Category: South America

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Report # 12 : Clay brick/concrete block masonry walls with concrete floors (predating seismic codes or with a few seismic features)

by Luis G. Mejia

Typical multi-family housing construction found in urban areas of Colombia. It is a modern construction practice and represents approximately 50% of the housing stock for medium-rise (4- to 6-story high) buildings constructed in the last 25 years. This type of construction generally predates seismic codes; however, some buildings of this type were constructed after the first edition of the Colombian Seismic Code was issued in 1984. This type of construction can be found either on flat or on sloped terrain; vertical stiffness irregularity in the sloped terrain conditions may introduce additional unfavorable effects. Due to poor construction practices and poor detailing of the reinforcement, this construction is considered to be very vulnerable to earthquake effects.

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Report # 11 : Gravity Concrete Frame Buildings (Predating Seismic Codes)

by Luis G. Mejia

This is typical multi-family housing construction found in urban areas of Colombia that predates seismic codes. This housing type is widely used and represents 60% of the existing housing stock. At the present time, poor people occupy buildings of this type. This construction is rather vulnerable to seismic effects due to a limited amount of transverse reinforcement (ties); this is especially true for columns. This structural system is very flexible when subjected to lateral seismic loads. The quality of materials and workmanship is typically rather poor. In many cases, buildings of this type are constructed on a very steep terrain; soil condition is often rather poor.

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Report # 10 : Non-engineered Unreinforced Brick Masonry Building

by Luis G. Mejia

This type of housing is typically constructed in urban and rural areas in the interior of Colombia. This type of construction is especially widespread in the following provinces of the Andean region of Colombia: Antioquia, Caldas, Risaralda, Quindio, Tolima and Valle, where it constitutes approximately 60% of the housing stock. It is used exclusively as residential housing. This construction is very vulnerable to earthquake effects due to its brittle behavior. It has demonstrated poor seismic performance in several Colombian earthquakes.

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Report # 8 : Buildings with hybrid masonry walls

by Ofelia Moroni, Cristian Gomez, Maximiliano Astroza

This housing type represents a common multi-family urban construction in Chile. Practice of this construction “mainly used for dwellings and for up to 4-story apartment buildings” began in the 1980s. The main load-bearing system consists of masonry walls in the transverse direction and reinforced concrete walls in the longitudinal direction. In some cases, longitudinal walls are of reinforced masonry construction (instead of concrete construction). Masonry walls in the transverse direction are usually confined with concrete posts at the ends (such as is found in confined masonry construction). Buildings are usually regular in plan and in elevation. The seismic design code does not address this building type. However, the Chilean Ministry of Housing has issued specifications for 1- and 2-story dwellings, which have mainly been followed in the design (even in taller buildings of this type). Performance in the 1985 Llolleo earthquake was rather poor, with most buildings experiencing structural damage.

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Report # 7 : Confined block masonry building

by Ofelia Moroni, Cristian Gomez, Maximiliano Astroza

This construction practice started during the 1940s after the 1939 earthquake that struck the mid-southern region of Chile. It is mainly used for dwellings and apartment buildings up to four stories high. Buildings of this type are found in all regions of Chile. This is a confined masonry construction, consisting of load-bearing unreinforced masonry walls (commonly made of clay units or concrete blocks) confined with cast-in-place reinforced-concrete, vertical tie-columns. these tie-columns are built at regular intervals and are connected with reinforced concrete tie- beams cast after the masonry walls have been constructed. Tie-columns and tie-beams prevent damage due to out-of-plane bending effects and improve wall ductility. Floor systems generally consist of cast-in-place reinforced slabs with a thickness between 100 to 120 mm. Confined masonry walls have limited shear strength and ductility compared to reinforced concrete walls. Nevertheless, typical buildings of this type have good earthquake resistance, because they have high wall densities and because wall layouts are symmetric and regular, both in plan and elevation. Their seismic behavior has been satisfactory, particularly in one- or two-story-high buildings during strong earthquakes [Monge, 1969].

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Report # 6 : Concrete Frame and Shear Wall Building

by Ofelia Moroni, Cristian Gomez, Maximiliano Astroza

Buildings of this type are used mainly for offices or hotels, and they are found in large cities throughout the country. At the present time this building type represents about 15-20% of the high-rise building stock in Chile (building with more than 10 stories). The structural system consists of reinforced concrete frames and shear walls. The walls are typically located around the staircases and the elevators, while the frames may be uniformly distributed in plan or at the perimeter only. Most of the lateral load-bearing elements exist along the full building height in the elevation and in both directions of the building plan. In some buildings the walls are perforated with openings and coupled with lintel beams. Some buildings of this type have one or more basement floors. In general, these buildings are quite stiff. Seismic performance is very good, strength and stiffness are controlled, and torsion effects are minimal. Problems that may occur in the future are related to the reduction in the wall density, and introduction of soft-story or torsional effects.

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Report # 5 : Reinforced Clay/Concrete Block Masonry Building

by Ofelia Moroni, Cristian Gomez, Maximiliano Astroza

This is a rather recent construction practice followed since 1970, and it has been widely used for dwellings and up to 4-story-high apartment buildings. Buildings of this type can be found both in urban and rural areas of Chile. The main load-bearing elements are masonry walls reinforced with vertical steel reinforcement bars and placed in the hollow cores of clay masonry units (hollow clay tiles) or concrete blocks. Horizontal reinforcement bars are placed in horizontal bed joints. Masonry shear walls are tied together at floor levels by means of reinforced concrete beams in a regular structural layout. Stiffness distribution both in plan and elevation is uniform. Prior to 1986, there was no seismic design code for this structural type. During the March 3, 1985 Llolleo earthquake, performance of buildings of this type was rather poor, mainly due to construction problems, such as partial grouting in the hollow cores with reinforcement, poor quality of the mortar, and lack of horizontal reinforcement. Following the earthquake, the Chilean Design Code NCh1928 code was published based on the U.S. Uniform Building Code (UBC-1979) and on the seismic performance of this construction type reported in previous earthquakes. Since 1993, when the last version of NCh1928 was published, and more restricted requirements were enforced, the use of this type of construction has been less frequent, in part because of economic reasons.

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Report # 4 : Concrete Shear Wall Buildings

by Ofelia Moroni, Cristian Gomez

This housing type is mainly characterized by reinforced concrete shear walls that are built in both directions along the entire height. Some of the walls may be perforated with openings (coupled walls). These buildings are multiple housing units and are found in the major urban areas in Chile. Stiffness and mass distribution are regular and most of them may have a symmetry axis in at least one direction of the plan. In general, these buildings are quite stiff because they must resist a base shear of 5-6.7% (depending on the seismic zone) and the story drift must be equal to or less than 0.002. Seismic performance is very good, strength and stiffness are controlled, and torsional effects are minimal. The buildings may have one or two basement floors. Problems that may appear in the future include reduction in the wall density, introduction of soft floor, or torsional effects.

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Report # 3 : Steel Frame Buildings with Shear Walls

by Elias Arze-L.

These buildings are modern steel composite structures ranging from 3 to 24 stories. The buildings have a rigid steel frame with floor diaphragms made of post-tensioned concrete slabs or composite steel decking, with or without a concrete slab covering. Additional lateral force-resisting elements are added to the steel moment-resisting frame to stiffen the structure and enhance the seismic performance. These elements are steel #X# or concentric braces and reinforced concrete shear walls. The seismic performance for these composite structures is very good. Most of these buildings are used as apartments or offices.

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Report # 2 : Traditional Adobe House with Reinforcement

by Virginia I. Rodriguez, Maria I. Yacante, Sergio Reiloba

This construction type is a single-family house. In general, it is a single-storey building, an isolated construction found in the rural areas of San Juan and Mendoza. The traditional adobe block masonry walls are reinforced with foundations and plinth structure, which provide structural strength. A deficiency in this type of construction is that the adobe blocks deteriorate due to prolonged exposure to humidity.

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