The Syrian Arab Code for the Design and Implementation of Reinforced Concrete Structures and its earthquakes appendix sets strict standards for construction. However, after the recent earthquake, the damage to buildings licensed under the code raises questions about its effectiveness.
The code and its appendix require specific steps to be followed when constructing an earthquake-resistant building, including criteria on the type of iron reinforcements, the portion of concrete in square metres, and the ratios for concrete mixes, as well as information regarding the design of the structural sequence, i.e. the distribution of the building foundations, retaining walls, and load-bearing shear walls. After completing the design, which indicates that a planned building complies with the standards of the earthquake appendix, it must be submitted to the local administrative unit before obtaining a construction permit.
The Engineers Syndicate and the local administrative unit are subsequently responsible for supervising adherence to the code during the various stages of construction.
When digging begins at the construction site, the builders – usually the contractors – submit soil samples for testing at specialised civil engineering labs affiliated with public universities or government institutions. The records of these test results are documented in an official register that can later be referenced. The foundation design and concrete mixes for the planned building may be modified according to the test results. As the construction process continues, the builder must also present samples of the concrete mix to officially accredited labs to test whether they adhere to the descriptions within the design study. These labs then issue official reports either approving or rejecting the concrete mixes. Like the soil samples, the results are recorded in an official register that can be referenced later.
In short, even considering the cases of negligence and corruption, strict criteria still exist for implementing the code during the design and construction process. Such rigorous standards mean we must examine the code to understand why many licensed buildings collapsed in the earthquake.
First, there is a purely technical issue in the code: the earthquakes appendix uses a cacophony of different scales to measure earthquake intensity, energy, and size, such as the Mercalli intensity scale, the peak ground acceleration (PGA) measured in metre per second squared, the PGA in square centimetres per second squared, and the PGA attributed to the gravitational acceleration scale. PGA measures the ground acceleration during earthquake shaking in a given location.
These scales measure different seismic events using various methods with no direct relationship between them. As such, the earthquake appendix appears to be a mix of scales borrowed from various international construction codes with no clear justification or reason for using them. Remarkably, the appendix leaves out the widely used Richter scale entirely.
Beyond the cacophony of scales, there is an even bigger problem. Part H of the earthquake appendix states that Syria’s most seismically dangerous areas are located in the country’s west, where the PGA measures 300-400 centimetres per second squared during an earthquake. Yet, the appendix requires residential construction designs in these areas to resist a maximum PGA of only 300 centimetres per second squared. It is unclear why the code does not require resistance to a PGA of 400, as expected in these regions.
Because it is difficult to use these complex scales in the design process for earthquake-resistant buildings, engineers hoping to obtain construction permits in western parts of the country design their buildings to resist magnitude-6 quakes on the Richter scale. Theoretically, this is roughly equivalent (albeit with much simplification) to a PGA of 300 centimetres per second squared. In either case, permits are granted for residential buildings in high-density parts of western Syria so long as they can resist magnitude-6 earthquakes, even though the area is at risk of 6.5-magnitude earthquakes and higher.
The code also requires that soil at the excavation level of a building’s foundations be tested but does not require any geological study of the construction site. Such a study would mean examining the geological characteristics beneath the foundation level, which is essential because there may be hollow spaces, aquifers, and sandy, unstable soil in areas close to seismic faults below the construction site. Earthquakes can loosen these underground layers, causing the buildings above them to collapse regardless of how earthquake-resistant they are according to the Syrian Arab Code standards.
The code also fails to account for construction time. Construction in Syria usually takes a long time due to funding issues, complicated bureaucracy, and the need for security approvals. Construction can span decades for public sector projects, social housing and cooperative housing. In such cases, the concrete structure of the built unit remains exposed and unprotected from the weather for long periods. High humidity in coastal areas may erode cement surfaces and cause iron to rust. When construction does resume, no new inspection is done on the concrete structure, leaving the completed buildings vulnerable to collapse in an earthquake.