W-band MIMO GB-SAR for Bridge Testing/Monitoring

Interferometric radars are widely used for static and dynamic monitoring of large structures such as bridges, culverts, wind turbine towers, chimneys, masonry towers, stay cables, buildings, and monuments. Most of these radars operate in Ku-band (17 GHz). Nevertheless, a higher operative frequency could allow the design of smaller, lighter, and faster equipment. In this paper, a fast MIMO-GBSAR (Multiple-Input Multiple-Output Ground-Based Synthetic Aperture Radar) operating in W-band (77 GHz) has been proposed. The radar can complete a scan in less than 8 s. Furthermore, as its overall dimension is smaller than 230 mm, it can be easily fixed to the head of a camera tripod, which makes its deployment in the field very easy, even by a single operator. The performance of this radar was tested in a controlled environment and in a realistic case study.

Simplified Calculation of Pylon Top Displacement of Multi-Pylon Suspension Bridge

The long-span multi-pylon suspension bridge is the subject of growing interest. Under live load, the longitudinal deflection of the mid-pylon is an important control parameter for a multi-pylon suspension bridge design. It is important to establish a simplified method of calculating pylon deflection for the preliminary design and selection of a multi-pylon suspension bridge. Based on deflection theory and deformation compatibility condition, considering main cable horizontal constraints and the interaction among pylons and girders with the methods of equivalent stiffness and moment distribution, the simplified calculation formulas of pylon displacement at the top for three-, four-, and five-pylon suspension bridges are derived. The validity of the formulas are verified by model experiment, real bridge testing, and finite-element analysis. For a floating system, the error between the simplified formula and the finite element method is less than 10%, and that of the model experiment is within 25%. For a consolidation system, the error between the simplified formula and the finite element method is within 16%, and that of the real bridge testing is less than 11%. As the number of pylons increases, the simplified formulas tend to be less accurate.

Dynamic Analysis and Test Validation for Continuous Girder Bridge

With the rapid development of technology of bridge, bridge as an important part of the traffic network, the safety of its operations was getting more and more attention by people. In order to ensure the bridge can be safe and reliable operating, the newly built bridge testing had become a necessary measures. In this paper, a three span continuous box girder bridge (28+36+28m) was taken as an example, To analyze and calculate its dynamic characteristics, the finite element software MISAS was used. And it was verified through experiments.