International Research Journal of Engineering and Technology (IRJET) Volume: 04 Issue: 02 | Feb -2017
e-ISSN: 2395 -0056
www.irjet.net
p-ISSN: 2395-0072
Effect of Infill and Mass Irregularity on RC Building under Seismic Loading Oman Sayyed1, Suresh Singh Kushwah2, Aruna Rawat3 1Post
Graduate Student, Department of Civil Engineering, University Institute of Technology (RGPV), Bhopal, India & HOD, Department of Civil Engineering, University Institute of Technology (RGPV), Bhopal, India 3 Asst. Prof. Department of Civil Engineering, University Institute of Technology (RGPV), Bhopal, India
2Professor
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Abstract – If there is a sudden change in mass, stiffness and strength along the vertical or horizontal plane of a building then it may suffer serious damages due to seismic loading. Such a building which has an irregular distribution of mass, strength and stiffness along the building height can be termed as vertically irregular building. These irregularities cause deterioration of the building which leads to collapse. In this paper, the focus is made on the performance & behavior of regular & vertical irregular G+10 reinforced concrete (RC) buildings under seismic loading. Total nine building models having irregularity due to partial infill and mass irregularity are modeled & analyzed. Response spectrum analysis (RSA) is carried out for these building models for seismic zone V and medium soil strata as per IS 1893:2002 (part I). Seismic responses like storey displacement, storey drift, overturning moment, storey shear force, storey stiffness are obtained. By using these responses comparison is made between the regular and irregular building models. This study focuses on the effect of infill and mass irregularity on different floor in RC buildings. The results conclude that the brick infill enhances the seismic performance of the RC buildings and poor seismic responses are shown by the mass irregular building, therefore it should be avoided in the seismic vulnerable regions.
Irregularities
Vertical irregularity •Irregular distribution of stiffness, mass and strength along the height. •Setback
Horizontal irregularity •Irregular distribution of stiffness, mass and strength along the plan. •Diaphragm discontinuity •Re entrained corners •Asymmetrical plan shapes
Fig.1: Detail of irregularities in RC buildings. Table 1: Vertical irregularity limits prescribed by IS 1893:2002 Type of Vertical Irregularity Stiffness Irregularity Soft Storey
Stiffness Irregularity Extreme Soft Storey
Key words: Equivalent Diagonal Strut, Infill irregularity, Masonry infill, Mass irregularity, Response spectrum analysis, Vertical Irregular.
Mass Irregularity
1. INTRODUCTION In the past, a number of major earthquakes have uncovered the deficiency in buildings. This weakness causes deterioration of the building which leads to the collapse. This weakness mostly occurs due to the presence of irregularities in a building system. It has been observed that regular buildings perform better than irregular buildings under seismic loading. The irregularities in the buildings are present due to irregular distribution of mass, strength and stiffness along the height and plan of building. Mainly these irregularities are classified into two types as shown in Fig. 1 and the irregularity limits prescribed by IS 1893:2002 (part I) are given in Table 1.
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Impact Factor value: 5.181
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Prescribed Limits A soft storey is one in which the lateral stiffness is less than 70 percent of that in the storey above or less than 80 percent of the average lateral stiffness of the three storeys above. A extreme soft storey is one in which the lateral stiffness is less than 60 percent of that in the storey above or less than 70 percent of the average stiffness of the three storeys above. Mass irregularity shall be considered to exist where the seismic weight of any storey is more than 200 percent of that of its adjacent storeys.
Vertical Geometric Irregularity
Vertical geometric irregularity shall be considered to exist where the horizontal dimension of the lateral force resisting system in any storey is more than 150 percent of that in its adjacent storey.
In-Plane Discontinuity in Vertical Elements Resisting Lateral Force
An in-plane offset of the lateral force resisting elements greater than the length of those elements.
Discontinuity in CapacityWeak Storey
A weak storey is one in which the storey lateral strength is less than 80 percent of that in the storey above.
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