Study On Horizontal Mechanical Properties Of Core Concrete Cable Tower Anchorage Structure

The cable tower anchorage structure of cable-stayed bridge is an important structure that transmits the strong cable force to the cable tower and then to the foundation.It has the characteristics of large load,complex structure and diverse force transmission paths.If the design is improper,it will directly affect the safety and normal use of the structure.The existing cable tower anchorage structure can no longer bear the super-high cable force of 1200 m cablestayed bridge in the force transmission mechanism.In this paper,a new type of core concrete cable tower anchorage structure suitable for ultra-high cable force is proposed.The structure is that the stay cables on both sides of the bridge tower are staggered anchored on the core concrete covered with steel siding,which makes full use of the compressive capacity of concrete and the tensile capacity of steel plate,and reduces the risk of cable tower cracking.Based on the combination of experimental research,theoretical analysis and numerical simulation,this paper studies the force transfer mechanism,failure mode and design method of the horizontal mechanical properties of the new core concrete cable tower anchorage structure.In order to explore the mechanical properties of core concrete cable tower anchorage structure,10 scale models are designed to study the effects of stirrup ratio,reinforcement ratio and shear span ratio on the properties of anchorage structure.The test shows that the anchorage structure of core concrete cable tower has good bearing capacity and can meet the anchorage requirements of super large cable force.Under the action of the horizontal force of the cable,the anchorage structure presents the stress state of the classic tension and compression bar.When it is damaged,the wrapped steel plate yields and the core concrete in the diagonal compression bar area is compressed and damaged.According to the tension compression bar theory and the experimental failure mode,the mechanical behavior of the cable of the new anchorage structure under the action of horizontal force is revealed,and the calculation formula of the shear bearing capacity of the core concrete cable tower anchorage structure is put forward.Based on the above research,the specific conclusions are as follows:(1)the shear span ratio is the main factor affecting the bearing capacity.Reducing the shear span ratio can significantly improve the ultimate bearing capacity of core concrete;(2)The reinforcement ratio of horizontal reinforcement in the web of beam is another factor affecting the bearing capacity.The horizontal reinforcement in the web of beam passes through the oblique crack in the diagonal compression bar area,which has a strong restraining effect on the concrete in the diagonal compression bar area,and can improve the bearing capacity and ductility of the structure in the event of diagonal compression failure,and the effect is more obvious in the specimens with small shear span ratio;(3)Because the failure mode of the new anchor structure is oblique compression failure and wrapped in strong steel plates,it only improves the reinforcement ratio of the structure,which has little effect on the ultimate bearing capacity of the structure;(4)Due to the existence of steel plate,the contribution rate of transverse reinforcement to ultimate bearing capacity is not high,which can be appropriately reduced in design.Combined with the test and finite element analysis,the stress characteristics of the new anchorage structure are determined,the influence of horizontal reinforcement and cable conduit on the structure is clarified,and the reason of hollowing phenomenon in the test process is explained.Finally,based on the analysis of the failure mode and force transfer mechanism of the test beam,the calculation formula of the shear bearing capacity of the new structure is proposed.The effectiveness and accuracy of the formula are verified by comparing the calculated value of the formula with the test value.The above research results can provide some references for the engineering application of this core concrete cable tower anchorage structure and some research.