Inductive machine learning of optimal modular structures: Estimating solutions using support vector machines

Structural optimization is usually handled by iterative methods requiring repeated samples of a physics-based model, but this process can be computationally demanding. Given a set of previously optimized structures of the same topology, this paper uses inductive learning to replace this optimization process entirely by deriving a function that directly maps any given load to an optimal geometry. A support vector machine is trained to determine the optimal geometry of individual modules of a space frame structure given a specified load condition. Structures produced by learning are compared against those found by a standard gradient descent optimization, both as individual modules and then as a composite structure. The primary motivation for this is speed, and results show the process is highly efficient for cases in which similar optimizations must be performed repeatedly. The function learned by the algorithm can approximate the result of optimization very closely after sufficient training, and has also been found effective at generalizing the underlying optima to produce structures that perform better than those found by standard iterative methods

Improving the Prediction of the Behaviour of Masonry Wall Panels Using Model Updating and Artificial Intelligence Techniques

Out-of-plane laterally loaded masonry wall panels are still much used in modem structures. However due to their anisotropic and highly composite nature, it is extremely difficult to understand their behaviour and to date there is no analytical method that is capable of accurately predicting the response of masonry panels to the applied loadings. This is one of the major obstacles in analysing and designing masonry structures. This research studied a new method that accurately predicts the response of laterally loaded masonry wall panels. In this dissertation, the method of using corrector factors developed by previous researchers was further studied using model updating and artificial intelligence (AI) techniques based on previous experimental results of full scale wall panels tested in the University of Plymouth. A specialised non-linear finite element analysis (FEA) program was used to implement the method developed in this study. The analytical response was compared with other experimental results from different laboratories. Initially, it was found that there was some obvious noise in the experimental load deflection data, which made comparison between FEA and the experimental results very difficult. The research therefore proposed a methodology for minimising the experimental noise based on 3D surface fitting and regression analyses applied to lateral deflection experimental data. The next step was the detailed study of corrector factors using the numerical model updating procedure. Corrector factors were determined for various zones within a masonry panel (the Base Panel) by minimising the discrepancy between the experimental load deflection data and those obtained from non-linear FE analysis. A detailed model updating procedure was studied including the model analysis, the objective function and the constraint function for the genetic algorithm (GA). A uniqueness study to corrector factors was also carried out. The following step was undertaken to analyse general masonry wall panels using the findings of this study. The concept of zone similarities proposed by previous researcher, which was based on the relative distance of each zone from similar boundaries, was used for applying correctors from the base panel to the new panel to be analysed. A modified cellular automata (CA) model was used to match the similar zones between the new panel and the base panel. The generality and robustness of this method was validated using a number of masonry wall panels tested by various organizations. These walls were single leaf masonry wall panels of clay bricks with different boundary types, dimensions, with and without openings. The main finding in this research are that the boundary effects have a major influence on the response of masonry panels subjected to lateral loading, improperly defined boundary conditions in FEA are the main source of error in the past numerical analysis. Using the corrector factors that are able to properly quantify the actual boundary effects and make appropriate revisions, more accurate analysis is achieved and the predicted response of masonry walls match with their experimental results very well

Vibration Serviceability of Long Span Slender Floors

The modern trend towards long slender floors has led to major vibration serviceability issues in building floors under rhythmic loading. This happens as a result of reduced natural frequencies and damping ratios due to reduced structural rigidity (Devin et al, 2015). Even though these vibrations do not lead to structural failure in most cases, they can often create such an excessive discomfort to the occupants that they render the structure unusable (Orvin et al, 2016). A serviceable long-span floor is a floor that does not only carry the permanent and imposed loads applied onto it, but one that is stiff enough to prevent excessive deflections as well as vibrations (Cement and Concrete Association of Australia, 2003). Common structural systems used for long span floors are plane trusses, space frames and space grids. These types of structures are generally lighter and stronger because individual members carry externally applied loads mainly through tension and compression which makes them more structurally efficient than solid-web girders which are subjected to flexure (Porwal et al, 2017). This research focusses on the vibration serviceability of long span floors subjected to rhythmic loads such as aerobics, dance-type loads or similar audience participation activities. The most important parameter in the design for vibration serviceability is the natural frequency and simplified methods in which it can be estimated for concrete floors supported on a steel frame or truss exist. According to the National Building Code of Canada (NBC) resonance for structures exposed to human activity can occur if the natural frequency of the structure is below 10 Hz which takes into consideration the believe by the NBC that resonance is attainable if the forcing frequency of a repetitive motion such as dancing is around half the natural frequency of the floor (Murray et al, 2003). Another important parameter is acceleration. Critical floor accelerations occur at resonance but their effect on vibration serviceability of the floor depend on human perception. This is dependent on the activity type the occupants are involved in. Acceptable acceleration limits are recommended in the NBC and the International Standards Organization (ISO 2631-2, 1989) for various occupancies such as office or residential, dining or weightlifting and rhythmic activity (Murray et al, 2003). Because the criterion by the NBC is based on the beam theory, models the floor as a single degree-of-freedom and only considers the fundamental mode of vibration, Ji et al (1994) and Ellis et al (2004) proposed an alternative criterion which entails the characterization of the load which pertains to the determination of the load model in a form of a Fourier series, evaluation of the characteristics of the floor vibration and calculation of the response of the floor to the dancing loads. Of all the design codes reviewed, only the British Standard provided the load model which can be used in the analysis of structures subjected to rhythmic loads. The UK National Annex to Eurocode 1: Part 1-1 does, however, recommend that a designer consult literature that provide rhythmic load models such as that by Ellis et al (2004). Measures that can be applied to improve the vibration serviceability of planned or existing structures include increasing the stiffness of the structure, increasing the damping, installing tuned vibration absorbers and restricting the usage of the structure (Erlina et al, 2017). Three different floor systems were studied in this research, namely, the plane truss, space frame and space grid floors and different measures were applied to evaluate their effect on the vibration behaviour of these floor systems under rhythmic loading. The results showed that increasing the number of column supports, adding extra edge supports around the floor perimeter and increasing the floor depth all improve the vibration serviceability of the floor. The results also showed that the space frame floor performed better under rhythmic loading than the plane truss and space grid floors. The space frame, however, required large members (resulting in a relatively heavy structure) to work and is complicated and costly to construct. It was therefore determined that when taking into consideration both the vibration serviceability of the structure and the ease and cost of construction that the space grid was the best structural system to employ. Physical tests need to be carried out on existing long span floors under rhythmic loads to verify the FE analysis results obtained in this study. Guidelines in design codes should also be updated to make special provision for long-span floors subjected to rhythmic loading

Optimización del diseño estructural de pavimentos asfálticos para calles y carreteras

gráficos, tablasThe construction of asphalt pavements in streets and highways is an activity that requires optimizing the consumption of significant economic and natural resources. Pavement design optimization meets contradictory objectives according to the availability of resources and users’ needs. This dissertation explores the application of metaheuristics to optimize the design of asphalt pavements using an incremental design based on the prediction of damage and vehicle operating costs (VOC). The costs are proportional to energy and resource consumption and polluting emissions. The evolution of asphalt pavement design and metaheuristic optimization techniques on this topic were reviewed. Four computer programs were developed: (1) UNLEA, a program for the structural analysis of multilayer systems. (2) PSO-UNLEA, a program that uses particle swarm optimization metaheuristic (PSO) for the backcalculation of pavement moduli. (3) UNPAVE, an incremental pavement design program based on the equations of the North American MEPDG and includes the computation of vehicle operating costs based on IRI. (4) PSO-PAVE, a PSO program to search for thicknesses that optimize the design considering construction and vehicle operating costs. The case studies show that the backcalculation and structural design of pavements can be optimized by PSO considering restrictions in the thickness and the selection of materials. Future developments should reduce the computational cost and calibrate the pavement performance and VOC models. (Texto tomado de la fuente)La construcción de pavimentos asfálticos en calles y carreteras es una actividad que requiere la optimización del consumo de cuantiosos recursos económicos y naturales. La optimización del diseño de pavimentos atiende objetivos contradictorios de acuerdo con la disponibilidad de recursos y las necesidades de los usuarios. Este trabajo explora el empleo de metaheurísticas para optimizar el diseño de pavimentos asfálticos empleando el diseño incremental basado en la predicción del deterioro y los costos de operación vehicular (COV). Los costos son proporcionales al consumo energético y de recursos y las emisiones contaminantes. Se revisó la evolución del diseño de pavimentos asfálticos y el desarrollo de técnicas metaheurísticas de optimización en este tema. Se desarrollaron cuatro programas de computador: (1) UNLEA, programa para el análisis estructural de sistemas multicapa. (2) PSO-UNLEA, programa que emplea la metaheurística de optimización con enjambre de partículas (PSO) para el cálculo inverso de módulos de pavimentos. (3) UNPAVE, programa de diseño incremental de pavimentos basado en las ecuaciones de la MEPDG norteamericana, y el cálculo de costos de construcción y operación vehicular basados en el IRI. (4) PSO-PAVE, programa que emplea la PSO en la búsqueda de espesores que permitan optimizar el diseño considerando los costos de construcción y de operación vehicular. Los estudios de caso muestran que el cálculo inverso y el diseño estructural de pavimentos pueden optimizarse mediante PSO considerando restricciones en los espesores y la selección de materiales. Los desarrollos futuros deben enfocarse en reducir el costo computacional y calibrar los modelos de deterioro y COV.DoctoradoDoctor en Ingeniería - Ingeniería AutomáticaDiseño incremental de pavimentosEléctrica, Electrónica, Automatización Y Telecomunicacione

Structural Analysis and Matrix Interpetive System /SAMIS/ program Technical report, Feb. - Aug. 1966

Development of characteristic equations and error analysis for computer programs contained in structural analysis and matrix interpretive syste

A study of staggered and shear-wall tall building systems

Abstract unavailable please refer to PD

Elastsete-platsete telgsümmeetriliste plaatide analüüs ja optimeerimine

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Insenerimehaanikast on teada, et konstruktsioonielementide (talade, plaatide, koorikute) projekteerimisel on materjali kokkuhoiuks mõistlik arvestada lisaks elastsetele deformatsioonidele ka plastseid. Elastse deformatsiooni korral taastub keha esialgne kuju pärast koormuse eemaldamist, plastse deformatsiooni korral mitte. Antud töös vaadeldakse nn sandwich-tüüpi ümar- ja rõngasplaate, millele mõjub telgsümmeetriline ristkoormus. Ümarplaat on ringsilindriline keha, mille kõrgus on teiste mõõtmetega võrreldes väike. Sandwich-tüüpi plaadiks nimetatakse ideaalset kahekihilist plaati, mille kandva kihi paksus h on kihtidevahelise kaugusega H võrreldes väike. Kogu plaat on elastne, kui talle rakendatakse väikseid koormusi. Koormuse suurendamisel tekib plaadis üks või mitu plastset piirkonda. Doktoritöös uuritakse erinevate kinnitusviisidega tükati konstantse paksusega elastseid-plastseid ümar- ja rõngasplaate tükati lineaarsete voolavustingimuste korral. Elastse-plastse konstantse paksusega välisservast vabalt toetatud rõngasplaadi paindeülesaande lahendamiseks leitakse erinevate koormuste korral analüütiliselt ja numbriliselt plaadi läbipainded ning radiaal- ja tangentsiaalsuunalised paindemomendid. Selgub, et tükati konstantse paksusega elastse-plastse seest jäigalt kinnitatud ja välisservast täiesti vaba astmelise rõngasplaadi pingeseisundi saab jagada kolme erinevasse staadiumisse. Leitakse läbipainde ja paindemomentide avaldised vastavalt elastse, elastse-plastse ja täiesti plastse plaadi pingeseisundi korral. Numbriliselt lahendatakse ühe astmega elastsete homogeensest ja anisotroopsest materjalist ümarplaatide optimeerimisülesanded, kus etteantud plaadi ruumala korral arvutatakse optimaalsed kandvate kihtide paksused ning astme asukoht nii, et plaadi keskpunkti läbipaine oleks minimaalne. Samuti leitakse ringikujuliste lisatugede optimaalsed asukohad vabalt toetatud elastse ümarplaadi puhul nii, et plaadi läbipaine oleks minimaalne.When modelling the structural behaviour of the structural elements (e.g. beams, plates, shells), it is necessary to account for both the plastic and elastic deformations. In the case of elastic deformation the body recovers its initial shape after removing the loading, in the case of plastic deformation it does not recover. In this work, the so-called sandwich-type circular and annular plates under axisymmetric transverse loading are studied. A circular plate is a cylinder with a much smaller height compared to its radius. A sandwich-type plate is an ideal two-layered plate where the height of the carrying layers h is much smaller than the thickness of the core material H. Under small loads, the entire plate is elastic. Increasing of the load may cause the appearance of one or several plastic areas in the plate. In this thesis, the circular and annular plates with the piecewise constant thickness and different support types are investigated using piecewise linear yield conditions. The bending problem for the elastic plastic annular plate, simply supported at the outer edge, is solved by finding the deflections, the radial and circumferential bending moments for different loadings. It appears that the stress strain state of the elastic plastic annular plate with the piecewise constant thickness, clamped at the inner edge and absolutely free at the outer edge, can be divided into three stages. The expressions of the deflections and the bending moments are found in the cases of elastic, elastic plastic and entirely plastic stress strain states, respectively. The optimization problems regarding to the stepped circular plates made of homogeneous and anisotropic materials are solved numerically. For the fixed plate volume, the optimal values for the heights of the carrying layers and the location for the step are calculated while requiring minimal deflection at the centre of the plate. Also, the optimal locations for additional circular supports corresponding to the minimum of the mean deflection are found in the case of the elastic simply supported plate

Satellite swarms for auroral plasma science

With the growing accessibility of space, this thesis work sets out to explore space-based swarms to do multipoint magnetometer measurements of current systems embedded within the Aurora Borealis as an initial foray into concepts for space physics applications using swarms of small spacecraft. As a pathfinder, ANDESITE---a 6U CubeSat with eight deployable picosatellites---was built as part of this research. The mission will fly a local network of magnetometers above the Northern Lights. With the spacecraft due to launch on an upcoming ELaNa mission, here we discuss the details of the science motivation, the mathematical framework for current field reconstruction, the particular hardware implementation selected, the calibration procedures, and the pragmatic management needed to realize the spacecraft. After describing ANDESITE and defining its capability, we also propose a follow-on that uses propulsive nodes in a swarm, allowing measurements that can adaptively change to capture the physical phenomena of interest. To do this a flock of satellites needs to fall into the desired formation and maintain it for the duration of the science mission. A simple optimal controller is developed to model the deployment of the satellites. Using a Monte Carlo approach for the uncertain initial conditions, we bound the fuel cost of the mission and test the feasibility of the concept. To illustrate the system analysis needed to effectively design such swarms, this thesis also develops a framework that characterizes the spatial frequency response of the kilometer-scale filter created by the swarm as it flies through various current density structures in the ionospheric plasma. We then subjugate a nominal ANDESITE formation and the controlled swarm specified to the same analysis framework. The choice of sampling scheme and rigorous basic mathematical analysis are essential in the development of a multipoint-measurement mission. We then turn to a novel capability exploiting current trends in the commercial industry. Magnetometers deployed on the largest constellation to date are leveraged as a space-based magnetometer network. The constellation, operated by Planet Labs Inc., consists of nearly 200 satellites in two polar sun-synchronous orbits, with median spacecraft separations on the order of 375 km, and some occasions of opportunity providing much closer spacing. Each spacecraft contains a magneto-inductive magnetometer, able to sample the ambient magnetic field at 0.1 Hz to 10 Hz with <200 nT sensitivity. A feasibility study is presented wherein seven satellites from the Planet constellation were used to investigate space-time patterns in the current systems overlying an active auroral arc over a 10-minute interval. Throughout the this work advantages, limitations, and caveats in exploiting networks of lower quality magnetometers are discussed, pointing out the path forward to creating a global network that can monitor the space environment

Numerical study of improved methods of in-field capacity assessment of reinforced concrete bridges

Bridges, particularly short-span highway bridges, are basic elements of nearly all contemporary transportation networks. For reinforced concrete structures, complete information regarding the number, size, and orientation of steel reinforcement is necessary in order to make a complete strength assessment. Since reinforcement is not visible externally, making an accurate assessment without design drawings is extremely difficult. Improving the accuracy of capacity assessments of reinforced concrete bridges when information regarding the design and construction of the bridge is limited or not available would be useful in a number of situations, including military operations and disaster response. The objective of this project is to develop more reliable means of in-field capacity assessment of reinforced concrete bridges by making improved estimates of the level of longitudinal and shear reinforcement. The proposed assessment procedure is based on comparing measured structural response under controlled loading conditions to predicted structural response from analysis. This report presents results from a preliminary sensitivity study of the analytically predicted response of simply supported reinforced concrete T-beam girders with varying levels of longitudinal and shear reinforcement