(4/3) Allowable Increase in Masonry Walls for Wind

[bflood]

I always used the (4/3) allowable increase for bending on a masonry wall with wind load. I am sitting for the SE 1 this Friday and the review course I sat in on via the web through ASCE suggested not to take the (4/3) allowable increase. I have attached a sample problem to better clarify myself. If anyone can help clear this up for me I would appreciate it. I am using Working Stress to solve the problems.

 

[jike]

Most of the states follow the IBC which references ASCE 7. Both the IBC and ASCE 7 do not allow the 1/3 increase anymore. You must follow the various load combinations given.

 

[csd72]

There was an article about this in Modern Steel construction about 2 or 3 years back. It may be worthwhile reading.

 

[Lion06]

I think ASCE7-05 allows the 1/3 increase, but you have to use the Alternate Load Combinations, not the basic. I would stick with the basic combinations and NOT use the increase. ACI 530 allows the increase, but that doesn't supersede ASCE 7, and IBC.

 

[ash060]

It all depends, when I took the test the problems stated the code(s) they wanted you to use.

For example, it might be a steel beam design and at the top it would say "Using the AISC 13th Edition Manual and ASCE 7-05 answer the following question"

So use the codes it tells you to use. A masonry question may only reference the Masonry code in that case I would probably use the 1/3 increase in necessary.

If the question also references IBC 2006 I would not use the 1/3 increase.

 

[abusementpark]

Does it only allow you to increase the allowable masonry stress? What about the steel?

 

[sandman21]

Masonry and Wood. No increase in Steel. The CBC also allows the increase.

 

[abusementpark]

No, I mean does it allow to increase the allowable stress on the rebar steel in the masonry?

 

[JLNJ]

yes, if you are allowing the increase for the masonry then allow it for the rebar.

 

[DaveAtkins]

StructuralEIT is correct. This leaves you in a bit of a "pickle". The question does not say if the Alternate Load Combinations were used to develop the wind load applied to the wall.

When you take the SE1 or SE2, make sure you write down your assumptions on any problem of this type. You should write down, "Assume wind load is not based on Alternate Load Combinations. Therefore 1/3 masonry stress increase is not permitted." Then solve the problem.

DaveAtkins