M. Arif Gurel

Buckling of slender prismatic circular columns weakened by multiple edge cracks

SummaryThe investigation of the effects of cracks or similar weaknesses on the load carrying capacity of structural elements such as columns, beams and shells is an important problem in civil, mechanical and aerospace engineering. In this paper, the buckling of slender prismatic circular columns with multiple non-propagating edge cracks is studied by use of the transfer matrix method. The columns are modeled as an assembly of sub-segments connected by massless rotational springs whose flexibilities depend on the local flexibilities introduced by the cracks. This model enables discontinuity in rotations due to bending moments transmitted by the cracked sections. Eigenvalue equations are established in explicit form for classical columns and written for elastically supported columns. Numerical examples show that the buckling loads are affected considerably by the depths, locations and number of cracks, as expected. In case of a single crack, depending on the support conditions of the columns, the buckling loads show sensitivity or insensitivity to the crack location. For a constant crack depth, a crack located in the section of the maximum bending moment causes the largest decrease in the buckling load. In the study, modifications to take into account the intermediate elastic supports are also presented.

Strength capacity of unreinforced masonry cylindrical columns under seismic transverse forces

In this paper, the seismic resistance of unreinforced masonry (URM) cylindrical columns is investigated with an equivalent static analysis procedure. To this end, an existing numerical model developed for the stability analysis of masonry elements with rectangular cross-section is utilized and modified for the cylindrical columns. In the numerical model which takes into account the cracking of the sections and the second-order effects, the columns are divided ideally into sufficiently high number of elements, each having uniform curvature. The columns are modeled as prismatic cantilevers undergoing their own weights, eccentric vertical loads and distributed and concentrated static horizontal loads equivalent to the inertia actions. By considering two examples of columns, firstly a reference column and secondly a column from a real building, lateral seismic coefficient versus top drift level curves are obtained. On the basis of these curves, lateral load behavior of the columns is interpreted and maximum seismic load values which can be resisted by each column are determined. Implementing parametric analyses on the reference column, sensitivity of the seismic resistance to parameters such as column slenderness, magnitude and eccentricity of vertical top load, and the flexibility parameter is determined. The influence of some structural imperfections such as the deviation from vertical on the seismic resistance is also discussed in the paper.

Dynamic Analysis of Vertically Post-Tensioned Masonry Minarets

In Turkey, with the occurrence of almost every strong and even moderate earthquake, damage to masonry minarets is observed. In the present work, efficiency of vertical post-tensioning application to reinforce masonry minarets against earthquakes has been investigated. Considering a representative minaret and its post-tensioned counterpart, and performing spectral and time-history analyses, the effects of post-tensioning on the axial stresses, top lateral displacements and overturning safety have been determined. Obtained results have shown that vertical post-tensioning application is a very efficient method to reduce axial tensile stresses and lateral displacements, and to assure the overturning safety of masonry minarets against earthquakes.

Stability of Slender Masonry Columns with Circular Cross-Section under Their Own Weight and Eccentric Vertical Load

ABSTRACT This work concerns the stability of unreinforced masonry slender circular cross-sectional columns subjected to their own weight and eccentric vertical load. Cantilever columns are examined, considering that the material has infinitely linear elastic behavior in compression and has no tensile strength. For the analysis, an existing numerical model and solution procedure developed for the stability analysis of masonry elements with rectangular cross-section are utilized and adapted to the circular columns. For the instability of the columns, an appropriate criterion that relates the top lateral deflection to the intensity of the applied eccentric vertical load is employed. By considering a reference column, critical buckling load is obtained, behavior of the column interpreted and efficiency of the numerical model emphasized. Performing a nonlinear buckling analysis using a general purpose software on this reference column, obtained results are compared with those of the adapted procedure of the present study. Implementing parametric analyses on reference column, effects of the column slenderness, eccentricity of vertical load, elastic modulus, and self-weight on the buckling load are investigated. Presented calculation procedure provides a useful tool in order to calculate the critical loads or to check the stability of masonry circular columns.ABSTRACTThis work concerns the stability of unreinforced masonry slender circular cross-sectional columns subjected to their own weight and eccentric vertical load. Cantilever columns are examined, considering that the material has infinitely linear elastic behavior in compression and has no tensile strength. For the analysis, an existing numerical model and solution procedure developed for the stability analysis of masonry elements with rectangular cross-section are utilized and adapted to the circular columns. For the instability of the columns, an appropriate criterion that relates the top lateral deflection to the intensity of the applied eccentric vertical load is employed. By considering a reference column, critical buckling load is obtained, behavior of the column interpreted and efficiency of the numerical model emphasized. Performing a nonlinear buckling analysis using a general purpose software on this reference column, obtained results are compared with those of the adapted procedure of the pre...

Numerical Assessment of the Lateral Stiffness of Unreinforced Masonry Rectangular Columns

Using an efficient numerical model capable of capturing the cracking and second-order effects, this study investigates the lateral stiffness of unreinforced masonry rectangular columns at uncracked and cracked situations. The columns are modeled as prismatic cantilevers undergoing their own weights, eccentric vertical top loads, and static concentrated lateral top loads having increasing magnitude. The lateral force is considered to perform a monotonic lateral load analysis on the columns. On the basis of the numerically obtained lateral force versus lateral displacement relationships, the behavior of the columns is characterized by two limit states corresponding to the first cracking and the maximum resistance. For a reference column, the lateral stiffness values at these limit states are determined and compared with each other. The results show that the lateral stiffness of a column is related to the displacement level and hence the level of cracking. Implementing parametric analyses, the effects of some parameters are also investigated such as the column slenderness, the magnitude and eccentricity of the vertical top load, the flexibility parameter, and the angle of tilt, if any, on the lateral stiffness of the columns.