The Implementation of Full Depth UHCP Waffle Bridge Deck Panels

APPENDIX A: SUMMARY AND CONCLUSIONS

As the first part of a study that is aimed for the first application of the full depth UHPC waffle deck panels in the field, an experimental investigation on a UHPC waffle deck panel system consisted of two panels was conducted at Iowa State University to examine the structural performance of the UHPC waffle deck, critical connections and system performance. A total of six tests were conducted and the key results obtained from the different tests, indicating that that the overall performance of the system was satisfactory under the service, fatigue and ultimate load conditions are summarized below.

Panel Service Test (Test 1)

Load applied: 16 kips x 1.33 (33% IM factor) = 21.3 kips
Maximum measured panel displacement: 0.03 inches (< 0.11 in. of allowable deck displacement at the service load specified by AASHTO, section 9.5.2)
Maximum measured strain in panel bottom reinforcement = 375x10^-6
Maximum measured strain in joint bottom transverse reinforcement = 40 x10^-6
Measured crack width in the transverse rib < 0.002 in. ( • 0.017 inches, the allowable crack width by AASHTO, 2007; • 0.0118 inches of crack width expected for the fiber pullout (AFGC 2002))
No cracks developed in the joint region.

Joint Service Test (Test 2)

Load applied: 16 kips x 1.75 (75% IM factor) = 28 kips
Maximum measured panel displacement : 0.022 inches (< 0.11 in., allowable deck displacement at service load by AASHTO, section 9.5.2)
Maximum measured strain in panel bottom reinforcement: 160 x10^-6
Maximum measured strain in joint bottom transverse reinforcement: 175 x10^-6
Measured crack width in the transverse ribs forming the joint < 0.002 in. ( • 0.017 inches, the allowable crack width by AASHTO, 2007; • 0.0118 inches of crack width expected for the fiber pullout (AFGC 2002))

Joint Fatigue Test (Test 3)

Load applied = 16 kips x 1.75 (75% IM factor) = 28 kips
Number of load cycles = 1 million cycles at 2 Hz frequency.
Maximum measured panel displacement = 0.024 inches (< 0.11 in., allowable deck displacement at service load by AASHTO, Section 9.5.2)
Maximum measured strain in panel bottom reinforcement: "not measured"
Maximum measured strain in joint bottom transverse reinforcement: 150 x10^-6
Measured crack width in the transverse ribs forming the joint = 0.0017 in. (• 0.017 inches, the allowable crack width by AASHTO, 2007; • 0.0118 inches of crack width expected for the fiber pullout (AFGC 2002))
No fatigue damage occurred to the joint or the panels.

Joint Ultimate Test (Test 4)

Load applied = 3.0 x 16 kips = 48 kips
Maximum measured panel displacement = 0.052 inches (< 0.11 in., allowable deck displacement at service load by AASHTO, section 9.5.2)
Maximum measured strain in panel bottom reinforcement = 360 x10^-6
Maximum measured strain in joint bottom transverse reinforcement: 325 x10^-6
Crack width in the transverse ribs forming the joint = 0.003 in. (• 0.017 inches, the allowable crack width by AASHTO, 2007; • 0.0118 inches of crack width expected for the fiber pullout (AFGC 2002))
Multiple cracks were observed in the transverse and longitudinal ribs adjacent the joint.

Panel Fatigue Test (Test 5)

Load applied: 16 kips x 1.33 (33% IM factor) = 21.3 kips
Number of load cycles: 1 million cycles at 2 Hz frequency.
Maximum measured panel displacement : 0.039 inches (< 0.11 in., allowable deck displacement at service load by AASHTO, section 9.5.2)
Maximum measured strain in panel bottom reinforcement: 450 x10^-6
Maximum measured strain in joint bottom transverse reinforcement: 150 x10^-6
Measured crack width in the transverse ribs of the panel < 0.0023 in. ( • 0.017 inches, the allowable crack width by AASHTO, 2007• 0.0118 inches of crack width expected for the fiber pullout (AFGC 2002))
No fatigue loading damage observed to the panel and joint

Panel Ultimate Test (Test 6)

Load applied = 2.5 x 16 kips = 40 kips
Maximum measured panel displacement = 0.08 inches (< 0.11 in., allowable deck displacement at service load by AASHTO, section 9.5.2)
Maximum measured strain in panel bottom reinforcement: 880 x10^-6
Maximum measured strain in joint bottom transverse reinforcement: 100 x10^-6
Crack width in the transverse ribs forming the joint = 0.008 in. ( • 0.017 inches, the allowable crack width by AASHTO, 2007; • 0.0118 inches of crack width expected for the fiber pullout (AFGC 2002))
Multiple cracks in the transverse and longitudinal ribs of the panel.

Conclusions

Based on the experimental testing of the UHPC waffle deck system under service, ultimate and fatigue load conditions, the following conclusions are drawn for the prototype bridge system:

Overall system behavior of the UHPC waffle deck bridge system would be satisfactory.
The UHPC waffle panel or the joints are not expected to experience any fatigue damage under service loads.
Displacements of the bridge deck under service conditions will be much smaller than the AASHTO specified allowable limits.
The provided reinforcement and the use of wet UHPC infill for the joints will be satisfactory.
Expect hairline cracks to form in the prototype bridge on the underside of the deck under service conditions.
Crack widths will be negligibly small and are not expected to widen due to repeated loading under the most critical service conditions
Larger cracks may form if the boundary conditions of the deck are altered from what was used for the test setup (e.g., by providing rigid connections between the deck and abutments).
Dowel bars attached to the sides of the panels to form a positive connection with an interior girder experienced stresses in the order of 3 to 8 ksi and these bars should be included in the prototype bridge.

Recommendations

In light of the conclusions established from the study, the proposed waffle deck panel can be used in the Wapello County prototype bridge, provided:

Connection reinforcement matches or marginally exceeds those provided in the test unit; and
Moment demands on the slab are kept below those induced during the tests for various limit states.

References

AASHTO LRFD Bridge Design Specifications, American Association of State Highway and Transportation Officials, Washington, D.C., 2007
AFGC (2002) Association Française de Génie Civil Interim Recommendations for Ultra High Performance Fibre–Reinforced Concretes. SETRA (Service d'études techniques des routes et autoroutes). (Bétons Fibrés à Ultra-Hautes Performacnes – Recommandations Provisoires), France.
http://www.zellcomp.com/infrastructure_crisis.html, cited on 3rd March 2010.
Bhide, S., Material Usage and Condition of Existing Bridges in the US, PCA, Skokie, Illinois USA, 2001.
FHWA, 2007. Analysis of an Ultra–High Performance Concrete Two–Way Ribbed Bridge Deck Slab, TECHBRIEF, FHWA–HRT–07–055, McLean, VA.
Keierleber, B., Phares, B., Bierwagen, D., Couture, I. and Fanous, F. 2007. Design of Buchanan County, Iowa, Bridge Using Ultra High Performance Concrete and PI Girders. In Proceedings of the 2007 Mid–Continent Transportation Research Symposium, Ames, IA, 2007.
Kim Stantill–McMcillan and Cherilyn A. Hatfield (1994) "Performance of Steel, Concrete, Prestressed Concrete, and Timber Bridges", in Developments in short and medium span bridge engineering '94: Proceedings of 4th International conference on short and medium span bridges; 1994 August 8–11; Halifax, Nova Scotia, Canada. Montreal, P.Q., Canada: The Canadian Society for Civil Engineering; 1994: 341–354
Perry, V., Scalzo, P., and Weiss, G. 2007. Innovative Precast Deck Panels and Field–Cast UHPC Joints for Bridge Superstructures, In Proceedings of the PCI National Bridge Conference, 53rd PCI Annual Convention, Phoenix, Arizona.
Sritharan, S. 2009. Use of UHPC for Sustainable Bridges in Seismic Regions. In Proceedings of the 2009 US–Korea Conference on Science, Technology and Entrepreneurship; Main Theme: Creative Minds for Global Sustainability, Raleigh, NC.
Vande Voort, T., Sritharan, S., and Suleiman, M. T. 2007. A Precast UHPC pile for Sub structural Applications. In Proceedings of the PCI National Bridge Conference, 53rd PCI Annual Convention, Phoenix, Arizona.
Vande Voort, T., Suleiman, M. T., and Sritharan, S. 2008. Design and performance verification of ultra–high performance concrete piles for deep foundations. IHRB Project TR–558 Report, Iowa Department of Transportation.