Simplified analysis of wall-frame structure with columns and girders of unequal lateral dimension

Abstract

This thesis presents a comprehensive finite element study of the composite behaviour of brick masonry column with ferrocement overlay. The ANSYS package available at BUET Computer Centre has been used to perform this fmite element analysis. The model considers the columns as a composite of three types of materials viz. bricks, mortar matrix and ferrocement. The nonlinear response of the column is produced by a combination of nonlinear deformation characteristics and progressive failure of the constituent materials. The material properties for the analytical model are determined from tests on samples of ferrocement, bricks, mortar and small brick masonry specimens. A total of 48 columns were tested in this study. The investigations were carried out under only concentric and eccentric. short term static loading. The application of ferrocement overlay on the bare masonry column increases the load carrying capacity of the column quite significantly. With the increase of cross sectional area of column by 46% due to addition of ferrocement overlay, the average increase in strength is found to be 184% for axial loading and 158% for eccentric loading. The results of the finite element analysis are verified by comparison with the uniaxial behaviour of masonry column with ferrocement overlay. Several parameters like type of ferrocement overlay, discontinuity in ferrocement overlay, mortar proportion and number of layers of wire mesh were varied to produce variations in behaviour and in failure modes of the specimens. In general, the agreement between finite element analysis and experiment in case of failure load, failure pattern and load-deformation characteristics is good. Sensitivity analyses of various parameters like bed joint thickness, tensile and compressive strength of mortar, brick and ferrocement, number of layers of wire mesh and modulus of elasticity and Poisson's ratio of brick and ferrocement, defining the material model were carried out using the finite element model. The following parameters were found to be the most significant in the range of values considered in the study: i) the compressive strength of ferrocement mortar (range: from 15 MPa to 20 MPa) ii) the tensile strength of brick (range: from 0.5 MPa to 2.25 MPa) iii) the thickness ratio of bed joint and brick (range: from 0.045 to 0.30). The finite element program available in ANSYS package has also been used to carry out a comprehensive parametric study of the composite behaviour of ferrocementcoated masonry column subjected to axial and eccentric short term static loading. The parameters related to the strength and deformation characteristics of the constituent materials of the composite (as listed in the preceding paragraph) were considered in this study. From the parametric study, empirical equations are derived to predict the ultimate loads of the ferrocement coated masonry column.