某变截面连续钢-混叠合梁负弯矩区桥面板顶升抗裂措施的应用研究

Research on Application of Anti-cracking Measures for Bridge Deck Jacking in Negative Bending Moment Zone of Variable Cross-section Continuous Steel-concrete Composite Beam

鄞州大道跨南塘河节点采用35 m+70 m+35 m变截面连续钢-混叠合梁。鉴于此种梁桥中支点附近的负弯矩区桥面板容易开裂,采用了支点先同步顶升再回落的施工工艺,以使桥面板获得足够的压应力储备,提高桥面板的抗裂性能。为了确保工程质量和施工安全,采用MIDAS Civil有限元软件建立桥梁有限元模型,以模拟中支点先顶升再回落的施工过程,并通过比较来确定中支点合理的顶升高度。计算结果表明:中支点合理顶升高度为40 cm,在频遇工况下,负弯矩区混凝土桥面板受压且不出现裂缝,端支座最小反力为188.1 kN(不出现支座脱空),可以满足变截面连续钢-混叠合梁桥面板的抗裂要求。

The(35+70+35)m variable cross-section continuous steel-concrete composite beam is used for Yinzhou Avenue across Nantang River.Due to the bridge deck easily cracked in the hogging moment area near the central bearing point of this bridge,the construction process of fulcrum jacking synchronously first and then falling back is adopted to make the bridge deck obtain the sufficient compressive stress reserve and improve the anti-crack performance of bridge deck.In order to ensure the engineering quality and construction safety,a finite element model of the bridge is established by using MIDAS Civil finite element software to simulate the construction process of the central bearing point jacking first and then falling back.And through the comparison,the reasonable jacking height of the central bearing point is determined.The calculation results show that the reasonable jacking height of central bearing point is 40 cm.The concrete bridge deck in the hogging moment area is compressed without the cracks under the frequent conditions.The minimum reaction force of the end support is 188.1 kN(without the support separation),which can meet the anti-crack requirements of variable cross-section continuous steel-concrete composite beam bridge deck.