API-650, Appendix R, Equation (g)
API-650, Appendix R, Equation (g)
(OP)
Addendum 1 of API-650 11th Edition includes a new equation (g) in Appendix R. This equation combines the dead, live and external pressure loads attributed to an internal floating roof (IFR) to the dead, live and ext. pressure loads acting on the fixed roof.
Note 1 in the appendix indicates to add the IFR loads as point loads, since the loads from the IFR are concentrated on the fixed roof at the point where the IFR suspension cables connect to the fixed roof.
I don't know how to apply this equation since the loads on the fixed roof are uniform loads applied to the entire roof surface (pounds per square foot) and the IFR loads are point loads (pounds). I have inconsistent units. Advice?
Also, the variable (T) for equation 5.10.6.1 still indicates that it should be the larger of Appendix R equations (e)(1) and (e)(2). It was not expanded to read "or greater of (g)(1) or (g)(2) if applicable", which makes me wonder if equation (g) is intended to be applied to umbrella roofs.
Typically we suspend our IFR's by cables attached to the bottom flange of rafters on rafter supported roofs, but was curious how to apply the equation (g) if suspending the IFR directly to the roof plate of an umbrella roof.
Note 1 in the appendix indicates to add the IFR loads as point loads, since the loads from the IFR are concentrated on the fixed roof at the point where the IFR suspension cables connect to the fixed roof.
I don't know how to apply this equation since the loads on the fixed roof are uniform loads applied to the entire roof surface (pounds per square foot) and the IFR loads are point loads (pounds). I have inconsistent units. Advice?
Also, the variable (T) for equation 5.10.6.1 still indicates that it should be the larger of Appendix R equations (e)(1) and (e)(2). It was not expanded to read "or greater of (g)(1) or (g)(2) if applicable", which makes me wonder if equation (g) is intended to be applied to umbrella roofs.
Typically we suspend our IFR's by cables attached to the bottom flange of rafters on rafter supported roofs, but was curious how to apply the equation (g) if suspending the IFR directly to the roof plate of an umbrella roof.





RE: API-650, Appendix R, Equation (g)
RE: API-650, Appendix R, Equation (g)
RE: API-650, Appendix R, Equation (g)
IF you connect your IFR cables to the bottom flange of your fixed roof rafters, how do you adjust from high to low leg setting? Just curious.
I agree with the method IFRs describes. In fact, I typically obtain the actual proposed layout from the IFR manufacturer to determine where (worst case) the point loads will intersect the rafters. From there it's simply a beam analysis problem.
By the way, the required loading combinations are very conservative and when coupled with often necessary assumptions regarding existing roof structure material strength calculated bending stresses may push the allowable limit.