Laserfiche WebLink
8 of 234 <br />14.3.1 Energy Diss,pation Systems - <br />General Requirements <br />For this alternative seismic upgrade, a Limited Performance Objectives of Life Safety and <br />Collapse Prevention under 50%/50yr demands apply. Multiple analysis runs indicate that the <br />damping devices have reserve capacity to address events well beyond the target 50%/50 year <br />demands The pnmary Identified deficiency Is the performance of the lowest level of columns ' <br />between Ll-L3. On this story alone, eight energy dissipation devices are in each prinapal <br />direction of the buildings with four located on each side of the center of stiffness of the lowest <br />story Reserve capacity as required in point 14.31 1, having velocity dependent devices capable <br />of sustaining the force and displacement associated with 200% of the maximum calculated <br />velocity for that device at the 50%/50yr level, is satisfied: For an exponent a of 0 3, if velodty <br />increases by a factor of 2, damper force increases by 2'0.3 or 1.23. Maximum damper force of <br />367k found at 50%/50yr increased by 1 23 is 452k, still well within manufacturefs stated ultimate <br />capacity. Connections are designed for 500k damper force to provide an additional margin. <br />1432.4 <br />Intended manufacturer tests each damper before shipping to maintain dose tolerances on <br />damper design properties Code recommendations consider a damping value range from <br />Upper- and Lower-Bound Design 1.15'nominal design property to 0 85'nominal destgn property. Runs used to determine <br />and Analysis Properties acceptance based on 0 85,1.0 and 1.15 times nominal design damping properties compare <br />results at Level 1-3 and Level 3-4 columns, finding only small changes in DCR values and <br />somewhat larger changes in damper forces.