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Mono strand system
Flat tendon system
Multi strand system
External Prestessing



 


PBL Post tensioning systems for multi strand round duct type M.

The systems are commonly used in bridge construction as well as other civil Engineering structures such as Silo, Water tank etc. The systems are normally adopted for bonded tendons. The tendons consist of a bundle of strand with a nominal diameter of 0.5" (12.7 mm.) or 0.6" (15.2 mm.). The number of strands per tendon can be from 4 strands up to 31 strands of diameter 0.5" or 22 strands of diameter 0.6". The strands in the tendons are contained in one round duct which is made of corrugated galvanized or non-galvanized metal.

The strands are individually gripped in one anchor head unit and transmits their prestressing force by means of anchor plate casting unit type M. For each anchor size a special spiral reinforcement is provided at the anchor plate casting to give adequate splitting reinforcement for burstling stresses developed at the anchorage zone. The strands in tendon are stressed simultaneously by means of a multi strand stressing jack from capacity 1,100 KN up to 5,000 KN. In case of small size tendon unit such as type M405 the strands can also be stressed individually by means of mono jack.

To ensure corrosion protection and to give adequate bond strength, the tendons are filled with suitable cement grout mix after complete stressing of the strands.

Anchorage components

1. Wedges
2. Anchor head type M
3. Anchor plate casting type M
4. Grout vent
5. Corrugated metal round duct
6. Anchorage spiral reinforcement

Stressing anchorage data

Number of strands dia. 0.5(12.7mm) 4 7 12 19 31
Tendon Type 405 705 1205 1905 3105
Ultimate tensile force per tendon, kN 747 1302 2232 3534 5766
Stressing force at 0.8 u.t.s.,kN 595 1042 1786 2827 4613
Duct ID, mm 45 55 70 85 105
Jack Type V16 M110 M200 M300 M500

Number of strands dia. 0.6(15.2mm) 4 7 12 19 22
Tendon Type 406 706 1206 1906 2206
Ultimate tensile force per tendon, kN 1116 1953 3348 5301 6138
Stressing force at 0.8 u.t.s., kN 893 1562 2678 4241 4910
Duct ID, mm 50 65 80 100 110
Jack Type M110 M200 M300 M500 M500


The same anchorage can be used as dead end anchorage in which case the strands are gripped by means of wedges and are secured by springs and covered with cap fastened against anchor plate casting to prevent intrusion of cement slurry into the anchorage.

In case of prestressing continuity is required, the tendons are coupled by means of anchorage coupling connected to the stressed anchorage at the stressing joint. The anchorage couplings are available for each type of anchor size.

Anchorage coupling

  Strand Dia. 0.5" Strand Dia. 0.6"
Number Of Strands 7 12 19 31 4 7 12 19 22
Coupling Type 705 1205 1905 3105 406 706 1206 1906 2206
Length h, mm. 420 565 655 775 420 565 655 775 815
Diameter d, mm. 156 206 247 307 156 206 247 307 337

Multi strand stressing jack

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PBL GROUP LTD. PBL Group Building 8/11 Soi Vipavadi 44 Vipavadi Rangsit Road, Jatujak, Bangkok 10900
Tel. 66(0)2562-0765-9, 66(0)2941-1692-3 Fax. 66(0)2562-0764 PBLGROUP@PBL-Thailand.com