Spectral matching, the process of modifying a seed acceleration time history in intensity and frequency content until its acceleration response spectrum matches a target spectrum, is used extensively in practice. Predictive equations that quantify the impact of spectral matching on the peak ground velocity, peak ground displacement, Arias intensity, and cumulative absolute velocity of a scaled seed time history have been developed and validated on the basis of thousands of matched motions, three different earthquake scenarios, and numerous target spectra. It is found that spectral mismatch is the most critical factor affecting the changes in ground motion characteristics. The technique used for modification (e.g., time domain or frequency domain) is in many cases not critical. Based on the results, recommendations in order to minimize the impact of matching on the ground motion characteristics are provided.

Wind turbines are becoming a larger source of renewable energy in the United States. However, most of the designs are geared toward the weather conditions seen in Europe. Also, in the United States, manufacturers have been increasing the length of the turbine blades, often made of composite materials, to maximize power output. As a result of the more severe loading conditions in the United States and the material level flaws in composite structures, blade failure has been a more common occurrence in the U.S. than in Europe. Therefore, it is imperative that a structural health monitoring system be incorporated into the design of the wind turbines in order to monitor flaws before they lead to a catastrophic failure. Due to the rotation of the turbine and issues related to lightning strikes, the best way to implement a structural health monitoring system would be to use a network of wireless sensor nodes. In order to provide power to these sensor nodes, piezoelectric, thermoelectric and photovoltaic energy harvesting techniques are examined on a cross section of a CX-100 wind turbine blade in order to determine the feasibility of powering individual nodes that would compose the sensor network.

An earlier exploratory study on the effects of restraint of thermal expansion on the fire resistance of prestressed concrete showed that for similar specimens, made of normal weight concrete, maximum thermal thrust was a function of the allowed linear expansion. In the present study, data were obtained for three additional groups of specimens: lightweight prestressed, lightweight reinforced, and normal weight reinforced. A method is presented for estimating the maximum thermal thrust that occurs during a fire test of a concrete floor, roof, or beam. Results of 12 fire tests of restrained concrete flexural members indicate that the method predicts the maximum thrust within about 15 percent. The method is applicable to specimens restrained both longitudinally and laterally as well as those restrained in only one direction. The method underestimates thrust for specimens with embedded underfloor ducts and overestimates thrust for specimens partly insulated from direct contact with the fire. In all 43 fire tests the specimens supported their loads considerably longer than would have been anticipated for either simply supported or fully restrained conditions.

When fire occurs in a building, the structural parts tend to expand under the effects of the resulting heating. Thermal expansion of structural building components may be variously restricted according to the resistance offered at the supports or by the stiffness of abutting constructions. Restriction of thermal expansion has been shown by many fire tests and by evidence from building fires to have an important influence on the structural behavior of building elements during exposure to fire. Described in this paper are results and impressions gained in an exploratory study of the effect of varying intensities of restraint of the thermal expansion of precast, prestressed concrete double-tee floor elements during the course of standard fire exposures. The principal variable in the study was the amount of linear expansion along the axis of the span allowed before further expansion was stopped. Relationships between given expansions, the resulting expansion forces, and midspan deflection are presented. The changes in the location of the center of thrust at the ends of the members during the course of the fire exposure are discussed. Further investigations on the subject of restraint are suggested.

Ground motion modification (or spectral matching) has been criticized, but has many appealing characteristics and is widely used in practice. Modification of ground motions can be performed in either the time domain or the frequency domain. Depending on the choice of modification technique, modified ground motions can be significantly different from each other as well as from the original ground motion. This paper studies the impact of these differences on seismic geotechnical analyses for two different site profiles using two earthquake scenarios and a total of 20 ground motions. This study shows that the final results are influenced by many factors such as the original (seed) ground motion, the target spectrum, and the local site conditions, in addition to the ground motion modification technique used. The results also show that while both techniques can significantly modify the original ground motion, neither technique is consistently more conservative than the other. Therefore, a general conclusion that a particular technique results in ground motions that yield the largest intensity parameters cannot be made a priori.