| Calculation of local compression bearing capacity is one of pivotal problems in design of prestressed concrete structure. A series of problems on local compression have been investigated in the eighties of the twentieth century. The research achievement has been involved in relevant national design criterions. Engineering practice and science research in latest years show that there are some problems in the calculation method of local compression bearing capacity in the current Code for Design of Concrete Structure ("the Current Code"for abbreviation) and they need to be improved. To solve these problems, five parts of research work are accomplished in this dissertation.(1) The influence of ducts and its diameter on the enhancement coefficient of concrete strength for local compression has not been taken into account in the calculation formula in the Current Code. Considering this problem, local compression experiments on 12 plain concrete prism specimens with ducts are completed. The influence of ducts'diameter and the ratio of calculated bottom area for local compression (Ab) to local compression area of concrete (Al) on local compression performance of plain concrete specimens have been researched. The first-hand experimental data are got, such as failure modes of specimens, features of the wedges, load-displacement curves and characteristics of crack distribution. Researches show that the enhancement coefficient of concrete strength for local compression decreases due to ducts, and the decrease degree increases with the increase of diameter of ducts. The law for decrease of concrete strength is the same in general for different Ab/ Al. The calculation formula for local compression bearing capacity of concrete considering the influence of diameter of ducts is brought forward, in which an influence coefficientλ_d is introduced. Theλ_d decreases linearly with the increase of the ratio of diameter of ducts to length of bearing plate and the ratio of diameter of ducts to length of specimen side. The second value has notable influence onλ_d.(2) The influence of concrete core area within the range for inner surface of indirect reinforcements on the local compression bearing capacity has not been reflected in the calculation formula in the Current Code. Considering this problem, local compression experiments on 29 concrete prism specimens with indirect reinforcements are completed. The influence of some factors on local compression performance of concrete specimens have been researched, such as the variety of indirect reinforcement, concrete core area and the ratio of the calculated bottom area for local compression to local compression area of concrete. The first-hand experimental data are got, such as failure modes of specimens, features of the wedges, load-displacement curves, characteristics of crack distribution and strain distribution of the indirect reinforcement. Researches show that concrete core area has notable influence on local compression bearing capacity. When the variety, diameter, number, and spacing of mesh indirect reinforcement keep constant, or the variety, diameter, and spacing of spiral indirect reinforcement keep constant, contribution of indirect reinforcements to local compression bearing capacity increases with the increase of concrete core area.The calculation method for local compression bearing capacity considering the influence of concrete core area is brought forward when the ratio of concrete core area (Acor) to local compression area of concrete (Al) is not less than 1.35. The idea is the enhancement coefficient of local compression bearing capacity due to indirect reinforcements (βcor) is replaced by a multinomial (5.91βcor-4.52) in the calculation formula in the Current Code.The calculation method for local compression bearing capacity is brought forward when Acor/Al is less than 1.35. The idea is the contribution of indirect reinforcements to local compression bearing capacity in the Current Code is multiplied by the reduction factor of strength of indirect reinforcements (λ_s). When Acor/Al<1,βcor equals to 1, and the net local compression area (Aln) in the indirect reinforcements contribution is replaced by Acor,n. Acor,n is the residual area of removing the ducts and caves from Acor.λ_s relates to Ab/Al and Acor/Al , and it increases with the increase of the product of the two ratios.(3) Considering the case that prestressed concrete beams are anchored in the side of boundary beam perpendicular to the prestressed concrete beam, local compression experiments on 12 concrete specimens which simulating this case are completed. The influence of boundary beam on local compression performance of anchorage zone of prestressed concrete beams have been researched with length of bearing plate and width of boundary beam varying and width of bearing plate keeping constant. The first-hand experimental data are got, such as failure modes of specimens, load-displacement curves and strain distribution of the indirect reinforcement. Researches show that boundary beam has strong restrictions on end anchorage zone of prestressed concrete beam. When the ratio of length of calculated bottom area outside the section of prestressed concrete beam to width of boundary beam is less than 2 and width of boundary beam is larger than the shorter length of local compression area, the calculated bottom area for local compression can be extended to the side face of boundary beam according to the principle of the local compression area is concentric or symmetric to the calculated bottom area.(4) Considering the applicability of calculation formulas on concrete local compression bearing capacity in present national standards to reactive powder concrete (RPC), local compression experiments on 48 RPC prism specimens are completed. Influences of RPC strength and the ratio of calculated bottom area for local compression to local compression area on RPC local compression performance have been researched. The first-hand experimental data are got, such as failure modes of specimens, characteristics of crack distribution, features of the wedges and load-displacement curves. Researches show that local compression performance of RPC is similar to the ordinary concrete. Local compression bearing capacity of RPC increases with the increases of Ab/Al. The enhancement coefficient of RPC strength for local compression is smaller than the ordinary concrete under the same Ab/Al. Local compression performance of RPC can be improved by mixing steel fiber into RPC, but the dosage of steel fiber has little influence on it.Based on experimental results, two kinds of calculation formulas for local compression bearing capacity of plain RPC and RPC with steel fiber are brought forward. In formula one of plain RPC, influence coefficient of RPC strength (βc) linearly decreases with the increase of Ab/Al, and in formula two, the single influence coefficient of local compression strength is uses to synthetically take into account the influence of strength of RPC and local compression on local compression bearing capacity of specimens. In formula one of RPC with steel fiber,βc is taken as constant and in formula two, the single influence coefficient of local compression strength is used to reflect the influence of factors on local compression bearing capacity of specimens, such as character and dosage of steel fiber, RPC strength and local compression.(5) Suggested methods for calculation of local compression load bearing capacity and placing of indirect reinforcement in end zone are presented.
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