CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 1 of 13 REPORT ON COUNTERMEASURE OF CRACKING OF SUPER T GIRDER I. General After first girder casting finished, through process of monitoring, we found that there are some cracks and breaking concrete at locations as follows: Location: 1. Crack at contiguous location of void and solid section; 2. Location: Crack at angle of contiguous location of void and solid section; 3. Location: Crack of angle on girder end; 4. Location: Traverse crack of girder end; 5. Location: Breaking angle of bottom of girder; 6. Location: Breaking of partition of girder. Reasons: During process of construction, cracks may be appear: because of Creation of formwork, sequence of disassemble formwork, cut PC strands…. are not suitable which cause local stress in concrete of girder over allowable limitation, simultaneously some steel re-bars of girder end is short of length comparing with technical design drawing. Reference of some projects constructed (Ring Road No. 3) also happened situation as the above mentioned. After applied some solutions to treat, it reached good result, therefore we would like to propose some solutions as follows: CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 2 of 13 II. Countermeasure: 1. Location: Crack at contiguous location of void and solid section: (See picture in Appendix 1) + Countermeasure: Add more 6 rebars A1-D12, L=1000 mm, @200mm at the connection between void and solid of the girder CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 3 of 13 2. Location: Crack at angle of contiguous location of void and solid section: (See picture in Appendix 2) + Countermeasure: Add a re-bar A2-D12, L=3421 mm and a re-bar A3-D12, L=2928 mm CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 4 of 13 3. Location: Crack of angle on girder end (See picture in Appendix 3) + Countermeasure: Add 2 re-bars A4-D12, L=720 mm and add 2 re-bars A5-D12, L=610 mm, @50 mm. And cut 1.3m formwork of girder flange so that when cut cable we can disassemble formwork CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 5 of 13 4. Location: Traverse crack of girder end (See picture in Appendix 4) + Countermeasure: Extend bar NY10-D16 and bar NY11-D16 with length 1329 mm into length 1440 mm. A B CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 6 of 13 5. Location: Breaking angle of bottom of girder (See picture in Appendix 5) + Countermeasure: - Cutting bottom formwork of girder end and change by rubber cushion (panel). - Be careful during compacting concrete 6. Location: Breaking of partition of girder (See picture in Appendix 6) + Countermeasure: - Surface grinding of angle of internal formwork, cleaning carefully before installing - When disassemble internal formwork, using 6 jacks to lift internal formwork up (replace the use 4 jacks as used on site) after that using gantry crane to crane internal formwork out of. CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 7 of 13 7. We propose change sequence to cut cable as follows: - The procedure of cutting strands as follows: from strand No. 18→ 6→ 30→ 31→ 17→ 19→ 5→ 7→ 29→ 32→ 16→ 20→ 4→ 8 → 28→ 33→ 15→ 21→ 27→ 34→ 14→ 22→ 38→ 39→ 26→ 35→ 13→ 23→ 37→ 40→ 25→ 36 → 12→ 24→ 41→42 → 3→ 9→ 2→10 → 1→11. CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 8 of 13 Appendix 1 Crack at contiguous location of void and solid section CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 9 of 13 Appendix 2 Crack at angle of contiguous location of void and solid section: CIVIL ENGINEERING CONSTRUCTION CORPORATION No.4 PROJECT MANAGEMENT BOARD – NHAT TAN P-3 Page 10 of 13 Appendix 3 Crack of angle on top of girder end