Timber Semirigid Frame Connection with Improved Deformation Capacity and Ductility

Abstract

The present study deals with the innovation and the possibilities of improving the design solution of a frame connection for two selected types of fasteners. All specimens were made of glued laminated timber. Dowel-type mechanical fasteners, a combination of bolts and dowels, and full-threaded screws were used for the connection. The main goal of this research was to replace the typical solution (common dowel-type fasteners) with a more modern, faster, and easier solution in order to improve the load-carrying capacity, ductility, and deformation capacity of this type of frame connection. This article also aimed to provide a detailed evaluation of the mechanical properties of the used glued laminated timber and fasteners in order to comprehensively evaluate the research task. For the design solution, a frame connection created from a system of two struts and a partition was chosen as the basis of the experimental program. Dowel-type mechanical fasteners, as well as combinations of bolts and dowels, were used for the connection; however, in addition to these standardly used mechanical fasteners, full-threaded screws were used. The article describes the use of static destructive testing to determine the ductility of the connection, considering different variations in the strengthening of the individual segments of the mentioned connection means. In the first variation, the individual components of the frame were not reinforced in any way. In the second, the crossbar was reinforced with two full-threaded bolts. In the third, the webs and the crossbar were reinforced with two full-threaded bolts. In the article, these ductility values were compared with each other and the procedure was set by the currently valid standard.

Numerical and Experimental Analysis of the Load-Carrying Capacity of a Timber Semi-Rigid Dowel-Type Connection

“…The stress during the collapse reaches the ultimate strength and the maximum plastic deformation reaches the value of 3.68%. On the basis of the experimental testing of used fully threaded screws (see the publication Johanides 2022 [ 43 ]), it can be concluded that the numerical model did not fail due to the rupture of the fasteners. This fact was also verified and confirmed by the experimental testing of those connections.…”

“…Four-point bending tests were performed to verify the properties of the used timber. Results of the tests have already been published in Johanides 2022 [ 43 ]. The stands were made of a cross-section of 100/300 mm and the rung was made of a cross-section of 100/300 mm.…”

“…The stands were made of a cross-section of 100/300 mm and the rung was made of a cross-section of 100/300 mm. The material properties of the fasteners were also experimentally verified by tensile tests in Johanides 2022 [ 43 ].…”

“…The values of the plastic behavior of timber (see Table 4 ) and the plastic behavior of steel (see Table 5 ) were obtained based on an experimental testing. The results of the testing have already been published in [ 43 ].…”

“…Small semi-rigid connections with the two already mentioned types of fasteners were subsequently created for a detailed analysis of the connection. The article by Johanides 2022 [ 43 ] dealt with the determination and comparison of the ductility of this connection. The article by Johanides 2022 [ 44 ] dealt with the determination and comparison of the rotational stiffness of this connection.…”