Nabil A.B. Yehia

Distortional strain energy density criterion: the Y-Criterion

Abstract The complete formulation of the distortional strain energy density criterion is presented. The criterion minimizes the distortional strain energy density component to predict the propagation direction. It further postulates that propagation will commence when this minimum reaches the material critical distortional strain energy density determined through the implementation of the proper yield condition. The criterion defines the crack tip core region as the distance determined in pure mode I; this distance is considered an intrinsic material property. LEFM concepts are used through the singular elastic stress field at a crack tip. Predictions of the presented fracture criterion regarding crack propagation angle and fracture load are compared to the predictions of other criteria as well as the available experimental data.

A knowledge-based system for the design of reinforced concrete halls

Abstract A knowledge-based system for the design of reinforced concrete halls is presented for use on microcomputers. The system consists of two subsystems, an intelligent subsystem for proposing the layout of the structural system, and an algorithmic subsystem for both analysis and structural design of the components of the structural system. The intelligent subsystem is developed in PROLOG while the analysis and design subsystem is developed in FORTRAN. The intelligent subsystem tried to make use of available aspects of Artificial Intelligence. It takes a step towards the development of knowledge-based systems in structural engineering that learn from the previous experience the system has gone through. It also employs a general technique of generalization/specialization to understand the nature of the problem(s) not known to the system. The analysis and design subsystem contains the required algorithms to generate, preliminary proportion, analyse and design the structural system proposed by the intelligent subsystem. An example is given to show the application of each module in the system until the final product is obtained.

A knowledge-based approach for the design of spread footings

Abstract A knowledge-based system for the design of the general layout of reinforced concrete spread footings is presented. A database, sorting previous design cases, is used to assist the user in obtaining different solutions for each problem. Plotting capability is also incorporated to show all the reinforcement details which could be obtained from a design office. The analysis of single and double footing is carried out using the conventional methods whereas the mat foundation is treated as a plate on elastic foundations and is analyzed by the bending theory of plates using the finite element method.

Approaches to AI methodology in reinforced concrete structures: a case study

A system developed earlier for reinforced concrete halls layout is studied and justified from different aspects. Also, updates of both capabilities and limitations, which were recently incorporated in the system, are emphasized. Some of the original aspects of the system were reviewed and modified, to overcome some of the drawbacks in the earlier presentation. The systems organization remains almost the same. Some suggestions for further improvements to the system are presented as well. Finally the function of the system is illustrated by a sample run of the system.