Foreword
This study was conducted for Headquarters, U.S. Army Corps of Engineers under Construction Productivity Advancement Research (CPAR) Work Unit LW4, "Repair Upgrade of Concrete CE Structures Using FRP Composites." The technical monitors were M.K. Lee (CECW-EG), D. Chen (CEMP-ET), and C. Harris (CEMP-CE).
The work was performed by the Materials Science and Technology Division (FL-M) of the Facilities Technology Laboratory (FL), U.S. Army Construction Engineering Research Laboratories (CERL). The CERL Principal Investigator was Orange P. Marshall, CECER-FL-M. Dr. Ilker R. Adiguzel is Acting Chief, CECER-FL-M, and L. Michael Golish is Acting Operations Chief, CECER-FL. The CERL technical editor was Gordon L. Cohen, Technical Information Team.
The Director of CERL is Dr. Michael J. O'Connor.
Contents
SF 298 1
Foreword 2
1 Introduction 7
Background 7
Objective 9
Approach 9
Mode of Technology Transfer 9
Units of Weight and Measure 102 Fiber-Reinforced Composites 11
3 Experimental Program 14
Test Specimens 14Experimental Results 19
Load and Deflection 19
Strains 21
Cracking and Failure Mechanism 22
Experimental Test Conclusions 234 Design Procedure for Hybrid Joists 25
Overview 25
Design Criteria and Assumptions 25
Design Procedure 25
Define Loading 25
Define Capacity of Existing Beam Section 26
Determine Load Requirement for Upgrade/Repair 27
Determine FRP Properties 27
Determine Configuration and Calculate Thickness of FRP 28
Check Stresses 29
Check Deflections 29
Determine Failure Mode 30
Detailing 30Design Example 30
5 Conclusions and Recommendations 33
References 35
Figures and Tables 36
Distribution
List of Figures and Tables
Figures
1 Joist configuration. 36
2 Joist prestressing tendon profile. 36
3 HJ-3 and HJ-4 web reinforcement. 37
4 FRP joist repair. 37
5 High-performance concrete strength versus time. 38
6 Prestressing tendon stress versus strain. 38
7 Prestressing and casting of hybrid joists. 39
8 Completed hybrid joist construction. 39
9 FRP application. 40
10 Gap in FRP upgrade of HJ-3. 40
11 Epoxy injection of voids. 41
12 Internal strain gage layout for HJ-3, HJ-4, HJ-6, and HJ-7. 41
13 External strain gage layout on HJ-3. 42
14 External strain gage layout on HJ-4. 42
15 LVDT locations on test specimens. 43
16 Potentiometer locations on test specimens. 43
17 Block diagram of data recording system. 44
18 Test setup. 44
19 Load versus deflection for HJ-3, HJ-4, HJ-6, and HJ-7. 45
20 Load versus deflection cycles for HJ-4. 46
21 Deflected shape for HJ-3. 46
22 Deflected shape for HJ-4 before repair (top) and after FRP repair (bottom). 47
23 Deflected shape of HJ-6. 47
24 Deflected shape for HJ-7. 48
25 Strain distribution for HJ-3. 49
26 Strain distribution for HJ-4. 50
27 Strain distribution for HJ-6. 51
28 Strain distribution for HJ-7. 52
29 Strain distribution along strand length of HJ-3. 53
30 Strain distribution along strand length of HJ-4. 54
31 Strain distribution along strand length of HJ-6. 55
32 Strain distribution along strand length of HJ-7. 56
33 HJ-3 upgrade FRP strains. 57
34 HJ-4 repair FRP strains. 58
35 Crack patterns for HJ-6. 59
36 Failure of HJ-6. 59
37 Crack patterns for HJ-7. 60
38 Crack patterns for HJ-3. 61
39 Failure of HJ-3. 62
40 Crack Patterns of HJ-4 prior to FRP repair. 63
41 Crack patterns for HJ-4. 64
42 Shear repair design procedure. 65
43 Simply supported beam. 65
44 Shear diagram. 66
45 FRP wrap repair. 66
Tables
1 Hybrid Joists Tested 67
2 Epoxy Material Properties 67
3 Yarn Properties 67
4 Fabric Properties 67
5 Composite Laminate Specification 68
6 Composite Material Properties 68
7 Casting and Release Dates for Each Hybrid Joist Web 68
8 Instrumentation for HJ-3 Upgraded With FRP 69
9 Instrumentation for HJ-4 Without FRP Repair 71
10 Instrumentation for HJ-4 With FRP Repair 73
11 Principal Experimental Test Results for Hybrid Joists 75
12 Camber and Deflection for Hybrid Joists (in.) 75
