Neighborhood Sector 3A
Ciudad Caribia, Venezuela Independent Research Study by AEOP Sector: Residential Seismic Assessment (ASCE 41) Project year: 2016 Publication at World Congress of Earthquake Engineering, Japan, 2020 Otero, A. and Molina Hutt, C. Seismic Evaluation of an Existing Shear Wall Building Representative of Housing Developments in Venezuela,17th World Conference on Earthquake Engineering, September 2020. |
Technological and experimental advances and data obtained through seismic events that have occurred in recent years have incorporated more sophisticated analysis methodologies that model the response of components that enter the inelastic range and are capable of capturing their cyclic degradation. , which has motivated the increase in the use of non-linear dynamic analysis procedures in engineering offices, to optimize designs, evaluate existing buildings and carry out seismic rehabilitation projects.
The present study is part of the first phase of the beginning of a seismic evaluation program of buildings built as a housing solution, motivated by the large number of buildings of social interest built in Venezuela in recent years.
The present study is part of the first phase of the beginning of a seismic evaluation program of buildings built as a housing solution, motivated by the large number of buildings of social interest built in Venezuela in recent years.
In Venezuela there is a considerable housing deficit and in recent years hundreds of buildings of social interest have been built. Most of the housing solutions developed are located in cities with a high level of seismic threat. Originally, the scope of the project was to carry out the structural design of four typical buildings of 5, 6 and 9 floors, constituting a total of 18 buildings (90 housing units). The complex is located in a mountainous area 10 km from Caracas, in a housing development called Ciudad Caribia.
The construction is specified with the Tunnel and Forsa type construction systems, in which the structure is made up of walls to resist gravitational and lateral loads. The structural configuration presented in the architectural project contains walls of 12 cm and 15 cm thickness on which 12 cm slabs are supported.
Among the factors detected that increase the seismic vulnerability of the buildings considered, it is worth highlighting:
Wall thicknesses below the minimum recommended to develop ductile behavior.
High inelastic torsional risk.
Irregular plans classified in the standards as “Flexible Diaphragm” due to internal openings and recesses.
Lack of seismic events in the country (Venezuela) that show evidence of the behavior of this type of construction (Forsa, Túnel) in the face of severe seismic movements.
Changes in rigidity between the ground floor and first level (Soft Mezzanine) due to openings in some walls on the first level.
The densities (total wall area / floor area) are below 4% as recommended in some studies.
Wall thicknesses below the minimum recommended to develop ductile behavior.
High inelastic torsional risk.
Irregular plans classified in the standards as “Flexible Diaphragm” due to internal openings and recesses.
Lack of seismic events in the country (Venezuela) that show evidence of the behavior of this type of construction (Forsa, Túnel) in the face of severe seismic movements.
Changes in rigidity between the ground floor and first level (Soft Mezzanine) due to openings in some walls on the first level.
The densities (total wall area / floor area) are below 4% as recommended in some studies.
It was determined that the case study building does not meet the seismic performance objective provided by the Venezuelan seismic code Covenin 1756. The results suggest that the case study building has low ductility in the east-west direction associated with seismic demands concentrated at the base of the building in few components and low utilization ratios in other elements. The flexural strength of two force-controlled components is exceeded in the E-W direction, suggesting that these localized brittle failures could lead to partial or complete collapse of the building. The results of the study suggest that a response modification coefficient R should not be greater than 1.4 in the east-west direction, while the 4.5 assumed in the design is adequate in the north-south direction. The study also identifies the torsional sensitivity of the design, which would fall under the classification of “Extreme Torsional Irregularity” per ASCE 7. While this study is limited to one case study building, it is representative of Tunnel-type mass housing development projects. developed in Venezuela. Further research is needed to identify whether similar observations apply more broadly to this type of widely used tunnel construction.
Featured recommendations:
Increase wall thickness and obtain a density greater than 4% in both orthogonal directions.
Consider new walls on the perimeter to mitigate inelastic torsional risk.
Carry out a seismic design based on performance and a non-linear dynamic analysis that allows visualizing the inelastic behavior of the proposed configuration and determining, based on its performance, whether it is acceptable.
Increase wall thickness and obtain a density greater than 4% in both orthogonal directions.
Consider new walls on the perimeter to mitigate inelastic torsional risk.
Carry out a seismic design based on performance and a non-linear dynamic analysis that allows visualizing the inelastic behavior of the proposed configuration and determining, based on its performance, whether it is acceptable.