| The prestressed concrete T-shaped beam bridge which is constructed from the simply supported type to the continuous type,is used on a large scale in China.It is also the main type of bridges which spans are small and medium on the expressway.However,the serious problems as cracks are gradually exposed in the negative moment zone,which will affect the function of bridges.The analysis shows that the main reason is that the prestressed force is implemented by using the tooth plates in the current structural design of the negative moment zone.The construction method needs aloft work by hanging basket,and the working plane is narrow.That will result in the difficulties and quality problems owing to the uneven levels of existing construction companies.Therefore,according to the existing problems of the negative moment zone in the T-beam,the improved construction technology is proposed,which is more reasonable and convenient for the construction.In this way,the advantages of the bridge can be presented to ensure the safety of operation and prolong the service life of the bridge,which has the great practical significance.To solve problems of T-shaped bridges,the main researching contents and conclusions are as follows:(1)The present situations of the research on the application of this type of bridges at home and abroad was investigated.The main problem is concentrated in the negative moment zone.It is characterized by the serious cracks on the top of the pier,affecting the durability and the bearing capacity of the structure.The reason is due to the complex construction process which results from the existing structural type and prestressed implementation.Therefore,it is difficult to guarantee the quality of the construction and apt to cause the excessive prestressed losses.(2)Combined with the purpose of this paper,the principle of the design and the deflection calculation theory of the prestressed structure were analyzed.Then,the analytical calculation and deflection formulas by the prestressed effect were deduced.So,a single beam was taken as an example to calculate the effect of the prestressed length and alignment on the prestressing force and deflection.Meanwhile,the responses to the structural deflection and stress of the control section were calculated with prestressed losses.Next,the influential degrees of the effective prestressing force on the deflection and stress were analyzed.The results showed that the influential degree ranged from high to low and they were successively the effective prestressing force,the length,and alignment of the steel beam.The three factors above should be reckoned in the improved structure.(3)Aimed at the shortage of the traditional structure,a new structure of negative moment section and its construction technology were developed.The durability of the bridge could be improved,and the construction process was also simplified.In addition,the construction environment was improved,and the construction quality could be controlled.Eventually,the problems as prestressed losses and the cracks of negative moment zone could be solved,which would play a greater role in mechanical and economic advantages of T-shaped beam bridge converting from the simply supported type to the continuous type.(4)The MIDAS/Civil and ABAQUS software were adopted to simulate the new and the traditional structure.The static,dynamic parameters,the response of the prestressed losses and local stress of the two structures were compared and analyzed.The results showed that the mechanical performance of the traditional structure had been improved via the new structure.(5)Based on the Old Courtyard Bridge,the application research on the T-shaped beam bridge converting from the simply supported type to the continuous type was carried out by using the improved structure.Then,the feasibility of the improved structure and construction technology was verified.Meanwhile,the actual effects were tested,which would provide a demonstration project for the further application. |
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