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University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 5-2011 Development of Design Guidelines for CIP Joint Connections with U-bar Reinforcement Richard Aaron Hanks University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Structural Engineering Commons Recommended Citation Hanks, Richard Aaron, "Development of Design Guidelines for CIP Joint Connections with U-bar Reinforcement. " Master's Thesis, University of Tennessee, 2011. https://trace.tennessee.edu/utk_gradthes/878 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Richard Aaron Hanks entitled "Development of Design Guidelines for CIP Joint Connections with U-bar Reinforcement." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in Civil Engineering. Zhongguo J. Ma, Major Professor We have read this thesis and recommend its acceptance: Edwin G. Burdette, Qiuhong Zhao Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Development of Design Guidelines for CIP Joint Connections with U-bar Reinforcement A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Richard Aaron Hanks May 2011 Acknowledgements I would like to thank my wife, Julie Hanks, parents, Richard and Glenda Hanks, and the rest of my family for their support and encouragement in pursuing a career in Structural Engineering. My education and career would not have been possible without their love and support. I would especially like to thank Dr. John Ma for encouraging and guiding me in pursuit of a Master of Science degree by providing this excellent opportunity to further my education to an important and applicable research project. Thanks to Beth Chapman and Sam Lewis for their exhaustive lab results and information. I am grateful for Zhiqi He for providing assistance in the strut and tie modeling. Thanks to Qi Cao for presenting and helping to navigate through the lab results. I would also like to thank Dr. Edwin Burdette for providing his professional expertise in reinforced concrete. My extended thanks go to Dr. Burdette and Dr. Qiuhong Zhao for being on my committee. ii Abstract The interstate highway system is vitally dependent upon current and future bridges. These bridges must be designed economically to continue the serviceability with limited maintenance. For precast bridge construction a portion of the design must consider the bridge connections. Some current connections have proved insufficient in serviceability as there is uncontrolled cracking. In other connections there are uncertainties in the calculations (or lack of calculations) which require design guidelines. This thesis presents design recommendations for precast decking u-bar reinforcement in tension which results from negative moment over a pier. Testing results from the University of Tennessee were analyzed to determine the design recommendations. The calculated capacity of the specimens was determined first by strut and tie modeling by AASHTO and ACI, but was shown to be insufficient. Proposed changes to the current calculation of the strut width as specified in AASHTO and ACI STM methods were discussed in order to match the test results. However, strut and tie modeling demonstrated that the design for the lacer bar was inadequate. Since the strut and tie modeling method resulted in an inaccurate lacer bar size, another method was developed. A triangular shape develops from the flow of forces in the connection joint zone; as a result, a free body diagram (FBD) was developed from the concrete triangular shape. This diagram showed how the forces flow in the in-situ joint as well as how they are resisted. A formula was developed from the FBD to determine the capacity of the joint which accurately reflected the capacities from tests. iii A FBD was also made of the lacer bar utilizing the forces and geometry calculated from the capacity calculations. A computer analysis program was used to determine the forces in the lacer bar. The lacer bar could then be designed since the required forces to resist (moment and shear) were known. A comparison of the strut and tie model to the triangular method led to the conclusion that both can determine the longitudinal reinforcement spacing, joint overlap length, and concrete strength, but only the triangular method can determine a more sufficient lacer bar size. iv Table of Contents Development of Design Guidelines for CIP Joint Connections with U‐bar Reinforcement .... i Chapter 1 Introduction ....................................................................................................... 1 1.1 Introduction ............................................................................................................. 1 1.2 Lab Research ............................................................................................................ 2 1.3 Literature Review ..................................................................................................... 7 Chapter 2 Strut and Tie Modeling .................................................................................... 11 2.1 STM for the joint connections ........................................................................... 11 2.2 ACI strut and tie modeling ................................................................................ 11 2.3 AASHTO strut and tie modeling ......................................................................... 14 2.4 Adjusted joint strut and tie model .................................................................... 14 Chapter 3 Triangular Method ........................................................................................... 20 3.1 Tension Joint Capacity Calculations ................................................................... 20 3.2 Lacer Bar ................................................................................................................ 27 Chapter 4 Recommended Design Criteria for the Triangular Method................................ 41 4.1 Area Calculations of the Bearing Strength Capacity................................................. 41 4.2 Limitations of design .............................................................................................. 43 4.2.1 Concrete compressive strength .............................................................................. 44 4.2.2 U‐bar spacing .......................................................................................................... 44 4.2.3 Overlap length ........................................................................................................ 46 4.3 Lacer Bar ................................................................................................................ 48 Chapter 5 Conclusion ....................................................................................................... 55 List of References ............................................................................................................. 58 Vita .................................................................................................................................. 61 v List of Tables Table 1: Testing parameters and capacities of tensile specimens .................................. 7 Table 2: Maximum forces in their respective joints ..................................................... 12 Table 3: STM calculated capacity verses testing ......................................................... 17 Table 4: Calculated verses tested capacities dependent upon different variables ........ 26 Table 5: Area design calculations comparison ............................................................. 43 Table 6: U-bar spacing capacity comparison of per triangle and per foot section ....... 45 Table 7: Joint overlap length capacity comparison ...................................................... 47 Table 8: Comparison of elastic and plastic design ....................................................... 51 Table 9: Deflection comparison of ST-0 for different rebar sizes ................................ 53 vi List of Figures Figure 1: A current precast concrete decking joint connection ...................................... 1 Figure 2: U-bar transverse joint ..................................................................................... 3 Figure 3: Headed bar transverse joint ............................................................................ 4 Figure 4: U-bar joint detail strain gauge configuration ................................................. 4 Figure 5: Headed Bar joint detail strain gauge configuration ........................................ 5 Figure 6: Tensile specimens WT-1, WT-2, WT-3, ST-0, ST-7, FT-0, and FT-7 with varying parameters shown in Table 1 ............................................................................ 6 Figure 7: Tensile specimen WT-4 with parameters shown

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