Experimental Study On The Flexural Behavior Of Reinforced Concrete Beam Strengthened With Bolted Side Steel Plate And Its Design Methods

Because of the Strengthening structure in the practice, when the bottom beam with obstructions can not be reinforced bottom, a new type of reinforcement technology is proposed in this paper, the technique of strengthening RC structure by bolting steel plates on the side, which is steel plates are fixed by anchors to the face of RC structure, which makes beam and steel plates change into one structure system to bear load simultaneously. Because of anchor with good shear and pull-out performance, this strength technique avoids desquamation of bonded steel plate effectively, and has a very good strengthening effectiveness to improve the bearing capacity and stiffness of the beam. At present, the reported on the experimental and theoretical of which is still a few in home and foreign, and the study is not only no-depth but also with no systems. To that end, design methods based on the norms of our country bending design is proposed by experimental study on the flexural behavior of reinforced concrete beam strengthened with bolted side steel plate. Research results not only for the application can provide a basis, but also help to improve academic research of reinforced concrete beam strengthened with bolted side steel plate and the preparation of the norms.Five strengthened beams are designed and the influence of the strengthening effectiveness (to the development of cracks, stiffness, ultimate strength, failure mode, etc.)by rigidity of anchor pitch , highth of steel plate and loading / unloading is defined. Based on the experimental study on the flexural behavior of reinforced concrete beam strengthened with bolted side steel plate and proposed its design methodsIn this paper, by the experimental study and theoretical analysis, the main conclusions are given as follows:The first,experimental study on the flexural behavior of reinforced concrete beam strengthened with bolted side steel plate1) Rigidity of beams of static load by bolting steel plates through contrasting experiment, the limit bearing capacity of several strengthened beams are increased about twice,and stiffness also improved more. Concentrated load in the department of the corresponding beam bottom and the vicinity of Anchor at side of the beam, cracks have appeared. The cracks of the vicinity of Anchor is more serious at the abdomen than at the bottom of the beam strengthened,and the end than midspan, as a result of the fina l failure are the end section cracks of the beam strengthened too wide and are destructed because of the shear capability.2) Comparing reinforcement effective with different high steel of the beam strengthened: when it is cracked the load is basically the same; the higher plate, the greater stiffness, the more fine cracks, to the development of cracks more slowly; the higher ultimate strength, but the increase marginally; the phenomenon which steel and bottom bars of Strain is not synchronized is the more obvious, but the destruction patterns of the beam strengthened is the same, both ends of shear failure.3) Comparing reinforcement effective with different Anchor pitch: the smaller pitch, the greater stiffness, but improvement range is unapparent, both the yield load and deflection of the damage are basically the same, as the cracking-load also is increased slightly; The greater ultimate bearing capability, but to increases the range is marginally (15%), when the beam strengthened are destructed, the cracks are larger, and lead to ends of the shear failure.4) Comparing reinforcement effective with different loading / unloading: the former pre-stiffness is greater, but the latter improvement is not obvious; the latter pre-stiffness is small, but improvement range in the latter part than the former. When the beam strengthened is destroyed , the former deflection is more small than the latter, Cracking-load is the same, which cracks continued a longer time and faster than the former, and the ultimate bearing capacity is also bigger, but only with not significant improvement (about 10%); destruction model is the same, ends of the shear failure.The second,based on the experimental and theoretical analysis,design methods is given on the flexural behavior of reinforced concrete beam strengthened with bolted side steel plateBased on test and theory analysis, the design formula of flexural strengthening RC beams by bolting steel plates is given in this paper and the result indicates that the formula provides a good reliability.The third,the design and construction proposals of anchor on the flexural behavior of reinforced concrete beam strengthened with bolted side steel plate. Beginning with Anchor material request and damage model, baseing on the principle of the anchor work and the capacity factors, and the experimental study ,analysis model is given, and the corresponding method of calculating is given in different reinforcement ways under the ( different anchor rank number and the plate highth), the final Construction proposals is brought up.