N. Araki, Associate Professor, Department of Architecture and Architectural Engineering, and Takiyama, Kyoto University, Dr. Y. Kitamura, Chief Designer, M. Maeda, Chief Engineer, Kozosoken Corporation, H. Nagae, Researcher, Hyogo Earthquake Engineering Research Center, National Research Institute for Earth Science and Disaster Prevention, Dr. N. Yoshida, N, Research Engineer, Katsura Int’tech Center, Kyoto University.
We report our research projects on seismic rehabilitation of historic brick buildings, wherein un reinforced walls are strengthened by inserting stainless pins. In strengthening historic buildings, preservation of their appearance, durability of strengthening materials, and minimization of parts to be damaged pose main difficulties. Inserting stainless pins into un reinforced walls is known as an effective method to overcome the difficulties, and has been applied to some buildings in practice in Japan. In the method, stainless pins are inserted from the mortar joints between bricks in the direction of 45 degree from the vertical, while preserving the appearance of the walls. No research efforts, however, have been devoted that evaluate the improvement of the seismic performance by the method, taking its unique way of inserting stainless pins into account. Our research aims to evaluate and improve, if necessary, the seismic performance of the reinforced walls through a set of experimental studies. As the first step toward this goal, we have conducted cyclic out-of-plane bending tests. The main findings from the tests can be summarized as follows: (1) Significant differences exit between the restoring force characteristics in one and the other loading directions. The reason of this is that the reinforced wall is subject to tension of stainless pins in one direction, while it is subject to dowel action of the stainless pins in the other direction. (2) Too much increase of the number and/or strength of stainless pins decrease the capacity of the reinforced wall. The increase makes the difference greater between the reinforced and un reinforced parts of mortar joints .The unbalance of the strengths causes stepping pattern fracture at the mortar joints where no stainless pins go through. Once stepping pattern fracture takes place, no tension element exists in one loading direction, which leads to loss of capacity.
