Assessment of Existing Steel Structures - Recommendations for Estimation of the Remaining Fatigue Life

Due to the demand for freight volume on rail and road, traffic has increased significantly in the past years leading to an increasing number of heavy vehicles in the traffic flows and greater exploitation of their loading capacities. Because of environmental considerations there is also a tendency to further enhance the admissible loads in the design of new heavy vehicles (e.g. by increasing axle loads or using road trains). This all may affect the safety, serviceability and durability of existing bridges. Bridge authorities are therefore interested in agreed methods to assess the safety and durability of existing bridges and to make appropriate provisions for more refined maintenance methods, possible restriction of traffic, bridge-rehabilitation or substitution of old bridges by new ones where necessary. For steel bridges including the old riveted ones there are numerous approaches to such assessments, partly standardized by national codes or recommendations. In the light of the development of the European single market for construction works and engineering services there is thus a need to harmonize them and to develop agreed European technical recommendations for the safety and durability assessment of existing structures. These recommendations should follow the principles and application rules in the Eurocodes and provide a scheme with different levels of analysis: a basic level with general methods and further levels with higher sophistication that call for specific expertise. This technical report on ¿Recommendations for the estimation of remaining fatigue life¿ supported by the ECCS could be used as a basis for harmonizing National procedures and for the further evolution of the Eurocodes.JRC.G.5-European laboratory for structural assessmen

Spatial and temporal changes in cumulative human impacts on the world's ocean

Human pressures on the ocean are thought to be increasing globally, yet we know little about their patterns of cumulative change, which pressures are most responsible for change, and which places are experiencing the greatest increases. Managers and policymakers require such information to make strategic decisions and monitor progress towards management objectives. Here we calculate and map recent change over 5 years in cumulative impacts to marine ecosystems globally from fishing, climate change, and ocean- and land-based stressors. Nearly 66% of the ocean and 77% of national jurisdictions show increased human impact, driven mostly by climate change pressures. Five percent of the ocean is heavily impacted with increasing pressures, requiring management attention. Ten percent has very low impact with decreasing pressures. Our results provide large-scale guidance about where to prioritize management efforts and affirm the importance of addressing climate change to maintain and improve the condition of marine ecosystems

Strength and shape of the magnetic field of the Fermilab main injector dipoles

Measurements of 230 6-meter and 136 4-meter dipoles constructed for the Fermilab Main Injector were carried out as part of the magnet production effort. An automated measurement system provided data on magnetic field strength and shape using several partially redundant systems. Results of these measurements are available for each individual magnet for use in accelerator modelling. In this report we will summarise the results on all of the magnets to characterise the properties which will govern accelerator operation

Probabilistic models to evaluate effectiveness of steel bridge weld fatigue retrofitting by peening

The purpose of this study was to evaluate, with two probabilistic analytical models, the effectiveness of several alternative fatigue management strategies for steel bridge welds. The investigated strategies employed, in various combinations, magnetic particle inspection, gouging and rewelding, and postweld treatment by peening. The analytical models included a probabilistic strain-based fracture mechanics model and a Markov chain model. For comparing the results obtained with the two models, the fatigue life was divided into a small, fixed number of condition states based on crack depth, similar to those often used by bridge management systems to model deterioration due to other processes, such as corrosion and road surface wear. The probabilistic strain-based fracture mechanics model was verified first by comparison with design S-N curves and test data for untreated welds. Next, the verified model was used to determine the probability that untreated and treated welds would be in each condition state in a given year; the probabilities were then used to calibrate transition probabilities for a much simpler Markov chain fatigue model. Then both models were used to simulate a number of fatigue management strategies. From the results of these simulations, the performance of the different strategies was compared, and the accuracy of the simpler Markov chain fatigue model was evaluated. In general, peening was more effective if preceded by inspection of the weld. The Markov chain fatigue model did a reasonable job of predicting the general trends and relative effectiveness of the different investigated strategies

A probabilistic model for determining the effect of post-weld treatment on the fatigue performance of tubular bridge joints

Herein, a probabilistic model for predicting the effect of post-weld treatment on the fatigue performance of the welded joints in tubular truss bridges is described. Specifically, a probabilistic LEFM-based model is first developed for the fatigue analysis of single untreated and treated crack sites in tubular K-joints. A systems reliability approach is then proposed for the analysis of tubular structures with multiple potential crack sites. Using this approach, it is then demonstrated that significant improvements in the fatigue reliability of tubular joints with dimensions common to bridge structures can be obtained with post-weld treatment, even when the influences of the various untreated and treated potential crack sites are considered

Poly(dimethylsiloxane)-Stabilized Polymer Particles from Radical Dispersion Polymerization in Nonpolar Solvent: Influence of Stabilizer Properties and Monomer Type

Particles used in electrophoretic display applications (EPD) must possess a number of specific properties ranging from stability in a nonaqueous solvent, high reflectivity, low polydispersity, and high charge density to name but a few. The manufacture of such particles is best carried out in the solvent of choice for the EPD. This opens up new interests in the study of nonaqueous dispersion polymerization methods, which deliver polymer particles suspended in low dielectric constant solvents. We explore in this article the use of a poly(dimethylsiloxane) macromonomer for the stabilization of poly(methyl methacrylate) polymer particles in dodecane, a typical solvent of choice for EPDs. The use of this stabilizer is significant for this method as it is directly soluble in the reaction medium as opposed to traditionally used poly(12-hydroxystearic acid)-based stabilizers. Additionally, the present study serves as a baseline for subsequent work, where nonaqueous dispersion polymerization will be used to create polymer particles encapsulating liquid droplets and solid pigment particles. In this article, the influence of the macromonomer molecular weight and concentration on the properties of the synthesized particles is studied. In addition, we investigate the possibility of synthesizing polymer particles from other monomers both as a comonomer for methyl methacrylate and as the only monomer in the process. The influence of macromonomer concentration is also studied throughout all experiments