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Thanks. That explanation makes sense. Excel can be used to do the curve fit using center of mass ordinates for the primary mode shape in each building direction.

I have a tall (300ft) and somewhat slender building and want to get input on drift criteria. The building is in a high seismic area as well. I can easily satisfy the l/400 drift for wind at the center of mass, but for the torsion wind cases the corners of my building exceed the l/400 suggested...

I am studying the methods documented in the commentary and there is a method of determing the displacment and accelerations over the height of a structure. This is under C6.5.8. There is a term "mode exponenet" that is not defined and is needed. Can any one enlighten me on what this term is...

I am investigating the use of ASCE 7 Chapter 19, which seems like a way of approximating Soil Structure Interaction (SSI) without including it in the Building Model. If this chapter is implimented it could reduce the lateral loads for design and drift. I have used modal analysis procedures for...

Thanks. I'll dig into those agencies to see what i can find. I had another thought from a coworker that the UBC had very early versions that may have some basic design info for materials.

I am working on a seismic retrofit of 1930s-1940s era concrete buildings for the Dept of Veterans Affairs (VA). We have the original construction drawings but they only refer to Type C and Type B concrete. We are doing material testing but ASCE 41 dictates different amount of testing required...

I am working on a seismic retrofit of 1930s-1940s era concrete buildings for the Dept of Veterans Affairs (VA). We have the original construction drawings but they only refer to Type C and Type B concrete. We are doing material testing but ASCE 41 dictates different amount of testing required...

I am awaiting concrete test results, but until then ASCE 41 gives ranges for what can be assumed. Thats where 2500psi came from

I calced the shear strength from ACI (phi=1.0)and for the 2in slab a capacity of 7.24k/ft was found. ASCE41 m factor used was 1.5 for Imediate occupancy. The expected f'c is 2500psi the expected fy =49.5ksi and there are only 1/4" dia bars at 12" o.c. For example at a 32 ft long perimeter...

I am analyzing an existing building with concrete joist floor system. The joists are 5in wide by 8in below the slab. The slab is only 2 or 2.5 in thick. The joist spacing is 20in and the spans are 10-12ft. I am in a high seismic area and the diaphragm strength is being evaluated. The slab alone...

I am trying to get access to old FEMA documents, mainly the 1994 provisions which i think are 222 and 223. I tried getting them through the FEMA distributor but they didn't have them in the warehouse. Is there a way to get these older documents in either electronic or hard copy form? Thanks in...

Does anyone have experience with modeling a stepped basement wall for a building foundation? I am having trouble with applying a continuous footing at different levels along a wall that steps.

Dik, I found my CD that came with the blue steel manual. The program that is on the CD was not what i was looking for. It requires you to actually type in the shape your interested in rather than using drop downs that have all the shapes. It may be different with the new black manual. would...

Thanks for the help. That was what i thought but couldn't find our copy of the errata. Now i know they are online, which makes sense.

I am trying to calculate the gust effect factor for a structure that falls into the flexible category according to the code. There is bunch of equations to work through the calc but i get to calculating the R (eqn 6-10) and for RB the equation for n = 4.6*n1*E*B/Vz. The E in the equation is not...

Thanks for the reminder. I will try to locate my CD.

I am trying to find a program that AISC used to have for download on there website. It was an actual program, not the excell files that are available now, that let you select the steel manual version and then the shape type and it would show all the properties for the shape. It even had the...

i did a comparison of the two programs a while back and found that if settings are adjusted properly the two programs give basically the same results. The main things to examine are the fixity and modeling of columns above/below your slab and what the datum is for lengths of columns above and...

From my experience meshing should be at 48in max and segments should be as square as possible. The finer the mesh the more accurate the results but greatly increases the run time. The reason for the different stress is that between mesh points the values are estimated so if your mesh is too...

Some final comments on the subject ... I spent some time studying the support conditions and after examining many possibilities, i think that using full height columns below the slab only with either pinned or fixed supports is most realistic. It results in good estimate of deflections and seems...