ã€Abstract 】 In this paper, the mechanical properties test of the cross joint of the Zhanjiang Bay Bridge anchorage plate is studied. The stress state of the weld of the cross joint, the influence on the mechanical properties of the joint and its application in the manufacture of bridge steel structure are introduced.
First, the project brief
In October 2004, our company won the bid for the steel structure manufacturing project of Zhanjiang Bay Bridge. The length of the steel box girder of the main bridge is 716. 4m. The structure of the bridge is shown in Figure 1. The top surface of the box girder is 28. 5 m, the bottom is a radius of 72. 5 m, the height of the bridge center line is 3.0 m, and the cross section of the steel box girder is shown in Fig. 2.
There are two major characteristics in the manufacture of the box girder of the bridge: one is to set two inner webs between the two outer webs, with a spacing of 9. 8 m, except for the section with large internal force and the joints, which are solid webs, and the rest are Fasting structure. The inner web can strengthen the rigidity of the box girder, reduce the shear hysteresis, and ensure the geometry of the cross section and the accurate positioning of the steel beam segments during the manufacture of the steel beam: Second, the cable stays on the steel beam. For the first time, the anchoring structure of the anchor plate is adopted (see Figure 3). The anchor plate is welded to the top surface of the box girder above the outer web of the main beam, and is divided into upper, middle and lower parts. The anchor pipe is embedded in the middle of the upper part of the anchor plate. The two sides are welded with the anchor plate on both sides, and the lower part is directly welded to the bridge deck. In addition to the installation of the anchor in the middle, the upper and lower parts need to be connected. In order to compensate for the weakening of the cross section of the anchor plate and the lateral rigidity of the hole, the reinforcing plate is welded on both sides of the plate and connected with the bridge deck. This anchoring method has clear transmission path, simple structure and construction work on the site. Convenient, and the upper and lower fillet welds of the deck form a typical cross joint weld that directly transmits tensile stress.
In this joint form, the cross weld and the bridge deck are sharply transitioned, and the joint is twisted greatly under the action of external force, resulting in extremely uneven stress distribution, and the load stress and weld residual stress concentration at the weld are large. When there is a defect in the root or transition, fatigue fracture occurs due to long-term fatigue stress. According to the design, the weld seam of the weld is made of penetration fillet weld. The stress in the weld of the anchor pull plate under the axial tension is mainly normal stress, which can greatly improve the joint strength. The axial force acting on the anchor plate is transmitted directly from the groove weld to the deck. Therefore, there is a high requirement for the material of the deck and the mechanical properties of the plate thickness: and the cross joint weld is on the bridge. The steel structure anchor plate is welded for the first time, which brings certain difficulties to the welding production of our company's steel bridge. To this end, we have carried out a series of welding procedure qualification tests on the cross joint weld. The internal quality and mechanical properties of the joint can meet the design requirements, which can be used to guide the penetration of the fillet weld of the steel box girder of the bridge. Welding production.
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