Applied Research On Stress Loss Of Prestressed Silos

The unbonded prestressed concrete structure has been widely used in the construction industry,which can obviously improve the bearing capacity and service performance of the members,especially the silo structure,bear dynamic load.The prestress can bear the change of the force produced by the silo wall when loading and unloading materials.The application of prestress in large diameter silo not only saves materials but also simplifies construction.With the improvement of prestressed technology,many advantages make this technology more and more used.PRESTRESS technology has become one of the important indexes to measure a country’s construction technology level,and the correct understanding and calculation of prestress loss has also become an important link in engineering construction.Therefore,taking an unbonded prestressed concrete coal silo in Inner Mongolia as the research and monitoring object,the main work done and the conclusions obtained are as follows:1.The influencing factors of prestress loss are analyzed and the loss value is calculated.Through monitoring the stress of prestressed steel bar at the end of Silo Wall and testing the stress of common steel bar and concrete at one quarter of the silo wall,the stress change in the empty silo stage is obtained,and the law of stress loss at different parts is analyzed.2.Through the long-term test monitoring data processing,it is obtained that: with the change of time,due to the shrinkage and creep of concrete,the stress of the silo ring is redistributed to the common steel bar and concrete,and the compressive stress of the steel bar increases gradually with the time,the compressive stress of concrete decreases with time,the loss of prestressing tendon decreases with time and finally tends to be flat.3.The stress loss of prestressed steel bar in the lower end of empty bin is about 280 MPA,and the value of stress loss of different height is different,the loss of code calculation is larger than that of actual measurement,the loss of steel bar is loose,the loss of shrinkage and creep of concrete accounts for 12.4% of the total loss.As the silo was not put into use and the loss was not fully completed,the monitoring loss was relatively small.4.Using the finite element software,the stress of the silo under the condition of half silo and full silo is analyzed when the loss is basically completed in the empty silo,and the concrete part of the silo wall is compressed under the condition of prestressed concrete,with the increase of the height of the storage load,the circumferential tensile force decreases gradually and the maximum circumferential force is located about 12 meters above the lower end of the silo.When the silo is full,the maximum tensile force of concrete is 0.884 MPA,the silo will not produce cracks and the structure is safe.