A procedure enabling the identification of the mass/inertia, damping and stiffness matrices for mechanical systems or the analogous inductance, resistance and capacitance matrices for electrical, fluid or thermal systems from measured results is developed. Analytical constraints that are mandatory are defined. Illustrative examples are provided.
Flexural beam fatigue testing of asphalt mixtures has been used for nearly 40 years in the pavement industry. Since the development of the test, the definitions of initial and failure stifnesses have not been verified or validated in any comprehensive study. The main objective of this study is to validate the criteria used to define the initial and the final stiffnesses in flexure fatigue testing. In this study, extensive flexure fatigue tests were performed on five typical dense-graded mixtures and an asphalt rubber gap-graded mixture. An optimization approach was used, in which different intial and failure conditions were assumed. Fatigue models were developed using linear regression curve fitting and the conditions that produced the best fit were selected. Both the phenomenological and the dissipated energy approaches were used. Test results conclusively indicated that the initial stiffness should be defined at cycle number 50. In addition, when a phenomenological approach for fatigue is employed, the fatigue stiffness should be taken at 50% of the initial stiffness.A stiffness degradation model was developed, which provided an independent proof that failue occurs when the stiffness of the beam is reduced to 50% of the initial stiffness. This model represents a basic material propertey at which damage accumulation in the mixture has produced an inability of the mix to resist further damage independent of the mode of loading. In contract to the tensile strain-failure approach, data analysis with the energy approach showed that fatigue failure stiffness, taken at 30% of the initial stiffness, provided identical fatigue energy failure regardless of constant stress or strain mode of loading. The results show that the phenomenological and energy approaches provide different definition of failure and the test should be consistent with the method of analysis used.
Industrial wastes and byproducts have to be disposed off properly so that their environmental impacts are minimized. Alternatively, some of these materials can be utilized in recycling processes, manufacturing of new products, or as construction materials. This paper presents an effective way of utilizing the steel slag aggregate (SSA), which is a byproduct of the steel manufacturing process, in road construction. A comprehensive study was conducted to characterize SSA and determine the potential for its use in road bases. Testing results indicated that SSA is an environmentally safe product and has physical and chemical properties that make it an excellent candidate for road base construction. Laboratory and field data have shown the superior performance of SSA over the locally available calcareous sediments. The resulting California Bearing Ratio values are doubled and the water sensitivity is much less when using SSA instead of the local calcareous material.
In this study, the effect of antistrip additives on asphalt binders was evaluated by both laboratory tests and a proposed chemical model of asphalt binder based on the surface free energy characteristics. Two performance graded asphalt binders, namely, PG 64-22 and PG 70-28 and two amine-based liquid antistrip additives, namely, AD-Here HP Plus and Redicote E-6 were evaluated at different percentages (0.25 %, 0.75 %, and 1.5 %). It was found that 1.5 %AD-Here HP Plus and 1.5 % Redicote E-6 increased the total SFE of PG 64-22 by 67 % and 208 %, respectively. Also, the acid components of PG 64-22 and PG 70-28 are 2.9 dyne/cm and 2.5 dyne/cm, respectively, whereas, the corresponding base components are 0.4 dyne/cm for both. With the addition of 1.5 %. Redicote E-6 in PG 64-22, the acid component of the binder reduced by 92 % and the base component of the binder increased by 1141 %.
Process mechanical system models are considered and the techniques for analysis are discussed. A method for the investigation of system models which possess multiple degrees of freedom is outlined. To illustrate this general procedure the dynamical response of a pulp blender-beater, with dual impellers and five degrees of freedom, for paper and board manufacturing is computed.
This study investigated the effects of applying three different types of rejuvenators on a highly aged parking lot pavement, which had shown some severe raveling. Cores were taken from the pavement before and after the treatments to examine the effects of these treatments. Tests were performed to determine the viscosity of the recovered asphalt binders from different layers of the pavement before and after the treatment. Right before coring, the surface texture and skid resistance were measured to assess whether the treatment had adversely affected the frictional properties of the pavement.
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