The objective of this article is to document the development of an automatic procedure for the routing of overweight vehicles with load-carrying and vertical clearance restrictions for the bridges of a highway network. The use of a network routing procedure within a geographic information system (GIS) operating in a PC environment is one of the distinctive features of the proposed approach. The procedure automatically identifies all bridges on a specified route and evaluates the adequacy of the bridge structures as well as vertical and horizontal clearance requirements for a given vehicle. A GIS computerized support methodology consistent with the Texas Administrative Code is developed. In particular, the proposed approach uses bridge load formulas to evaluate the adequacy of bridge structures for incoming overloads. Sample runs of the procedure using Texas data indicate that the procedure is computationally efficient.
A model and solution methodology are developed for determining the most cost-effective rehabilitation and replacement activities for each bridge in a large-scale Bridge Management System along an extended planning horizon. The objective of the optimization model, formulated as a multi-dimensional 0-1 knapsack problem with multiple-choice constraints, is to maximize the total effectiveness of bridge activities in the set of selected projects. The solution approach is based on a specialized branch-and-bound procedure with embedded Lagrangean relaxation. Subgradient optimization is used to solve the relaxed problem along with a set of valid inequalities obtained from a generalized network representation of the problem with the purpose of improving the bounds. Computational results indicate that large-scale problems considering one thousand bridges requiring several thousand bridge projects can be solved within 0.05 percent of the upper bounds on the objective function value in an average computer time of 49 minutes using a personal computer.
The REHAB and NULOAD computer models are combined into a new approach called RENU to forecast pavement rehabilitation costs. It incorporates the following elements: (a) revised pavement performance equations, (b) design-oriented survivor curves, and (c) a procedure to predict the increment in axle loads when higher pay loads are allowed. The most relevant contribution of the new model in the area of flexible pavements is the development of a serviceability/distress approach to investigate the effect of vehicle loading on the life cycle of highways. This approach has the capability to predict if a pavement needs light to medium rehabilitation as a result of distress signs, when the riding conditions (PSI) hve not yet reached a terminal value. The new approach is considered more reliable, for Texas flexible pavements, than the AASHTO methodology. In the area of rigid pavements the two most important improvements are the formulation of a modified AASHTO equation to include soil support values, regional factors, design characteristics, and traffic conditions typical of the Texas highway system, and the development of a failure prediction model to estimate maintenance needs. The RENU approach was built using experimental values of material properties, climatic conditions, design factors, and traffic measurements. Briefly, the overall methodology can be summarized in four steps: (a) a load distribution procedure is incorporated to investigate the shift toward higher loads if a new legal axle load limit is considered, (b) generation of a pavement performance function based upon statistical criteria, (c) generation of survivor curves to predict the extent of road rehabilitation requirements in each of the periods of a planning horizon, and (d) determination of rehabilitation costs considering life cycles for both the current and new axle load legal limits. (Authors)
A comprehensive Bridge Management System (BMS) is a rational and systematic approach for organizing and carrying out all activities related to managing a network of bridges and optimizing the selection of maintenance, rehabilitation and replacement actions resulting in maximal dollar value of benefits without exceeding available funds. The purpose of this research is to develop and computerize a multi-period optimization procedure that selects the most cost-effective set of replacement or rehabilitation projects for a State Department of Transportation, assuming that budgets are carried over from one period to the next. The solution technique uses dynamic programming in combination with an incremental benefit cost analysis. The periods of the planning horizon are considered as stages, bridge conditions (stochastic input) and available funds (deterministic input) are regarded as state variables; and project selections are treated as decision variables. The model maximizes the overall present value of net benefits associated with a network of bridges, subject to a budget constraint for each period of the planning horizon. Several system scenarios are developed to investigate the computational capability of the procedure.
Abstract An adequate and economical design for a pavement structure is just as important as one for any other engineering structure. A procedure is developed for selecting materials and thicknesses for the surface, base, and sub-base layers of flexible pavements. The problem is formulated in terms of a mathematical model. The total pavement cost is minimised subject lo a set of constraints which specify minimum requirements of the design in terms of(a)u structural number or a minimum equivalent thickness of the pavement structure, (b) total thickness of the pavement structure, and (c) thickness for each individual layer of the structure. In order to determine the optimal materials and layer thicknesses of the flexible pavement the particular structure of the model is exploited and three major cases are identified and further subdivided into 18 subcases. For a given set of data, a systematic analysis is conducted to discard those subcases that are not appropriate. The developed mathematical model and linear programming complementary slackness conditions are used for further analysis of the subcases which are not discarded. Finally, a subcase with minimum total cost of the pavement is selected and the corresponding cost-effective materials and layer thicknesses are used in the pavement design. KEYWORDS: dualitydiscrete variableshighwayslinear programmingoptimizationpavement design
Salary administration research mostly examines the compensation guides in a subjective manner and lacks quantitative approaches. Recent failure instances of salary administration demonstrate the exiguity and/or inapplicability of scientific research in this area. This research considers the core aspects of theoretical salary administration while complying with the recent competitive working environment. In this article, a mathematical optimization approach that recognizes the significance of performance and potential to future promotions of employees is proposed to find the optimal salary increase amounts and to set an advantageous schedule for salary increases. The two objectives are combined with a weight, and a sensitivity analysis shows the impact of the weight on both objectives to provide managerial guidance. The resulting raise amounts satisfy both internal alignment and external competitiveness conditions and represent employee performance and potential for promotion. The proposed mixed integer programming problem can be solved with commercial solvers quickly, even for rather large instances. The short computational time directly addresses the challenge raised by the current trend that more enterprises hire a large number of exempt employees. Additionally, two cases are presented with detailed data collection to illustrate the applications and limitations of the proposed model.
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