Day 2: Initial Wanderings and Observations
Initial Structural Damage Observations and Social Discoveries
October 29, 2017
Today I woke up at 7 a.m. to the sound of loud Mexican music coming from the plaza outside my window. Not long after, I went down to the hotel lobby to meet up with Dr. Breña and our local host, Dr. Mario Rodriguez from Universidad Nacional Autónoma de México (UNAM). Dr. Rodriguez shared his theories about damage to buildings that experienced both the 1985 and 2017 earthquakes.
We then navigated our way through the blocks of downtown Mexico City towards the concentration of damaged buildings shown in the annotated map (near Av. México and Ámsterdam). The red markers are buildings that have not yet been investigated, yellow markers have already been investigated, and black markers indicate collapses. Today we would focus on the red markers.
Above: map of earthquake investigation sites
Much of the external damage to buildings was horizontal and diagonal cracking to unreinforced masonry infill, clearly visible in the images shown below (top row). Another common damage type was spalling along beams and columns that were subjected to significant stresses during the earthquake shown below (bottom row). Further investigation will be necessary to determine if repairs could be made using epoxy injection of cracks or strengthening of column members via jacketing.
cracking to masonary infill(left) and cracking and spalling of beams/columns(right)
This is about the time that Garrett Hagen joined up with us, and all stopped for a lunch of pollo con mango seasoning. At home, I am a practicing vegan, but I did not want to miss out on experiencing the culture during my travels.
The afternoon allowed me to practice my Spanish, as it turns out many locals like to tell their story and voice their concerns about the buildings they live in to a team of knowledgeable engineers. Some were even kind enough to let us into their homes or apartments to take notes of damage to interior columns and shear walls.
A case I found in particularly interesting was 55 Av. México where one side of the building had hardly any external damage, but the perpendicular side had masonry infill cracking at nearly every floor and plaster was spalling off in large sections. From the interior courtyard we also observed the causes of the irregular soft story suffered by this building: a reentrant corner and a large span without a continuous column to the foundation. This building had been rehabilitated after the 1985 earthquake with epoxy crack injections to the concrete core wall surrounding the stairwell at the center of the building. Last month’s earthquake led to weakening of this wall system resulting in additional lateral and torsional demands on exterior columns. As an outcome, the front center column exhibits shear cracking at the ground level of structure, but we did not observe distress as we traced the column up to the third through fifth floors. It is likely damage is concentrated at the base of the structure due to the combined story forces which result in a significant base shear at the bottom floor.
55 Av. México: Undamaged vs. Damaged Faces of the Building
left: 55 Ave. mexico: concrete core wall surrounding stairwell (darker areas indicate poxy addded after 1985 earthquake)
Right: shear cracking to column at bottom level
During the course of our work today, I witnessed a Día de Los Muertos procession attended by many with painted faces and traditional attire. This event serves as a remembrance of those who have since passed on, including those from the recent earthquake. A park near our hotel also had giant skulls adorning the walkways for this special occasion.
