Explained: Earthquake-resistant Building Design Basics

In the Syrian Arab Code for the Design and Implementation of Reinforced Concrete Structures, there is an appendix on the basic principles for earthquake-resistant building design. It specifies the construction methods to prevent total or partial collapse during earthquakes. In theory, if the code is followed during the design and implementation process, a building will remain intact even if an earthquake’s magnitude on the Richter scale reaches the upper expected limit for that area. 

The code lays out four steps that must be followed to construct earthquake-resistant buildings: 

1. A building site’s seismicity (or maximum expected earthquake magnitude) must first be determined. The most significant factors in a site’s seismicity are its proximity to active seismic sources, the seismic history and the frequency of earthquakes in the past 50 years. To help determine seismicity, the earthquake appendix includes a seismic map of Syria created in cooperation with the General Establishment for Geology and Mineral Resources and the Atomic Energy Commission of Syria.The map divides Syria into seismic regions according to the magnitude of expected earthquakes, which are weakest in the east and more severe as the map moves further west. Zone 0 is not considered at risk of significant earthquakes and has a maximum expected magnitude of less than 4.8 on the Richter scale. Zone 1, with a maximum expected magnitude of 5.4, is not at risk of deadly quakes. Zone 2 is at risk of moderate earthquakes of up to 6.1 on the Richter scale. Zone 3 can expect high-intensity earthquakes up to 6.5 on the Richter scale. Finally, Zone 4 is at the highest risk. It can expects devastating earthquakes of over 6.5 degrees of magnitude.

   The seismic map of Syria. Source: The earthquakes appendix to the Syrian Arab Code for the Design and Implementation of Reinforced Concrete Structures.

2. The geological features and soil type of the building site must undergo study. The study includes the soil mechanics that determine a site’s cohesion and hardness (if it is rocky, clay-like or sandy). Each type has the potential to be compressed or fragmented and collapsed. The depth and dimensions for digging a building’s foundation are determined based on these soil types. This study is required in building design and obtaining a permit to begin construction work.
3. The design stage of the building, according to the shape requirements, determines the structural sequence of construction, meaning the distribution of the building foundations, retaining walls, and the building height. For example, buildings in areas subject to over-6.1-magnitude earthquakes on the Richter scale may not be taller than 20 metres if using traditional construction methods or 49 metres for those with shear walls. Buildings with steel frames can be up to 73 metres tall.
4. The design for the building’s earthquake resistance undergoes study using static methods (the impact of an earthquake on the base of a building only) and dynamic methods (the impact on the entire structure). For example, if the building is less than 73 metres tall, it must be designed according to static study methods. Those taller than 73 metres must also undergo dynamic study methods. 

Only buildings designed according to the above four steps are considered to comply with the earthquake-resistance appendix standards. Engineers and building contractors must apply the building code in their design studies when applying for a construction permit. The Engineers’ Syndicate and local administrative units oversee adherence to the code during the different stages of construction.