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Description of LARS Analysis
The basic analysis methods (i.e., section property, influence lines, and dead load and live load analysis) of the Load Analysis Rating System (LARS) are very similar to those that have been employed in BARS. The majority of analysis results are presented in LARS reports that have headings and labels that fairly clearly describe the associated data. The key values that control the evaluation of the bridge are the moment capacity and available capacity for Live Load + Impact (LL + IMP). These results are produced by executing calculations that are defined by the AASHTO Bridge Specifications, while using the data describing member section properties and the moment and shear values that are applied to the section being analyzed. The calculations are intermixed with logical tests of the intermediate results of the calculations. These logical tests guide the analysis to the various calculations that relate to the type of member section (e.g., non-composite, composite, compact, braced non-compact or unbraced non-compact for steel) within a material of construction type (i.e., for steel, composite steel and concrete, reinforced concrete, prestressed concrete, composite prestressed concrete). The following descriptions are directed toward the clarification of the logical criteria and the calculation methods that produce the moment capacity and the available capacity for LL + IMP for structural steel, composite steel and concrete, reinforced concrete, prestressed concrete and composite prestressed concrete.
The criteria for the selection of, and the computational processes, that make up the analysis processes for the various types of member conditions are listed below. The member analysis conditions for moment analysis are: