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Bridge Structures (bridge + structure)
Selected AbstractsPost-earthquake bridge repair cost and repair time estimation methodologyEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2010Kevin R. Mackie Abstract While structural engineers have traditionally focused on individual components (bridges, for example) of transportation networks for design, retrofit, and analysis, it has become increasingly apparent that the economic costs to society after extreme earthquake events are caused at least as much from indirect costs as direct costs due to individual structures. This paper describes an improved methodology for developing probabilistic estimates of repair costs and repair times that can be used for evaluating the performance of new bridge design options and existing bridges in preparation for the next major earthquake. The proposed approach in this paper is an improvement on previous bridge loss modeling studies,it is based on the local linearization of the dependence between repair quantities and damage states so that the resulting model follows a linear relationship between damage states and repair points. The methodology uses the concept of performance groups (PGs) that account for damage and repair of individual bridge components and subassemblies. The method is validated using two simple examples that compare the proposed method to simulation and previous methods based on loss models using a power,law relationship between repair quantities and damage. In addition, an illustration of the method is provided for a complete study on the performance of a common five-span overpass bridge structure in California. Intensity-dependent repair cost ratios (RCRs) and repair times are calculated using the proposed approach, as well as plots that show the disaggregation of repair cost by repair quantity and by PG. This provides the decision maker with a higher fidelity of data when evaluating the contribution of different bridge components to the performance of the bridge system, where performance is evaluated in terms of repair costs and repair times rather than traditional engineering quantities such as displacements and stresses. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis and thermal crosslinking of oxazolidine-functionalized polyurethanesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2007Robert Andreu Abstract A new oxazolidine derivative was obtained from phenol, 2-amino-2-methylpropane-1,3-diol and paraformaldehyde. The reaction of this novel oxazolidine diol with phenylisocyanate lead to a urethane model compound which can be polymerized thermally by oxazolidine ring opening to give a Mannich bridge structure. Linear segmented polyurethanes were prepared by reaction of different ratios of oxazolidine diol and commercial polyethylenglycol (Mw , 400) with 4,4,-methylenbis (cyclohexylisocyanate) (HMDI, 90% isomers mixture). The polyurethanes were thermally characterized and crosslinked by oxazolidine ring opening to obtain materials which showed improved thermal stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4965,4973, 2007 [source] Condition Assessment by Visual Inspection for a Bridge Management SystemCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2005Vincenzo Gattulli This article deals with a procedure for bridge condition assessment by visual inspection developed during the planning and preliminary design of the BMS for the public railway networks in Italy. The main modules adopted in the procedure are: bridge inventory, computer-aided visual inspection, automated defect catalog, and priority-ranking procedure. The probabilistic models used to calibrate the condition evaluation algorithm are discussed. Different levels of deficiency have been individuated for each class of bridge structure belonging to the managed stock. The procedure allows comparison and relative ranking of deficiency conditions across different types of bridge structures. The results of a visual inspection campaign conducted for a set of bridges with different structural characteristics are reported and evaluated within the framework of the developed BMS. [source] Response simulation and seismic assessment of highway overcrossingsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2010Anastasios Kotsoglou Abstract Interaction of bridge structures with the adjacent embankment fills and pile foundations is generally responsible for response modification of the system to strong ground excitations, to a degree that depends on soil compliance, support conditions, and soil mass mobilized in dynamic response. This paper presents a general modeling and assessment procedure specifically targeted for simulation of the dynamic response of short bridges such as highway overcrossings, where the embankment soil,structure interaction is the most prevalent. From previous studies it has been shown that in this type of interaction, seismic displacement demands are magnified in the critical bridge components such as the central piers. This issue is of particular relevance not only in new design but also in the assessment of the existing infrastructure. Among a wide range of issues relevant to soil,structure interaction, typical highway overcrossings that have flexible abutments supported on earth embankments were investigated extensively in the paper. Simulation procedures are proposed for consideration of bridge-embankment interaction effects in practical analysis of these structures for estimation of their seismic performance. Results are extrapolated after extensive parametric studies and are used to extract ready-to-use, general, and parameterized capacity curves for a wide range of possible material properties and geometric characteristics of the bridge-embankment assembly. Using two instrumented highway overpasses as benchmark examples, the capacity curves estimated using the proposed practical procedures are correlated successfully with the results of explicit incremental dynamic analysis, verifying the applicability of the simple tools developed herein, in seismic assessment of existing short bridges. Copyright © 2009 John Wiley & Sons, Ltd. [source] Seismic design of bridges accounting for spatial variability of ground motionEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4-5 2005A. Lupoi Abstract The effects of the spatial variability of the ground motion on the response of bridge structures are investigated in this study. Following a well-established convention, the phenomenon is represented as the combined effect of three causes: the loss of coherence of the motion with distance, the wave-passage, and the local site conditions. Since the nature and amount of non-synchronism vary within ample limits a statistical approach is adopted. A parametric study is carried out on a representative set of bridges subjected to carefully selected combinations of the factors inducing spatial variability. The investigation has shown that the phenomenon affects the response considerably and, hence, the level of protection of these structures. It is observed that for all bridge types considered, the ductility demands at the base of the piers in the presence of spatial variability increase in the majority of cases. Further, for a given bridge type, the probabilities of failure vary by more than one order of magnitude depending on the combination of the parameters. Attention has been focused on a parameter representing the ratio between the maximum curvature ductility demand and the same quantity for the case of fully synchronous motion. This parameter has been used to correct the conventional synchronous design procedure by increasing the available ductility. The re-analysis of all the cases with a modified ductility capacity shows that the procedure is effective in reducing the fragilities to the values corresponding to synchronous input. Copyright © 2005 John Wiley & Sons, Ltd. [source] Seismic performance evaluation of steel arch bridges against major earthquakes.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2004Part 1: dynamic analysis approach Abstract In this study the inelastic behavior of steel arch bridges subjected to strong ground motions from major earthquakes is investigated by dynamic analyses of a typical steel arch bridge using a three-dimensional (3D) analytical model, since checking seismic performance against severe earthquakes is not usually performed when designing such kinds of bridge. The bridge considered is an upper-deck steel arch bridge having a reinforced concrete (RC) deck, steel I-section girders and steel arch ribs. The input ground motions are accelerograms which are modified ground motions based on the records from the 1995 Hyogoken-Nanbu earthquake. Both the longitudinal and transverse dynamic characteristics of the bridge are studied by investigation of time-history responses of the main parameters. It is found that seismic responses are small when subjected to the longitudinal excitation, but significantly large under the transverse ground motion due to plasticization formed in some segments such as arch rib ends and side pier bases where axial force levels are very high. Finally, a seismic performance evaluation method based on the response strain index is proposed for such steel bridge structures. Copyright © 2004 John Wiley & Sons, Ltd. [source] A new approach to solving problems of multi-state system reliability optimizationQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 2 2001Gregory Levitin Abstract Usually engineers try to achieve the required reliability level with minimal cost. The problem of total investment cost minimization, subject to reliability constraints, is well known as the reliability optimization problem. When applied to multi-state systems (MSS), the system has many performance levels, and reliability is considered as a measure of the ability of the system to meet the demand (required performance). In this case, the outage effect will be essentially different for units with different performance rate. Therefore, the performance of system components, as well as the demand, should be taken into account. In this paper, we present a technique for solving a family of MSS reliability optimization problems, such as structure optimization, optimal expansion, maintenance optimization and optimal multistage modernization. This technique combines a universal generating function (UGF) method used for fast reliability estimation of MSS and a genetic algorithm (GA) used as an optimization engine. The UGF method provides the ability to estimate relatively quickly different MSS reliability indices for series-parallel and bridge structures. It can be applied to MSS with different physical nature of system performance measure. The GA is a robust, universal optimization tool that uses only estimates of solution quality to determine the direction of search. Copyright © 2001 John Wiley & Sons, Ltd. [source] Zur maßgebenden Verkehrslaststellung bei SchrägseilbrückenBAUTECHNIK, Issue 4 2004Harald Unterweger ao. Als Grundlage der Bemessung erfordert die Systemberechnung im Brükkenbau auch die Auffindung der ungünstigsten Verkehrslaststellung für jeden betrachteten Brückenquerschnitt. Insbesondere beim Fahrbahnbalken von Schrägseilbrücken ergibt sich die Gesamtbeanspruchung aus einem komplexen Zusammenwirken aus Normalkräften, Querkräften und Biegemomenten. In der Praxis erfolgt üblicherweise eine Selektion jener Verkehrslaststellungen, die eine der Teil beanspruchungen am Querschnitt (meist ausgedrückt durch Schnittkräfte) maximieren, wodurch jedoch für die nachfolgend betrachteten Stahl- bzw. Verbundbrücken nicht immer die höchsten Beanspruchungen entstehen. Einleitend erfolgt die Darstellung eines einfachen und anschaulichen Verfahrens, um , unabhängig von der Komplexität der Grenzzustandsfunktion, die auch das Beulen des Hauptträgerstegs beinhalten kann , die ungünstigste Verkehrslaststellung am Querschnitt zu finden. Dies stellt eine Verallgemeinerung des in [1] vorgestellten Verfahrens dar. Der Hauptteil beinhaltet ein Anwendungsbeispiel einer Schrägseilbrücke mit Verbundquerschnitt, wobei zwei repräsentative Fahrbahnquerschnitte näher untersucht werden. Einerseits werden die Gesamtbeanspruchungen der konventionellen und der genauen Vorgehensweise anhand von Einflußlinien erläutert, und andererseits lassen sich daraus Hinweise für die Praxis ableiten. Die dargestellte ingenieurmäßige Vorgehensweise kann alle Arten der Einwirkungen beinhalten und ist grundsätzlich auch auf andere Bauwerke sowie Baustoffe (z. B. Stahlbeton) direkt anwendbar. Appropriate traffic load cases for steel and composite cable , stayed bridges. A significant problem in the global analysis of bridge structures is to find the most unfavourable position of the traffic loads for each cross-section. In practice usually those traffic load cases are chosen which maximise one part of stresses at the cross-section (often expressed in form of internal forces). First of all a simple method is presented to find out the most unfavourable traffic load position, also applicable for complex interaction formulae including web buckling. Secondly an example of a cable-stayed bridge is analysed. For two significant sections of the bridge deck the results are presented. The stresses due to the conventional practical procedure are compared with the more accurate ones. The behaviour is explained by the corresponding influence lines. Based on these results some proposals for practical work are given. The presented procedure is also applicable to other types of construction works and materials (e.g. reinforced concrete). [source] Anpassung des Verkehrslastmodells des DIN FB 101 für kommunale BrückenBETON- UND STAHLBETONBAU, Issue 5 2007Balthasar Novák Prof. Dr.-Ing. Für den Verantwortungsbereich des BMVBS ist das kürzlich eingeführte Lastmodell LM1 für die Verkehrslasten auf Brücken ohne weitere Reduktionen für alle neuen Brückenbauwerke anzusetzen. Dies führt jedoch leider gerade im Bereich der Kommunen zu teilweise konservativen Ergebnissen, da die geometrischen Abmessungen von kommunalen Brücken deutlich von den "üblichen" Abmessungen von Autobahnen und Bundesstraßen abweichen können und die Belastung aus dem LM1 durch den realen Verkehr nicht erzeugt werden kann. Es werden Vorschläge präsentiert, wie bei bestimmten geometrischen Randbedingungen und abhängig vom statischen System eine weitere Abminderung des LM1 möglich ist, ohne das Sicherheitsniveau zu verlassen. Die Arbeit entstand in enger Zusammenarbeit mit den Städten Frankfurt/Main, Leipzig und Stuttgart. Adjusted Traffic Load for Bridges under Communal Responsibility Recently the traffic loads of bridges of the EC1 have been introduced in Germany under the responsibility of the Federal Ministry of Transport, Building and Urban Affairs. Usually the Load Model LM1 has to be used for all new bridge structures with the adjusted values of ,Q1 = 0, 8, ,Q2 = 0, 8, ,Q3 = 0. A further classification has not been defined. This makes sense for the highway bridges and federal road bridges, because usually they have longer spans where a further reduction of the ,-values is not justified. In the sphere of influence of cities and villages the situation is totally different, because many bridges are short and are buildt as single span girder bridges or single frame bridges. In case of those bridges the LM1 leads to conservative results because the geometry and the total weight and the axle weight of the real lorries are limited and cannot develop those high inner forces and moments. The authors developed a proposal for further reduction of the ,-values dependent on the geometry and the statical system of the bridge without leaving the safety level of the Eurocode. Also for strengthening existing bridges these values can be used. The development has been undertaken in colaboration with the civil engineering offices in Frankfurth/Main, Leipzig and Stuttgart. [source] Bemessung von Umlenkstellen externer Spannglieder: Finite-Element-Untersuchungen und BemessungsverfahrenBETON- UND STAHLBETONBAU, Issue 3 2005Josef Hegger Prof. Dr.-Ing. Die sorgfältige Bemessung und Konstruktion von Verankerungs- und Umlenkstellen ist Voraussetzung für sichere und dauerhafte Brückenbauwerke mit externer Vorspannung. Für die Bemessung von Umlenkstellen liegen allerdings nur wenige wissenschaftliche Erkenntnisse vor. Nachfolgend wird über Untersuchungen zur Beanspruchung von Umlenkkonstruktionen berichtet. Dabei ist auch die Beanspruchung des umgebenden Hohlkastenquerschnitts Gegenstand der Betrachtung. Anhand von Finite-Element-Untersuchungen wird ein einfaches Bemessungsmodell für Umlenkeckkonsolen hergeleitet. The Design of Deviators for External Tendons Thoroughly designed anchorage and deviation points are a basic requirement for reliable and durable bridge structures with external prestressing. In the past only little research has been made in the field of deviation of external tendons. Therefore investigations on the behaviour of deviation constructions have been carried out. Additionally the behaviour of the entire hollow-box-section is investigated. With calculations based on the finite-element-method an easy design procedure for deviation constructions is being derived. [source] | ||||||||||