The development of structural health monitoring technique of external prestressing tendon for precast segmental box girders by cable vibration measurement | |
| Author | Narawich Thanawongwat |
| Call Number | AIT Thesis no.ST-19-03 |
| Subject(s) | Structural health monitoring Reinforced concrete construction |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Structural Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. ST-19-03 |
| Abstract | Monitoring and determination in tension force of external prestressing tendons in the segmental box girder bridges is very essential to investigation and maintenance of structure over its service life. Incomplete grouting along tendon duct due to improper grouting process is one of concerned problems which may result in void in some area. In addition, the insufficient coverage for PC strand in tendon may lead to the risk of corrosion and tension loss unfortunately. There are several techniques which were used to inspect and check these problems. One such approach has been widely used to access these effects is to use a dynamic identification method. The first two mode frequency (f1and f2) created by an impact excitation are introduced and determined the tendon segment’s tension, bending rigidity and unit mass using a differential equation describing a stiff sting with fixed end boundary conditions. To ensure the reliability and validity of identification technique, the experimental investigation is carried out into two main experiments. Firstly, the model for tendon with typical diameter 9.5 mm and 12.7 mm seven-wire strand are chosen for case study of PC strand (less bending rigidity effect). Second, the model for grouting were comprised of PC strand with a diameter 12.7 mm and HDPE duct with a diameter 63 mm which this model was conducted in order to study the different bending rigidity effect in each direction and uncertainty of grout quantity by varied grouting in tendon duct. In each model, a specimen is tensioned by prestressing machine and fixed by anchor grips. The tension force is then directly measured by load cell. Unit mass obtained by weighting. Flexural rigidity determined by bending rigidity testing (Only conducted for grouting). For the vibration response, accelerometers were used to be a signal sensor in study cases of PC strand. For grouting case, accelerometers and strain-gauges were placed in vertical and horizontal direction, including inside the duct to process frequency domain by using Fast Fourier Transform in each direction. The experimental investigation proves the reliability and validity of the identification technique which can estimate the tension, unit mass and bending rigidity with fair accuracy. Finally, for field measurement, monitoring and investigation of segmental posttensioned bridges were investigated in Udon-Ratthaya and Ngamwongwan expressway to estimate the tension force by using identification technique. In addition, when the more numbers of mode frequency were taken into the identification techniques for this study (f1to f5), the more results are corresponding with theory. |
| Year | 2019 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. ST-19-03 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Punchet Thammarak; |
| Examination Committee(s) | Pennung Warnitchai;Anwar, Naveed; |
| Scholarship Donor(s) | Royal Thai Government Fellowship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2019 |