This paper presents the behaviour and design of axially loaded elliptical steel hollow sections filled with normal and high strength concrete. The experimental investigation was conducted with three nominal wall thickness (4mm, 5mm and 6.3mm) and different infill concrete cube strengths varied from 30 to 100 MPa. The effect of steel tube thickness, concrete strength, and confinement were discussed together with column strengths and load-axial shortening curves were evaluated. The study is limited to cross-section capacity and has not been validated at member level. Comparisons of the tests results together with other available results from the literature have been made with current design method used for the design of composite circular steel sections in Eurocode 4 and AISC codes. It was found that existing design guidance for concrete filled circular hollow sections may generally be safely applied to concrete filled elliptical steel tubes.

This paper presents a nonlinear 3-D finite element model for eccentrically loaded concrete encased steel composite columns. The columns were pin-ended subjected to an eccentric load acting along the major axis, with eccentricity varied from 0.125 to 0.375 of the overall depth (D) of the column sections. The model accounted for the inelastic behaviour of steel, concrete, longitudinal and transverse reinforcement bars as well as the effect of concrete confinement of the concrete encased steel composite columns. The interface between the steel section and concrete, the longitudinal and transverse reinforcement bars, and the reinforcement bars and concrete were also considered allowing the bond behaviour to be modelled and the different components to retain its profile during the deformation of the column. The initial overall geometric imperfection was carefully incorporated in the model. The finite element model has been validated against existing test results. The concrete strengths varied from normal to high strength (30¿110 MPa). The steel section yield stresses also varied from normal to high strength (275¿690 MPa). Furthermore, the variables that influence the eccentrically loaded composite column behaviour and strength comprising different eccentricities, different column dimensions, different structural steel sizes, different concrete strengths, and different structural steel yield stresses were investigated in a parametric study. Generally, it is shown that the effect on the composite column strength owing to the increase in structural steel yield stress is significant for eccentrically loaded columns with small eccentricity of 0.125D. On the other hand, for columns with higher eccentricity 0.375D, the effect on the composite column strength due to the increase in structural steel yield stress is significant for columns with concrete strengths lower than 70 MPa. The strength of composite columns obtained from the finite element analysis were compared with the design strengths calculated using the Eurocode 4 for composite columns. Generally, it is shown that the EC4 accurately predicted the eccentrically loaded composite columns, while overestimated the moment.

Enhancing the dependability and power density of a SPMSMs is crucial for its extensive utilization in the automotive and aerospace sectors. One major concern regarding these machines is the significant thermo-mechanical loads experienced by the overall rotating assembly due to high rotational speeds and a wide operational temperature range from $50^\circ C$ to $150^\circ C$. This poses a considerable challenge in maintaining structural integrity among the components. Redesigning components to reduce assembly complexity and weight necessitates careful consideration of boundary conditions and contact modeling to prevent catastrophic failures like magnet fly-by conditions. To reduce model complexity, a simplified approach involves integrating the hub and shaft; both machined from AISI 4340. Additionally, the application of a carbon fiber sleeve is investigated through 3-dimensional composite modeling to enhance structural integrity. The primary objective of this thesis is to scientifically justify the design and validation of an integrated rotor hub and shaft using efficient FEM and integration strategies, with the aim of maximizing the durability of a $150kW$ radial flux SPMSMs spinning at $20,000 rpm$. The integrated topology optimization is evaluated using a multiphysics platform alongside studies on motor assembly eigenfrequency. By employing the integrated approach and utilizing AISI 4340 for both the shaft and rotor hub, a weight reduction of $1.84kg$ is achieved, eliminating the need for standard components such as balancing end clamp plates, locknuts, and washers. Furthermore, introducing a carbon fiber sleeve enhances structural integrity, thereby reducing adhesive stress. The design and optimization of the rotating components ensure that the maximum von Mises stress is $50\%$ lower than the material's yield strength. Reduced masses lead to lower centrifugal forces, thereby diminishing radial stress and promoting component and assembly stiffness. / Thesis / Master of Applied Science (MASc) / This thesis aims to increase the reliability and power density of a surface-mounted permanent magnet synchronous machine (SPMSMs), a commonly used traction motor in the automotive and aerospace industries. One of these machines' main challenges is designing their components to withstand the high mechanical loads caused by their fast rotational speeds. The studies performed in this thesis use a computer modeling technique called Finite Element Modeling (FEM) to strategize and design an integrated rotor hub/shaft by maximizing the durability of a 150kW radial flux SPMSMs rotating at 20,000 rpm. Upon evaluating the integrated design using a variety of physics-based simulations, the design was found to save 1.84kg in weight, reducing centrifugal forces and improving the overall stiffness of the motor assembly. This research could lead to more efficient and durable electric SPMSMs for various applications.

No description available.

This paper describes the finite element modelling of steel beams acting compositely with proprietary precast hollow core slabs. A companion paper (Lam D, Elliott KS, Nethercot DA. Experiments on composite steel beams with precast hollow core floor slabs. Proceedings of the Institution of Civil Engineers: Structures and Buildings 1999; in press [1]) reports results of full scale bending tests and compression slab tests. The finite element package ABAQUS was used to extend the scope of the experimental work, by first demonstrating that a 2-dimensional plane stress analysis is sufficiently accurate, providing that the correct material input data and shear stud characteristics obtained from isolated push-off tests are used. The FE results are within 5% of the experimental results. An extensive parametric study was carried out to investigate the flexural behaviour of composite beams with variations in transverse reinforcement ratio, stud spacing and steel UB section.

The accuracy and reliability of three structural analysis and design programs were evaluated. The three programs considered were MicasPlus, STAAD III, and GTSTRUDL. Nine different test cases of three basic steel space frames were analyzed and designed using the programs. The nine cases were formed by modifying different modeling, analysis, and design parameters. Comparison of results obtained from the programs for each case was presented. It was found that the percentage differences in the analysis results obtained from the programs were typically less than five percent. For steel design, both MicasPlus and GTSTRUDL gave member sizes that were very close. It was also found that changing modeling parameters can have a significant effect on analysis results. This confirms the importance of accurate structural modeling. The functionality and usability of the three programs were also evaluated. After an extensive study of MicasPlus a list of suggested modifications and additions to the program was presented. / Master of Science

A general review of lattice dome geometry and connection details, leads to a modeling approach, which introduces intermediate elements to represent connections. The method provides improved modeling of joint behavior and flexibility for comparative studies. The discussion of lattice domes is further specialized for parallel lamella geometry. A procedure is developed for minimizing the number of different member lengths. This procedure is incorporated into a program, which generates the geometric data for a specified dome. The model is developed from a background which considers commercial space frame systems, static and dynamic loads, and modeling techniques using ABAQUS, a finite element program. An optional output of the generation program creates input data for ABAQUS. Modal analysis, static design loads, and earthquake loads are used in the evaluation of the model. / Master of Science

No description available.

Little is known of the actual performance of existing buildings for normally Structural Engineers do not require that their structures be tested once they are built. The wide availability of computer programs to aid Structural Engineers in design and analysis is a great advantage over previous computational tools but the very precision of computer output can give the designer a false sense of accuracy. If buildings of the future are to be safe and efficient, then an assessment of the accuracy of current analytical procedures is required. This study used some of the few published measurements of the lateral and torsional dynamic characteristics of buildings to establish accurate analytical models of the structures. These measurements, for five different buildings, consisted of data on their fundamental mode shapes and natural frequencies. Initially, estimates of these characteristics were obtained by inputting traditional evaluations of the stiffness parameters for a TABS-77 program. In general, the traditional assumptions did not result in an adequate prediction when compared with the known experimental results. Improvements were made in the analytical models by incorporating "non-structural" elements or by reducing the efficiency of certain members until the fundamental mode shapes and frequencies were matched. Implications of incorrect modelling at the design stage were investigated for both static and dynamic lateral loadings. This study shows that it is necessary to match both frequencies and mode shapes if an accurate analytical model is desired. Failure to match mode shapes can seriously affect the evaluation of loads carried by the structural elements when the building is subjected to lateral loads. Internal partitions and cladding not only add stiffness to the structure but also change the mode shape. Strong evidence is provided that these nonstructural elements do carry load and do provide stiffness. This study shows that shear lag exists in shear wall elevator cores commonly occurring in buildings and this should not be neglected. Large panels buildings apparently have significant joint rotation between panels and this should be accommodated in some manner in developing an analytical model. Considerable inaccuracies have been shown to exist in present design and practice and this study provides guidance for significantly improving present analytical modelling. / Ph. D.

Engineering design is hierarchical in nature, and if no attempt is made to benefit from this hierarchical nature, design optimization can be very expensive. There are two alternatives to taking advantage of the hierarchical nature of structural design problems. Multi-level optimization techniques incorporate the hierarchy at the formulation stage, and result in the coordinated optimization of a hierarchy of subsystems. The use of multi-level optimization techniques often necessitates the use of equality constraints. These constraints can sometimes cause numerical difficulties during optimization. Single-level decomposition techniques take advantage of the hierarchical nature to reduce the optimization cost. In this research the decomposition approach has been followed to reduce the computational effort in a single-level design space. A decoupling technique has been developed that retains the advantages of a partitioned system of smaller independent subsystems without an increase in the total number of design variables. A penalty function formulation using Newton's method for the solution of a sequence of unconstrained minimizations was employed. The optimization of the decoupled system is cheaper due to (i) cheaper evaluation of the hessian matrix by taking advantage of its sparsity, (ii) fewer global analyses for constraint derivative calculations, and (iii) utilizing the decoupled nature of the hessian matrix in the solution process. Further, the memory requirements of the decoupled system are much less than that of the original coupled system. These benefits increase substantially for design problems with larger and larger number of detailed design variables. Orthotropic material properties as stiffness global variables have been shown to be effective as global variables for panels in a hierarchical wing design formulation. The proposed decoupling technique was implemented to minimize the volume of a portal frame and a wing box. Computational savings of up to 50 percent have been obtained for medium sized problems. The savings increase as the size of the problem and the amount of decoupling is increased. The procedure is simple to implement. For truly large systems this decoupling technique provides the necessary reduction of computational effort to make the optimization process viable. / Ph. D.