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- 2006 (173) (remove)
The design of safety-critical structures, exposed to cyclic excitations demands for non-degrading or limited-degrading behavior during extreme events. Among others, the structural behavior is mainly determined by the amount of plastic cycles, completed during the excitation. Existing simplified methods often ignore this dependency, or assume/request sufficient cyclic capacity. The paper introduces a new performance based design method that considers explicitly a predefined number of re-plastifications. Hereby approaches from the shakedown theory and signal processing methods are utilized. The paper introduces the theoretical background, explains the steps of the design procedure and demonstrates the applicability with help of an example. This project was supported by German Science Foundation (Deutsche Forschungsgemeinschaft, DFG)
Hinsichtlich der Integration einzelner Bauwerkslebensphasen und der verschiedenen Beteiligten, insbesondere innerhalb von Bauplanungs- und Revitalisierungsprozessen, bestehen aktuell entscheidende Defizite. Die generelle Zielstellung der in diesem Beitrag vorgestellten Forschungsarbeiten besteht in der Unterstützung und Verbesserung der Integration durch die disziplin- und lebensphasenübergreifende Bereitstellung sämtlicher bauwerksbezogener Informationen. Dies erfordert einerseits geeignete Ansätze zur Modellierung und Integration der vielfältigen disziplinspezifischen Daten, andererseits geeignete Lösungen, die einen globalen Zugriff, Navigation und Recherche im Gesamtdatenbestand ermöglichen. Die Modellierung und Verwaltung bauwerksbezogener Daten ist seit längerem Gegenstand diverser Forschungsarbeiten. Im Rahmen des SFB 524 wurde ein eigener Ansatz basierend auf einem laufzeitdynamischen Partialmodellverbund entwickelt. Dieser wird in den wesentlichen Grundzügen anderen Ansätzen gegenübergestellt. Den Schwerpunkt dieses Beitrags bildet jedoch die Entwicklung einer geeigneten flexiblen Navigations- und Rechercheschicht zu Realisierung projektglobaler Informationsrecherche. Aus der Sicht der Modellierung und Datenverwaltung wie auch aus der Sicht der Informationsrecherche und Informationspräsentation in Planungsprozessen ergeben sich verschiedene Anforderungen an derartige Recherchewerkzeuge, wobei der wesentlichste Grundsatz maximale Flexibilität hinsichtlich verfügbarer Darstellungstechniken und deren freie Kombination mit Techniken formaler Suchanfragen ist. Das entwickelte Systemkonzept basiert auf einem Framework, welches verschiedene Grundtypen von Recherchemodulen und deren Interaktionsprinzipien vorgibt. Einzelne Recherchemodule werden als Ausprägungen dieser Modultypen realisiert und können je nach Bedarf laufzeitdynamisch in die Navigationsschicht integriert werden. Die technische Realisierung des Systems erfolgt im Umfeld vorhandener Prototypen aus vorangegangenen Forschungsaktivitäten. Dieses technische Umfeld gibt verschiedene Rahmenbedingungen vor, welche im Vorfeld prototypischer Implementierungen verschiedene Adaptionen des generellen Systemkonzepts notwendig machen. Der vorliegende Beitrag stellt den aktuellen Entwicklungsstand der Systemlösung aus konzeptioneller und technischer Sicht sowie erste prototypische Realisierungen von Recherchemodulen vor.
Projector-based displays have been evolving tremendously in the last decade. Reduced costs and increasing capabilities have let to a widespread use for home entertainment and scientific visualization. The rapid development is continuing - techniques that allow seamless projection onto complex everyday environments such as textured walls, window curtains or bookshelfs have recently been proposed. Although cameras enable a completely automatic calibration of the systems, all previously described techniques rely on a precise mapping between projector and camera pixels. Global illumination effects such as reflections, refractions, scattering, dispersion etc. are completely ignored since only direct illumination is taken into account. We propose a novel method that applies the light transport matrix for performing an image-based radiometric compensation which accounts for all possible lighting effects. For practical application the matrix is decomposed into clusters of mutually influencing projector and camera pixels. The compensation is modeled as a linear equation system that can be solved separately for each cluster. For interactive compensation rates this model is adapted to enable an efficient implementation on programmable graphics hardware. Applying the light transport matrix's pseudo-inverse allows to separate the compensation into a computational expensive preprocessing step (computing the pseudo-inverse) and an on-line matrix-vector multiplication. The generalized mathematical foundation for radiometric compensation with projector-camera systems is validated with several experiments. We show that it is possible to project corrected imagery onto complex surfaces such as an inter-reflecting statuette and glass. The overall sharpness of defocused projections is increased as well. Using the proposed optimization for GPUs, real-time framerates are achieved.
We propose a novel method that applies the light transport matrix for performing an image-based radiometric compensation which accounts for all possible types of light modulation. For practical application the matrix is decomposed into clusters of mutually influencing projector and camera pixels. The compensation is modeled as a linear system that can be solved with respect to the projector patterns. Precomputing the inverse light transport in combination with an efficient implementation on the GPU makes interactive compensation rates possible. Our generalized method unifies existing approaches that address individual problems. Based on examples, we show that it is possible to project corrected images onto complex surfaces such as an inter-reflecting statuette, glossy wallpaper, or through highly-refractive glass. Furthermore, we illustrate that a side-effect of our approach is an increase in the overall sharpness of defocused projections.
Die meisten Insolvenzen in Deutschland kommen aus der Bauindustrie. Die Gründe hierfür sind vielschichtig, jedoch kann mittels eines modern ausgerichteten M-I-S und Baustellen-Controllings frühzeitig erkannt werden, wie sich die Baustellenergebnisse entwickeln. Hierzu ist es notwendig, dass die Arbeitskalkulation ständig auf dem Laufenden gehalten wird. Nur wenn dies geschieht, sind monatliche Soll-/ Ist-Vergleiche und eine Betrachtung der cost-to-complete möglich und sinnvoll. Eine monatlich rollierende Prognose des Baustellenergebnisses zum Bauende ermöglicht, dass gravierende Veränderungen des Ergebnisses umgehend aufgedeckt werden. Nur in Kenntnis dieser Entwicklungen kann das Management frühzeitig (im Sinne eines Frühwarnsystems) agieren und Steuerungsmaßnahmen ergreifen. Die Ergebnisprognose zum Bauende ist allein als Steuerungsinstrument nicht ausreichend. Die Finanzsituation der Baustelle muß auch regelmäßig geprüft werden, d.h. der Leistungsstand mit der Rechnungsstellung an den Bauherren abgeglichen sowie die unbezahlten Rechnungen des Bauherren überprüft werden. Das beste Prognoseergebnis ist wertlos, wenn der Bauherr seine bezogenen Leistungen nicht vergütet. Die wirtschaftlichen Daten stehen den Verantwortlichen online im Baustellen-Informations-System (B-I-S) zur Verfügung. Ein Ampelsystem verdeutlicht die wirtschaftliche Lage der Baustelle.
Subject of the paper is the realisation of a model based efficiency control system for PV generators using a simulation model. A standard 2-diodes model of PV generator is base of the ColSim model, which is implemented in ANSI C code for flexible code exporting. The algorithm is based on discretisized U-I characteristics, which allows the calculation of string topologies witch parallel and serial PV cells and modules. Shadowing effects can be modelled down to cell configuration using polar horizon definitions. The simulation model was ported to a real time environment, to calculate the efficiency of a PV system. Embedded System technology allows the networked operation and the integration of standard I/O devices. Futher work focus on the adaption of shadowing routine, which will be adapted to get the environment conditions from the real operation.
TOOL TO CHECK TOPOLOGY AND GEOMETRY FOR SPATIAL STRUCTURES ON BASIS OF THE EXTENDED MAXWELL'S RULE
(2006)
One of the simplest principle in the design of light-weight structures is to avoid bending. This can be achieved by dissolving girders into members acting purely in axial tension or compression. The employment of cables for the tensioned members leads to even lighter structures which are called cable-strut structures. They constitute a subclass of spatial structures. To give fast information about the general feasibility of an architectural concept employing cable-strut structures is a challenging task due to their sophisticated mechanical behavior. In this regard it is essential to control if the structure is stable and if pre-stress can be applied. This paper presents a tool using the spreadsheet software Microsoft (MS) Excel which can give such information. Therefore it is not necessary to purchase special software and the according time consuming training is much lower. The tool was developed on basis of the extended Maxwell's rule, which besides topology also considers the geometry of the structure. For this the rank of the node equilibrium matrix is crucial. Significance and determination of the rank and the implementation of the corresponding algorithms in MS Excel are described in the following. The presented tool is able to support the structural designer in an early stage of the project in finding a feasible architectural concept for cable-strut structures. As examples for the application of the software tool two special cable-strut structures, so called tensegrity structures, were examined for their mechanical behavior.
Analysis of the reinforced concrete chimney geometry changes and their influence on the stresses in the chimney mantle was made. All the changes were introduced to a model chimney and compared. Relations between the stresses in the mantle of the chimney and the deformations determined by the change of the chimney's vertical axis geometry were investigated. The vertical axis of chimney was described by linear function (corresponding to the real rotation of the chimney together with the foundation), and by parabolic function (corresponding to the real dislocation of the chimney under the influence of the horizontal forces - wind). The positive stress pattern in the concrete as well as the negative stress pattern in the reinforcing steel have been presented. The two cases were compared. Analysis of the stress changes in the chimney mantle depending on the modification in the thickness of the mantle (the thickness of the chimney mantle was altered in the linear or the abrupt way) was carried out. The relation between the stresses and the chimney's diameter change from the bottom to the top of the chimney was investigated. All the analyses were conducted by means of a specially developed computer program created in Mathematica environment. The program makes it also possible to control calculations and to visualize the results of the calculations at every stage of the calculation process.