Leaderboard

higher the story, lower will be the reinforcement in column due to less gravity load and seismic shear in it. But beam reinforcement remain same in all stories because the gravity and seismic load remain same in beams in all stories. As you go up, the cloumns become weaker and weaker bur strength of beam remains same so the C/B capacity ratio (opposite of B/C capacity ratio) become lower and lower. on top of that, at the top story joints there in only one column end at the bottom of the joint but two beam ends so two beam capacity is added for calculation for C/B capacity ratio but there in only one column capacity. So in the top joint C/B capacity is even drastically reduced. Wheres in all other stories except the top story each joint has at least to column ends and the joints in the middle have two beam ends. Here, moment capacity of two columns are added to calculate B/C capacity ratio. Also, moment capacity of two beams are added.