Developing a Seismic Damage Evaluation Model for Tehran’s Buildings in a GIS Environment

In the context of a research project, which is conducted by K.N.Toosi University of Technology and Tehran University, a general model is developing to estimate destruction levels of buildings in Tehran, in the case of occurrence of earthquake. This model is being developed in GIS environment. This paper outlines the basic concepts which are being used to develop the model as well as the results of the research till now.

Attenuation Relationships
After occurrence of an earthquake, the center and the magnitude of the earthquake are two initial data that are available. The magnitude of earthquake in any location is different from the magnitude at the center. It differs and generally decreases when the distance between a certain point and the earthquake center increases. Different factors such as soil type and distance from the center have effect on the value of magnitude on a certain point. To obtain this effect and the magnitude in any place, some formulas called attenuation relationships are used. Common parameters that can be calculated by these formulas are PGA (Peak Ground Acceleration), PGV (Peak Ground Velocity) and PGD (Peak Ground Displacement). These formulas are developed based on empirical or theoretical studies. In this research Zare's attenuation relationship (Zare, 1999) that is based on empirical method is used.

Fragility Curves
Fragility curves describe the destruction excess probability (from a predefined percentage) with respect to the earthquake physical parameters (Jalalian, 2006). To develop fragility curve for an area, buildings are classified to different groups according to their structural system, the design code and number of floors. A fragility curve is offered for each group. For example, in U.S emergency management software (Hazus99 Technical Manual, 1999), buildings have been classified into 36 groups according to structural system and number of floors. In this category, number of floors have been classified into Low-Rise(1-3), Mid-Rise(4-7) and High-Rise(8+). With respect to the design code, the 36 groups are presented in four code groups: Pre-code, Low-code, Moderate-code, and High-code.

There are four methods to develop a fragility curve namely empirical, judgmental, and analytical and hybrid. In figures 1, 2, 3 some fragility curves for Masonry buildings are illustrated (Jalalian, 2006).

Figure 1 – Fragility curve for 0-30% Destruction (Jalalian, 2006)

Figure 2 – Fragility curve for 30-60% Destruction (Jalalian, 2006)

Figure 3 – Fragility curve for 60-100% Destruction (Jalalian, 2006)

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