| Based on the “Constraint prefabricated lightweight wallboard structure”, we put forward the “Prefabricated lightweight core-tie-columns with core grouted and reinforcement inserted ”. Firstly, the prefabricated light concrete hollow structural columns are produced by the ground formwork extrusion technology. After the structural column is installed in place, we insert a steel bar into the center hole of the hollow column. And then we grout the fine stone concrete so as to form a vertical continuous structural column. The reinforced and grouted structural column has the advantages of standard factory production,rigid connection of the node, itself as the formwork, and time saving, etc. Furthermore, it is in line with the national development policy of green building and housing industrialization. As he new type of structural column in the “Constraint prefabricated lightweight wallboard structure”, the reinforced and grouted structural column has some mechanical properties to be studied.From the point of stress mechanism analysis we know that the deformation coordination between interfaces is the basis to ensure the joint work among reinforcement,core column and lightweight concrete shell, and interfacial bond strength is an important condition to ensure the deformation coordination. Therefore, it is crucial to study the bonding properties between each interface of the structural column for the research on its overall mechanical performance. In this paper, the bond anchorage properties between the two interfaces of the three materials are studied by experimental study and numerical simulation analysis. The main contents and conclusions are as follows :1. Experimental study on bond anchorage properties of prefabricated lightweight structural column with core grouted and reinforcement inserted(1) Optimization of grouted materials. Evaluated the fine stone concrete, live-mixed mortar and ready-mixed mortar from bond anchorage properties and material cost. After comparison, we see that fine stone concrete is better than the other two materials in bond property and its cost is relative to the minimum. Finally, we optimize the fine stone concrete to be the reasonable grouted material for the reinforced and grouted structural column.(2) Optimized matching of bond and anchorage property. Firstly, the author analyzed the failure mode of structural column and summarized the influence of different factors on bond anchorage properties of structural column. Then the author discussed respectively the anchorage property between steel and core column and bond property between core columnand lightweight concrete shell. At last, matching relationship of the bond anchorage properties between the two interface of the stuctural column was summerized and design method of the bond anchorage length was given. The results show that if the lightweiht shell is not higher than CL5, the bar diameter is not less than 10 mm and the bond anchorage length is not more than 30 d, bond failure will occur in the structural column. And under the other conditions, the final failure of the structural column is the reinforcement yield as long as the anchorage length of reinforcement in the core column meet the anchorage requirements; otherwise, the anchorage failure of the structural column will happen.2.Numerical simulation analysis on bond anchorage properties of prefabricated lightweight structural column with core grouted and reinforcement inserted(1)Verifying the rationality of the simulation model. With the ABAQUS finite element software used, different failure mode of typical parts were investigated respectively by numerical simulation. Eight node reduced integral format of the 3D entity unit(C3D8R)is taken into account in the lightweight concrete shell and core column concrete unit model.Two node linear 3D truss element(T3D2) is used in the reinforcement. The anchorage property between reinforcement and core column is simulated by using nonlinear spring element spring2 unit. Hard contact is adopted in the normal contact surface of the precast lightweight concrete shell and the core column. Kulun friction model is adopted in the model of the interfacial tangential force. The comparison between numerical simulation results and experimental results shows that the modeling method is reasonable.(2)Effect of stirrups on the bond anchorage property of reinforced and grouted structural column. To analyze the extended parameters of simulation model, round hoop whose diameter is 90 mm is added in the lightweight concrete shell. By changing the stirrups’ diameter and stirrups’ spacing, the author analyzed the effect of stirrups on the bond anchorage property of reinforced and grouted structural column. The results show that adding stirrups in the lightweight concrete shell can reduce the shell stress 20%~35%, and reduce the shell strain 60%~80%; Stirrup rate increase by 0.1%, the constraint effect of stirrups will increase by about 4%. Therefore, adding stirrups in lightweight concrete shell can effectively improve the bond anchorage properties of reinforced and grouted structural column.3.The design method and construction measure of prefabricated lightweight structural column with core grouted and reinforcement insertedIn this chapter, the experimental results and numerical simulation results are deeply summarized. The formula for calculating the bond anchorage length of the structural columnis given, the requirements of bond anchorage structure are put forward and the construction process and operation method are summarized. This chapter provides guidance and basis for the scientific design, reasonable structure and construction method of the reinforced and grouted structural column.Among them, the bond anchorage length of the structure column is calculated by :And the construction requirements are as follows:(1)The strength of lightweight concrete in prefabricated structural columns should not be less than 10MPa;(2)The grouted material should be given priority to the selection of fine stone concrete;when the diameter of hole of the prefabricated lightweight concrete shell is less than 60 mm,the mortar should be properly selected;(3)When the grouted material is fine stone concrete, coarse aggregate particle size is not more than 20 mm, concrete strength grade should not be higher than C30 and should not be less than C15, the bond anchorage length of reinforcement should not be less than 30d;(4)When the grouted material is live-mixed mortar, live-mixed mortar strength grade should not be less than M20, the bond anchorage length of reinforcement should not be less than 50d;(5) When the grouted material is ready-mixed mortar, ready-mixed mortar strength grade should not be less than M10, the bond anchorage length should not be less than 40 d. |
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