STRUCTURAL REDUNDANCY IN CROSS-LAMINATED TIMBER BUILDINGS

Transcription

1 STRUCTURAL REDUNDANCY IN CROSS-LAMINATED TIMBER BUILDINGS Ildiko Lukacs 1, Anders Björnfot 2, Themistoklis Tsalkatidis 3, Roberto Tomasi 4 ABSTRACT: In high timber structures, cross-laminated timber panels are common structural elements. The wall and floor panels are typically connected with steel plates, angle brackets, hold-downs, and screws. Based on analytical research, it seems that panel-to-panel connections give additional stiffness due to structural redundancies resulting from transversal wall and floor elements. The purpose of this paper is to investigate the effect of structural redundancy of common CLT wall-to-floor panel configurations on the global system stiffness. As a first phase, a Finite Element (FE) study is performed to investigate the behavior of a single shear panel subjected to both horizontal and vertical loads. In this paper, the behavior of the FE model is verified with previous tests results of CLT shear walls. The next phase presented in the paper outlines future work of a Finite Element study with different CLT wall configurations with longitudinal and transversal CLT panels connected to each other. KEYWORDS: System stiffness, FE modelling, Timber shear-walls, Structural Redundancy, Cross-Laminated Timber (CLT), Steel connection 1 INTRODUCTION 123 Cross-laminated timber (CLT) panels of varying dimensions, placed in a crosswise manner to each other, form the typical contemporary high-rise timber building [1]. CLT as wall and floor panels are typically connected to each other with steel plates, steel brackets and long wooden screws, creating a structural system of interconnected CLT panels that by nature is stiffer than its individual parts. Monitoring horizontal deflections of an eight-story CLT building, situated in the southeast of Norway showed wind-induced deflections at the top story of less than 0,5 cm [2] which was surprising considering that theoretical calculations indicated that five times higher deflections was to be expected. The small measured deflections raise some questions about the actual stiffness of high-rise CLT buildings, indicating that a CLT building is stiffer than what academics and practitioners alike have previously thought. Normally, the building stiffness to horizontal loads are calculated from the amount of shear walls and their individual stiffness in the wind direction. However, it seems that panel-to-panel connections gives additional stiffness due to structural redundancies resulting from transversal wall and floor elements [3]. A potential explanation for the structural redundancy is the fact that the lateral stiffness of a typical shear panel in high-rise CLT buildings is mainly affected by rigid-body 1 Ildiko Lukacs, Norwegian University of Life Sciences, ildiko.lukacs@nmbu.no 2 Anders Björnfot, Norwegian University of Life Sciences, anders.bjornfot@nmbu.no rocking ( 80 %) while the contribution from rigid body translation and panel shear is substantially smaller ( 20 %) [3,4]. In practice, the rigid-body rocking of a shear panel is partially restricted by structural system redundancies obtained by continuously placed mechanical connections between timber shear panels and transverse wall- and floor panels. In addition, the effect of friction between panels is rarely considered as a factor that increases the global stiffness of a high-rise CLT building. Consequently, the aim of this research is to: Explore the effect of structural redundancy of common CLT wall-to-floor panel configurations on the global system stiffness. First, a Finite Element study is conducted to investigate the behavior of a single shear panel subjected to both horizontal and vertical loads. The Finite Element model is then calibrated based on results from previous tests of CLT shear walls. The second step of the paper outlines future work of a Finite Element study of different configurations of longitudinal and transversal CLT panels connected to each other using various types of mechanical connectors. The investigated configurations are standard combinations of wall and floor panels typically found in high-rise CLT buildings, exemplified by an eight-story CLT building situated in Norway. 3 Themistoklis Tsalkatidis, Norwegian University of Life Sciences, themistoklis.tsalkatidis@nmbu.no 4 Roberto Tomasi, Norwegian University of Life Sciences, roberto.tomasi@nmbu.no

2 2 CASE STUDY The eight-story case study building (Figure 1) is located in the south of Norway. The choice of case study is based on ease of access to detailed information of the structural system. Data was collected by reviewing construction drawing and other relevant documentations, from observations through site visits, and through open interviews with designers, building residents and fellow researchers studying the performance of the building from different aspects, see e.g. [1,2,5]. Each room has a bedroom and a bathroom. During assembly of the building, the bathrooms arrived as prefabricated modules straight from the factory. Platform framing was the production technique used to assemble the pre-cut CLT wall and floor panels. 2.1 Stabilizing system The building has an elevator shaft and a staircase placed in the center of the floor (Figure 2) that functions as a core to stiffen the building. The building has a symmetrical distribution of shear walls (marked as sw in Figure 2) that repeats itself on every floor of the building. A shear wall is here defined as For our problem as shear wall, we define a CLT panel that distributes shear forces to adjacent panels through mechanical connectors (brackets, screws, etc.) and where hold-downs are arranged in each end of the panel to balance the uplifting forces due to rigid body rotation. Figure 1. Left:The Eight-story CLT building. Right: Buckling of hold-down steel plates placed in the elevator shaft The case building houses student apartments in eight floors of similar layout. The basic characteristics of the building are given in Table 1 below. As all wall and floor panels are made of CLT (with C24 strength class), the concept of a pure CLT building has a meaning (Table 2). A basic wind velocity of 22 m/s and a characteristic snow load of 3.5 kn/m 2 typifies the geographical location of the building. The short side of the building is located in the east-west cardinal direction. Table 1. Case study building characteristics (after [1]) Parameter Value Unit Length m Width m Height m Nr. of floors 8 # Rooms / building 127 # Net area / floor m 2 Net area / building m 2 CLT wall panels 3 layers 90 mm 5 layers 100, 120, 130, 140, 160, 180 mm CLT floor panel 5 layers 180, 220 mm CLT roof panel 5 layers 200 mm Wood amount total m 3 Hold-down steel plates kg Shear steel plate 1919 kg Self-tapping screws 6124 # Steel brackets 390 # The building has a rectangular floor plan layout where each floor is composed of two apartments for handicapped people, normal student apartments, and a common area used as kitchen and living room. In total there are 127 student rooms divided evenly between the eight floors. Figure 2. Designated shear walls (sw) and identification of redundant wall configurations (C, L). Figure after [1] The total length of designated shear walls are approximately 46 m per floor, which equals about one fourth of the total wall length. Shear forces are being distributed using shear plates and brackets (Figure 3) while long steel plates, ranging from the foundation to the roof, are placed at each end of the designated shear walls (Figure 3) to resists overturning. However, failing to consider the cumulative shrinkage perpendicular to the grain of each floor panel has resulted in an undesired buckling of the steel plates (Figure 1) [2] which limits the functionality of the steel plates. Figure 3. Left: Shear plate and hold-down plates ranging from the foundation to the roof. Right: Inclined self-tapping screws and steel brackets. Illustrations from [1]

3 As rigid body rotation is the significant deformation mode [1], limiting the rotation of the wall would give a substantial increase in shear wall stiffness. Therefore, a redundant wall configuration is defined as a shear wall that is connected to a perpendicular wall at one (L form) or both ends (C form). The most significant part of this definition is that there must be a shear connection (Figure 3) between the shear wall and perpendicular wall(s). Based on this definition, five C and one L configurations are identified per floor (Figure 2). 3 CLT SHEAR WALL MODELLING There are a few different approaches for Finite Element (FE) modelling of CLT shear walls. Sustersic & Dujic [6] presented an FE model using shell elements and linear or nonlinear springs arguing that the stiffness of the shear wall is based predominantly on the stiffness of the mechanical connectors. In this case, the connectors can be brackets or screws. The authors [6] also presented a simplified FE model that consists of a truss with a diagonal element where the stiffness of the connectors where modeled as springs in the corners (Figure 4). Figure 4. CLT Shear wall (right) substituted with a model of a truss system with a diagonal (left). Figure adapted from [6] The simplified truss model (Figure 4) should mainly be used for nonlinear dynamic analysis where the truss, representing the CLT panel, have high stiffness. Further simplification of the truss is also presented where the stiffness of all individual components of the shear wall (e.g. CLT panel, angle brackets, hold-downs, screws, etc.) are substituted by a diagonal elements. This final simplification is, according to the authors [6] more proper for linear elastic analysis of CLT shear walls. Flatscher & Schickhofer [7] describes a CLT shear wall FE model, where the walls were modelled individually as shell elements. In addition, the connections joining the CLT panels were modelled as simply supported linear springs. Similar to the previous author, a simplified beam model was introduced composed of infinitely stiff columns and semi-rigid supports representing the shear wall (Figure 5). Based on this simplified model, the authors [7] performed a linear modal analysis. Follesa et al. [8] suggested a 3D numerical model using shell elements (4-noded, 24 DOF) representing walls and truss elements (2-noded, 6 DOF) representing the connections between wall panels. Some model simplifications were made, e.g., floor panels were assumed to be in-plane rigid, no out-of-plane stiffness were taken into account for the floor panels, connections between panels were considered rigid, and the holddowns were not defined in the model [8]. Figure 5. CLT shear wall (right) substituted with an infinitely stiff cantilevered column (left). Figure adapted from [7] Calderoni et al. [9] created a FE model of a three-story CLT wall. The CLT panels were modeled as shell elements with an elastic behavior and the connections as frame elements with non-linear axial behavior. The holddowns were given a non-linear axial behavior in both tension (steel) and compression (timber crushing). Frame elements were also used to model non-linear shear behavior in connection zones. Rinaldin et al. [10] also represented the CLT shear wall with shell elements given elastic isotropic properties. The connections were modeled with nonlinear spring elements. Although, recent research (see e.g., [5]) has indicated great potential in improving the stiffness of the CLT panel itself by changing the panel characteristics (Figure 6), e.g., board width (b) and inclining board layers (ϕ), the above research concludes that the stiffness of the mechanical connectors governs the behavior of the CLT shear wall. Therefore, the shell element, representing a CLT panel with high bending and shear stiffness is a natural choice. However, for the mechanical connectors there seems to be no commonly accepted solution. Figure 6. Illustration of parameters affecting the shear stiffness of a CLT panel. Figure adapted from [5]

4 4 SINGLE SHEAR WALL BEHAVIOUR The first step in order to investigate the structural redundancy of CLT buildings is to create a single shear wall FE model used as a base case. A single wall gives a better understanding of the CLT shear wall behavior. The model of the single shear wall is calibrated with test result to have valid FE model from where to model and analyze other configurations of CLT shear walls. 4.1 SINGLE SHEAR WALL A shear wall is a vertical element of the structural system used to resist against horizontal forces (Figure 7). Common horizontal forces in a building are, for example, wind and seismic loads. In addition to the horizontal load, the shear wall also needs to transfer vertical loads (gravitational loads) from the above structure, which can be another floor or the roof of the building. Simple metal fasteners, connectors and hold-down anchors [4] connect CLT panels to each other [11]. in the shear wall. One effect is the sliding of the wall and the other effect is the uplift. These effects can be avoided by using angle brackets and metal hold-down anchors attached to the CLT panel on the bottom side. The goal of the hold-down anchors is to withstand the uplift associated to the vertical force between panels or foundation [11]. These connectors are normally positioned in the corners of the shear wall (Figure 7). Shear connections (e.g., angle brackets) are mainly designed to resist panel sliding and to transfer shear forces but they are actually active in two directions, i.e. they resist both horizontal and vertical forces [12]. The ability of the angle brackets to resist vertical load is exemplified in Figure 8, showing deformed angle brackets after shear tests of a CLT wall. Figure 8. Illustration of the vertical stiffness of angle brackets Since the shear wall needs to resist dynamic loads (e.g., wind and earthquake), the angle brackets and the holddown anchors need to demonstrate a ductile behavior. Through the ductile behavior, the shear wall is able to resist a high dynamic load without deformation leading to connection and system failure. This is why the non-linear behavior of the connectors should also be considered in an FE model studying shear wall redundancy. As the angle brackets have vertical stiffness, as well as horizontal, a numerical model must also consider the nonlinearity of the connectors. Figure 7. Cross-laminated timber (CLT) shear wall 4.2 STIFFNESS OF SINGLE COMPONENTS Single components for the shear wall are represented by the following characteristics: geometry, material, mechanical connectors, effect of vertical load, and the non-linear behavior of the components. The geometry of the panel is considered a square with the same height as length (h=l). The number of layers composing the CLT panel determines the wall thickness. Wood has different behavior depending on the grain orientation (radial, tangential or longitudinal). These directions refer to the orthotropic behavior of the CLT panel. The CLT panel is an orthotropic material as it has different properties in each orientation. However, the stiffness of the CLT shear wall is not influenced by the material properties in different directions. According to Tomasi & Smith (2014) [11] two types of connections are used corresponding to counter the forces 4.3 EXPERIMENTAL RESULTS In understanding the behaviour of CLT shear walls, numerical analysis must be combined with test results to properly describe its performance. In the following part one such test experiment is presented based on a single CLT wall test. According to Tomasi [13] the purpose of the test is to assess the CLT shear wall behaviour in different load cases. For the test, a 3-layered CLT panel was used, with square geometry (2500x2500 mm 2 ). All of the layers have the same thickness, together forming a 90 mm thick panel. For hold-downs, typical steel connectors are used and for the angle brackets, traditional steel connectors. These connections were placed just on one side of the wall panel (asymmetric setup) and connected using regular ring nails (4x60 mm). Two different test setups of the bottom connections are used: a concrete foundation and a wooden floor. In the course of the testing period, the test arrangements permitted to apply immediate gravitational force

5 (vertical) and displacement (horizontal). The following units were measured: wall uplift, horizontal displacement between wall and foundation, in-plane shear deformations, applied horizontal force, and the deformation of the hold-downs. In the following part, experimental test results are presented based on the research by Tomasi [13]. Figure 9 presents horizontal force vs. deformation diagrams from two test setups with the same panel configuration and connectors. The difference between them is the applied load on the CLT panels. In the first case, the horizontal load acting on the wall panel (L0-AB200-HD620). The second case has, in addition to the horizontal load, a constant vertical load acting on the wall panel (L20- AB200-HD620). The vertical load was applied constant during the whole experiment. prevents the sliding of the panel resulting from the horizontal load acting on the wall panel. Figure 10 presents the basics of the FE model. To stop the wall panel penetrating into the floor panel, a pinned support is proposed in the lower right corner. If the support is not used, than a very stiff element needs to be defined, that will have the same function to block the penetration. Figure 10. Illustration of numerical model with CLT panel, hold-downs (HD), angel brackets (AB) and applied loads Figure 9. Force--deformation curves for shear wall with applied horizontal load (L0-AB200-HD620) and horizontal/vertical load (L20-AB200-HD620) 4.4 CLT SHEAR WALL NUMERICAL MODEL According to the previous sections, the first step in understanding the structural redundancy of CLT structures is to create a numerical model of a single CLT shear wall (base case). A numerical model of the tested wall (Figure 9) is created based on previous research and experimental test results in order to verify the behavior of the model. This step is important because further modelling will be based on this case. As base case, a single shear wall connected at the bottom of the CLT panel is studied. This model is a 2-dimensional (2D) simplified version of the wall. In this case, the vertical CLT panel is modelled as a thick shell element with boundary conditions on the bottom. These boundary conditions are influenced by the connections used to transfer the loads through the panel to the floor/foundation. As connections, link elements are used in the model. These link elements can have nonlinear compression and tension behavior, or both. Two main types of connectors are distinguished; the holddown and the angle bracket. The hold-down (HD) stops the uplift of the panel, while the angle bracket (AB) As shown in Figure 10, for the hold-downs (HD) vertical stiffness is considered and for the angle bracket (AB) both vertical and horizontal stiffness is taken into account in the model. The HD and AB properties match the steel connector properties that were used in the test [13]. In Table 2, the main characteristics of the connectors are presented. More precisely, in the model the following notation is used; HD 620 for the hold-down connectors and AB200 for the angle bracket. Table 2. Characteristics of angle brackets (AB 200) and hold-downs (HD 620). Data obtained from [13] Angle bracket Hold-down Type AB 200 HD 620 b 200 mm 80 mm h 100 mm 620 mm t 3 mm 3 mm In total, the model is built up by two HD link elements and three AB link elements. Based on the theoretical study [3, 4] the shear wall is mainly affected by rigid-body rotation, as an effect from the horizontal load. To stop this

6 rotation, and to block the wall penetration into the floor panel/foundation, on the bottom of the wall panel, between the previously presented connections (AB, HD) one more element is defined. This is also a link element, named gap, for which a very high stiffness is defined, that stops the wall from penetrating into the floor (Figure 11). is part of the shell element forming the wall panel and the other is a fixed node illustrating the foundation/floor (Figure 12). Between the connections, a gap link element is added to make sure that the wall panel does not penetrate the floor. HD AB AB AB HD Gap Gap Gap Gap Figure 11. Illustration of Link elements; hold-downs (HD), angel brackets (AB) and gap elements The shell element is defined from the characteristics of the CLT wall use in experimental test [13]. The model is a simplified version of the wall as the CLT panel s layers are not modeled. Material properties used in the FE model is orthotropic properties characterized by the timber strength class (C24) and the timber characteristics (thickness-layers, grain direction). The main orthotropic material properties defined are the modulus of elasticity, shear modulus and Poisson s ratio. Loads considered in the model are also corresponding with the test loads applied on the wall; a vertical (q) uniformly distributed load on the top and a horizontal (F) force applied on the upper-left corner of the wall. The main characteristics for modelling of the CLT shear wall are summarized in Table 3. Table 3. Summary of CLT shear wall characteristics used for modelling CLT PANEL CONNECTORS Geometry [mm] Connector type Length 2500 Hold-down HD620 Height 2500 Angle bracket AB200 Thick 90 3 layers Nails 4x60 mm Material properties HD nails [#] 52 pcs Type Orthotropic AB nails [#] 30 pcs Class C24 LOADS [kn/m] E o,mean 11 [kn/mm 2 ] q-vertical constant E 90,mean 0.37[kN/mm 2 ] own weight constant G 0.69 [kn/mm 2 ] F-horizontal irregular Poisson 0.2 q value 0 Density 480 [kg/m 3 ] q value 20 The mesh size used in the numerical model does not particularly affects the results [10]. In the process of creating the mesh also the position of the connectors has to be considered, because the goal is to accurately position the connections as close as possible to the test experiments. Based on this, a common mesh size is created that leads to uniform sized shell elements organizing the wall panel (Figure 12). The link elements that substitute the connections are connecting two nodes at the bottom of the wall. One node Figure 12. Illustration of the numerical model composed of shell and link elements 4.5 NUMERICAL MODEL ANALYSIS The model explained in Figure 12, is created with the FE software SAP2000. In the analysis of the shear wall, the following contributions are taken into account: effect of the horizontal load, effect of the constant vertical load, stiffness characteristic for the AB (vertical stiffness U1, horizontal stiffness U2 or both), HD vertical stiffness (U1) characteristic. Combinations of these are also investigated. The load effect is noted with the following specification, L represents the increasing horizontal load while the number 0 and 20 represents a constant vertical load value. The flowing cases are analysed: L0 AB(U2) HD(U1) L0 AB(U1, U2) HD(U1) L20 AB (U2) HD(U1) L20 AB(U1, U2) HD(U1). As the effect of the vertical load has not been properly investigated before [4], the application of the vertical load is of high interest in this analysis. Before the analysis is performed, the first step is to create the geometry, assign characteristics for the components, joint restrains, define loads and load cases acting on the shear wall. The next step is then to run the analysis and present the results to verified it with test results. 5 RESULTS AND ANALYSIS Figure 13 illustrates an example of a deformed shape of the CLT shear wall after analysis. The deformed shape is as one would expect the shear wall to behave loaded by a horizontal force in the upper left corner. In the previous

7 section the role of different link elements was presented. From the deformed shape presented in Figure 13, it is apparent that the link elements are activated and behave as expected as an elongation can be observed in both the hold-downs and angle brackets. In addition, the gap elements behave as intended as no penetration of the floor can be observed. numerical model and the corresponding test results for increasing horizontal load. Figure 15. Comparison between experimental and numerical modelling results without any addition of vertical loads Figure 13. Illustration of the deformed shape of the CLT shear wall after analysis Not just the deformations are as one would expected. In addition, the shear stresses have an anticipated distribution with stress concentrations evident around the location of the hold-downs and angle-brackets that are more intense than in other parts of the wall (Figure 14). In this case, the effect of the vertical load is not included. However, a variation of the wall capacity can be observed between the model results with and without the inclusion of the vertical stiffness of the angle brackets. If the vertical stiffness of the angel brackets are considered, the wall capacity is higher than in the case when just the horizontal stiffness is included in the model. However, the elastic stiffness of the shear wall with and without adding the vertical stiffness for the angle brackets remain approximately the same, a result supported by result from the analysis of the shear wall with added vertical loads (Figure 16). Figure 14. Illustration of stress concentrations at the location of the hold-downs and angle brackets The accuracy of the model is evaluated by comparing the numerical results to the experimental ones (refer to Figure 9). Figure 15 presents results from analysis of the four load/stiffness cases and a comparison between the Figure 16. Comparison between experimental and numerical modelling results with added vertical load In this case (Figure 16), the inclusion of the vertical stiffness for the angle brackets lead to an increased capacity for the wall. What can also be observed from the

8 results in Figure 16 is that there is a clear effect of the vertical load, i.e. the wall capacity (maximum force) is higher than it is in the previous case (Figure 15). 6 CONCLUSION AND DISCUSSION This paper presents a FE numerical model of a CLT single shear wall. The analysis highlights how individual components of the shear wall affect its behavior. For example, the vertical load acting on the shear wall, lead to higher wall capacity. In addition, the stiffness of the connector has a strong influence on the results. If the angle bracket is considered activated in both horizontal shear and vertical tension then the shear wall will behave more stiff and have a higher maximum capacity. The results presented in this paper have indicated the applicability of the FE model for a single shear wall. In the next step, the proposed FE model will be used to evaluate the structural redundancy of typical wall-to-floor configurations in multi-story CLT buildings. Based on the case study and floorplan in Figure 2, five typical wall-tofloor panel configurations are proposed (Table 4) as future work. The first model (0) consists of a single panel connected to the foundation and loaded in shear the base case validated in this paper. The remaining configurations have additional panels connected on different sides. For example, the T model has two additional boundaries - connection to a transversal wall panel and a floor panel. Table 4: Wall configuration for redundancy investigation Model Configuration Panel Boundary 0 1 wall 1 side T I C L REFERENCES 2 walls 1 floor 3 walls 1 floor 3 walls 1 floor 2 walls 1 floor 3 sides 4 sides 4 sides 3 sides [1] Lukacs, I. and Björnfot, A.: Structural Performance of Multi-Story Cross-Laminated Timber (CLT) Buildings. In: Proceedings of the 3 rd ICSA Conference, Guimares, Portugal, [2] Nathan, E., Thiis, T.K., Gjevestad, J.G., Björnfot, A.: Monitoring Wind-Induced Deflections of Multy- Storey Timber Housing using Global Navigation Satellite Systems (GNSS). In: Proceedings of ICWE14, Porto Alegre, Brazil, [3] Reynolds, T., Harris, R., Chang, W-S., Bregulla, J., Bawcombe, J.: Ambient vibration test of crosslaminated timber building. In: Proceedings of the Institution of Civil Engineers, Construction Materials, [4] Casagrande, D., Rossi, S., Sartori, T., Tomasi, R.: Proposal Of An Analytical Procedure And A Simplified Numerical Model For Elastic Response Of Single-Storey Timber Shear-Walls. Journal of Construction and Building Materials, pp , [5] Nygård, A.S., Bovim, N.I., Björnfot, A.: Solid Timber Shear Panels A Parametric Study of Geometries and Material Properties. In: Proceedings of the 10 th Annual Meeting of the Northern European Network for Wood Science & Engineering (WSE), Edinburgh, Scotland, [6] Sustersic, I, Dujic, Br.:Simplified Cross-Laminated Timber Wall modelling for Linear-Elastic seismic analysis. Meeting 45 of the Working Commission W18-Timber Structures; 2012, Växjö (Sweeden), paper CIB-W18/ [7] Flatscher, G., Schickhofer, G.: Shaking-Table test of a Cross-Laminated Timber Structure. In: Proceedings of the Institution of Civil Engineers, Structures and Buildings, [8] Follesa, M., Christovasilis, I.P., Vassallo, D., Fragiacomo, M., Ceccotti, A.: Seismic Design of Multi-Storey Cross Laminated Timber Buildings According to Eurocode 8 [Progettazione sismica di edifici multipiano in cross laminated timber secondo l'eurocodice 8] (2013) Ingegneria Sismica, 30 (4), pp [9] Calderoni B., Giubileo C., Sandoli A.: Criteri di Progettazione Strutturale di Edifici in Legno a Pannelli X-lam XV Convegno ANIDIS, Padova 2013, Italy. [10] Rinaldin, G., Amadio, C., Fragiacomo, M.: A Component Approach for the Hysteretic Behaviour of Connections in Cross-Laminated Wooden Structures. Journal of the International Association for Earthquake Engineering, 42: , 2013 [11] Tomasi, R., Smith, I.: Experimental Characterization of Monotonic and Cyclic Loading Response of CLT Panel-To-Foundation Angle Bracket Connections. Journal of Materials in Civil Engineering, ASCE, ISSN / (10), [12] Flatscher, G., Bratulic, K., Schickhofer, G.: Experimental tests on cross-laminated timber joints and walls. In: Proceedings of the Institution of Civil Engineers, Structures and Buildings, [13] Tomasi, R,: Seismic Behavior of Connections for Buildings in CLT. Focus Solid Timber Solutions Proceedings of the European Conference on Cross Laminated Timber, TU Graz, May COST Action FP1004, pp , 2013.