Seismic Response of Multistorey Flat Slab Building with Shear Wall using ETABS

Seismic Response of Multistorey Flat Slab Building with Shear Wall using ETABS

Jincy.D.S, PG Student Department of Civil Engineering Mangalam college of Engineering Kottayam, India

R Senthil Kumar

Associate Professor, Department of Civil Engineering Mangalam College of Engineering

Kottayam, India

Abstract The floor system of a common type of concrete building is a flat concrete slab (without supports).This system is really easy to construct and efficient in that regard. It stipulates the optimum height of the building for a specified number of stories. Currently, the flat slab method is frequently utilised in construction. It allows for greater architectural flexibility space, low building height, easier formwork, and a quicker construction period, construction time. Furthermore, Flat slab building structures much more adaptable than conventional concrete as there are no beams present. They are more susceptible to harm earthquakes. The purpose of this research is to examine the behaviour of a G+9 flat slab structure with shear wall. The normal lateral behaviour of a flat slab construction is analysed using dynamic analysis utilising the ETABS software by response spectrum method. The effectiveness and functionality of Indian standard code in seismic zone III has been observed.

KeywordsFlat slab, Shear wall, ETABs, Linear Time history Analysis

1. INTRODUCTION

   An earthquake (also known as a quake, tremor, or temblor) is the severe shaking of the Earth's surface, which can destroy huge structures and kill thousands of people. Earthquakes have been recognised as one of the most devastating natural disasters for centuries. Malls, theatres, and other constructions that require broad beam-free zones are constructed with flat slabs. Flat slab construction requires shear walls when earthquake resilience is considered. IS 1893 Part1:2002 permits the construction of flat slab structures to resist both vertical and lateral stresses in areas of low seismicity (Zone II). In zones III, IV, and V, however, the code prohibits the construction of flat slabs without a lateral load resisting system or lateral force resisting system. In this research, modelling and analysis of the seismic response of a ten-story (G+9) flat slab multi-story building with a shear wall were conducted. Shear walls are installed at the building's corners and in the middle, and then the model's efficiency and serviceability under Indian standard circumstances in seismic zone 'V' are evaluated.

   A. Flat Slab

   Flat slabs are preferred by architects and clients due to their aesthetic and financial benefits. Although this type of reinforced concrete construction has a number of advantages over framed structures, it also has a number of problems due to the brittle punching failure at the slab column junction and the considerable horizontal deformation. Many researchers argue that flat slabs used in

   higher seismic zones should be built to resist solely gravity loads, while lateral loads should be transferred by a system resistant to lateral force. The column itself or a column capital and drop panel can support a flat slab. Due to the lack of frame action, which causes excessive lateral deformation, the performance of flat slab buildings under seismic loading is inferior to that of framed structures. The most vulnerable component of a flat slab construction is the slab column joint. The behaviour of flat slab column connections has been the subject of extensive research. The mode of failure is dependent on the type and quantity of loading. Punching shear strength of slab column connection is essential and is heavily dependent on gravity shear ratio. A punching failure of a flat slab may come from the transfer of shearing force and an imbalanced moment between the slab and column.

   B.Shear Walls

   Shear walls are one of the most prevalent lateral load- resisting systems seen in high-rise buildings. Shear walls have great in-plane stiffness and strength, allowing them to resist huge horizontal loads and support gravity loads simultaneously.

   Buildings utilise R.C. shear walls to resist lateral forces caused by wind and earthquakes. Typically, they are installed between column lines, in stairwells, liftwells, and shafts housing other utilities. Shear walls provide lateral load resistance by transmitting wind and seismic loads to the base. In addition, they offer lateral rigidity to the system and support gravity loads. They are widely employed to prevent the collapse of tall buildings. International Research Journal of Engineering and Technology (IRJET) Shear wall may become inevitable from an economic and control of lateral deflection standpoint. When shear walls are strategically placed in a building, they can form an effective system for resisting lateral forces. Numerous construction rules mandate the installation of these barriers to make homes safer and more sturdy.

   The column-slab system of a flat slab building is designed to resist both gravity loads and earthquake- induced lateral inertialoads. Due to the low lateral stiffness and lateral load resistance of the column-slab system, the columns are incapable of accommodating the additional secondary moments generated by the large lateral drift of the flat slab building.

   HYSD50 0	Rebar	200000	0	76.972 9	Fy=500 MPa, Fu=545 MPa
   M30	Concret e	27386.1 3	0.2	24.992 6	Fc=30 MPa
   Mild250	Rebar	200000	0	76.972 9	Fy=250 MPa, Fu=410 MPa

   Consequently, there are significant problems with the usage offlat-slab buildings in seismic zones IV and V.

   Attempts were made to compensate for this lack of capacity in flat slab structures by lowering overall lateral deformation and so improving their overall lateral resistance by adding structural walls as a supplemental lateral load resisting system(LLRS).

   The shear wall is modeled with a thin shelled element usingM30 grade concrete at a depth of 250mm.

   Fig 1. Flat slab with drop panel and column head

2. METHODOLOGY

   Analytical research of the models dealized linear timehistory approach was carried out to analyse the seismic

   dealize of flat slab building with shear wall. ETAB software was used to conduct the analysis. Only the maximum values are used in the response spectrum method for calculating other parameters such as displacement and member forces.

   1. Modeling

      The fundamental goal of structural analysis of building structures is to determine the distribution of internal forces andmoments across the entire structure or a portion of it,

   2. Analysis

      Fig 2. 3D View of model

      Fig3. Plan view of the model

      as well as to identify essential design conditions in all

      sections. The geometry is frequently dealized by

      imagining the structure to be composed of linear and plane two-dimensional parts. The ETABS application is used to do nonlinear dynamic time history analysis in order to acquire the modal properties.

      • Properties

        The properties of various materials used are shown in the table.

        Name	Type	E MPa		Unit Weight kN/m³	Design Strengths
        A416Gr270/p>	Tendon	196500.6	0	76.9729	Fy=1689.91 MPa, Fu=1861.58 MPa
        A615Gr60	Rebar	199947.98	0.3	76.9729	Fy=413.69 MPa, Fu=620.53 MPa

        TABLE I. MATERIAL PROPERTIES

      • Response spectrum method

      Response spectrum analysis is a method to estimate the structural response to short, nondeterministic, transient dynamic events. Examples of such events are earthquakes and shocks. Since the exact time history of the load is not known, it is difficult to perform a time-dependent analysis. Due to the short length of the event, it cannot be considered as an ergodic ("stationary") process, so a random response approach is not applicable either.The response spectrum method is based on a special type of mode superposition.

      The idea is to provide an input that gives a limit to how much an eigenmode having a certain natural frequency anddamping can be excited by an event of this type.

      The analysis of flat slab structure has been done by

      using ETABS 2016 software package. Before analysis all the

      required elements of the structure needs to be defined earlier like material properties, loads, load combinations, size of members, response spectrum function etc. once the analysis has been done we can extract the results like displacement,storey shear, storey drift , drift ratio, storey stiffness for comparing the performance of all models. The

      flow chart shows the steps involved in the analysis of ETABS.

      Defining dimensions of the building

      Defining the members and material properties

      Assigning loads and load combinations

      Run check model to find errors

      Run Analysis Extract results and discuss

3. RESULTS

   This section defines about detail discussions of software results of flat slab building model with shear wall with respect to storey shear, storey stiffness, storey displacement, storey drift etc

   1. Storey Shear

   2. Storey Stiffness

   3. Storey Displacement

   4. Storey Drift

   5. Storey Overturning Moment

   6. Auto Lateral Loads

   .

4. CONCLUSION

This study examines multi-story flat slab construction. G+9 building with shear wall at corners and middle of the building. Based on analysis following findings have been drawn for the structural framework of a flat slab.

• To increase the performance of the flat- slab structure under horizontal loads, particularly when speaking about seismically prone areas

  modifications of such system can be done by adding structural elements such as RC shear wall.

• From the results obtained from the analysis a multistory flat slab building with shear wall at corners and middle is safer and recommendedthan the one having shear wall at core or centre.

ACKNOWLEDGMENT

Iam grateful to the Almighty who is the source of knowledgeand one who guides us in all aspects to bring out this paper work a successful one. I express my deep respect and profound gratitude to my college management committee for providing us an opportunity and infrastructure to undertake this paper work. I express my sincere gratitude to Prof.

Dr.Vinod P Vijayan, Principal, Mangalam college of Engineering and Prof. Dr. Ramesh Kumar, Head of Civil Department for providing an opportunity to undertaken this work. I express sincere gratitude to my family and friends forencouraging in the completion of this work.

REFERENCES

[1] Analysis and design of flat slab: Professor, Department of Applied Mechanics, Walchand College of Engineering, Sangli,

Maharashtra, India

[2] Dr. Uttamashagupta et.al, Seismic behavior of buildings having flat slabs with drops. International Journal of Emerging Technology andAdvanced Engineering website:

[3] www.ijetae.com (ISSN 2250-2459, volume 2, issue 10, October

2012).

[4] Ms. Navyashree K and Sahana T.S Use of flat slabs in multi- story commercial building situated in high seismic zone. IJRET: International Journal of Research in Engineering and Technology2014.

[5] Mrs.Sumitpahwa et.a1, Comparative study of flat slab with old traditional two way slab. International Journal of Latest Trends in Engineering and Technology (IJLTET)2014.

[6] Pushover Analysis of Existing 4 Storey RC Flat Slab Building A.

E. Hassaballa , M. A.Department of Civil Engineering, Jazan University, Jazan, KSAa

[7] Performance of Flat Slab Structure Using Pushover Analysis Dhananjay D.Structural Engineering Department, Govt. College of Engineering Aurangabad,

[7] Seismic Behaviour of Flat Slab Systems Pradip S.Landel, Aniket

B. Raut Associate Professor Government College of Engineering,

Amravati Maharashtra, India

[8] IS:456-2000-code of practice for plain andreinforced concrete