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Effect of Varying the Number of Transverse DiaphragmsThe effect of varying the number of transverse diaphragms posttensionedfrom 5, 4, 3, to 0 on the load distribution was insignificantwhen the bridge deck remained uncracked. The same deflection ofapproximately 5.33 mm (0.21 in.) was observed in each loadedbeam when the number of diaphragms was varied. After crackswere induced, the deflection of the loaded beam B4 (Fig. 8)was 10.41 mm (0.41 in.) when none of the diaphragms were posttensioned.Increasing the number of posttensioned diaphragms tothree or four significantly decreased the deflection in beam B4 to8.64 mm (0.34 in.). Increasing the number of diaphragms to fiveresulted in a slight decrease in beam B4’s deflection to 7.87 mm(0.31 in.). When TPT forces were applied, the deflections of theloaded and unloaded beams were almost equal and showed aneffective distribution of load in the bridge model. Yet, a slightreduction was seen in deflection when increasing the number ofdiaphragms posttensioned to five. The increase in the numberof transverse posttensioned diaphragms increased the lateralconfinement and improved the monolithic behavior of thebridge model.Strain DistributionTypical results from the strain-distribution tests are presented inFigs. 9–11. The results are compared with the AASHTO LRFD(2007) minimum transverse prestress limit of 1.7 MPa (250 psi).This is equivalent to a minimum strain of 60με for thisbridge model.At all TPT force levels, the transverse compressive strains werehighest above the outermost shear keys. The compressive straindecreased toward the center of the deck slab. Also, compressiveFig. 10. Strain distribution on the bridge model with 4 diaphragms posttensionedFig. 11. Strain distribution on the bridge model with 3 diaphragms posttensioned668 / JOURNAL OF COMPOSITES FOR CONSTRUCTION © ASCE / SEPTEMBER/OCTOBER 2011Downloaded 18 Nov 2011 to 198.111.39.24. Redistribution subject to ASCE license or copyright. Visit http://www.ascelibrary.org
strains were observed only near the active transverse diaphragmsand decreased to almost zero midway between the posttensioneddiaphragms. This showed that posttensioning at the transversediaphragms does not generate a uniform transverse compressionstate in the deck. An increase in the TPT force level from89–445 kN (20–100 kip) resulted in a corresponding increase inthe transverse strain on the bridge deck from 39με to 92με.However, the change in maximum strain when increasing theTPT level from 356–445 kN (80–100 kip) was insignificant.Effect of Bridge Width on Strain DistributionA comparison was made of the strain distribution in a narrow-widthbridge with that in a wider-width bridge. Transverse straindistributionresults of this seven box beam bridge (wider-width),at a TPT level of 356 kN (80 kip) applied to all five diaphragms,was compared with a previous study involving a four-box beambridge (narrow-width) with similar configuration and diaphragmarrangement (Grace et al. 2010). In the case of the four-beambridge, a transverse strain of 192με was observed along the exteriorFig. 12. Load versus deflection response of the box beam bridge modelFig. 13. Failure mode detail of the box beam bridge model (photo courtesy of Center for Innovative Materials Research, Lawrence TechnologicalUniv.)JOURNAL OF COMPOSITES FOR CONSTRUCTION © ASCE / SEPTEMBER/OCTOBER 2011 / 669Downloaded 18 Nov 2011 to 198.111.39.24. Redistribution subject to ASCE license or copyright. Visit http://www.ascelibrary.org
Page 2 and 3: This paper presents the experimenta
Page 4 and 5: (100 kip) force. The bridge was sub
Page 8 and 9: Fig. 14. Load versus strain respons

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