The Research On The Basic Mechanical Behavior Of Masonry Structure

The current situation and developing trend of research on the basic theory of masonry structure at home and abroad are summarized. The compressive stress-strain relations, failure criteria, compressive and shear behavior of masonry are studied systematically.The expressions of compressive stress-strain complete curve with inclusion of brick and concrete block masonry have been put forward through comparison andanalysis of different compressive constitutive relations put forward by scholars at home and abroad. The reasonable ratio ε_u/ε₀ is provided for the first time, whichequals to 1.6 for brick masonry, 4.0 for concrete block masonry. The expression of descending slope of descending stage provided by M.J.N. Priestley is simplified by this paper. The simplified expression is more audio-visual and simple. Three kinds of expressions of masonry elastic modulus are derived on the basis of the compressive stress-strain relation of masonry put forward by myself, deformation coordination among block, mortar and masonry and the experimental results statistic of masonry elastic modulus. The formulae of elastic modulus of brick, block and mortar are also derived on the basis of statistic regression of testing results.The failure criteria of masonry have been founded systematically at home for the first time according to Mohr-Coulomb theory, principal tensile and compressive theory. These failure criteria can reflect probable three kinds of destruction of masonry in compression-shear, in the meanwhile provide definitely boundary values to divide failure modes of slipping, tensile and compressive failure. These failure criteria bring to light the failure mechanism and influencing law of vertical compressive stress on shear strength of masonry. The calculating values of shear strength of masonry derived from these failure criteria not only agree well with experimental results, but also coincide with the interrelationship curves basically put forward by Luo WanKang.The calculating formulae of compressive strength of masonry are founded on the basis of equilibrium condition, deformation coordination and failure criteria with inclusion of brick, ungrouted and grouted concrete block masonry. These formulae reflect more comprehensively influences of strength, elastic modulus, Poisson ratio of block, mortar, grout concrete on masonry compressive strength. The form ofcalculating formulae simplified is simple. This method improves existing questions of current code such as uncontinuity of formulae and troublesomeness of calculating method.The main influencing factors on shear behavior of masonry shear wall are analyzed and summarized. The cracking load, crack distribution and its appearance sequence of wall with or without holes are analyzed using ALGOR FEA software and the failure criteria of masonry in compression-shear founded by this paper. The elasto-plastic finite element analysis on the force and deformation of masonry shear wall has been made by using MSC. Marc software and adopting two-dimensional four-node element, compressive stress-strain relation and failure criteria of masonry put forward by this paper. The predicted values of cracking load, ultimate shear load-bearing capacity and maximum horizontal deformation of wall agree better with testing results. The calculating formulae of shear load-bearing capacity of unreinforced and reinforced masonry shear wall with or without holes have been founded more comprehensively and systematically at home and abroad for the first time in which main influencing factors on shear load-bearing capacity of wall are considered. These formulae are successive and boundary condition can be satisfied. The method is clear, simple and easy to be applied. It also compensate incompleteness of current code in which the influence of height-width ratio of wall is not considered. It enlarges the application range when vertical compressive stress is greater. The minimum horizontal reinforcement percentage (which raises deformation ability of wall after crack and sustains wall integrity) has been put forward.