Exploratory study into a safety format for composite columns exposed to fire

Current performance based structural fire engineering approaches evaluate structural behaviour under prescribed fire scenarios. The mechanical properties of the materials, the load conditions and geometric parameters are all however fraught with uncertainty, and there is currently no clear safety format ensuring the reliability of the design solution. In this contribution, a safety format is explored for evaluating the fire resistance of composite columns, following results obtained in earlier studies on uncertainty quantification. Using the safety format, a single nonlinear finite element evaluation of the fire resistance time is combined with a global safety factor, defining its design value. Under the assumptions derived from earlier work, the safety format works well, but additional parameter studies indicate that good performance is limited to relatively low ambient design utilization ratios. The results thus highlight the importance of uncertainty quantification and the limitations of basing a safety format for structural fire design on limited studies. It is concluded that detailed studies into the probabilistic description of the response of composite columns exposed to fire are required to generalize the results to a broadly applicable design rule

Accounting for multivariate probabilities of failure in vertical seawall reliability assessments

The aim of this paper is to appraise the current knowledge on seawall performance and reliability, and to make the case for improved reliability assessments of vertical seawalls, which are used here as a representative for coastal flood defences. In order to achieve this aim, a brief introduction to flood risk management is first given. Then, vertical seawalls are introduced, and their most prominent failure modes are discussed. Reliability analysis is introduced within the context of flood risk management. More specifically, the fragility curve approach that is currently in use in industry is described, and its limitations are discussed. Finally, it is argued that recent advances in multivariate extreme value models would enable improvements to the approaches currently applied in practice. It is stressed that future risk assessment models of coastal flood defences ought to include multiple failure modes and their interactions, a thorough analysis of the model uncertainties, and potential computational costs, in view of providing practitioners with an improved and functional risk assessment tool. Carter, Magar, Simm, Gouldby & Walli

Influence of near-fault effects and of incident angle of earthquake waves on the seismic inelastic demands of a typical Jack-Up platform

In this paper, the potential influence of near-fault effects and of the incident angle of earthquake waves to the seismic response of a typical jack-up offshore platform is assessed by means of incremental dynamic analysis involving a three dimensional distributed plasticity finite element model. Two horizontal orthogonal strong ground motion components of a judicially chosen near-fault seismic record is considered to represent the input seismic action along different incident angles. The fault-normal component exhibits a prominent forward-directivity velocity pulse pulse-like) whose period lies close to the fundamental natural period of the considered structure following a “worst case scenario” approach, while the fault-parallel component does not include such a pulse. Pertinent numerical data demonstrate that the fault normal component poses much higher seismic demands to the “prototype” jack-up structure considered compared to the fault parallel component. Further, significant variation in the collapse resistance/capacity values is observed among different incident angles especially for the “critical” fault normal component. It is concluded that the combined effect of forward-directivity phenomena and the orientation of deployed jack-up platforms with respect to neighbouring active seismic faults needs to be explicitly accounted for in site-specific seismic risk assessment studies. Further research is warranted to propose recommendations on optimum orientation of jack-up structures operating in the proximity of active seismic faults to minimize seismic risk

Machine Learning Aided Stochastic Elastoplastic and Damage Analysis of Functionally Graded Structures

The elastoplastic and damage analyses, which serve as key indicators for the nonlinear performances of engineering structures, have been extensively investigated during the past decades. However, with the development of advanced composite material, such as the functionally graded material (FGM), the nonlinear behaviour evaluations of such advantageous materials still remain tough challenges. Moreover, despite of the assumption that structural system parameters are widely adopted as deterministic, it is already illustrated that the inevitable and mercurial uncertainties of these system properties inherently associate with the concerned structural models and nonlinear analysis process. The existence of such fluctuations potentially affects the actual elastoplastic and damage behaviours of the FGM structures, which leads to the inadequacy between the approximation results with the actual structural safety conditions. Consequently, it is requisite to establish a robust stochastic nonlinear analysis framework complied with the requirements of modern composite engineering practices. In this dissertation, a novel uncertain nonlinear analysis framework, namely the machine leaning aided stochastic elastoplastic and damage analysis framework, is presented herein for FGM structures. The proposed approach is a favorable alternative to determine structural reliability when full-scale testing is not achievable, thus leading to significant eliminations of manpower and computational efforts spent in practical engineering applications. Within the developed framework, a novel extended support vector regression (X-SVR) with Dirichlet feature mapping approach is introduced and then incorporated for the subsequent uncertainty quantification. By successfully establishing the governing relationship between the uncertain system parameters and any concerned structural output, a comprehensive probabilistic profile including means, standard deviations, probability density functions (PDFs), and cumulative distribution functions (CDFs) of the structural output can be effectively established through a sampling scheme. Consequently, by adopting the machine learning aided stochastic elastoplastic and damage analysis framework into real-life engineering application, the advantages of the next generation uncertainty quantification analysis can be highlighted, and appreciable contributions can be delivered to both structural safety evaluation and structural design fields

A rational approach to the harmonisation of the thermal properties of building materials

The Energy Systems Research Unit at the University of Strathclyde in Glasgow was contracted by the Building Research Establishment to review existing data-sets of thermo-physical properties of building materials and devise vetting and conflation mechanisms. The UK Chartered Institute of Building Services Engineers subsequently commissioned a project to extract a sub-set of these data for inclusion in Guide A, Section 3. This paper reports the project process and outcome. Specifically, it describes the source of existing data, comments on the robustness of the underlying test procedures and presents a new approach to data classification and conflation

Economics of the Firm and Economic Growth. An hybrid theoretical framework of analysis

The characterization of individual firms is an essential step toward the study of the behaviour of industries and other more aggregated units of economics, and so to the analysis of economic growth processes. Hence, the main goal of this study is to achieve a critical discussion around the conceptualisation of the firm and its role in the dynamical process of economic growth. The approach to the main topic starts with the construction of a theoretical matrix of the economics of the firm, opening with the two major traditions of institutionalist thought in economics, and evolving then towards some considerations around the contractual and the evolutionary approaches. Another important theoretical stream that deals with organizations in economic and sociological terms also appears, the population ecology approach. After this overview, it is developed a cross-exam of distinct theoretical perspectives and the identification of possible flaws of the neoclassical theory. This confrontation, which goes throughout many imperative and controversial issues within economics such as the nature of the firm and the cognitive capacities of economic agents, results in a systematisation about the impact of this discussion on economic growth. The conclusions appear as crucial to develop further research aiming the construction of economic growth models based on a microeconomics that is closer to the reality of firms.Firm; Economic Growth; Institutionalism; Evolutionary theory; Contractual Theory; Ecology Population Theory.

reliability-based structural integrity assessment

Improved generic strategies and methods fo

Stochastic process model for timber-concrete composite beam deterioration

The aim of this paper is to present a new stochastic process model that will capture the true nature of deterioration of timber-concrete composite beams. Composite elements such as timber-concrete composite sections are designed to take advantage of compatibility of materials under sustained loading. Applied sustained load on timber-concrete composite structures causes gradual increase of deformation and deflection. In particular for timber-concrete composite beams, component materials will deteriorate at different pace over the life-cycle. In order to enable efficient management of structures in terms of required maintenance, repair and/or replacement, it is essential to be able to capture the uncertain nature of the deterioration process. We focus on modeling the deterioration of mid-span deflection of the timber-concrete composite beam over long term under sustained load. As the increasing deflection of the timber-concrete composite beam over time is generally uncertain and non-decreasing, it can best be regarded as a continuous gamma process. Examples of continuous gamma process representation have been included

Economic and Religious Choice: A Case-Study from Early Christian Communities

The aim of this paper is to elaborate an evaluative framework of religious choice within the early Christian communities reconstructed through the narrative of a New Testament Epistle, 2Peter, based on an economic approach to moral dilemmas identified in this context. Thus the work concentrates on the stances, attitudes and social practices of deviant members who engaged in free-riding within early Christian congregations and were exposed to serious self-control problems. In our attempt to employ economic theories of religion, we are in a position to better assess the efficiency of early Christian responses to the entry of competing groups in the religious market of this era, as well as to identify and explore the sort of criteria that determine the intertemporal choices of distinct religious actors.choice and markets, religious consumption, free-riding