Experimental Study On Flexural Properties Of R.C.Beams Strengthened By Welding Steel Bar To Embedded Anchors

The paper presents a new technique of strengthening RC beams by welding steel bar to the anchor belt embedded in concrete, which makes beam and steel bar change into one structure system to bear load simultaneously. With this method, tensile reinforcement area of the positive cross-section increased effectively. Which is increase the cross section of concrete beam reinforcement area efficiently. This mothod set up adhesive anchors on the surface of concrete beams, which is make the addition of steel bar and concrete beam becomes a new joint fore system by welding the addition of steel bar at the end of anchor belt. The original reinforcement method of welding up strengthed bar need to chiseling concrete at the end of the beam and tie the reinforcing steel bar to the build-in steel bars by means of welding, which is cause a certain degree of damage to the beam and reduce the coefficient of utilization of the build-in steel bars. The reported technique in the present work overcomes the drawbacks of the above method with minimized damage by using the technique of plantting, which can coordinate stress with the original member, and enhanced the flexural capacity effectively. The proposed technique of welding steel bar to the anchor belt embedded in concrete has many advantages, such as simple and speedy execution, minimal disruption during installation, involve less costly materials, less surface preparation, negligible increase in the self-weight and no appreciable reduction in headroom. Thus, the reinforcement technology has a wide prospect of engineering application in structural strengthening of the medium and small span beam bridge.In order to study the influence of design parameters, including quantity of Reinforcing Steel and planting rebar spacing and quantity of anchor belt, five rectangular beams strengthened by means of welding steel bar to the anchor belt embedded in concrete and one reference beams were tested. By analyzing the carrying capacity, deflection, rigidity and cracking of the tested beams, the influence of the strengthening effectiveness is defined. Progress has been made in the following areas:(1) On the basis of mechanics principle of bridge reinforcement,the reinforcement methods of girder bridge upper structure were summarized,and a new technique of strengthening RC beam was proposed according to welding up steel original method improved combined with post installed anchorage technology, which name is anchor belt welding steel bar reinforcement method;(2) Through theoretical analysis of strengthened RC beams, it is considered that the performance of anchor being the critical factor to the strengthening effectiveness. Therefore, the mechanics mechanisms and calculation method of anchor bolt are discussed attentively, and the failure characteristics of anchor are generalized comprehensively;(3) The experimental result showed that the beams strengthed by the new technique this paper prosed improves not only the flexural capacity, but also enhances the crack resistance and raises the capability of resistance to deflection;(4) Stressing characteristics were studied through contrasting experiment of five test beams, and influence of the strengthening effectiveness were discussed for various parameters which had different effect on bearing capacity.crack initiation and stiffness of strengthening beams;(5) With the theoretical analysis of RC beams, this thesis propose the brief formulas of strengthening beams to calculate the flexural bearing capacity, which has a high calculation accuracy in comparison with the results of the experiment;(6) The deflection and crack of strengthening beams were checked according to the coefficient revised formulas of the deflection and the maximum crack width under short-date loading. Compared the calculation of the formulas with the experimental results, it judges the formulas is propitious to actual engineering.