International Journal of Structural Engineering (5 papers in press)
RC skew slabs behavior: a finite element model
by Eman Ismail
Abstract: Skew slabs enable to achieve a variety of solutions in, for instance, roadway alignments which contribute to a minor environmental impact for new road construction projects. But the force flow in skew slabs is much more complicated than in straight slab. Thus, the problem is more critical when constructing skew slabs. The complex behavior of skew bridge slabs makes the utilization of Finite Element method (FEM) the most critical and essential analytical tool to model reinforced concrete (RC) skew slab and calculate the non-linear behavior of its structural members with considerable accuracy. This paper uses the general purpose of 3D-finite element and ABAQUS software to design straight and skew slabs. Six separate bridge slab models/sketches of different angles were produced. Same material and material properties, loading, boundary conditions and meshing were used to determine the response and behavior of each bridge slab. The slab is made of concrete class C35/45.
Keywords: Skew slabs; RC concrete; Loading; Slab; Finite Element.
Scheme for beam progressive collapse mitigation
by Bilal El-Ariss, Said A. Elkholy
Abstract: Latest recommendations have made provisions to improve structure resistance to progressive collapse in the event of interior support collapse. This paper defines a mitigating scheme to repel progressive collapse in reinforced concrete beams due to damaged interior supporting member by providing a new path to transfer the loads to other supporting members. The mitigating scheme suggests the use of unbounded unstressed externally installed fibre reinforced plastic cables with straight profile and three deviators. An open source finite element package for structural analysis (ZEUS-NL) using the fibre element approach is adopted to numerically model the mitigated beam. The proposed numerical model evaluates the progressive collapse of such beams using a push-down analysis to simulate column removal. It assumes that the anchorage and deviator locations of the external cables act as rigid arms that connect the external cables to the beam. The numerical results demonstrate that the defined mitigating scheme increases the beam resistance to progressive collapse due to interior column failure.
Keywords: progressive collapse; FRP external unbounded cables; fibre element approach; cable deviators; catenary action.
A consistent triangular thin flat shell finite element with drilling rotation based on the strain approach
by Hamza Guenfoud, Mohamed Himeur, Hassina Ziou, Mohamed Guenfoud
Abstract: The paper offers a new flat shell finite element. It results from the combination of a membrane and a bending elements, both founded on the strain based formulation. The used membrane element is the T43_Eq. It is a triangular element with four nodes, three nodes at the vertices and the fourth one at the barycenter. Each node has three degrees of freedom, two translations and one rotation around the normal. The coefficients related to the degrees of freedom at the internal node are subsequently removed from the element stiffness matrix by using the static condensation procedure. The interpolation functions of strain, displacements and stresses fields are developed from equilibrium conditions. Then, the plate element used for the construction of the shell element is a triangular four-node thin plate element based on: the deformation approach, the four fictitious node, the static condensation and the analytic integration. The shell element result of this combination is robust, competitive and efficient. The shell element result of this combination is robust, competitive and efficient.
Keywords: finite element method; membrane; plate; shell; condensation; deformation approach; true rotation.
Review study on the current development of confined high-strength concrete
by Abdullah Zawawi Awang, Chau-Khun Ma, Ahmad Beng Hong Kueh, Wahid Omar
Abstract: This paper reviews the current development of the confined high-strength concrete (HSC). The differences between conventional concrete and HSC, the detailed mechanical characteristics of HSC, advantages and disadvantages, and the importance of confinement in HSC are critically reviewed. The beneficial effects of confinement in improving the low-ductility of HSC are also discussed. In addition, the recent progress in the research on confined HSC is presented. Subsequently, the existing stress-strain models for confined concrete are reviewed. In conclusion, the review paper notes and highlights some essentials points from the aforementioned discussion where several recommendations have been made for the advancement of this ever-developing topic.
Keywords: high-strength concrete; ductility; brittleness; confinement; steel straps.
New plasticity model using artificial neural networks
by Lyamine Briki, Noureddine Lahbari
Abstract: Concrete is one of the most widely used materials in building construction. Under static loads, the concrete is subjected to various stress states associated with significant deformation. In this paper, we study the feasibility of using artificial neural networks for modelling the mechanical behaviour of plain concrete in compression under static loading using the theory of plasticity. The database used for the development is obtained from a selection of previously published tests results and includes a series of uniaxial, biaxial and triaxial compression tests. This database is used for making and testing predictive models. The results of the ANN model can accurately predict the load resistance and deformation capacity in various compression stress states. Expansion and plastic contraction of concrete under different confining pressures and the nonlinear behaviour of concrete are simulated. The results show that the accuracy of the proposed ANN-based models is satisfactory compared with experimental results. It is also shown that the RBF neural network model may accurately represent the load resistance and deformation capacity for three types of compression tests.
Keywords: concrete; compression; plasticity; failure criteria; artificial neural network; ANN.