PRECAST BEARING building (15 X 60) m

[h-badawy]

DEAR EXPERTS

I'm designing a precast concrete building consisting of hollow core slab rested on four precast bearing wall and foundation is strip footing inverted tee , the thing is that building is very long(60m) beside the width(15m) and i modeled roof as a one meter width frame elements released moment (M2 and M3) from two sides and the precast wall is hinged from the bottom, so i feel the building is unstable against lateral forces (wind and seismic ) specially if the force acts perpendicular on the long direction because the distance between the two short side wall is very long , can you give me your advice if the structural system can practically work like this or difficult ??. (check attachment images for the models )

Thank you

 

[KootK]

Your roof diaphragm aspect ratio is four which is getting high but should still be doable in my opinion. Just pay some attention to the strength and stiffness of the precast roof diaphragm, particular since it's likely untopped. PCI's hollow core manual has information on this topic as does NEHRP's new design guide for precast diaphragms in seismic regions.

If an interior shear wall or brace frame in the middle works with the building programming, that's probably a better engineering solution and would likely be less work on your end.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[h-badawy]

I did the top level of the building in the model rigid diaphragm to transfer the lateral loads , and This building is chiller plant building and mechanical engineer need all area free without any interior wall , by the way the superstructure is pre-engineering , vendor will make the design and i will design the foundation only because of this am trying to make a model to get the reactions , the first estimation sections have been received are :
Hollow core slab 400 mm
Top slab 50mm
Precast concrete wall 360mm

Thank you

 

[TehMightyEngineer]

I agree with KootK; at 4:1 aspect ratio this should be doable with standard precast diaphragm and shearwall design and detailing.

Perhaps a cost-effective alternative solution would be a precast moment frame in the interior to cut your diaphragm aspect ratio in half. Could be expensive but it would reduce your diaphragm deflections significantly and possibly make many other aspects of the design easier. The moment frame would have a large tributary area though so it's likely going to be a fairly large frame.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[h-badawy]

Adding intermediate moment resisting frame or precast wall is not acceptable in this building because they need clear height and space due to mechanical equipments , so because of this the wall thickness is very thick (360mm).

Thank you