7 stories mid rise

[mronlinetutor]

I have a preliminary design of a 7 stories, 14' a storey, mid-rise 200'x200'. The building is braced on four sides so that the building is a non-sway. The building is a moment steel frame. The building is assumed to seat on 2' dia piles 100' in a 40'x40' grid leading to bedrock. Since earthquake attacks at the mass center of the building and since the building is square, there is little eccentricity and the building won't rotate.

One beam on the left top side on the roof is missing for the purpose of generating a failure mode and to see how the building behaves under failure. The members are not final yet. I have obtained three modes of natural frequencies of vibrations, namely mode 2, mode 9 and mode 18.

I find that the building won't rotate but the interior beams act as springs sloshing inside the building. The girders are 40' apart and the beams are 10' apart. My solution is adding k-braced members at the corners of the girder and beams. And you cross I-beams as columns. At the middle of the k-braced members are vicious dampers hoping to damp out the natural vibrations.

Attached is the mid-gen 2013 results. Enjoy.

p.s. Remember to turn on the repeat button on your viewer.



disclaimer: all calculations and comments must be checked by senior engineers before they are taken to be acceptable.

 

[JAE]

So what is the question?

 

[mronlinetutor]

One question is the frame is braced. Does the bracing needs to be prestressed and does it have to be designed as a shear wall? Is the shape and orientation of the bracing okay? etc. Thank you.

disclaimer: all calculations and comments must be checked by senior engineers before they are taken to be acceptable.