1
Date of Test: 4th – 5th June, 2020
Client: Karen Roses Joint Body
Structural Investigation Report for the Burnt One Storey Building
On Block/ Plot No 2/38 Nakuru/ Eldama-Ravine Highway
2
3
Table of Contents
Executive Summary 4
1.0 Introduction 10
1.1 Study Objective 11
1.2 Methodology 11
2.0 Tests and Assessments 12
2.1 Visual Inspection of the Structure 12
2.2 Schmidt hammer test 17
2.2.1 Schmidt Hammer Test results 18 2.3 Ultrasonic Pulse Velocity Test 21
2.3.1 Ultrasonic Pulse Velocity Test Results 23
2.3.1.1 Direct test results 23
2.3.1.2 Indirect test results 26
2.4 Carbonation test 35
2.4.1 Visual Assessments of Concrete Cores for Carbonation test 36 2.4.2 Carbonation test results 38
2.5 Compressive Strength Test 40
2.5.1 Visual Assessments of Concrete Cores for compressive strength 41
2.5.2 Core Compressive Strength Test Results 43
2.6 Electromagnetic Ferroscan Test. 45
2.6.1 Electromagnetic Ferroscan Test Results 46 3.0 Conclusions and Recommendations 56
3.1 Schmidt hammers test results 56
3.2 Ultrasonic Pulse Velocity Test 56
3.3 Core compressive strength test results 56
3.4 Carbonation test results 57
3.5 Reinforcement Details 57
3.6 General conclusions 58
3.7 Recommendations 58
4.0 Appendices 66
4.1 Layout Plan 66
4.2 Photographs 68
4.2 References 75
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Executive Summary
i. Leeds Engineering Company Limited (L.E.C.L) was commissioned by the client to
carry out a detailed structural integrity audit for a Burnt one story building in Eldama
Ravine. This was necessitated after a fire incident on the building
ii. The structure under investigation has one suspended reinforced concrete slab plus
ground floor level. The structural frame of the building is comprised of reinforced
concrete slabs, typical reinforced concrete beams (450x200mm) and typical reinforced
concrete columns (200x200mm).
iii. Based on our visual inspections on the structure, it is evident that the structural
elements supporting the structure have been affected by the fire. The following
conditions were observed:
a) At the ground floor level, only the area between grid lines 1/5-A/D was affected
by the fire incident whereas at the first floor level the entire structure was
affected.
b) Cracks had developed on some of the walls in the first floor.
c) Plaster on some structural elements had completely de-bonded and peeled off;
the most affected areas are the sports bar and entire first floor.
d) Concrete had flaked off from some columns and beams an indication that fire
exposure has affected the integrity of concrete.
e) Most of the non-structural fittings such as non-load bearing walls, partitions, wall
linings, ceilings, windows, glazing, roofing, doors, tiles, timber floor, movable and
fixed furniture had been completely destroyed by the fire.
f) All elements above first floor level have been completely destroyed by the fire.
g) There were no major effects noted on external walls.
iv. Results obtained from Schmidt hammer test regime confirm that concrete on structural
members achieved an average compressive strength of 15 N/mm². This is below the
nominal concrete strength of C20 for that nature of a structure; an indication that the
concrete strength has been affected by the fire exposure.
v. Ultrasonic pulse velocity test was carried out on concrete elements to assess the
quality of concrete on these members. The test was also done on plastered elements
to assess whether the plaster has de-bonded.
5
vi. Direct Ultrasonic Pulse Velocity test results showed that the concrete on structural
elements was ranging from doubtful quality to good quality. This is an indication
that surface concrete on some of the affected elements has developed voids, cracks
and internal cavities due to fire exposure.
vii. Results for Indirect Ultrasonic Pulse Velocity test on concrete elements gave largely
non-homogeneous concrete and some fairly homogenous concrete matrix. This is
a further indication that surface concrete has developed voids, cracks and internal
cavities due to the fire exposure. Indirect Ultrasonic Pulse Velocity test results on
plastered elements also confirm that plaster has de-bonded on most of the elements.
viii. Concrete strength assessed through Ultrasonic Pulse Velocity test gave an average of
16.9 N/mm². This is below the nominal concrete strength of C20 for that nature of a
structure; an indication that the concrete strength has been affected by the fire
exposure.
ix. Results obtained from core compressive strength tests confirm that concrete on
structural members achieved an average compressive strength of 15.4 N/mm2. This is
below the nominal concrete strength of C20 for that nature of a structure; an indication
that the concrete strength has been affected by the fire exposure.
x. Results obtained from carbonation test confirm that the carbonation depth was NIL for
some cores, and in the range of 15mm - 35mm for the other cores. Considering an
average concrete cover to reinforcement of around 25mm, the carbonation depth for
the affected elements is high. Thus, in general, carbonation front has reached the
vicinity of the surface of the Rebars for most of the affected elements. This increases
the risk of reinforcement corrosion in the elements thereby undermining their yield
strength.
xi. Consistencies of electromagnetic ferroscan results confirm that columns had 4No
12mm bars with 8mm links at a spacing of 200mm c/c.
xii. Beams were established to have 2No. 16mm bottom bars with 8mm links at a
spacing of 200mm c/c.
xiii. The slabs were established to have 10mm bars bottom 1 at a spacing of 200mm c/c
and 10mm bars bottom 2 at a spacing of 200mm.
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General conclusions
i. The concrete strength on structural elements is below the nominal concrete strength of
C20 for that nature of a structure. This gives an indication that the concrete strength
has been affected by the fire exposure
ii. Surface concrete has deteriorated as a result of fire exposure. It has developed voids,
cracks and internal cavities.
iii. Carbonation depth has reached the vicinity of the surface of the rebars. There is a high
risk of reinforcement corrosion considering that this is a time dependent process.
iv. Considering the low concrete strengths, it is our conclusion that the structural capacity
of the concrete members including first floor beams, first floor slab and ground floor
columns within grid lines 1/5-A/D has been compromised. As these members are still
intact, they can still be repaired and strengthened for them to achieve their full
structural potential.
v. The structural frame above the suspended slab is completely damaged and has been
weakened by the fire. This frame therefore cannot be salvaged.
Recommendations
Following the assessments carried out, the physical conditions observed and tests
carried out, the structure has been found to be adversely affected by the fire incident.
The load carrying capacity of the structural frame has therefore been undermined. It is
imperative that urgent corrective measures are undertaken on the damaged areas by
carrying out the following procedures;
i. Repair of all the concrete elements within the ground floor and first floor levels
that have developed surface defects by use of a structural repair mortar between
grid lines 1/5-A/D.
ii. To safeguard the existing ground floor columns, first floor slab and first floor
beams between grid lines 1/5-A/D against carbonation attack, we propose
demolition of columns and recasting with a suitable structural repair mortar before
containing them by use of carbon fibre wraps. The repair mortar shall be a mixture
of Master Flow 928 hydraulic cement-based mineral aggregate non-shrink grout
and 10mm aggregates to a ratio of 1:2. The first floor slab and first floor beams
shall be strengthened using epoxy bonded carbon fibre strips as specified below.
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iii. The existing reinforcement on ground floor columns, first floor beams and slab
that experienced the heat, were never checked for percentage (%) elongation
including tension, bending and re bending properties after the fire exposure. In
addition, we note that reinforcement in these elements may have been affected by
carbonation attack. It is therefore important we strengthen the these elements by
use of carbon fibre wraps and epoxy bonded carbon fibre strips as follows;
a) One (1) laminate plate of 50mm width should be fixed at the center of the
beam soffit covering the total length of the beam to increase flexural capacity
and one (1) shear strip should be fixed at either sides of the beam to
increase shear capacity.
b) Laminate plates of 50mm width should be fixed at the soffit of the first floor
slab in one direction at a spacing of 1500mm c/c to provide additional
flexural resistance.
c) Strengthening of ground floor columns between grid lines 1/5-A/D by
application of epoxy bonded unidirectional carbon fibre wrap placed around
the entire circumference of the columns.
iv. Demolishing and reconstruction of the entire structural frame above the first floor
slab.
v. Reconstruction of the entire roof structure.
vi. Redoing all non-structural elements such as non-load bearing walls, partitions,
wall linings, ceilings, flashings, windows, glazing, roofing, doors, tiles, movable
and fixed furniture
vii. Redoing all the electrical and mechanical services as detailed in the services
engineering report.
viii. All the structural repair work should be done under instructions and supervision of
a competent structural Engineer.
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Summary of Mechanical and Electrical Services
The table below gives a summary of the Mechanical and Electrical Services as
observed on site;
AREA OBSERVATIONS RECOMMENDATION
GF – Commercial
recreation centre
1. All electrical fitting and wiring
burnt, damaged beyond salvage.
1. Replace all electrical fitting
and wiring with new.
2. To reinstate fire alarm
detection devices and security
surveillance system
GF – ATS board
adjacent to staircase
1. The board not affected by
fire. The ATS and some
isolators observed intact
2. Some cut outs observed
disconnected.
1. To replace with an ATS
board that incorporates
latest switchgear that got
self-tripping mechanism in
case of a fault.
GF – KPLC meter
chamber
1. Observed in a standlone
chamber surrounded by
vegetation
2. 2. The chamber not accessible
and not secured by a padlock.
3. Cables poorly managed
4. Mounting height for the
switchgear too low against
working safely guidelines
5. Routing for cables from
transformer to metering chamber
to ATS board not traceable.
1. The meter chamber should
be easily accessible and
lockable.
2. Cables to be neatly
managed and labelled.
3. The mounting heights to
be raised to 1200mm
above finished floor level
4. Cable routing from the KPLC
transformer to metering
chamber to ATS board
should be in well-marked &
identifiable accessible ducts.
Ground floor – Diesel
powered Generator
1. 10kva 3phase diesel
powered generator observed
in a secure metal cage
behind the building.
2. Observed ok with no visible
effect of fire
3. Power and control cable
exposed on their entry to ATS
board at the staircase lobby
observed burnt.
1. Power and control cable from
Generator to ATS board to
be replaced with new.
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Ground floor –
External services
1. Some lights on the perimeter
column at the backside of the
plot observed burnt
2. The top most water tank
observed burnt on the side
3. The rear side rain water
gutters and drop pipes
observed burnt
1. Replace all the burnt items
with new
1st Floor – Staircase
lobby
1. The fitting on roof and wall all
burnt.
1.Replace all burnt fittings
1st Floor – Computer
room
1. All electrical fitting and wiring
burnt, damaged beyond
salvage.
2. 2no portable fire extinguisher
cylinders observed beyond
salvage
1. Replace all burnt fittings
2. Reinstate the fire detection
and extinguishing system in
this room as per building fire
code
1st Floor – Office
room(2no)
1. All electrical fitting and wiring
burnt, damaged beyond
salvage.
1. Replace all burnt fittings
2. Reinstate fire detection
& alarm system as per
building fire code
1st floor - Library 1. All electrical fitting and wiring
burnt, damaged beyond
salvage.
1. Replace all burnt fittings
2. Reinstate fire detection &
alarm system as per building
fire code
1st floor - WC 1. All electrical fitting and
wiring burnt, damaged
beyond salvage.
2. Sanitary fitting burnt
beyond salvage
3. Concealed plumbing pipe
work also observed burnt.
1. Replace all burnt fittings
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1.0 Introduction
Leeds Engineering Company Limited (L.E.C.L) was commissioned by the client to carry
out a detailed structural integrity audit for a Burnt one story building in Eldama Ravine.
This was necessitated after a fire incident on the building. The fire incident was severe
in some parts of the structure, as evident in that most items were burnt down and very
few were salvaged. Both structural and non-structural members were also adversely
affected by the fire incident and this warranted the structural investigations to determine
the structural integrity of the building.
The Structural investigations entailed carrying out an assessment of physical conditions
of the structure including assessment of the in-situ concrete strengths and its
consistency throughout the structural elements, reinforcement mapping on the structural
members of the building and assessment of extent of damage caused by the fire. The
data obtained thereof would then be used to establish the structural robustness, stability
and remedial measures necessary to restore its structural capacity.
A team from Leeds Engineering Co. Ltd. visited the above mentioned site on 4th – 5th
June 2020 to carry out structural investigations that entailed both non-destructive and
destructive tests. Non-destructive tests included Schmidt Hammer Test and Ultrasonic
Pulse Velocity Test on structural members and a detailed study of reinforcement
mapping by use of Electromagnetic Ferro Scan. The destructive tests included sampling
and extraction of four (4) number concrete cores from structural members for
carbonation test and compressive strength tests. The cores were well labeled and
information was gathered and recorded for each core based on the visual inspection
and measurements done on site. The results of the investigation into each of the tests
are followed by a summary of the findings enclosed herein.
This report has been prepared based on the results obtained from the tests mentioned
above. Any conclusions made at the end of this report are based on the results obtained
thereof and firm’s experience in execution of similar exercises.
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1.1 Study Objective
The main objective of this study was;
1. In situ materials assessment on the existing building structure which included
determination of the quality of concrete in the structural elements.
2. Reinforcement mapping to determine the actual size and number of rebars used
on site.
3. Carbonation tests on concrete core samples extracted on site.
4. Condition assessment of the structural elements with a view of modeling their
deterioration mechanism due to fire exposure.
5. Material analysis and risk assessment on the structural elements.
1.2 Methodology
The structural integrity assessment was carried out as follows:
i. Site visit(s) to carry out visual inspection to determine the condition of the
building and identify areas for testing.
ii. Carrying out a comprehensive material tests that included;
i. Non-destructive testing thus;
Schmidt Hammer test
Ultrasonic Pulse Velocity Test
Determination of reinforcement used on the structural
elements
II. Destructive testing that included;
Depth of carbonation test on concrete core samples
extracted on site.
Core compressive strength test
iii. Making conclusions based on the findings.
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2.0 Tests and Assessments
The following tests/inspections were carried out;
i) Condition assessment and Visual inspection of the building from an engineering
point of view.
ii) Schmidt Hammer Test to determine the quality and strength of concrete in
accordance with BS EN 12504:2-2012).
iii) Assessment of plaster debonding by Ultrasonic Pulse Velocity Analyzer in
accordance with BS EN 12504-4:2004
iv) Electromagnetic Ferro scan Test to determine reinforcement mapping in
accordance to BS 1881 – 204: 1988
v) Core extraction and crushing to determine the compressive strength of
concrete cores according to BS EN 12504-1:2009.
vi) Depth of Carbonation determination with accordance to BS 1881-210:2013 and
BS EN 14630:2006.
2.1 Visual Inspection of the Structure
The structure under investigation has one suspended reinforced concrete slab plus
ground floor level. The structural frame of the building is comprised of reinforced
concrete slabs, typical reinforced concrete beams (450x200mm) and typical reinforced
concrete columns (200x200mm).
Based on our visual inspections on the structure, it is evident that the structural
elements supporting the structure have been affected by the fire. The following
conditions were observed;
i. At the ground floor level, only the area between grid lines 1/5-A/D was affected
by the fire incident whereas at the first floor level the entire structure was
affected.
ii. Cracks had developed on some of the walls in the first floor.
iii. Plaster on some structural elements had completely de-bonded and peeled off;
the most affected areas are the sports bar and entire first floor.
iv. Concrete had flaked off from some columns and beams an indication that fire
exposure has affected the integrity of concrete.
13
v. Most of the non-structural fittings such as non-load bearing walls, partitions, wall
linings, ceilings, windows, glazing, roofing, doors, tiles, timber floor, movable and
fixed furniture had been completely destroyed by the fire.
vi. All elements above first floor level have been completely destroyed by the fire.
vii. There were no major effects noted on external walls.
Structural members identified for testing were selected randomly depending on
accessibility, functions and damage observed. Tests on the structural elements were
carried out as planned in the preamble to this report. Information generated from the
inspection and deductions made are contained in this report.
The photographic records below show the condition of the structure as noted during
these investigations.
Plate 1: Cracks on an a wall element
Crack on
an internal
wall
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Plate 2: Debonded plaster which has peeled off on a wall element
Plate 3: Completely burnt roof structure
15
Plate 4: Debonded and damaged floor tiles
Plate 5: Destroyed non-structural fittings
16
Plate 6: Section of the structure not affected by the fire
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2.2 Schmidt hammer test
The rebound (Schmidt) hammer is one of the oldest known methods of non-destructive
methods of determining concrete strength in different parts of a structure. The rebound
hammer is a means of assessing variations in strength within a structure. It is not
concise but gives an indication of acceptable concrete strength and if not acceptable,
then a destructive method is employed by cutting concrete core for crushing strength
testing in the laboratory
Apparatus:
The Schmidt Hammer test involves various apparatus namely:
1. Rebound Hammer – calibrated before commencement of the test
2. Abrasive stone – used to smoothen the surface before the test is conducted
3. Chisel and mason hammer – used in hacking and leveling the test surface
4. Reference anvil – used to check the correct functioning of the rebound hammer.
Sufficient test readings at each test location were taken. Care was taken to keep the
Rebound hammer perpendicular to the surface which is tested to specifications BS EN
12504-2:2012 in managing any error.
Plate 7: Schmidt hammer test in progress
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2.2.1 Schmidt Hammer Test results
19
Project:
Date:
Element Floor Level GridTest
Direction1 2 3 4 5 6 7 8 9 10 11 12
Average
Rebound
Value
Equivalent
Compressive
Strength(N/MM2)
Age of Concrete
Beam First Floor A/B - 1 Side 28 20 24 26 24 26 26 26 28 25 27 23 25 18 Over 28 days
Side 19 16 16 18 19 16 18 14 18 18 19 16 17 12 Over 28 days
Soffit 26 24 25 25 26 24 26 26 26 24 24 26 25 14 Over 28 days
Side 25 24 26 26 25 26 23 24 24 26 23 26 25 17 Over 28 days
Soffit 27 28 26 30 27 29 27 24 26 29 28 31 28 15 Over 28 days
Side 19 24 22 21 19 22 22 22 21 19 20 24 21 15 Over 28 days
Soffit 35 35 30 32 34 33 30 30 36 34 31 35 33 18 Over 28 days
Side 20 19 25 20 19 24 25 22 24 21 20 21 22 15 Over 28 days
Soffit 29 30 34 30 30 33 32 29 31 33 31 30 31 17 Over 28 days
Beam Roof 8 - B/C Soffit 26 27 30 25 29 24 26 24 26 26 29 24 26 14 Over 28 days
Beam Roof A/B - 5 Soffit 21 25 24 21 20 24 22 23 24 25 26 23 23 13 Over 28 days
N/B: Approximate Converted Strength(N/MM2)=Average Rebound x Correlation factor of 0.70 for horizontal orientation
and 0.55 for vertical orientation obtained from calibration of cube compressive strength.
Proper Surface preparation was done on site according to BS EN 12504-2:2012
Tested by:………………………………… Checked by:…………………………
Sign:…………………………………….
Date:………………………………………
Beam First Floor C/D - 4
Beam First Floor 5/6 - B
Beam First Floor 4/5 - C
STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT STRUCTURE IN ELDAMA RAVINE
04-06-20
Beam First Floor B - 4/5
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, KenyaParklands,Forest Road/Forest Court Mezzanine FloorOffice: +254 705186673/ +254 788316459Email: [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459 Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
20
Project:
Date:
Element Floor Level GridTest
Direction1 2 3 4 5 6 7 8 9 10 11 12
Average
Rebound
Value
Equivalent
Compressive
Strength(N/MM2)
Age of Concrete
Column Ground Floor 8 - C Side 20 16 19 18 19 16 16 17 16 17 16 17 17 12 Over 28 days
Column Ground Floor 4 - B Side 19 15 21 19 18 18 16 19 19 21 18 17 18 13 Over 28 days
Column First Floor 4 - D Side 20 22 24 26 23 26 24 24 22 24 24 26 24 17 Over 28 days
Column First Floor 5 - B Side 22 27 23 24 21 22 26 22 21 26 24 23 23 16 Over 28 days
Column First Floor 8" - D Side 24 26 26 22 23 28 24 25 27 24 26 27 25 18 Over 28 days
Slab First Floor 4/5 - A/B Soffit 27 27 23 24 27 26 23 29 26 24 25 27 26 14 Over 28 days
Slab First Floor C/D - 4/5 Soffit 27 29 31 30 33 29 34 32 31 34 29 32 31 17 Over 28 days
N/B: Approximate Converted Strength(N/MM2)=Average Rebound x Correlation factor of 0.70 for horizontal orientation
and 0.55 for vertical orientation obtained from calibration of cube compressive strength.
Proper Surface preparation was done on site according to BS EN 12504-2:2012
Tested by:………………………………… Checked by:…………………………
Sign:…………………………………….
Date:………………………………………
STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT STRUCTURE IN ELDAMA RAVINE
04-06-20
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, KenyaParklands,Forest Road/Forest Court Mezzanine FloorOffice: +254 705186673/ +254 788316459Email: [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
21
2.3 Ultrasonic Pulse Velocity Test
This test was carried out on structural elements with accordance to BS EN 12504-
4:2004 to determine the concrete quality and plaster De-bonding. The test
equipment has provisions for generating ultrasonic pulse, transmitting it to concrete,
receiving and amplifying the pulse and measuring and displaying the pulse travel
time. Good acoustic coupling between the transducers and concrete is established
for correct measurement of the speed.
Couplant is applied on the locations where the transducers are placed. Care is taken
not to move the transducers while reading is being taken, as this can generate noise
signals and errors in measurements. The transducers are held onto the surface of
the material until a consistent reading appears on the display. This is the time in
microsecond for the ultrasonic pulse to travel the test distance.
By this technique one can assess the quality of concrete such as presence of any
hollow sections, voids as well as cracks.
When an ultrasonic pulse travelling through concrete meets a concrete-air interface,
there is negligible transmission of energy across this interface. Thus, any air-filled
crack or void lying immediately between two transducers will obstruct the direct
ultrasonic beam when the projected length of the void is greater than the width of the
transducers and the wavelength of sound used. When this happens, the first pulse to
arrive at the receiving transducer will have been diffracted around the periphery of
the defect and the transit time will be longer than in similar concrete with no defect.
The following arrangements of the transducers were used during the tests to achieve
different test results:
a. Direct Transmission: - During this arrangement the transducers were placed
in opposite faces of the element.
b. Indirect Transmission: - During this arrangement the transducers were place
on the same face of the test area. This was mainly used where only one face
of the element sample area was accessible.
22
Plate 8: Ultrasonic pulse velocity test in progress
23
2.3.1 Ultrasonic Pulse Velocity Test Results
2.3.1.1 Direct test results
24
PROJECT:
DATE:
Element Floor Level GridTest
Location
Average
Transit Time
(µ Sec)
Average
Distance
(mm)
Transit
Velocity
(km/s)
Concrete Quality
(IS Code 13311 Part
1-1992) Table 2
Compressive
Strength
(N/MM2)
Column Ground Floor 4 - C Middle 182 334.00 2.20 Doubtful Quality 14.09
Column Ground Floor 4 - B Middle 134.2 318.00 2.84 Doubtful Quality 18.20
Column Ground Floor 5 - C Middle 45.2 141.42 3.75 Good Quality 24.03
Column Ground Floor 8 - C Middle 44.3 141.42 3.83 Good Quality 24.52
Column Ground Floor 9 - D Middle 46.6 141.42 3.64 Good Quality 23.31
Column First Floor 6 - B Middle 125.0 240.00 2.30 Doubtful Quality 14.75
Column First Floor 4" - D Middle 46.2 141.42 3.67 Good Quality 23.51
Column First Floor 8" - D Middle 96.3 141.42 1.76 Doubtful Quality 11.28
Checked by……………………………………..
LEGEND:
Signature…………………………………
N/B: Compressive Strength(N/MM2)= Corrected Transit Velocity (km/s) x Correlation factor of 6.4 obtained from
calibration of cube compressive strength.
Test
Regime
STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT STRUCTURE IN ELDAMA RAVINE
05-06--2020
DIRECT ULTRASONIC PULSE ANALYZER TEST (BS 12504-4:2004, IS 13311-1:1992)
Tested by:……………………………………………….
Date:……………………………………………………
Direct
Direct
Semi Direct
Semi Direct
Semi Direct
Direct
Semi Direct
Semi Direct
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, KenyaParklands,Forest Road/Forest Court Mezzanine FloorOffice: +254 705186673/ +254 788316459Email: [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
25
PROJECT:
DATE:
Element Floor Level GridTest
Location
Average
Transit Time
(µ Sec)
Average
Distance
(mm)
Transit
Velocity
(km/s)
Concrete Quality
(IS Code 13311 Part
1-1992) Table 2
Compressive
Strength
(N/MM2)
Beam First Floor 4/5 - C Midspan 119.2 240.00 2.42 Doubtful Quality 15.46
Beam First Floor 4/5 - B Midspan 101.5 255.00 3.01 Medium Quality 19.29
Beam First Floor C/D - 4 Midspan 155.2 270.00 2.09 Doubtful Quality 13.36
Beam First Floor 4 - A/B Midspan 116.3 141.42 1.46 Doubtful Quality 9.34
Beam First Floor 5/8 - C Midspan 89.1 250.00 3.37 Medium Quality 21.55
Beam First Floor 8/9 - C Midspan 82.4 240.00 3.50 Medium Quality 22.37
Beam First Floor 5/6 - B Midspan 35.6 141.42 4.77 Excellent 30.51
Beam Roof 8 - B/C Midspan 177.1 141.42 0.96 Doubtful Quality 6.13
Beam Roof 5/6 - B Midspan 324.7 270.00 1.00 Doubtful Quality 6.39
Beam Roof C/B - 4 Midspan 443.2 250.00 0.68 Doubtful Quality 4.33
Checked by……………………………………..
LEGEND:
Signature…………………………………
N/B: Compressive Strength(N/MM2)= Corrected Transit Velocity (km/s) x Correlation factor of 6.4 obtained from
calibration of cube compressive strength.
Semi Direct
STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT STRUCTURE IN ELDAMA RAVINE
05-06--2020
DIRECT ULTRASONIC PULSE ANALYZER TEST (BS 12504-4:2004, IS 13311-1:1992)
Test
Regime
Direct
Direct
Direct
Semi Direct
Direct
Direct
Semi Direct
Tested by:……………………………………………….
Date:……………………………………………………
Direct
Direct
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, KenyaParklands,Forest Road/Forest Court Mezzanine FloorOffice: +254 705186673/ +254 788316459Email: [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459 Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
26
2.3.1.2 Indirect test results
27
DATE:
ULTRASONIC PULSE ANALYZER TEST FOR SLAB (A/B-4/5) FIRST FLOOR
Distance (mm) Transit time(µsec)
50 53.2
100 72.4
150 124.0
200 160.1
250 180.1
Remarks: Non Homogeneous concrete matrix; plaster has debonded
Tested by:……………….. Checked by:…………………
Sign:……….……..…….
Date:……………………
PROJECT: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT
STRUCTURE IN ELDAMA RAVINE
05-06-20
y = 0.7676x
0.0
50.0
100.0
150.0
200.0
250.0
0 100 200 300
Tim
e (µ
sec)
Distance ( mm)
Homogeneity curve
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
28
DATE:
ULTRASONIC PULSE ANALYZER TEST FOR SLAB (C/D - 4/5) FIRST FLOOR
Distance (mm) Transit time(µsec)
50 22.9
100 42.1
150 71.2
200 105.2
250 135.4
Remarks: Fairly Homogeneous concrete matrix; plaster has debonded
Tested by:……………….. Checked by:…………………
Sign:……….……..…….
Date:……………………
PROJECT: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT
STRUCTURE IN ELDAMA RAVINE
05-06-20
y = 0.5158x
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
0 100 200 300
Tim
e (µ
sec)
Distance ( mm)
Homogeneity curve
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
29
DATE:
ULTRASONIC PULSE ANALYZER TEST FOR SLAB (B/C - 5/8) FIRST FLOOR
Distance (mm) Transit time(µsec)
50 25.3
100 44.7
150 66.9
200 84.7
250 99.2
Remarks: Fairly Homogeneous concrete matrix; plaster has debonded
Tested by:……………….. Checked by:…………………
Sign:……….……..…….
Date:……………………
PROJECT: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT
STRUCTURE IN ELDAMA RAVINE
05-06-20
y = 0.4183x
0.0
20.0
40.0
60.0
80.0
100.0
120.0
0 100 200 300
Tim
e (µ
sec)
Distance ( mm)
Homogeneity curve
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459 Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
30
DATE:
ULTRASONIC PULSE ANALYZER TEST FOR COLUMN (9-B) GROUND FLOOR
Distance (mm) Transit time(µsec)
50 23.6
100 48.5
150 66.3
200 106.8
250 125.7
Remarks: Non Homogeneous concrete matrix; plaster has debonded
Tested by:……………….. Checked by:…………………
Sign:……….……..…….
Date:……………………
PROJECT: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT
STRUCTURE IN ELDAMA RAVINE
05-06-20
y = 0.5001x
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
0 100 200 300
Tim
e (µ
sec)
Distance ( mm)
Homogeneity curve
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
31
DATE:
ULTRASONIC PULSE ANALYZER TEST FOR WALL (C/D - 4) FIRST FLOOR
Distance (mm) Transit time(µsec)
50 28.4
100 48.3
150 78.5
200 115.5
250 137.2
Remarks: Fairly Homogeneous concrete matrix; plaster has debonded
Tested by:……………….. Checked by:…………………
Sign:……….……..…….
Date:……………………
PROJECT: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT
STRUCTURE IN ELDAMA RAVINE
05-06-20
y = 0.5485x
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
0 100 200 300
Tim
e (µ
sec)
Distance ( mm)
Homogeneity curve
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459 Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
32
DATE:
ULTRASONIC PULSE ANALYZER TEST FOR WALL (5 - C/B) FIRST FLOOR
Distance (mm) Transit time(µsec)
50 39.3
100 125.4
150 236.2
200 426.6
250 545.4
Remarks: Non Homogeneous concrete matrix; plaster has debonded
Tested by:……………….. Checked by:…………………
Sign:……….……..…….
Date:……………………
PROJECT: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT
STRUCTURE IN ELDAMA RAVINE
05-06-20
y = 1.9753x
0.0
100.0
200.0
300.0
400.0
500.0
600.0
0 100 200 300
Tim
e (µ
sec)
Distance ( mm)
Homogeneity curve
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
33
DATE:
ULTRASONIC PULSE ANALYZER TEST FOR WALL (9 - B/C) FIRST FLOOR
Distance (mm) Transit time(µsec)
50 56.6
100 92.2
150 185.7
200 221.5
250 288.3
Remarks: Non Homogeneous concrete matrix; plaster has debonded
Tested by:……………….. Checked by:…………………
Sign:……….……..…….
Date:……………………
PROJECT: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT
STRUCTURE IN ELDAMA RAVINE
05-06-20
y = 1.1366x
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
0 100 200 300
Tim
e (µ
sec)
Distance ( mm)
Homogeneity curve
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
34
DATE:
ULTRASONIC PULSE ANALYZER TEST FOR WALL (A/B - 8) FIRST FLOOR
Distance (mm) Transit time(µsec)
50 66.3
100 122.4
150 141.2
200 170.2
250 201.1
Remarks: Non Homogeneous concrete matrix; plaster has debonded
Tested by:……………….. Checked by:…………………
Sign:……….……..…….
Date:……………………
PROJECT: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT
STRUCTURE IN ELDAMA RAVINE
05-06-20
y = 0.8804x
0.0
50.0
100.0
150.0
200.0
250.0
0 100 200 300
Tim
e (µ
sec)
Distance ( mm)
Homogeneity curve
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
35
2.4 Carbonation test
This test was conducted in accordance to BS 1881-210:2013 and BS EN
14630:2006.
Carbonation of concrete by attack from atmospheric carbon dioxide will result in a
reduction in alkalinity of the concrete, and increase the risk of reinforcement
corrosion. This will normally be restricted to a surface layer of only a few millimeters
thickness, in good quality concrete but can be much deeper in poor quality concrete,
with results as high as 30 mm being not uncommon. The extent of Carbonation can
be easily assessed by treating with phenolphthalein indicator the freshly exposed
surfaces of a piece of concrete which has been broken from a member to give
surfaces roughly perpendicular to the external face.
Plate 9: Showing extraction of concrete a core for carbonation test
36
2.4.1 Visual Assessments of Concrete Cores for Carbonation test
Visual assessment was carried out on all the concrete cores extracted for
carbonation both after sampling and after treating the cores with phenolphthalein
indicator.
The figure below shows the general condition of the concrete cores extracted from
the beams.
Figures 1- 4 show the general condition of concrete cores as noted:
Longitudinal Profile Cross-Section Comments
At Sample Location
Core Length= 165mm
Diameter= 100mm
The concrete has angular
aggregates with maximum
aggregate size of 20mm
The percentage of voids is
<0.5%
2 No. Rebars present
Carbonation depth = 15mm
Figure 1: Core extracted from first floor Slab C/D – 4/5
At Sample Location
Core Length= 140mm
Diameter= 100mm
The concrete has angular
aggregates with maximum
aggregate size of 20mm
The percentage of voids is
<0.5%
1 No. Rebars present
Carbonation depth = 35mm
Figure 2: Core extracted from first floor slab B/C – 4/5
37
Longitudinal Profile Cross-Section Comments
At Sample Location
Core Length=180mm
Diameter= 100mm
The concrete has angular
aggregates with maximum
aggregate size of 20mm
The percentage of voids is
<0.5%
2 No. Rebars present
Carbonation depth = NIL
Figure 3: Core extracted from first floor slab 5/8 – B/C
Longitudinal Profile Cross-Section Comments
At Sample Location
Core Length=145mm
Diameter= 100mm
The concrete has angular
aggregates with maximum
aggregate size of 20mm
The percentage of voids is
<0.5%
1 No. Rebars present
Carbonation depth = NIL
Figure 4: Core extracted from first floor slab 8/9 – C/D
38
2.4.2 Carbonation test results
39
Project: DEPTH OF CARBONATION TEST FOR THE BURNT BUILDING IN ELDAMA RAVINE
Date: 04.06.2020
First Slab C/D - 4/5 100 165 VERTICAL 15
First Slab B/C - 4/5 100 140 VERTICAL 35
First Slab 5/8 - B/C 100 180 VERTICAL NIL
First Slab 8/9 - C/D 100 145 VERTICAL NIL
Tested by:…………………………………….. Checked by:………………………………
Sign:……………...…………………………….
Date:…………………………………………….
Carbonation Depth test results( Tests carried out according to BS EN 14630-2006)
SITE SPECIMEN SAMPLING FORMS
Length
(mm)GridFloor Level
Element
Extracted
Depth of Carbonation
(mm)
Diameter
(mm)
Direction of
Extraction
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
40
2.5 Compressive Strength Test
Cores of 100mm diameter were used for compressive strength tests. The test
specimens were centrally positioned between the compressive test machine platens
and a load was then applied at a uniform rate, approximating the rate of stress of
about 15MPa/min, until the test specimen failed. The load at failure was recorded in
KN and the compressive strength was calculated to the nearest 0.1 MPa by dividing
the load at failure, in N, by the area of the contact face, in mm2. Correction factors
were then applied to derive the equivalent cube strength in accordance to BS 12504-
1.
Plate 10: Showing Core crushing in progress
41
2.5.1 Visual Assessments of Concrete Cores for compressive strength
Visual assessment was carried out on all the concrete cores both at the sample
location and after core preparations.
Figures 1- 4 shows the general condition of concrete cores as noted:
Longitudinal Profile Cross-Section Comments
At Sample Location
Length=165mm
Diameter= 100mm
The concrete has angular
aggregates with
maximum aggregate size
of 20mm
The percentage of voids
is <0.5%
2No. Rebar present
Trimming and capping
done at the top and
bottom to achieve parallel
surfaces.
Figure 1: Core for First floor slab grid C/D – 4/5
Longitudinal Profile Cross-Section Comments
At Sample Location
Length=140mm
Diameter= 100mm
The concrete has angular
aggregates with
maximum aggregate size
of 20mm
The percentage of voids
is <0.5%
1No. Rebars present
Trimming and capping
done at the top and
bottom to achieve parallel
surfaces.
Figure 2: Core for First floor slab grid B/C – 4/5
42
Longitudinal Profile Cross-Section Comments
At Sample Location
Length=180mm
Diameter= 100mm
The concrete has angular
aggregates with
maximum aggregate size
of 20mm
The percentage of voids
is <0.5%
2No. Rebars present
Trimming and capping
done at the top and
bottom to achieve
parallel surfaces.
Figure 3: Core for First floor slab grid 5/8 – B/C
Longitudinal Profile Cross-Section Comments
At Sample Location
Length=145mm
Diameter= 100mm
The concrete has angular
aggregates with
maximum aggregate size
of 20mm
The percentage of voids
is <0.5%
1No. Rebars present
Trimming and capping
done at the top and
bottom to achieve
parallel surfaces.
Figure 4: Core for First floor slab grid 8/9 – C/D
43
2.5.2 Core Compressive Strength Test Results
44
COMPRESSIVE STRENGTH OF CONCRETE CORES
BS EN 12504-1:2009, BS EN 13791:2007, BS 6089:2010
DATE SAMPLED 05th June 2020
DATE TESTED 8th June 2020
CLIENT
ELEMENT GRID FLOOR VOIDS HEIGHT CORE HEIGHT/ BULK COMPRESSIVE
LEVEL (mm) DIAMETER DIAMETER DENSITY STRENGTH
(mm) RATIO (kg/cu.m) (N/mm2)
Slab C/D - 4/5 Firs t Floor 0.5% 110 100 1.10 2273 125.6 16.0
Slab B/C - 4/5 Firs t Floor 0.5% 110 100 1.10 2265 119.8 15.3
Slab B/C - 5/8 Firs t Floor 0.5% 115 100 1.15 2265 112.5 14.3
Slab C/D - 8/9 Firs t Floor 0.5% 110 100 1.10 2265 105.1 13.4
TESTED BY: REPORTED BY: CHECKED BY:
PROJECTCONCRETE ASSESSMENT FOR THE
BURNT BUILDING IN ELDAMA RAVINELOCATION:
ELDAMA
RAVINEELEMENT:
15.8
13.9
15.1
KAREN ROSES JOINT BODY
FAILURE
LOAD (KN)
SLABS
EQVLT. CUBE STRENGTH
(BS EN 12504-1:09)
(N/mm2)
16.6
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ +254788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
45
2.6 Electromagnetic Ferroscan Test.
The electromagnetic test is conducted in accordance of BS 1881 – 204: 1988
A PS200 Ferroscan cover meter is used. A 600mm square template is fixed to the
structure and the area in question is scanned in two directions at right angles to each
other, in a series of sweeps. A calibrated wheel on the search head records where
the search head is at all times. Using electromagnetic principles and an on-board
computer analysis, an image of the underlying reinforcement is shown on a screen.
This is downloaded to a PC and analysed in detail to give readout of bar sizes. The
data can also be saved to a Microsoft Excel file.
When conducting these tests we made sure that the surface was uniform and level
as possible since bumps and unevenness would cause variation from the correct
readings.
Plate 11: Showing Electromagnetic Ferroscan test in progress
46
2.6.1 Electromagnetic Ferroscan Test Results
47
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT STRUCTURE
IN ELDAMA RAVINE
Date: 04.06.2020
Location: First floor
Element: Beam B - 4/5
Beam Size: 300 X 240
Electromagnetic Ferro Scan
Side Soffit
Main bars Links Main bars Links
1No. 16mm bottom bar 8mm @ 200mm c/c 2 No. 16 mm bottom bars 8mm @ 200mm c/c
Remarks: 2 No. 16mm bottom bars with 8mm links @ 200mmc/c
Cover to reinforcement = 25mm
Tested by:………………………………… Checked by:………………………………
Sign:…………………………………….
Date:………………………………………
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459 Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
48
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT STRUCTURE
IN ELDAMA RAVINE
Date: 04.06.2020
Location: First floor
Element: Beam C/D - 4
Beam Size: 270 X 270
Electromagnetic Ferro Scan
Side Soffit
Main bars Links Main bars Links
1No. 16mm bottom bar 8mm @ 200mm c/c 2 No. 16 mm bottom bars 8mm @ 200mm c/c
Remarks: 2 No. 16mm bottom bars with 8mm links @ 200mmc/c
Cover to reinforcement = 30mm
Tested by:………………………………… Checked by:………………………………
Sign:…………………………………….
Date:………………………………………
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
49
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT STRUCTURE
IN ELDAMA RAVINE
Date: 04.06.2020
Location: First floor
Element: Beam C - 5/8
Beam Size: 260 X 300
Electromagnetic Ferro Scan
Side Soffit
Main bars Links Main bars Links
1No. 16mm bottom bar 8mm @ 200mm c/c 2 No. 16 mm bottom bars 8mm @ 200mm c/c
Remarks: 2 No. 16mm bottom bars with 8mm links @ 200mmc/c
Cover to reinforcement = 25mm
Tested by:………………………………… Checked by:………………………………
Sign:…………………………………….
Date:………………………………………
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
50
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT STRUCTURE
IN ELDAMA RAVINE
Date: 04.06.2020
Location: First floor
Element: Beam 8/9 - C
Beam Size: 310
Electromagnetic Ferro Scan
Soffit
Main bars Links
2No. 16mm bottom bar 8mm @ 200mm c/c
Remarks: 2 No. 16mm bottom bars with 8mm links @ 200mmc/c
Cover to reinforcement = 25mm
Tested by:………………………………… Checked by:………………………………
Sign:…………………………………….
Date:………………………………………
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459 Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
51
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT BUILDING
IN ELDAMA RAVINE
Date: 04.06.2020
Location: First Floor
Element: Column 4 - D
Column Size: 220mm
Electromagnetic Ferro Scan
SIDE
Main bars Links
2No. 12mm bars
Remarks: 2No. 12mm bars with 8mm links @ 200c/c (single face scanned)
Cover to reinforcement = 20mm
Tested by:………………………………… Checked by:………………………………
Sign:…………………………………….
Date:………………………………………
8mm bars @ 200c/c
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
52
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT BUILDING
IN ELDAMA RAVINE
Date: 04.06.2020
Location: Ground Floor
Element: Column 6 - B
Column Size: FWW
Electromagnetic Ferro Scan
SIDE
Main bars Links
2No. 12mm bars
Remarks: 2No. 12mm bars with 8mm links @ 200c/c (single face scanned)
Cover to reinforcement = 20mm
Tested by:………………………………… Checked by:………………………………
Sign:…………………………………….
Date:………………………………………
8mm bars @ 200c/c
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
53
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT BUILDING
IN ELDAMA RAVINE
Date: 04.06.2020
Location: First Floor
Element: Column 9" - D
Column Size: FWW
Electromagnetic Ferro Scan
SIDE
Main bars Links
2No. 12mm bars
Remarks: 2No. 12mm bars with 8mm links @ 200c/c (single face scanned)
Cover to reinforcement = 30mm
Tested by:………………………………… Checked by:………………………………
Sign:…………………………………….
Date:………………………………………
8mm bars @ 200c/c
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, Kenya
Parklands,Forest Road/Forest Court,Mezzanine FloorOffice : +254705186673/ 0788316459
Email: [email protected] [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
54
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT BUILDING
IN ELDAMA RAVINE
Date: 04-06-20
Location: First floor
Element: Slab 4/5 - A/B
Electromagnetic Ferro Scan
Bottom 1 Bottom 2
10mm bars @ 200c/c 10mm bars @ 200c/c
Remarks: Bottom 1: 10mm bars @ 200c/c
Bottom 2: 10mm bars @ 200c/c
Cover to reinforcement = 45mm
Tested by:…………………………………….. Checked by:…………………………
Sign:…………………………………….
Date:…………………………………………….
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, KenyaParklands,Forest Road/Forest Court Mezzanine FloorOffice: +254 705186673/ +254 788316459Email: [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
55
Project: STRUCTURAL CONCRETE ASSESSMENT FOR THE BURNT BUILDING
IN ELDAMA RAVINE
Date: 04-06-20
Location: First floor
Element: Slab 8/9 - A/B
Electromagnetic Ferro Scan
Bottom 1 Bottom 2
10mm bars @ 200c/c 10mm bars @ 200c/c
Remarks: Bottom 1: 10mm bars @ 200c/c
Bottom 2: 10mm bars @ 200c/c
Cover to reinforcement = 45mm
Tested by:…………………………………….. Checked by:…………………………
Sign:…………………………………….
Date:…………………………………………….
Leeds Engineering Company LtdP.O. Box 64785, 00620Nairobi, KenyaParklands,Forest Road/Forest Court Mezzanine FloorOffice: +254 705186673/ +254 788316459Email: [email protected]
Leeds Engineering Company Ltd. P.O. Box 64785 - 00620, Nairobi, Kenya MOBILE : 0705 186673 / 0788 316459
Email: [email protected]
Date:………………………………….….
Sign:………………………………….….
56
3.0 Conclusions and Recommendations
3.1 Schmidt hammers test results
The tests were carried out in accordance to BS EN 12504:2-2012.
Results obtained from this test regime confirm that concrete on structural members
achieved an average compressive strength of 15 N/mm². This is below the nominal
concrete strength of C20 for that nature of a structure; an indication that the concrete
strength has been affected by the fire exposure.
3.2 Ultrasonic Pulse Velocity Test
The tests were carried out in accordance to BS EN 12504:2-2012.
Ultrasonic pulse velocity test was carried out on concrete elements to assess the
quality of concrete on these members. The test was also done on plastered
elements to assess whether the plaster has de-bonded.
Direct Ultrasonic Pulse Velocity test results showed that the concrete on structural
elements was ranging from doubtful quality to good quality. This is an indication
that surface concrete on most of the affected elements has developed voids, cracks
and internal cavities due to fire exposure.
Results for Indirect Ultrasonic Pulse Velocity test on concrete elements gave largely
non-homogeneous concrete and some fairly homogenous concrete matrix. This is
a further indication that surface concrete has developed voids, cracks and internal
cavities due to the fire exposure. Indirect Ultrasonic Pulse Velocity test results on
plastered elements also confirm that plaster has de-bonded on most of the elements.
Concrete strength assessed through Ultrasonic Pulse Velocity test gave an average
of 16.9 N/mm². This is below the nominal concrete strength of C20 for that nature of
a structure; an indication that the concrete strength has been affected by the fire
exposure.
3.3 Core compressive strength test results
The tests were carried out in accordance to BS EN 12504:1-2009, BS EN 13791-
2007 and BS 6089:2010.
Results obtained from this test regime confirm that concrete on structural members
achieved an average compressive strength of 15.4 N/mm2. This is below the nominal
concrete strength of C20 for that nature of a structure; an indication that the concrete
strength has been affected by the fire exposure.
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3.4 Carbonation test results
This test was carried out in accordance to BS 1881-210:2013 and BS EN
14630:2006.
Results obtained from carbonation test confirm that the carbonation depth was NIL
for some cores, and in the range of 15mm - 35mm for the other cores. Considering
an average concrete cover to reinforcement of around 25mm, the carbonation depth
for the affected elements is high. Thus, in general, carbonation front has reached the
vicinity of the surface of the Rebars for most of the affected elements. This increases
the risk of reinforcement corrosion in the elements thereby undermining their yield
strength.
3.5 Reinforcement Details
The tests were carried out in accordance to BS 1881 – 204: 1988.
The columns were established to have 4No 12mm bars with 8mm links at a
spacing of 200mm c/c.
Beams were established to have 2No. 16mm bottom bars with 8mm links at a
spacing of 200mm c/c.
The slabs were established to have 10mm bars bottom 1 at a spacing of 200mm c/c
and 10mm bars bottom 2 at a spacing of 200mm.
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3.6 General conclusions
i. The concrete strength on structural elements is below the nominal concrete
strength of C20 for that nature of a structure. This gives an indication that the
concrete strength has been affected by the fire exposure
ii. Surface concrete has deteriorated as a result of fire exposure. It has developed
voids, cracks and internal cavities.
iii. Carbonation depth has reached the vicinity of the surface of the rebars. There is a
high risk of reinforcement corrosion considering that this is a time dependent
process.
iv. Considering the low concrete strengths, it is our conclusion that the structural
capacity of the concrete members including first floor beams, first floor slab and
ground floor columns within grid lines 1/5-A/D has been compromised. As these
members are still intact, they can still be repaired and strengthened for them to
achieve their full structural potential.
v. The structural frame above the suspended slab is completely damaged and has
been weakened by the fire. This frame therefore cannot be salvaged.
3.7 Recommendations
Following the assessments carried out, the physical conditions observed and tests
carried out, the structure has been found to be adversely affected by the fire incident.
The load carrying capacity of the structural frame has therefore been undermined. It
is imperative that urgent corrective measures are undertaken on the damaged areas
by carrying out the following procedures;
i. Repair of all the concrete elements within the ground floor and first floor levels
that have developed surface defects by use of a structural repair mortar
between grid lines 1/5-A/D.
ii. To safeguard the existing ground floor columns, first floor slab and first floor
beams between grid lines 1/5-A/D against carbonation attack, we propose
demolition of columns and recasting with a suitable structural repair mortar
before containing them by use of carbon fibre wraps. The repair mortar shall
be a mixture of Master Flow 928 hydraulic cement-based mineral aggregate
non-shrink grout and 10mm aggregates to a ratio of 1:2. The first floor slab and
first floor beams shall be strengthened using epoxy bonded carbon fibre strips
as specified below.
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iii. The existing reinforcement on ground floor columns, first floor beams and slab
that experienced the heat, were never checked for percentage (%) elongation
including tension, bending and re bending properties after the fire exposure. In
addition, we note that reinforcement in these elements may have been affected
by carbonation attack. It is therefore important we strengthen the these
elements by use of carbon fibre wraps and epoxy bonded carbon fibre strips as
follows;
d) One (1) laminate plate of 50mm width should be fixed at the center of the
beam soffit covering the total length of the beam to increase flexural
capacity and one (1) shear strip should be fixed at either sides of the
beam to increase shear capacity.
e) Laminate plates of 50mm width should be fixed at the soffit of the first
floor slab in one direction at a spacing of 1500mm c/c to provide
additional flexural resistance.
f) Strengthening of ground floor columns between grid lines 1/5-A/D by
application of epoxy bonded unidirectional carbon fibre wrap placed
around the entire circumference of the columns.
iv. Demolishing and reconstruction of the entire structural frame above the first
floor slab.
v. Reconstruction of the entire roof structure.
vi. Redoing all non-structural elements such as non-load bearing walls, partitions,
wall linings, ceilings, flashings, windows, glazing, roofing, doors, tiles, movable
and fixed furniture
vii. Redoing all the services buried in walls, concrete elements or on the surfaces
such electrical and mechanical services and fittings.
viii. All the structural repair work should be done under instructions and supervision
of a competent structural Engineer.
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3.8 Mechanical & Electrical Services
61
ITEM AREA OBSERVATIONS RECOMMENDATION PHOTOS 1 GF – Commercial
recreation centre
1. All electrical fitting and
wiring burnt, damaged
beyond salvage.
3. Replace all electrical
fitting and wiring with new.
4. To reinstate fire alarm
detection devices and
security surveillance
system
2 GF – ATS board
adjacent to staircase
3. The board not
affected by fire. The
ATS and some
isolators observed
intact
4. Some cut outs
observed
disconnected.
1. To replace with an ATS
board that incorporates
latest switchgear that
got self tripping
mechanism incase of a
fault.
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3 GF – KPLC meter
chamber
6. Observed in a standlone
chamber surrounded by
vegetation
7. 2. The chamber not
accessible and not secured
by a padlock.
8. Cables poorly managed
9. Mounting height for the
switchgear too low against
working safely guidelines
10. Routing for cables from
transformer to metering
chamber to ATS board not
traceable.
5. The meter chamber
should be easily
accessible and lockable.
6. Cables to be neatly
managed and labelled.
7. The mounting heights
to be raised to
1200mm above
finished floor level
8. Cable routing from the
KPLC transformer to
metering chamber to ATS
board should be in well-
marked & identifiable
accessible ducts.
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ITEM AREA OBSERVATIONS RECOMMENDATION PHOTOS 4 Ground floor – Diesel
powered Generator
4. 10kva 3phase diesel powered generator observed in a secure metal cage behind the building.
5. Observed ok with no visible effect of fire
6. Power and control cable exposed on their entry to ATS board at the staircase lobby observed burnt.
1. Power and control cable
from Generator to ATS
board to be replaced with
new.
5.0
Ground floor – External services
4. Some lights on the
perimeter column at the
backside of the plot
observed burnt
5. The top most water tank
observed burnt on the
side
6. The rear side rain
water gutters and drop
pipes observed burnt
1. Replace all the burnt items with new
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ITEM AREA OBSERVATIONS RECOMMENDATION PHOTOS
6.0
1st Floor –
Staircase lobby
1. The fitting on roof and wall all burnt.
1.Replace all burnt fittings
7.0
1st Floor –
Computer room
3. All electrical fitting and
wiring burnt, damaged
beyond salvage.
4. 2no portable fire
extinguisher cylinders
observed beyond
salvage
3. Replace all burnt fittings
4. Reinstate the fire
detection and
extinguishing system in
this room as per building
fire code
8.0 1st Floor –
Office
room(2no)
1. All electrical fitting and
wiring burnt,
damaged beyond
salvage.
3. Replace all burnt
fittings
4. Reinstate fire
detection & alarm
system as per
building fire code
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ITEM AREA OBSERVATIONS RECOMMENDATION PHOTOS
9.0 1st floor - Library 1. All electrical fitting and
wiring burnt, damaged
beyond salvage.
3. Replace all burnt fittings
4. Reinstate fire detection &
alarm system as per
building fire code
10. 1st floor - WC 4. All electrical fitting
and wiring burnt,
damaged beyond
salvage.
5. Sanitary fitting
burnt beyond
salvage
6. Concealed
plumbing pipe work
also observed
burnt.
1. Replace all burnt fittings
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4.0 Appendices
4.1 Layout Plan
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68
4.2 Photographs
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70
71
72
73
74
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4.2 References
1. BS EN 12504:2-2012)– Recommendations for surface hardness testing by
rebound hammer
2. BS 1881 – 204: 1988 – Recommendations for conducting electromagnetic
tests using a cover meter and Ferrouscan
3. BS EN 12504-1:2009, Cored specimens-Taking, examining and testing in
compression
4. Determination of Ultrasonic Pulse Velocity – BS12504:Part 4 : 2004
5. BS 1881-210:2013 - Testing hardened concrete. Determination of the
potential carbonation resistance of concrete. Accelerated carbonation
method
6. BS EN 14630:2006 - Products and systems for the protection and repair of
concrete structures. Test methods. Determination of carbonation depth in
hardened concrete by the phenolphthalein method
7. BS 4449:2005+A3:2016 - Steel for the reinforcement of concrete.
8. ISO 6892-1:2019(en) - Metallic materials — Tensile testing — Part 1:
Method of test at room temperature
9. Non – destructive methods of test for concrete - BS4408:Part 5 : 1974
10. J H Bungey, S G Millard, M G Grantham, Testing of concrete in structures, 4
ed. Taylor & Francis, 2006.
11. M Goueygou, O Abrahan, J-F Lataste, “A comparative study of two non-
destructive testing methods to assess near-surface mechanical damage in
concrete structures,” NDT&E International. 41, 2008.
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Disclaimer The content of this report reflect the views that is (are) responsible for the fact and the accuracy of the data presented herein. This report does not constitute a standard specification or regulation and shall not be reproduced in part or in full without the written approval of Leeds Engineering Company Ltd