Assessing the behaviour of reinforced concrete columns under blast loads

This Thesis is concerned with the numerical investigation of the structural response of reinforced concrete columns under blast loads, by means of dynamic nonlinear finite element analysis. This study provides an in depth understanding of the mechanics underlying reinforced concrete structural response under blast loading and studying the effect of certain important design parameters on the exhibited behaviour. The numerical investigation was carried out through the use of a well-established commercial finite element package (Abaqus) and employed a numerical model capable of accounting for the brittle nature of concrete. The latter model forms an extension to the ‘brittle crack’ model (already available in Abaqus) and was developed in order to overcome the shortcomings of the existing concrete model in describing concrete material behaviour in compression. The verification of the validity of the numerical predictions is based on a comparative study with relevant experimental data. The validated models are then employed to investigate the effect of various parameters on the exhibited response and are used to identify the reasons that trigger the experimentally and numerically observed change in structural behaviour under high loading rates (compared to that established under static loading). On the basis of the predictions obtained from the FE analysis a new graphical method was developed, based on building complementary diagrams, for the effective derivation of Pressure-Impulse (P-I) diagrams. This method aims to overcome the problems associated with their inherent sensitivity to any change in the state of the analysed structural system. Through the combined use of the validated FE model and the proposed graphical method, P-I diagrams and the associated complementary diagrams are presented and the efficiency and applicability of the methodology is demonstrated

Strength determination for band-loaded thin cylinders

Cylindrical shells are often subjected to local inward loads normal to the shell that arise over restricted zones. A simple axisymmetric example is that of the ring-loaded cylinder, in which an inward line load around the circumference causes either plasticity or buckling. The ring-loaded cylinder problem is highly relevant to shell junctions in silos, tanks and similar assemblies of shell segments. The band load is similar to the ring load in that a band of inward axisymmetric pressure is applied over a finite height: when the height is very small, the situation approaches the ring loaded case: when the height is very large, it approaches the uniformly pressurised case. This paper first thoroughly explores the two limiting cases of plastic collapse and linear bifurcation buckling, which must both be fully defined before a complete description of the non-linear and imperfection sensitive strengths of such shells can be described within the framework of the European standard for shells EN 1993-1-6 (2007). Finally, the application of the Reference Resistance Design (RRD) over the complete range of geometries for the perfect structure is shown using the outcome of the limiting cases. (EN1993-1-6, 2007; Rotter, 2016a; 2016b; Sadowski et al., 2017)

Fidelity of computational modelling of offshore jacket platforms

The development of oil and gas exploitation offshore has a history of about half a century. Many platforms have been built since to facilitate the production of hydrocarbons oil and gas, of which fixed offshore jacket type structures are the most commonly adopted rigs for shallow water depths. The present paper focuses on the modelling of a 4-legged X-braced jacket type platform, representative of a typical fixed platform in the North Sea using nonlinear finite element analysis. Normally, offshore platforms are conservatively designed using linear-elastic models to determine the effects of applied actions. The nonlinear effects of joint flexibility, piled foundations and geometrical imperfections on the platform behaviour are investigated in this paper. Joint flexibility is studied by modelling the jacket using beam elements and introducing rigid or flexible joints. A hybrid model, with the critically loaded leg and connected joints built using shell elements, is applied for the investigation of localised effects on increasing joint flexibility. The soil-pile interaction is modelled implicitly using sets of decoupled springs distributed along the piles. The geometrical imperfections are introduced in the compression legs of the jacket. The imperfect leg shapes are generated based on the failure modes of the platform. The platform is loaded by operational and environmental loads. The environmental loads are gradually increased until platform failure occurs. Eight load cases are considered, where the environmental loads are applied in 4 end-on and 4 broadside directions. The findings of the paper indicate that incorporation of joint flexibility and piled foundation result in the reduction of platform yielding and ultimate strength. The piled foundation affects platform stiffness severely. The imperfections increase platform deformability in the elastic rage and lead to dramatic reduction of jacket base shear capacity

Sustainable deployment of environmental management systems for higher education institutions:challenges and limitations

Higher education institutions (HEIs) face unique barriers to implementation of environmental management systems (EMSs) compared to the private sector, where formal EMS approaches such as ISO 14001 are widely used. HEIs across the world have tended to adopt structured EMSs through less formal methods or apply bespoke approaches based on institutional drivers for implementation. This chapter explores organizational factors specific to HEIs that impact on their ability to implement and sustain formal EMS approaches. An in-depth review was undertaken examining key organization barriers to EMS adoption, and organizational factors specific to HEIs that can affect the successful implementation and sustainability of EMS approaches. The study finds that considerations of the key actors, existing organizational structures, governance and leadership, and resistance to change are important areas to consider in the implementation of an EMS within an HEI. UK HEIs are used as a case study to examine the relationship between EMS uptake and performance, and identify trends toward the adoption of various types of systems. We find that a trend toward the adoption of more formalized EMS approaches among UK HEIs contradicts the suggestion from the literature that less-formal approaches may be more suitable. The study challenges the assumption that formal approaches to environmental management such as ISO 14001 and Eco-Management and Audit Scheme (EMAS) provide the gold standard EMS, suggesting that alternative standards may be more suitable in the context of the unique organizational structures and key barriers to EMS implementation faced by HEIs

Tensegrity Structures Design Methods

Tensegrity structures are pre-stressed systems of cables and bars in which no bar is connected to the other and the structure has no continuous rigid skeleton. This general introduction presents an original general method for the design of tensegrity structures, the first configurations of which were found by trial and error. The book begins with two-dimensional tensegrity structures, particularly tensegrity nets, tensegrity chains, tensegrity rings and tensegrity arches. These are then developed to original configurations of spatial tensegrity structures such as tensegrity slabs, primitive spatial tensegrity arches, and primitive tensegrity domes, as well as more elaborate spatial tensegrity structures such as tensegrity cylindrical shells, slim tensegrity domes, tensegrity vaults, and tensegrity caps. • Presents a robust new approach to the design of tensegrity structures • Extends tensegrity structures to new three-dimensional configurations Tensegrity Structures Design Methods suits structural, civil, and mechanical engineers and architects, as well as graduate students. Oren Vilnay is Professor Emeritus and was founder and head of the Department of Structural Engineering at Ben Gurion University Israel. He is also former head of the Structural Engineering Section at Technion-Israel Institute of Technology. Leon Chernin is Lecturer at the University of Dundee. He was granted a PhD in Structural Engineering from the Technion-Israel Institute of Technology. His research activities encompass both physical testing and numerical modelling.</p