2019-02-12-minutes-solid-waste - Laserfiche WebLink

Home Browse Search

Patti Johnson From: Robb Dibble <Robb@DibbleEngineers.com> Sent: Sunday, February 10, 2019 4:38 PM To: Mike Flory; Patti Johnson Cc: Travis Colliander Subject: RE: Engineering Report Good afternoon Mike, Your most welcome. We appreciate assisting the County on this, and any future work. I'm out both tomorrow and Wednesday for meetings, but I'll do my best to get this out by end of the week. Travis and I chatted on the way back a fair bit and that the original drawings indicated a fairly heavy live load capacity for the designated "Storage" as shown on the plan, that strongly suggests there is inherent strength in the long span joists. The strength will likely allow for a fairly good loading of filing racks above. I was working on the report today with some early interpretative calcs. Existing 5 Drawer cabinets weight about 102 PSF, based on a 28" deep drawer and that is assumed the cabinets without boxes stacked on them. The new racks are definitely more efficient at 6 open shelves with files sticking out past the 12" shelf width, effectively concentrating the loading. Based on the banker box sample weight, the new shelving system is closer to 212 PSF (Same as PLF based on the 12" width. Then put two back to back shelves, is 424 PLF of the combined new shelves. Then we consider the clearance on the front sides for access to average it down. Further we need to consider bracing these shelves for lateral stability. The resulting issue will be more of a deflection compatibility. Cracks by themselves may not represent a failure, just an elastic strain yielding of the trusses resulting in downward movement. Floors and roofs are intended to move. Calculating the long span over the Commissioner meeting room at 30'x 12" = 360" span. Based on a code allowed Live Load Deflection of L/360, that would suggest that the 2nd floor bar joists could result in an expected downward deflection of 1" and still be with in code. That will probably result in substantially more ceiling cracking, and crushing of interior non-bearing partition walls, like the one at the back of the Commissioner's room. The ceiling assembly which is a fairly rigid 10 PSF and probably considered.a brittle acoustical stucco type ceiling implies cracking should be expected. That's in comparison to the adjacent 16' span Live Load Deflection of only a %" tolerable deflection. The architect who laid out the storage load over the long span joists versus the adjacent shorter span joists should have considered the deflection and should have laid out the storage room better in space planning way back in the day, but that's hindsight. With all that said, my hunch says that I think there will be a mix of the Courts getting a layout plan that they will need to live with using their shelving at some spacing, and the Owner will get a confirmation and level of comfort that what is being installed shouldn't bring down the house. I think that is the 3rd party recommendation and confirmation that will bring peace to the issue. Please await for the report. Thanks,