The unbalanced response of a large rotor-pedestal-foundation system using an elastic half space soil model was determined. The effective stiffness and damping terms between the foundation and soil were determined from the elastic half space soil model. The rigid body equations of motion of the foundation were derived subject to applied forces from the bearing-support structure and from the springs and dashpots representing the soil. An impedance matrix representing the relationship between the bearing-support structure forces and the corresponding displacements was then derived and matched with the finite element model of the turborotor system. The analytical results of this investigation were compared with test data from a recirculating gas fan at a power plant installation. There was very good agreement between the analysis and the test data. This is the first time a realistic coupling of rotor models and foundation-soil models has been accomplished. This method of analysis should be the basis for the design of rotor-bearing-foundation-soil systems.

Compactability of asphalt concrete mixtures is critical for successful long-term performance in the field. Laboratory samples are necessary for volumetric analysis and performance testing during the design process, so the ability to quantify compactability during specimen production in the lab would be highly beneficial. While there has been significant work in defining compaction characteristics of asphalt concrete, most of this work has revolved around traditional Hot Mix Asphalt (HMA), and little work has been done with Warm Mix Asphalt (WMA) or high percentage Recycled Asphalt Pavement (RAP) mixtures. This research examined HMA without RAP (HMA Virgin), HMA with 35 % RAP (HMA RAP), and two WMA technologies with 35 % RAP (WMA 1 and WMA 2). Four compactability metrics were evaluated, including number of gyrations to 92 % density (N92), Construction Densification Index (CDI), the Construction Force Index (CFI), and the newly introduced Normalized Shear Index (NSI). This research found that the WMA technologies improved the compactability of asphalt concrete, as did the addition of RAP. In general, the WMA 1 showed better compactability than WMA 2, but this could be partially attributed to a softer binder grade, higher asphalt binder content, and the potential for a tender mix, as indicated by the normalized shear curve. The HMA RAP mixture also had a higher asphalt binder content compared to HMA Virgin, which could have contributed to the improved compactability. The NSI metric consistently showed the lowest Coefficient of Variation (COV) values and has the potential to distinguish tender mixtures.

Many aspects of balanced mix design (BMD) and performance-related quality control and quality acceptance (QC/QA) testing depend heavily on how the asphalt mixes are conditioned. There is, therefore, a critical need for practical loose mix conditioning protocols. The main objective of this study was to establish practical loose mix condition protocols for both the BMD and QC/QA phases. To develop these protocols, this paper reviewed the field performance and pavement lives of more than 200 test sections around the United States and found most of these test sections were 50-mm thick asphalt overlays where cracking is evident in 1 to 4 years. Based on this finding, the paper developed two conditioning protocols for asphalt overlays: short-term and mid-term. The short-term conditioning is intended for volumetric design, BMD rutting performance test, and QC/QA testing at asphalt plants, while the mid-term conditioning is mainly for BMD cracking performance test. A series of IDEAL cracking tests were then conducted with 13 mixes and the test results confirmed the validity of the mid-term conditioning protocol. It was also found that conditioning time affected mix cracking resistance significantly. The longer the conditioning time, the poorer the cracking resistance. When conditioned too long, the normalized cracking resistance difference among various mixes diminished. For asphalt mix composition, binder source (or quality) and asphalt absorption are two significant factors affecting the normalized cracking resistance of asphalt mixes; in contrast, mix type, asphalt binder content, and the use of rejuvenator had insignificant influence.

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