Analysis And Research Of Key Temporary Structures In Cantilever Construction Of PC Continuous Beam

In recent years,China has achieved remarkable achievements in the field of bridge construction.Among them,PC continuous beam bridges have been widely used and promoted due to their excellent structural performance,with cantilever construction being the main construction method for PC continuous beam bridges.Currently,there are several issues in the construction process of cantilever beam bridges.Firstly,the simplified model of the temporary joint between the pier and the beam is not accurate enough,and the influence of the temporary joint on the internal force and deflection of the main beam is not fully considered.Secondly,it is easy for the hanging basket to overturn during the pouring of concrete for the cantilever,and the force on the beam and suspension rod in the hanging basket is also likely to be unbalanced.Additionally,the impact of the structure is not clear when the cantilever is constructed using a hanging basket equipped with beam bottom protection.Finally,the degree and scope of the impact of the reaction force on the rear anchorage beam after hanging the basket are also unclear.Therefore,it is particularly important to study these issues.By researching these issues and adopting a reasonable optimization plan to solve the problems in the construction process of cantilever beam bridges,construction quality can be improved,and construction safety can be ensured.This article analyzes the stress situation of the temporary fixation of pier-beam and the hanging basket structure during the construction process of a prestressed concrete continuous box girder bridge.The causes of unbalanced loads and the calculation methods of unbalanced bending moments are discussed.Based on this,the calculation formulas of the double support point model and the three support point model of the pier-beam temporary fixation structure are summarized and verified for their correctness.The suitability of the diamond-shaped hanging basket in cantilever hanging basket pouring construction is assessed through finite element software MIDAS/Civil.The correctness of the model is verified by establishing a full-bridge truss model and a detailed solid model,and combining with on-site measured stress data.Finally,the influence of different pier-beam temporary fixation methods,structures,and protected hanging baskets and hanging basket anchorages on the structure is explored through the establishment of finite element local solid models.The conclusion drawn from this article is as follows:(1)The use of a three-point calculation model in the temporary fixation calculation of the pier-beam can better reflect the actual stress characteristics of the structure.(2)The change in the position of temporary supports has little effect on the main beam structure.Two methods,namely temporary fixing inside the pier and temporary fixing at the pier corner,have little impact on the internal forces and displacements of the main beam structure.(3)With the protective netting structure in place,the compressive stresses on the top edge of the pier’s top cross-section increase,and there is also a significant increase in longitudinal and transverse compressive stresses along the bottom edge of the bottom cross-section.During construction,the suspended protective netting also has some impact on the deformation of the main beam.(4)The tensile stress on the top plate exhibits an obvious stress concentration phenomenon at the location where the load is applied by the rear anchorage and the front support point.Based on the results of the aforementioned research,the weight optimization of construction schemes was carried out.Linear data collection for the "Ning luo Bridge" was conducted to verify the weight distribution plan,providing a reference for future construction of similar bridge structures.