Custom Prestressing strand coupler
Custom Prestressing strand coupler
(OP)
Hello everyone
I have designed a coupler to join 2 prestressing strands to avoid wastage ( see attachment )
1. For 9.3 mm dia strand
a. Load Capacity = 100kN ( strand A= 52mm2, fpu = 1770 N/mm2, 70% tensioning only)
b. Base thickness of plate = 15mm (limited to 15mm to maintain strand cover)
c. wall thickness = 20mm
d. Plate S355 with min yield strength = 355 N/mm2
e. Fillet weld on both sides all around with strength 390 N/mm2 (SG2)
f. From SAP2000 model, max stresses are in range of 190N/mm2
2. For 12.7 mm dia strand ( strand A= 97 mm2, fpu = 1770 N/mm2, 70% tensioning only)
a. Load Capacity = 200kN
b. Base thickness of plate = 15mm (limited to 15mm to maintain strand cover)
c. side wall thickness = 20mm and front wall where the barrel will fix = 30mm
d. Plate S355 with min yield strength = 355 N/mm2
e. Fillet weld on both sides all around with strength 390 N/mm2 (SG2)
f. From SAP2000 model, max stresses are in range of 190N/mm2
My questions are:
1. Did I choose the correct plate for this purpose? Any suggestions? which plate can perform better in welding ect
2. Which rod to choose for welding the plate?
3. Are the stresses in plate and weld are OK?
4. Will this coupler system will work or i am missing something?
I have designed a coupler to join 2 prestressing strands to avoid wastage ( see attachment )
1. For 9.3 mm dia strand
a. Load Capacity = 100kN ( strand A= 52mm2, fpu = 1770 N/mm2, 70% tensioning only)
b. Base thickness of plate = 15mm (limited to 15mm to maintain strand cover)
c. wall thickness = 20mm
d. Plate S355 with min yield strength = 355 N/mm2
e. Fillet weld on both sides all around with strength 390 N/mm2 (SG2)
f. From SAP2000 model, max stresses are in range of 190N/mm2
2. For 12.7 mm dia strand ( strand A= 97 mm2, fpu = 1770 N/mm2, 70% tensioning only)
a. Load Capacity = 200kN
b. Base thickness of plate = 15mm (limited to 15mm to maintain strand cover)
c. side wall thickness = 20mm and front wall where the barrel will fix = 30mm
d. Plate S355 with min yield strength = 355 N/mm2
e. Fillet weld on both sides all around with strength 390 N/mm2 (SG2)
f. From SAP2000 model, max stresses are in range of 190N/mm2
My questions are:
1. Did I choose the correct plate for this purpose? Any suggestions? which plate can perform better in welding ect
2. Which rod to choose for welding the plate?
3. Are the stresses in plate and weld are OK?
4. Will this coupler system will work or i am missing something?






RE: Custom Prestressing strand coupler
As an alternative, have you considered the use of a strand splice reducer, which is a multi-use strand splice chuck where one end fits 12.7 mm dia strand and the other fits 9.3mm dia strand. Also called a "double ended joint" outside the US.
The cost less than US$100 and common in the pretensioning industry.
Link
RE: Custom Prestressing strand coupler
RE: Custom Prestressing strand coupler
They are used daily, the world-over, without incident. All have a spring lock, and some use safety pegs to ensure full strand biting. They require cleaning after each use, but so does everything in such applications.
Compare that with your proposed custom coupler that is UNtested and still depends on barrel chucks to grip the strand.
RE: Custom Prestressing strand coupler
RE: Custom Prestressing strand coupler
If the production manager chooses to go with the custom splice box, you are going to have to test it, possibly to a proof load of about 2 x maximum expected applied load, and depending on what part of the world this shall be used, it may require independent laboratory and/or prototype load testing too.
Your also need to consider the maintenance of this custom splice box, and procedures to be taken by experienced personnel to check daily for wear, distortion etc.
RE: Custom Prestressing strand coupler
Its in Bahrain. Extremely humid place. Box must be galvanized. And the maintenance note I will put for him.
Thanks!
RE: Custom Prestressing strand coupler
The coupler must be designed for a load of at least 110% of the strand strength plus material factors etc.
How are the wedges held in place and set?
RE: Custom Prestressing strand coupler
I'm not trying to say your design is unsafe or not logical, by all accounts it appears to make sense. But the concept of basically reinventing something that already exists and has extensive history of safe use carries a high level of risk just seems like an unnecessary liability concern.
RE: Custom Prestressing strand coupler
RE: Custom Prestressing strand coupler
RE: Custom Prestressing strand coupler
PAUL (from Germany) are a well recognised and long-time manufacturer of pretensioning components and hardware.
With competition from SURELOCK (US manufacturer) and CCL (UK manufacturer) the prices for 12.7mm couplers are about US$80 each - just took delivery of some last week.
Engineering, reliability and safety trumps production!
RE: Custom Prestressing strand coupler
RE: Custom Prestressing strand coupler
The splice chucks (and any re-usable chuck or barrel) needs to be cleaned and maintained after each use.
Best of luck.
RE: Custom Prestressing strand coupler