| The anchorage zone of the pylon is a key part for cable-stayed bridges, where the local concentrated force of cable will be transferred to the pylon safely and uniformly. Because of the powerful local concentrated forces, anchoring forces from prestressed steels and weaken factors from opening holes, the strength state at this area is very complicated. Therefore, analysis of strength performance at the anchorage zone of cable-stayed bridge tower has been attracted attention in bridge engineering all the time and anchorage zone of tower is also the difficult and important part in designing and constructing of cable-stayed bridge. Based on Song Huajing River Bridge at Sifangtai, clear numerical analysis and reliable full-scale model test for the anchorage zone segment on the tower were carried out, and the optimum plan was also proposed in this paper.At first, utilized ANSYS to analyze the anchorage zone on the cable bent tower and investigate stress distribution and deformation at the area. The analysis results by FEA indicated that the horizontal direction stress compared with the vertical direction stress was important. During the prestressing stage, prestressed steels converged at the anchorage zone where the stress distributed complicatedly. Especially influenced by horizontal prestressing force of great tonnage tension, great local tension stress would appear at a small area from the tip in the long inboard of the model. It had been proved by theories and experiments.The construction technique experiment of prestressed steel bundles for anchorage zone on the cable bent tower was performed. The testing condition was same to real construction technique of main tower in order to practice tower's construction technique strictly and accumulate experience for tower's construction. By test plastic corrugated pipes' friction factor was determined, the extension of prestressed steel bundles was measured and analyzed, and the vacuum pumping technique was investigated. In the small radius and large tonnage the radial force loading on the ducts would be increased, and the prestressed steels would not touch the duct in a point but were embedded into it. The friction factor would be remarkably increased, but the current national regulation has not had clear specifications to this yet. For many small radius and large tonnage situations, k and u should be determined according to the results of model test. The plastic corrugated pipes' friction factors were determined by test and its value was between 0.12 and 0.15. The factors influencing the extension of prestressed steel bundles are various. Generally speaking, the results of extension got in the test and theories are different. In this experiment, the influence degree of various kinds of factor was investigated and the tension technique to reduce the extension of prestressed steel bundles was discussed. The results of the test indicated that 25% σ con pretension can reduce the extension of prestressed steel bundles caused by uniform force. In the test, the vacuum assistant pumping technique of practice was adopted to guide the construction and determine the proper motor mix proportions. Results of the test indicated that when the vacuum assistant pumping technique was used in thegrouting of prestressed concrete structures' ducts, the pumping degree of saturation and the degree of compaction were high, so the method was worth popularizing.Full-scale model test of the anchorage zone segment on the cable bent tower was done. The anchorage zone is a key part of cable-stayed bridges, where the horizontal forces are enormous. At the same time, there are other kinds of forces and the weakening effects by holes, so the strength state is very complicated. However the single axial symmetry similar hexagon section of main tower for Song Huajing River Bridge at Sifangtai was used in China for the first time, and the strength state was so more complicated that simple theory could not analyze the real stress distribution and deformation at the anchorage zone. Compared results of the model test of the full-scale with that of FEA: during the pretension stage and before concrete fracture, the stress got by test corresponded with the results got by FEA. It indicated that FEA could be utilized to analyze the anchorage zone of tower, which is in complicate stress state. According to the result of the test, the cracking load of the tower was 14500kN, and the safe factors for cracking was 2.07. Because along the bridge the towers were asymmetrical, the stress in the north and south sides distribute nonuniformly and there were greater circumferential tension stress at the tower wall of southern side, the crack developed very fast. In view of this, the prestressed steel bundles at the south side of tower should be strengthened. At the corner of east and west short side of the model and under the anchor, the stress concentration was obvious, so circumferential steels should be added there and the spiral stirrup should be reinforced around holes of cables.Optimize the arrangement of prestressed steel bundles which are important to improve the strength performance at this area. Because the sectional type of the tower that the wall of the tower was shot along the north side of the bridge was special, it is difficult to assign independent prestressing steel bundles in line. The rational assignment of prestressed steel bundles was special and the optimum was that making sure the number of prestressed steels in bundles. Among the plans of arrangement of prestressed steel bundles, after optimum, when N1=l 1, N2=8, N3=5, N4=6, the strength performance was the best.Assigning steel crossbeams or steel-concrete crossbeams in the concrete tower could endure the horizontal force, vertical force and eccentric moment effectively. The function and the strength spreading of the crossbeam was relatively clear in the comparatively simple symmetrical structures, but in the complicated asymmetrical structures, strength loading and strength spreading form changed, so it was necessary to discuss its function performed in structure of main tower. By FEA, the stresses were not remarkably different when there were crossbeams in the anchorage zone or not, but it corresponded with the results got from the full-scale model test that crossbeams only endured 7.7% of the tension stress in all. Considering the strength loading, construction convenience and other factors, crossbeam should be cancelled, which has been adopted in the practice construction and played an important role to optimize designing of the main tower structure.
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