Composite Prestressed Pipe Pile Mechanical Testing And Finite Element Analysis

Because of the complexity and variety of the foundation conditions, many researchs and applications have been carried on foundation treatment and reinforcement, foundation pit bracing and new type basal design. Among all these, the prestressed pipe piles, which adopt pretensioned technics, centrifugal molding and steam maintain, is developed rapidly for the advantages of high bearing capability, quality ensurence, short construction period, variety of pipe piles, and easily matching. But the pipe piles are used individually in pile engineering, the wall thickness is about 1/5 of the pipe pile diameter. So the deadweight is heavy.In the thesis, compound prestressed pipe piles which high-pressure jet piles or deep mixing method is adopt as piles core, equal diameter prestressed concrete pipe piles is inserted should be studied. The concrete and the prestressed concrete pipe piles can co-work (the wall thickness would be 1/10 of the pipe pile diameter). Because the pipe piles are forced immediately after the concrete piles is casted, the pressure needed is less. So the problem of pressing pipe piles in sandy soil by static pressure is solved. Thecompound prestressed pipe piles have high resist bending and shear capability, so it can be used in deep foundation pit bracing.The mechanical properties of thecompound prestressed pipe piles are studied. The contents are the following:1) Thecompound prestressed pipe piles are schemed out and the bearing capability is analyzed in theory.2) The bend test project ofcompound prestressed pipe piles is designed, and 4compound prestressed pipe piles bending bearing test and 2compound prestressed pipe piles joint components intensity test were carried. According to the tests, sectional average strain graph and loading-flexibility curve(F-f) of the pipe piles are drawn out. Then the cracking bending moment and ultimate bending moment and flexibility, and joint components ultimate bending moment and breakage moment of 4compound prestressed pipe piles are compared . The results show that the consistent quality and ductility requilments of the designed prestressed pipe piles is satisfied, and the prestressed pipe piles joint components intensity is also satisfied.3) The finite element software is adopted to count the press bearing capability of thecompound prestressed pipe piles. First the press bearing capability of thecompound prestressed pipe piles and the prestressed pipe piles without core are compared, then the stress chart and the load-displacement chart of the 850mm, 1100mmcompound prestressed pipe piles without core andcompound prestressed pipe piles in different conditions are drawn out, at last, based on the results, a calculate formula is proposed for compress resistance bearing capability of thecompound prestressed pipe piles.