Experimental Study On Behavior Of Full-Scale Stone Beams Of Ancient Buildings In Beijing

In recent years, the reinforcement and repair of ancient structures have attracted more and more attention in our country, and the unique ancient structure, stone structure, has been arousing people's concern. At present, the existing reinforcement methods of stone members are mainly of CFRP cloth reinforcement, CFRP rods reinforcement, prestressed reinforcement, ferrocement mortar reinforcement, etc. But most of these strengthening methods should not be directly applied to heritage buildings, because they will cause certain damage to the original artifacts in different degrees, and it is difficult to accomplish the reinforcement principle of reversibility in ancient buildings, so they have some limitations in strengthening ancient buildings. Besides, the specimen sizes in some relevant tests were usually small, while the actual components are mostly large-scale, so the size effect on the experiment cannot be ignored.For the above, after the stone material tests, the external prestressed strengthening method and the angle steels and PET belts strengthening method were proposed which were brand-new and practical. At the same time, the experimental study on behavior of twenty-three full-scale stone beams was carried out. The stones used for the tests were natural greenish white marble and white marble quarried from Fangshan, Beijing, China. The flexural behavior of the stone beams unstrengthened and strengthened by three different methods(CFRP cloth strengthening, external prestressed strengthening, angle steels and PET belts strengthening) was analyzed. And the shear behavior of the stone beams unstrengthened and strengthened with CFRP cloth was also analyzed. At the same time, the difference between the strengthened and unstrengthened stone beams was compared.The experimental results showed that:(1) the flexural capacity and deformation capacity of the strengthened stone beams were improved to some extent. After cracking,the strengthened stone beams still had certain bearing capacity,namely bearing capacity margin;(2) the shear capacity of the stone beams was relatively high and the shear failure mode did not appear in the whole tests, so the operating condition of the shear failure can only be appropriately considered in the actual reinforcement engineering;(3) Before cracking, the assumption of plane cross section was established, and the ultimate flexural capacity of the stone beams was connected with stone material and specific strengthening methods. By comparing the experimental data and the theoretical analyses, a simplified calculation formula of the flexural capacity and the shear capacity of the strengthened and unstrengthened stone beams were proposed, and the test results had good agreement with the calculation results, which had certain guiding significance to the actual reinforcement engineering. In practical reinforcement projects, we can comprehensively select appropriate reinforcement method based on factors such as construction conditions, economic conditions and so on.