BRIDGE DECK OVERHANG CONSTRUCTION by Sean P. Clifton and Oguzhan Bayrak Technical Report: IAC 88-5DD1A003-2 conducted for the Texas Department of Transportation by THE UNIVERSITY OF TEXAS AT AUSTIN September 2008 Investigation performed in cooperation with the Texas Department of Transportation. ACKNOWLEDGMENTS We greatly appreciate the financial support from the Texas Department of Transportation that made this project possible. The support of the project monitoring committee, John Holt, Amy Eskridge and Randy Cox is also very much appreciated. DISCLAIMER The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the view of the Federal Highway Administration or the Texas Department of Transportation. This report does not constitute a standard, specification, or regulation. NOT INTENDED FOR CONSTRUCTION, PERMIT, OR BIDDING PURPOSES Bridge Deck Overhang Construction: Summary An experimental investigation was conducted at the Ferguson Structural Engineering Laboratory at the University of Texas at Austin to investigate the current bridge deck overhang construction practice as is relates to the use of the new Texas I- girders (Tx girders). Due to the wide and thin top flange of the Tx-girders, the Texas Department of Transportation funded a testing program to have the performance and behavior of the current systems for overhang forming investigated. The primary objectives of this investigation were to examine the performance of commercially available overhang forming products and provide recommendations for their use with Tx Girders. In order to achieve the goals set forth, four Tx-girders were fabricated in the laboratory and a total of thirteen load tests were performed on the overhang forming products and Tx girders. Recommendations for the use of overhang forming systems for the Tx girders were based on the results of the experiments and synthesis of those results. At the completion of the testing of the currently available systems for overhang forming, a new concept was developed to use a precast overhang as an alternate solution to create the finished bridge deck overhang construction. The solution involved precasting a portion of the overhang after the fabrication of pretensioned girders and using the precast portion of the overhang as stay-in-place formwork. i Table of Contents CHAPTER 1 Introduction .................................................................................... 1 1.1 Background ............................................................................................ 1 1.2 Objectives .............................................................................................. 1 1.3 Scope ..................................................................................................... 2 1.4 Program Overview: Chapter Outline ..................................................... 2 CHAPTER 2 Bridge Deck Overhang Construction ........................................... 5 2.1 Overview ............................................................................................... 5 2.2 Overhang Formwork ............................................................................. 5 2.3 Bridge Deck Finishing Screed ............................................................. 12 2.4 Bridge Traffic rail ................................................................................ 14 2.5 Overhang Bracket Removal ................................................................ 15 2.6 Summary .............................................................................................. 16 CHAPTER 3 Experimental Program ................................................................ 17 3.1 Overview ............................................................................................. 17 3.2 Products ............................................................................................... 17 3.2.1 Meadow Burke Products ............................................................... 17 3.2.1.1 HF-43 Precast Embed Hanger ................................................. 17 3.2.1.2 HF-67 Bulb Tee Bar Hanger ................................................... 20 3.2.1.3 HF-67-M Bulb Tee Bar Hanger (Modified) ............................ 22 3.2.1.4 HF-43-V Precast Embed Hanger (Modified) .......................... 24 3.2.1.5 HF-43-I Precast Embed Hanger (Modified) ............................ 24 3.2.1.6 HF-86 Bridge Overhang Bracket ............................................. 25 3.2.1.7 HF-96 Aluminum Bridge Overhang Bracket .......................... 27 3.2.2 Dayton Superior Products .............................................................. 29 3.2.2.1 C-24 45° Pres-Steel Precast Half Hanger Type 4-APR ........... 29 3.2.2.2 C-49 Bridge Overhang Bracket ............................................... 29 ii 3.3 Loading calculations on overhang systems ......................................... 31 3.3.1 Meadow Burke Products ............................................................... 31 3.3.2 Dayton Superior Products ............................................................. 32 3.4 Test Setup ............................................................................................ 33 3.4.1 Design ............................................................................................ 33 3.4.2 Construction .................................................................................. 37 3.5 TxDOT New I-Girder sections ............................................................ 38 3.6 Instrumentation .................................................................................... 40 3.6.1 Load cells ...................................................................................... 40 3.6.2 Linear Potentiometers ................................................................... 43 3.6.3 Strain Gauge Installation on Reinforcing Bars ............................. 44 3.6.3.1 Strain Gauge Locations: Transverse Reinforcing Bars in Top Flange ............................................................................... 44 CHAPTER 4 Test Results and Discussion ........................................................ 47 4.1 Introduction ......................................................................................... 47 4.2 Bracket-Hanger system loads .............................................................. 47 4.2.1 Frictional Resistance ..................................................................... 48 4.2.2 Hanger Forces ............................................................................... 51 4.2.3 Failure Mechanisms ...................................................................... 52 4.3 Test Results: Meadow Burke HF-43 ................................................... 53 4.3.1 Tx-28-I .......................................................................................... 53 4.3.2 Tx-28-II ......................................................................................... 57 4.3.3 Tx-46 ............................................................................................. 59 4.3.4 Tx-70 ............................................................................................. 62 4.3.4.1 HF-43-V .................................................................................. 62 4.3.4.2 HF-43-I .................................................................................... 65 4.3.5 Summary of Results: HF-43 .......................................................... 67 iii 4.4 Test Results: Meadow Burke HF-67 ................................................... 69 4.4.1 Tx-28-I ........................................................................................... 70 4.4.2 Tx-28-II ......................................................................................... 73 4.4.3 Tx-46 ............................................................................................. 75 4.4.4 Tx-70 ............................................................................................. 79 4.4.4.1 Tx-70 Test #1 .......................................................................... 79 4.4.4.2 Tx-70 Test #2 .......................................................................... 82 4.4.5 Summary of Results: HF-67 .......................................................... 85 4.5 Test Results: Dayton Superior C-24 .................................................... 87 4.5.1 Tx-28-I ........................................................................................... 87 4.5.2 Tx-28-II ......................................................................................... 90 4.5.3 Tx-46 ............................................................................................. 93 4.5.4 Summary of Results: C-24 ............................................................ 95 4.6 Recommendations ............................................................................... 97 4.7 Summary ............................................................................................ 101 CHAPTER 5 Precast Overhang ....................................................................... 103 5.1 Introduction ....................................................................................... 103 5.1.1 Current Practice ........................................................................... 103 5.1.1.1 Disadvantages .......................................................................