collector elements in lateral system

[structuralnerd]

I have a steel framed building using moment and braced frames as the lateral system. Wind is controlling the lateral design as the building is in Seismic Category A. Some of my braced frames and moment frames are located in the center of the building. Does this mean I need to provide beams on either sides of the lateral frames to act as collector elements, or is the metal deck enough of a diaphragm to act as a collector? If I do need to provide beams, do they need to be along the entire length of the building, or just immediately adjacent to the lateral frame? Also, do they need to have tension controlled connections to prevent slipping and "banging bolts?" Any help would be much appreciated. Thank you.

 

[jike]

The metal deck needs to transfer its forces to collector beams that then in turn transfer its axial load to the braced frame or moment frame. The question of how many beams need to be collectors is determined by how much force needs to be collected. Can you provide enough connections without overstressing your diaphragm?

For metal deck, I prefer to use the entire beam line to collect the bracing force. Keep in mind that the collector force is coming in at the top flange of the beam and will create an additional moment in the beam plus you will have the axial load plus to the gravity moments. Make sure you look at the pass thru (axial) forces at the ends of the beams. You will probably need heavier clip angles, shear tabs, etc.

For concrete deck, you may be able to collect the forces in just a few beams by adding headed studs.