Study On The Measurement Of Strain And Deflection In The Test Detection Of The Bridge Structure

Strain and deflection must be measured in the experiment detection of bridge.Nowadays strain is usually measured with train chip. When using strain chip, bending the chip, welding the chip, and cuffing the chip usually need to do in the air. So it is difficult and the quality also can't be kept and the rate also is low. And the result is affected very much by the temperature and the moisture of the environment. And sometimes some of the results have much drift and low degree of belief.While measuring with optical fibre, the equipment is very pricy and the cost is high While measuring with string wire, the equipment is easily damaged and only used in long-term monitoring. So it is necessary to research an another better way to measure the strain.The double cantilever beam is analysed in the paper. And it is also proved practical to bring it in making sensing device. And such sensing device is also produced. The assignment test and the concrete prism comparison test are presented in the paper. The above experiments prove that the results of the equipment are very linear and the biggest percent of difference is only 0.25%. And the results have good repeating with the biggest percent of difference,0.23%. With the experiments of the real bridges, the sensing device is using very conveniently and need a little time. And it is also proved that it is little effected by the temperature and the moisture of the environment, and the results is stabled and have high degree of belief. And the sensing devices of the same batch have the same sensitivity to make the setting of the equipment very convinent. The design of the disassembly and assembly department has solved the problem of the contradiction of the high sensitivity required and the big energy of removal to avoid the damage in removal of the sensing device. And with the outside shell, the inner elastic elements is very durable.Nowadays the methods of measuring the deflection of the bridge are measuring with dial indicator, measuring with the hanger, measuring with the balance level, photoelectric method and so on. Measuring with dial indicator and measuring with the hanger both need the standtill point so that they are only suitable for the bridge with bed river. Measuring with precision level, measuring with GPS, measuring with the deflection device are easily effected by the weather and has low precision with the precision of millimeter, or even centimeter and need much time. They are only suitable for the measuring of big bridges. While being used in small bridges, they can't cater to the bridge engineering. So it is necessary to research an another better method to measuring the deflection.A new method, calculating the deflection with the measured slope angles of the sections of the bridge is presented in the paper. The principle of the QY inclinometer is introduced and the software transferring the slope angles to the matched deflection is also researched. How to arrange the inclinometers is also researched and the experiments of the continuous beams are also presented in the paper. The experiments proved it practical calculating the deflection with the slope angles. And such a method is very promising.