טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKatriel Elad
SubjectOptimal Seismic Retrofit of 2D Reinforced Concrete Frames
with Masonry Infill Using Various Technologies
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Oren Lavan
Professor Oded Amir
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Earthquakes and their consequences have been known to humanity since the beginning of time. When a building that is designed to withstand only static loads has to resist also horizontal forces due to an earthquake, it might collapse and cause damage and loss of life. Older buildings were not designed to withstand earthquakes, or designed according to old codes. Those buildings must be examined, analyzed and retrofitted to meet the standards of today's codes. It is a complicated engineering task, demands not only an investment in the construction of the retrofitting itself but also in its design and calculation.

A widespread constructive system in old buildings is the reinforced concrete (RC) frame with masonry infill (MI). The MI is not typically considered part of the structural system for vertical loads. Nonetheless, in ground motions due to earthquakes, it is apparent that the infill works as part of the structural system.

When forces are low the infill may assist the building in resisting earthquakes, making it stronger than initially anticipated. However, under stronger earthquakes the MI might fail. Its failure can cause undesirable effects such as soft story mechanism or "short column" phenomenon.

In order to retrofit buildings with MI against earthquakes, the infill has to be given special care and consideration, such as: separation of the infill and the frame, FRP retrofitting, shotcrete cover and damper additions, among other techniques. Each of the above techniques has its advantages and disadvantages.

Choosing the most suitable technique or techniques to retrofit a specific RC frame is a problem by itself and depends upon many variables. The large amount of information turns the task of retrofitting a RC frame with MI in the lowest cost possible into a non-trivial task even for experienced engineers. Therefore, a better way to make the process of choosing the retrofitting techniques and schema for those cases is needed - i.e. a way to optimize the retrofitting design for RC frames with MI.

Structural optimization mainly focuses on new buildings. Most of the work on the optimization of retrofitting existing buildings does not take into account the infill of the frames. Although it is clear that when neglecting the infill, buildings react in completely different ways. Papers that take the MI into account, mostly focus on only one kind of retrofitting method.

The question what is the most efficient way of retrofitting a specific RC frame with MI using several retrofitting techniques is usually not dealt with research papers.

In this research an optimization method for retrofitting RC frames with MI to withstand a seismic hazard using various techniques was developed. The research is analytical and numerical methods were used. Two case studies are presented, demonstrating that the method can provide a decision-making tool when facing a problem of retrofitting an RC framed structure with MI against earthquakes. Hopefully the research will lead to retrofitting RC framed structures with MI that are not retrofitted due to high costs.