113 Fatigue

A structural member subjected to cyclic loadings may eventually fail through initiation and propagation of cracks. This phenomenon is called fatigue and can occur at stress levels considerably below the yield stress.

Extensive research programs conducted to determine the fatigue strength of structural members and connections have provided information on the factors affecting this property. These programs included studies of large-scale girder specimens with flange-to-web fillet welds, flange cover plates, stiffeners, and other attachments. The studies showed that the stress range (algebraic difference between maximum and minimum stress) and notch severity of details are the most important factors. Yield point of the steel had little effect. The knowledge developed from these programs has been incorporated into specifications of the American Institute of Steel Construction, American Association of State Highway and Transportation Officials, and the American Railway Engineering and Maintenance-of-Way Association, which offer detailed provisions for fatigue design.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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