Some more reflections from Kevin on his recent Haiti trip:
This trip has been particularly difficult in terms of logistics. I was able to schedule appointments, cars, drivers and translators up to a half a day in advance of our team but not usually beyond that. But we were amazed that we had so little down time due to waiting or needing another project to visit. God worked it out very well. Even though efficiency and effectiveness are not a measure of success in God’s kingdom, from an engineer’s perspective, it was a very efficient and effective trip. We were able to bring relief to a lot of people who feared they would have to tear down and build again. We were able to provide repairs to them that would strengthen their house to better than it was before the earthquake. And they could grasp that the repairs were achievable as long as they applied attention to detail and were diligent in hiring competent crews that did not skimp on materials.
On a technical note:
Our observations were that buildings by and large failed because of inattention to detail during construction.
The worst failures were in buildings that were very top heavy. Thick heavy concrete slabs on each floor and roof with inherently weak columns and no effective shear walls resulted in buildings swaying in the earthquake resulting in column and wall failures on the first floor. Most second floors were unscathed with not even cracks in the walls. The first floor columns would fail and the building would fall maybe ½” or 10 feet, and still the second floor would not need even cosmetic repairs. However you can’t lift a second story (not by much anyway with wooden shoring), so the building easily becomes a writeoff.
The buildings we were able to save were those where even though there were structural cracks in columns or walls the second floor hadn’t actually subsided at all. These were often ones with light roofs (non-concrete), or single storey.
We didn’t find a single foundation failure (cracks or tilting).
Bad construction details that we found included:
– one building where the rebar in a beam was only overlapping 4”. We assumed this to be a widespread problem.
– Most columns did not have sufficient stirrups. However, one building where the high number of stirrups in the column prevented the broken concrete from crumbling out of the column, resulting in the second floor not subsiding and allowing us to rebuild the column and save the building.
– Concrete blocks that crumbled with small hits of a hammer. Better blocks are widely available but cost twice as much. It is common to try to save money by using cheaper blocks. Therefore the block walls easily crumbled
– Insufficient cement in the concrete – very common method to save money in concrete
– Sand in the concrete was limestone based, and so it was very weak and silty
– Too much water in the concrete mix and very little compaction / vibration is common
– It is uncommon to put any reinforcement in block walls
This was a tragic earthquake, but the death toll and carnage of buildings could have been significantly reduced with more inspections, quality control and attention to detail. It’s not as if Haitians don’t know how to build well, it’s that they are constantly looking for shortcuts and cost savings.
We’ll hope and pray that as Haiti rebuilds, these lessons learned will be reflected in the new construction.