Research On Compressive Performance And Bearing Capacity Of RC Short Columns Strengthened With Circular Steel Jacketing

The circular steel jacketing (CSJ) is causing widespread concerns in the field of civil engineering reinforcement, because of its strong grasping, wonderful mechanical property, and fast-convienient construction. As well known, it is always got mixed with steel tube reinforced concrete (STRC). In fact, CSJRC is quite different from STRC in the aspect of mechanical property. There’s few literature about CSJRC column by today, and the reinforcement calculation is far away from satisfactory. This thesis is developed considering the current status in this field, and divides into eight main topics:1. The working mechanism of strengthened axial compressed strenthened short columns is thoroughly studied by failure experiments of axial compressed strengthened short columns. The influence of different design parameters on the mechanical behaviour and load bearing capacity are given by changing the thickness of strengthened steel jacketing and initial stress.2. The nonlinear finite element analysis of mechanical property and working mechanism has been done for axial compressed strengthened speciments. Then speciments is studied in depth by above simulation method to obtain influence of initial stress on the bearing capacity of strengthened axial compressed columns and the paper compared with the bearing capacity and the change rule of the stress and the strain of the first forced strengthed short column and the second forced short column.3. The paper exponds four common constitutive relations of confined concrete, then compares with the strengthened column loading capacity result of experiment and calculation given by above four constitutive relations with FEM method. Finally, chooses the best constitutive relation of confined concrete to lay the foundation for the later calculation.4. According to the working mechanism of strengthened short column, the loading transmission length of the interface of new and old concrete and loading condition are proposed firstly, then the paper puts forward the modifier formulars of hoop stress and vertical stress of steel jacketing, deduces the loading calculating method of strengthened short column considering the shear and lateral deformation by the result of experiment and analysis of the strengthened short columns. At last, the loading calculating method considering the initial stress is deduced after putting forward the conception of the critical stress.5. The working mechanism of eccentric compressed strenthened short columns is thoroughly studied by failure experiments of eccentric compressed strengthened short columns. The influence of different design parameters on the mechanical behaviour and load bearing capacity are given by changing the thickness of strengthened steel jacketing and offset distance.6. According to the experiment of eccentric compressed strenthened short columns and computational method of concrete filled steel tube, the paper proposes the concept of equivalent hoop stess considering the lateral deformation and shear deformation of jacketing, At the same time, considering initial stress, get the load capacity computational formula of strengthened columns taking advantage of the addition method.7. The paper analyses the eccentric compressed strengthened short column by finite element theory,and compares with the bearing capacity of the first forced strengthened column and the second forced strengthened column, then fits the computational results, at last gets the strengthened short column formula of reduction of bearing capacity.By the above method, studies the effect of initial stress to bearing capacity, and compares with the bearing capacity, change rule of the strain and the stress and the second forced.8. By the study on the faying face of new and old concrete,the paper gets the working mechanism of strengthening short column and the loading transfer length under the axial load, then through numerical simulating the faying face and and anchor reinforcment,gets the distribution regularity of stress and strain. At the same time, deduces the faying face shear stress considering the concrete shrinkage and creep, and sums up the shear strength formula, at last, according to the failure modes, gets the minimum ratio of anchor bar.