A concrete-filled steel tube (CFT) column system has many advantages compared with ordinary sttel or reinforced concrete system. One of the main advantages is the interaction between steel tube and concrete: occurrence of the local buckling of steel tube is delayed by the restraint of concrete, and the strength of concrete is increased by the confining effect provided from the steel tube. Extensive research work has been done in Japan over the last 15 years, including "New Urban Housing Project" and "US-Japan Cooperative Earthquake Research Program", in addition to the work done by individual universities and industries, which has been presented at the annual meeting of Architectural Institute of Japan (AIJ). This paper introduces the merits, design provisions and recent construction trends of CFT column systems in Japan, and discusses the results of trial designs of CFT theme structures which have been carried out to look for the advantages in the performance and construction cost compared with other constructional system.
The paper presents some experimental data and phenomenon on bracket anchor connections for Cross-Laminated-Timber. The goal of this research is to provide a better understanding of the seismic performance of bracket connections subjected to seismic actions and how to choose and design bracket connections for Cross-Laminated-Timber structures. Test configuration and experimental setups are illustrated in details; cyclic displacement schedules of the connections in two directions are presented considering that CLT wall has horizontal sliding in the plane and uplift at the end in quasi-state tests. Different failure modes and force transmission mechanisms of different connections under the loading protocol were analysed. And important quantities for seismic design such as strength, and stiffness, equivalent yield load, peak load and ductility of the connections are evaluated and compared among different kinds of connections; an excellent connector is revealed in ductility and load capacity by test data analysis. In addition, some suggestions to choose and design bracket anchor connections are given.
CLT wall panels having an opening were subjected to horizontal loading and the failure process of CLT around the opening was compared with the simulation by Finite Element Method. Three types of CLT wall panels of 3500mm length and 2700mm height had an opening of 1500mm length and 900mm to 2000mm height at the center of the wall panel. During the racking test of wall panel cracks appeared at the corner of the opening. The wall panel was modelled with three models. One included a single orthotropic plane element calculated from the mechanical properties parallel and perpendicular direction of lamina layout (Model I). Another included two orthotropic plane elements crossed each other and connected at each nodal point based on the mechanical property of lamina composing the panel (Model II). The third model included laminae of 30-by 120mm cross section arranged vertical and horizontal directions (Model III). The simulation by each model predicted comparatively well the initial shear stiffness of CLT wall panels and the initiation of cracks at the corner of opening.
In this paper, the results of lateral loading tests on two types of CLT shear wall systems with an opening are summarized, one is the shear wall system with assembling narrow size CLT panels and another is that using one large size panel with an opening. 8 types, 13 specimens in all were tested. Load-displacement curves were obtained and characteristic values of shear performance were derived. As a result, the assembly system revealed higher ductility because of the ductility of connections between panels, while the rapture of large panel system was brittle though the shear capacity was higher than the assembly system.
