Grouted Tieback Anchors
Grouted Tieback Anchors
(OP)
We bid a projet for installing 25' long PZC 13 steel sheet piling with grouted hollow bar anchors 2".Bulkhead application with 12' exposed to the bay.Design Engineer plans show detail drawings as such and he noted the anchors to be 12' on center maxium with a waler.Wall design for 7000 psi per foot which we had to suppy a design for the anchors by another P.E.When we do our design the anchors have to be on 9.5' on center at a 30 degree angle 60' long with a 20' bond lenght to work.Since the bid plans noted anchors to be 12' on center maxium and we now know that they have to be on 9.5' maxium on center should the Owner be responsible for the additional anchors since we used the bid plan that was signed and sealed which noted the 12' OC notation for the anchors,stated sheet pile size and lenght, and grouted anchor to be used.The only two items not stated was the angle of the anchor and the lenght of the anchor.





RE: Grouted Tieback Anchors
RE: Grouted Tieback Anchors
RE: Grouted Tieback Anchors
What do you mean by 7000 psi per foot?
Also, did the contract documents require the anchor design to use any specific soil properties? If so, you probably will have to use them or more conservative values if more appropriate. If your PE chose the soil properties and tieback angle for his design, you need to check if he was too conservative. The tieback capacity will also be a function of the drill hole (drill bit) diameter. The bigger the diameter, the more bond area and capacity.
I am not a big fan of these hollow bar anchors. They are expensive to buy, limited in capacity compared to a solid bar or strand anchors, are not easy to corrosion protect, and it is hard to install an unbonded length over the couplings. It is also hard to use re-grout tubes with these anchors due to the couplings.
Normally, it is up to the tieback contractor to install an anchor that can do the job. The 12' maximum is most likely a function of the already designed tieback wale. Also, the anchor spacing is normally a multiple of the sheet pile double width. Therefore, the anchors are usually installed through the back flange of the sheet pile doubles when the wales are attached to the front flanges of the sheets.
RE: Grouted Tieback Anchors
Dik
RE: Grouted Tieback Anchors
The owner is not going to pay more just because the contractor (or his/her) engineer comes up with another design. If you can prove that the anchors could not, under any conditions, be installed at 12 ft c-c then maybe you could get more money.
If you, as the contractor, were responsible for designing the anchors, then you should have designed them prior to putting your bid together for the project.
RE: Grouted Tieback Anchors
RE: Grouted Tieback Anchors
RE: Grouted Tieback Anchors
I can't say that I agree with the second half of your last posting. It seems very clear to me that the contractor or anchor subcontractor is to design the anchors and use 12' as the MAXIMUM spacing. The designer doesn't seem to have designed the anchors. If he did, he would have had to give you the total anchor length, the drill hole diameter, the corrosion details, the design load, the anchor tendon type, tendon size, bearing plate size, etc. Did he give you that information? All that you said was specified is that the anchors are to be at 12' maximum and that should be based on the already designed tieback wales.
RE: Grouted Tieback Anchors
Are the plans showing 12 feet maximum approved by a local building official?
RE: Grouted Tieback Anchors
you note "The only two items not stated was the angle of the anchor and the lenght of the anchor" but the REQUIRED spacing was not specified, only the MAXIMUM spacing. Sounds like whoever put the bid together missed that important distinction.
RE: Grouted Tieback Anchors
RE: Grouted Tieback Anchors
RE: Grouted Tieback Anchors