Single Story Deflection/drift
Single Story Deflection/drift
(OP)
I am designing a single story building, 17.5 feet in height. The footprint is 51 ft by 56 ft. It consists of bar joists spanning the 56 foot direction (for a number of reasons), supported on WF beams along the 51 dimension. The 51 ft ends are 2-bay rigid frames with steel tube columns and moment connections to the wide flange beams. The 56 foot edges are also 2-bay rigid frames using 30kcs joists due to the longer spans. I am checking the drift on the frames using ASCE 7, Appendix C, cc1.2 = L/400. I am finding this limits me to about 0.6 inches of deflection. The result is my columns are 10x10x3/8 and 30KCS5 joists (highest series) are required. This all seems very heavy for a small, one story building, with basically about 4 kips wind load at each frame. This seems unusual to me but I have checked it several times. Is the L/400 (0.6 inch) drift limit correct? Seems very tight. Have others run into this issue?






RE: Single Story Deflection/drift
RE: Single Story Deflection/drift
RE: Single Story Deflection/drift
RE: Single Story Deflection/drift
RE: Single Story Deflection/drift
RE: Single Story Deflection/drift
For a wind event, it is common to assume that some of the moment is resisted at the base. During a webinar, it was recommended that the point of zero moment be 1/4 to 1/3 of the column height.
I think that this is related to settlement. The base is pinned under sustained loads, and fixed under temporary loads.