UBC load combinations 2

[dwduqu]

I'm using Enercal for a cantilevered retaining wall system and they have a 1.7H factor (it will multiply the force by 1.7) embeded in the design program - for where they suggest earthquake forces from the soil are entered for the design of the stem of the wall.

My question is either to use that 1.7H for the earthquake forces of the soil to the retaining wall stem or 1.1E which could be interperted as = 1.1(1.6H)= 1.76 as outlined in the 97 UBC.

Also, do any of you use the smilutaneous effects of the later pressures caused by the soil and active pressures as outlined in NAVFAC? Thanks!

 

[jen4950]

An obvious first step is to contact the Geotech.

 

[JStephen]

I would think 1.7H would be the normal non-seismic loading on the wall, and the 1.1E would be the additional forces due to seismic. The load factors have changed some; check the standards to see which ones are correct for your application. (old ones: 1.7, 1.4 factors, new ones, 1.6, 1.2 factors, for example.)

 

[dwduqu]

Hi and thanks for the replies and input. My question stems from the fact that in the soils report the geotech specified a 18H^2 force to act simultaneously with the active pressure. Since they do not do concrete engineering, they don't have a clue about the factors we use for these things (most don't). I've checked the UBC (both current and old) and it doesn't say exactly how to combine these. Part of the problem arises out of the EQ forces in the code (if the equations are used) are strength level while the 18H is not (EQ/1.4). If you know of any other sources I could ck please let me know ... and thanks again!