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Subsection 12.14.3.2.1, equation 12.14-9 specifies that Emh = 2.5*Qe. My question is when to use the 2.5 factor and when not to. The Code is unclear. I am designing anchorage forces for a vertical rigid steel storage tank and I use equation 15.4-5 to calculate the lateral seismic force, V...

I am a structural engineer and I have a question: I have a 24" diameter steel pipeline under about 40 feet of hydraulic head with occasional changes in direction of 45 degrees each. The pipes are welded together using groove welds. Do I need to account for thrust forces at the bends even...

We have been tasked to design full height concrete abutments on spread footings subjected to scour. The bridge structure will be an ACROW steel bridge similar to a Bailey bridge. The single span is 110 feet from CL bearing to CL bearing with HL-93 loading. My question concerns scour from...

Thanks for your great post STrctPono. These trusses are only 3'-4" apart and they are HSS 4x4s. Since they are relatively close, I will use your recommendation for wind on the leeward truss.

For a pedestrian bridge does the wind force calculated get applied to BOTH trusses or only the windward truss?

After determining the depth to fixity for concrete drilled shafts based on ADOT (Arizona DOT) Geotechnical Design Policy DS-3, how does one determine the tip elevation beyond the fixity depth? Is there a good rule of thumb (assuming that even exists) based on the shaft diameter?

After determining the depth to fixity for a concrete drilled shaft, what is the rule of thumb (if such a thing exists) for the increase in depth beyond fixity to the tip elevation?

RWW0002 I could amend OME Engineering to OLD MAN EMERITUS ENGINEERING.

All shafts...of all the bridges I have designed here in Tucson, each and every shaft has cross sonic logging and gamma-gamma required testing. However, in the local design community there is continued heated discussion about where the testing tubes (PVC) are to be located. I prefer that they...

Since I am older in my 70s, my name would be OME Engineering, LLC. "Old Man Engineering".

There are some nice tables with different aspect ratios in "Design of Concrete Structures" 12th Edition by Arthur Nilson, pages 408-411. The tables give you coefficents to calculate the moments in either direction.

Thanks so much for that clarification.

I am tasked with designing a tank to hold acid (sg = 1.84) and one of the design criteria I have from the owner says: "Tank will be rated for 6" water pressure and -.4 oz vacuum." Can anyone shed some light on what this means? I am a structural engineer, not a mechanical engineer. The tank...

I always design the walls using standard methods in accordance with ACI 318. First I design the walls assuming a cantilevered condition with the outside soil causing tension on the outside face. I design the footing assuming a cantilevered condition but sliding may be resisted by the basement...

Hello: We have a bridge here in Tucson that might be scheduled for demolition due to its age and inadequate inventory and operating ratings. The bridge is a 6 span, non composite structure: total length = 363 feet: out to out width = 64 feet. Superstructure is composed of 4 feet wide...

Thanks HotRod 10 My trench is only 12 feet long so the most I can get on the trench is 3 wheel loads. As the wheel load is distributed downward, are the pressures additive at the bottom once the pressure triangles intersect? Is it appropriate to use the 1.33 dynamic load allowance for the...

I am designing a narrow concrete trench with proprietary traffic rated grating which spans between the walls. The wall height of the trench is in the order of 5 feet and the wall thickness is tentatively 6 inches. When the wheel load of 16 kips + impact is directly over the wall, how does this...

Yes HotRod: I thought of that. This old bridge uses 250 ksi tendons f'c = 5 ksi for the girders and grade 40 for the mild steel. I will use the oldest AASHTO we have. Thanks again for your timely and thoughtful responses. The existing stirrup layout could be the deal breaker in trying to...

HotRod10 and wiktor: Thanks so much for your responses. The prestressing tendons are straight and are all within the bottom flange of the girder. There are 26 straight 3/8" diameter strands (0.08 in^2/strand). The shear reinforcing is located within the centerlines of the vertical stems of...

Gentlemen: I am analyzing an old 3 span non-continuous, pre-cast box girder bridge, with simple spans of 49.25 feet each. The superstructure is 27 feet wide and consists of 9 voided box sections 3 feet wide and 27" deep. Currently the driving surface is only about 2" of asphalt. Our scope of...