Cellular beams (I sectioned steel beams with web openings) are frequently used in different types of construction to achieve attractive, flexible, and effective solutions. These beams have other advantages such as providing passages for building services and achieving longer spans. However standard beam theory cannot be applied to calculate the maximum displacement of a cellular beam due to the presence of the web openings resulting in significant shear deformations in the web and consequently the flanges and to that normal stresses are no longer distributed linearly across the crosssection. This research aims to gain a thorough understanding of the serviceability behaviour of cellular beams and to propose a simple and relatively accurate hand calculation method to determine their deflections by practicing engineers. The research also examines the failure loads and modes of failure of simply supported cellular beams when subjected to vertical loads. Extensive numerical analyses using finite element (FE) method have been undertaken in this thesis. Therefore FE models of several cellular beams are first validated against available experimental measurements in terms of stresses, deflection, and modes of failure. The shear and normal stress distributions in cellular beams are examined numerically. The results show that: 1) there are relatively large shear stresses around the midheight section of the webpost with associated very small normal stresses; 2) normal stresses vary linearly in the webpost with maximum at the flange level and zero at some distances away from the neutral axis; 3) the normal stresses are nonuniform in the T sections at the opening centres and the maximum is at the edge of the opening; and 4) the normal stresses are not smooth along the flanges and suggest that their plane sections do not remain plane during bending. To calculate the deflection of simply supported cellular beams, a cellular beam is divided into two components, the cellular web and the flanges, and their bending and shear deformations are examined to quantify their individual contributions to the total deflection. The bending deformation of a cellular web is analytically investigated and equations are developed to convert the cellular web beam into an equivalent solid beam with variable crosssections and then to an equivalent solid uniform beam. Many practically used cellular webs are evaluated using the FE method to identify their shear deformations. In this respect shear deformation factor is introduced to quantify the shear deformation of the web. These studies led to the determination of the equivalent second moment of area of the cellular web which caters for both bending and shear effects. The effect of the design parameters (span to depth ratio, opening diameter to height ratio, web thickness, flange thickness, flange width, and opening spacing) on the deformations of the flanges is numerically examined and the results reveal that the flanges undergo significant deformations. These deformations are due to deformations of the cellular web which arise from two sources: the shear deformation in the webpost and the deformation at the opening centres. Theoretical equations are developed to determine these deformations. A complete hand solution to the deflection problem is developed based on the above studies. The newly developed method provides an improved understanding of the deflection problem and quantifies the deflection contributions from shear and bending and from flanges and the web. Comparison with existing methods shows that the developed method has simplified the hand calculation of deflection but with enhanced accuracy. Finally, two hand calculation examples are provided together with a flow chart so that the developed method can be followed by practicing engineers. The failure modes in cellular beams such as pure bending, Vierendeel Mechanism, and Webpost buckling using FE program LUSAS have been investigated in a paramet
Date of Award  31 Dec 2017 

Original language  English 

Awarding Institution   The University of Manchester


Supervisor  Tianjian Ji (Supervisor) 

Deflection, stress distributions and modes of failure of cellular beams
Sheena, N. (Author). 31 Dec 2017
Student thesis: Phd