Anpassungsfaktoren für das Lastmodell 1 des DIN‐Fachberichtes 101 für gewichtsbeschränkt beschilderte Straßenbrücken

Correction Factors for the Load Model 1 according to the DIN‐Fachbericht 101 for Weight constricted signposted Road Bridges Since 2003 the DIN‐Fachbericht 101 is the normative basis for the design loads of bridges in Germany. In contrast to the previous code of practice, the DIN 1072, the DIN‐Fachbericht does not include details about bridges, which will be signed with traffic weight limitations. This paper describes the development of reduction factors for the Load Model 1 in the DIN‐Fachbericht and presents the new calculated factors. Therefore the DIN‐Fachbericht Load Model 1 has been extended for the application of traffic weight limitations signed bridges.     

Beurteilung des Tragverhaltens von Spannbetonbrücken mit spannungsrisskorrosionsgefährdetem Spannstahl

Die Beurteilung des Tragverhaltens von Spannbetonbrücken, die in den 1960er und 1970er Jahren in Deutschland und Österreich gebaut wurden und für deren Herstellung vergütete Spannstähle Verwendung fanden, ist seit vielen Jahren Gegenstand der Forschung mit starkem Praxisbezug. Im vorliegenden Beitrag werden nach einer theoretischen Erläuterung des Tragverhaltens die praxisrelevanten Fragestellungen wie das Vorgehen bei der Beurteilung sowie weiterführende Untersuchungen erörtert. Zudem werden aktuelle Entwicklungen in der Forschung zur Beurteilung von gefährdeten Spannbetonbrücken aufgezeigt und diskutiert. Assessment of Load Bearing Behaviour of Post‐Tensioned Concrete Bridges Equipped with Prestressing Steel Susceptible to Stress Corrosion Cracking Basics, Practical Application and Current Developments Due to extending lifetime of infrastructure in general and posttensioned concrete bridges in particular the importance of durability aspects increases. Especially older prestressed bridges built in the 1960s and 1970s in Germany and Austria are subject of these investigations. Some of these post‐tensioned concrete bridges consist of quenched and tempered prestressing wires with high susceptibility to stress corrosion cracking as we know nowadays. This article deals with recalculation, assessment and evaluating methods for post‐tensioned concrete bridges including further analytic for endangered bridges. The procedure is shown by an example of an existing multi girder bridge and furthermore, future prospects are given.     

Lastkollektive für Eisenbahnbrücken aus Messdaten

Load spectra for railway bridges from measurement data – Part 1: systematic investigations into damage equivalent factor λ₁ on single span girders. The rapid progress in the evolution of memory device leads to an increasing data‐gathering. This offers new opportunities to define fatigue loads for railway bridges by systematic evaluations. So far, the definition of load spectra based on predefined trains and traffic mix was the only approach, but now it can be done much more detailed but even more CPU‐intensive by using influence data over a long period of time. This article shows practical results of this new approach for building load spectra by using systematic calculations on single span girders together with short theoretical explanations. The used influence data provided by the Österreichischen Bundesbahnen result in significant differences comparing to standardized values. Part 1 of this article includes exclusively the damage equivalent factor λ₁ while the second part includes the damage equivalent factors λ₂ and λ₃ as well as the threshold value λ_max and a model with respect to traffic trends.     

Beurteilung der Tragfähigkeit von geschädigten Stahlbetonbrücken auf der Grundlage der Ergebnisse einer Bauwerksprüfung

Structural Reliability Assessment of Damaged Reinforced Concrete Bridges on the Basis of the Results from a Bridge Inspection The regular bridge inspection is of high importance for the reliable use of the infrastructure. This paper describes and explains a method with supports the engineers of a bridge inspection in the assessment of the damaged bridges during or directly after the inspection. Based on this initial estimate the urgent measures i.e. a lower permitted bridge class can still be carried out before more detailed inspections and calculations have been done. The reliability analyses for the damaged bridges are carried out using first order and second order reliability method (FORM and SORM). The probability of failure, p_f or the safety index, of the system respectively are the main results of the calculation procedure. This paper shows the approach and the application with an example. Particularly in the communal sector the method can be helpful, because it can not be assumed that in all cases the regular bridge inspections and the appropriate maintenance have been carried out.     

Characteristic dynamic traffic load effects in bridges

When formulating an approach to assess bridge traffic loading with allowance for Vehicle-Bridge Interaction (VBI), a trade-off is necessary between the limited accuracy and computational demands of numerical models and the limited time periods for which experimental data is available. Numerical modelling can simulate sufficient numbers of loading scenarios to determine characteristic total load effects, including an allowance for VBI. However, simulating VBI for years of traffic is computationally expensive, often excessively so. Furthermore, there are a great many uncertainties associated with numerical models such as the road surface profile and the model parameter values (e.g., spring stiffnesses) for the heavy vehicle fleet. On site measurement of total load effect, including the influence of VBI, overcomes many of these uncertainties as measurements are the result of actual loading scenarios as they occur on the bridge. However, it is often impractical to monitor bridges for extended periods of time which raises questions about the accuracy of calculated characteristic load effects.Soft Load Testing, as opposed to Proof Load or Diagnostic Load Testing, is the direct measurement of load effects on bridges subject to random traffic. This paper considers the influence of measurement periods on the accuracy of soft load testing predictions of characteristic load effects, including VBI, for bridges with two lanes of opposing traffic. It concludes that, even for relatively short time periods, the estimates are reasonably accurate and tend to be conservative. Provided the data is representative, Soft Load Testing is shown to be a useful tool for calculating characteristic total load effect.     

正交异性钢桥面板纵肋与桥面板连接细节的疲劳评估及修复措施

正交异性钢桥面板由于具有自重轻、极限承载力大等优点目前广泛应用于大、中跨径桥梁中,我国已建和在建的大跨径桥梁也大多采用正交异性钢桥面板.但由于正交异性钢桥面板结构构造复杂,受焊接残余应力影响大,钢桥面板直接位于车轮荷载的作用下,一些构造细节处极易发生疲劳开裂.以国内某大桥正交异性钢桥面板为例,针对纵肋与桥面板之间的疲劳...     

Structure‐aware 3D reconstruction for cable‐stayed bridges: A learning‐based method

A powerful deep learning‐based three‐dimensional (3D) reconstruction method for reconstructing structure‐aware semantic 3D models of cable‐stayed bridges is proposed herein. Typically, conventional bridge semantic 3D model reconstruction methods are not robust when low‐quality point clouds are used. Furthermore, they are suited particularly for their respective fields and less generalized for cable‐stayed bridges. Hence, a structure‐aware learning‐based cable‐stayed bridge 3D reconstruction framework is proposed. The encoder part of the network uses both multiview images and a photogrammetric point cloud as input, whereas the decoder part uses a recursive binary tree network to model a high‐level structural relation graph and low‐level 3D geometric shapes. Two actual cable‐stayed bridges are employed as examples to evaluate the proposed method. Test results demonstrate that the proposed method successfully reconstructs the bridge model with structural components and their relations. Quantitative results indicate that the predicted models achieved an average F₁ score of 99.01%, a Chamfer distance of 0.0259, and a mesh‐to‐cloud distance of 1.78 m. The achieved result is similar to that obtained using the manual reconstruction approach in terms of component‐wise accuracy, and it is considerably better than that obtained using the manual approach in terms of spatial accuracy. In addition, the proposed recursive binary tree network is robust to noise and partial scans. The potential applications of the obtained 3D bridge models are discussed.     

宽箱梁荷载横向分布的探讨

变截面连续箱梁桥、连续刚架桥的设计,一般均将桥跨结构视作弹性梁元,采用平面杆系程序计算。荷载偏心用增大系数法考虑,增大系数的取值对于宽跨比很大的城市桥梁具有很大的任意性。本文以某实桥为背景,采用ANSYS结构分析通用程序计算了多个特征断面各腹板的横向分布系数。据此,对照了按荷载横向分布简化算法的计算结果,所得出的结论,可为同类工程设计提供参考。     

Versuche an genieteten Brückenlängsträgern – Statisches Verhalten,Ermüdungsfestigkeit und Rissausbreitung

Tests on riveted bridge stringers – behaviour under static loads, fatigue strength and crack propagation. The assessment of the load‐carrying capacity and of the remaining fatigue life of existing railway and road bridges has gained an increasingly significant role over the last years. Thus, the problem of determining adequate strength values of riveted members of older steel bridges once again arose during the elaboration of the ONR 24008 specification. In the course of a research project initiated by the Austrian Federal Railways (ÖBB), static and fatigue tests were carried out on riveted members taken from a demolished railway bridge in Salzburg. The results of these tests gave further insight into the load carrying behaviour of built‐up riveted members, particulaly the progagation of fatigue cracks.     

Die Brücke über den Oberhafen in Hamburg

The bridge across the Oberhafenkanal in Hamburg. The replacement of 4 steel railway bridges with a total steel construction weight of 4000 tons in the centre of Hamburg, which connect the central station of Hamburg with the south of Germany was a great challenge in bridge building. The central steel superstructure of the bridge, the Oberhafenbrücke, a five‐span truss continuous beam is special because it is a combined railway and road bridge. The railway travels on the upper deck between the upper chords whereas the road traffic travels on the lower deck between the truss. This superstructure crosses the Oberhafenkanal. The available time for the complete building process comprised of statics, design, manufacturing and assembly was only 14months. The end of this process was totally fixed because of the long‐time announced complete shutdown of the railway connections to the south and parts of the Hamburg central station between December 24^th and December 31^st, 2007. Despite the new definition of substantial design‐parameters (load models for road and railway, permanent bearing‐system, temporary bearing‐system after December 31^st, 2007) and therefore a reduction of the available time by 4 months the task of building the new bridge was carried out successfully by the consortium comprised of Eiffel Deutschland Stahltechnologie GmbH, Bilfinger Berger AG ZN Hamburg and Jürgen Martens GmbH & Co. KG.     

3D‐Tragwerkssimulationen zur Erfassung der aerodynamischen Beanspruchungen bei der Planung von Brückenstrukturen

On the Modeling of Aerodynamic Effects in the Design Phase of Bridges via 3D Structural Simulations. The use of innovative building materials has led to a trend towards increasingly light and slender structures. Especially for cable‐stayed and suspension bridges, but also for girder bridges, there has been observed a growing dynamic vulnerability. The vibrations are caused, besides pedestrian and traffic‐induced vibrations, mainly by wind action. Apart from local vibrations of cables, the global dynamic behaviour of the bridge deck is of special interest. This paper gives an overview of the analysis methods currently used in practice. Load models which are based on a two‐dimensional treatment of the flow around the cross‐sections and their numerical treatment within the framework of a 3D structural simulation are presented. The experimental measurement of stationary and instationary cross section parameters is briefly recapitulated. Application in engineering practice in both preliminary and final design phases is demonstrated by four examples.     

A filtering-based bridge weigh-in-motion system on a continuous multi-girder bridge considering the influence lines of different lanes

A real-time vehicle monitoring is crucial for effective bridge maintenance and traffic management because overloaded vehicles can cause damage to bridges, and in some extreme cases, it will directly lead to a bridge failure. Bridge weigh-in-motion (BWIM) system as a high performance and cost-effective technology has been extensively used to monitor vehicle speed and weight on highways. However, the dynamic effect and data noise may have an adverse impact on the bridge responses during and immediately following the vehicles pass the bridge. The fast Fourier transform (FFT) method, which can significantly purify the collected structural responses (dynamic strains) received from sensors or transducers, was used in axle counting, detection, and axle weighing technology in this study. To further improve the accuracy of the BWIM system, the field-calibrated influence lines (ILs) of a continuous multi-girder bridge were regarded as a reference to identify the vehicle weight based on the modified Moses algorithm and the least squares method. In situ experimental results indicated that the signals treated with FFT filter were far better than the original ones, the efficiency and the accuracy of axle detection were significantly improved by introducing the FFT method to the BWIM system. Moreover, the lateral load distribution effect on bridges should be considered by using the calculated average ILs of the specific lane individually for vehicle weight calculation of this lane.     

Talbrücke Elben – Eine Stahlverbundbrücke mit einteiligem Querschnitt

Viaduct Elben – A steel‐composite bridge with one‐piece cross‐section. In the north of Siegen a non existing section of the German motorway Autobahn A 4 and of the federal highway B 54n, also called “Hüttentalstraße”, was completed during the last years. The 432 m long viaduct – called “Talbrücke Elben”, as an important element in the construction for the extension of the A 4, is in particular interesting because of its design and its construction itself. During the last years about 10 similar constructions have been implemented, others are currently planned. Therefore, it seems appropriate to report about the experiences with steel‐composite bridges in general and particular, always having the bridge “Talbrücke Elben” in mind. Furthermore, the paper intends to give an overview on further fields of application in the near future.     

Ingenieurbaukunst in den neuen Bundesländern am Beispiel des Brückenbaus

The art of structural engineering in the new federal states of Germany – based on examples of bridge construction. During the last 15 years, a large number of interesting and innovative bridge structures were constructed in the new federal states. Based on a few examples it will be shown that, many bridges were erected by a new generation of bridge builders within the framework of the urgently needed expansion of the road network. These bridges represent new structural concepts and ideas by making use of new materials and enabling for new dimensions that far outperform previous limitations.     

Bewertung bestehender Natursteinbogenbrücken

Assessment of existing natural stone arch bridges. Arch bridges made of natural stone masonry rank among the oldest structures still in full function within road and railways. With a age from partly far over 100 years these represent historically very valuable built volumes in large number of several thousand buildings at the same time. The oldest existing bridges based on empirical values design, later there were graphic procedures for structural design, one developed approximation formulas on basis of the arch line of thrust for the draft of substantial geometry parameters such as span, type of arch as well as arch thickness at the crown and springing. In the course of the revision of these buildings evaluations regarding load‐carrying capacity and serviceability on the basis are demanded under today valid loads and standards. In this paper apart from a short overview to the existing arch bridges the possibilities of the structural modelling are discussed. An emphasis forms the computation of the masonry load‐carrying capacity, which is described in particular by safety considerations. The procedures referred to the bridge construction are transferable in principle to other structures of building construction.     

Verdrängungskörper in vorgespannten Brücken: Untersuchung und Instandsetzung

Hollow Fillers in Prestressed Bridges Examination and Reinstatement. To reduce self weight hollow fillers were frequently used in prestressed bridge decks between 1960 and 1970. Investigations of these bridges indicate that often the hollow fillers have been the starting point of damages. Sometimes first defects already arose while casting, if e.g. too stiff concrete has not been able to enclose the hollow fillers. Due to a defective bridge deck sealing and cracks within the bridge deck, water is able to penetrate the hollow fillers. Often also leaking drainage systems running through a hollow filler or located nearby have caused damages on the bridge deck.     

50 Jahre Aluminiumbrücke über den Datteln‐Hamm‐Kanal

50th birthday of the aluminium road bridge across the Datteln‐Hamm‐Kanal in Germany. Germany's first aluminium road bridge, the Schwansbell Bridge spanning the Datteln–Hamm Canal near Lünen, was opened to traffic in 1956. The design is a trussed structure made from extruded profiles and sheets using AlMgSi 1 alloy (today's equivalent would be EN AW‐6082). The bridge has a span of 44.2 metres; it has a dead weight of 25 t and vehicles weighing up to 12 t are allowed to use it. The design of a comparable steel bridge had a dead weight of 60 t. Thus, the use of aluminium led to a weight saving of 58%. Aluminium rivets, also made from AlMgSi1, were used almost exclusively for the joints. The shape of the rivets had previously been tested and optimised in a series of tests. A decision was made before the bridge was built to forego the use of any additional coating in order to evaluate the corrosion resistance of the aluminium. To this day, there has not been any need for either additional corrosion protection to be applied to the aluminium structure of the bridge or for any maintenance work to be carried out on the bridge because of corrosion. Routine inspections of the bridge confirm that it is in an excellent condition. This is all the more remarkable as the construction is located in the Ruhr area and has been exposed to an industrial atmosphere for 50 years. Savings in the cost of corrosion protection as well as for the work needed to maintain such protection have been made during the bridge's entire service life.     

Characteristic traffic load effects from a mixture of loading events on short to medium span bridges

In recent years, highway bridge load assessment has been recognised as an area through which savings can be made by avoiding unnecessary bridge refurbishment and replacement. Load effects in bridges result from single truck crossings or multiple-truck presence events which are, statistically, not identically distributed. Conventional approaches fit statistical distributions to mixtures of non-identically distributed load effects. Inaccuracies in the conventional approach are identified and an alternative approach is developed to find the characteristic load effects. Theoretical and field data are used to show the potential implications of conventional techniques and to demonstrate the application of the new approach.     

Reliability-based optimisation design of post-tensioned concrete box girder bridges considering pitting corrosion attack

Since the mid-twentieth century, prestressed concrete (PC) bridges have been significantly developed to become the most important type of bridge in the world. However, only a few studies have dealt with the reliability-based design optimisation (RBDO) of PC bridges despite the fact that RBDO demonstrates the real behaviour of structures. Moreover, the corrosion of post-tensioned tendon in PC bridges seriously caused sudden failures which have been recorded in the world. Since then, this study presents the probabilistic model and approach to formulate and analyse the RBDO of PC box girder bridges which consider the pitting corrosion phenomenon of shear, torsion reinforcements and post-tensioned tendon. A practical example of a typical PC box girder bridge is presented and discussed. Sensitive analyses are performed to evaluate the influence of ultimate target reliability index on the optimal solution. For the simple support PC box girder bridge, the ultimate target reliability index should be in the range of β_ult: 3.5–5 in order to produce the optimal design.