Runway Beams Research Articles

Viewpoint: Runway beam 'serviceability limit state' – deflection or slope?

David Edwards argues that the serviceability limit state for runway beams should be considered to be slope, not deflection, meaning that current limitations are overly conservative in most cases.

Failure and repair analysis of a runway beam: Influence of the standard applied to lifetime prediction

The structural integrity of a welded structure is guaranteed insofar as the integrity of any particular welded detail is ensured. This is highlighted in this paper which analyzes the premature failure of a runway beam, occurring only two years after being commissioned. Initial fractographic analysis and visual in-situ inspection of the beam suggest that the failure was caused by fatigue. The fracture initiated in an apparently innocuous zone where the beam joins a twin runway beam, the bracing of which is performed by a transverse truss beam with fillet welds.The failure analysis was performed according to two standards specific to runway beam design: the former Spanish UNE 76202:1992 standard, applicable at the time the beam was built, and the current EN 1993-1-9:2005 standard. The main difference between the two standards consists in the load spectrum considered for calculations. While UNE 76202:1992 prescribes a defined combination of the most unfavorable loads, EN 1993-1-9:2005 leaves to the designer’s discretion the choice of more realistic load data directly derived from in-service observations or measurements, which presumably better reflect the loads the beam will have to support throughout its service life.To achieve this goal, once the beam was repaired and operating once again, in-service strain measurements were performed over several days. These measurements allowed us to obtain a real load spectrum, which was taken into consideration in fatigue strength assessment based on the EN 1993-1-9:2005 standard. The results provide a more realistic fatigue life prediction than that obtained using UNE 76202:1992, a standard no longer applicable.

Proposal of a condition index for maintenance of runway beams

Condition-based maintenance is a maintenance philosophy based on systematic visual inspection and condition ratings. Condition-based maintenance requires specific visual inspection protocols and condition rating models calibrated for each type of infrastructure. The purpose of this study is to explore the development of a method for estimating the current condition of a type of infrastructure based on visual inspection and expert judgement. A condition index, based on the condition-based maintenance philosophy, is proposed for use in assessing the current condition of a type of infrastructure and establishing maintenance strategies such as rehabilitation, reconstruction and restoration. The method was applied to runway beams fabricated in a steelworks company in Chile. Two models – a linear model and a dichotomic model – were calibrated and the correlation coefficients obtained were 0·9 for both models. It is thus concluded that the method is suitable and easily applicable under the condition-based maintenance concept. Further research is needed to improve the model by including maintenance costs.

Impaired motor activity and motor learning function in rat with middle cerebral artery occlusion

The poor quality of life after a stroke is largely attributed to deficits in cognitive-motor functioning. The goals of this study were to detect if damaged motor learning function were attributed to motor deficits in rats following a transient middle cerebral artery (MCA) occlusion. Stroke was induced by a 2-h occlusion of the MCA using an intraluminal filament. Motor functions were evaluated from 5 up to 28 days after reperfusion in ischemic and control rats. Motor function was detected by a series of motor tests (runway traversing and beam balancing, as well as foot fault placing, parallel bar crossing, rope and ladder climbing), and motor learning behavior was determined by analyzing the rate of improvement of impaired function during performance of the motor tasks. Significant ( P<0.001) motor deficits were detected in the stroke group ( n=10) while performing motor tasks that involve extensive coordination, in comparison to the controls ( n=12). Although motor behavior was improved with repeated behavior testing, unparalleled rate of improvement of motor performance on rope and ladder climbing tests was found between the two groups, suggesting an impaired motor learning function. Brain tissue damage was detected in the ischemic animals 28 days after surgery, demonstrated by 40% infarct volume of contralateral hemisphere. Both motor learning and motor function were impaired in ischemic rats. The motor tests used in this study are sensitive, semi-quantitative, and reproducible measurements of functional impairment in rats following an ischemic stroke.

Design of Crane Runway Beam with Channel

A common practice in industrial buildings is to weld a channel, open side down, to the top flange of a standard rolled beam for use as a crane runway. In many cases, it is not possible to brace a crane runway laterally between columns, so the channel provides additional lateral stiffness. There are several interesting structural questions associated with the practice, like, what should be the welding pattern? How are the residual stresses affected? What if the channel has a yield strength different from the beam? However, the primary question addressed in this paper is, how does one check such a beam for lateral-torsional buckling?

The Warping Constant for the W-Section with a Channel Cap

It is common practice in crane runway beams to place a channel, open-side down, over the top flange of a W-section to increase its lateral stability. This is done because it is not always convenient to brace the compression flange between columns. The lateral-torsional buckling capacity of a singly symmetric section may be determined by the formulas without knowing the warping section constant. However, these formulas were developed from research on three-plate mono-symmetric sections. If one is to develop a similar equation for the case of the W-section with a channel cap, it is necessary to return to the basic theory of lateral-torsional buckling and that means that one must calculate the warping constant (Cwc) for the cross-section. It is not a difficult matter to do this with a computer, but since the program may not be available to everyone, it would be useful to develop a simple empirical equation for preliminary design, making use of the section properties already given in the AISC steel manual.