Test Study And Analysis On Flexural Behaviour Of Steel Reinforced Concrete Beams With Discontinuous Top Flange And Filled With DCLs And FC

A straightforward use of demolished concrete lumps(DCLs)rather than recycled aggregates in structural members has proved to be an effective approach of recycling waste concrete.A series of research of structural members filled with DCLs and FC has been conducted and has been used in several construction applications.In order to advance the use of DCLs in composite structures,a steel reinforced concrete(SRC)beam with discontinuous top flange and filled with DCLs and FC is proposed,and flexural capacities in both positive and negative bending are experimentally explored in this dissertation.Three parts of main research work of this dissertation are listed as follows:1.Tests of five full-scale specimens in positive bending were conducted.Influences of some crucial variables on flexural performance of the specimens in positive bending had been discussed,and the constructability of this newly-developed structural member was examined.Flexural capacities of the specimens were also calculated and compared with the existing formulas.It is found that:(1)SRC beams filled with DCLs and FC have similar flexural capacity and stiffness with conventional SRC beams;(2)in positive bending,eliminating the top flange has very little influence on the specimen’s flexural capacity and stiffness;(3)the formula given in Chinese specification JGJ 138-2001 is still applicable for predicting flexural capacities of SRC beams with discontinuous top flange and filled with DCLs and FC in positive bending.2.Tests of four full-scale specimens in negative bending were conducted.Flexural capacities of the specimens in negative bending were studied,and the local stress condition where the top flange was cut off were mainly focused.It is found that:(1)SRC beams filled with DCLs and FC have similar flexural capacity and stiffness with conventional SRC beams;(2)in positive bending,eliminating the top flange has significant influence on the specimen’s flexural capacity and stiffness;(3)in negative bending,there is a concentration of stess where the top flange is cut off,which chould result in a plastic hinge here;(4)the existing formulas have some limits for calculating flexural capacities of SRC beams with discontinuous top flange and filled with DCLs and FC in negative bending,and a more applicable formula is proposed and demonstrates better accuracy.3.Numerical simulation on bending performance of the SRC beams with discontinuous top flange was conducted with the finite element analysis software ABAQUS,and the calculated results were compared with the tests results,based on which the parametric analysis was carried out considering different length of top flange and different corner cut.And a recommended top flange length and corner cut angle was provided.It is found that:(1)as the length of top flange grows,bearing capacity of SRC beam grows at first and then stays constant;(2)the critical length of top flange of less than 1/10 of the span is recommended;(3)for the convenience of construction,a corner cut of less than 30°on the top flange is recommended,and proper corner cut has no influence on the bearing capacity of the beam.