Special Masonry Moment Frame

[BoydZander]

I'm designing a stand alone masonry elevator hoist way. Code is IBC 2003 which defers to ASCE 7-02 for Seismic Design. Seismic Design Category = C. Due to windows on the back side and doors on the entrance side, in one direction the shaft functions as a moment frame. ASCE 7-02 classifies the seismic-force-resisting system as Special Masonry Moment Frame.

I have not yet been able to find a specific definition of this system or the requirements for design of the Special Masonry Moment Frame in ACI 530-02, IBC 2003 nor ASCE 7-02. I'm hoping someone might be familiar with thsi structural system and can point me to the requirements for it's design.

If anyone can offer any direction in regards to design requirements for Special Masonry Moment Frames and what governing code documents would provide this, I'd be most appreciateive if you could share on the topic.

 

[sundale]

A Special Masonry Moment Frame sounds like putting lipstick on a pig. Is there really such a thing? Section 1.13 of ACI 530-02 and IBC 2106 make no mention of any such system and there is probably a good reason for this...

If there is not enough wall left to justify the wall piers acting like shear walls, then I would consider simply using a steel moment frame (ordinary, intermediate, or special) to address your lateral isssues.

 

[BoydZander]

Sundale, yes, there is such and seismic force-resisting-system and despite other simpler solutions, sometimes the owner just insists on lipstick on his pig.

IBC 2000, section 2108.9.6 provides detailed requirements for such a system. The 97 and 2000 editions of the NEHRP Provisions also provide requirements for the design of such a system. In the code cycle that inlcuded the IBC 2000, this was a system that could be used and designed. With the new code cycle that inlcuded INC 2003/ASCE 7-02/ ACI 530-02, something happened where the system is allowed to be used per ASCE 7-02 table 9.5.2.2 under moment resisting frames. Despite it being allowed, one cannot find any design requirements for it because it appears to me that IBC removed the design requirements in revision effort that prodiced IBC 2003, assuming it would be located elsewhere and neither ASCE nor ACI inlcuded it in their documents.

So, I guess I have to tell the owner that code allows the wall (lipstick) he wishes but sorry, I cannot design your wall because I have no requirements for it's design.

Thanks for the input.