OB Engineering Ltd.

Calgary, Canada

OB Engineering Ltd.

Calgary, Canada
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Bedair O.,OB Engineering Ltd.
Thin-Walled Structures | Year: 2012

The paper presents numerical procedure for stress analysis of structural components surrounding piping penetrations used in oil and gas facilities. The stress components due to the web penetration are determined by introducing fictitious models with assumed normal and tangential force distributions. The magnitudes of these forces are determined by solving set of linear equations. The influence of the perforation eccentricity and spacing on the behaviour of the structure is highlighted for several opening configurations. The influence of the penetration spacing in the vertical and horizontal directions is also investigated. It is shown that the location of the maximum stress is also affected by the penetration spacing. Recommendations are proposed to optimize the pipe penetration spacing for various configurations. It is shown that more than 60% reduction in the web stress can be achieved. © 2011 Elsevier Ltd. All rights reserved.


Bedair O.,OB Engineering Ltd.
Structural and Multidisciplinary Optimization | Year: 2010

The paper presents a numerical procedure for dynamic analysis of box girders with tee-stiffeners utilizing unconstrained optimization techniques. Unlike the finite element or finite strip methods, the procedure does not require discretization to the whole structure, thus resulting in great savings in computational time. The potential and kinetic energy of the assembled structure is expressed in terms generalized functions that describe the longitudinal and transverse displacement profiles. The problem is then converted into uunconstrained optimization problem to determine the magnitude of the lowest natural frequency and the associated mode shape. Results are presented showing the sensitivity the natural frequency to the stiffener depth (d) and the flange width (b). It is shown that the number of longitudinal and transverse stiffeners largely influence the magnitude of the natural frequency (λ) of the box girder. Design guidelines are also provided to optimize the dynamic response of the structure. The procedure is very practical and can be utilized in the industry for the analysis of box girders. © 2010 Springer-Verlag.


Bedair O.,OB Engineering Ltd.
Journal of Constructional Steel Research | Year: 2011

As the demand for light-weight steel constructions continues on the rise, efficient and accurate design procedures become extremely essential. A good understanding and knowledge of the structural performance is a fundamental step to achieve this target. The paper examines the behavior of channel members subjected to compression and bi-axial bending. A modeling strategy is first presented for non-linear analysis of channels under this combined loading arrangement. The interaction between serviceability and ultimate limit states is then highlighted. Cost-effective design spaces are shown for channels under this loading that can be used in practice to achieve economical light-weight designs. Several strategies are also presented that tackle common design challenges encountered in practice. The paper offers to practitioners and steel fabricators procedures that can be used to optimize the channel size under this general loading combination. © 2011 Elsevier Ltd. All rights reserved.


Bedair O.,OB Engineering Ltd
Recent Patents on Engineering | Year: 2012

The paper reviews recent research work developed for the analysis and design of defective stiffened panels with application to marine and aerospace structures. The review is limited to recent research work evolved over the past three decades. Varieties of numerical modeling philosophies and experimental techniques are discussed. The paper addresses various types of damages such as residual stress, fatigue cracks, manufacturing imperfections, corrosion and welding distortions. The paper also reviews recent patents developed using stiffened plates. © 2012 Bentham Science Publishers.


Bedair O.,OB Engineering Ltd.
Multidiscipline Modeling in Materials and Structures | Year: 2013

Purpose - The paper aims to review recent developments for analysis of deteriorating stiffened panels subjected to static and explosive forces. Design/methodology/approach - The first part reviews numerical procedures developed for stiffened panels subjected to explosive forces. The structural idealization, the theoretical basis, and the merits of these methods are discussed. The second part reviews the probabilistic procedures developed for analysis of deteriorating stiffened panels. The third part reviews recent work developed in several finite element modelling philosophies for analysis of stiffened panels. The influence of various parameters affecting the structural performance, such as geometric and material imperfections, corrosion, residual stresses, etc. is discussed. The fourth part reviews hybrid procedures developed to provide approximate solutions for the designers. Numerical procedure is presented using combination of energy formulations and mathematical programming techniques to model the interaction between the box girder components. Findings - Localized damage largely affects the performance of stiffened panels and must be accounted for in the design phase. Little emphasis was given in the published literature to developing simplified analytical models that can be used in practice to compute the residual strength of the stiffened panels under these types of loadings. Furthermore, analytical expressions are required to compute the reduction in the stiffness induced due to the structural or material defects. These expressions must be dependent on the type of damage. It must be noted that some of this damages is localized in nature and must be accounted for by using specialized functions to assess the structural defect accurately. Research work is required in this direction. Practical implications - The paper provides useful resource material for the engineers in practice regarding recent techniques developed to assess damaged stiffened panels subject to static and explosive loadings. The paper reviews work developed over the past 20 years that can be used as a baseline for future developments. Originality/value - Very limited literature dealt with the ultimate strength of damaged stiffened structure under static and explosive forces. No guidelines are available in current design codes to assess the damage in predicting the strength of deteriorating stiffened panels. © Copyright - 2013 Emerald Group Publishing Limited. All rights reserved.


Bedair O.,OB Engineering Ltd.
Practice Periodical on Structural Design and Construction | Year: 2011

Rectangular openings in structural members are used to allow the passage of services. Special design considerations are required to compensate for the reduction in stiffness and to minimize fatigue cracks in the web. The paper investigates the behavior of deep plate girders with rectangular openings with applications to oil and gas facilities. An efficient numerical procedure is first presented for analysis of webs with rectangular penetrations. The limitations of the current AISC guidelines and Canadian design procedures are also highlighted. Recommendations are proposed for structural engineers to minimize web stresses in the girder. The influence of these penetrations on the performance of the plate girder is also illustrated for several loading conditions. It is shown that for openings with aspect ratios (α/β)>1, the stress decreases as the opening radius of curvature (r) increases. Also, the location of the maximum stress is largely influenced by the opening aspect ratio (α/β). It is also shown that a slow increase in the web maximum stress results when the opening curvature (r)<40mm. For plate girders under shear loading, the web stress decreases by increasing the opening curvature (r). © 2011 American Society of Civil Engineers.


Bedair O.,OB Engineering Ltd
Recent Patents on Engineering | Year: 2011

The paper presents design aids for stability limit state design of wide flange beam-columns I-sections that can be used by the structural engineers to achieve cost-effective designs. Current design provisions ignore the influence of the web/flange size in the design of beam column members. Design curves are provided for various compression/bending stress ratios. The influence of the flange/web width (b/d) ratio on the web stability is also highlighted. The variation of post-buckling deflection for various stress ratios is also presented. Related patents to the subject are also provided. © 2011 Bentham Science Publishers.


Bedair O.,OB Engineering Ltd.
Practice Periodical on Structural Design and Construction | Year: 2011

The paper examines the behavior of lightweight channels under combinations of axial compression, major and minor axis bending. Design guidelines are proposed that can be used by practicing engineers to maximize the channel section performance. Results are presented showing the design space of several North American standard cold-formed steel sections subjected to this load combination. A three-dimensional multistory building model is used to demonstrate cost-effective design strategies that cope with challenges encountered in practice. The influence of the flange, web size, and section thickness on the ultimate strength and serviceability of the channel section are also highlighted. The study leads to significant guidelines that can be used by practicing engineers and steel fabricators in order to optimize the section sizes under this load combination. © 2011 ASCE.

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