Category: Seismic Protection Systems

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Report # 152 : Base Isolation of Confined Masonry

by Noemi Graciela Maldonado, Dr. Miguel Eduardo Tornello

Most of Argentine Republic territory may be considered seismic.Great Mendoza is an important social-economic area in the mid- western region and it has the greatest seismic risk in the country. In the last 200 years or so, there have been important earthquakes affecting building structures. Consequently, new techniques aimed at controlling vulnerability must be developed. Methodology: An investigation of the actual application of Basal Seismic Isolation (BSI) on a building ‘Students’ House’ belonging to the Technological National University (UTN) is implemented. Research of the isolation system for near source motions has been done. The construction of three modules of student houses has been done in 2004, with confined masonry and reinforced concrete for three levels and prestressed slabs. Both buildings have accelerometers to register earthquake effects. The complex is completed with a building of two levels for administration with confined masonry. The aim is to control BSI displacement. The strategy proposed was to add damping to the isolation system within certain limits and the results are compared to similar fixed base building. To control near source displacements, additional damping is an applicable and economic strategy. Although with this strategy there is increased acceleration , it is far less than in the case of fixed base building

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Report # 77 : Buildings protected with “disengaging reserve elements” (vyklyuchayu-shchiesya svyazi)

by Jacob Eisenberg, Svetlana Uranova, Ulugbek T. Begaliev

This building type is characterized with a special system of seismic protection called “Disengaging Reserve Elements” (DRE). DRE are installed at the ground floor level of a building, which is typically a RC frame structure. The upper part of the building, usually 9 stories high, is a load-bearing wall structure, either of large-panel RC construction or brick masonry construction. DRE consist of a “rigid structure” (usually RC wall panel) connected to the adjacent RC frame members by means of disengaging restraints. Disengaging restraints are sacrificial reserve elements (fuses) that serve as restraints for the “rigid structures.” Typical restraints are steel plates joined together by means of rivets or steel bolts, steel bars, concrete prisms or cubes, etc. Initially, at the lower ground motion level, DRE and RC frame work together; at that stage, disengaging elements transfer lateral loads to rigid structures. DRE is an adaptive seismic protection system whose unique feature, the variable (self-adjusting) rigidity and periods of vibration during an earthquake, prevent resonance. This system is widely used in seismic-prone areas of Russia and Kyrgyzstan. Buildings of this type have not yet been exposed to the effects of damaging earthquakes.

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Report # 76 : Load-bearing wall buildings protected with the “sliding belt” base isolation system

by Jacob Eisenberg, Svetlana Uranova, Marat Abdibaliev, Ulugbek T. Begaliev

Sliding belt is a base isolation system developed to protect buildings from seismic effects by reducing and limiting the level of seismic forces. The sliding belt system is installed at the base of the building between the foundation and the superstructure. The foundation is usually made of cast-in-situ concrete and the superstructure is typically a load-bearing wall structure, either a 9-story, large concrete panel system, or a 3-story brick masonry construction. Once the earthquake base shear force exceeds the level of friction force developed in the sliding belt, the building superstructure starts to slide relative to the foundation. The lateral load transferred to the superstructure is expected to be approximately equal to the frictional force that triggers the sliding of the structure. The sliding belt consists of the following elements: (a) sliding supports, including 2-mm-thick stainless steel plates attached to the foundation and 4-mm Teflon (PTFE) plates attached to the superstructure, (b) reinforced rubber restraints for horizontal displacements (horizontal stop), and (c) restraints for vertical displacements (uplift). A typical large panel building with plan dimensions 39.6 m x 10.8 m has 63 sliding supports and 70 horizontal and vertical restraints. The sliding belt scheme was developed in CNIISK Kucherenko (Moscow) around 1975. The first design application in Kyrgyzstan was made in 1982. To date, the system has been applied on over 30 buildings in Bishkek, Kyrgyzstan. All these buildings are residential buildings and are presently occupied. Base-isolated buildings of this type have not yet been exposed to the effects of damaging earthquakes.

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Report # 9 : Multistory base-isolated brick masonry building with reinforced concrete floors and roof

by Fu L. Zhou, Zhong G. Xu, Wen G. Liu

This is typically a 5- to 8-story building with commercial enterprises on the ground floor and residences above. Brick masonry buildings have been used in China for thousands of years. This construction practice possesses the advantage of easy manufacture and low cost; however, the brittleness of the brick masonry material combined with weak seismic resistance induces severe damage or collapse of buildings and causes thousands of deaths during an earthquake. Since 1990, base-isolated brick masonry buildings with reinforced concrete floors/roof have been used more widely in China. The base-isolated building consists of an isolation system (laminated rubber isolation devices) superstructure and substructure. The base-isolation system is located on top of the walls or columns in the basement or at the ground floor level of a building without a basement. The superstructure consists of conventional multi-story brick masonry walls and reinforced concrete floors/roof. The substructure is part of the building beneath the isolation system and consists of the basement and the foundation structure. The base-isolated masonry structure results in an increase in seismic safety by a factor of 4-12 times as compared to that of a non-isolation masonry structure. The high seismic resistance of the base isolation structure house has been proven by shake table tests and in many actual earthquake events in China and other countries. The wide usage of base isolation technology indicates that the era of strong earthquake-proof buildings is coming in China.

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