The Research About Stiffness Gradient For Widening Technology Of Hollow Plate Bridge Of Highway

Fabricated hollow slab bridge is a kind of common type in bridge engineering because of its advantages of simple structure, easy construction, low cost and so on. With the rapid economic development of China and the great increase of car ownership and traffic volume, the capacity of the original few-lane highway can't meet present requirement any longer and is needed to be widened and reconstructed. The fabricated hollow slab bridge, as the main bridge type of highway, will be the emphasis of the bridge widening project. How to assure the normal working between the old and new junction and how to assure the integrity of bridge deck pavement will be the pivot of the project.In this paper, the great rigidity difference between the old and new slab was the research focus. The rigidity difference between the old and new slab achieves equal graduation and expand the change area, and thus achieves the change from the rigidity saltation between old and new slab into multi-slabs gradual change. Therefore, the displacement difference and accessory stress will be greatly decreased into the permissible range of structural element, and hence the integrity of bridge deck pavement can be achieved. Moreover, we researched for the rigidity saltation technology of hollow slab bridge widening engineering, taking the widening project of Cang paragraphs Henan Bridge as engineering instance, which is a segment of Beijing, Hong and Macao expressway from Xinxiang to Anyang. The following shows the accomplished work and corresponding conclusions:(1) The rigidity of hollow veneers used in the old and new bridge was checked. The calculation results show that the rigidity of veneers used in new bridge and the old bridge exhibited great difference, which could result in bridge deck damage at junction after joining of old and new slabs. Based on that, the rigidity gradient of old and new slabs was proposed and identified.(2) Two rigidity gradient theoretical calculation models on widening hollow slab bridge were proposed. Based on that, we calculated and educed the initial rigidity gradient project of old and new slabs and the initial assign position, shape, size and materials of the lateral rigidity gradient components.(3) The analysis of static mechanical properties of rigidity gradient hollow slabs was carried out. The results show that the displacement on transition region exhibited great difference before and after using lateral rigidity gradient components:before that, there was significant rigidity saltation between old and new slabs, and hence displacement saltation; while after that, the displacement of each bridge deck exhibited the trend of gradual change. Furthermore, the load transverse distribution coefficient of hollow slabs that absorbed load stocked up significantly before using lateral rigidity gradient components, i.e. it is significant for single beam bearing; whenas after that, the salience value of load transverse distribution coefficient of hollow slabs decreased and the salience width increased, which illustrated that the concentrated loads were bore by multi slabs. The comparison of static mechanical properties before and after using lateral rigidity gradient components proved that the gradient effect was excellent, and proved the effectiveness of lateral rigidity gradient components.(4) The dynamic response analysis of hollow slab bridge applying rigidity gradient model was carried out. The calculation results show that:before using lateral rigidity gradient components, the span dynamic displacement of the bridge slab that enduring moving load presented displacement saltation, comparing with adjacent slabs; while after using that, its span dynamic displacement reduced by 50% and similar with that of the adjacent slabs. In addition, before using lateral rigidity gradient components, the time of arrived to the maximum of span dynamic displacement of each bridge slab exhibited some difference, which proved that there was non synchronous vibration phenomenon, and it could result in damage at match-concrete joints because of non synchronous vibration of bridge slabs during use of the bridge; after using that, the coordination of vibration displacement during slabs enhanced greatly, and the time up to the maximum displacement nearly consistent. The dynamic response analysis also proved the effectiveness and necessity of using lateral rigidity gradient components.(5) The channel sections and bolts of lateral rigidity gradient components easily appeared concentration during working. The analysis in details shows that the bolts presented stress concentration, and the tress value was larger than that of the channel sections significantly. When choosing bolts, it is better to choice the high-strength bolt and increases its diameter to assure that there is enough safety reliability, because that the slot is the weakness during the lateral rigidity gradient components working. So the local stress of both the selected slots and channel sections were within the scope of materials to withstand.(6)Finally, the specific measures and Construction project of rigidity gradient of hollow slabs were identified.