Shear Behavior Of Reinforced Concrete Beams Strengthened With Aluminum Alloy Sheets

With the rapid development of the economy and society,and the renewal of the relevant design codes as well,the buildings constructed previously have become increasingly unable to meet people's needs in life and work in terms of safety,applicability and durability.If a large number of defective buildings are demolished and rebuilt directly,it will not only take a lot of time and money,the basic state policy of protecting the environment is not responded effectively.In order to improve the bearing capacity and service life of these buildings,the technology of concrete structure reinforcement has been acceptable increasingly.At present,most of the reinforcement materials used are steel plate and FRP,but steel plate is easy to be corroded.FRP is a kind of brittle material,and there is no sign of destruction.Aluminum alloy has some typical advantages,such as lightweight,the surface of aluminum will form a dense oxide film when exposed to air,and not easy to rust and so on.At present,the reinforcement of concrete beams is mainly bending and shearing.Shear failure of concrete beams is a kind of brittle failure without warning,which will pose a great threat to people's lives and property.Considering the superiority of aluminum alloy and the urgency of shear strengthening,it is necessary to study the shear strengthening of concrete beams with aluminum alloy.In this paper,the relevant mechanical properties of aluminum alloy,steel and concrete used in the design beam were tested.At the same time,and the design of the size and reinforcement of the test beam has been completed.Firstly,a single shear test is carried out on the bonding properties of between aluminum alloy and concrete,determined the bond-slip relationship between aluminum alloy and concrete,and then carried out an experiment of four-point bending on concrete beams with different reinforcement forms and damage degrees.In the performance test,the shear capacity of concrete beams strengthened by different forms is improved to different extents.The method of U-shaped pressure strips achieves the greatest improvement in the shear capacity of concrete beams,followed by the45-degree side-bonded aluminum alloy,U-shapedPaste,and side vertical paste.In terms of operability and economy,the method of 45 ° side paste is more desirable.For different damage degree ofconcrete beam,with the aggravation of damage,the strengthening effect of aluminum alloy is less.According to the material performance parameters obtained from the relevant experiments,the three-dimensional finite element model of the aluminum alloy shear-reinforced concrete beam was established by the finite element software ABAQUS.The cohesive force unit was used to consider the bonding layer between the aluminum alloy and the concrete.The load-displacement curve obtained from simulation is in good agreement with the test results.At the same time,the relationship between shear reinforcement effect of aluminum alloy and stirrup spacing,shear span ratio is studied by simulation.With the same reinforcement method,the shear reinforcement effect shows a better trend with the increase of stirrup spacing and shear span ratio.Based on the test and the relevant specifications of the bonded steel,it is considered that the shearing reinforcement effect of the aluminum alloy is not only related to the damage degree of the beam,but also related to the amount of the aluminum alloy adhered in the horizontal projection range of the oblique section when the beam is broken.A theoretical calculation model for concrete beams strengthened by aluminum alloy is proposed.The corresponding reduction coefficient of concrete beams strengthened by aluminum alloy is suggested by regression fitting.