Tang Hongwei, Li Wansheng, Li Yuhong
APPLICATION ON MEASUREMENT OF PRE-STRESS LOSS IN CONCRETE STRUCTURE WITH FIBER-OPTIC SENSORS

As one of the important works in the pre-stressed concrete structure design, magnitude of the pre-stress loss has not been measured conveniently until now. A suitable measuring technique for pre-stress loss is the studying goal of researcher in a long time. In the present work, the fiber-optic measuring technique has been introduced to measure the pre-stress loss, and all of the measuring works were conducted on the model of a wastewater tank. Result of the measurement shows that optical fiber sensor can be used to measure the pre-stress loss in engineering, and the short-term pre-stress loss of steel strand is strongly effected by the arranging manner of steel strand, the magnitude of pre-stress loss measured in the present work is less than 20%.

W. Habel, D. Hofmann, F. Basedau, A. Barner, S. Crail, D. Reichel, U. Schreiner, E. Lindner
STATIC AND DYNAMIC MEASUREMENTS ON A NEWLY DEVELOPMENT PRECAST CONCRETE TRACK FOR HIGH SPEED RAILWAY TRAFFIC USING EMBEDDED FIBER-OPTIC SENSORS

In a German slab track system (“Feste Fahrbahn” FF, system Bögl) for speeds up to 300 km/h and more different fibre optic sensors have been embedded in several levels and locations of the track system. The track system consists of prestressed precast panels of steel fibre concrete which are supported by a cast-in-situ concrete or asphalt base course. The sensors are to measure the bond behaviour or the stress transfer in the track system. For that, tiny fibre-optic sensors - fibre Fabry-Pérot and Bragg grating sensors - have been embedded very near to the interface of the layers. Measurements were taken on a full scale test sample (slab track panel of 6.45 m length) as well as on a real high speed track. The paper describes the measurement task and discusses aspects with regard to sensor design and prefabrication of the sensor frames as well as the embedding procedure into the concrete track. Results from static and dynamic full scale tests carried out in the testing laboratory of BAM and from measurements on a track are given.

J. Kim, Y. Park, I. Choi, D. Kang
DEVELOPMENT OF SMART ELASTOMERIC BEARING EQUIPPED WITH PVDF POLYMER FILM FOR MONITORING VERTICAL LOAD THROUGH THE SUPPORT

This paper presents a smart elastomeric bearing using PVDF polymer film, which is very sensitive to dynamic loading condition. The PVDF polymer film is inserted into the elastomeric bearing to monitor the normal load, which is applied to the bridge structure. Therefore, the prototype of the smart elastomeric bearing is finally fabricated with the electric circuit for signal of the PVDF polymer film subjected to vertical loading. The evaluation system for smart elastomeric bearing is manufactured with shake, accelerometer and plate. The bearing was tested under sinusoidal loading condition. Finally the system confirmed that real time measurement of elastomeric bearing reaction provides the structure with certain intelligence.

H. C. Schoenekess, W. Ricken, J.-G. Liu, W. -J. Becker
EDDY-CURRENT SENSORS AND THEIR APPLICATIONS TO FORCE AND STRESS MEASUREMENT IN STEEL REINFORCED CONCRETE

The monitoring of bridge constructions can be performed by optimised eddy-current sensors to recognise damages earlier and to reduce rehabilitation expenses. The aim is to measure the coil impedance of an eddy-current sensor positioned close to a pre-stressing cable and to conclude the change of stress in steel of reinforced concrete elements. For this purpose, measurements were taken with specified specimen to investigate the influence from the air gap variation and hysteresis curve.

Eugen-Georg Woschni
EDUCATIONAL METHODS AS MATHEMATICAL AND PHYSICAL APPROACHES DEMONSTRATED WITH TYPICAL EXAMPLES

Three typical examples with great relevance to practice are demonstrating that as well mathematics as physics must be used to solve problems and especially to gain closed solutions as necessary for application in practice. Therefore both methods have to be teached in measurement education also to-day.