This study aims to compare different historical predictive master curve techniques which model the rheological properties of asphalt binders in terms of dynamic shear modulus (G*). The investigated models are the Sigmoidal model, Generalized Logistic Sigmoidal model (GLS), Christensen-Anderson model (CA), and Christensen-Anderson and Marasteanu (CAM) model. These models are applied on virgin and sulfur-extended asphalts (SEA). Two types of recycled plastic waste; recycled high-density polyethylene (RHDPE) and recycled low-density polyethylene (RLDPE) are used to modify both the virgin asphalt and SEA. The investigated models are employed to describe the rheological viscoelastic characteristics of the different investigated binders at different aging conditions under the influence of different frequencies and temperatures based on dynamic mechanical analysis (DMA). The results of this study show that the performance of the investigated models is affected by binder modification and aging conditions. The G* of virgin and sulfur asphalts (either modified or virgin) can be satisfactorily represented by all models investigated in this study under original and aged conditions. The most accurate model is the generalized modified sigmoidal model followed by the Sigmoidal model, the CAM Model, and CA Model, respectively

This research evaluates the rheological properties of virgin asphalt and sulfur extended asphalt (SEA) modified with two types of recycled plastic waste (rPW). The investigated plastic wastes are the recycled low-density polyethylene (rLDPE) and recycled high-density polyethylene (rHDPE). It also assesses the environmental and economic benefits of recycling such materials. A total of 16 modified binder samples are produced by adding rLDPE and rHDPE modifiers to virgin asphalt and SEA in four different concentrations of 2%, 4%, 6%, and 8% by weight of asphalt. The basic and rheological properties of the virgin and modified asphalts are explored by conventional tests, and advanced rheological tests at different aging conditions. Finally, cost-effectiveness and environmental analyses are conducted. The environmental benefit analysis is performed by comparing carbon and non-methyl volatile organic compound (NMVOC) emission from the various recycled polyethylene (rPE) with the manufacturing process of the same quantities of virgin LDPE and HDPE when used to modify asphalt. The effect of incorporating sulfur into virgin asphalt on the environment is also determined. Results show that modification yields a higher binder complex shear modulus (G*) and a lower loss tangent (tan δ) at all traffic speeds meaning improved rut resistance behavior under heavy traffic loading and high temperature conditions. About 29% reduction in material cost occurs when rPE-modified SEA is used instead of virgin asphalt. The environmental and economic analyses show that using SEA modified with rPE for road construction is an economic, sustainable, and ecological alternative with better performance compared to virgin asphalt.

This paper documents the testing of six 20 ft × 4 ft × 8 in. (6.1 m × 1.2 m × 203.2 mm) precast, prestressed concrete sandwich panels constructed with continuous rigid insulation and a carbon-fiber-reinforced polymer grid shear transfer mechanism. All panels were identical except for foam type and were cast together on the same prestressing bed. Three of the six panels were fabricated with expanded polystyrene (EPS) foam insulation, and the remaining three panels were fabricated using sandblasted extruded polystyrene (XPS) foam. For each group of three panels, one was tested to failure as a control and two others were cycled 2 million times to 45% of their design ultimate load before failure testing. The tested EPS panels all failed when the applied lateral load was greater than or equal to 100 lb/ft² (4.79 kPa), which is 2.35 times their design load of 42.5 lb/ft² (2.03 kPa). The tested XPS panels all failed at the equivalent of 175 lb/ft² (8.38 kPa) of applied lateral pressure, which is more than 4.0 times their design load of 42.5 lb/ft². All four panels subjected to fatigue survived 2 million lateral load cycles without any visible signs of degradation.

The design procedure presented in the seventh edition of the PCI Design Handbook: Precast and Prestressed Concrete for ledges of L-shaped beams has been called into question by many engineers and researchers. Research findings from previous experimental studies have indicated that the PCI ledge design equations can overestimate ledge punching shear strength. This paper presents the development of the design procedure for the eighth edition of the PCI Design Handbook to evaluate the punching shear strength of ledges of L-shaped beams. Based on the failure surfaces observed throughout a comprehensive experimental program, an idealized failure surface was determined. The results of extensive finite element analyses and a large experimental program were used to evaluate the effects of global stress on ledge capacity, and a procedure to evaluate the punching shear strength of the ledge was developed. The proposed procedure is presented in this paper and is intended to provide an improved margin of safety for ledge capacity under a wide range of loading conditions. Consideration was given to ensure simplicity and practicality of the proposed design procedure.

The ledge design procedure in the seventh edition of the PCI Design Handbook: Precast and Prestressed Concrete has been called into question by several engineers and researchers since 1985. Specifically, the ledge punching-shear capacities predicted by the PCI procedure overestimate the failure loads observed in several previous laboratory tests and analytical studies. This paper presents the results of the second phase of an extensive experimental program conducted on nine fullscale, long-span, L-shaped beams with ledge heights from 8 to 18 in. (200 to 450 mm). The main objectives of this study were to investigate the effects on ledge capacity of several significant parameters, such as global stress, prestressing, ledge height, and concrete strength. In addition, the study also investigated the efficiency of selected special reinforcement details. The experimental results demonstrated that increasing the global stress significantly reduces ledge capacity, while the use of prestressing increases the capacity. The research also demonstrated that concentrating the ledge reinforcement at the load location can significantly increase the ledge capacity, offering a practical design alternative for carrying heavy loads.

The design procedure for ledges of L-shaped beams presented in the seventh edition of the PCI Design Handbook: Precast and Prestressed Concrete has been called into question by many engineers and researchers. Research findings from previous experimental studies have indicated that the ledge design equations provided in the seventh edition of the PCI Design Handbook overestimate the ledge punching-shear capacity. This paper presents the findings of the first phase of a comprehensive experimental program conducted with the objective of developing design guidelines for the ledges of L-shaped beams. In this first phase of study, short-span beams were used to minimize the effect of global stresses and the cost of testing, thus allowing for a larger number of parameters to be examined. The main objectives of this study were to investigate the ledge behavior and the configuration of the failure surface. In addition, the study also investigated the effect of various parameters believed to affect ledge behavior. The study also investigated the performance of special reinforcement details toward the development of detailing recommendations for ledge reinforcement. Research findings indicate that even with low levels of global stress, the ledge design procedure provided in the seventh edition of the PCI Design Handbook could overestimate the ledge capacity. Furthermore, the observed failure surface was generally larger than the assumed surface specified by the PCI procedure. The study also found that several parameters affected the ledge capacity but are not considered by the PCI procedure. Finally, the study also demonstrated that certain reinforcement details can be used to improve the ledge behavior and to enhance the ledge capacity.

Droop control has been widely used as a load-sharing method between paralleled power sources in DC microgrid due to its modularity and reliability. Existing droop gains design methods rely on computationally intensive supervisory control algorithms and knowledge of sub-system parameters.This paper presents a streamlined design approach for optimal droop gains, relying only on the knowledge of the parameters of the local converter power losses model in order to achieve minimum power losses for a More Electric Aircraft (MEA) DC microgrid. Additionally, a simplified, but sufficiently accurate, converter losses model is proposed in this paper for optimal droop gains design. The proposed converter losses model consists of two parts; no-load losses, and losses which are represented by Equivalent Series Resistance (ESR). The proposed design approach analyses show that setting the optimal droop gains equal to the converter ESR will achieve minimum overall DC microgrid power losses without the need for any additional information on the DC transmission line parameters. The effectiveness of the optimal droop gains design method is tested in a simulation environment and evaluated experimentally using a laboratory DC microgrid test rig.