Nodal Displacement at Ridge/Apex node

Question

Hello, 
 I have modelled a space braced frame industrial warehouse and I would like to have the vertical deflection of the Rafter for checking serviceability limit. The span of rafter is 16.9m. I find ridge nodal displacement is higher than L/300 (as per EN 1993) and member displacement is within limits. Please advise is taking the member displacement for permit report is correct since I believe that ridge node vertical displacement (Y dir) is global displacement. Kindly confirm. (STAAD model attached for ready reference. 
 B4-8 MODEL 16.04.20.std

Modestas · Accepted Answer

I would suggest you to define DJ1 and DJ2 parameters for each rafter on each plane separately. For example, for rafters 124 and 125, define DJ1 as node 22 and DJ2 as node 114. In such case, the deflection of rafters 124 and 125 will be checked considering the physical length of it (between nodes 22 and 114). The displacement of apex nodes should be checked manually. 
 You also need to have a TRACK 4 design parameter to invoke the deflection check as per EN1993-1-1:2005 code. 
 Also, there is no need to have PERFORM ANALYSIS and CHANGE commands after each load case. One PERFROM ANALYSIS command is enough after the last load case.

Modestas · Answer

TRACK 4 performs the deflection check while TRACK 2 performs the strength check only. To have both checks, you need to have 2 different code checks. I am not sure what is your requirement, but I think you should check the section displacement of each rafter and probably the nodal vertical displacement of apex node.