This report presents bending tests performed on composite beams made from glulam beams and cross laminated timber (CLT) panels. The composite beam, with a T-cross section, represents a section of a floor element in a multi-storey CLT construction system. The shear connections used were made either of doublesided punched metal plate fasteners, either of inclined screws, or of a combination of both fastener types. The screws are used to secure the shear connection with double-sided nail plates with respect to possible separation forces between the glulam and the CLT. An additional test with a screw glued connection was made for comparison as the upper bound case in terms of composite action. The results show the beams with double-sided nail plates (with or without screws) achieved a very high level of composite action and an overall satisfactory behaviour. Almost full composite action was achieved for the screw-glued composite beam. A detailed design example of the beam element according to the Eurocode 5 and Finnish National Annex is presented.
This thesis focuses on the development of composite floor solutions where Cross Laminated Timber (CLT) panels are used as a base element. Preliminary investigations on shear connections between prefabricated concrete beams and CLT panels were performed. The focus is on investigations on glulam-CLT composite beam elements, and the mechanical shear connectors used to achieve composite action.
The new shear connections system evaluated in this thesis for glulam-CLT floor elements consists of double-sided punched metal plate fasteners. In order to secure the shear connection made with double-sided nail plates and to improve the shear behaviour of the joint, a combination with inclined self-tapping screws was evaluated through a shear test programme. It was found that the double-sided punched metal plate fasteners and inclined screws can effectively be combined.
This report presents bending tests performed on composite beams made from glulam beams and cross laminated timber (CLT) panels. The composite beam, with a T-cross section, represents a section of a floor element in a multi-storey CLT construction system. The shear connections used were made either of doublesided punched metal plate fasteners, either of inclined screws, or of a combination of both fastener types. The screws are used to secure the shear connection with double-sided nail plates with respect to possible separation forces between the glulam and the CLT. An additional test with a screw glued connection was made for comparison as the upper bound case in terms of composite action. The results show the beams with double-sided nail plates (with or without screws) achieved a very high level of composite action and an overall satisfactory behaviour. Almost full composite action was achieved for the screw-glued composite beam. A detailed design example of the beam element according to the Eurocode 5 and Finnish National Annex is presented.
A new shear connection system was tested in order to be used in off-site manufactured cassette floor elements made with glulam beams and Cross Laminated Timber (CLT) panels. The shear connection proposed is made with double-sided punched metal plate fasteners, connecting CLT and glulam members to form a T-cross-section. Due to the lack of withdrawal capacity of punched metal plate fasteners, the shear connection must be secured with screws to resist separations forces which may occur between the members in the floor element.
Shear tests were performed on glulam-CLT joints made with double-sided punched metal plate fasteners and with inclined self-tapping screws as reference cases to compare to joints with both fastener types combined. Each fastener type is characterised by a specific load-slip curve and different values for the yield slip, slip at maximum load and failure slip. These parameters can be used to evaluate the compatibility of the different fasteners and their combined effect in a joint. The test results show that there is a significant contribution from both the double-sided punched metal plate and inclined screw fasteners to the strength and stiffness of the combined joints.
Due to the fact that the individual fasteners reach their maximum load for different slip values, the load-carrying capacity of joints with combined fasteners is somewhat lower than the sum of the individual fasteners load-carrying capacities. The slip modulus of the combined fasteners may be estimated as the sum of the respective slip modulus of each fastener due to the compatible behaviour of the fasteners in the serviceability limit state.
