SEISMIC LENS-TYPE SHEAR PANEL DAMPER FOR BRIDGES AND BUILDINGS: INNOVATION AND OPTIMIZATION IN NATURE AND DESIGN TO ENGINEERING FIELDS
Keywords:lens-type shear panel damper, bearing, seismic control, bridge, building
Experimental study about shear panel was initiated at Fukuyama Univ.( 2005). The paper” Cyclic Shear Behaviour of Low-Yield Steels by New Shear Test Procedure” includes several findings such as:1) shear panel with LY100 is one of the best nature for energy dissipation devices, 2) by strain hardening effect of LY100, plastic zones are spread widely without local stress concentration and which result in well ductility. Then, a variety of bearing types for seismic energy dissipation has been discussed at AIT (2007), and the lens-type shear dampers have been proposed. A number of tests of lensdamper have been conducted for practical use at Nippon Chuzou, mainly for highway bridges (2008). Feasibility study project has been started for building application by a group of architects (2013). Lens-type shear panel dampers have been newly developed for highway bridges and buildings against the large-scale earthquakes. It utilizes low yield steel LY100 and concave lens shape panel. Both properties of low yield strength andof high ductility are major requirements for the damping devices. Static and dynamic tests show rectangular shapes of lateral load-displacement hysteresis loops with high quality damping. Damage and life cycles can be estimated by Miner’s rule. Prediction matches well with the testing results. Large deformation of steel with high speed strain rate generates heat of temperature of 300~450℃. Earthquake energy is converted into strain and heat, which results in large energy dissipation.
For application to bridges, both experimental and analytical works have been investigated in parallel. Random loading tests have been examined to evaluate the structural and functional performance of dampers under design level earthquakes, and at the same time to determine the safety margin against collapse under extreme earthquakes. For the evaluation of fracture, two types of prediction formula, damage index method and damage pass method are proposed. For application to buildings, seismic control stud of column type is newly proposed for low/medium-rise buildings with use of low yield steel LY 225.
The design principle of lens damper bases on nature laws of Miner’rule and similarity laws. An optimization in nature and design to engineering originates in nature law. The truth and beauty are in nature. Results of works are reported．