Bridge girders are subjected to repeated patch loading during incremental launching (i.e. travelling over supports). Plastic deformations are likely to occur in the girder already at the first patch ...loading. They influence the girder’s structural response and bring about a decrease in the ultimate resistance at subsequent patch loadings. This problem is analysed in the present paper through the serviceability limit state (SLS) of incrementally launched bridge I-girders (ILBGs). The SLS of ILBGs is a current problem since only a few studies, with contrasting conclusions and certain limitations, have been recognised in the literature. Research is limited on plate girders without longitudinal stiffeners made of structural steel. Flat slide-type launching shoes are considered in this paper.
The serviceability requirement (repeatable behaviour of ILBGs) and criterion (that effective membrane strains should remain in the elastic range) are adopted from the literature. So, the serviceability resistance is adopted as a load at the start of the effective membrane plastic strains in the girder. In order to propose a practical and simple SLS design procedure, the serviceability resistance is normalised against the ultimate resistance, so a serviceability correction factor (ksls) is defined. The paper presents a parametric numerical analysis of the factor (ksls). A finite element model previously developed and validated by the author is employed to simulate a nonlinear response of patch-loaded girders. The parametric study includes 599 girders. ksls is inversely proportional to the web thickness and directly proportional to the flange thickness and the yield strength of the steel material. The load length, web depth and flange width do not influence ksls. The influence of the spacing between transverse stiffeners on ksls is negligible. Finally, by regression analysis of the results of parametric study, an original and reliable serviceability correction factor is proposed as the main objective of the research. The range when the SLS of ILBGs should be checked is also defined.
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•The serviceability correction factor (ksls) is the serviceability resistance normalised against the ultimate resistance.•A parametric numerical analysis of ksls is conducted. The numerical database contains 599 patch-loaded girders.•The load length, web depth and flange width do not influence ksls, while the influence of the spacing between transverse stiffeners is negligible.•ksls is inversely proportional to the web thickness and directly proportional to the flange thickness and steel grade.•A reliable, original and simple empirical expression for ksls is proposed.
During launching, the superstructure acts as a continuous beam supported by different launching bearings on the piers. Just before reaching the next pier, a part of the superstructure temporarily ...behaves as a long cantilever. As a result, a large bending moment and reaction force at the last bearing occur. The interaction of the internal forces results in a biaxial stress state in the cross‐section. This load case is usually determining for the buckling check and the structural design of the webs. Additionally, the webs of the superstructure and the launching bearing often fail to share the same center lines. This eccentricity can be caused by misalignments of the launching bearings, the necessary air gap to the lateral guide as well as the different thicknesses of the panels along the superstructure. These eccentricities are not considered in the buckling check according to EN 1993‐1‐5 1. It is often discussed how these eccentricities affect the buckling behaviour and whether they must be considered in the buckling check. In the case of launching bearings like a rocker system which includes an elastomeric bearing between the superstructure and the launching beam, the reaction forces of the nonlinear material behaviour are additionally discussed. In 2 the effects on the buckling resistance in dependence of load eccentricity for some parameters for the different types of launching bearings are presented. 3 shows the comparison of the buckling resistance with investigations from 4 and 5 with the buckling check according to 1. A comprehensive summary and the new proposal for considering an eccentric load application and clamping effects in the buckling zone can be read in 6. This paper shows first investigations of the influence of the elastomeric bearing and the problem of the reaction of the nonlinear material behaviour and its definition in the numerical model. The results have shown that load eccentricities in combination with elastomeric bearings have no impact on the buckling behaviour.
In the incremental launching method employed for steel bridge construction, the girder is subjected to patch loading which occurs at the piers’ position. This loading significantly affects the girder ...resistance in the construction stage. Therefore, prediction of the girder resistance under this loading is important. This paper proposes a new approach for predicting the patch load resistance of stiffened plate girders using an extreme gradient boosting algorithm (XGBoost). A total of 170 experimental data on stiffened plate girders under patch loading collected from the literature serves as the training and testing data to build the predictive model. To demonstrate the efficiency of the proposed model, its predictions were compared with those obtained from other Machine Learning (ML) methods such as support vector machines (SVM), decision tree (DT), random forest (RF), adaptive boost (Adaboost), and deep learning (DL). The accuracy of the proposed model was validated against the existing equations taken from the design standards (EN-1993-1-5 and BS 5400) as well as existing formulae in the literature. The comparative results reveal that the proposed model provides better and more accurate predictions than the existing formulae.
•A new approach for predicting the patch load resistance of stiffened plate girders using an XGBoost algorithm is proposed.•The efficiency of the proposed method is demonstrated by comparing its performance with that obtained from other ML methods.•The accuracy of the developed method is verified with the design equations from modern codes as well as existing formulae.
The effectiveness of the incremental launching method with lightweight, flexible nose beam in the construction and erection of emergency bridges with large-span composite materials is investigated ...through a combined experimental and numerical study. A theoretical model is developed to characterize the additional bending movement induced during the flexible nose launching process and analyze stress fluctuations in structural components during critical launching stages, providing theoretical underpinning the for lightweight nose beam design. Results indicate that the stress attributable to the additional bending moment during critical launching stages constitutes approximately 9.6 %, significantly impacting lightweight nose beam design con-siderations. Additionally, it was shown that conventional static analyses are difficult to adequately capture the internal force changes during the launch of a flexible nose beam. Therefore, a finite element model accounting for geometric and contact non-linearity is proposed, exhibiting higher precision in predicting additional bending movement values compared to traditional finite element models. The accuracy of the finite element model is confirmed through scaled-down experiments.
Abstract
Incremental launching erection is a widely construction technology, which has the advantages of low cost, low environmental requirements, simple equipment. In this project, the multi-point ...support rolling device is used instead of the linear or planar slide support system, and the short nose bridge-fishing method is further used to realize the smooth pier of the beam body. According to the site, a simple and easy deviation correction device is designed. According to the simulation results of deflection calculation and field deflection measurement data, the construction monitoring of the process of incremental launching was carried out, and the incremental launching construction was successfully completed.
Abstract
Für den Ersatzneubau der Überführung der Bundesautobahn A73 über die ICE‐Ausbaustrecke Nürnberg–Ebensfeld und die Bundesstraße 4 wurde ein innovativer Lösungsansatz mit unterschiedlich ...geformten Tragebenen gewählt. Die beiden äußeren Träger werden dabei als Doppelwelle ausgeführt – die mittleren Tragebenen als Monowelle optisch zu einer Einheit verbunden. Das Bauwerk bildet ein Merkzeichen und hält sich dennoch in der Erscheinung zurück. In Kombination mit den gläsernen Schutzwänden auf den äußeren Trägern ergibt sich ein elegantes Wellenspiel, welches ein Alleinstellungsmerkmal darstellt und sich wie selbstverständlich in die Landschaft einfügt.
Abstract
The Güßbach Wave – an innovative steel composite bridge with asymmetric trough cross‐section in wave design
For the replacement of the overfly over the highway A73, the high‐speed railway road Nuremberg–Ebensfeld and the federal road B4 an innovative design concept with different shaped girders was chosen. The outer girders are designed as a double wave – the inner girders as a mono wave merge into one unity. The bridge creates both, an outstanding sign and also a distant figure. In combination with the transparent protection walls, an elegant wave game is created which establish a unique selling point and fits obviously into the landscape.
Für den Ersatzneubau der Überführung der Bundesautobahn A73 über die ICE‐Ausbaustrecke Nürnberg–Ebensfeld und die Bundesstraße 4 wurde ein innovativer Lösungsansatz mit unterschiedlich geformten ...Tragebenen gewählt. Die beiden äußeren Träger werden dabei als Doppelwelle ausgeführt – die mittleren Tragebenen als Monowelle optisch zu einer Einheit verbunden. Das Bauwerk bildet ein Merkzeichen und hält sich dennoch in der Erscheinung zurück. In Kombination mit den gläsernen Schutzwänden auf den äußeren Trägern ergibt sich ein elegantes Wellenspiel, welches ein Alleinstellungsmerkmal darstellt und sich wie selbstverständlich in die Landschaft einfügt.
The Güßbach Wave – an innovative steel composite bridge with asymmetric trough cross‐section in wave design
For the replacement of the overfly over the highway A73, the high‐speed railway road Nuremberg–Ebensfeld and the federal road B4 an innovative design concept with different shaped girders was chosen. The outer girders are designed as a double wave – the inner girders as a mono wave merge into one unity. The bridge creates both, an outstanding sign and also a distant figure. In combination with the transparent protection walls, an elegant wave game is created which establish a unique selling point and fits obviously into the landscape.
Teil 1 des vorliegenden Aufsatzes umfasst die Erläuterung der großmaßstäblichen Beulversuche unter biaxialer Belastung, die an der Technischen Universität München im Zuge von Projekten durchgeführt ...wurden, sowie deren Nachrechnung und Modellierung mit der Finite‐Elemente‐Methode. Das in Teil 1 beschriebene numerische Modell wurde für die nachfolgende Parameterstudie erweitert und geringfügig angepasst. Der Flansch wird in der Modellierung berücksichtigt, damit seine Einspannwirkung erhalten bleibt. Ohne Anschluss eines Bodenblechs oder Flanschs kann eine exzentrische Last nicht in das Stegblech eingeleitet werden, sodass eine gewisse Einspannwirkung unerlässlich ist und somit die Annahme einer Navierschen Lagerung des Rands der exzentrischen Lasteinleitung nicht zutrifft. Die Ergebnisse der numerischen Parameterstudie mit dem entwickelten Modell werden in diesem Teil 2 zunächst kurz zusammengefasst. Anschließend werden die aufnehmbaren Spannungen nach der Methode der reduzierten Spannungen gemäß DIN EN 1993‐1‐5:2019 mit denen der numerischen Berechnung verglichen und bewertet. Dieser Vergleich zeigt, dass bereits durch die Berücksichtigung eines Flanschs bei I‐Querschnitten ein enormes wirtschaftliches Potenzial für den Beulnachweis erschlossen werden kann. Daher wird ein Ansatz entwickelt und vorgestellt, der die Berücksichtigung einer exzentrischen Lasteinleitung im Beulnachweis ermöglicht und gleichzeitig die auftretenden Einspanneffekte konservativ berücksichtigt.
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