Design Of Major Structures Research Articles

Experimental and numerical investigations on slim floor beams exposed to fire

Slim floor systems possess favourable thermal and thermo-mechanical behaviour in comparison with the traditional steel-concrete composite beams. Despite a recent surge in their usage in the construction sector, there is limited research on their performance at elevated temperatures. Due to limited investigations, there is a lack of fire design guidance for slim floor beams in major structural design codes. This study addresses the response of slim floor systems at elevated temperatures through experimental and analytical investigations. The experimental work consists of fire tests to study the thermo-mechanical response of SFBs in standard fire conditions. In addition to their thermo-mechanical response in fire, the efficiency of the rebars as an aid to enhance their fire resistance being an alternative to fire protection materials is also investigated. The test results show that the fire resistance of slim floor beams is significantly higher than the traditional steel-concrete composite beams due to the thermal gradient resulting from the concrete encasement. Further, the presence of longitudinal steel rebars enhances the fire resistance of SFBs significantly as they add to the flexural resistance of SFBs. During the tests, additional fire resistance of 79 min was achieved by the aid of steel rebars, a useful alternative to the fire protection materials which have been found to be toxic to the environment. Keeping in view the useful contribution of the steel rebars, a sensitive study was conducted using the finite element modelling to analyse the influence of their size and positioning on the fire resistance of the slim floor beams. Finite element modelling was later used to conduct a parametric study to analyse the influence of the degree of utilization on the response of slim floor beams exposed to standard fire. Degree of utilization represents the ratio between the applied load during a fire limit state and the capacity of the structural member at the ambient temperatures. The results from the parametric study were used to develop a simple design methodology by relating the degree of utilization and the average critical temperatures. Due to lack of fire design guidance in Eurocode 4, engineers usually use the design guidance proposed in Eurocode 3 which produces conservative results if applied to perform the fire design of slim floor beams as they have been developed for steel and traditional composite beams. The proposed methodology during this study is similar to that available in the Eurocodes for steel and composite beams but is developed specifically for the fire design of slim floor beams.

Optimization of Thermal and Structural Design in Lithium-Ion Batteries to Obtain Energy Efficient Battery Thermal Management System (BTMS): A Critical Review.

Covid-19 has given one positive perspective to look at our planet earth in terms of reducing the air and noise pollution thus improving the environmental conditions globally. This positive outcome of pandemic has given the indication that the future of energy belong to green energy and one of the emerging source of green energy is Lithium-ion batteries (LIBs). LIBs are the backbone of the electric vehicles but there are some major issues faced by the them like poor thermal performance, thermal runaway, fire hazards and faster rate of discharge under low and high temperature environment,. Therefore to overcome these problems most of the researchers have come up with new methods of controlling and maintaining the overall thermal performance of the LIBs. The present review paper mainly is focused on optimization of thermal and structural design parameters of the LIBs under different BTMSs. The optimized BTMS generally demonstrated in this paper are maximum temperature of battery cell, battery pack or battery module, temperature uniformity, maximum or average temperature difference, inlet temperature of coolant, flow velocity, and pressure drop. Whereas the major structural design optimization parameters highlighted in this paper are type of flow channel, number of channels, length of channel, diameter of channel, cell to cell spacing, inlet and outlet plenum angle and arrangement of channels. These optimized parameters investigated under different BTMS heads such as air, PCM (phase change material), mini-channel, heat pipe, and water cooling are reported profoundly in this review article. The data are categorized and the results of the recent studies are summarized for each method. Critical review on use of various optimization algorithms (like ant colony, genetic, particle swarm, response surface, NSGA-II, etc.) for design parameter optimization are presented and categorized for different BTMS to boost their objectives. The single objective optimization techniques helps in obtaining the optimal value of important design parameters related to the thermal performance of battery cooling systems. Finally, multi-objective optimization technique is also discussed to get an idea of how to get the trade-off between the various conflicting parameters of interest such as energy, cost, pressure drop, size, arrangement, etc. which is related to minimization and thermal efficiency/performance of the battery system related to maximization. This review will be very helpful for researchers working with an objective of improving the thermal performance and life span of the LIBs.

Automatic design of slanted wall anechoic chamber using 3D deterministic ray tube method

In order to make an anechoic chamber operate similarly to ideal OATS, various design methods of the anechoic chamber have been studied. Without changing of RAM and major structural design of the rectangle anechoic chamber, we propose a method of automatically designing the shape of a slanted wall anechoic chamber by applying the PSO to 3D deterministic ray tube method. The 3D Deterministic Ray Tube method enables efficient and fast calculation of the electric field in any slanted wall anechoic chamber. The optimized slanted wall anechoic chamber has very good performance for NSA, sVSWR compared to the general rectangle chamber.

Artificial intelligence in seismology: Advent, performance and future trends

Realistically predicting earthquake is critical for seismic risk assessment, prevention and safe design of major structures. Due to the complex nature of seismic events, it is challengeable to efficiently identify the earthquake response and extract indicative features from the continuously detected seismic data. These challenges severely impact the performance of traditional seismic prediction models and obstacle the development of seismology in general. Taking their advantages in data analysis, artificial intelligence (AI) techniques have been utilized as powerful statistical tools to tackle these issues. This typically involves processing massive detected data with severe noise to enhance the seismic performance of structures. From extracting meaningful sensing data to unveiling seismic events that are below the detection level, AI assists in identifying unknown features to more accurately predicting the earthquake activities. In this focus paper, we provide an overview of the recent AI studies in seismology and evaluate the performance of the major AI techniques including machine learning and deep learning in seismic data analysis. Furthermore, we envision the future direction of the AI methods in earthquake engineering which will involve deep learning-enhanced seismology in an internet-of-things (IoT) platform.

Rime icing on bundled conductors

With the increase of electric demand and development of high voltage technology, bundled conductors are used more frequently in new power line networks. Ice load on conductors is a major structural design criterion of power lines, and icing on bundled conductors is different from that on a single conductor because of the shadowing effect by the windward conductor. In this paper, rime icing on bundled conductors was simulated and the results were compared with that on a single conductor. The results show that the ice mass of leeward conductor is usually smaller to a degree that depends on the angle and distance between the windward conductor and the leeward conductor. Icing on several different bundle geometries was simulated, which allows the selection of the optimum bundle arrangement in regard to icing. We also made icing experiments simulating bundled conductors in an icing wind tunnel. The experimental results show a good agreement with the results of numerical simulations.

Recent changes in extreme floods across multiple continents

Analyses of trends in observed floods often focus on relatively frequent events, whereas changes in rare floods are only studied for a small number of locations that have exceptionally long observational records. Understanding changes in rare floods is especially relevant as these events are often most damaging and influence the design of major structures. Here, we provide an assessment of changes in the largest flood events (~0.033 annual exceedance probability) observed during the period 1980−2009 for 1744 catchments located in Australia, Brazil, Europe and the United States. The occurrence of rare floods in spatial aggregate shows strong temporal variability and peaked around 1995. During the 30 year period, there are overall increases in both the frequency and magnitude of extreme floods. These increases are strongest in Europe and the United States, and weakest in Brazil and Australia. Physical causes of the reported short-term variability and longer-term changes in extreme floods currently remain elusive, because the key drivers vary between catchments. Nonetheless, this approach provides the basis for a more spatially representative assessment of changes in extreme flood occurrence.

Design and optimisation of the external load bearing carry through structure of a columned multi bubble fuselage

AbstractThe blended wing-body configuration holds a major structural design challenge at the centre-body where the structure must support both wing bending loads and internal cabin pressure. A membrane approach is proposed which decouples the loads to allow their resistance by two independent structures: an inner membrane for cabin pressure and an outer structure to resist wing loads. A columned multi-bubble fuselage is proposed for the inner membrane structure, which are multispherical configuration to efficiently withstand the pressure loads. Considering this configuration, the carry-through structure can be designed and optimised. Finite element results show a significant reduction of stress level in this design over that for a conventional multi-bubble fuselage. Up to 30% weight reduction is achieved for a military cargo application that requires an extensive area with no structural interruption. For the outer carry-through structure, the topology and shape optimisations of finite element models were performed on the given design domain. The results from the shape and topology optimisations were complementary demonstrating a consistent design approach. The optimisation theory is briefly presented along with the results.

Coupled Computational Analysis of Piled-Raft System on Saturated Rheologic Geomaterial Foundation

It is well-known that soils may display strong nonlinear and inelastic characteristics. Furthermore, the viscosity or rheology of soft clays cannot be usually overlooked in the design of major structures founded on soft ground. Especially, rheologic deformation of soils may get considerable under high stress level. In fact, the saturated soft ground usually displays low strength, sensitive thixotropy, and high compressibility. In this paper, the soil deformation on interaction behaviour of piled rafts and soil foundation by using a fully coupled finite-element method of consolidation in which an elasto-viscoplastic model is incorporated. Through numerical computations, it is demonstrated that the coupled creep-consolidation analysis can give a more rational evaluation of overall performance of interaction of piled raft and soils and conventional analyses which overlooks time-dependency of soil deformation may give rise of inaccuracy in engineering evaluation and design of structures.

Functional Biopolymer Particles: Design, Fabrication, and Applications.

Biopolymer nano- and micro-particles, fabricated from either proteins and/or polysaccharides, can be utilized as delivery systems or to modulate the physicochemical and sensory characteristics of food products. This article reviews the principles underlying the design, fabrication, and application of biopolymer particles fabricated from globular proteins, used either alone or in combination with polysaccharides, within the food industry. The properties of biopolymer particles and their impact on the physicochemical and functional properties of foods are described. The molecular characteristics and interactions of the building blocks (proteins and polysaccharides) used to assemble these particles are briefly reviewed. The major structural design principles that can be used to fabricate biopolymer particles from food-grade proteins and polysaccharides are outlined. Finally, some of the potential applications of functional biopolymer particles within foods are highlighted.

Dynamics of Structures—Theory and Applications to Earthquake Engineering, Third Edition

Previous editions of Anil Chopra’s Dynamics of Structures set the standard as textbook of choice for teaching structural dynamics with an eye to earthquake engineering. This third edition has come out nearly eleven years after the first hit the bookshelves, and what a fruitful decade this has been for earthquake engineering (see review of the second edition in Earthquake Spectra 17, 549). Performance-based earthquake engineering, which was in its infancy when the first edition of this book was published, is now entering its second generation. Application of nonlinear dynamics, which was limited to small academic circles and graduate studies, is now center stage for evaluation and design of major structures. Today, hardly any serious evaluation or retrofit of a substantial building is complete without at least considering either static or dynamic nonlinear analyses. The revisions included in the third edition of Dynamics of Structures reflect the changing characteristics of structural dynamics as applied in practice; as such, this book can be useful in teaching future engineers what they need to know to hit the ground running when they graduate. As previous editions did, the book can also serve as a comprehensive reference on the subject for practicing engineers who need to understand old as well as cutting-edge topics of structural dynamics. The major revisions to the book are reflected in Part III, the section that covers earthquake response and design of multistory buildings. In particular, Chapter 19, which deals with earthquake analysis and response of inelastic buildings, has been completely rewritten. In the second edition, this chapter contained only 23 pages; in this edition it has been expanded to 60 pages. Furthermore, the chapter has been divided into two separate parts. The first part covers what has been traditionally referred to as nonlinear time-history analysis, which is recently and more accurately referred to as nonlinear response-history analysis. The second part deals with approximate methods of nonlinear analysis consisting of various pushover analysis techniques, including modal pushover analysis, for which the author has been one of the leading pioneers. Based on structural dynamics theory, the modal pushover analysis procedure is developed and its accuracy evaluated. Chapter 21, which deals with various building code interpretations of structural dynamics principles, has also been significantly revised and enhanced, and now includes explanation and discussion of the relevant provisions of the 2006 International Building Code, 2005 National Building Code of Canada, 2004 Mexico Federal District Code, and 2004 Eurocode 8. New in the third edition, Chapter 22 discusses methods for estimating seismic demands promulgated in performance-based guidelines for evaluat-

What lies beneath: surveying the Thames at Woolwich

Line 1 of the Crossrail project is planned to cross the River Thames via twin tunnels at Woolwich in east London. This paper reports on the fascinating investigation into the riverbed of Woolwich Reach, involving integration of a wide range of data from historical, geophysical and borehole sources. It illustrates how combining detailed desk studies and focused borehole investigations with over-water seismic, sonar and magnetic gradiometer surveys can assist civil engineers in the design of major structures within historic urban and tidal river environments.

On the buckling analysis and design of silos and tanks

Buckling considerations arise in the design of steel silos and tanks because the slender shell wall is subjected to compressive stresses, most commonly from the action of wind on the empty structure causing circumferential stresses, and combinations of wall friction forces, roof loads, non-uniform filling and discharge, and non-uniform settlement of the foundation causing meridional stresses. In this paper, recent research work of the author and graduate students relevant to buckling behaviour is briefly reviewed. Problems relevant to buckling behaviour, and which arose in several major tanks and silos with which the author was concerned either at the design stage or arising from operational problems, are discussed. The buckling behaviour and design of slender steel silos and tanks has been reviewed, with particular reference to buckling under wind loading, and under meridional compression. The benefits to be obtained by refined finite element analysis at the design stage have been emphasised, and several examples of buckling phenomena in the design of major structures reviewed. The occurrence of uplift of large emoty tanks under severe wind loadings has been detected. A simplified design method for wind buckling has been given, which includes an approximate consideration of the effects of imperfections, meridional end restraints and form of the wind pressure distributions. Situations under which meridional compression can govern the design have been explored. The beneficial effects of a bulk solid content against buckling have been investigated.

Ultra High Bypass Aircraft Sonic Fatigue

The development of the Ultra High Bypass (UHB) engine for transport aircraft introduces sonic fatigue as a major structural design challenge. UHB engines generate high intensity acoustic tones associated with the harmonics of the propeller blades. Current analysis methods and structural design approaches to prevent sonic fatigue cracks are based on techniques developed in the 1960s for broadband random jet-noise excitation. The high intensity noise testing and analysis completed to develop a sonic fatigue treatment design for the UHB Demonstrator aircraft are discussed. The evaluation included progressive wave tube (PWT) and shaker table testing conducted on representative aircraft components in the laboratory. Also discussed are the sonic fatigue treatment designs developed and flight tested on the UHB Demonstrator aircraft by Douglas Aircraft Company. The tests proved that lightweight and inexpensive treatments can be developed that will provide protection against sonic fatigue.

Structural Prospects for Hypersonic Air Vehicles

THE purpose of this paper is to review the major structural design problems common to all hypersonic air vehicles and describe some of the current research results to indicate the structures and materials technology produced during the initial phase of a new era in aeronautics. To further limit the scope of the discussion and to focus it on a particular application, these structural problems will be discussed in relation to a hypersonic commercial air transport that might be ready for intercontinental airline service 15 to 20 years' hence.