Ph.D

Mrs Noorifard Azadeh will  present her P.H.D thesis on "A Model for Determining the Arrangement and Geometrical Specifications of Non-Structural Walls in the Final Stages of Basic Architectural Design to Improve the Seismic Behavior of Buildings" in Iran at 17:30 P.M on Sunday, April 30 th 2017.

Supervisors:

Dr. Fatemeh Mehdizadeh Saradj

Dr. Mohammad Reza Tabeshpour

Abstract

Experiences of past earthquakes show that some designed and constructed buildings by engineers were severely damaged due to disregarding the negative effects of infill walls, although there were other buildings without any lateral force resistance elements constructed by non-specialist people remained stable due to positive effects of infill walls. Structural engineers often consider masonry infill walls as non-structural elements and design the structure as the bare frame. On the other hand, architects determine the arrangement and specifications of walls without considering their seismic behavior. In this way, one of the most important non-structural elements with the potential to destroy the whole building has been neglected in the engineering community. Numerous studies have been carried out about seismic behavior of infill walls and their effects on buildings by researchers from structural and earthquakes engineering with detail oriented approach, while architects are responsible for designing the form and geometry of walls in basic design and determining the detail and material of walls in detailed design. So, the main purpose of this dissertation is to prevent the adverse effects of infill walls on seismic behavior of structures and use the maximum potential of walls and increase the capacity of the structure by controlling and modifying the architectural drawings.

In this research, experimental and logical argumentation strategies are used. In the first stage, experiences of past earthquakes, results of experiments and modeling, seismic codes and principles of earthquake engineering are investigated. Accordingly, effective measures in different stages of design are presented in the form of check lists for engineering applications to prevent undesirable seismic behavior of walls. In the sampling stage, architectural drawings of 364 conventional residential buildings in Tehran are investigated and classified and 21 cases in four main defined groups are selected. Then, based on statistical study on 625 buildings under construction in Tehran, common materials and systems of structures and walls are determined. Thereafter the structure of all selected buildings is designed with the same assumptions in order to control some variables.

In this research, a total of 2718 models are analyzed by a structural analysis and design software. 246 two-dimensional frames are analyzed to study the methods of determining the story stiffness and 75 two-dimensional frames are analyzed to study short column. In the main part of analysis in group one to three, all cases studied in the following three conditions: bare frame as a representative of design condition, infilled frame as a typical of construction condition and modified infilled frame which is checked by proposed algorithm. In these three groups, 120 three-dimensional buildings with different arrangement of walls in terms of torsion, soft story and short column are analyzed. Positive effects of selected modified cases including increase of stiffness and strength and decrease of lateral displacement are compared with the bare frame. At the end of this section, by identifying the most effective factors in producing the torsion, peripheral walls and the ones close to the edge of the building and the specifications of walls including ratio of opening area, the distance of wall from the edge of the building, aspect ratio of walls, material of wall and its finish, an approximate method has been developed with the performance of 98%. In group four, 2277 three-dimensional buildings with different arrangement of walls just in terms of soft story are investigated. As a result, an approximate method with the performance of 97% has been developed by identifying the most effective factors in creating soft story including percentage of infilled frames in upper story, percentage of infilled frames in lower story and the length ratio of walls in story under investigation to upper story,.

Results of studies and analyses in this dissertation have been developed in the form of nine algorithms to evaluate and reduce the adverse effects of infill walls in the final stages of basic architectural design; Five algorithms are related to the accurate model and can be used when the software model of structure is made and four algorithms are related to the approximate model which does not need specifications of structure and only geometrical specifications of architectural drawings are sufficient. By these two models, through minor modifications in the specifications of walls, it is possible to prevent torsion caused by irregular arrangement of infill walls in plan, soft story caused by irregular arrangement of infill walls in elevation, and short column caused by partial infill walls. While in the meantime the concept and specifications of architectural plan can be kept unchanged.  In this way, without using extra material, earthquake resistance of building is increased. As this model has been designed for final stages of basic architectural design, so creativity and ideas of architects will not be interrupted. The test results of approximate model indicate that this model has high performance for various groups of architects and there is no relation between using this model and the level of education, field of study, trends and years of work experience.

Keywords: Non-structural walls, Basic architectural design, Seismic behavior, Torsion, Soft story, Short column, Lateral stiffness