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Frontiers of Structural and Civil Engineering

Front. Struct. Civ. Eng.    2014, Vol. 8 Issue (4) : 373-387     https://doi.org/10.1007/s11709-014-0087-7
RESEARCH ARTICLE |
Shear design of high strength concrete prestressed girders
Emad L. LABIB1,Hemant B. DHONDE2,Thomas T. C. HSU3,Y. L. MO3,*()
1. Oil Field Development Engineering LLC, Houston, TX 77079, USA
2. Department of Civil Engineering, VIIT, University of Pune, Pune 411007, India
3. Department of Civil and Environmental Engineering, University of Houston, Houston, TX 77004, USA
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Abstract

Normal strength prestressed concrete I-girders are commonly used as the primary superstructure components in highway bridges. However, shear design guidelines for high strength PC girders are not available in the current structural codes. Recently, ten 7.62 m (25 feet) long girders made with high strength concrete were designed, cast, and tested at the University of Houston (UH) to study the ultimate shear strength and the shear concrete contribution (Vc) as a function of concrete strength (f\hskip -3ptc). A simple semi-empirical set of equations was developed based on the test results to predict the ultimate shear strength of prestressed concrete I-girders. The UH-developed set of equations is a function of concrete strength (f\hskip -3ptc), web area (bwd), shear span to effective depth ratio (a/d), and percentage of transverse steel (ρt). The proposed UH-Method was found to accurately predict the ultimate shear strength of PC girders with concrete strength up to 117 MPa (17000 psi) ensuring satisfactory ductility. The UH-Method was found to be not as overly conservative as the ACI-318 (2011) code provisions, and also not to overestimate the ultimate shear strength of high strength PC girders as the AASHTO LRFD (2010) code provisions. Moreover, the proposed UH-Method was found fairly accurate and not exceedingly conservative in predicting the concrete contribution to shear for concrete strength up to 117 MPa (17000 psi).

Keywords shear design      high strength concrete      prestressed girders      full-scale tests     
Corresponding Authors: Y. L. MO   
Online First Date: 12 December 2014    Issue Date: 12 January 2015
 Cite this article:   
Emad L. LABIB,Hemant B. DHONDE,Thomas T. C. HSU, et al. Shear design of high strength concrete prestressed girders[J]. Front. Struct. Civ. Eng., 2014, 8(4): 373-387.
 URL:  
http://journal.hep.com.cn/fsce/EN/10.1007/s11709-014-0087-7
http://journal.hep.com.cn/fsce/EN/Y2014/V8/I4/373
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Emad L. LABIB
Hemant B. DHONDE
Thomas T. C. HSU
Y. L. MO
Fig.1  Determination of number of stirrups for steel contribution V s in a PC girder. (a) Smeared stirrups method; (b) minimum shear resistance method
materials - kg/m3 (lb/yd3) Group A Group F Group C
cement: ASTM Type-III 218 (368) 308 (519) 415 (700)
fly ash: ASTM Type-F 89 (150) 147 (248) 119 (200)
Cementitious Content 307 (518) 455 (767) 534 (900)
fine aggregate: river bed sand 685 (1156) 685 (1156) 634 (1070)
coarse aggregate 1304 (2200)a) 1125 (1899)a) 1304 (2200)b)
coarse agg./fine agg. ratio 1.91 1.64 2.06
water 107 (180) 136 (230) 142 (240)
water/cement ratio 0.49 0.43 0.34
water/cementitious materials ratio 0.35 0.30 0.27
superplasticizerc) 5.7 (9.6) 7.6 (12.8)
retarderd) 0.6 (1) 2.4 (4)
slump: mm (in.) 165 (6.5) 216 (8.5) 267 (10.5)
average compressive strengthe): MPa (psi) 49 (7,100) 91 (13,200) 108 (15,660)
Tab.1  Concrete mix proportions used for casting PC girder specimens
Fig.2  Layout of Tx54 girders with top deck (unit: mm)
Fig.3  Full scale and scaled down cross-sections of PC girders. (a) Full scale cross-section; (b) scaled down cross-section (unit: mm)
Fig.4  Cross-section and reinforcement details for modified Tx28 girders (unit: mm)
Fig.5  Cross-section and reinforcement details for modified Tx28 girders C2 and C4 (unit: mm)
Fig.6  Positions of loading actuators and load cells for various girder specimens. (a) A1, F1, F3, C1, and C3 with a/d equals 1.77; (b) F2 and F4 with a/d equals 2.25; (c) A2, C2 and C4 with a/d equals 3.00 (unit: mm)
girder strands mild steel reinforcement (refer to Figs. 4 and 5 for more details)
Nos. dia. /mm transverse steel(?16 mm) “S”-rebar top flange flexural steel (?13 mm) bottom flange flexural steel
s/mm ρ/% longitudinal direction “T”-rebar lateral direction “A”-rebar extra flexural steel confinement steel (?13 mm) “C”-rebar
Nos. s Nos. s Nos. s
A1 14 13 150 1.76 10 90 26 300 - 106 150
A2 14 13 115 2.30 10 90 34 230 - 138 115
F1 14 13 140 1.88 10 90 28 280 - 114 140
F2 14 13 100 2.58 10 90 38 200 - 154 100
F3 14 13 110 2.43 10 90 36 215 - 146 110
F4 14 13 75 3.31 10 90 32 250 - 196 80
C1 14 13* 100 2.58 10 90 27 305 - 154 100
C2 14 13* 80 3.18 6 40 32 250 6- ?25 mm 96 165
C3 14 13* 75 3.44 10 90 27 305 - 100 150
C4 14 13* 65 4.13 6 40 30 190 6- ?25 mm 120 125
Tab.2  Reinforcement details for PC girder specimens
Fig.7  Test setup for high strength PC I-girders
Fig.8  Typical LVDT rosette installed on girder specimens at end zone
Fig.9  Shear force vs. net deflection curves for Group A PC girders
Fig.10  Shear force vs. net deflection curves for Group F PC girders
Fig.11  Shear force vs. net deflection curves for Group C PC girders
girder I.D. expt. ult. shear strength Vtest/kN a/d f c /MPa transverse steel expt. concrete contribution Vc/kN expt. failure mode
ρ/% balanced Vs, Eq. (7)/KN avg. strain ?avg expt. Vs/kN
A1 north 632.14 1.77 48.3 1.76 231.44 ?y 256.22 375.92 web-shear
south 519.82 - - -
A2 north 576.04 3.00 49.6 2.30 313.73 ?y 359.82 216.23 web-shear
south 551.77 191.95
F1 north 919.91 1.77 91.0 1.88 317.83 ?y 279.35 640.56 web-shear
south 896.72 617.37
F2 north 885.82 2.25 89.6 2.58 368.58 ?y 415.15 470.67 web-shear
south 841.83 426.67
F3 north 895.01 1.77 91.7 2.43 319.03 ?y 385.84 509.17 web-shear
south 904.99 519.15
F4 north 723.73 2.25 90.3 3.31 370.00 0.70 ?y 388.20 335.53 web-shear
south 786.13 397.94
C1 north 851.39 1.77 108.2 2.58 346.65 0.90 ?y 373.61 477.78 web-shear
south 766.87 0.85 ?y 352.88 414.00
C2 north 858.51 3.00 103.4 3.18 452.87 ?y 530.01 328.50 flexure-shear
south 745.08 0.85 ?y 450.52 294.56
C3 north 971.22 1.77 116.5 3.44 359.64 0.90 ?y 522.98 448.25 web-shear
south 1032.6 509.63
C4 north 875.85 3.00 105.5 4.13 457.37 0.70 ?y 499.71 376.14 flexure-shear
south 775.77 276.06
Tab.3  Calculations of steel and concrete shear contribution
Fig.12  Variation of the normalized concrete shear contribution with shear span to depth ratio for PC girders
girder I.D. expt. ult. shear strength Vtest/kN a/d f c /MPa transverse steel expt. concrete contribution Vc/kN expt. failure mode
ρ/% balanced Vs, Eq. (7)/KN avg. strain ?avg expt. Vs/kN
A1 north 632.14 1.77 48.3 1.76 231.44 ?y 256.22 375.92 web-shear
south 519.82 - - -
A2 north 576.04 3.00 49.6 2.30 313.73 ?y 359.82 216.23 web-shear
south 551.77 191.95
F1 north 919.91 1.77 91.0 1.88 317.83 ?y 279.35 640.56 web-shear
south 896.72 617.37
F2 north 885.82 2.25 89.6 2.58 368.58 ?y 415.15 470.67 web-shear
south 841.83 426.67
F3 north 895.01 1.77 91.7 2.43 319.03 ?y 385.84 509.17 web-shear
south 904.99 519.15
F4 north 723.73 2.25 90.3 3.31 370.00 0.70 ?y 388.20 335.53 web-shear
south 786.13 397.94
C1 north 851.39 1.77 108.2 2.58 346.65 0.90 ?y 373.61 477.78 web-shear
south 766.87 0.85 ?y 352.88 414.00
C2 north 858.51 3.00 103.4 3.18 452.87 ?y 530.01 328.50 flexure-shear
south 745.08 0.85 ?y 450.52 294.56
C3 north 971.22 1.77 116.5 3.44 359.64 0.90 ?y 522.98 448.25 web-shear
south 1032.6 509.63
C4 north 875.85 3.00 105.5 4.13 457.37 0.70 ?y 499.71 376.14 flexure-shear
south 775.77 276.06
Tab.4  Calculations of steel and concrete shear contribution
Fig.13  Variation of the normalized concrete shear contribution with shear span to depth ratio for PC girders
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