecting the panels with mechanical fasteners, mainly angle brackets with nails and/or screws, hold-downs, metal plates and self-tapping screws. CLT wall panels are very rigid in comparison to its connections. Thus, connections play an essential role in maintaining the integrity of the structure providing the necessary strength, stiffness and ductility, and consequently, they need close attention by designers. However, there is still a lack of proper design rules for these connections, in particular under cyclic loads, mainly due to a large variety of connectors and connection systems. In this paper, the different properties of connections for CLT buildings, on both monotonic and cyclic behaviour, are described using recent works from different authors. From the bibliography, it is clear that experimental data, regarding both monotonic and cyclic tests, is required for the assessment of the performance of the CLT structural system attending to the interaction between rigid panels and connections. This work evidences results from experimental campaigns and numerical analysis regarding definition and quantification of the cyclic response of CLT connections. Examples regarding monotonic and cyclic tests aimed to evaluate cyclic behaviour of connections through physical parameters, such as the impairment of strength and the damping ratio, are presented and discussed.
In Japan, the moment resistance connections of large-scale timber building are inefficiency in terms of time and economic, because connections and column base hardware are custom-made to obtain the required performance. To improve this problem, it is necessary to unify standardization of their connection. At first, in this study, we focused on column-base connection, the horizontal...
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 report presents the seismic design of a 10-storey Cross Laminated Timber (CLT) building in Vancouver, BC, conducted according to the National Building Code of Canada. The multi-storey condominium consists of 20 apartments for a total floor area of about 2000 m2. First, a preliminary simplified model is formulated assuming the same stiffness per meter for each wall of the building. The Equivalent Seismic Force Procedure is applied and the results serve for a preliminary design of all the major connections that play a significant role on the lateral stiffness of the building, assuming rigid in plane floor diaphragms and well-anchored CLT walls. Based on the results of the preliminary design, a 3 dimensional finite element model is created, describing analytically the modelling approach adopted, and both the Equivalent Seismic Force Procedure (referred as static analysis) and the Modal Response Spectrum Method (referred as dynamic analysis) are applied to obtain the design forces for each wall of the building. Based on the results from the dynamic analysis, the final seismic design of the building is performed and the results are presented for connections dedicated to transfer (i) shear forces from floor diaphragms to walls below and from walls to diaphragms below, (ii) uplift forces for each wall, (iii) boundary forces between CLT panels within the same walls, (iv) boundary forces between perpendicular walls, and (v) boundary forces between CLT floor panels. All connections prescribed to provide ductility and energy dissipation are designed to fail in ductile failure mode according to the CSA 086-09 while connections that should remain within the elastic range to allow the ductile connections to yield are designed with overstrength factor.
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.
Recent architectural trends include the design and construction of increasingly tall buildings with structural components comprised of engineered wood referred to by names including; cross laminated timber (CLT), laminated veneer lumber (LVL), or glued laminated timber (Glulam). These buildings are cited for their advantages in sustainability resulting from the use of wood as a renewable construction material. Previous research has shown that timber elements contribute to the fuel load in buildings and can increase the initial fire growth rate – potentially overwhelming fire protection system and creating more severe conditions for occupants, emergency responders, and nearby properties.
The overarching goal of this project Fire Safety Challenges of Tall Wood Buildings Phase 2 (involving five tasks) is to quantify the contribution of CLT building elements (wall and/or floor-ceiling assemblies) in compartment fires and provide data to allow comparison of the performance of CLT systems against other building systems commonly used in tall buildings.
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.