| Recycling demolished concrete in form of recycled lump concrete with demolished concrete lumps(DCLs)is an effective approach.Recycled lump concrete components have been successfully utilized in actual practice.However,there are few experiences in the application of Recycled lump concrete in prefabricated components,and has not applied in steel bar truss concrete composite slab.To further extend the applications of recycled lump concrete slabs,preliminary investigations on the mechanical performance of such members were carried out in this thesis.The main works in this thesis can be summarized as follows:1.Static bending tests on two recycled lump concrete prefabricated slabs and two conventional concrete prefabricated slabs were conducted,and the influences of the use of recycling demolished concrete and cross-section structural forms on the flexural performance of the prefabricated slabs is suggested.It can be found that:(1)The use of recycled lump concrete will make the prefabricated slab specimens have much higher stiffness before cracking and ultimate load than the specimens using conventional concrete,while the influence on the cracking load of the prefabricated slab specimens is not obvious;(2)The specimens with the stress reinforcements arranged on the upper layer of the distributed reinforcements(ie the standard atlas Steel Bar Truss Concrete Composite Plate form),the centroid position of the stress reinforcement is very close to the position of the neutral axis before cracking,which leads to the failure of the prefabricated slab specimen after cracking similar to that of less reinforcement or no reinforcement.that is,the specimen quickly cracks and the reinforcement strain suddenly increase,until the longitudinal bars and bottom bars can bear the tensile stress;(3)The stiffness before cracking of the specimens with the stress reinforcements arranged on the upper layer of the distributed reinforcements is slightly increased but the ultimate load will be greatly reduced,compared with the specimens with the stress reinforcements arranged on the lower layer of the distributed reinforcements,the different arrangement order of the reinforcements has no obvious effect on the cracking load of the specimens.2.Static bending tests on one Recycled lump concrete composite slab and one conventional concrete composite slab and the shear tests of interface on one recycled lump concrete specimen and one conventional concrete specimen were conducted.The influences of the use of recycled lump concrete on the flexural performance of the composite slab and the interface shear performance is suggested.It can be found that:(1)The stress and failure modes of the recycled lump concrete composite slab and the conventional concrete composite slab are similar,and the cracking load and ultimate load of the two specimens are very close.It can be considered that the two have similar flexural performance,the use of recycled lump concrete has no obvious effect on the flexural performance of the composite slab;(2)The shear strength of the interface of the recycled lump concrete slab is much higher than that of conventional concrete specimen,because the direct shear strength of the DCLs on the interface is higher than that of the concrete interface.3.The finite element numerical model of prefabricated slab is established by finite element software ABAQUS,and the rationality and accuracy of the numerical model are verified by comparing with the test results in Chapter 2.After that,the influence of the replacement ratio and the size of the DCLs on flexural performance of the prefabricated slab is analyzed.It can be found that:(1)When the replacement ratio of DCLs remains unchanged,the stiffness before cracking and ultimate load of the prefabricated slab will increase slightly with the increase of the size of DCLs.(2)When the size of DCLs remains unchanged,the stiffness before cracking and ultimate load of the prefabricated slab will increase slightly with the increase of the replacement ratio of DCLs. |
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