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Seismic Evaluation and Retrofit of Haitian Masonry Construction (Part 2)
Days 2, 3 & 4 – Wednesday June 15th – Friday June 17th Build Change employs a number of local Engineers to work on the design of both new buildings and retrofit projects. The retrofit projects are potentially more complex than new design, therefore a group of 8 of the top performing engineers were selected to learn the retrofit procedure. I spent Thursday morning explaining the retrofit procedure, with the help of Remixon, the translator. I would speak to the group, pause, and he would speak to the group in Creole. It was difficult to tell whether the group was really understanding the material, or just saying they understand. That’s what tests are for!The classroom of Build Change EngineersThe evaluation and retrofit procedure starts with a site visit and a checklist evaluation to identify major deficiencies. One major deficiency is a lack of usable shear wall length in unreinforced masonry buildings. The method has the engineer quantify the actual shear wall length, then calculate the required shear wall length based on the seismicity, the number of stories, building type, the block strength, and the quality of construction. If the actual shear wall length is less than the required wall length, then the engineer must design a retrofit solution using the catalog of retrofit details and recheck the structure. The retrofit can increase wall area by adding new walls, plaster overlay, or concrete overlay. It also can reduce the demand increasing the quality, providing more ductility to the system, or simply reducing the mass by removing the upper story. The procedure is simple to implement, but still requires engineering judgment to execute correctly. Class is in session.We went out to Bristout Boba in the afternoon under a light rain to apply the procedure to the example buildings. (I can hardly imagine what this area is like under a heavy rain. The paths between the houses must become rivers that wash the trash down to the tent camps lower on the hill) The engineers seemed to have picked up on the procedure. They measured the building, defined the usable walls, identified the building type, and completed the evaluation checklist. They calculated the percentage of wall area and, with some coaching, were able to calculate the required wall area. Engineers at the example buildingThe sample building planMeanwhile, construction progress was being made at the pilot project house. The team of builders applied the initial coat of concrete to the retaining wall, and demolished the remainder of the damaged masonry wall. The engineer in charge said that the owner wanted to remove an interior wall in the building, which provides support to the exterior walls. I told him they can’t do it because it was being supported (and providing support to) the adjacent wall. I foresee a challenge with homeowners pressuring the engineers to make “remodel” changes that are not part of the seismic retrofit and not beneficial to the building. The local engineers need to be confident in their evaluations and not condone making changes to weaken the building. I later found out that the owner had dug his own hole for a new column foundation as his own solution for supporting the roof in the absence of the wall he wanted removed. Maybe he conspired with the owner of the adjacent Miyamoto house, who demolished walls that were not part of the retrofit scope with the expectation that Miyamoto would replace them with new ones.Matthew and engineers back at the Pilot ProjectA neighbor lending a handOne of three kids who live at the Pilot Project, soon to have a safer house.Thursday night I had dinner with the Build Change interns from Cal Poly, Ben and Anna, as well as with James Mwangi. James is a Cal Poly professor who has been working for an aid organization in Haiti for a year. We knew each other prior to Haiti from working on the Cal Poly scholarship program. The restaurant was called La Reserva, located in a lush tropical location on a hillside in/near Petion-Ville. James hosted Ben and Anna when they went to Haiti earlier this year on a spring break trip. His understanding of Haitian culture and the challenges facing the country were insightful. The process of rebuilding is more of a political and cultural challenge than an engineering challenge. He shared some of the history of Haiti which indicated that Haiti has grown accustomed to inefficiency. But he genuinely loved the year he spent there. James also spoke highly about his recent road trip through the Dominican Republic. Sounds like another place I’d like to visit.Ben, Anna, James, and Gordy at dinnerI’ve included a few pictures of the apartment that Build Change rents for their guests. They are serious about the safety and comfort of their guests. Every morning one of the drivers employed by Build Change picks us up at the apartment and takes us to the office. Every excursion from the office is with a driver. I would not want to be behind the wheel in Port-au-Prince!The apartment from the outsideThe apartment from the insideThe view from the truckOn Friday morning we wrapped up the training with the Haitian engineers, since we ran out of time the day before. They completed the checklists and did their own calculated of required wall area. It turned out that both buildings we evaluated did not need significant retrofit, although we went through a hypothetical retrofit if one of the buildings were two stories. We had the engineers presented their buildings to the group and talk about the process we used for the evaluation. Seeing the Haitian Engineers present the retrofit procedure was very satisfying. It is important that the Haitian engineers are confident communicators when speaking with the building owners. Engineers working back in the classroomOverall the opportunity to see the projects and the working conditions first hand was invaluable. When concrete ingredients are trekked to a jobsite in 5 gallon buckets, it makes you think twice about how much concrete is really necessary. The trick to the process is maximizing the benefit to the owner for every dollar they spend. The goal is not a code compliant building by US standards, but a building that is not likely to collapse in another major earthquake. Using locally available materials, engineers can assist the homeowners to build better buildings that are culturally appropriate.
Filed Under: Community, Degenkolb, Earthquake, Engineering
Posted by noblestudios on June 29, 2011 2:26 PM
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