May 1st was our first full day in Ecuador, after landing in Guayaquil on April 30. Our team has three members: Traveling from our Bogota office there is Juan Caballero, architect and Director of Programs and Partnerships for Latin American, and Walter Cano, structural engineer and Project Engineer for Colombia. From the U.S./headquarters there is Lizzie Blaisdell, structural engineer and Director of Engineering.
In Guayaquil, we saw little evidence of an earthquake. According to the preliminary report on the Instituto Geofisico website (http://www.igepn.edu.ec/) a strong motion sensor near Guayaquil, “AGYE” experienced a maximum ground acceleration of 23.04 cm/s2 (approx. 2%g) while another just east of the area, “AMIL” recorded a maximum acceleration of 51.04 cm/s2 (approx. 5%g). As a point of comparison, the new Norma Ecuatoriana de la Construccion (Ecuadorian Construction Code) considers the seismic zone factor, Z, to be 0.4. For a Type D soil, that would result in a peak ground acceleration of 0.48g for the design spectrum (475 year return period earthquake). So the recorded motions indicate the accelerations were about 5-10% of the design basis earthquake for Guayaquil, fairly low.
We spent the day driving toward Manta. In Guayaquil, the housing was generally taller than once we were out of the city. The residential buildings were typically concrete frame with block infill, or confined masonry in some cases.
As we drove further from the city along highway 482, the housing types became more variant. Instead of columns and beams built from reinforced concrete construction, we also began to see houses that were heavy timber frame or even steel frame, with infill. The infill varied too, from concrete blocks, solid bricks (often turned vertical on their narrow edge), or hollow clay tile.
We only started to see significant signs of earthquake damage as we approached Montecristi, a town just east of Manta. However, once we arrived in Manta, the damage was evident and areas of the city were barricaded for safety.
We saw similar housing types in Manta as we had seen on the drive. Several timber frame with infill houses were heavily damaged. Probably the masonry did not have good connections with the frame and it was also not strong enough to resist the earthquake – causing failure of the masonry and separation from the frame. Sometimes it appeared that the collapsing masonry tore down other parts of the building with it, such as the roof or floor.
Separation between the different parts of the building due to poor connections between elements was a common type of damage observed. The connections were not strong enough to keep the building tied together in the earthquake.
Several residential buildings suffered from soft/weak story failure.
We also saw failure or damaged front walls where they cantilever out over the facade below. The vertical discontinuity this causes can create stress concentrations at the overhang and increase flexibility at the base of the overhanging wall – leading to cracking.
We see very similar types of buildings to these from Manta everywhere around the world where Build Change works. It’s always hard to see communities suffering from these disasters. We hope these vibrant towns will be able to recover from this disaster quickly, while rebuilding safer, more resilient communities.