ALGERIA EARTHQUAKE DISASTER MITIGATION ASSESSMENT

Project Period:
12 days

Volunteer Requirement:
A bi-lingual team consisting of two seismic/structural

Engineers and a construction manager to undertake the following:
1. to help provide an evaluation of building damages that occurred as a result of the earthquake and,
2. to identify measures to improve the safety of these buildings and to mitigate the impact of future earthquakes.

Location: Algiers, Algeria

Client:
Industry Canada/ Sustainable Cities Initiative, and the Government of Algeria

Project Description:
At 18:44 UTC on 21 May 2003 an earthquake of magnitude 6.8 (Mw) shook Algeria and caused damage in five provinces in the North-Central section of the country. The epicenter was located at 36.89N-3.78E just offshore from the locality of Zemmouri in the province of Boumerdes about 50 km east of the capital city of Algiers see Figure 1&2 . The earthquake was followed by several aftershocks, including two events of magnitude 5.8 (Mw). The northern part of Algeria is located at the margin between the north moving African plate and the Eurasian plate, creating a zone of compression, which manifests itself by a series thrust and normal faults that have been mapped in the area

The areas affected by the May 21 earthquake are located along a shoreline strip of 100 km long and about 6 to 12 km wide. This strip encloses very populated cities, including Algiers and Boumerdes. According to AFP (June 16, 2003), the earthquake resulted in 2,276 deaths and 11,000 injuries (based on the provisional toll released by the interior ministry). According to AFP (May 30, 2003), over 100,000 people have been left homeless after the earthquake and are currently staying in the tents.

Of the roughly 107,000 buildings, about 31,000 buildings were listed under heavy damage or total collapse, and about 49,000 were identified to have no or slight damage See Figure 3 & 4. Approximately 11,000 of the buildings assessed after the earthquake expect to be replaced.

It is noteworthy that Algiers area is located in the seismic zone II (the highest seismic zone in Algeria is zone III). Peak ground acceleration (PGA) value for an earthquake expected in Zone II is 0.15g (the acceleration of gravity) for residential apartment buildings. However, according to the information provided by CGS, the recorded peak accelerations in the Algiers area during the May 21 earthquake were on the order of 0.34g. This indicates that the accelerations predicted by the RPA 99 code for the Algiers area were significantly underestimated. According to the discussions the BWB team had with the Algerian scientists involved in the seismic code development, it is likely that the seismic zone for Algiers is going to be upgraded to zone III (with the corresponding PGA value for residential apartment buildings increased to 0.25g).

Damage Assessment:
The BWB team concluded that main deficiency of the widely used concrete “post and beam” buildings, See Figure 5, that were affected by the May 21, 2003 earthquake in Algeria was related to their inability to resist lateral earthquake forces, as discussed above. Beam-column joints failed at the top of the first storey column level due to their inability to sustain high stresses these joints were subjected to during the earthquake, See Figures 6 and 7. These failures resulted in a loss of stability and collapse of most buildings, and rendered many damaged buildings of this type at risk of collapse in future earthquakes, “Stiffening” element(s) need to be provided to remediate this deficiency and retrofit the damaged buildings for the effects of future earthquakes.

The causes of building failures, as identified and outlined above by the BWB team, were discussed with the CTC engineering staff, and they agreed with these findings. During the meetings, the BWB team members introduced an alternative building technology using a reinforced hollow concrete block system. The CTC Government Engineers indicated that the reinforced concrete block construction system was not being used, and also the concrete hollow blocks were not being manufactured in Algeria.

The BWB team members described the advantages of the system were:
1. it provides the necessary rigidity in the damaged buildings and improves earthquake safety by being more resilient than a poured âin-place solid concrete wall;
2. it is a simple construction technology ;
3. it requires less building materials, including formwork, steel and concrete;
4. it is a faster construction system
5. it provides an improved level quality control of quality control of building materials.

Recommendation - a Demonstration Project:

1. Builders Without Borders proposes that the Canadian Government, through Industry Canada, SCI and CIDA, work with the Algerian Government through the Wilaya d’Alger officials, on a Demonstration Project, to repair a typical five-storey concrete building using an alternative construction technology.
2. The Demonstration Project would introduce an alternative construction technology, namely a hollow reinforced concrete block building construction, a building system commonly used in North America.
3. This technology has a potential of wide application to the construction of new one to five storey buildings in Algeria. Application of this technology would also create opportunities for several new companies in the block manufacturing business.

Figure 1. Earthquakes in Algeria, with the epicenter of the May 21, 2003 earthquake denoted with a yellow star.



Figure 2. Major ground fissures in the epicentral area of the May 21, 2003 earthquake close to the port of Zemmouri-El-Bahri.



Figure 5. Typical reinforced concrete multi-family residential construction (note columns, beams, and floor slabs).



Figure 3. Total collapse of a reinforced concrete building (Derguana, Algiers); the collapsed building was identical to the one standing on the left hand side of the photograph (which is a part of the Demonstration project).



Figure 4. Total collapse of a single-family house in the epicentral area (Zemmouri) caused by the collapse of the first storey columns.



Figure 6. Many reinforced concrete buildings experienced damage at the first storey; cleaning of the site and the preparations for the retrofit work are underway (Derguana area, Algiers).



Figure 7. Typical damage pattern in reinforced concrete construction: damage concentrated at the top of the first storey columns; note buckling of steel reinforcement, absence of transverse reinforcement and crushing of concrete. Hollow brick infill has also failed. Damage to the upper floors is marginal.



Figure 8. BWB/SCI team discussing the retrofit solutions with CTC engineers in Algiers (note the open staircases at the background)



Figure 9. BWB/SCI team standing in front of the building complex chosen for the Demonstration project.