Performance of Steel, Concrete and Masonry Structures in recent earthquakes of Armenia and Iran Design and Construction Deficiencies

Major earthquakes have occurred during the past two years in the Northern parts of Iran, Armenia, Pakistan and Turkey, killing more than ۷۵,۰۰۰, causing billions of dollars of damage and destruction, and leaving more than half a million people homeless. These earthquakes are the result of the tectonic movements of the Arabian plate moving with a rate of one inch per year, North, towards the Eurasian plate. The collision zone of the plates occur on a line stretching form Northern parts of Afghanistan passing through Pakistan, Iran, Armenia and Turkey (Ref.l). The Armenian earthquake occurred on December ۷, ۱۹۸۸ with a magnitude of ۶.۹ and an aftershock of ۵.۸ on the Richter scale. The Iranian "Manjil" earthquake occurred on June ۲۱, ۱۹۹۰, with a magnitude of ۷.۳ and an aftershock of ۵.۷ on the Richter scale. The epicenter of the Armenian earthquake was located near the city of Spitak, a city located at about ۸۰ Kilometers North of Yerevan, the capital of Armenia (Ref.۲). A forty Kilometer long fault, which originally was thought to be eight Kilometers, was created at the town of spitak extending North West towards the city of Leninakan causing vertical and horizontal movement of ۷۰" and ۲۰" at the fault. Due to shallow focal depth of the earthquake, the energy released affected a small radius. The earthquake caused drastic damage and destruction to three major cities of Spitak, Leninakan, and Kirovakan, and a smaller city Akhorian. The town of Spitak was levelled with the ground and only about ۲۵% of buildings survived in Leninakan. In Spitak most of the buildings were built with hollow core concrete slabs, resting on masonry walls. These buildings were four to five stories high and suffered the most damage due to lack of horizontal or vertical ties. In Kirovakan the subsoil conditions provided minor amplification of the earthquake forces resulting in less damage to buildings even though they were closer to the epicenter than Leninakan. In Leninakan, which is located at a flat sedimentary alluvial and volcanic Tuff basin, amplification occurred due to poor soil conditions resulting in failure of most of the buildings. These areas are not suitable for constructing earthquake resistant structures designed for conventional forces and construction systems. Sedimentary subsoil conditions caused similar destructions in down town Mexico City during earthquake of ۱۹۸۵ (Ref.۳). Due to the extreme shortage of housing in the Soviet Union, programs were developed in the past two decades to construct high rise buildings in various densely populated areas within a short period of time. Prefabricated concrete building