台背回填与桥头跳车施工技术

随着我国经济的快速发展,公路建设的速度也突飞猛进,而公路的施工技术也随之有所提高,人们对行车的安全舒适度也要求的越来越高。但是现在存在着桥头的跳车问题,是影响行驶的一大问题,也是现在大多数的公路普遍存在的问题。如何解决这一通病,是现代的施工单位需要解决的问题,以下将结合本人多年从事公路施工的经验,浅谈一下控制桥头跳车的施工技术与控制措施。

浅谈台背回填与桥头跳车施工技术

随着我国公路建设的快速发展,汽车行使速度的提高,对行车舒适要求也越来越高,但桥头跳车问题却是公路的通病,根据公路施工的经验,从施工技术的角度,浅谈桥涵台背回填与桥头跳车的施工与控制措施。

Construction techniques of super-length main cable of Taizhou Bridge

Taizhou Bridge is a highway three-pylon two-span bridge with span arrangement of 1 080 m + 1 080 m and the length of the main cable is more than 3 100 m. It is the longest cable in China. As the erection of the main cable needs to cross over three towers and the cables undulate acutely, general problems like the twist, spread and swell of strands and shedding of the zinc coating are prone to arise, which make it difficult to guarantee the quantity of cable traction construction. In this paper, the hauling, shaping and saddling of strands and sag adjusting are illustrated in detail and how to execute the refined construction control to guarantee the erection quality is also covered.

Stone Columns and Tensioned Anchors to Completely Eliminate Tunnels Trough Settlements

The complex tunnelling constructive environment in urban area in similar green field situations is faced through analytical evaluations in order to control the design calculation process and subsequently manage the interventions techniques with the aim of totally reducing the typical settlements trough above the tunnel either during the construction stage or during the serviceability stage. Recently, the author has proposed an operative and mathematical method by an opportune choice of tensioned anchors to control the tunnel lining settlements. In order to completely eliminate the remainder typical soft soil trough which is normal to the line of the tunnel, it is here proposed to use and properly calculate the interventions of stone columns by the SAVE （silent, advanced, vibration-erasing） Compozer method, in combination with the anchorages.

Refined analysis and construction parameter calculation for full-span erection of the continuous steel box girder bridge with long cantilevers

To accurately control the full-span erection of continuous steel box girder bridges with complex cross-sections and long cantilevers, both the augmented finite element method(A-FEM) and the degenerated plate elements are adopted in this paper. The entire construction process is simulated by the A-FEM with the mesh-separation-based approximation technique, while the degenerated plate elements are constructed based on 3D isoparametric elements, making it suitable for analysis of a thin-walled structure. This method significantly improves computational efficiency by avoiding numerous degrees of freedom(DoFs) when analyzing complex structures. With characteristics of the full-span erection technology, the end-face angle of adjacent girder segments, the preset distance of girder segments from the design position, and the temperature difference are selected as control parameters, and they are calculated through the structural response of each construction stage. Engineering practice shows that the calculation accuracy of A-FEM is verified by field-measured results. It can be applied rapidly and effectively to evaluate the matching state of girder segments and the stress state of bearings as well as the thermal effect during full-span erection.

Control measures for thermal effects during placement of span-scale girder segments on continuous steel box girder bridges

In this study, we examined the thermal effects throughout the process of the placement of span-scale girder segments on a 6×110-m continuous steel box girder in the Hong Kong-Zhuhai-Macao Bridge. Firstly, when a span-scale girder segment is temporarily stored in the open air, temperature gradients will significantly increase the maximum reaction force on temporary supports and cause local buckling at the bottom of the girder segment. Secondly, due to the temperature difference of the girder segments before and after girth-welding, some residual thermal deflections will appear on the girder segments because the boundary conditions of the structure are changed by the girth-welding. Thirdly, the thermal expansion and thermal bending of girder segments will cause movement and rotation of bearings, which must be considered in setting bearings. We propose control measures for these problems based on finite element method simulation with field-measured temperatures. The local buckling during open-air storage can be avoided by reasonably determining the appropriate positions of temporary supports using analysis of overall and local stresses. The residual thermal deflections can be overcome by performing girth-welding during a period when the vertical temperature difference of the girder is within 1 °C, such as after 22:00. Some formulas are proposed to determine the pre-set distances for bearings, in which the movement and rotation of the bearings due to dead loads and thermal loads are considered. Finally, the feasibility of these control measures in the placement of span-scale girder segments on a real continuous girder was verified: no local buckling was observed during open-air storage;the residual thermal deflections after girth-welding were controlled within 5 mm and the residual pre-set distances of bearings when the whole continuous girder reached its design state were controlled within 20 mm.