Interactive modeling system for bridges

The modeling system described in this paper was developed in conjunction with the computer program called STACRB that was developed in the CURT research project at the University of Pennsylvania. In essence, the STACRB program utilized the method of finite elements to analyze the static behavior of horizontally curved and straight aligned bridge structures.

The modeling system communicates with the user through a problem oriented language. The commands in this language allow the user to define the parameters that characterize the structure, modify an already existing structure, or inquire about the results of analysis already completed for a structure. The commands are entered in free format and are executed interpretively, thus allowing the user to communicate with the system in a conversational mode. The user may also enter the command on punched cards and execute the routine as a non-conversational batch job. The modeling system can be used to either control the analysis or operate independently from it. In the former case, the modeling system synthesizes the structure, then calls on the STACRB program to analyze it. When the analysis is completed, the control is returned to the modeling system to interpret the results of the analysis according to the commands supplied by the user. In the latter case, the results from the modeling procedure alone are punched onto cards which may subsequently be inputed to the analysis routine.

The modeling system also includes facilities for graphical displays of components of the designed structure such as structure geometry and element discretization or results of analysis such as nodal deflections, reactions and element stresses. The displays may be produced either on the line printer for conversational purposes or on a CALCOMP plotter.

The overall increased efficiency introduced by the modeling system in the analysis/design cycle of a bridge structure is quite significant.