Study on Anti-cracking Technology for Post-tensioned Precast Panel in Negative Moment Zone of Composite Girders
For bridges with spans less than 50 m,the use of strong reinforcement can well meet the requirements of anti-cracking performance,but for composite girder bridges with long spans,the use of strong reinforcement cannot well meet the needs of anti-cracking alone.In order to improve the cracking resistance of bridge panels in negative bending moment zone of 50-80 m continuous composite girder bridge and realize the construction of bridge panels in negative bending moment zone,a modular prestressed precast panel with different cracking resistance is proposed.First of all,3 types of precast panels suitable for rapid construction in negative bending moment area are designed,among which Class A is the ordinary precast panel in the middle position,Class B is the anchor panel with tooth block,and Class C is the end anchor plate.According to the actual stress situation,the number and length of the 3 types of precast panels are combined to meet the needs of anti-cracking.Secondly,combined with the design specification and numerical simulation,the internal force,stress,deflection and anti-cracking performance of the bridge structure by using anti-cracking technology are checked to verify the feasibility.Finally,it is further extended to the composite girder bridge with medium span of 50-80 m and 1.5-1.7 side to span ratio,and MIDAS is used to check the structural crack resistance and applicability analysis.The result shows that(1)the post-tensioned prestressed precast panel anti-cracking technology can realize that no tensile stress occurs in the flange stress of precast panel with the combination of long and short term,that meets the anti-cracking requirements of Class A members in the specifications;(2)the precast panels with a curing period of 6 months have an obvious effect on reducing the creep effect with a reduction of about 48%,which can meet the requirements of the bridge panel crack resistance and steel box girder strength control specifications for 50-80 m main span composite girder bridges;(3)when the negative bending moment precast panel is used,the length range of the negative bending moment is slightly reduced compared with the standard calculation result,and the standard partial safety calculation can still be used.
bridge engineeringpost-tensioned precast panel technologyfinite element calculationcomposite beamsshrinkage and creep
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