Center for Infrastructure Engineering and Safety

Australia, Australia

Center for Infrastructure Engineering and Safety

Australia, Australia
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Bradford M.A.,Center for Infrastructure Engineering and Safety | Pi Y.-L.,Center for Infrastructure Engineering and Safety | Yang G.,Center for Infrastructure Engineering and Safety | Fan X.-C.,Center for Infrastructure Engineering and Safety | Fan X.-C.,Wuhan University of Technology
Engineering Structures | Year: 2015

In the non-linear in-plane elastic buckling and postbuckling analyses of shallow parabolic arches, to overcome the difficulty in deriving an accurate expression for the non-linear normal strain, an approximation assumption that the derivative of the vertical coordinate with respect to the horizontal coordinate satisfies (dy/dz)2≪1 has been adopted in many investigations. The merit of the assumption is that it leads to the same differential equations of equilibrium and the same solutions as those for shallow circular arches. However, the accuracy of the assumption and the limitation of the analytical solutions have not been examined and because of the approximation, the analytical solutions may lead to significant errors for the buckling loads of shallow parabolic arches in some cases. This paper investigates the effects of the approximation assumption on the accuracy of in-plane buckling and postbuckling analyses of pin-ended and fixed shallow parabolic arches by comparing the analytical solutions with their finite element counterparts. It is found that the analytical solutions based on the assumption have some limitations because the assumption holds approximately only for extremely shallow parabolic arches, but is not valid for most shallow parabolic arches. The analytical solutions for the buckling loads based on the assumption are larger than the corresponding finite element results for parabolic arches with a rise-to-span ratio greater than 0.08, the error of the analytical solution increases with an increase of the rise-to-span ratio of the arch, and the sources for the errors are identified and discussed. Hence, caution should be exercised when using the analytical solutions to predict the buckling load of shallow parabolic arches, particularly of those with a rise-to-span ratio greater than 0.08. © 2015 Elsevier Ltd.

Al-Deen S.,Tech Force | Ranzi G.,University of Sydney | Uy B.,Center for Infrastructure Engineering and Safety
Steel and Composite Structures | Year: 2015

This paper presents the results of four long-term experiments carried out to investigate the time-dependent behaviour of composite floor slabs with particular attention devoted to the development of non-uniform shrinkage through the slab thickness. This is produced by the presence of the steel deck which prevents moisture egress to occur from the underside of the slab. To observe the influence of different drying conditions on the development of shrinkage, the four 3.3 m long specimens consisted of two composite slabs cast on Stramit Condeck HP® steel deck and two reinforced concrete slabs, with the latter ones having both faces exposed for drying. During the long-term tests, the samples were maintained in a simply-supported configuration subjected to their own self-weight, creep and shrinkage for four months. Separate concrete samples were prepared and used to measure the development of shrinkage through the slab thickness over time for different drying conditions. A theoretical model was used to predict the time-dependent behaviour of the composite and reinforced concrete slabs. This approach was able to account for the occurrence of non-uniform shrinkage and comparisons between numerical results and experimental measurements showed good agreement. This work highlights the importance of considering the shrinkage gradient in predicting shrinkage deformations of composite slabs. Further comparisons with experimental results are required to properly validate the adequacy of the proposed approach for its use in routine design. Copyright © 2015 Techno-Press, Ltd.

Erkmen R.E.,University of Technology, Sydney | Erkmen R.E.,Center for Infrastructure Engineering and Safety | Bradford M.A.,University of New South Wales
Journal of Engineering Mechanics | Year: 2011

A numerical formulation for the nonlinear quasi-viscoelastic (creep and shrinkage) analysis of steel-concrete composite beams that are curved in their plan is developed. The creep behavior of the concrete is considered by using the viscoelastic Maxwell-Weichert model, in which the aging effect of the concrete is taken into account. Geometric nonlinearities and the partial shear interaction that exist at the deck-girder interface in the tangential (or longitudinal) direction and in the radial (or horizontal) direction owing to the flexibility of the shear connectors are considered in the strain-displacement relationship. The modeling based on the developed formulation is validated by comparisons with available results reported in the literature. The effects of initial curvature, partial interaction, and geometric nonlinearity on the time-dependent behavior of curved composite beams are illustrated in selected examples. © 2011 American Society of Civil Engineers.

Masoumi S.,Center for Infrastructure Engineering and Safety | Arab B.,Islamic Azad UniversityTehran | Valipour H.,Center for Infrastructure Engineering and Safety
Polymer (United Kingdom) | Year: 2015

In this paper, crosslinking process and thermo-mechanical properties of epoxy materials containing diglycidyl ether bisphenol-A (DGEBA) as the epoxy resin and JEFFAMINE® D-230 polyoxypropylenediamine as the hardener have been studied using molecular dynamics simulation. An algorithm to create the crosslinked epoxy has been developed, and the crosslinking process is monitored. The simulation results disclose the effectiveness of the using annealing in the crosslinking process to achieve higher crosslinking densities within shorter reaction radiuses while producing more desirable conformation. The evolution of the complex network of cured epoxy is studied by radial distribution function (RDF). The important properties of the epoxy material such as glass transition temperature (Tg), the coefficient of thermal expansion (CTE), and elastic constants are calculated. Furthermore, the variation of the properties through the evolution process is considered, and the improvement of them is captured. The results obtained from our simulation are in good agreement with the experimental results, revealing the strength of molecular dynamics to predict the material properties. Crown Copyright © 2015 Published by Elsevier Ltd.

Valipour H.,Center for Infrastructure Engineering and Safety | Rajabi A.,Center for Infrastructure Engineering and Safety | Foster S.J.,Center for Infrastructure Engineering and Safety | Bradford M.A.,Center for Infrastructure Engineering and Safety
Construction and Building Materials | Year: 2015

This paper describes the results of the testing of precast concrete slabs in a deconstructable composite steel-concrete system for the construction of bridge decks. Benign arching action is utilised to carry the point (wheel) loads to the supports and to develop the required slab capacity; the failure mode and load-deflection response of the precast concrete slabs being investigated in the study. Twelve half-scale precast reinforced concrete slab strips were tested, with the slabs being attached to steel girders using friction grip bolts to provide shear connection between the deck and the supporting steel girders. The systems were tested under a monotonically increasing point load, which simulates vehicle wheel loading. The configuration and proportion of the reinforcing steel bars and the types of transverse cross-bracing and transverse straps were the main test variables. It is concluded that friction grip bolted shear connectors can prevent relative slip between the steel girders and concrete deck slabs, so that the equilibrating tension force in the cross-bracing/transverse straps, required to develop compressive arching in the slabs, can be developed. The arching effect in the slabs is very beneficial, and cannot be ignored in rational structural design processes. © 2015 Elsevier Ltd.

Khezri M.,Center for Infrastructure Engineering and Safety | Gharib M.,Center for Infrastructure Engineering and Safety | Bradford M.A.,Center for Infrastructure Engineering and Safety | Uy B.,Center for Infrastructure Engineering and Safety
Computers and Structures | Year: 2015

Abstract In this paper, a hybrid numerical method which combines the states space approach with the generalised Reproducing Kernel Particle Method (RKPM) is proposed for the three-dimensional analysis of thick and laminated composite plates. Employing the state space approach in the thickness direction, the governing partial differential equation is transformed into a state equation. The meshless RKPM is utilised to present the in-plane distribution of the displacement and stress components while their variation in the transverse direction of the plate and lamina is captured by adopting the state space method. This results in the formation of an algebraic system of equations where the number of unknowns is independent of the number of material layers of the laminate. Moreover, the solution provides a continuous transverse stress and displacement field which is not generally achievable using conventional numerical methods. Because the method is based on a mixed variational principle, and a meshless method is incorporated as the numerical tool, enforcement of the essential boundary conditions requires special treatment and a detailed description is given of the mixed method developed for the enforcement of the essential boundary conditions. A series of numerical examples is performed to illustrate the application of the proposed method and the results obtained are compared with known analytical and numerical solutions. © 2015 Elsevier Ltd.

Zargarbashi S.,Golder Associates | Khalili N.,Center for Infrastructure Engineering and Safety
Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 | Year: 2014

An experimental program has been conducted to investigate dependency of directional plastic flow on stress increment direction. The effect of unsaturation on the stress increment direction dependency of plastic potential is also examined. Stress probing technique has been adopted for testing identical normally consolidated samples of a low plasticity clay and a clayey sand at various degrees of unsaturation and under different loading directions. The experimental results are discussed and prevailing trends are highlighted. © 2014 Taylor & Francis Group, London.

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