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Structural Design (structural + design)
Selected AbstractsAnwendung von Trapezblechstegen im BrückenbauBETON- UND STAHLBETONBAU, Issue 9 2009Längsschubtragverhalten von Betondübeln in Kombination mit Trapezblechstegen Brückenbau; Entwurf und Konstruktion Abstract Trapezblechstege im Brückenbau kommen trotz der großen Vorteile, die diese Bauweise bietet, in Deutschland bisher nur an einem Pilotprojekt zur Anwendung. Durch die charakteristischen Eigenschaften des Trapezbleches entstehen konstruktive und wirtschaftliche Vorteile gegenüber herkömmlichen Brückenbauweisen. Allerdings lassen die aktuell gültigen Regelwerke aufgrund fehlender Kenntnis zum Tragverhalten und mangelnder Erfahrung keine wirtschaftliche Ausbildung zu. Dies zeigt sich am Beispiel des Pilotprojekts. Die Ausbildung der Verbundfuge wurde hier nur sehr unbefriedigend gelöst und verdeutlicht somit die Notwendigkeit einfacher und praktikabler Verbindungsmöglichkeiten. Am Institut für Leichtbau Entwerfen und Konstruieren der Universität Stuttgart wurde in Zusammenarbeit mit dem Institut für Konstruktion und Entwurf ein von der Forschungsvereinigung für Stahlanwendung e. V. (FOSTA) finanziertes Forschungsvorhaben bearbeitet, bei dem unterschiedliche Verbundfugenausbildungen numerisch und experimentell untersucht wurden. Der folgende Beitrag beschränkt sich auf die Verwendung von Betondübeln als Verbundmittel und stellt hierfür ein einfaches Bemessungskonzept für die Verbundsicherung unter Längsschubbeanspruchung im Grenzzustand der Tragfähigkeit vor. The use of corrugated steel webs in bridge constructions , Load bearing behaviour of concrete dowels in combination with corrugated steel webs under longitudinal shear Studies of the load bearing behaviour under shear force of integrated connections at composite bridge girders using corrugated steel webs. Up to now there is only one project in Germany, where the application of corrugated steel webs has been practiced in the field of composite bridges. Due to the characteristics of the corrugated steel web this construction method has constructive and economic advantages. However there is a lack of experiences and standards to fully utilize these advantages and to allow an economic application. Especially the first project in Germany expose some critical points. The design of the joint between the concrete slab and the corrugated steel web is actually not satisfactory and shows the need for simpler and more practicable connection methods. At the Institute for Lightweight Structures and Conceptual Design at Universität Stuttgart and together with the Institute of Structural Design, a research project, financed by Forschungsvereinigung für Stahlanwendung e. V. (FOSTA) was made. Within this project different types of composite joints were experimentally and numerically analysed. This paper deals only with the investigations of concrete dowels as connectors. On the basis of these studies simple design rules for shear connection in the ultimate limit state were developed. [source] Effect of Polarity and Structural Design on Molecular Photorefractive Properties of Heteroaromatic-Based Push,Pull DyesCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2006Graziano Archetti Dr. Abstract A combined experimental (optical and electro-optical absorption measurements) and computational (ab initio RHF and DFT) approach has been used to investigate the molecular low- and high- Tg photorefractive (PR) performances of neutral and zwitterionic heteroaromatic dipolar chromophores in terms of structural and solvent-polarity effects. We have found that the nature of the building units (donor, acceptor, and spacer) and the polarity of the surrounding medium strongly affect all the relevant ground-state and nonlinear optical properties involved in the PR activity, that is, the dipole moment, the polarizability anisotropy, and first hyperpolarizability of the electronic ground-state. The variation of these properties is in turn transferred to molecular low- and high- Tg PR figures of merit. It is shown that PR molecular performance not only relies on a proper choice of structural components but varies by orders of magnitude as a function of the medium polarity, and this suggests that a combination of molecular design and host-matrix engineering is required for optimized performances of PR materials. [source] Structural design of composite nonlinear feedback control for linear systems with actuator constraint,ASIAN JOURNAL OF CONTROL, Issue 5 2010Weiyao Lan Abstract The performance of the composite nonlinear feedback (CNF) control law relies on the selection of the linear feedback gain and the nonlinear function. However, it is a tough task to select an appropriate linear feedback gain and appropriate parameters of the nonlinear function because the general design procedure of CNF control just gives some simple guidelines for the selections. This paper proposes an operational design procedure based on the structural decomposition of the linear systems with input saturation. The linear feedback gain is constructed by two linear gains which are designed independently to stabilize the unstable zero dynamics part and the pure integration part of the system respectively. By investigating the influence of these two linear gains on transient performance, it is flexible and efficient to design a satisfactory linear feedback gain for the CNF control law. Moreover, the parameters of the nonlinear function are tuned automatically by solving a minimization problem. The proposed design procedure is illustrated by applying it to design a tracking control law for the inverted pendulum on a cart system. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] Topology Design of Truss Structures in a Multicriteria EnvironmentCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2001Won-Sun Ruy As an analogy of the general design process, this article presents a novel design approach that could generate structural design alternatives having different topologies and then select the optimal structures from them together with simultaneously determining the optimal design variables related to geometry and member size subjected to a multiple objective design environment. For this purpose, a specialized genetic algorithm, called StrGA_DeAl+MOGA, that can handle the design alternatives and multicriteria problems very effectively is developed for the optimal structural design. To validate the developed method, plain-truss design problems are considered as illustrative examples. To begin with, the promising topologies are generated under the name of "design alternatives" with consideration of the given multiobjective environment. Based on the selected topology of truss structures, the sizing or geometric optimization process starts to determine the optimal design parameters. Three-bar and ten-bar truss problems are treated in the article to test the concept and methodology. [source] Does amplitude scaling of ground motion records result in biased nonlinear structural drift responses?EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2007Nicolas Luco Abstract Limitations of the existing earthquake ground motion database lead to scaling of records to obtain seismograms consistent with a ground motion target for structural design and evaluation. In the engineering seismology community, acceptable limits for ,legitimate' scaling vary from one (no scaling allowed) to 10 or more. The concerns expressed by detractors of scaling are mostly based on the knowledge of, for example, differences in ground motion characteristics for different earthquake magnitude,distance (Mw,Rclose) scenarios, and much less on their effects on structures. At the other end of the spectrum, proponents have demonstrated that scaling is not only legitimate but also useful for assessing structural response statistics for Mw,Rclose scenarios. Their studies, however, have not investigated more recent purposes of scaling and have not always drawn conclusions for a wide spectrum of structural vibration periods and strengths. This article investigates whether scaling of records randomly selected from an Mw,Rclose bin (or range) to a target fundamental-mode spectral acceleration (Sa) level introduces bias in the expected nonlinear structural drift response of both single-degree-of-freedom oscillators and one multi-degree-of-freedom building. The bias is quantified relative to unscaled records from the target Mw,Rclose bin that are ,naturally' at the target Sa level. We consider scaling of records from the target Mw,Rclose bin and from other Mw,Rclose bins. The results demonstrate that scaling can indeed introduce a bias that, for the most part, can be explained by differences between the elastic response spectra of the scaled versus unscaled records. Copyright © 2007 John Wiley & Sons, Ltd. [source] The role of soil in the collapse of 18 piers of Hanshin Expressway in the Kobe earthquakeEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2006George Mylonakis Abstract An investigation is presented of the collapse of a 630 m segment (Fukae section) of the elevated Hanshin Expressway during the 1995 Kobe earthquake. The earthquake has, from a geotechnical viewpoint, been associated with extensive liquefactions, lateral soil spreading, and damage to waterfront structures. Evidence is presented that soil,structure interaction (SSI) in non-liquefied ground played a detrimental role in the seismic performance of this major structure. The bridge consisted of single circular concrete piers monolithically connected to a concrete deck, founded on groups of 17 piles in layers of loose to dense sands and moderate to stiff clays. There were 18 spans in total, all of which suffered a spectacular pier failure and transverse overturning. Several factors associated with poor structural design have already been identified. The scope of this work is to extend the previous studies by investigating the role of soil in the collapse. The following issues are examined: (1) seismological and geotechnical information pertaining to the site; (2) free-field soil response; (3) response of foundation-superstructure system; (4) evaluation of results against earlier studies that did not consider SSI. Results indicate that the role of soil in the collapse was multiple: First, it modified the bedrock motion so that the frequency content of the resulting surface motion became disadvantageous for the particular structure. Second, the compliance of soil and foundation altered the vibrational characteristics of the bridge and moved it to a region of stronger response. Third, the compliance of the foundation increased the participation of the fundamental mode of the structure, inducing stronger response. It is shown that the increase in inelastic seismic demand in the piers may have exceeded 100% in comparison with piers fixed at the base. These conclusions contradict a widespread view of an always-beneficial role of seismic SSI. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ordered Mesoporous Silica Derived from Layered SilicatesADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Tatsuo Kimura Abstract Here, the development of ordered mesoporous silica prepared by the reaction of layered silicates with organoammonium surfactants is reviewed. The specific features of mesoporous silica are discussed with relation to the probable formation mechanisms. The recent understanding of the unusual structural changes from the 2D structure to periodic 3D mesostructures is presented. The formation of mesophase silicates from layered silicates with single silicate sheets depends on combined factors including the reactivity of layered silicates, the presence of layered intermediates, the variation of the silicate sheets, and the assemblies of surfactant molecules in the interlayer spaces. FSM-16-type (p6mm) mesoporous silica is formed via layered intermediates composed of fragmented silicate sheets and alkyltrimethylammonium (CnTMA) cations. KSW-2-type (c2mm) mesoporous silica can be prepared through the bending of the individual silicate sheets with intralayer and interlayer condensation. Although the structure of the silicate sheets changes during the reactions with CnTMA cations in a complex manner, the structural units caused by kanemite in the frameworks are retained. Recent development of the structural design in the silicate framework is very important for obtaining KSW-2-based mesoporous silica with molecularly ordered frameworks. The structural units originating from layered silicates are chemically designed and structurally stabilized by direct silylation of as-synthesized KSW-2. Some proposed applications using these mesoporous silica are also summarized with some remarks on the uniqueness of the use of layered silicates by comparison with MCM-type mesoporous silica. [source] Fabrication and Electromechanical Characterization of a Piezoelectric Structural Fiber for Multifunctional CompositesADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Yirong Lin Abstract The use of piezoceramic materials for structural sensing and actuation is a fairly well developed practice that has found use in a wide variety of applications. However, just as advanced composites offer numerous benefits over traditional engineering materials for structural design, actuators that utilize the active properties of piezoelectric fibers can improve upon many of the limitations encountered when using monolithic piezoceramic devices. Several new piezoelectric fiber composites have been developed; however, almost all studies have implemented these devices such that they are surface-bonded patches used for sensing or actuation. This paper will introduce a novel active piezoelectric structural fiber that can be laid up in a composite material to perform sensing and actuation, in addition to providing load bearing functionality. The sensing and actuation aspects of this multifunctional material will allow composites to be designed with numerous embedded functions, including structural health monitoring, power generation, vibration sensing and control, damping, and shape control through anisotropic actuation. This effort has developed a set of manufacturing techniques to fabricate the multifunctional fiber using a SiC fiber core and a BaTiO3 piezoelectric shell. The electromechanical coupling of the fiber is characterized using an atomic force microscope for various aspect ratios and is compared to predictions made using finite element modeling in ABAQUS. The results show good agreement between the finite element analysis model and indicate that the fibers could have coupling values as high as 68% of the active constituent used. [source] Why Is the Intelligence Community So Difficult to Redesign?GOVERNANCE, Issue 3 2007Conflicting Goals, Smart Practices, the Creation of Purpose-Based Organizations The adoption of "smart practices" requires that smart practices can actually be identified for the areas of public policy in which we are interested. For the problem of designing structures for public agencies, however, identifying smart practices is not easy. This article explores the reasons for the substantial conservativism, lasting over 50 years, regarding the structural design of the U.S. intelligence community. One central argument is simply that it was very difficult to discover a clearly superior structure; in fact, the long-standing structure may have had some unrecognized virtues. But the other central argument is that one smart practice may have emerged since the 9/11 attacks: It involves the creation of problem-focused interagency centers that are intended to enhance the sharing and integration of information within the intelligence community. These conclusions about redesigning the structure of the intelligence community are based on the arguments of Luther Gulick on methods of departmentalization and Martin Landau on redundancy and system reliability. [source] Designed Synthesis of Coaxial SnO2@carbon Hollow Nanospheres for Highly Reversible Lithium StorageADVANCED MATERIALS, Issue 24 2009Xiong Wen Lou A proof-of-concept structural design is demonstrated for high-capacity lithium-ion batteries anode materials by multistep synthesis of coaxial SnO2@carbon hollow nanospheres. This material integrates two beneficial features: hollow structure and carbon nanopainting. When evaluated for reversible lithium storage, these functional materials manifest excellent cycling performance and rate capabilities. [source] An improved perturbation method for stochastic finite element model updatingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2008X. G. Hua Abstract In this paper, an improved perturbation method is developed for the statistical identification of structural parameters by using the measured modal parameters with randomness. On the basis of the first-order perturbation method and sensitivity-based finite element (FE) model updating, two recursive systems of equations are derived for estimating the first two moments of random structural parameters from the statistics of the measured modal parameters. Regularization technique is introduced to alleviate the ill-conditioning in solving the equations. The numerical studies of stochastic FE model updating of a truss bridge are presented to verify the improved perturbation method under three different types of uncertainties, namely natural randomness, measurement noise, and the combination of the two. The results obtained using the perturbation method are in good agreement with, although less accurate than, those obtained using the Monte Carlo simulation (MCS) method. It is also revealed that neglecting the correlation of the measured modal parameters may result in an unreliable estimation of the covariance matrix of updating parameters. The statistically updated FE model enables structural design and analysis, damage detection, condition assessment, and evaluation in the framework of probability and statistics. Copyright © 2007 John Wiley & Sons, Ltd. [source] Jaques and the early years in AustraliaINTERNATIONAL JOURNAL OF APPLIED PSYCHOANALYTIC STUDIES, Issue 4 2005Sir Roderick Carnegie Abstract The Chief Executive Officer (CEO) of any organization, by the nature of his or her title and role, sets the culture (the "how we do things around here") which becomes either paranoiagenic or trust-inducing to greater or lesser extremes. This account of one CEO emphasizes the relationships between past managerial experiences, the business requirements of a highly competitive industry, the nature of the impact of local government on globally dispersed installations, and an intense interest in bringing together a better understanding of trust-inducing top-down managerial leadership. Thus follows an examination of one CEO's journey with a nascent body of research and the researcher as, together, they struggle with understanding what requirements and actions will be interpreted as not only "good for the company" but also "good for me" as an employee. The paper describes the added value of a CEO's systematic organizational analysis and structural design of a managerial work system focused on the employment of the discretion and judgment of each employee within appropriate role boundaries, thereby inserting a large amount of psychologically sound, creative problem-solving focused on competitive business outcomes. It develops understanding of the business reasons for fair pay for levels of work assigned, and the recognition of current potential capability and development of individuals as they naturally mature in future potential capability to handle more complex assignments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Construction of the Femoral Neck During Growth Determines Its Strength in Old Age,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2007Roger M D Zebaze Abstract Study of the design of the FN in vivo in 697 women and in vitro in 200 cross-sections of different sizes and shapes along each of 13 FN specimens revealed that strength in old age was largely achieved during growth by differences in the distribution rather than the amount of bone material in a given FN cross-section from individual to individual. Introduction: We studied the design of the femoral neck (FN) to gain insight into the structural basis of FN strength in adulthood and FN fragility in old age. Materials and Methods: Studies in vivo were performed using densitometry in 697 women and in vitro using high-resolution ,CT and direct measurements in 13 pairs of postmortem specimens. Results: The contradictory needs of strength for loading yet lightness for mobility were met by varying FN size, shape, spatial distribution, and proportions of its trabecular and cortical bone in a cross-section, not its mass. Wider and narrower FNs were constructed with similar amounts of bone material. Wider FNs were relatively lighter: a 1 SD higher FN volume had a 0.67 (95% CI, 0.61,0.72) SD lower volumetric BMD (vBMD). A 1 SD increment in height was achieved by increasing FN volume by 0.32 (95% CI, 0.25,0.39) SD with only 0.15 (95% CI, 0.08,0.22) SD more bone, so taller individuals had a relatively lighter FN (vBMD was 0.13 [95% CI, 0.05,0.20 SD] SD lower). Greater periosteal apposition constructing a wider FN was offset by even greater endocortical resorption so that the same net amount of bone was distributed as a thinner cortex further from the neutral axis, increasing resistance to bending and lowering vBMD. This was recapitulated at each point along the FN; varying absolute and relative degrees of periosteal apposition and endocortical resorption focally used the same amount of material to fashion an elliptical FN of mainly cortical bone near the femoral shaft to offset bending but a more circular FN of proportionally more trabecular and less cortical bone to accommodate compressive loads adjacent to the pelvis. This structural heterogeneity was largely achieved by adaptive modeling and remodeling during growth,most of the variance in FN volume, BMC, and vBMD was growth related. Conclusions: Altering structural design while minimizing mass achieves FN strength and lightness. Bone fragility may be the result of failure to adapt bone's architecture to loading, not just low bone mass. [source] Development of High Strength Magnesium Based MMC Reinforced with SiC Particles for Satellite Structure ApplicationsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2003B. Landkof Abstract The appearance of Metal Matrix Composites has opened a new area in structural design. The possibility of tailoring mechanical properties of structural metals reinforced with particles or fibers into specific spacecraft applications is very appealing. This paper deals with such a MMC, which is based on a magnesium alloy matrix and SiC reinforcement. The technology used is a commercial semi-solid die-casting, which promises a cost-effective solution. The results of the first stage of this research are discussed with a focus on the satellite structure design application. The next steps of this investigation are also presented. [source] Comparative study between laser performance and carrier lifetime of 400 nm emitting GaInN/GaN laser diodesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003C. Netzel Abstract GaInN/GaN laser diodes with different laser performance but nearly identical structural design, all emitting at around 400 nm, were investigated with time-resolved and temperature-dependent photoluminescence under pulsed excitation and with temperature- and power-dependent photoluminescence under cw excitation. To compare the laser diodes with LEDs, the same measurements were performed for an LED structure emitting in the same spectral region. The time-resolved photoluminescence as well as the measurements under continuous excitation point at a more efficient nonradiative recombination for laser structures. This enhancement of nonradiative recombination for the laser diodes was observed to be most pronounced for the best laser diodes. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Dachentwässerungen im Zuge geänderter normativer Anforderungen und sich ändernder klimatischer Einwirkungen , eine Planungsaufgabe?BAUPHYSIK, Issue 2 2008Jörg Röder Dr.-Ing. Die Dach- und Gebäudeentwässerung soll für den schadenfreien Abfluss des Regenwassers sorgen. Die planmäßige Dachentwässerung wird dabei "nur" für einen mittleren Regen ausgelegt. Schäden durch stärkere Regenereignisse sollen vermieden werden, indem die Möglichkeit einer Notentwässerung vorgesehen wird. Die Notentwässerung und die Sicherstellung der Funktionstüchtigkeit der Dachentwässerung durch eine regelmäßige Wartung stellen die Hauptanforderungen an Dach- und Gebäudeentwässerungen dar. Die Planung und Bemessung von Rinnen und Fallleitungen erfolgt mit der neuen Normengeneration erstmals unter Verwendung hydraulischer Bemessungsgrundlagen und statistisch abgesicherter Regenspenden. Dennoch zeigen Fallbeispiele, dass der Planung und Bemessung von Dach- und Gebäudeentwässerungen zu wenig Aufmerksamkeit geschenkt wird. Die Folge sind nicht selten Wasserschäden an der Konstruktion. Eine Analyse der Bemessungsverfahren verdeutlicht, dass auch in diesem sensiblen Bereich der Gebäudekonstruktion , im Gegensatz zur statischen Bemessung von Bauteilen , i. d. R. keine Sicherheiten vorgesehen sind. Diese wären jedoch im Zuge sich abzeic hnender Klimaveränderungen u. a. zur Vermeidung von Überbeanspruchungen und Schäden durchaus sinnvoll. Roof drainage in the course of changed regulation require-ments and changed climatic influences , a planning task? The roof and building drainage is supposed to take over the flaw-less drain of rain water. Still, the roof drainage as planned is "only" designed for a rain of medium intensity. In order to prevent damages through rain of stronger intensity the possibility of an emergency drainage will be planned. The emergency drainage and the ensured roof drainage by regular maintenance are the main drainage requirements. With the new regulation generation, planning and structural design of gutters and fall pipes are first done using basis for assessment of hydraulic nature and statistically backed up rain fall data. Nevertheless, case studies show that there is not enough attention given to the planning and design of roof and building drainage. Not uncommon, the result is water damage to the structure. An analysis of the design method shows that even in this sensitive field of building construction , in opposition to static dimensioning of components , there are usually no safeties planned. However, on the tide of the evolving climatic changes, this would make sense inter alia to prevent overloading and damages. [source] Sonderlösungen bei der Tragwerksplanung auf der Grundlage der neuen Normen , Klimatische EinwirkungenBAUTECHNIK, Issue 3 2005Hans-Jürgen Niemann Prof. em. Der folgende Beitrag befaßt sich mit den klimatischen Einwirkungen auf weit gespannte Dächer. Im Zentrum stehen die Windlasten. Die Angaben der Norm lassen sich durch Sonderuntersuchungen zuschärfen, soweit die Regelungen das nahe legen und der zusätzliche Aufwand gerechtfertigt ist. Das gilt sowohl für das Windklima am Bauwerksstandort als auch für die aerodynamischen Beiwerte, für die im allgemeinen Windkanalversuche die Grundlage bilden. In einer neuen Norm, der DIN 1055 Teil 100: "Grundlagen der Tragwerksplanung, Sicherheitskonzept und Bemessungsregeln", werden erstmalig die Anforderungen an die Tragsicherheit und Gebrauchstauglichkeit einer Konstruktion formuliert und festgelegt. Sie definiert die Lastannahmen als Teil des Sicherheitskonzepts, legt die Anforderungen an das Lastniveau fest und bestimmt so die Spielräume für eine Zuschärfung der Lastannahmen durch Sonderuntersuchungen für ein bestimmtes Bauprojekt. Hinzu kommen einzelne Öffnungsklauseln, die in den Normen für Wind- und Schneelasten vorgesehen sind. Der Beitrag stellt die Rahmenbedingungen für eine Optimierung der Lastannahmen dar. Special solutions in structural design on the basis of the new design codes , climatic actions. The following contribution deals with climatic actions on large lightweight roofs of stadia. The focus is on the wind loads. In some cases, it becomes necessary or advantageous to provide more precise design wind loads compared to the code provisions. This applies to the local wind climate as well as to the aerodynamic coefficients. The framework for such investigations is established by the requirements set by the code DIN 1055-100: Basis of design, with regard to structural safety and reliability, and by those basic stipulations in the wind loading code which may not be altered. The author presents and discusses the framework for optimised design wind loads. [source] Untersuchung zur Erddruckbeanspruchung von WinkelstützwändenBAUTECHNIK, Issue 12 2004Martin Achmus Univ.-Prof. Die Bemessung des vertikalen Schenkels von Winkelstützwänden ist gemäß derzeitiger deutscher Normung für erhöhten Erddruck, d. h. den Mittelwert aus aktivem Erddruck und Erdruhedruck, vorzunehmen. Dieser Ansatz liegt, wie im vorliegenden Aufsatz gezeigt wird, in vielen Fällen deutlich auf der sicheren Seite. Mittels einer numerischen Parameterstudie werden die wesentlichen Einflußfaktoren aufgezeigt. Auf der Grundlage der Ergebnisse wird ein Verfahren vorgeschlagen, das die genauere Festlegung der Erddrucklast unter Berücksichtigung der wesentlichen Einflußgrößen in einfacher Weise ermöglicht. Investigation on the earth pressure loading of L-shaped retaining walls. Due to current German regulations the structural design of the vertical wall stem of L-shaped retaining walls is based on the assumption of increased earth pressure loading, i.e. the average of active earth pressure and earth pressure at rest. In the presented paper it is shown that with this approach the resultant loading is in most cases overestimated. The influence of the most important parameters is investigated by a numerical model. Based on the results, a simple method for a more accurate estimation of the resultant loading is proposed. [source] Anwendung der neuen Stahlbetonnormen für die Bemessung von TunnelinnenschalenBETON- UND STAHLBETONBAU, Issue 2 2004Bruno Mattle Dipl.-Ing. Abstract Die in den letzten Jahren in der Bundesrepublik Deutschland und in Österreich errichteten Verkehrstunnel wurden i. a. zweischalig, d. h. mit einer Spritzbetonaußenschale und einer Innenschale aus unbewehrtem Beton oder Stahlbeton hergestellt. Die Bemessung der Innenschalen erfolgte unter Anwendung der Normen DIN 1045 [1] und ÖN B 4200 [2]. Während die neuen Normen wie EC 2 [3], DIN 1045-1 [4] und ÖN B 4700 [5] im Hochbau schon seit längerem Anwendung finden, ist deren Anwendung für die Bemessung von Tunnelschalen im wesentlichen noch Neuland. Dies betrifft insbesondere die Anwendung des Teilsicherheitskonzeptes und die Möglichkeit, die Schnittgrößen unter Anwendung nichtlinearer Stoffgesetze zu ermitteln. Im vorliegenden Beitrag wird die Problematik dargestellt und anhand von Beispielen der Einfluß unterschiedlicher Annahmen aufgezeigt. Design of Final Tunnel Linings according to the new Codes for Reinforced Concrete The traffic tunnels which have been constructed during the last few years in Germany and Austria in general have an initial shotcrete lining and a final, cast in place reinforced or unreinforced concrete lining. The structural design of the final linings has been based on specific standards from the clients and on the national codes DIN 1045 [1] and ÖN B 4200 [2]. While the new codes EC 2 [3], DIN 1045-1 [4] and ÖN B 4200 [5] have been widely used for the structural design of buildings for a while, their application for the design of tunnel linings is more or less a new field. In particular this is valid for using nonlinear material laws and the partial safety factor concept. In the presented paper this topic is discussed and the consequences of different assumptions are shown on specific examples. [source] A Tale of Two Targets: Differential RNA Selectivity of Nucleobase,Aminoglycoside ConjugatesCHEMBIOCHEM, Issue 10 2006Kenneth F. Blount Dr. Aminoglycoside antibiotics are RNA-binding polyamines that can bind with similar affinities to structurally diverse RNA targets. To design new semisynthetic aminoglycosides with improved target selectivity, it is important to understand the energetic and structural basis by which diverse RNA targets recognize similar ligands. It is also imperative to discover how novel aminoglycosides could be rationally designed to have enhanced selectivity for a given target. Two RNA drug targets, the prokaryotic ribosomal A-site and the HIV-1 TAR, provide an excellent model system in which to dissect the issue of target selectivity, in that they each have distinctive interactions with aminoglycosides. We report herein the design, synthesis, and binding activity of novel nucleobase,aminoglycoside conjugates that were engineered to be more selective for the A-site binding pocket. Contrary to the structural design, the conjugates bind the A-site more weakly than does the parent compound and bind the TAR more tightly than the parent compound. This result implies that the two RNA targets differ in their ability to adapt to structurally diverse ligands and thus have inherently different selectivities. This work emphasizes the importance of considering the inherent selectivity traits of the RNA target when engineering new ligands. [source] | |||||||||||||||||||||||||||||||