Experimental Study On Shear Behavior Of Reinforced Concrete Beams With Combined Aggregate

Faced with the increasingly serious ecological problems and the depletion of natural aggregates,the research and utilization of recycled concrete gradually show its importance.In recent years,great progress has been made in the research of the basic mechanical properties of recycled aggregates and recycled concrete,and due to the complexity of structural problems,there are few researches on the structure of recycled concrete.In the existing research,most of the scholars take the concrete components,in which the natural coarse aggregate is replaced by the recycled coarse aggregate,as the research object.In order to maximize the use of recycled aggregates,the shear behavior of concrete beams mixed with 14 large-size natural aggregates and small-diameter recycled aggregates was researched in this article,and it also analyze the influence of some factors,such as shear-span ratio and concrete strength,on the shear cracking load,the stirrup strain in the bending and shear zone,the concrete strain in the shear zone,the width of the main oblique crack at the intersection with the stirrup and the shear capacity.By comparing the test results with the calculated results of the formula of crack load and the formula of shear strength for the ordinary section of reinforced concrete beam,the applicability of ordinary reinforced concrete formulas to reinforced concrete beams with combined aggregate was verified.Mainly draw the following conclusions:(1)The failure mode of the reinforced concrete beams with combined aggregate are similar to the ordinary reinforced concrete beams.It is represented as baroclinic failure when the shear span ratio is 1,and it occurs shear failure when the shear span ratio is 1.5,2.0,and 3.(2)Under the same concrete strength grade,the crack load and the shear strength of the test beam are reduced with the increase of shear-span ratio.Under the same shear span ratio,the crack load and the shear strength of the test beam are increased with the increase of concrete strength.(3)When the concrete strength grade is C40,under the same load,the stirrups strain at the intersection with diagonal cracks are increased with the increase of shear span ratio.When the shear-span ratio is 2,under the same load,the stirrups strain at the intersection with diagonal cracks are decreased with the increase of the concrete strength grade.(4)Under the same concrete strength level,when the diagonal crack width at the intersection with the stirrup is a certain value,the corresponding load of the test beam decreases with the increase of the shear span ratio.Under the same shear span ratio,when the diagonal crack width at the intersection with the stirrup is a certain value,the corresponding load of the test beam increases with the strength grade of the concrete.(5)The existing statistical formula for the crack load of ordinary reinforced concrete beams are no longer applicable to the reinforced concrete beams with combined aggregates,and the results are unsafe.The calculated value of shear capacity formula in(GB50010-2010)has the best agreement with the experimental values,and it is also suitable for predicting the shear capacity of reinforced concrete beams with combined aggregates.