Recent content by bar7h

I am looking for suggestions on the best FEA software for modeling joints, connections, custom base plates, etc. We are using RISA which does a good job on wire-frame models and handles basic plate model pretty well. But, we are often requested to make finite element models of more complex...

Thank you for your input.

The ASCE 7 defines edge and corner zones "a" as 10% of the least horizontal dimension or 0.4h, whichever is smaller... How do you all define "least horizontal dimension" when the building isn't a box, but irregular with several different wings or roof sections. I typically take the least...

Thanks for your comments. I'm not sure if my FEA program will allow the periodic application of live load as you have suggested - I'll have to look into that. Also, thank you for the technical paper references. I have some reading to do.

We have considered designing in connection points for dampers and then leaving the final decision on whether to install them until after the structure is commissioned and "tried out". The bridge is multi-span, so it lends itself nicely to this with relative displacement of the top chords at the...

I'll see if I can contact Professor Murray - although I have never been very successful getting academic folks to respond to questions like this. I agree that it would be much better to make dampers part of the original design, but I want to be sure that they are truly necessary before I incur...

I am working on the design of a long span (approx. 200') pedestrian bridge consisting of a steel box truss and concrete deck. The natural frequency of the bridge in the vertical mode is approximately 1.5 Hz, so it does not meet the AASHTO ped. bridge spec minimum requirement of 3 Hz - and there...

I am designing the anchorage of some large pylons with very large moments (approx. 65,000 k-ft unfactored). They will be anchored into large mat foundations with an annular anchor bolt pattern utilizing (34) 3.5" diameter anchor bolts on a 144" bolt circle. Checking the anchor bolt steel...

How do you determine the stiffness of the bearing and what spring constant would you use? It seems like there would be free movement due to the oversized bearing plate A.B. holes until the holes came in contact with the the anchor bolt, then there would be a fully fixed condition. I know some...

Thanks for the input. I'll give that a shot.

This bridge has a timber plank deck, so I'm using steel bracing in the horizontal plane. The bearing is a typical bearing plate on a setting plate - teflon coated at expansion end. I don't have the model in front of me now, but the opposing reactions are in the neighborhood of 33 kips. I...

Yes, I did check that, and I check the deflected model and it behaves as expected. Thinking of a beam that is fully fixed at one end and "roller" at the other, you still get quite a large moment reaction at the fixed end which seems to be what is giving me the large couple forces at the...

I am designing a single span 10'x100' Pratt Truss pedestrian bridge. I have created a 3D FE model of the bridge with the two bearings at the fixed-end modeled as "pinned" and bearings at the expansion-end free to translate longitudinally. When I analyze the model under transverse wind loads, I...

Thank you. That was very helpful.

I need some input on the appropriate 'R' value to use in concrete tilt-up design. Under the 2003 IBC we used R=5.5 for special reinforced conc. shearwalls. Under the new 2006 IBC & ASCE 7-05, Table 12.2-1 lists intermediate precast concrete shearwalls with an R=4 and special reinf. conc...