Experimental Analysis of The Behaviour of Aluminium Alloy EN6082AW T6 at High Temperature

The paper presents test results for the mechanical and creep properties of European aluminium alloy EN6082AW T6 at high temperatures. Mechanical properties of the aluminium alloy were determined by means of two types of test: constant stress-rate and stationary creep tests. Mechanical properties were determined up to a temperature of 350°C, while the creep tests were conducted within the temperature interval 150-300°C. The creep tests conducted have identified the critical temperature interval for creep development, which represents an important factor when analysing creep behaviour of aluminium structures. This temperature interval was found to be within the range 200-300°C. Test results for stress at 0.2% strain and modulus of elasticity at different temperatures have shown good agreement with the codified values from Eurocode 9 and with other comparable studies

Changes to the lambda model for fatigue loads on steel railway bridges in Europe

For the fatigue design of steel railway bridges in Europe, the European standards EN 1991-2 and EN 1993-2 provide a factored Load Model '71, called the lambda model. The stress range in the fatigue detail of study should be determined with this model. Engineers can easily verify their structural design for fatigue by comparing this stress range to the fatigue reference strength of the detail.This paper compares the load effect caused by the lambda model with the load effect of actual trains measured with ‘Weigh In Motion’ systems during 7 years at 81 locations in the rail network of The Netherlands. Locations with heavy loads are selected and their load effects in terms of stress ranges and fatigue damage are determined for various influence lines, including one, two and three span beams with spans ranging between 1 and 150 m. The design (i.e. elastic section modulus) is optimized such that the calculated fatigue damage using the damage accumulation rule of Palmgren Miner equals 1 for a 100 years design life for these locations. This elastic section modulus is compared to the elastic section modulus obtained by designing according to the lambda model.Improvements are proposed to the lambda model based on this comparison, such that the resulting design gives a reasonable agreement with the design based on measured loads, while maintaining the current ease of use of the lambda model. Uncertainties such as possible changes in axle loads and train speeds in future are taken into account

Probabilistic fatigue life updating accounting for inspections of multiple critical locations

Many steel structures contain multiple fatigue sensitive details that have similar geometries and are subjected to similar load fluctuations. Examples are orthotropic (bridge) decks and stiffened (ship) hulls where tens to thousands of similar details are present in one structure. Generally only visual inspections on fatigue cracks are considered for these structures because more accurate techniques are considered to be too expensive and time consuming when so many details need to be inspected. Visual inspections are known to have a low probability of detection. Consequently Bayesian update techniques usually show a marginal effect of the result of visual inspections on the reliability of structures with respect to fatigue failure. On the other hand the inspection result of one location also provides information on similar details at other locations and thus the significance of the inspection result may be larger if multiple potential crack locations occur and cracks are not detected at any of these locations. This paper provides a probabilistic fatigue crack growth (fracture mechanics) model of a system containing a fatigue sensitive detail at multiple locations that accounts for the results of inspections. Spatial correlations of loading, resistance, and uncertainty variables between the different locations are evaluated and estimated through a literature review and are accounted for in the model. The model is demonstrated on a practical example of an orthotropic bridge deck containing a detail at 100 locations. The paper shows that visual inspections may be effective provided that a certain minimum inspection reliability can be guaranteed, that the structure is relatively tolerant to large cracks, and that the geometry and loading conditions are similar for a large number of locations

Inspectie-interval is geen toeval – vermoeiing van bruggen (2) : bepalingsmethode voor stalen brugdekken

Het verstrijken van de vermoeiingslevensduur vna stalen verkeersbruggen stelt beheerders ervan voor een aantal dilemma's. Wanneer moet ik de eerste inspectie laten plaatsvinden en bij welke details? Wat is het inspectie-interval voor voldoende veiligheidsniveau? Als er een scheur gevonden wordt, hoeveel tijd heb ik om een reparatie uit te voeren? Welke inspectiemethode moet ik toepas-sen? Dit artikel geeft een (berekenings)methode om een gefundeerd antwoord te kunnen geven op deze vragen

Fire exposed aluminium structures

Material properties and mechanical response models for fire design of steel structures are based on extensive research and experience. Contrarily, the behaviour of aluminium load bearing structures exposed to fire is relatively unexplored. This article gives an overview of physical and mechanical properties at elevated temperature of frequently applied aluminium alloys, found in relevant literature and discusses mechanical response models currently applied for fire exposed aluminium structures. A comparison is made with steel structures exposed to fire

Fatigue assessment for deck plates in orthotropic bridge decks

Since the 1960s, orthotropic deck plates of highway bridges have been built with large cold-formed trapezoidal stiffeners supporting a deck plate with a thickness of approx. 12 mm. The maximum cross-beam spacing is approx. 4 m. A number of these bridge decks in The Netherlands suffer from fatigue cracks in the deck plate. First cracks have been observed after about 30 years in service. In one particular movable bridge, the cracks were found after only seven years. In many other countries, this type of crack has not yet been observed. This article provides a fatigue assessment procedure for deck plates. The procedure is calibrated with the conditions and observations in The Netherlands. It gives a fatigue life prediction and takes account of inspection results quantitatively. Although aspects such as the type and thickness of the surface finishes and the traffic load may vary between countries, the principles of the assessment procedure in this article are generally applicable and can be used to identify reasons for differences in fatigue life and to develop strategies for increasing the life