Across-partition Contact Analysis with Adaptive Tracking

The current work proposes a novel adaptive node-to-surface contact approach to discretise the across-partition contact boundaries and to trace the evolution of contact locations for problems with across-partition contact boundaries

Conceptual issues in geometrically nonlinear analysis of 3D framed structures

Accepted versio

Guidance on the design for structural robustness

This JRC Science and Policy Report presents scientific and technical background information to introduce the different aspects involved in providing robustness of structures. It is intended to bring together references and ongoing work on the subject as well as stimulate debate. It presents background information, state-of-the-art references and discusses provisions in available guidelines. As such, it serves as a basis for further work to achieve a harmonized European view on the consideration of robustness in the design, execution and assessment of structures. The report focusses on new-build construction, although the underlying principles also apply to existing structures. The report introduces the general principles of structural robustness, including concepts and terminology, hazards and damage scenarios as well as assessment of the consequences of failure. An overview is provided of current standardization and design guidelines in Europe as well as outside of Europe. Strengths and weaknesses in current provisions are discussed. State-of-the-art information is collected covering alternative design strategies, approaches and considerations. Specific information on strategies to improve robustness is outlined, including the importance of allowing for ageing and deterioration, and aspects related to multi-hazard design. Whilst robustness as a design principle covers a range of extreme design events, including seismic and fire, differences in design approaches for such exposures are also important to recognize. State-of-the-art research information is referenced where available. Finally, a series of novel proposals for robustness provisions is provided encompassing more detailed technical guidance concerning the tying force strategy, the alternative load path strategy, etc. are proposed to encourage discussion.JRC.E.3 - Built Environmen

Nonlinear dynamic analysis of framed structures.

Imperial Users onl

Objective modelling of reinforced concrete structures

The finite element (FE) method is a powerful technique that can provide numerical solutions to the response of reinforced concrete (RC) structures. However, results obtained from FE models are often not objective in the sense that the numerical solutions of FE models depend on aspects such as the selection of mesh size, load step size etc. FE model objectivity aims at the development of FE models for which the predicted results converge with refinement. To date, many research studies have been carried out on the objectivity of FE solutions for RC structures. However, considerable uncertainty still exists because of the many parameters which are involved in the analysis. The parameters affecting FE analysis of RC structures may be divided into two groups: material parameters and procedural parameters. The main parameters related to the material behaviour are tension softening and interaction between steel reinforcement and concrete. On the other hand, the procedural parameters which affect directly the results of the analysis are the load step, mesh size, iterative scheme, and number of cracks allowed per load step, numerical integration rule, and the use of static vs. dynamic analysis. In an effort to investigate these parameters, the current research is primarily aimed towards developing finite element formulations and solution procedures that facilitate the objective modelling of RC structures. The present study focuses on a subset of the above parameters that appear to be most relevant to objective modelling. Two new formulations have been developed in this work which allows the objective modelling of RC beam-column members, including geometric and material nonlinearity as well as bond slip. Particular emphasis is placed on predicting crack localisation in the concrete and stress concentrations in the steel reinforcement across such cracks, as this is particularly relevant to the modelling of RC structures under extreme loading. Several verification and validation studies are presented in the thesis to illustrate the key features of the proposed formulations and their applicability to the objective modelling of RC framed structures.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Meshless local buckling analysis of steel beams with irregular web openings

In addition to typical perforated beams with regular openings of circular or hexagonal holes, the use of beams with irregular web holes of different shapes and arrangement is also widespread in steel construction. Despite some advantages over typical perforated beams, the behaviour of such beams is complicated by the irregularity of openings, which demands more reliable tools for assessing their local buckling response. This paper considers the efficient local buckling analysis of beams with regular and irregular web openings, employing the Element Free Galerkin (EFG) method for the numerical discretisation together with a simplified buckling assessment approach from the Rotational Spring Analogy (RSA). This combination offers a more effective means of buckling assessment utilising an iterative procedure of a rank 2 reduced eigenvalue problem along with a shifting local region. Several illustrative examples are provided to demonstrate the effectiveness of the proposed EFG/RSA approach for local buckling analysis of steel beams with irregular openings

An anisotropic plastic‐damage model for 3D nonlinear simulation of masonry structures

Predicting the structural response of masonry structures with acceptable accuracy is paramount to safeguard the historical heritage and build new constructions with safety margins adequate to modern standards. However, due to the heterogeneous nature and anisotropic response of masonry, such prediction is still difficult to achieve, where most current masonry representations are based upon homogeneous isotropic material models or even more simplified masonry macro-elements. In this article, a novel anisotropic constitutive model to be used in detailed 3D continuum FE representations is described. This is based upon the application of the transformed-tensor method to an isotropic uncoupled plastic-damage model, which is further enhanced by additional novel features enabling the proper definition of the shear behavior both in terms of yielding surface and damage evolution while increasing local computational robustness. Illustrative examples at different scales are presented, highlighting the characteristics and potential of the developed masonry material model. Focus is placed on the mechanical behavior under uniaxial and biaxial stress states considering pure compression on wallets with varying inclination of the material principal axes and the out-of-plane response of wall components. The numerical results confirm the ability of the proposed constitutive model to predict typical masonry anisotropic response characteristics, which cannot be accurately represented by standard isotropic representations commonly used in professional practice and research

Nonlinear macroelement for steel shear walls under seismic loading

This paper proposes an efficient macroscale representation for unstiffened thin steel shear walls, enabling accurate and efficient predictions under earthquake loading. The 8-noded macroelement incorporates six nonlinear springs with asymmetric constitutive relationships to represent the cyclic response of steel panels. The macroelement formulation is introduced first, followed by the constitutive model for the nonlinear springs, which allows for strain-hardening in tension, strength degradation in compression, residual strength at the strain reversal point, and stiffness reduction. The material parameters for the constitutive model are calibrated by multi-objective optimisation with Genetic Algorithms based on the numerical results provided by accurate nonlinear FE models with shell elements. Linear regression is utilised to establish the material parameters for infill plates with different geometric properties. The residual of dissipated energy for the calibrated macroelement models lies between 3 % overestimation and 12 % underestimation compared to detailed shell element models, whereas the computational demand is reduced with wall-clock time reductions of more than 97 %. Finally, the proposed macroelement is verified in numerical examples, where a substandard RC frame enhanced with different types of steel shear walls is analysed under cyclic loading using detailed shell element models and the proposed macroelement for the steel wall components. The excellent comparisons confirm that the proposed macroelement model provides an efficient and accurate description of unstiffened steel wall components, and it can be used for realistic nonlinear dynamic simulations of framed buildings equipped with steel walls under earthquake loading

Nonlinear Dynamic Mesoscale Analysis of Masonry Buildings Subjected to Earthquake Loading

Unreinforced masonry buildings constitute an important part of the architectural and engineering heritage. A large number of these structures is located in earthquake prone regions, but their seismic response is often inadequate, and they commonly suffer substantial damage when subjected to earthquake loading. Therefore, at present there is a pressing need to develop accurate assessment strategies providing realistic response predictions under dynamic loading which are critical to address the development of effective strengthening solutions. In practical assessment of unreinforced masonry buildings, macro-models are usually employed because of their simplicity and computational efficiency. However, the complexity of the dynamic response of masonry structures under extreme loading can be captured only by employing detailed modelling strategies, where all sources of nonlinearities are taken into consideration. In this work, a detailed 3D mesoscale modelling approach is adopted, where cracks in mortar joints and masonry units are represented using nonlinear interface elements with detailed material descriptions allowing for degradation of strength and stiffness under cyclic loading. An advanced domain partitioning approach utilising parallel computational resources is employed to enhance computational efficiency. The potential of this approach is demonstrated considering the dynamic response of a full-scale building tested in laboratory in previous research. The results of this study reveal that the proposed approach, although computationally demanding, is capable of predicting the seismic response of entire buildings with good accuracy, at both the local and global levels. The modal dynamic characteristics, along with the main structural resistance mechanisms, the crack patterns and the base shear-floor displacement curves are captured in very good agreement with the experimental observations