We currently use Engineering News with a FS of 3 for temporary work bridge installation in remote areas with little to no geotechnical information. I noticed then FWHA has adopted the modified Gates formula. Could any give advice on risks ? as I realize the Engineering News formula has it's own draw backs.

Do a google search - there are some good downloads out there that discuss the pros and cons of the various pile driving formulas (and I am not going into the fact that many don't like them!).  Olson and Flaate back in the 60s did a number of papers that studied the various formulas in detail.  Gates and the Danish seem the best (from memory):

http://www.google.co.id/search?num=100&hl=en&q=Flaate+dynamic+formula+piles&btnG=Search&meta=

 

Gates is promulgated by AASHTO/FHWA as the "best" method. Produces results similar to wave equation method.

Jeff
 

FHWA has adopted Gates as its preferred formula, but I generally use it only as a starting point, to proceed into the wave equation from there.  That software (it's old, I know) is at

http://www.vulcanhammer.info/drivability/weap-spile.php

http://www.pz27.net

The sites are quite remote 1000's of KM away from nearest PDA. Gates seems to provide a reasonable alternative to ENR. I've noted that the capacity requirements appear to less stringent or volatile with Gates in most cases.

When I compared the factored equations ENR @ FS=3, ENR @ FS=6, and Gates @ FS=3.5, the results are all over the map. The gates formula seems to be more stable.
The ENR @ FS=3 and Gates seem to be correlate up to around 300 KN at lower energy ratings, and up to 600 KN and higher values. Can anyone give recommendation on when to not apply equations, i.e. (less the 400-500 KN) See attachments.
 

• http://files.engineering.com/getfile.aspx?folder=f89de43c-cfdf-49fe-9ff6-b7

lat post should of read, (i.e. only at ratings less the 400-500 KN)