Evaluation of Response Reduction Factor for Flat Slab Structures

Flat slab systems are more effective than traditional slab-beam-column framed system because of its speedy construction, Easier formwork, use of space and architectural significance. Flat slab system advantageously used where we required large area such as auditorium, theatre halls, showrooms of shops and so on. Flat slab system generally consists of drop panel, column head, column strip and middle strip. In flat slab systems there are generally two types of failures occurs namely flexural failure and punching shear failure. To overcome this problem, we provide drop panel and column head at columns. Response reduction factor is the ratio of elastic base shear to design base shear. Base shear is generated due to the lateral forces. Response factor denotes the capacity of the frame to dissipate energy through inelastic behavior. ‘R‘ factor depends upon number of stories as the number of stories increases R factor decreases. Response reduction factor is depends upon ductility factor, strength factor, structural redundancy and damping. Actual intensity of earthquake is reduced by response reduction factor ‗R‘. As flat slab system is not frame system so we cannot use ‗R‘ factor directly without any basis. IS code does not state the ‗R‘ factor for flat slab system. This paper deals with the evaluation of response reduction factor for flat slab at seismic zones IV and comparison of pushover curves by pushover analysis. For that first step is to collect the data for analysis of flat slab and conventional Frame structure modelling of structure on STAAD.Pro Software. Then Design the flat Slab structure by considering R=1,2,3,4,5 & RCC frame structure by considering R=3,5 for different load Combinations.

The plan for the commercial building G+7 with floor to floor height 3.6m is kept for all storey including ground floor for flat slab structure and frame structure. The panel size is 5.1m x5.1m for both the structures. End conditions of all the columns is assigned as fixed support. For partition wall the brick material is siporex block of grade 1 having density 9kN/m3. All the model analysis and designed in STAAD.Pro software. Analysis of both the structure by Static method. Grade of the concrete is M25 and steel is Fe415.

Total numbers of models are seven created in STAAD.Pro having different response reduction factor for flat slab structure and frame structure. Five models are created for flat slab structure having different response reduction factor (R factor) and two models are created for frame structure of different response reduction factor(R factor) as 3 for ordinary

parameters required for design are mention below in the table as,

Table 3: Column Details for Frame structure

According to IS: 1893 (Part 1):2002, Load combination used as follows-

 1.5DL + 1.5LL

 1.5DL ± 1.5EQx  1.5DL ± 1.5EQz  1.2DL + 1.2LL ± 1.2EQx  1.2DL + 1.2LL ± 1.2EQz  0.9 DL ± 1.5EQx  0.9 DL ± 1.5EQz Where, DL is Dead load and LL is Live load, EQX and EQZ are Earthquake loads in the X- and Z- directions, respectively

Fig4: Elevation of G+7 storey building of frame structure 2.4 Design Base shear Lateral forces applied on building along X & Z direction due to seismic effect or wind at base is known as base shear. Base shear of all models considering different R factor for flat slab structure & frame structure as, Table 6: Design Base shear with manual validation

I would like to thanks to first my project guide Prof. V. P. Bhusare as well as our PG Co-ordinator Prof. Pallavi Pasnur madam, Department head Prof. Dhawale A. W. sir and second shift co-ordinator Prof. Phatak U.J. and special thanks to Director of SaltInfra.pvt.ltd Mr.Manoj Baraskar sir and all my friends who help me during this project work.

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Assistant Professor, Department of Civil Engineering JSPM‘s ICOER Wagholi, Pune, India