Experimental and Analytical Study of Strengthening Reinforced Concrete Beams with Openings

摘要

The present study describes the result of an experimental investigation on the response of creating opening in reinforced concrete beams after and before casting using steel wire mesh, steel angles, steel straps, steel stirrups system and reinforcement beams around the opening. The beams were instrumented and tested under two-point load. The experimental program consisted of testing thirteen simply supported reinforced rectangular beams. The main parameters of study are the different methods of strengthening. The deflection, strain, failure load, failure mode and stiffness of the strengthened beams are discussed. A nonlinear finite element method NFEM analyses (Ansys15 program) was used to corroborate the results from the experimental study. Test results indicates that the best, simple and cheap technique of strengthening by recording an increase in the load capacity of 8.95% is that strengthened by using four steel stirrups as rectangular shape with diameter 8mm and steel rods with 8mm which also gives an decrease in deflection and an increase in stiffness. The beam strengthened by reinforced beams around the opening, gives an increase in the load carrying capacity of 2.8% of the control ultimate capacity. However, beams strengthened by two numbers of steel wire mesh, steel bars like box with diameter 8 mm and reinforced beams at upper and lower of the opening, gives an increase in the load carrying capacity of 1.6% of the control ultimate capacity. For the beam strengthened after casting an increase was obtained in the load capacity by 3.77% for the specimen that strengthened by using four layers of steel wire mesh, steel strip system, steel angles and clamps. The analytical results are compared with the data obtained from beam tests up to failure. Faire agreement was found between the FEA results and EXP results.