The report, by University of Colorado (CU) Department of Civil, Environmental, and Architectural Engineering researchers Abbie Liel and Kathryn Lynch, is the result of a field study following the April 6 L’Aquila, Italy, earthquake. The authors collected information on more than 450 reinforced concrete structures. By examining that information along with census and other social data, they found 38 percent ofL’Aquila residents living in reinforced concrete structures experienced moderate or heavy damage to their homes. The damage led to significant disruption of the community and social fabric, including the closure of government offices, churches, restaurants, and schools.

The fieldwork, funded by the Natural Hazards Center Quick Response Grant Program, will be the basis for a National Science Foundation RAPID research project on progress and priorities in L’Aquila’s recovery and reconstruction. The original research team will work with CU Engineering Professor Ross Corotis, CU Institute of Behavioral Science Research Associate Jeannette Sutton, and University of Chieti-Pescara Professors Guido Camata and Enrico Spacone to study decision making and recovery progress over the next nine months.

The Italian government’s new approach to disaster recovery—and probable resulting changes in decision making and organizations—makes the study particularly compelling. Interviews with reconstruction and building industry leaders, government officials, and community leaders are expected to wrap up in Spring 2010.

Italy’s AeDES assessment process is considerably more detailed and nuanced compared to the CalEMA SAP-ATC 20 process. Italy uses engineers to collect additional information about the nature of the building systems, the damage and its extent to help compile aggregate loss estimates on groups of the buildings that have been assessed. Italy does not post placards since laws prohibit that activity. Italy also does not provide immunity from liability for safety and damage assessments. In contrast, SAP-ATC 20 is limited to safety assessments and is not intended to estimate aggregate losses or the extent and variation of losses within portions of buildings. SAP ATC 20 is also largely conducted by non-engineer inspectors averaging 26 building assessments per team-day (20 to 25 minutes per building) supplemented by teams of engineers for follow-up evaluations or for the larger, engineered buildings. Italy’s assessments are averaging 20 to 30 minutes per building for the entire event and 7 assessments per team-day in the Red Zone due to extenuating circumstances. A chart comparing the different assessment processes is under development and will provide basic information about Japan’s and Greece’s practices as well as a new form under development by STEP.

Fred’s images are captioned and geotagged at:

http://picasaweb.google.com/FredTurnerSE/LAquilaItalyFredTurnerSImages200906?authkey=Gv1sRgCOLQrOLCrvrT2AE#

A detailed map of the Red Zone:

map-red-zone-laquila-fmt-6-4-09

Onna

Monticchio and Onna are about a mile apart, and have a similar building stock of stone masonry buildings in the historical centers. It is interesting to see how different these two villages performed, given the structural similarity.

Onna suffered badly in the earthquake. Almost all buildings in the historical center show signs of damage, and many collapsed. About 40 lives were lost on a population of 350. Many of the damaged buildings and the building remains pose collapse hazards. At the time of our visit buildings were being shored or demolished to mitigate falling hazards and provide the citizens with a safe opportunity to visit their houses to gather any belongings that can be salvaged.

Monticchio on the other hand suffered little from the earthquake. We walked through the historical center, and saw mainly minor cracking in walls and failure of some parapet walls. We visited a house that was retrofitted by confining the walls with a welded wire mesh on both sides, connected with through bars. The only sign of damage that this building showed was a crack in the wall at the first floor were new material and historic fabric abutted. Down from the village into the valley we did find a few concrete structures with more sever damage, including failure of infill walls and buckling of bars in the hinge zone of the concrete columns.

Monticchio

The current thought is that the site conditions have driven the difference in performance. Monticchio is built on a hill side on rock, whereas Onna is built in the plane on softer soil layers.

During our (limited) site visit we observed very little structural damage. Unfortunately the structural damage that did occur is located in crital areas. There is severe column damage in the farmacy area, which is considered to pose a collapse hazard. Operating theaters are located at the floor above the farmacy, and as a result could not be used. Another column that is shored at this time is right along the A&E access path, and posed a serious risk to people seeking medical attention after the earthquake.

We observed mainly non-structural damage at the hospitalm (say 90-95% of all damage was non-structural ). Failure of brick veneer cladding was widespread on the hospital campus. Many internal clay masonry partitions were also damaged. There are many signs of unanchored equipment that moved in the earthquake, but not to an extent where it damaged the equipment.

The hospital was evacuated after the earthquake, and remains closed. One of our principal concerns before allowing access to relatively undamaged buildings of the hospital would be the falling hazard that damaged brick veneer poses to access routes and travel paths through the hospital campus. They would need to be mitigated.

Talking to the people in the area around l’Aquila it is pretty clear what kind of performance is expected from a hospital after an earthquake: it should be operational.

Among this construction class the modern RC frame buildings (i.e., those designed after 2003 when the last building code was issued) performed much better than those of the 60s to 80s vintage. The modern RC frame buildings usually suffered no exterior damage or minor/moderate damage to the clay partitions both internal and external (see Fig 1 for a typical example). We only found one modern building on the verge of collapse whose many columns were completely severed in shear possibly due to a faulty design that did not properly considered torsional effects (i.e., buildings rotation along the vertical axis during the ground shaking due to stiffness and plan irregularities) (see figure 2 ).  This building is unlikely to be recovered and may be demolished.

In the nearby town of Pettino, the EERI survey team found several instances of soft story effects. Two out of four almost identical buildings collapsed in this same failure mode and two survived. In the particular case shown (in figure 3) a three story structure collapsed when the columns of the first story,used for parking space, failed. A survivor of the earthquakes told us that the mainshock of April 6 generated a significant damage that lowered the first floor by about a foot but the first story collapsed completely in an aftershock.

The first story column-beam connections displayed insufficient stirrup reinforcement (large spacing and small diameter) and short anchorage lengths around the beam longitudinal rebar in the column. The second collapsed building in this cluster of four failed instead during the mainshock. The other two remained standing although one showed significant separation of the infill walls in the first story, indicating an incipient similar failure mechanism that was not fully developed while the fourth one experience minor exterior damage (figure 4).

The green shed in figure 5. houses the strong ground motion station at the “Moro” location that registered a peak ground acceleration of over 1g, saturating shortly thereafter. Investigations are still taking place to make sure that no malfunctioning of the instrument occurred during the shaking. The station is surrounded by several identical six-story reinforced concrete structures (figure 6) built in the late eighties to early 90s that showed no apparent structural damage but only moderate cracking to the infill walls. Note the green 3-story RC frames recently remodeled (figure 5) across the street from the station that was completely unscathed. This case study is sure to stem thorough investigations in the engineering community to understand how these buildings could survive relatively untouched to such a large ground motion

Figure 1

Facades of unreinforced masonry structures show cracks varying in severity, from loss of plaster to separation of the walls from the structure. In this last case, the structural integrity of the wall, the load-bearing system, is compromised. Some of the structures in downtown L’Aquila that show this type of failure in several of their facades might have to undergo demolition. In isolated cases, the collapse of masonry structures in the old center of L’Aquila was complete. Partial structural collapses of walls or cornices were more frequent.

Figure 2

Masonry structures that displayed cross-ties (catena in Italian), showed a much better resistance provided that the lateral walls were properly constructed.

From EERI/PEER Team: Damage to Concrete Structures

Figure 3

Figure 4

In older building code specifications, column-beam connections were allowed to be designed with smooth rebars that provide insufficient bonding with the concrete such as shown in figure 4. Failed connections also displayed widely-spaced, small-diameter stirrups, that cannot prevent the buckling of longitudinal rebar in columns. This has been the cause of most of the collapses that we have seen in the field, such as in figure 3.

Figure 5

This figure shows a spectacular pancake of the third onto the second story due to the failure of all the beam-column connections (as described above).

Figure 6

This is a textbook example of pounding effect between two neighboring structures. The roof of the 2-story building hits the column of the adjacent 4-story structure causing the complete failure of all the columns at that level. Note that the third and the fourth story essentially show no damage.

The website is located at:  http://virtualdisasterviewer.com/vdv/index.php?selectedEventId=2

We have obtained the ground motion records from the 4 instruments in the area. Today we located one of the records.  Tomorrow, we intend to locate the remaining three instruments and to observe the earthquake damage at the San Salvatore Hospital. (Photos and captions by Ricardo Hernandez)

Provided by Professor E. Lekkas, University of Athens.