In Egypt, the first official seismic design code was established in 1989. Prior to the issuance of this seismic code most of buildings were designed without any considerations for seismic design requirements. The occurrence of the 12 October 1992 Cairo earthquake has surprised the engineering community, as they have long believed that Egypt is not in seismically active area. This has made the problem of seismic capacity evaluation of existing buildings in Egypt of great importance and interest.

Difficulties in the safety evaluation of an existing building result from the complexities of the structural system and uncertainties of future earthquake activities. The exact behaviour of a given structure is still difficult to predict because of the many uncertainties involved at all stages of structural design, construction and operation. Therefore, it is not yet possible to apply a general mathematical model for accurate prediction of structural response under expected earthquakes.

The current procedures of assessment and evaluation of existing buildings are highly dependent on the experience, intuition and judgment of recognized experts. Moreover, the choice between several available evaluation methods requires expert opinion and the final result must be properly interpreted according to engineering expertise and judgment. In addition, most available methods in damage assessment are not sufficient alone because the information can be inexact and/or incomplete. Therefore, structural assessment for a particular building can be characterized as a sequence of decision-making problems. Many researchers have focused on developing a rational and systematic process to assist in the assessment of structural safety. Knowledge- based expert systems can be useful tools in such applications.

In the present paper a knowledge-based expert system EQEVAL (EarthQuake EVALuation system) is developed for the qualitative evaluation of seismic behaviour of existing reinforced concrete buildings. The qualitative approach performs the seismic evaluation of buildings with simple rational and instructive procedures.

The main source of knowledge for the expert system EQEVAL is based on the Japanese standard for evaluation of seismic capacity of existing reinforced concrete building structures. The basis of selection of this standard is that, it considered the most important factors affecting the seismic performance of buildings, as well as, reliable weights for these factors are assigned. Some of equations used to calculate the ultimate strength of the vertical elements were adapted to reflect the requirements of the Egyptian code of practice for reinforced concrete structures. The seismic behaviour of a reinforced concrete building is judged by comparing an estimated performance index (supply) for the considered building with a required seismic performance index (demand). The investigated structure is said to be safe if the calculated seismic index is larger than the required judgment index. Otherwise, the structure is assumed to be uncertain for the seismic performance against an assumed earthquake ground motion.

The knowledge representation used to organize and control information in the developed expert system was the attributes, rules and methods with Object- Oriented Programming technique. The forward chaining inference engine, which suits damage assessment problems, was used in developing the system. A graphical representation was employed in the developed expert system whenever possible. This representation provides an accurate and easy way to describe the building configuration and its structural system. User-friendly interface was employed to simplify the system-user interaction through its menus and help messages.

To calibrate the developed methodology and the proposed expert system EQEVAL, two buildings located at greater Cairo area, were investigated. These buildings experienced the October 12, 1992 Cairo earthquake. A brief description of the evaluated buildings, their structural damage levels and the results of the qualitative evaluation were introduced.

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