Dynamic Behavior and Fatigue Life of Highway Bridges Due to Doubling Heavy Vehicles

An increase in the demand for the freight shipping in the United States has been predicted for the near future and Longer Combination Vehicles (LCVs), which can carry more loads in each trip, seem like a good solution for the problem. Currently, utilizing LCVs is not permitted in most states of the US and little research has been conducted on the effects of these heavy vehicles on the roads and bridges. In this research, efforts are made to study these effects by comparing the dynamic and fatigue effects of LCVs with more common trucks. Ten Steel and prestressed concrete bridges with span lengths ranging from 30’ to 140’ are designed and modeled using the grid system in MATLAB. Additionally, three more real bridges including two single span simply supported steel bridges and a three span continuous steel bridge are modeled using the same MATLAB code. The equations of motion of three LCVs as well as eight other trucks are derived and these vehicles are subjected to different road surface conditions and bumps on the roads and the designed and real bridges. By forming the bridge equations of motion using the mass, stiffness and damping matrices and considering the interaction between the truck and the bridge, the differential equations are solved using the ODE solver in MATLAB and the results of the forces in tires as well as the deflections and moments in the bridge members are obtained. The results of this study show that for most of the bridges, LCVs result in the smallest values of Dynamic Amplification Factor (DAF) whereas the Single Unit Trucks cause the highest values of DAF when traveling on the bridges. Also in most cases, the values of DAF are observed to be smaller than the 33% threshold suggested by the design code. Additionally, fatigue analysis of the bridges in this study confirms that by replacing the current truck traffic with higher capacity LCVs, in most cases, the remaining fatigue life of the bridge is only slightly decreased which means that taking advantage of these larger vehicles can be a viable option for decision makers.

Profiling The Campus Recruiter At A Four-Year Hospitality Program

Profiling the Campus Recruiter At a Four-Year Hospitality Program, is a written profile, supported by anecdotal rather than stridently empirical evidence, by Al lzzolo, Assistant Professor, College of Hotel Administration, University of Nevada, Las Vegas. “Each year major chain corporations as well as single unit companies interview hospitality students throughout the country. A study conducted at the University of Nevada, Las Vegas, was designed to profile the hospitality industry campus recruiter and to provide meaningful data to college students who would be interviewing with these recruiters,” the author initially proffers. “Recruiting at the four-year hospitality program, by its nature, is not a science, nor is it highly quantifiable. The interviewing and selection processes are highly subjective and vary from company to company,” says Izzolo to preface his essay. “Data were collected via a questionnaire specifically designed to answer questions about the recruiters and/or the companies that sent interviewers to the placement office of the university's hospitality program,” our author says to explain the process used to gather information for the piece. Findings of the study indicate that the typical recruiter is male, college educated – but not necessarily in a Hospitality’ curriculum – and almost 80 percent of respondents said they had the authority to hire management trainees. Few campuses are visited by hospitality industry recruitment staff as evidenced by Izzolo’s observations/data. Table 3 analyzes the desirable traits a recruiter deems appropriate for the potential employee candidate. Personal appearance, work experience, grade point average, and verbal communication rank high on the list of distinguishable attributes. The most striking finding in this portion of the study is that a student’s GPA is virtually ignored. “Recruiting for the hospitality industry appears to be very subjective,” Izzolo says. “Recruiters are basing decisions to hire not on knowledge levels as determined by an academic grade point average but rather on criteria much less definitive, such as verbal skills and personal appearance,” our author opines. In closing, Izzolo concedes this is not a definitive study, but is merely a launching pad to a more comprehensive investigation on the recruitment subject.

Maximizing Hospitality Learning Outcomes: An Integrated Experiential In-Class Approach

This study explored the influence of an experiential, in-class approach to the hospitality curriculum as a means of increasing its efficiency and effectiveness. Specifically, the study provides an example of how hospitality faculty might utilize an experiential, in-class approach to integrate additional hospitality-specific content along with process and content issues for working in teams and team decision-making. The results of this study support the efficient and effective use of an experiential inclass teaching method. The value of this study is twofold: (1) it provides an initial test of this approach’s usefulness and (2) it provides a forum for continued conversations of how experiential approaches can be utilized to enhance and reinforce other hospitality content and managerial skills and to bridge the gap between vocational and liberal education outcomes.

Large-Scale Testing to Study the Effects of Critical Parameters on the Aerodynamic Behavior of Long Span Bridges

Long-span bridges are flexible and therefore are sensitive to wind induced effects. One way to improve the stability of long span bridges against flutter is to use cross-sections that involve twin side-by-side decks. However, this can amplify responses due to vortex induced oscillations. Wind tunnel testing is a well-established practice to evaluate the stability of bridges against wind loads. In order to study the response of the prototype in laboratory, dynamic similarity requirements should be satisfied. One of the parameters that is normally violated in wind tunnel testing is Reynolds number. In this dissertation, the effects of Reynolds number on the aerodynamics of a double deck bridge were evaluated by measuring fluctuating forces on a motionless sectional model of a bridge at different wind speeds representing different Reynolds regimes. Also, the efficacy of vortex mitigation devices was evaluated at different Reynolds number regimes. One other parameter that is frequently ignored in wind tunnel studies is the correct simulation of turbulence characteristics. Due to the difficulties in simulating flow with large turbulence length scale on a sectional model, wind tunnel tests are often performed in smooth flow as a conservative approach. The validity of simplifying assumptions in calculation of buffeting loads, as the direct impact of turbulence, needs to be verified for twin deck bridges. The effects of turbulence characteristics were investigated by testing sectional models of a twin deck bridge under two different turbulent flow conditions. Not only the flow properties play an important role on the aerodynamic response of the bridge, but also the geometry of the cross section shape is expected to have significant effects. In this dissertation, the effects of deck details, such as width of the gap between the twin decks, and traffic barriers on the aerodynamic characteristics of a twin deck bridge were investigated, particularly on the vortex shedding forces with the aim of clarifying how these shape details can alter the wind induced responses. Finally, a summary of the issues that are involved in designing a dynamic test rig for high Reynolds number tests is given, using the studied cross section as an example.