DEVELOPMENT OF DUCTILE MOMENT-RESISTING JOINT BASED ON A NEW IDEA FOR GLULAM PORTAL FRAME STRUCTURES. Kohei Komatsu 1 , Shouichi Nakashima 2 and Akihisa Kitamori 3 ABSTRACT: A new ductile glulam moment-resitting joint system was developed by making use of friction resistance of steel splice joint for before-yielding revel and for post-yielding level embedment resistance of steel bolted joint was used. The basic idea has been recognized by the author through past experiments on glulam splice joints using drift-pins and this time the same idea was extended to glulam moment resisting joint system using Lagscrewbolt (LSB). At this moment, only limited number and type of experiments have been conducted but good coincident between prediction and experiment was obtained, therefore using this limited results, we would like to introduce a concept of new ductile glulam moment-resisting system which will be usable for low-rise glulam semi-rigid portal frame structures. KEYWORDS: Friction Joint, Post-Yielding Embedment of Steel, Lagscrewbolt, Glulam, Ductility 1 INTRODUCTION 123 On May in 2010, a law called as “Promoting Timber Structures for Public Low-Rise Buildings” was proclaimed in Japan. This law led good wind blow towards timber structures. So as to meet this law, we need to develop a new moment-resisting joint system which should satisfy the following requirements. 1) High initial stiffness 2) Clear yielding point 3) Controllable ultimate strength 4) High energy absorption performance (Ductility) 5) Easy repair after suffering devastating earthquake 6) Low cost 7) Versatility of existing technologies In order to satisfy the above mentioned criteria, we developed a new method as shown below. 2 BASIC CONCEPT 2.1 Conventional glulam LSB joint Figure 1 shows a schematic explanation of conventional LSB glulam joint with steel splice joint connected by 1 Kohei Komatsu, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasyou, Uji, Japan, Email: [email protected] 2 Shouichi Nakashima, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasyou, Uji, Japan, Email: [email protected] 3 Akihisa Kitamori, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasyou, Uji, Japan, Email: [email protected] high tension bolts (HTB). In this joint, as HTB joint is almost rigid, only elastic deformation between LSB and glulam affects on the initial stiffness but its quantity is very small thus the apparent initial stiffness of the whole serial joint is very high. Once tensile force reaches to P slip , which indicates load at HTB starts to slip, load drops suddenly with big sound. After then load once again rise up steeply because HTB contacts with steel plate. If the ultimate tensile strength of LSB P LSB is lower than the ultimate strength of HTB P HTB , whole joint will lose its performance due to pull-out failure of LSB from glulam. This type of rather brittle failure mode was observed in previous LSB joint actually. Fig.1 Load-deformation behaviour of conventional LSB joint connected with steel splice HTB joint. .