Naggud
Structural
- Jan 31, 2013
- 42
Hi guys,
I am a recently graduate, I'm looking at a building (prelim. seismic assessment).
We are not assessing the rigidity of the diaphragms. In general we are assuming a timber floor/roof is a perfectly flexibly diaphragm and a concrete diaphragm is assumed to be completely rigid (relatively short spans - commercial buildings).
The seismic load is distributed based on trib area for a flexible diaphragm and based on the relative stiffness of the vertical elements for a rigid diaphragm.
If I have a simple timber building, square on plan. If I have 3 vertical support systems in one direction - on the west wall I have post and beam construction (assumed no lateral stiffness), a timber stud wall in the middle of the building the length of the building north south and a partial timber stud wall on the east wall.
In my analysis of this I originally attributed the lateral loads based on tributary area. i.e. 1/3 to the post and beam, 2/3 to the central wall and 1/3 to the shorter stud wall.
On this basis the post and beam wall would fail (negligible later stiffness), lets assume the middle wall is adequate and the shorter east wall fails.
I have been speaking to some of our more senior guys about this in the past while. They have been saying to me that the post and beam wall will not fail - that the load would be transferred back into larger middle wall.
When I find that the short east wall fails based on the tributary load he says to leave that wall as having failed (I think this is inconsistent).
I would appreciate your views. To emphasis, this is a very preliminary assessment, we are not going into very much detail, I just find the approach inconsistent.
Thank you.
I am a recently graduate, I'm looking at a building (prelim. seismic assessment).
We are not assessing the rigidity of the diaphragms. In general we are assuming a timber floor/roof is a perfectly flexibly diaphragm and a concrete diaphragm is assumed to be completely rigid (relatively short spans - commercial buildings).
The seismic load is distributed based on trib area for a flexible diaphragm and based on the relative stiffness of the vertical elements for a rigid diaphragm.
If I have a simple timber building, square on plan. If I have 3 vertical support systems in one direction - on the west wall I have post and beam construction (assumed no lateral stiffness), a timber stud wall in the middle of the building the length of the building north south and a partial timber stud wall on the east wall.
In my analysis of this I originally attributed the lateral loads based on tributary area. i.e. 1/3 to the post and beam, 2/3 to the central wall and 1/3 to the shorter stud wall.
On this basis the post and beam wall would fail (negligible later stiffness), lets assume the middle wall is adequate and the shorter east wall fails.
I have been speaking to some of our more senior guys about this in the past while. They have been saying to me that the post and beam wall will not fail - that the load would be transferred back into larger middle wall.
When I find that the short east wall fails based on the tributary load he says to leave that wall as having failed (I think this is inconsistent).
I would appreciate your views. To emphasis, this is a very preliminary assessment, we are not going into very much detail, I just find the approach inconsistent.
Thank you.
