Reinforced concrete corner for timber frame moment resisting joints – Design and experimental assessment

Abstract

In this paper, a new type of moment-resisting joint for timber frames is proposed and discussed. In short, the prismatic volume of the corner is made up of high-strength concrete reinforced with steel bars bonded in both the timber beam and the column, forming a composite joint. The analytical and experimental study of the resisting moment, stiffness and failure modes of the proposed joint are carried out. The role of the timber cross section and diameters of the steel bars on the resisting moment are investigated, based on an assumed mechanical model for the stress-strain relation. The failure mode based on the yielding of the steel bars is privileged towards the timber shear failure of the bonding of the bars, given its ductile nature. Series of knee joint specimens with steel reinforcement bars of two different diameters were produced and tested to failure. The experimental results showed good agreement with the ultimate moment estimates obtained from the proposed analytical method. Specimens of polygonal bolted joint were also tested, for the sake of comparison. Both the rotational stiffness and bending strength are much higher than those of the traditional bolted joints tested. It is concluded that this joint is structurally effective and has, consequently, good potential of application.