Condition assessment of T-Post

for

xxxxxxxx

AT

Panipat, Haryana

Prepared By:-

O.B DEVELOPERS

(STRUCTURE AUDIT AGENCY)

Email- strutureauditagency@gmail.com

Call-+91-9717924616

www.structureauditagency.com

Content

S.No.	Description of NDT Reports	Page No.
1	Introduction & Scope of Work	3-5
2	Test Procedure	6-9
3	Test Results and Interpretation	10
	3.4	Rebound Hammer & Ultrasonic pulse velocity Test Results & Interpretation	11-13
Annexure 1                          Relevant Codes Marked Test location Testing Photograph

1. INTRODUCTION

1.1. Introduction

The structure, existing column is RCC column and steel frame .The xxxxx has requested to OB Developers for safety and appraisal of T-Post through conditions survey using Non-destructive testing. This report pertains to the stated safety appraisal, health assessment and quality of construction. In this report first the description of the damage portions of the building, objectives of the investigation and survey, general methodology and test procedures, etc. are given followed by details of the observations recorded at site and results of in-situ and laboratory tests.

1.2 Background of the Assignment:

RCC/Steel/Masonry structures as many other engineering structures are subjected to deterioration that affect their integrity, stability and safety. Faced with the importance of the stability of the structures, it is common practice to determine the causes of the deterioration if any exists so that structural adequacy can be analysed.

1.3. Objectives of the overall investigation

The overall objective of the investigation carried out for the structure is to obtain an up to date account of the health condition of the structure so that appropriate repair measures can be taken up to make up for the damages sustained. Keeping this in view the basic objectives of the investigation formulated are as given below.

1. To assess the existing condition of the structural elements.
2. To determine the extent of damages in the structure, so as to undertake suitable remedial measures for rehabilitation of the structure.

1.4 Scope of work and selection of tests

In-situ tests and laboratory tests have been selected based on the visual inspections carried out and as detailed in the scope of work. The selection of tests has been done so as to meet the overall objective of the NDT study are selected on the basis of the requirements of the overall objectives of the investigation and the observations made during a quick walk over survey. Various Test were Conducted for the evaluation of the Structure: 

The various Non-Destructive Tests carried out for health assessment and structural audit of the Composite Structure are given below:-

1. Ultrasonic Pulse Velocity Test as per IS: 13311 (Part-1)-1992 for ascertaining the quality of concrete, soundness and density of concrete. As per testing data the concrete is found in Good Range (4.04km/sec-4.09km/sec). There are no indications presence of air-pockets and voids in structure from USPV test results as per IS:13311 part 1
2. Rebound Hammer Test:  For determining the estimated compressive strength of concrete and uniformity of concrete in terms of surface hardness as per IS 13311 (Part-2)-1992. As per testing results the average rebound value is 31 concrete surfaces are  not suffering from surface hardness problem. There is also no indication of blistering of concrete surface as per IS 13311 (Part-2)-1992.

2. TEST PROCEDURES

2.1 ULTRASONIC PULSE VELOCITY:-

Purpose:-

Although there is no fundamental relationship between pulse velocity and strength, an estimation of strength can be obtained by correlation. The method has perhaps a greater potential for comparing known sound concrete with affected concrete.

Ultrasonic pulse velocity is a means of assessing variations in the apparent strength of concrete.

The quality gradation of concrete can be appraised at best qualitatively as `excellent’, `good’, `medium’ or `doubtful’. The meanings of the term `excellent’, `good’, `medium’ and `doubtful’ are based on ultrasonic pulse velocity measured at site and are as per the nomenclature of IS  13311(part-1): 1992. To strike balance between the reliability, speed and damage to structure, core test have to be used to establish a correlation between rebound number index and the estimated in-situ strength with the USPV test results in the investigation.

Objective of testing:-

Ultrasonic pulse velocity test is used to establish the following:

• Homogeneity of concrete
• Presence of cracks voids, honeycombing and other imperfections
• Changes in the structure of concrete which may occur with time.
• Quality of one element of concrete in relation to another i.e. comparative quality analysis and gradation of concrete.
• The values of dynamic elastic modulus of the concrete.

References:-

• BS 6089:1981 and BS 1881:Part203
• IS 13311:Part1:1992
• ASTM: C597-83.

Influencing factors:-

The velocity of a pulse of ultrasonic energy in concrete is influenced by the stiffness and mechanical strength of the concrete

• Moisture content: The moisture content of the concrete have a small effect in the velocity and can increase the pulse velocity by 2%.
• Surface condition: The testing surface should be smooth any roughness cannot provide reliable readings because of gap between transducers and testing surface.
• Temperature: Ideal Temperature is between 5⁰C and 30⁰C; Temperature between 30⁰C to 60⁰C can reduce the pulse velocity up to 5%; below freezing temperature results in an increase the pulse velocity up to 7.5%.
• Stress: When concrete is subjected to a stress which is abnormally high for a quality of concrete, the pulse velocity may be reduced due to development of micro-cracks.
• Reinforcing bars: The velocity measured in reinforced concrete in the vicinity of reinforcing bars is usually higher than in plain concrete because pulse velocity in steel is 1.2-1.9 times the velocity in plain concrete. Wherever possible, measurements should be made in such a way that steel does not lie in the path of the pulse.

Testing method:-

According to IS 13311(Part1):1992 clause 5.2 transducers with a frequency of 50 to 60 kHz are useful for most all round applications, and as per IS 13311(Part1):1992 clause 6.2 the path length should be long enough not to be significantly influenced by the heterogeneous nature of concrete. This test requires a flat surface generally only appropriate for unspalled surfaces.

In view of inherent variability in the test results, sufficient number of readings should be taken by dividing the entire structure in suitable grid of markings 30×30 cm or even smaller. Each junction point of the grid becomes a point of observation.

There are three possible methods of testing according to the type of surface:

                      Table Velocity Criterion for Concrete Quality Grading [Ref: IS13311 (part-1)]

Sr. No.	USPV by Cross Probing (km/sec)	Concrete Quality Grading.
1	Above 4.5	Excellent
2	3.5 – 4.5	Good
3	3.0 – 3.5	Medium
4	Below 3.0	* Doubtful

2.2 REBOUND HAMMER TEST:-

Purpose:-

This test gives a measure of the surface hardness of the concrete surface. Although there is no direct relationship between this measurement of surface hardness and strength, an empirical relationship exists.

Rebound hammer is the best known methods of comparing the concrete in different parts of a structure and indirectly assessing concrete strength. The rebound hammer should be considered as a means of assessing variations of strength within a structure rather than an accurate means of assessing the strength.

Objective of testing:-

Rebound hammer test is performed to determine the following:

• Surface hardness
• Uniformity of concrete over the structure
• Grade of concrete
• Estimated strength which is derived from establishing a relationship between in-situ core strength and rebound number.

References:-

• BS 6089:1981 and BS 1881:Part 202,
• IS13311(Part2):1992
• ASTM C 805-02

Influencing factors:-

Rebound hammer test results are considerably influenced by these factors:

• Size, shape and rigidity of the specimen
• Age of test specimen
• Smoothness of surface and internal moisture condition of the concrete
• Carbonation of concrete surface

Testing Method:-

According to ASTM C 805-02 clause 7.1 the concrete members to be tested shall be at least 100mm thick and fixed within a structure. Towelled surfaces generally exhibit high rebound numbers than screed or formed finishes. Do not compare the test results if the form material against which the concrete is placed is not similar.

Heavily textured, soft or surfaces with loose mortar shall be ground flat with abrasive stone. Smooth formed or towelled surfaces do not have to be ground prior to testing.

Also this test is not conducted directly over the reinforcing bars having cover less than 20mm. The surface under test should be clean and smooth because rough surfaces cannot be tested as they do not give reliable results. Dirt or other loose material on the surface can be removed using a grinding stone prior to test.

3. Test Results & InterpretatioN

3.4 REBOUND HAMMER Test:-

Test results analysis of the Rebound Number values is based on test results conducted over concrete surfaces. Obtained test results explain about pattern of concrete quality of whole structure sections in terms of surface hardness. So there is no indication of blistering of concrete surface as per IS 13311 (Part-2)-1992. Estimated strength of concrete calculated from rebound hammer number is based on correlation graph between core strength v/s corresponding rebound hammer values.  Rebound hammer has been carried out in all three directions horizontal, vertical down and vertical up. By using manufacturer graph, all vertical up/vertical down rebound hammer readings has been converted into the equivalent horizontal readings.Histogram plot of the Rebound Number values is based on test results conducted over concrete surfaces. Histogram plot explains about pattern of concrete quality of whole structure sections in terms of surface hardness. Rebound number helps to obtained Estimation of Strength of concrete from correlation between Rebound Hammer V/S Core Compressive strength. Estimated strength of concrete (obtained from correlation between Rebound Hammer V/S Core Compressive strength in table & fig ) is explained in the table

Figure

Reference for Test Certificate of Rebound hammer & Ultrasonic Pulse Velocity Test table

	For Rebound hammer Test
1	Sample Identification/Location	Location where test are conducted
2	Hammer Alignment	Direction of hammer
3	Rebound No.	Horizontal proportionate of rebound nos. from manufacturer calibration graph
4	Avg. Rebound No.	Rebound hammer no. obtained from instrument
5	Estimated Strength (MPa)	Correlation equation between RH and Core Value(ref equation figure 3.2)

Quality Assurance in Concrete using Non Destructive Testing
Client:-        xxxxxx		Consultant OB Developers
Non Destructive Testing at xxxxxxxx
S. No./Location	Rebound Hammer Test		Ultrasonic Pulse Velocity
SL. No.	Sample Identification/ Location	Hammer Alignment	Rebound No.	Avg. Rebound No.	Quality Of Concrete	Estimated Concrete Strength     N/mm2	Type of surface	Distance (mm)	Travel Time (micro sec.)	Av. Velocity (km/sec)	Direct Proportionate Velocity (IS, 5.4.1 13311 part 1)	Concrete Quality
Ground floor
1	Column	Horizontal	32	28	32	32	34	32	32	Good Layer	17.37	Direct	420	104.01	4.04	4.04	Good
2	Column	Horizontal	30	30	28	34	30	30	30	Good Layer	16.38
3	Column	Horizontal	36	28	30	32	28	34	31	Good Layer	17.12	Direct	420	102.69	4.09	4.09	Good
4	Column	Horizontal	30	30	34	30	32	30	31	Good Layer	16.87
Rebound Hammer(ASTM  C 805- 85):- Surface Hardness  indices value should be more than 28 to get correlation with estimated strength , uniformity of concrete
USPV(IS:13311 part 1):- Concrete Quality Grading(km/sec) Above 4.5 – Excellent, 3.5 – 4.5 – Good , 3.0 – 3.5-  Medium & Below 3.0-  Doubtful

1. Analysis of uniformity and imperviousness of concrete on the basis of USPV test results:- 

USPV makes possible an examination of material homogeneity. Analysing the ultrasonic velocity wave propagation variations, it is possible to verify the compact of the structure or detect heterogeneous regions. The ultrasonic test methodology in concrete is based on the fact that the propagation time expresses the density of the material. Histogram of USPV test results is analysed in same pattern as rebound hammer is done but basic difference is that USPV results are interrelated in terms of density and rebound hammer results are interrelated in terms of surface hardness. It has uniform concrete quality in terms of density. There are no indications of air-pockets and voids as significant from USPV test results as per IS:13311 part 1. Statistical data says that over all concrete has uniform grade of quality of density pattern.

As per testing data the concrete is found in Good Range (4.04km/sec-4.09km/sec). There are no indications presence of air-pockets and voids in structure from USPV test results as per IS:13311 part 1

• Interpretation of RCC Surface condition, uniformity of concrete and f_ck value of concrete obtained from Rebound hammer:-

Test results analysis of the Rebound Number values is based on test results conducted over concrete surfaces. Obtained test results explain about pattern of concrete quality of whole structure sections in terms of surface hardness.

As per testing results the average rebound value is 31 concrete surfaces are not suffering from surface hardness problem. There is also no indication of blistering of concrete surface as per IS 13311 (Part-2)-1992

ANNEXURE 1

Relevant Code:-

TEST MARK LOCATION

TESTING PHOTOGRAPH

Rebound Hammer Test

Ultra Sonic Pulse Velocity Test

STRUCTURAL DESIGN BASIS REPORT

PROJECT

xxxxxxxx

AT

xxxxx

Prepared By:-

O.B DEVELOPERS

(STRUCTURE AUDIT AGENCY)

Email- strutureauditagency@gmail.com

Call-+91-9717924616

www.structureauditagency.com

1. INTRODUCTION

The structure is a RCC and STEEL AT T-POST AT xxxxx . In this report the design data sheet is attached along with the factor that are taken in account while analysis and design of the structure.

1. VARIOUS CODE REFERED DURING ANALYSIS AND DESIGN

 (i) IS 456       

(ii) IS 800

2.  aNALYSIS AND DESIGN DATA

2.1Method of structural adequacy analysis and design parameters:-

The seismic safety of a multi-storeyed reinforced concrete building will depend upon the initial architectural and structural configuration of the total building, the quality of the Structural analysis, design and reinforcement detailing of the building frame to achieve stability of elements and their ductile performance under severe seismic lading. Proper quality of construction and stability of the infill walls and partitions are additional safety requirements of the structure as a whole. Any weakness left in the structure, whether in design or in construction will be fully revealed during the postulated maximum considered earthquake for the seismic zone in the earthquake code IBC 4830, BS 8110

Assumptions in static analysis

The basic assumptions in static analysis methodology are as follows:-

1. The behaviour of the structure is assumed to be perfectly linear and deformations are small
2. All joints are rigid
3. The members are subjected to axial, flexural and shear deformations
4. The force deformation relationship remains linear during the entire load regime.

Mathematical Modelling

The structure is idolized as a 3-D space frame model. The beams and columns are considered as members. The floor slab load is given on beam members. The brick wall is used as a filler wall and is not casted monolithically with structure; hence this load is also given on beam members. The columns are assumed to be fixed at the foundation level.

2.2Loads for Superstructure and Sub structural elements:

1. Grade of Concrete: M15
2. Steel: Fe500
3. Density of Concrete: 25kN/m³
4. Density of Steel: 78kN/m³
5. Human Load: 1.5kN
6. Impact: 4 kN/m2

2.3Materials properties data for static analysis: (as given in test certificates of reports; clause no 4.1)

1)         Concrete

a)         Concrete grade                                                :Grade of concrete: M20(1:1.5:3)

b)         Static modulus of elasticity E_c                        :           5000√f_ck

c)         Poisson’s ratio                                                 :           0.2

d)         Unit weight of R.C.C                         :                       25 kN/m³

e)         P.C.C                                                              :           nominal mix of 1:4:8

2)         Reinforcement Steel                                                              

            Yield strength F_y                                             :           460 N/mm²                             

            Conforming to IS 1786 -1985

            Static modulus of elasticity E_s                        :           2 x 10⁵ N/mm²

2.4 Load combinations

Combination of Loads considered in analysis: The structural design has been carried out in accordance with the provisions of the codes BS 8110 for Normal design conditions

1. 1.5DL+1.5LL
2. 1.5DL
3. 1.0DL+1.0LL

3. Structure Adequacy analysis in Staad Pro.

• Loading arrangement in frame structure

3D View

SUMMARY OF STRUCTURE & FOUNDATION DESIGN REPORT

S.No	Particular	Result
1	Steel T-Post	All the members are found to be safe
2	Foundation	Foundation size 1200mmx1200mm are suitable as per the T-Post Load
3	Anchor Bolts	8 nos M16 bolts are suitable for holding the T-Post. Hence safe

Reason for T-Post Over Turning

Since the design is found to be safe the only reason for the T-post over turning is a impact from the moving trucks.

Action Needed:-

1. The pedestal needs to be dismantled till the foundation top (1500mm below the existing top level).
   1. New Pedestal to be provided with reinforcement mentioned below

A bars are new bars, B bars are existing bars. A bars need to be chemical anchored in the foundation upto depth of 200mm using Hilti Re 500.

• There is a need to apply anti-corrosion paint on the existing bars since it is clear that the existing bars are suffering from corrosion.

• Anchor Bolts are need to be placed as per old design.
  • The gap between the base plate and concrete surface need to be filled with grouting.