Strength Evaluation of Fire Affected Hospital Building by using Non Destructive Test

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Strength Evaluation of Fire Affected Hospital Building by using Non Destructive Test

Er. Skindar Bakht Shah

Research Scholar, Dept. of Civil Engineering.

Indo-global group of Colleges.

Abhipur, Mohali, India

Er. Manjit Kaur

Assistant Prof, Dept.of Civil Engineering Indo-global group of Colleges

Abhipur, Mohali. India

Abstract:- Concrete is broadly utilized for the development of frameworks, for example, structures, spans, cooling towers, stacks, mechanical and other numerical structures. Fire is one of the most damaging incidental loads that a structure can be oppressed during its lifetime. The measure of harm caused will depend for the most part on the seriousness and the term.

The physical properties of concrete and the

reinforcement steel are altered by the temperature and range of fire. Recovery of flame harmed structures are typically favored than destroying and remaking. Assessment of fire damaged concrete usually starts with visual observation followed by Non destructive tests Rebound hammer test, ultrasonic pulse velocity test, Carbonation Test. The Rebound hammer and ultrasonic pulse velocity measurements made on a structure will provide a qualitative estimation of the damaged members with the undamaged one. This paper outlines a methodology for assessing the condition of a fire damaged concrete structure based on non-destructive; the observations of the fire affected hospital building were taken and then compare with fire un-affected portion of the hospital building.

Key words: Fire damaged, Rebound hammer, Ultrasonic pulse velocity, Rehabilitation

  1. INTRODUCTION

    The purpose of using Non destructive tests is to determine the quality and integrity of materials, components or assemblies without affecting the ability to perform their intended functions. This paper deals with the change in properties of a fire affected concrete. Now days there are incidents of fires in buildings are often heard which are increasing day by day and also the repair and rehabilitation of fire damaged structures has become an area for study and research. Many efforts are been laid down to carry out research in these related fields. To build a structure usable again after fire damage is a discipline of great concern by civil engineering community. Concrete is known to exhibit a good behavior at high temperature, and the concrete is incombustible in Nature. Generally concrete having low thermal conductivity, which guarantee a slow propagation of thermal transients within the structural members. It was confirmed from the fire affected hospital building caused due to gas explosion located in Baramulla, Jammu and Kashmir that the physical and mechanical properties of concrete affected due to elevated temperature. A significant reduction in compressive strength, tensile strength has been found in the fire affected hospital building. Physical properties such as density, porosity, color and morphological properties were also remarkably affected.

    Hence there is a need of using Non destructive test techniques to evaluate the properties of fire affected hospital building.

    Key words: Non destructive test, compressive strength, tensile strength, porosity

  2. LITERATURE REVIEW

    Adam Levesque et al [2019] This research focuses on the effect of fire on structures due to the Boko Haram insurgency in Maiduguri, Northern Nigeria. It is aimed at giving a further contribution to understand the effect of fire with respect to the local aggregates, quenching methods and proposing an assessment methodology based on a suitable analytical procedure applied to reinforced concrete subjected to sustained fire. . The samples were burnt in a designed fire simulation furnace using sugarcane bags as fuel with varying air velocities for 2 hours. Cooling of samples was carried out using water splashing, CO2 powder fire extinguisher and air cooling methods before the compressive strength tests using a Seidner Compressive Testing Machine and Non-destructive test with Rebound Hammer. Kumavat H.R. et al. (2014) The paper present case study include the use of various Non- Destructive Test (NDT), to evaluate the concrete quality of building age was 8 years. Initially, the structure deteriorates due to cyclic temperature variations, physical causes and aggressive chemical attack the research paper also focus on standard testing procedure of NDT and sequence of operation for obtaining accuracy as well as the problems created during the testing and the limitations of the tests are considered. Said M. Allam, Hazem M.F and Elbakry Alaa G. Rabeai [2013] has investigated The behavior of reinforced concrete slabs under fire loading has been studied by researchers for many decades . It is well known that when the temperature increases the slab fire resistance decreases. This is because when concrete is exposed to heat, chemical and physical reactions occur such as loss of moisture, dehydration of cement paste and decomposition of the aggregate. Such changes lead to high pore pressures caused by the water evaporation, internal micro cracks and damages appear in concrete Also, the increase in the temperature leads to a decrease in the yield strength of the steel reinforcement. Concrete spelling under high temperatures is a major factor of reducing its fire resistance. The spelling is caused by the build-up of pore pressure during heating. F Ali, A Nadjai, A Abu-Tair [2011] has investigated the Explosive spalling of high

    performance concrete under fire is one of the major concerns in front of the engineering community today. It is associated with violent failure of thin layers of concrete resulting in sudden reduction of load carrying capacity which may lead to complete collapse. High pore pressures due to low permeability and stresses due to thermal gradients are considered to be the governing causes of explosive spalling. However, the failure mechanisms and all influencing parameters are not yet fully understood. The most popular method to prevent spalling is the addition of polypropylene (PP) fibers in concrete. It is generally accepted that the PP fibers leave a porous network after melting at around 160 °C, leading to an increase in permeability, thus allowing the water vapors to escape. Mohammad Reza Hamadan et al.(2009) In this research paper authors used Rebound hammer test and Ultrasonic pulse velocity test on specimen and existing structure and got compressive strength of concrete and comparison along with actual compressive strength which is obtain from compressive testing machine. The structural health monitoring by NDT methods comprised of UPV and RSH (Schmidt Rebound Hammer) were carried out in laboratory and site. The experimental investigation using NDT methods showed that a good correlation exists between compressive strength, SRH and UPV. Ian A.FLETCHER, Stephen WELCH, José L. TORERO, Richard O. CARVEL, Asif USMANI [ 2007] has investigated the performance of steel during a fire is understood to a higher degree than the performance of concrete, and the strength of steel at a given temperature can be predicted with reasonable confidence. It is generally held that steel reinforcement bars need to be protected from exposure to temperatures in excess of 250-300°C. This is due to the fact that steels with low C-contents are known to exhibit blue brittleness between 200 and 300°C. Concrete and steel exhibit similar thermal expansion at temperatures up to 400°C; however, higher temperatures will result in significant expansion of the steel compared to the concrete and, if temperatures of the order of 700°C are attained, the load-bearing capacity of th steel reinforcement will be reduced to about 20% of its design value. M.Z. Mohamed Firdows et al (2005) 34-year old industrial building was investigated to assess the extent of damage and the cause(s) of deterioration. This study involved visual inspection, non-destructive testing, and laboratory analysis for materials collected from the building. Besides rebound hammer and ultrasonic pulse velocity tests, cores were also extracted from select locations and a detailed analysis of the hardened concrete was carried out. Half-cell potential and concrete resistivity measurements were also conducted. The results of the testing and analysis indicated that the structural members were affected due to chlorine gas emission and carbonation. This paper describes details of the investigations carried out, evaluation of test results and recommendations on measures for strengthening the building. N.R. Short, J.A. Purkiss, et al [2001] this paper deals with Assessment of fire damaged concrete structures usually starts with visual observation of color change, cracking and spalling. On heating, a change in color from normal to a pink/red is often observed and this is useful

    since it coincides with the onset of significant loss of concrete strength. . The full development of the pink/red color is coincident with substantial reduction in compressive strength and the method may be used to define the distance from a heated surface where strength degradation has occurred. J.K Chege et al (2000) this paper deals with a bomb blast affected building suffered extensive damage to structural elements and other areas of a building. Major and crucial information necessary in the evaluation included the mapping of the extent of damage which calls for both visual examination and extensive use of Non Destructive Testing Equipment and skilled personnel capable of checking for cracks, materials damage, and reinforcement bars condition including location sizing and strength measurement of critical structures elements.

  3. OBJECTIVE OF THE STUDY

    • To Investigate the Rebound hammer measurements on fire un-affected concrete and compare with the values of fire affected concrete

    • To Investigate The Compressive Strength with the help of Rebound Hammer on fire un-affected concrete and compare with fire affected concrete

    • To Investigate the Ultrasonic Pulse Velocity (UPV) measurements on fire un-affected concrete and compare with the values of fire affected concrete.

    • To Investigate Any Discontinuity in cross section of structure like cracks, cover concrete delaminating.

    • To investigate the carbonation effect on fire affected and fire UN affected .concrete then compare with the obtained results.

    • To investigate the carbonation depth of the concrete cover over the reinforcement

  4. METHODOLOGY

    A precise methodology for completing a logical examination of a flame influenced in hospital building and the influenced in hospital building and the parameters that are to be assessed from these tests are displayed.

    The review depends on the

    1. Visual Inspection (Photographic Inspection).

        • Source of fire and its location in the building

        • Locations of portions with extensive, moderate and no-damage.

        • Color of concrete.

        • Spalling of concrete, horizontal and vertical cracks in concrete.

        • Damage of structural steel sections and their locations Inspection over damaged portions

    2. Conditional Survey.

      The motivation behind the overview is to gather adequate information to pinpoint the reason and wellspring of the issue and to decide the degree of the harm. Contingent

      upon the reasonable justification of the harm, the site work includes a mix of the accompanying procedures:

        • Detailed visual inspection;

        • Survey of cracks, spalling, concrete degradation etc.

        • Drilling holes or mini-cores for carbonation test

        • Coring of concrete for determination of strength and petrography examination;

        • Rebound hammer test for compressive strength (comparison only);

        • Ultrasonic pulse velocity test for honeycombing depth of cracks, or compressive strength (comparison only).

    3. Non-Destructive Testing.

    These tests are based on indirect measurement of concrete strength through measurement of surface hardness and dynamic modulus of elasticity. Calibration curves relating these properties to the strength of concrete are available. The most commonly adopted NDT methods for assessment of the strength of concrete and their principles are given in the following

    Rebound Hammer: – Spring-driven mass strikes the surface of concrete and rebound distance is given in R- values. Surface hardness is measured and strength estimated from calibration curves, keeping in mind the limitations.

    Ultrasonic Pulse Velocity: – It operates on the principle that stress wave propagation velocity is affected by the quality of concrete. Pulse waves are induced in materials and the time of arrival measured at the receiving surface.

    Carbonation Test: – Carbonation occurs when CO2 from air finds its way into the body of concrete through its pores in presence of moisture & water forms carbonic acid which neutralizes the Ca (OH) 2 formed due to their action during setting of concrete thus reducing the alkalinity of concrete

    Table 1: Relation between Rebound No and Concrete Quality

    AVERAGE REBOUND

    QUALITY OF CONCRETE

    >40

    30-40

    20-30

    <20

    0

    Very Good Good

    Fair

    Poor and/or delaminated Very Poor and/or delaminated

    Table 2: Relation of Pulse velocity with Quality of concrete

    PULSE VELOCITY (KM/SEC.)

    QUALITY OF CONCRETE

    0-2

    2-2.5

    2.5-3

    3-4

    POOR DOUBTFUL MEDIUM

    GOOD

    Picture 1 (Spalling of Concrete)

    S.No

    Specification

    Data

    1

    Building

    Hospital

    2

    Location

    Baramulla Jammu and Kashmir

    3

    Fire accident

    31 July 2015

    4

    Floors

    3

    5

    Height of building

    11 m

    6

    Grade of Concrete

    M 25

    7

    Grade of steel

    Fe 415

    S.No

    Specification

    Data

    1

    Building

    Hospital

    2

    Location

    Baramulla Jammu and Kashmir

    3

    Fire accident

    31 July 2015

    4

    Floors

    3

    5

    Height of building

    11 m

    6

    Grade of Concrete

    M 25

    7

    Grade of steel

    Fe 415

  5. RESULT AND DISCUSSION Table: 3 Specifications of the building

    REBOUND HAMMER TEST

    Table: 4 Ground Floor Fire Affected Portion.

    C No.

    Reading

    R No.

    Compressive Strength(N/mm2)

    Quality

    1

    2

    3

    4

    5

    6

    C1

    20

    30

    35

    34

    32

    33

    30

    24

    Fair

    C4

    29

    31

    27

    30

    28

    26

    29

    23

    Fair

    C7

    31

    25

    30

    26

    29

    30

    28

    22

    Fair

    C13

    29

    28

    26

    25

    28

    27

    27

    20

    Fair

    C7

    25

    23

    25

    26

    22

    28

    25

    18

    Delaminated

    B1

    30

    32

    31

    25

    24

    29

    28

    23

    Fair

    C8

    25

    32

    25

    32

    33

    28

    30

    24

    Fair

    Table: 5 First and second Floor Fire Un Affected Portion.

    C No.

    Reading

    R No.

    Compressive Strength(N/mm2)

    Quality

    1

    2

    3

    4

    5

    6

    C6

    33

    31

    25

    39

    35

    25

    31

    25

    Good

    C14

    50

    35

    20

    32

    29

    27

    32

    26

    Good

    C5

    33

    31

    33

    27

    33

    30

    32

    26

    Good

    B8

    33

    31

    29

    31

    33

    29

    30

    24

    Fair

    B9

    30

    35

    29

    36

    30

    28

    31

    25

    Good

    SECOND FLOOR

    C6

    35

    33

    30

    35

    32

    33

    33

    28

    Good

    C7

    35

    30

    38

    35

    30

    35

    34

    30

    Good

    C8

    30

    30

    39

    30

    38

    30

    32

    26

    Good

    C9

    30

    30

    30

    35

    38

    38

    33

    28

    Good

    C5

    33

    35

    32

    30

    38

    32

    33

    28

    Good

    C3

    31

    34

    33

    35

    38

    34

    34

    30

    Good

    C2

    39

    32

    32

    35

    31

    35

    34

    30

    Good

    30

    25

    20

    15

    30

    25

    20

    15

    compressi

    ve strenth

    compressi

    ve strenth

    10

    5

    0

    10

    5

    0

    30 29 28 27 25 28 30

    30 29 28 27 25 28 30

    31

    30

    29

    28

    27

    26

    25

    24

    31

    30

    29

    28

    27

    26

    25

    24

    compressi

    ve

    strength

    compressi

    ve

    strength

    33 34 32 33 34

    33 34 32 33 34

    Fig: 1 Graph between compressive strength and rebound number of Fire affected portion.

    Fig: 2 Graph between compressive strength and rebound number of Fire un-affected portion

    Ultrasonic pulse Velocity Test

    Table: 6 Ground Floor Fire Affected Portion

    C No.

    Distance (Metre)

    Time

    Velocity

    Time

    Velocity

    Average Velocity

    Method

    Quality

    I

    I

    II

    II

    C4

    0.381

    180

    2.116

    170

    2.241

    2.178

    Direct

    DOUBTFUL

    C10

    0.381

    177

    2.152

    180

    2.116

    2.134

    Direct

    DOUBTFUL

    C11

    0.381

    180

    2.116

    175

    2.177

    2.146

    Direct

    DOUBTFUL

    C12

    0.381

    151

    2.523

    160

    2.381

    2.452

    Direct

    DOUBTFUL

    C13

    0.381

    180

    2.116

    171

    2.228

    2.172

    Direct

    DOUBTFUL

    C14

    0.381

    177

    2.152

    185

    2.059

    2.105

    Direct

    DOUBTFUL

    B1

    0.381

    180

    2.116

    172

    2.215

    2.165

    Direct

    DOUBTFUL

    C6

    0.178

    80

    2.225

    76

    2.342

    2.283

    Indirect

    DOUBTFUL

    C7

    0.178

    75

    2.373

    71

    2.507

    2.440

    Indirect

    DOUBTFUL

    C5

    0.178

    75

    2.373

    78

    2.282

    2.327

    Indirect

    DOUBTFUL

    Table: 7 First and second Floor Fire UN Affected Portion.

    C No.

    Distance (Metre)

    Time

    Velocity

    Time

    Velocity

    Average Velocity

    Method

    Quality

    I

    I

    II

    II

    C8

    0.381

    175

    2.177

    182

    2.093

    2.135

    Direct

    DOUBTFUL

    C7

    0.381

    182

    2.093

    170

    2.241

    2.167

    Direct

    DOUBTFUL

    C6

    0.381

    170

    2.241

    177

    2.152

    2.196

    Direct

    DOUBTFUL

    C3

    0.381

    174

    2.196

    171

    2.228

    2.212

    Direct

    DOUBTFUL

    C5

    0.178

    71

    2.570

    80

    2.225

    2.397

    Indirect

    DOUBTFUL

    C13

    0.178

    73

    2.488

    75

    2.373

    2.410

    Indirect

    DOUBTFUL

    C12

    0.178

    75

    2.373

    75

    2.373

    2.373

    Indirect

    DOUBTFUL

    C11

    0.178

    77

    2.351

    71

    2.570

    2.460

    Indirect

    DOUBTFUL

    C10

    0.178

    80

    2.225

    71

    2.570

    2.397

    Indirect

    DOUBTFUL

    C9

    0.178

    75

    2.373

    77

    2.351

    2.362

    Indirect

    DOUBTFUL

    SECOND FLOOR

    C7

    0.381

    120

    3.175

    113

    3.371

    3.273

    Direct

    Good

    C12

    0.178

    65

    2.740

    61

    2.940

    2.840

    Indirect

    MEDIUM

    C11

    0.178

    60

    2.960

    65

    2.740

    2.850

    Indirect

    MEDIUM

    C10

    0.178

    61

    2.940

    62

    2.870

    2.905

    Indirect

    MEDIUM

    C9

    0.178

    74

    2.450

    69

    2.580

    2.515

    Indirect

    MEDIUM

    C8

    0.381

    120

    3.175

    113

    3.392

    3.30

    Direct

    GOOD

    C6

    0.178

    72

    2.455

    65

    2.740

    2.597

    Indirect

    MEDIUM

    C4

    0.178

    65

    2.740

    61

    2.940

    2.840

    Indirect

    MEDIUM

    B8

    0.178

    60

    2.960

    62

    2.870

    2.915

    Indirect

    MEDIUM

    The building is essentially a three storied framed structure having columns and beams running in perpendicular directions and is covered by R.C.C. slab. The fire has occurred mainly in the Ground floor of the building , so readings obtained from the rebound hammer test in fire affected portion of the building are not satisfactory as compared with Readings obtained from the rebound hammer test on second floor of the building are satisfactory as the concrete used in building is of M25 grade.

    Based on the UPV values, the members may be classified as:

    1. Unaffected – members with hair cracks and UPV values greater than 3.5 km/sec

    2. Moderately affected- members with wide cracks and UPV values between 2.5 and 3.5km/s

    3. Fairly affected – members with major cracks, spalling of concrete, and UPV values

      Below 2.5 km/sec

    4. Severely affected – major cracks, spalling of concrete, exposure and de-bonding of Reinforcement and finally the load carrying capacity can be

      calculated based on the Parameters evaluated using the various test results.

      3.5

      3

      2.5

      2

      fire affected

      3.5

      3

      2.5

      2

      fire affected

      1.5

      1

      fire un

      affected

      1.5

      1

      fire un

      affected

      0.5

      0

      0.5

      0

      Fig: 3 Graph between pulse velocity (km/s) and Quality of concrete for fire affected and un-affected.

  6. CONCLUSION AND FUTURE SCOPE

      1. The duration of fire in the room is of one hour and the estimated temperature is of the order of 300- 500ºC.

      2. The Ground Floor of the building is majorly affected by the fire and heat. Because of high temperature, the concrete cover is spalling out of the main members.

      3. Rebound hammer shows higher compressive strength in fire un affected portions than of fire affected portions.

      4. The effect of fire is clearly observed in UPV values i.e., the UPV readings of Un affected portion is higher than the affected portion.

      5. The Core was also extracted from one of the front columns up to 250mm depth, which shows the concrete is affected up to the cover level.

      6. The pH of concrete is decreased to 9 at Ground floor.

  7. RECOMMENDATIONS

    1. By using these results we can modify the properties of hospital buildings.

    2. To increase the compressive strength of fire affected buildings Concrete Jacketing has been used to increase the capacity of existing structures by placing cage around the beams and columns

    3. Grouting technique can be used on inclined and vertical cracks on walls, columns and beams.

    4. Epoxies and Epoxy Systems including Epoxy Concretes are used as repairing materials.

    5. Keim mineral paints preferred to protect from carbonation.

  8. REFERENCES

  1. Adam Levesque et al [2019] effect of fire on structures due to the Boko Haram insurgency in Maiduguri, Northern Nigeria American journal of civil Engineering and Architecture .2019,Vol 7 10.12691/ajcea-7-1-1.

  2. Kumavat H.R. et al. [2014] The concrete evaluation is necessary for the proper diagnosis of successful rehabilitation work International Journal of Research in Engineering and Technology EISSN: 2319-1163.

  3. Said M. Allam, Hazem M.F and Elbakry Alaa G. Rabeai [2013] behavior of reinforced concrete slabs under fire loading has been studied by researchers for many decades International Journal for Innovative Research in Science & Technology| ISSN (online): 2349-6010.

  4. F Ali, A Nadjai, A Abu-Tair [2011] explosive spalling of normal strength reinforced concrete slabs subjected to conventional fire F Ali, A Nadjai, A Abu-Tair – Materials and structures.

  5. Mohammad Reza Hamadan et al.(2009) Rebound hammer test and UPV on specimen and existing structure and got compressive strength of concrete and comparison along with actual compressive strength which is obtain from compressive testing machine. International Journal of Research in Engineering and Technology.

  6. Ian A.FLETCHER, Stephen WELCH, José L. TORERO, Richard O. CARVEL, Asif USMANI [ 2007] steel during a fire is understood to a higher degree than the performance of concrete, and the strength of steel at a given temperature can be predicted

    with reasonable confidence Directory of Open Access Journals , pp. 37-52(16).

  7. M.Z. Mohamed Firdows, A. Chellapan, J. Prabhakar and P. Srinivasan[2005],assessing the quality of in-situ concrete in the turbo generator foundation using UPV measurements, The Indian concrete journal, Feb 2005.

  8. N.R. Short U, J.A. Purkiss, et al [2001] Assessment of fire damaged concrete structures usually starts with visual observation of color change, cracking and spalling. Magazine of Concrete Research, Volume 54

  9. J.K Chege, NDT Application in Structural Integrity Evaluation of Bomb Blast Affected Buildings, 15th WCNDT-Roma, Apr 2000.

  10. IS 13311: 1992 (Part 1), Indian Standard Non-Destructive testing of Concrete-Methods of Test, Part 1-Ultrasonic Pulse Velocity.

  11. IS 13311: 1992 (Part 2), Indian Standard Non-Destructive testing of Concrete-Methods of Test, Part 2-Rebound Hammer

  12. BS 6089: 1981, Guide to Assessment of concrete strength in existing structures.

  13. BS 1881 Part 201:1986, British Standard Testing Concrete, Part 201-Guide to the use of Non-Destructive Methods of Test for Hardened Concrete.

  14. BS 1881 Part 202:1986, British Standard Testing Concrete, Part 202 Recommendations for Surface Hardness Testing by Rebound Hammer.

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