公铁两用钢桁梁铁路桥伸缩纵梁节点板更换施工

Replacement Construction of Gusset Plates at Adjustable Stringers for Rail-cum-Road Steel Truss Girder Bridge

枝城长江大桥主桥为(4×160+5×128)m公铁两用连续钢桁梁桥,主桥钢桁梁为"米"字桁。运营40余年后检查发现主桥铁路桥伸缩纵梁处连接竖向拉板的节点板出现裂缝(共4处)。为确保桥梁结构和列车行车安全,通过对伸缩纵梁处节点板断裂病害进行分析,在保证铁路运输交通安全的前提下,对断裂的节点板、角钢、拉板进行更换。节点板更换工艺为先将连接螺栓解除,拆除原节点板的连接杆件和连接板(先拆除次要连接杆件,后拆除主要连接杆件),然后对旧连接孔及杆件接触面进行相应处理;安装新杆件的顺序为拆除顺序的逆过程(先安装主要连接杆件和节点,再安装次要节点)。结构分析表明,更换后伸缩纵梁结构的整体受力性能加强,能够满足铁路桥梁伸缩变形的要求。该桥利用铁路维修天窗点进行杆件更换,整个施工未对营业线的安全造成影响。

T he main bridge of Zhicheng Changjiang River Bridge is a railcumroad continuous steel truss girder bridge with span arrangement of （4× 160＋5× 128） m .The steel truss girder of the main bridge adopts the type of steel truss like Chinese character “米” .After serving for more than 40 years ,the gusset plates at the adjustable stringers w hich connect the vertical tensile plates in the main railway bridge have cracks （a total of 4 locations with cracks） .To ensure the bridge structure and the train riding safety ,based on the analysis of the fracture deterioration of the gusset plates at the adjustable stringers ,and on the premise that the railway transportation safety is ensured ,the failed gusset plates ,angle steel and tensile plates were replaced .The replacing technique for the gusset plates starts from the removal of the connecting bolts and the demolition of the connecting chords and plates of the original gusset plates （dismantling the subsidiary connecting chords first and the main connecting chords later） .Then ,the contact surfaces of the original connecting holes and the chords were treated .The installation of the new chords follows the reversed procedure of the demolition （installing the main connecting chords and gusset plates first and the subsidiary gusset plates later） .The results of the structural analysis indicate that the overall load bearing capacity of the adjustable stringers is strengthened ,which can meet the demands of the contraction and extension deformation of the railway bridge .The replacements of the components were carried out during the railway maintenance duration ,and the whole construction exerts no influence on the safety of the railways in service .