detailed technical assessment of mr. shiva poudel & mrs
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Detailed Technical Assessment of
Mr. Shiva Poudel & Mrs. Indu Adhikari’s Residence
At Bansbari, Kathmandu
(September-2015)
Submitted by:
BK Shrestha & Builders P. Ltd.
Lagan, Ganabahal, Kathmandu
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
1. INTRODUCTION
1.1 General Background
According to the relevant I. S. Codes and Nepalese Standard Code, Nepal is rated as a zone of high
seismic activity. The vulnerability and seismic risk is defined as extreme and Nepal is placed in zone
five (V) with the value of seismic co-efficient 0.36, the highest of all. Kathmandu lies about 75 km
from the highly active boundary between the Eurasian and Indian tectonic plates along the
Himalayan front, which has been the site of many large magnitude earthquakes within historical
times. Moreover, Kathmandu is sited on the deep alluvial deposits of Kathmandu Valley; such
deposits may also prone to amplify earthquake ground motions, making them more destructive, and
the deposits may also be prone to liquefaction during strong earthquake.
The earthquake risk zones for unreinforced masonry building for Nepal is provided by Nepal National
Building Codes (Error! Reference source not found.). The figure clearly illustrates that Kathmandu
valley is lying in Zone A with high level of seismic risk associated with unreinforced masonry building.
Figure 1 : Seismic Zones for Unreinforced Masonry Buildings (Source: NNBC 109: 1994)
The level of Risk associated with the Seismic Zones (Error! Reference source not found.) shows that
Kathmandu valley is lying in zone A where the risk level is high with potential for widespread
collapse and heavy damage to unreinforced masonry buildings. The zone wise risk factor associated
with masonry building is presented in Error! Reference source not found.
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
Table 1: Seismic Zones for Unreinforced Masonry Buildings (Source: NNBC 109: 1994)
Zone Zone Coefficient Risk
A Z ≥ 1.0 Widespread Collapse and Heavy Damage
B 0.8 ≥ Z > 1.0 Moderate Damage
C Z < 0.8 Minor Damage
On 25 April 2015, massive earthquake triggered Nepal which occurred at 11.56 NST with a local
magnitude of 7.8 Richter Scale with maximum Mercalli Intensity (MMI) of VIII which had potential to
damage severely the buildings, boundary wall and other structures. To date, more than 10,000
people were killed and injured more than 40,000. Epicenter of 25 April earthquake was at Barpak
village of Gorkha district. The seismic energy released at the depth of 15 km (approximately) which is
called Hypocenter. Following major earthquake on 25 April, continued aftershocks more than two
hundred in numbers occurred in the country ranging from 4 to 6.8 Richter Scale (local magnitude).
The latest aftershock hit Nepal with 6.8 Richter scale on 12 May 2015 whose epicenter was at
Sunkhani village of Dolakha district.
According to USGS, the temblor was caused by a sudden thrust, or release of deposited energy along
the major fault line where the Indian plate is slowly diving underneath the Eurasian Plate. Nepal
locates between these two plates, therefore, is always threat to vulnerable structures thereby to
human beings as well.
At the present scenario the buildings that were constructed in the past are very much susceptible to
the risk of earthquake because they were not constructed by considering the seismic load. These
kinds of seismically vulnerable buildings can turn in to the death trap for large no of people if not
access from the perspective of earthquake. Hence there is great need for seismic assessment of the
buildings.
BK Shrestha & Builders P. Ltd. Is Nepali registered, Kathmandu based, Construction Company which
has long experience in the field of seismic intervention work and major construction work as well.
The report describes the method and findings of the assessment, which was conducted on
September 11 and 15, 2015. Recommendations and conclusions are provided indicating safety of
building occupants.
This report is based on the best engineering judgment arrived at from the visual inspection during
site visits, prevailing practices of building construction in the Kathmandu valley, and conduction of
some necessary field tests at some critical sections of the existing structural elements of the building
and verifying the findings. All possible efforts have been made to provide an accurate and
authoritative seismic vulnerable assessment of the building.
1.2 Scope of Works The main objectives of assignment are:
• To carry out a structural inspection of buildings on the compound, aiming to establish the
seismic vulnerability of the building and appropriate structural remedial measures.
• To assess the building and its condition, to explore the structural layout and to determine
the integrity of the building through site observation, field investigations, a study of the
drawings.
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
• To carry out simple field tests as necessary to obtain brief notifications regarding structure
of building.
• To hold discussions with house owner regarding damages as a result of recent earthquake
on 25 April 2015 and aftershocks thereafter.
• To prepare a report on the findings, conclusions and recommendations arising from the
work carried out.
The following field tests have been carried out for the building:
1) Schmidt Hammer Test
This is also the non-destructive test in which the Schmidt hammer measures the rebound of a spring-
loaded mass impacting against the surface of the sample. The test hammer will hit the concrete at a
defined energy. Its rebound is dependent on the hardness of the concrete and is measured by the
test equipment. By reference to the conversion chart, the rebound value can be used to determine
the compressive strength. When conducting the test the hammer should be held at right angles to
the surface which in turn should be flat and smooth. The rebound reading will be affected by the
orientation of the hammer, when used in a vertical position (on the underside of a surface) gravity
will increase the rebound distance of the mass and vice versa for a test conducted on a floor slab.
This test method for testing concrete is governed by ASTM C805.
At several points of structural column at different location or grid have been chosen and marked to
carry out this test. Please refer attached test results herewith. This sample result has been assumed
as comprehensive representation of overall concrete quality of building.
Ferro or Re bar Scanner
Ferro Scanning enables easy location of steel reinforcement in concrete which locates steel
reinforcing to 180 mm deep and determine depth, diameter and condition of rebar. In our specific
case, the Ferro Scanning will highly enable us to further analyze the structure for detailed seismic
vulnerability evaluation test, which may require repair or retrofitting.
1.3 Categorization of the Buildings available in Kathmandu (Identification of
building typology)
Most buildings, especially residential buildings are constructed in a traditional manner in the
Kathmandu valley. In general, we can categorize the available buildings in Kathmandu Valley into the
following four types:
TYPE 1: Building constructed with reinforced concrete shear wall; relatively rare, and found only in
high rise commercial building.
TYPE 2: Residential building with reinforced cement concrete frame which is also called frame
structured building designed to resist lateral forces and more or less meet the seismic codeof
criteria.
TYPE 3: Residential building with confined brick masonry system: 230 x 230 mm RCC columns tied
with horizontal beams at plinth and every floor level.
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
TYPE 4: Residential building constructed in pure brick masonry system; is also known as load bearing
structure.
The assessed building can be categorized as TYPE 4.
1.4 Introduction of the Building
The building is located at Bansbari, approximately 1 km distance from Maharajgunj ring road
intersection. The building is two storeys high excluding basement of pure machine made brick
masonry structure (fair faced) with load bearing walls constructed in rich cement mortar. The
building is minor irregular in both orthogonal directions but can be neglected. Most of walls in the
first floor are vertically continued from the ground floor, being separated with RCC floor beam and
slab. The first floor has been covered with RC beam and pitched roof slab. The thickness of
peripheral wall is 370 mm thick including all finishes. The interior partition walls in ground floor and
first has been constructed of same thickness as of peripheral wall except in bathroom walls which is
a positive aspect in consideration of the seismic aspect for such a building of high importance.
The footprint area of the ground floor is 1260.20 sqft and the first floor is 1271.45 sqft. The building
posses floor beam and slab at each floor level. Most of roof slab are pitched roof being provided by
sloped beam. A single flight spiral type staircase is located near main entrance door of building.
As per field investigations, there are structural beams at each floor level as a result the building can
act monolithically in providing resistance to earthquakes as well as can act with a diaphragm effect
to seismic activity. In ground floor dining and kitchen and first floor backside, the distances from the
wall corners to the openings do not meet the code of minimum criteria. The minimum distance as
per the NBC code for any openings should be 600 mm from the wall corner or junction or ½ of the
opening. This is the main drawback of building however, the size of window can easily be modified
to reduced size later in future as there is no immediate threat for moderate earthquake. Further,
some strengthening work will be required in future for cantilevered portion at first floor, backside.
The front car port slab has been supported by two RCC columns which seems safe.
1.5 Existing Conditions
BUILDING HISTORY
Year Constructed: 1992
Maintenance: None
Renovation: None
Builders Information: None
Owner Information: Mr. Shiva Poudel & Mrs. Indu Adhikari
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
OVERALL DESCRIPTION
Number of Storeys: Two Storey
Height of Storeys
Ground floor: 9’ to 11’
First floor: 9’ to 11’
Horizontal Plan Configuration: Not symmetrical
Vertical Configuration: Symmetrical in most sections
Floor Area:
Ground floor: 12060.20 sft
First floor: 1271.45 sft
STRUCTURE
Type: Load Bearing Structure
Walls: 350 mm thick peripheral and interior wall, 120 mm thick in bathroom
partitions
Slenderness ratio: 7.7 which is less than 17. Therefore, the effective wall height/length to the
wall thickness in this building is within the seismic code standard.
Floors:
Ground floor: Marble in lobby and passage, tile in kitchen, dining and toilet, wooden
flooring in sitting area, guest room
First floor: RCC slab, wooden flooring in bed rooms, marble in lobby, passage and
staircase
Roof: RCC beam and pitched slab roof
CONDITION
Cracks: Minor thermal cracks were observed in first floor west side bed room, which
is easily repairable. In other parts no cracks were seen.
Water: Not observed during assessment
Termites: Not observed during assessment
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
Damp: Not observed during assessment
2 Findings and Recommendation (Please refer Annex)
• Total average grade of concrete as per test is 20 MPa, which was tested on external column of
car porch.
• In external column of car porch at ground floor , 8 nos of 12mm dia re-bars & 6mm dia stirrups
6”c/c .
• In staircase slab 12 mm dia re-bar @ 6 “spacing is found at slab bottom.
• In beam in front of main door at ground floor Grid 3 B-C, 4 no re-bar of 12 mm dia & spacing of
3 “ is found , stirrups of 6mm @ 6 “c/c.
• On first floor, in beam above staircase Grid 3-4 B-C, two nos 12 mm dia with 6mm stirrups @
6”c/c.
• On first floor beam in front of bed room Grid E 2-3 , two nos of 12 mm dia with 6mm stirrups
spacing @ 6 “ c/c.
3 Final conclusion
Overall, the building is safe for habitants in respect of structural soundness as a result of rapid visual
assessment of building and test results.
This shall be remarkably notified that, the timing, location and intensity of seismic events cannot be
predicted accurately, some uncertainties remain regarding the actual consequences of a particular
earthquake shaking.
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
ANNEX-I
(Non Destructive Test-I) Re-Bound Hammer
PROJECT : Residential Building
Floor : Ground
Knowledge Factor
: 1.00
C.F. 0.73
Elemen
t : Column Grid : A5
S.N.
Rebound
Number
Mean
Value
Compressive
Strength Adopted Value Remarks
1 25
25.111111
1 18.43 20
2 26
3 24
4 20
Discarde
d
5 22
6 29
7 24
8 26
9 33
Discarde
d
10 25
11 25
12 20
Discarde
d
The Grade of concrete is as per rebound hammer test is found to be 20 MPa ( M 20 ).
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
ANNEX-II
(Non Destructive Test-II) Re-bar Locator / Scanner
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
ANNEX-III
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
PHOTOGRAPHS
Photographs showing preparation Photographs showing re bar scanning test
of schimdt hammer test at porch column at ground floor beam
Detailed Technical Assessment of Mr. Shiva Poudel & Mrs Indu Adhikari’s Residence at Bansbari, Kathmandu, Nepal
Photographs showing conduction of rebar scanning in staircase slab
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