1 Introduction
2 Transfer Lengths in Provisions and Previous Studies
Provisions | Abbreviation | Predictive equation | Remarks |
---|---|---|---|
AASHTO LRFD (AASHTO 2017) | AASHTO |
\(60d_{b}\)
| \(d_{b}\) : strand diameter (mm) |
KDCHB2 (KRTA 2015) | KDCHB2 | ||
KDCHB1 (KRTA 2010) | KDCHB1 |
\(50d_{b}\)
| \(d_{b}\) : strand diameter (mm) |
ACI 318-19 (ACI Committee 318 2019) | ACI |
\(\frac{{f_{se} d_{b} }}{21}\)
| \(d_{b}\) : strand diameter (mm) \(f_{se}\) : effective prestress of strand (MPa) |
PCI (PCI 2017) | PCI | ||
KSCDC (KCI 2012) | KSCDC | ||
BS 8110 (BSI 1997) | BS |
\(\frac{{K_{t} \varphi }}{{\sqrt {f_{ci} } }}\)
| \(K_{t}\): coefficient for tendon surface condition \(\varphi\): tendon diameter (mm) \(f_{ci}\) : concrete strength at transfer (MPa) |
Eurocode 2 (CEN 2004) | EC |
\(\frac{{\alpha_{1} \alpha_{2} \phi \sigma_{pm0} }}{{f_{bpt} }}\)
| \(\alpha_{1}\): coefficient for speed of transfer \(\alpha_{2}\): coefficient for tendon surface condition \(\phi\): tendon diameter (mm) \(\sigma_{pm0}\): tendon stress upon transfer (MPa) \(f_{bpt}\): bond stress (MPa) |
3 Fabrication of Specimens and Measurement Plan
3.1 Test Variables
Series | Specimens | |||
---|---|---|---|---|
M | C35 | N | D12 | C35-D12-N-M-1 C35-D12-N-M-2 |
D15 | C35-D15-N-M-1a C35-D15-N-M-2a | |||
H | D15 | C35-D15-H-M-1a C35-D15-H-M-2a | ||
C50 | N | D12 | C50-D12-N-M-1 C50-D12-N-M-2 | |
D15 | C50-D15-N-M-1b C50-D15-N-M-2b | |||
H | D15 | C50-D15-H-M-1b C50-D15-H-M-2b | ||
C80 | N | D12 | C80-D12-N-M-1 C80-D12-N-M-2 | |
D15 | C80-D15-N-M-1a C80-D15-N-M-2a | |||
H | D15 | C80-D15-H-M-1a C80-D15-H-M-2a | ||
T50 | C50 | N | D15 | C50-D15-N-T50-1 C50-D15-N-T50-2 |
H | C50-D15-H-T50-1 C50-D15-H-T50-2 | |||
T65 | C50 | N | D15 | C50-D15-N-T65-1 C50-D15-N-T65-2 |
H | C50-D15-H-T65-1 C50-D15-H-T65-2 |
\(f_{c}^{'}\) (MPa)a | Gmax (mm)b | Air content (%) | Slump (mm) | W/B (%) | S/a (%)d | Unit weight (kg/m3) | AD (B%)k | ||||
---|---|---|---|---|---|---|---|---|---|---|---|
We | Bf | FAi | CAj | ||||||||
Cg | SFh | ||||||||||
35 | 25 | 3 | 120 | 37.5 | 45 | 157 | 440 | – | 786 | 959 | 3.96 |
50 | 25 | 6 | 120 | 29.5 | 43.5 | 166 | 563 | – | 707 | 936 | 5.63 |
80 | 25 | 3 | 500c | 27.2 | 39.9 | 179 | 612 | 68 | 587 | 881 | 8.84 |
3.2 Test Procedure and Measurement Plan
4 Experimental Results
4.1 Estimation of Transfer Lengths
4.2 Results of Transfer Lengths
No. | Specimen ID | Transfer length (mm) | |||||
---|---|---|---|---|---|---|---|
Concrete gauge (CG) | Smart Strand (SM) | Strand gauge (SG) | |||||
Cut end | Dead end | Cut end | Dead end | Cut end | Dead end | ||
1 | C35-D15-N-M-1 | 729 | 623 | 736 | – | 730 | 608 |
2 | C35-D15-N-M-2 | 838 | 729 | 950 | – | 880 | 692 |
3 | C35-D15-H-M-1 | 752 | 615 | 734 | – | 712 | 701 |
4 | C35-D15-H-M-2 | – | – | – | – | – | – |
5 | C35-D12-N-M-1 | 416 | 405 | – | – | 523 | 511 |
6 | C35-D12-N-M-2 | 519 | 467 | – | – | 716 | 539 |
7 | C50-D15-N-M-1 | 1032 | 1011 | 940 | 914 | 874 | 645 |
8 | C50-D15-N-M-2 | 1187 | 826 | 1136 | 819 | 889 | 711 |
9 | C50-D15-H-M-1 | 986 | 919 | 1011 | 924 | 1058 | 545 |
10 | C50-D15-H-M-2 | 1287 | 936 | 1258 | 977 | 800 | 732 |
11 | C50-D12-N-M-1 | 852 | 696 | – | – | 885 | 511 |
12 | C50-D12-N-M-2 | 1083 | 640 | – | – | 1117 | 719 |
13 | C80-D15-N-M-1 | 499 | 459 | – | – | 532 | 521 |
14 | C80-D15-N-M-2 | 513 | 349 | – | – | 505 | 332 |
15 | C80-D15-H-M-1 | 691 | 403 | – | – | 515 | 473 |
16 | C80-D15-H-M-2 | 945 | 369 | – | – | 657 | 327 |
17 | C80-D12-N-M-1 | 334 | 248 | – | – | 332 | 330 |
18 | C80-D12-N-M-2 | 361 | 265 | – | – | 332 | 332 |
19 | C50-D15-N-T50-1 | 841 | 612 | – | – | 857 | 507 |
20 | C50-D15-N-T50-2 | 849 | 791 | – | – | 685 | 501 |
21 | C50-D15-N-T65-1 | 813 | 630 | – | – | 917 | 788 |
22 | C50-D15-N-T65-2 | 1207 | 846 | – | – | 905 | 516 |
23 | C50-D15-H-T50-1 | 1106 | 793 | – | – | 913 | 876 |
24 | C50-D15-H-T50-2 | 1315 | 926 | – | – | 853 | 735 |
25 | C50-D15-H-T65-1 | 1264 | 768 | – | – | 1022 | 596 |
26 | C50-D15-H-T65-2 | 996 | 779 | – | – | 1075 | 735 |