mikesg
Structural
- May 26, 2006
- 49
Dear colleagues,
I am analysing a one-storey structure, that consists of precast RC columns, fixed in both directions at base, supporting precast prestressed beams spanning in one direction. Beams-column connections are pinned. The roof is made of T panels, and there is space between panels so that light can enter throug polycarbonate elements(visual clue can be seen on Another option for the roof is to use 2T panels with openings in them.
In the case of T panels due to lighting the diaphragm is is non-existent. There is an option to choose 2T panels with openings in them however, but I would like to avoid cast in-situ concrete above the panels. Horizontal bracing is not an option with both types of panels.
I am trying to figure out the behaviour factor for seismic analysis, and here are my thoughts. I would highly appreciate your comments and recommendations on them.
In my opinion if there are steel plate welded connections (subject of calculation) at several places along the joint between 2T panels, and welded connection between the panels and the beams, I can consider this roof as a rigid diaphragm. And from what I read in our code I can accept q = 2.8. As I would if there was monolithic in-situ reinforced concrete 40-50mm(~2") thick cast on the panels.
In the case of T-beams with lighting however I think I cannot rely in any way on the roof as a diaphragm, even a flexible one, and I should take q=1.5 without any option for improving that.
The area is with high seismic hazard (0.27~0.30g). The columns are about 9m(~30ft) tall and the spacing between them is 18m in one drection/beams/ and 20m in the other/panels/ (59ft and 65ft respectively).
I appreciate highly any comments and suggestions.
Mike
I am analysing a one-storey structure, that consists of precast RC columns, fixed in both directions at base, supporting precast prestressed beams spanning in one direction. Beams-column connections are pinned. The roof is made of T panels, and there is space between panels so that light can enter throug polycarbonate elements(visual clue can be seen on Another option for the roof is to use 2T panels with openings in them.
In the case of T panels due to lighting the diaphragm is is non-existent. There is an option to choose 2T panels with openings in them however, but I would like to avoid cast in-situ concrete above the panels. Horizontal bracing is not an option with both types of panels.
I am trying to figure out the behaviour factor for seismic analysis, and here are my thoughts. I would highly appreciate your comments and recommendations on them.
In my opinion if there are steel plate welded connections (subject of calculation) at several places along the joint between 2T panels, and welded connection between the panels and the beams, I can consider this roof as a rigid diaphragm. And from what I read in our code I can accept q = 2.8. As I would if there was monolithic in-situ reinforced concrete 40-50mm(~2") thick cast on the panels.
In the case of T-beams with lighting however I think I cannot rely in any way on the roof as a diaphragm, even a flexible one, and I should take q=1.5 without any option for improving that.
The area is with high seismic hazard (0.27~0.30g). The columns are about 9m(~30ft) tall and the spacing between them is 18m in one drection/beams/ and 20m in the other/panels/ (59ft and 65ft respectively).
I appreciate highly any comments and suggestions.
Mike
