Crane Runway Research Articles

Life extension of pre-damaged existing crane runway girders

Crane runway girders are subjected to cyclic loading and must therefore be designed against fatigue failure. For existing structures, however, there are no standards for handling pre-damaged components at the end of their calculated lifetime. The Institute for Material and Building Research of the University of Applied Sciences Munich examines different approaches on how to deal with existing welded steel structures. The research project addresses the following questions:How can pre-damaged components without visible cracks be strengthened?How can components with visible cracks be repaired in a fatigue-proof manner?How can pre-damaged components be reinforced through a low-notch application of steel cover plates?In order to answer these questions several numerical and experimental investigations are carried out. Different innovative fastening techniques like lockbolts, adhesives and self-tapping screws for attaching reinforcement cover plates are tested on small and large specimens. Within this paper the research project will be presented and previous results on components without visible cracks will be summarized.

Оцінка залишкового ресурсу металевої підкранової балки на стадії зростання втомної тріщини

Оцінка залишкового ресурсу металевої підкранової балки на стадії зростання втомної тріщини

Influence of Imperfections in the Design of Crane Runway I‐Beams

AbstractCrane runway beams are generally loaded by vertical and horizontal forces as well as not‐negligible torsional actions. Horizontal and torsional deformations originate already from the 1st order analysis. The effects of imperfections of crane runway beams could, at least partially, be simulated by these deformations. While for the purely vertically loaded beams it is necessary to consider the horizontal bow imperfection, for the generally loaded beams with horizontal forces as well, the influence of horizontal bow imperfection may not be as important, due to the occurrence of horizontal deflection from primary actions. Eurocode EN 1993‐6 allows to consider either eccentricities of vertical forces or introduction of horizontal bow imperfections in the design of crane runway beams. In this article, using a self‐developed FEM‐program, the effect of horizontal bow imperfection for the generally loaded crane runway beams is investigated. The two options of EN 1993‐6 are compared in the FEM analyses with the simplified design methods like the Annex A method of the same standard and the Naumes method.

Influence of the geometry of butt welds and longitudinal attachments on their fatigue resistance

AbstractMany constructions, such as wind turbines, bridges and crane runways, are cyclic loaded so that fatigue failure may occur. Therefore, in the course of the revision of Eurocode 3, two research projects funded by AiF‐DASt re‐investigate the classification of constructional details of EN 1993‐1‐9. This paper focuses on the geometrical influence on the fatigue resistance of butt welds and longitudinal attachments. First, the influence of the plate thickness on butt welds was investigated. Both a meta‐study based on test results of various research projects and our own test series on butt welds up to 80 mm thickness led to interesting conclusions.Furthermore, the influence of the length and radius of longitudinal attachments on the fatigue resistance was investigated. By experiments and numerical analysis, clarification has been sought whether the transition radius larger than 150 mm or the ground weld toe is decisive for the improvement of the fatigue resistance. Since previous meta‐studies could not provide a clear result on the influence of the longitudinal attachment length, this was also investigated.A database established in the projects allows to integrate and assess the specified details of butt welds and longitudinal attachments in the context of the overall approach in EN 1993‐1‐9.

Stress increases in crane runway girders due to rail joints

AbstractVertically acting wheel loads from overhead bridge cranes and potential additional horizontal crane loads induce two types of stresses in crane runway girders: i) global stresses due to bi‐axial bending and torsion and ii) local stresses which mainly affect the girder's web. The latter typically represent one of the most decisive criteria for the fatigue design check of welded girders and are the focus of this paper. Crane rails with foot flange are typically connected to the top flange with rail clips. These clips maintain the position of the rail in vertical and horizontal transverse direction, but they generally allow for longitudinal movement of the rail. Rails with foot flange are used with and without elastomeric bearing pads between the rail and the top flange of the girder. The local stresses in the webs of crane runway girders are strongly affected by discontinuities of the crane rails. Such discontinuities can originate from unplanned rail cracks as well as planned rail expansion joints. The current mechanical models for concentric as well as eccentric wheel loading in relevant design standards assume continuous crane rails. However, rail joints are expected to significantly increase the local stresses in the region beneath rail joints. The present paper focuses on the impact of rail joints on the local stresses in crane runway girders. The research activities comprise experimental tests as well as finite element calculations. The aim of the investigations is to develop a better understanding of the mechanical behaviour in order to avoid future fatigue damage due to an unexpected increase of local stresses at a rail joint.

Insights into the occurrence of transverse bending stresses in web plates of crane runway girders

AbstractCrane runway girders are installed in industrial buildings to carry heavy loads from crane operation. The wheels of the bridge crane introduce concentrated forces in the crane runway girder via the rails. This leads to local vertical stresses in the web plates of the crane runway girders in addition to the global bending stresses. The local stresses at the top of the web usually become crucial for the fatigue design of the girder. The potential eccentricity of vertical wheel loads as well as additional horizontal forces from operation of the crane can lead to torsional rotations of the rail and the top flange and subsequently to transverse bending of the web plate of the crane runway girder. In the current design model of EN 1993‐6, the rotation at the top of the web plate is described by assuming the rail and the top flange of the girder acting as a bar under torsion, supported continuously by the bending stiffness of the web. Within this paper the existing model for the rotations is improved and it is shown that these modifications lead to more accuracy in comparison with numerical finite element calculations. It is also shown that the current simplified procedure for calculating the resulting stresses in the web is not able to adequately describe the real stresses for all practical cases. It is found that the quality of the stress predictions can significantly be improved by considering the web as a simply supported plate with the previously identified rotations on its top edge.

Fatigue behavior at flange thickness transitions with cope holes – design model for engineering practice

AbstractFlange thickness transitions are common constructional details in welded girders, such as crane runway girders or main girders of highway and railway bridges, to adapt the bending moment capacity of the girder to variable bending moment distributions. At these details the transverse butt weld is often decisive for the fatigue verification of the member. Based on comprehensive studies at Graz University of Technology, including also two fatigue tests, stress concentration factors for the fatigue verification of the butt welds at the girder flange were developed. However, due to the complex local stress fields at the flange thickness transition, cope holes were not included in these studies.Within a research cooperation of Graz University of Technology and Ruhr University Bochum, flange thickness transitions with cope holes are studied recently. Based on comprehensive numerical FE‐ calculations within the practically relevant geometric parameter range, the complex local stress fields near the cope hole are analyzed both, within the web and the flange plate. For validation of the FE‐model also strain measurements were carried out at large‐scale test girders. Applying the hot spot stress method, the decisive hot spots are determined, and a simplified design model is developed for an accurate prediction of these hot spot stresses.The paper presents this design model in detail and shows its accuracy ‐ compared to the FE‐results ‐ for a wide range of different geometrical conditions, as used in practice (e.g. variation of girder dimensions, flange thickness ratio, tapering to the outside and to the inside).Finally, also the results of full‐scale fatigue tests on two different welded girders with flange thickness transitions and cope holes are presented. This provides an accurate fatigue resistance for the proposed design model, based on the hot spot stress method.

К вопросу о допустимости дефектов в нижнем поясе подкрановых балок

Crane beams are among the most damaged structures in the buildings with heavy, and very heavy-duty overhead cranes. Their destruction can lead to the death of people working in the workshop, and to significant material losses. The durability of crane structures is determined by the intensity of work of the overhead cranes. The main defects and damages of metal crane beams are regulated by the standard STO-22-05—04, according to which all the cracks in the crane beams are divided into groups according to the risk of destruction. It is believed that the presence of cracks in the lower (stretched) chord of crane beams is unacceptable. Modern methods of non-destructive testing allow to detect defects with a minimum size from 2 mm (ultrasound) to 1 µm (capillary method). These cracks may be due to the inhomogeneity of the chemical composition of the alloy, or be of a structural nature, manifesting itself, in contrast to fatigue cracks that grow in the most loaded areas of the structure, in any part of the lower chord of the beam. If any crack is found in the lower chord of the crane beams, it is required to stop the operation of the crane and carry out a major overhaul of the crane runways. However, following these formal rules is not always economically and logically justified. The paper considers an example of rationing by the criterion of non-straining through cracks in the lower stretched chord (cracks of the first group). Based on the criteria of linear fracture mechanics, coefficients are proposed for all steels from which the crane beams are made, allowing for their technical inspection to give an express assessment of the admissibility of the detected through cracks. It is also shown that it is necessary to normalize the permissibility of the parameters of semi-elliptical cracks in the stretched zone (in the lower shelf of the I-beam crane beam), since these cracks can eventually develop into through defects.

Impact of rail joints on the local stresses in crane runway girders

Vertically acting wheel loads from overhead bridge cranes and potential additional horizontal crane loads induce global stresses due to bi-axial bending and torsion and local stresses in crane runway girders which mainly affect the girder’s web. The latter typically represent one of the most decisive criteria for the fatigue design check of welded girders and are the focus of this paper. Crane rails with foot flange are typically used for moderate to high wheel loads. They are usually connected to the top flange with rail clips. Rails with foot flange are used with and without elastomeric bearing pads between the rail and the top flange of the girder. The local stresses in the webs of crane runway girders are strongly affected by discontinuities of the crane rails. Such discontinuities can originate from unplanned rail cracks as well as planned rail expansion joints. The current mechanical models for concentric as well as eccentric wheel loading in relevant design standards assume continuous crane rails. However, rail joints are expected to significantly increase the local stresses in the region beneath rail joints. The present paper focuses on the impact of rail joints on the local stresses in crane runway girders. The research activities comprise experimental tests as well as numerical parametric studies based on finite element calculations, both for rails with and without elastomeric bearing pads. The aim of the investigations is to develop a better understanding of the mechanical behaviour and to quantify the increase factor for maximum local stresses in order to avoid future fatigue damage due to an unexpected increase of local stresses at a rail joint.

Local vertical compressive stress in the crane runway beam web

In this paper, the authors analysed several variants of connections between a block rail (60 mm × 60 mm) and a crane runway beam (IKS 800-6). They compared local vertical compressive stress in the crane runway beam web, calculated using an analytical approach and numerical simulations. In the case of the continuous block rail rigidly fixed to the beam flange, satisfactory convergence was obtained. For the remaining types of connections the results based on the analytical method were different from the results of the numerical simulations. The difference resulted from the fact that the analytical method did not take into account the crane rail joint. Furthermore, the impact of the elastomeric bearing pad on the local stress value was taken into account in a simplified manner in the analytical method by increasing the effective length by approximately 30%. The local vertical compressive stress in the crane runway beam web was significantly affected by the connection between the rail and the crane runway beam, the crane rail joint type, the use of the elastomeric bearing pad, the length of the elastomeric bearing pad, and the crane rail wear.

Influence of Longitudinal Stiffeners on the Local Stresses in Crane Runway Girders ‐ Experimental and Numerical Investigations

AbstractCrane runway girders with slender webs are often strengthened by additional longitudinal stiffeners to avoid local plate buckling of the web. It is expected that this leads to an increase of local vertical bending stresses near the top edge of the web due to eccentric wheel loads. These local stresses have a significant impact on the fatigue design of the flange‐to‐web connections and the required girder dimensions. However, the current design model in EN 1993‐6 for crane supporting structures does not consider this effect. In order to study this behaviour in detail, laboratory tests and numerical finite element calculations are carried out on crane runway girders with longitudinal stiffeners at different positions of the web. It is verified that the local stresses increase with decreasing distance of the stiffeners from the top edge of the web plate. Based on these results and a modified proposal from literature, the design model in EN 1993‐6 is extended to also cover additional stiffeners. Finally, the model is validated through a comparison with tests and numerical calculations.

Re‐evaluation and extension of fatigue test data for welded attachments and butt joints

AbstractWelded structures under fatigue loading are widely used in civil engineering. The fatigue strength of components such as welded attachments and butt joints are often determining for the dimensioning of bridges, crane runways or tower constructions. The existing design rules of Eurocode 3, Part 1‐9 are mainly based on experimental data. However, the experimental background of Eurocode 3 Part 1‐9 is partly incomplete. Some fatigue detail classifications are based on numerical modelling and engineering judgement. New findings from experimental research allow a revision of these details, leading to higher fatigue strength classifications in many cases.Firstly an overview of an extensive database for fatigue tests on butt joints and welded attachments is addressed. A method for statistical analysis is presented, which allows the consideration of fatigue tests from different sources by using the design philosophy of Eurocode 3 Part 1‐9 and also meeting the requirements of Eurocode 0.The paper is also going to present some new supplementary experimental investigations on a fatigue detail for transverse end welds of cover plates with blended weld toes, which is traditionally used in German bridge design.Finally a revised and simplified fatigue detail catalogue for welded attachments and butt joints is addressed which is intended as a suggestion for the next generation of Eurocode 3 Part 1‐9.

Strain measurements on rails of crane runway girders to predict accurate wheel loads

AbstractIn existing crane runways, data on the actual wheel loads acting on the crane rail are often missing. Therefore, approximated wheel loads have often to be assumed for static calculations of the crane runway girder. Within this paper, a method is presented that allows to calculate the actual wheel loads based on strain measurements on the crane rail. The idea is to measure strains on the rail at certain pre‐defined locations, while the crane is passing and calculate the wheel load from the measured strains. The correlation between the strains in the rail and the wheel load is determined in a numerical finite element study and in laboratory tests.The numerical studies also comprise several different geometries of crane runway girders. The objective is to verify the influences of them on the calculated strains in the rail. The results of the numeric calculations show, that the strains in the rail generally depend on the stiffness of the crane runway girder. The thickness of the upper flange and the web as well were identified as the main parameters. This behavior is also verified in laboratory tests.For the contact between the rail and the crane runway girder, two different cases have been investigated. The first analysis refers to a hard contact under compression which allows separation under tension. This configuration corresponds to cases with steel wearing plates beneath the crane rails. The second case considers an elastomeric rail pad between the rail and the crane runway girder.

A proposal for the local stresses in retrofitted crane runway girders due to eccentric wheel loading

AbstractGenerally, the local stresses near the web‐flange connection represent one of the most decisive criteria for the fatigue design of steel crane runway girders, particularly because every crane wheel induces an individual stress cycle and fatigue failure can potentially occur at any position of the girder's length. This paper presents a crane runway girder made of steel that has been retrofitted in the past to reduce the local bending stresses in the web, because of the installation of a new, heavier crane. This was done by additional longitudinal stiffeners to form a boxed upper flange. The local vertical stresses in the girder's web are investigated numerically and experimentally and the influence of the subsequently attached reinforcement plates, forming a boxed upper flange, is studied. Traditionally, it is state of the art to neglect any local bending stresses in the web after retrofitting the upper flange area to get a local box section. The results presented in this paper indicate that the additional local bending stresses within the upper flange box section can be significant and should not be neglected for fatigue design. Therefore, a new design concept for the calculation of the local bending stresses in webs of retrofitted crane runway girders with new boxed upper flange is proposed.

Limit states design of crane runway girders

Steel crane runway girders are subjected to torsion by their eccentric loads. The twist rotation of the principal axes caused by torsion induces additional bending moments, and reduces the resistance to lateral-torsional buckling. There is little guidance on how to design for torsion, and design procedures are often intuitive, with varying degrees of rationality and precision.This paper seeks to establish a logical procedure for designing crane runway girders which is based on an extension of the limit states methods of designing for biaxial bending. An additional term for the ratio of the design torque to the section torsion resistance is included in the interaction equations. Proposals are made for determining this section resistance. Research has shown that this addition can allow for the reduction in the lateral-torsional buckling resistance caused by the twist rotations. A linear elastic analysis of the twist rotations is used to determine the moment increases caused by torsion.An example of the proposed method is developed and illustrated by a design example. The design is governed by the member capacity, which is mostly affected by the lateral-torsional buckling capacity. Torsion has a very small effect, and the twist rotations are small. The twist rotations cause a significant increase in the minor axis bending moment, but this has only a minor effect on the member capacity.

Modeling the stress-strain state of crane metal structures

The intensification of construction production imposes very strict requirements on the safety of construction machines. When carrying out lifting and hoisting operations using overhead cranes, production safety is primarily determined by the technical condition of the undercarriage and crane runways, as well as metal constructions. The authors deal with the issues related to modeling and research of the stress-strain state of metal structures of an overhead crane. A model of the crane metal structure is proposed, which includes the main and end box-section crane girders. To study possible geometric movements of the crane, a model of an overhead crane was designed in KOMPAS-3D software environment. The model contains main and end box-section girders. The model allows determining the maximum possible misalignment of the crane and runout of one of the sides. To determine the bending, tensile and compressive stresses in the bridge truss and the deformations of the crane metal structures, depending on the working loads, a 3D model of the bridge crane was created in the ADW Winmachine software environment. With its help, the bending stiffness of the crane bridge was established. These values are necessary to compile a mathematical model of an overhead crane as a control object in the synthesis of an automatic control system.

Horizontal Forces on the Crane Runway during the Motion of the Crane

During the motion of an overhead travelling crane on the crane runway, horizontal forces between the crane and the crane runway girder occur. Some possibilities were presented in a paper by the author in 2018 and 2019. In the last one, a dynamic model was presented. This dynamic model enables us to determine the behaviour of the crane during its motion and also to calculate the horizontal transverse forces between the overhead double bridge crane wheels and the crane runway girder. This dynamic model consists of rigid parts connected by springs representing the elasticity of the steel structure of the overhead double bridge crane. The dynamic model can be used not only for the calculation of horizontal forces but also for the determination of the crane motion in general. The motion of the crane can be investigated both during its accelerating and during its motion with constant velocity. The basic assumption of this model is that there is no contact between the rim of the crane wheel and the rail of the crane runway. This paper shows the simulation of the motion of a specific overhead double bridge crane which is stationary and starts to move due to the engine’s torque. The data of the crane are shown in the paper as well as the result of the simulation. The initial conditions of the crane for the purpose of the simulation are described in the paper. The simulation assumes no contact between the rim of the crane wheel and the rail of the crane runway which is consistent with the model’s assumptions.

Effects of Shear Lag in Steel Box Girders of a Crane Runway

Abstract The term of shear lag is related to the discrepancies between the approximate theory of the bending of beams and their real behaviour. It refers to the increases of the bending stresses near the flange-to-web junctions and the corresponding decreases in the flange stresses away from these junctions. In the case of wide flanges of plated structures, shear lag caused by shear strains, which are neglected in the conventional theory, may be taken into account by a reduced flange width concentrated along the webs of the steel girders. In EN 1993-1-5, the concept of taking shear lag into account is based on effective width of the flange which is defined in order to have the same total normal force in the gross flange subjected to the real transverse stress distribution as the effective flange subjected to a uniform stress equal to the maximum stress of the real transverse distribution. Some aspects concerning the shear lag phenomenon and a working example for a box girder of a heavy crane runway to illustrate the determination of the shear lag effect are also presented.

Determination of wheel loads from runway cranes based on rail strain measurement

The knowledge of the actual wheel loads resulting from the runway cranes in service is of major importance for the fatigue assessment of existing crane runway girders. Once the wheel loads are known, the global and local stress fields can be calculated based on well-known procedures.Within this paper a methodology is developed to quantify the wheel loads based on strain measurements on the rail. For cases without rail pad, only two vertical strain gauges are sufficient to calculate the wheel load, while two additional horizontal strain gauges are necessary for cases with rail pad.Experimental tests with different rail types are presented and compared with numerical calculations. Both, the borderline case of rails with ridged support and cases of rails on crane runway girders, with and without elastomeric pads, are studied in detail.

Local stresses in retrofitted crane runway girders with boxed upper flange due to eccentric wheel loading

The local stresses near the web-flange connection usually represent one of the most decisive criteria for the fatigue design of steel crane runway girders, particularly because every crane wheel induces an individual stress cycle and fatigue failure can potentially occur at any position of the girder’s length. This paper presents a crane runway girder made of steel that has been retrofitted in the past to reduce the local bending stresses in the web, because of the installation of a new, heavier crane. This was done by additional longitudinal stiffeners to form a boxed upper flange. The local vertical stresses in the girder’s web are investigated numerically and experimentally and the influence of the subsequently attached reinforcement plates, forming a boxed upper flange, is studied. Traditionally, it is state of the art to neglect any local bending stresses in the web after retrofitting the upper flange area to get a local box section. The results presented in this paper indicate that the additional local bending stresses within the upper flange box section can be significant and should not be neglected for fatigue design. Therefore, a new design concept for the calculation of the local bending stresses in webs of retrofitted crane runway girders with new boxed upper flange is presented.