טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBrodsky Alexander
SubjectContribution of Masonry Infill Walls to Reduce the Risk
of Progressive Collapse of RC Frame Buildings in
the Extreme Event of a Supporting Column
Failure
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Oded Rabinovitch
Professor Emeritus David Yankelevsky
Full Thesis textFull thesis text - English Version


Abstract

Structural systems comprising frames with masonry infill walls are widely implemented in residential and public buildings. The masonry infill wall is usually considered as a non-structural element. Yet, even if not meant to, it plays a major role in the structural response in the case of an extreme event such as local impact, blast or earthquake. Extensive efforts have been invested in studying of the frame-infill wall composite behaviour under the action of lateral loads simulating earthquake actions. Extreme events may also severely damage a supporting frame column and lead to a progressive collapse. Opposed to earthquake events, the case of loss of a supporting column that is associated with vertical gravitational loading has gained considerably less attention.

The loss of a supporting column tends to cause a significant increase of the frame deflection that may be restrained by the infill, thus developing interaction forces between the infill wall and the frame. These interaction forces affect the shear forces and bending moments distributions along the frame elements and may lead to failure of the frame.

The present research aims at addressing these important issues and gain insight into the behaviour of a composite infilled-frame in the case of loss of a peripheral supporting column and into the wall-frame interaction characteristics.

The methodology developed in the study is based on a quasi-static experimental approach that investigates typical RC infilled-frames subjected to gravitational loading. To address the interaction problem, the study combines experimental, analytical, and numerical tools. These tools are jointly used to focus on the infill-frame interaction and gain insight into this complex problem that is still unresolved.

The experimental results of the study demonstrate the significant contribution of the infill to the overall infilled frame resistance. Its resistance to a vertical load was increased by up to 500%; therefore, the infill wall can play a major role in maintaining the structural system's integrity and reducing the likelihood of a progressive collapse. It was found that the frame failure determines the resistance of the entire structural system. This failure is attributed to the infill-frame interaction. A detailed numerical analysis has shown that even if a numerical model successfully predicts the load-deformation behaviour, it may not properly predict the damage and failure of the infill and of the frame.

In order to characterize the interaction effects, a new experimental technique has been developed. This innovative experimental system provides new data about the interfacial tractions between the infill and the frame. This system used to investigate the effect of loading patterns and joint types on the interaction effects. The investigation shows that the infill-frame contact regions constantly change during the loading process and the infill cracking is the most significant parameter affecting the interaction. A comparative investigation of the behaviour of identical infill walls under lateral or vertical loads reveals entirely different behaviors and proves that accumulated knowledge from studies on laterally loaded walls cannot be applied to problems of vertically loaded walls. This further highlights the contribution of the present investigation.