A private client wishes to add load to their roof. Thus, I am analyzing their most critical monoslope wood truss in RISA3D. The span is 50 feet, and the slope is 1:12. The truss is in service. I documented my own measurements and other truss details for the analysis. Later, I procured the manufacturer’s drawings.
Applying the manufacturer’s load combinations to my model gets me within 5% of their internal forces. This tells me that my model is sound. However, my unity checks are way off. Some of my webs are at 200% DCR, with excessive axial force demand. Since my loads are not the problem, I am digging into the capacities.
Is there a significant difference in truss capacity between the NDS and TPI? RISA3D performs unity checks to ASCE 7 (NDS), not TPI. Where am I going wrong?
Applying the manufacturer’s load combinations to my model gets me within 5% of their internal forces. This tells me that my model is sound. However, my unity checks are way off. Some of my webs are at 200% DCR, with excessive axial force demand. Since my loads are not the problem, I am digging into the capacities.
Is there a significant difference in truss capacity between the NDS and TPI? RISA3D performs unity checks to ASCE 7 (NDS), not TPI. Where am I going wrong?
