Research On Prestressed Intelligent Tensioning System

The prestress bar is an important part of prestressing construction. Traditional prestress stretching system is a construction technology which driven by oil-pump-driven jack. The system get the value of tensioning force by the pressure gauge reading and the value of stretching extension of prestressed strand by manual measurement. There are many problems during prestressing, for example large error of stretching force, inaccurate measurement of the stretching extension of prestressed strand, difficulty in measuring the effective stress of prestress bar, difficulty in realization of synchronization control for stretching force and the value of stretching extension of prestressed strand and so on.This paper studies the intelligent prestress tension system. The system control pumps and jacks by the combination of PLC and touch screen. The value of force is control object during prestressing and elongation of prestressed strand is calibration. The system measured real-time-data by pressure sensor and displacement sensor dnd then feedback the measurement result to the control system. According to the tension of each tensioning device and elongation of prestressed strand, it conduct analysis and judgement. According to the analysis results, corresponding control command will be passed to tensioning device by the operating system for realizing precise control of prestressed stretching force and elongation of prestressed strand. During prestressing, stretching force and elongation of prestressed strand displayed in real time on the touch screen. When the stretching is finished, tension data is stored and then report is automatically generated and the operator may to view the historical data at any time, which ensure the authenticity and accuracy of stretching construction. When fail to compl ? with the construction requirements, the system will immediately stop the tension and produce sound-light alarm.The research of the prestressed tension system of the subject has the following innovation points: the first, the traditional prestressed tension machine uses feed through prestressing jack. In this subject, we adopts cassette jack which can save steel strand length and cost; secondly, the electro hydraulic proportional control technology is applied to prestressed tension system. The electro hydraulic proportional control technology uses feedback loop control system to load pressure, and can make the output pressure reach very high accuracy. Besides, the stability of the holding time is long enough, and the steel strand can be evenly and slowly tensile, which effectively ensure the safety of the prestressed tensioning construction.This paper introduced the importance of the prestressed tension and the current situation of the prestressed tension equipment, and described the general design scheme, hardware selection and software design of tension program in detail. At the same time, we made the design of prestressed tension hydraulic system and made the model and simulation for the electro-hydraulic proportional pressure closed loop control system, which ensures that the system can achieve the prestressed tension.The prestressed tension system can control the stress and displacement by double control ways. It has the advantages of high precision, high efficiency, good real-time performance, simple operation, and automatic generation of reports, which can meet the requirements of engineering applications, with a broad engineering background and good application prospects.