NCEES Structural I Sample Questions

[bootlegend]

Has anyone worked problem 135? IT is basically a 200'x100' building and asks for the seismic chord force in the roof diaphragm. You are given Cs and the roof and wall DL's so it is easy to come up with seismic force. I would have thought you would distribute the force along the length of the building and taken the moment as (wL^2)/8 assuming pinned ends. This appears to be the correct solution but the answer is formulated as Chord force = (PL)/(chord depth*8) using the actual numbers. I can't tell if the author used PL/8 for a fixed ends with point load or wL^2/8 with pinned ends and distributed load. The way the solution is written it looks like fixed ends, but the answer is the same either way in this example.

 

[BLMedcalf]

Has anyone worked problem 135? IT is basically a 200'x100' building and asks for the seismic chord force in the roof diaphragm. You are given Cs and the roof and wall DL's so it is easy to come up with seismic force. I would have thought you would distribute the force along the length of the building and taken the moment as (wL^2)/8 assuming pinned ends. This appears to be the correct solution but the answer is formulated as Chord force = (PL)/(chord depth*8) using the actual numbers. I can't tell if the author used PL/8 for a fixed ends with point load or wL^2/8 with pinned ends and distributed load. The way the solution is written it looks like fixed ends, but the answer is the same either way in this example.

It is a distributed load simply supported equation. Some people use the PL/8d instead of WL^2/8d. It is the same thing, just substituting P instead of WL in the first equation. I hope I understood your question.

 

[bootlegend]

Alright, thanks. I assumed it was a simple span, but wanted to make sure there wasn't something with the seismic procedures that required a point load analysis.