Computerized Approaches Based on Classical Beam Analysis Methods

4.4 Computerized Approaches Based on Classical Beam Analysis Methods

One way to address the complexity of live load modeling in a girderline analysis is to computerize the analysis calculations. There are numerous ways to incorporate computer technology into a girderline analysis. Usually, the extent of the design process covered in the computer application determines the effort required to create and use that tool. An application may be as simple as a spreadsheet that tabulates moments and shears for the beam, or it may be as complicated as a custom program which covers the entire design process, from generation of geometric parameters and cross section properties, quantification of framing considerations, calculations of shears, moments, stresses, and deflections, and comparisons to specification- derived capacities and other code provisions.

Archived

Spreadsheets offer flexibility and control in girderline analyses. The limitations to the complexity and extent of the spreadsheet are based primarily on the time and money available

and the skills of the designer in programming the spreadsheet.

However, care should be exercised in using spreadsheets. As with any computer application, a spreadsheet can become a “black box” approach that is difficult to document, check, and interpret. Moreover, quality control and validation may be limited in many cases. For example, spreadsheets are often not checked with a full range of testing suites like most commercial However, care should be exercised in using spreadsheets. As with any computer application, a spreadsheet can become a “black box” approach that is difficult to document, check, and interpret. Moreover, quality control and validation may be limited in many cases. For example, spreadsheets are often not checked with a full range of testing suites like most commercial

In addition, the multiple paths and decision points in the current AASHTO steel girder design provisions may prove to be difficult to program efficiently in a spreadsheet. Spreadsheets are efficient for calculating a large number of values using simple formulas, but are much less efficient when used for calculating values that may result from complex formulas or processes often dependent on the value of one or more other variables with several conditional execution paths.

A more efficient approach to addressing the complexities in steel girder design may be found in applications that are developed using a formal programming language where spreadsheets constraints are removed. However both significant computer science and engineering experience are required to address the complexities of the current steel girder design provisions.

Applications for girderline analysis are most often commercially licensed or otherwise developed by specialized consultants. Several steel girderline design applications are available, both from commercial software companies and from various bridge owner-agencies (either for free or at a nominal cost).

In all cases, any computerized approach, whether a spreadsheet or a program, whether commercially-purchased or “home-grown,” should always be verified and spot-checked by independent calculations performed either by hand or by an independent computer tool. Most computer applications are complex tools and even minor programming errors can drastically affect the results of engineering computations. Details about validation of applications can be found in references (21, 22).