Proceedings of the 4 th World Congress on Civil, Structural, and Environmental Engineering (CSEE’19) Rome, Italy – April 7-9, 2019 Paper No. ICSECT 128 DOI: 10.11159/icsect19.128 ICSECT 128-1 Stress Analysis of The Effects of Mortar Thickness in Masonry Structures Using an Anisotropic Model Bahattin Kimençe 1 1 Civil Engineering Faculty / Istanbul Technical University Istanbul, Turkey kimence@itu.edu.tr Abstract - The aim of this study is to investigate the effect of mortar/brick thickness ratio, brick configuration on the masonry stresses and on masonry structure modelling. Different mortar/brick thickness ratios are micro-modelled by using stress- strain relationship. The results of these models are used to obtain the material properties of anisotropic macro-models in vertical and horizontal directions. The sample unreinforced masonry structures are simulated by the SAP2000 software using anisotropic material properties. In general masonry structures are composite materials that consists of brick and mortar. The main goal in modelling is to simulate a model that behaves close to the real structure as much as possible. Micro-modelling of masonry structure by considering its components individually is more realistic but not practical for large scale structures. In order to overcome this problem, macro-modelling is used in literature. Macro-model is obtained by smearing out the material properties of the micro-model to an anisotropic continuum material. Currently, most engineers simply analysis masonry structures with isotropic modelling in practice. However, presence of head and bed mortar joints in the construction of masonry causes the masonry to be anisotropic. Anisotropic modelling of a large scale structure does not need unreasonable effort as in micro-modelling and can be used instead of isotropic modelling easily in practice. Considering the horizontal and vertical loads in the plane, some wall types with rectangular cross-section, rectangular and arches cross-sections cavities were modeled as anisotropic and the effect of anisotropic material was investigated. In terms of displacements, an isotropic model and anisotropic models were found to be close to each other. However, when examined in terms of stresses, the maximum and minimum stresses in the masonary structure were changed. Keywords: Unreinforced masonry, mortar/unit thickness ratio, micro model, macro model, homogenization, composite materials, stress analysis. 1. Introduction The main purpose in modeling is to create a model that behaves as close as possible to the actual structure. Masonry is a composite material composed of brick and mortar. Micro-modeling, taking into account the individual components, is not practical for a more realistic but wide structure. To overcome this problem, the macro-model can be used to obtain an anisotropic continuity in the material properties of its components. Therefore, the wall elements shown in Figure 1 cause the wall to be anisotropic, since they have different material properties [1]. In this study, the modulus of elasticity in the wall structure was obtained by taking into consideration the change in the thickness of the mortar [2]. Material constants in both directions were obtained by using the stress - strain relations of the typical composite wall element in the plane stress effect. An example of this type of masonry structure is shown in Figure 2 by the author of this study during the restoration of a minaret in Istanbul where the mortar / brick thickness ratio is close to 1. Therefore, the effect of mortar thickness and anisotropic modeling on the brick wall was investigated. Only the horizontal component increased of the mortar thickness is shown figure 3. The micro-model is given in figure 3. The length of this modeled composite element was taken as L, width W, brick thickness hu, mortar thickness hm. Since the plane element is taken into consideration, the material constants are changed only in the direction 2 and in the direction 1, 3 has the same characteristics as shown fig. 3.