Study On Compressive Static Performance Of Tibetan Ancient Stone Masonry

Tibetan ancient architecture is an important part of Chinese ancient architectures,which contains unique historical,cultural,religious,and artistic connotations.Stone masonry is the main part of Tibetan ancient buildings,and the compressive performance is the most basic state during its long-term service.Due to the age of construction and the frequent occurrence of earthquakes in the Qinghai-Tibet Plateau,many damages have appeared in the stone masonry of ancient Tibetan buildings,such as local stone cracking,head joint expansion,through vertical cracks,stepped cracks,and mutual interaction of stones in different areas,which seriously threaten to the safety and durability of Tibetan ancient building structures.Understanding the compressive performance of Tibetan ancient stone masonry is an important foundation for understanding the mechanical property of ancient Tibetan stone masonry and the stone masonry with damages.At present,the understanding of the compressive performance of Tibetan ancient stone masonry is not perfect,so it is urgent to carry out basic research on it.In this thesis,the static compressive performance of Tibetan ancient stone masonry was studied by means of experiments and numerical simulation methods.Firstly,through the compressive and flexural tests of stone,the mechanical properties of granite were studied,and mechanical values such as strength and elastic modulus were obtained.Through the compressive tests of mortar,the strength,elastic modulus,Poisson’s ratio and other mechanical values of mortar were obtained.Through the compressive tests of masonry prism,the different effects of flat-stone and gravel-stone on the compressive performance of masonry were studied,and mechanical values such as initial cracking strength and ultimate strength were obtained.Through the full-scale wall compressive tests in the laboratory,the basic mechanical properties of the wall under compression were studied,and the initial cracking strength,ultimate strength,elastic modulus,Poisson’s ratio,stress-strain curve,damage mechanism and failure modes were obtained.A four-line model of the stress-strain relationship of the compressive wall was proposed.A more intuitive and clear understanding of the compressive performance of Tibetan ancient stone masonry has been formed.Secondly,based on the ABAQUS finite element software,combined with the material properties obtained from the experiments,under the premise of reasonable simplification of block-stone,flat-stone,gravel-stone and mortar joints,a three-dimensional simplified micro-modeling of ancient Tibetan stone masonry suitable for compressive analysis was established.The simulated equivalent plastic strain diagram which reflects the development of cracks was compared with the failure phenomenon of the full-scale wall test in the laboratory,and the load-displacement curve obtained from the simulation and the experiments were compared to verify the method of the applicability and accuracy of the modeling method.Finally,based on the simplified micro-model,through parameter analysis,the effects of Shoufen,height-length ratio and thickness of inner leaf wall on the compressive performance of Tibetan ancient building stone masonry are studied,the relationship between the compressive bearing capacity,stiffness and deformation and the above factors is analyzed,and the influence on the compressive performance of the wall was revealed.The results show that the Shoufen can reduce the center of gravity of the wall,reduce the out of plane deformation and enhance the stability of the wall.The larger the Shoufen proportion,the smaller the compressive ultimate bearing capacity and compressive stiffness of the wall.The greater the height-length ratio,the smaller the compressive bearing capacity and stiffness of the wall,and the greater the lateral out of plane deformation.Remain the thickness of the outer leaf wall unchanged,and the greater the thickness of the inner leaf wall,the greater the compressive strength,stiffness and elastic modulus of the wall.