ICART - 2023 (Volume 11 - Issue 02)

Study of Structural Behaviour of Pt Beam of a Multi-storied Building Under Seismic Load

DOI : 10.17577/IJERTCONV11IS02020

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Febin Antony, Ms: Geethu Lal, 2023, Study of Structural Behaviour of Pt Beam of a Multi-storied Building Under Seismic Load, INTERNATIONAL JOURNAL OF ENGINEERING RESEARCH & TECHNOLOGY (IJERT) Volume 11, Issue 02,

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Study of Structural Behaviour of Pt Beam of a Multi-storied Building Under Seismic Load

FEBIN ANTONY

Department of Civil Engineering Mangalam college of engineering Kottayam, India febinantony17@gmail.com

Ms: GEETHU LAL

Assistant professor Department of Civil Engineering Mangalam college of engineering

Kottayam, India

Abstract In case of RCC (Reinforced cement concrete) beam, usually the function of concrete is to take the compressive stresses and when it comes to steel the role is to take up the tensile stress. But we are not considering the mixture of concrete placed below neutral axis because of its fragile nature in tension resistance. Even though steel is provided for resist the tensile stress some minute cracks will form in the tension zone concrete. After a lot of research, it is found out that this problem can be eliminated by stressing both the steel and concrete, but this should be carried out before the load application. Pre tensioning process and post tensioning process are two different ways by which we can complete internal prestressing. In the process of pre-tensioning, before the casting of concrete using moulds, the tendons have to be tensioned first in between rigid anchor blocks cast which can be done on floor, pre-tensioning bed and also in columns. In post- tensioning the tensioning of concrete is carried out after casting of concrete. To fit the tendons concrete blocks are casted by incorporating ducts. Once the concrete attained enough strength, a jack is connected members end face and thus the high-tensile wires are tensioned and anchored by wedges. Some space will be remined after this process and this can be filled by grouting. This PT beam and RC beam effect used in several storey building under seismic is studied assessed using ETABS 2017 and also the effect of bracings on the PT beam structure

Keywords:RC beam,PT beam,ETABS

I. INTRODUCTION

Earthquake resisting reinforced concrete building design is a department deals with study of earthquakes because it has started in developed countries as well as in India. The damage

can be occurred due to different factors in an earthquake. On the last centuries India had undergone so many earthquake disasters in many placed in different scales. As a matter of fact the percentage of areas that are prone to heavy earthquakes are abouve 50% . Due to the uncertainty in the calculation of earthquake time and intensity it is considered as one of the most dangerous disaster and the destruction will not be over by effecting buildings it will also lead to human lose. Countrys north east part and Himalayan regions are subjected to high magnitude earthquake such as 8.0 and as per the study the main reason for this is Indian plate movement towards European plate and the amount by which it is happening is 50mm per year. Earthquake cant be eliminated from earth but by taking proper building construction technique it can br controlled to an extent .

In Asian countries one of the most used structures in industrial and residential building is RCC structures. PT beams are not used in buildings with small span length. Around 20 years ago we were suffered by the shortage of expertise people in the fields of prestressing but however this situation has improved a lot in these years and we are available with a lot of people and workshops to done this. one of the main reasons why the prestressed beams are economical is that, while we are using prestressed beam the depth of the beam can be reduced and in the same case if it is an ordinary beam as the span increases, we have to increase the depth of beams because of its limitations in deflection in structural engineering

construction most recent and effective structure included is PSC. Currently some of the main fields that are making use of prestressed structures are buildings, towers for communication purposes, storage which is floating in nature, subterranean structures, bridge etc. there are some main aims for structural engineers. . On the basis of availability and other common factors concrete is considered as an economical material compared to steel..

II. OBJECTIVES

  • To develop, design and conduct analysis of structure (G+14)

  • To compare the performance of RCC beam and PT beam under seismic effect

  • To compare the stiffness of structure

III . METHODOLODY

This describes the procedure for modelling the Reinforced cement concrete beam (RCC) and Post tensioning (PT) beam.

  1. MODELLING OF STRUCTURE

    Details of structure

    Storey number: G+14

    Dimension of the plan: 16m X 15m Floor to Floor height: 3m

    Materials used: M40 grade concrete and HYSD500 Steel Size of beam: 300mm X 600mm

    Size of column: 500mm X 500mm Thickness if slab used: 150mm Seismic sector V

    Fig 1 : plan of the building

    Fig 2 : Modelling of RC building

    Fig 3 : Modelling of PT building

    Fig 4 : Modelling of PT building with X bracings

    Fig 5 : Modelling of PT building with V Bracings

    Fig 6 : Modelling of PT building with inveted V Bracings

    Generating material property

    Fig 7 :material properties of concrete

    Fig 8 : material property of steel

    Properties of beam,column,slab and braces

    Fig 9 :properties of beam

    Fig 10 :properties of column

    Fig 11 :properties of slab

    Fig 12 :properties of braces

    Tendon details

    The tendon of strand area of about 93mmsq is used in this study

    Fig 13 :tendon details

    Fig 14 :tendon profile in x direction

    Fig 15 : tendon profile in y direction

    The tendon load can be define with the help of the software. In this study the jacking stress of about 1725 Mpa is used. The jacking is done from both ends. The load pattern of the tendon is given in the figure

    Fig 16 :tendon load

    Support conditions

    To dole out any sort of help either settled, stick or roller for which tap on dole out on the menu bar -> choose joint –

    >select type of help. We have used fixed supports here.

    Fig 17 :assign support conditions

    Table 1 :: load combinations

    Load combinations

    1

    LL

    9

    1.5 (DL + EQY)

    2

    LL+DL

    10

    1.5 (DL EQX)

    3

    1.5(LL+DL)

    11

    1.5 (DL EQY)

    4

    1.2 (DL +LL + EQX)

    12

    0.9DL + 1.5EQX

    5

    1.2 (DL + LL + EQY)

    13

    0.9DL + 1.5EQY

    6

    1.2 (DL +LL EQX)

    14

    0.9DL 1.5EQX

    7

    1.2 (DL + LL EQY)

    15

    0.9DL 1.5EQY

    8

    1.5(DL +EQX)

    Fig 18 :load cases

    Defining response spectrum

    The response spectrum varies as the variations in different earthquakes, but for the ease of study IS 1893:2002 specifies a response spectrum which can be considered for all purpose nature and it is dedutced from considering for some huge earthquakes .

    Fig 19 : response spectrum function

    1. RESULT AND DISCUSSIONS

      In this study the PT and RC beam is modeled and analysis is done by the ETAB software version 17. The structures are analyzed for response spectrum method. The comparison of the structures are done in the result. Folowing figures explain the maximum displacement of stories, Drift of stories and storey stiffness of PT beam and RC Structure.

      1. STOREY DISPLACEMENT

        The table shows the displacement in millimeters of the RC beam structure

        Storey

        Displacement of RC beam structure

        Height ( m )

        In x direction

        In y direction

        Base

        -1.5

        0

        0

        Plinth

        0

        1.337795

        1.487328

        1

        3

        4.605928

        4.442368

        2

        6

        6.637458

        7.3314

        3

        9

        9.913958

        10.117105

        4

        12

        11.647104

        12.765945

        5

        15

        13.978523

        15.263394

        6

        18

        16.176295

        17.600877

        7

        21

        18.231488

        19.773151

        8

        24

        20.135026

        21.774331

        9

        27

        21.875145

        23.594667

        10

        30

        23.435688

        25.218349

        11

        33

        24.795504

        26.622849

        12

        36

        25.929596

        27.780287

        13

        39

        26.811969

        28.663016

        14

        42

        27.448449

        29.273486

        Table 2 : displacement of RC beam

        From the table 2 its clear that the storey displacement of the RCC beam is directly propotional to storey height

        The maximum storey displacement is on the 14thstorey which is about 29.273486mm and the base has the minimum storey displacement that is zero

        The table shows the displacement in millimeters of the RC beam structure

        Table 3 : displacement of PT beam

        Storey

        Displacement of PT beam structure

        Height ( m )

        In x direction

        In y direction

        Base

        -1.5

        0

        0

        Plinth

        0

        1.136999

        1.166398

        1

        3

        3.356479

        3.468163

        2

        6

        5.61036

        5.779558

        3

        9

        7.86245

        8.071045

        4

        12

        10.08071

        10.314047

        5

        15

        12.239035

        12.485023

        6

        18

        14.315505

        14.564106

        7

        21

        16.290746

        16.533508

        8

        24

        18.146439

        18.377168

        9

        27

        19.864203

        20.077315

        10

        30

        21.424906

        21.614333

        11

        33

        22.808502

        22.968241

        12

        36

        23.994723

        24.118292

        13

        39

        24.965782

        25.046208

        14

        42

        25.738801

        25.747219

        The maximum storey displacement is on the 14thstorey which is about 25.747219mm and the base has the minimum storey displacement that is zero

        From the result above we can conclude that the PT beam has the lower displacement than the RCC beam about 12.04 %

      2. STOREY DRIFT

        Storey drift is the displacement occurred laterally in a floor with respect to the floor lying below .

        Storey drift ratio= storey Drift/storey height

        Fig 20 :: Drift of RC beam in x direction

        The storey drift of the RC beam structure is shown in the figure. The maximum drift in x and y direction is 0.000892 and 0.00992. The maximum drift is acting between the base and first storey. The maximum drift is 0.000992 and the minimum is zero at the base

        Fig 21 :: : Drift of PT beam in x direction

        The storey drift of the PT beam structure is shown in the figure. The maximum drift in x and y direction is 0.000758 and 0.000778. The maximum drift is acting between the base and first storey. The maximum drift is 0.000778 and the minimum is zero at the base. From the result above we can conclude that the PT beam has the lower drift than the RCC beam about

        21.57 %

      3. STOREY STIFFNESS

The value of force required to displace building to a certain amount is called stiffness. the greater the stiffness, the greater it can resist the deformations by earthquake because stiffness limits the building deformation demand. stiffness depends upon forces and deformations

Fig 22 :: Stiffness of RC beam in x direction

The storey stiffness of the RC beam structure is given in the figure. The stiffness is maximum between base and storey 1. The maximum stiffness is about 555385 KN/m which is in x direction and in y direction it is about 460116 KN/m

Fig 23 :: Stiffness of PT beam in x direction

The storey stiffness of the PT beam structure is given in the figure. The stiffness is maximum between base and storey 1. The maximum stiffness is about 1249505 KN/m which is in x direction and in y direction it is about 1205524 KN/m

EFFECT OF BRACINGS ON DISPLACEMENT

Effect of X bracings on PT beam

Fig 24 :displacement in Y direction

Maximum displacement is 15.562856mm which is in y direction and is lower than the PT beam structure without bracings

Effect of V bracings on PT beam

Fig 25 : displacement in Y directon

maximum displacement is 16.150414mm which is in y direction and is lower than the PT beam structure without bracings

Effect of inverted V bracings on PT beam

Fig 26 : displacement in Y directon

maximum displacement is 17.355338mm which is in y direction and is lower than the PT beam structure without bracings

From the above study it is clear that the PT beam structure with X bracings have least displacement when compared to V and inverted V bracings

  1. CONCLUSION

The following points are concluded from the study paper,

  • The modelling of the RC and PT beam is completed and is study under the seismic loading

  • The PT beam has the lower displacement than the RCC beam about 12.04 %

  • The PT beam has the lower drift than the RCC beam about

    21.57 %

  • The PT beam structure has the higher storey stiffness than the RCC beam structure

  • Three types of bracings are added to the PT beam structure and the effect on storey displacement is observed

  • PT beam structure with X bracings have least displacement when compared to V and inverted V bracings

VII. REFERENCES

[1] Shanmati Sridhar and A. leema rose (2019 ) performance evaluation of post tensioned concrete beams with bonded system (IJITEE) ISSN: 2278-3075, Volume-8 Issue-7 May, 2019

[2] Nighot (2020) Analysis and design of post tensioned slab using etab software International Journal of Innovative Science and Research

Technology ISSN No:-2456-2165 olume 5, Issue 11, November 2020

[3] Ramyasri. N and Rangarao. V (2017) Study on behaviour of prestressed concrete bridge with & without soil interaction. International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 1, January 2017, pp. 456463, Article ID:

IJCIET_08_01_053

[4] Reddy (2019) Comparative study on behaviour of deep beams. International Journal of Recent Technology and Engineering (IJRTE)

ISSN: 2277-3878, Volume-7, Issue-6C2, April 2019

[5] Boskey Vishal Bahoria and Dhananjay K. Parbat (2013) Analysis and design of RCC and post tensioned flat slab considering seismic effect. International Journal of Engineering and Technology, Vol. 5, No. 1,

February 2013

[6] Vamsikrishna (2021). Analysis and design of a commercial building with post tensioning slab by using etab. International Research Journal of Engineering and Technology (IRJET) Volume: 08 Issue: 06

[7] B.Anjaneyulu and K Jaya Prakash (2016) Analysis and design of flat slab using etab software. International journal of science engineering and advance technology IJSEAT, Vol. 4, Issue 2

[8] Vijay K More and Basavaraj Gudadappanavar (2022) Performance and Comparing RCC beam with Post Tension beam using Dynamic Load Condition of Larger Span Structure. (IJERT) ISSN: 2278-0181. Special Issue – 2022

[9] Ajinkya S. Dixit and V.G. Khurd, (2017) Nonlinear Flexural behavior of Post Tensioned Beam International Journal for Research in Applied Science & Engineering Technology (IJRASET), ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor:6.887, Volume 5 Issue X1

[10] Dawari, V. B and Vesmawala, G. R (2014) Application Of Nonlinear Concrete Model For Finite Element Analysis Of Reinforced Concrete Beam International Journal of Scientific & Engineering Research, Volume 5, Issue 9,

[11] G. Sri Harsha and P. Polu Raju (2019) Shear Strength of Deep Beams: A State of Art International Journal of Recent Technology and Engineering (IJRTE), ISSN: 2277-3878, Volume-7, Issue-6C2