Construction Retrofit Details - Un-Reinforced Masonry Walls

On January 12, 2010, a shallow earthquake 25 kms from Port Au-Prince in Haiti devastated the region and killed over 270,000 people. On early October 2016, Cat 4 Hurricane Matthew went over the same area, with catastrophic flooding and storm surge resulting in 580 people dead and 35,000 homeless.

Two earthquakes struck Mexico in September 2017, an 8.1 on the 7th on the coast of Oaxaca, and a 7.1 on the 19th near active volcano Popocatepetl right below the city of Puebla, 100 kms from Mexico City. The first event did substantial damage over a widespread area in three states (Oaxaca, Chiapas, and Tabasco); the second event was not expected and did substantial harm to existing buildings in the region, which unless repaired are prone to collapse.

A number of typical details are provided (no software tools) to retrofit Unreinforced Masonry (URM) walls of existing 1-2 story Low Rise buildings in seismic regions, with the intention of tying brittle walls (brick or masonry, damaged or not) together and providing enough system ductility to survive strong ground motion without collapse.

Description of Contents:

Retrofit Details are provided for strengthening URM walls of existing single story buildings in seismic regions:

These details show the completed Retrofit of URM walls (bricks, hollow masonry blocks, etc) supporting wood or other light roofs. URM walls are secured to new thin Reinforced Concrete (RC) Walls by means of dowels (securing falling hazard), and the wall reinforcement is interconnected at room corners and connected to floors as to form an interior thin walled RC membrane resisting all EQ loads while supporting the roof. The concrete used is Shotcrete, sprayed with a gun instead of poured with a hose, so concrete forms are not needed (one-sided forms, using URM walls tied with epoxy dowels).

These details can be used by contractor with minimal inspections by an Engineer or Building Department for a single story building. For two story buildings, an Engineer can use these details and add more to connect walls across a floor level and tie the entire building together.

For the construction of new low cost improved adobe wall residential buildings, please refer to EERI (Earthquake Engineering Research Institute) ”Lessons Learned Over Time Volume V: Adobe Housing Reconstruction after the 2001 El Salvador Earthquakes”, with text in both Spanish and English in a single document, and available for $15 per copy at the EERI website (https://www.eeri.org/products-page/research-needs-lessons-learned/lessons-learned-over-time-volume-v-adobe-housing-reconstruction-after-the-2001-el-salvador-earthquakes-2/).