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- Mathern, Alexandre, 1986, et al.
(författare)
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Enhanced strut-and-tie model for reinforced concrete pile caps
- 2017
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Ingår i: IABSE Conference, Vancouver 2017: Engineering the Future - Report. ; 109, s. 607-614
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Konferensbidrag (refereegranskat)abstract
- Strut-and-tie models provide a simple and rational way to design discontinuity regions in reinforced concrete structures. However, when it comes to three-dimensional concrete elements such as pile caps, enhancements are needed to ensure a reliable and not overly conservative design. This paper presents an enhanced strut-and-tie model adapted to the analysis and design of reinforced concrete pile caps. The model is based on consistent geometries of three-dimensional nodal zones and struts and integrates a strength criterion for confined bottle-shaped struts. An iterative process is used in order to optimize the position of the members by refining the dimensions of the nodal zones. The model is validated by experimental results from tests on four-pile caps reported in the literature, showing effective predictions of their ultimate capacities. This enhanced strut-and-tie model can lead to safe and less conservative design of pile caps.
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- Ekevid, Torbjörn, 1973, et al.
(författare)
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Computational railway dynamics
- 2006
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Ingår i: Computational Mechanics (editors C A Mota Soares, J A C Martins, H C Rodrigues and J A C Ambrósio). ; , s. 577-598
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Tidskriftsartikel (refereegranskat)
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- Kettil, Per, 1972
(författare)
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Adaptive structural design - Integration of computational tools for CAD, adaptive FEM and optimization
- 1999
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundConstruction is one of the largest industries with major impact on economy, environment and society. Improved structural design is important since the decisions made during the design process strongly influence all later stages, i.e. construction, operation, maintenance, repair and disassembly, and hence have major impact on the total economy.Optimization methods, FEM (Finite Element Method) for numerical solution of mathematical models and parametric 3D CAD-technique (Computer Aided Design) for geometry description in an overall high performance computing process are increasingly used in mechanical engineering. In civil engineering the application of these methods is not fully exploited. AimThe aim of this thesis is to contribute in the development of tools for rational structural design based on mathematics, optimization, adaptive computation and integration of methods into an adaptive structural design loop.MethodThe research method has a development and synthesis character. Ideas and methods are continuously implemented, incorporated and tested on realistic cases; e.g. column supported slabs and a common type of roadway bridge. ResultsThe thesis has presented the notion of adaptive structural design:1.Structural design has been idealized as an optimization problem.2.Programs for optimization, geometry description (CAD) and structural analysis (FEM) have been integrated to solve the optimization problem. 3.Discretization adaptivity has been tested and mathematical model adaptivity has been proposed as means to adapt the computational effort to the accuracy needed in the current phase of the design process.The tests have indicated that even for repeatedly built, standard type of structures economical savings can be utilized by improved computational methods in structural design.
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- Kettil, Per, 1972
(författare)
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Computational Engineering Development and Implementation of Computational Methods for Structural Analysis and Design
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 'Computational engineering' (CE) is computation based on mathematical models for use in engineering design. CE can be used to study and optimise structures and processes in industry and other branches of society to utilise resources in the most effective way. Modelling, simulation, optimisation and visualisation are basic methods of CE. The current development of CE is concerned with increased realism, improved efficiency, reliability and quality control, and integration of methods to solve more complex problems. The purpose of this thesis is to contribute to the development of the field of CE. As a respond, the thesis attempts to give both an overview and detailed knowledge of computational methods. The examples are limited to structural engineering, but the methodology should have a wider range of application. The thesis consists of five appended papers (A-E) and a summary. Paper A implements and tests mesh adaptive FE-analysis applied to plate bending problems. Paper B integrates CAD, FEM and optimisation programs in a nested loop for optimisation of a bridge structure. Paper C implements and tests the FEM90 program together with a CAD program in modelling and simulation of a major bridge structure. Paper D investigates methods to solve systems of non-linear equations as arising in FE-simulation of structures loaded to failure. Paper E implements and tests new pre-conditioned, iterative methods to solve large, multi-connected 3D problems. The summary gives an overview of the CE methods, and discusses computer implementation and integration of methods with the object-oriented FEM90 program as example. Paper A confirms that the SPR(D) technique provides good error estimates and that re-meshing adaptivity is applicable also for plate bending problems. The optimisation in Paper B indicated substantial cost reductions for a common type of highway bridge. However, the nested program set-up was not ideal. Paper C showed that CAD and FEM could handle complex engineering structures. However, increased realism of the simulations required improvement of methods for solution of non-linear equations. Paper D indicated that a combination of dynamics and a trust region method might improve the solution of non-linear equations. Paper E showed that the multi-grid method with mesh adaptation extends the range of the FEM to large 3D problems. The thesis shows that CE today consists of a number of useful but independent methods/programs. The object-oriented methodology provides a means to integrate the methods around data contained in natural objects defined by classes. The presentation proposes the development of generally applicable classes for use in the solution of realistic engineering problems.
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- Kettil, Per, 1972, et al.
(författare)
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Coupled hydro-mechanical wave propagation in road structures
- 2005
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Ingår i: Computers & Structures. ; 83, s. 1719 - 1729
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this paper is to simulate the water flow induced by the moving wheel pressure on wet asphalt road pavements, which may be a reason for a damage phenomenon in asphalt denoted stripping. The wet asphalt pavement is modeled as water saturated porous media. The interaction of the porous solid skeleton and the pore liquid leads to a coupled dynamic problem with the deformation of the solid and the relative velocity and pressure of the fluid as primary unknown fields. A FE program has been developed to perform simulations. The simulations clearly demonstrate the induced deformation and water flow in the asphalt. A water pumping phenomenon is obtained where water is squeezed out of the asphalt underneath the wheel load and then later sucked back when the wheel has moved away. The water velocity is however low.
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