2. 2
PROJECT MANAGEMENT
What is Project?
A Project is an investment of resources on a package of Inter-related time bound activitites.
Thus a project becomes a time bound task. A project should have a definite beginning and
an end.
Every project has two phases
a. Construction b. Operation
Examples
1. Construction of an irrigation dam/Bridge/Building
2. Systematic land developments
3. Establishing a milk chilling plants
4. Appointing staff
5. Launching a new products etc
6. 6
EVALUATION IS AN ESENTIAL COMPONENT OF DECISION MAKING
APPRASIAL PRE-PROJECT/INVESTMENT INVESTMENT
CONTINUATION
MODIFICATION
EVALUATION EXTENSION
EXPANSION
APRAISAL - POLICTICAL ACCEPTANCE REPLICATION
- SOCIAL ACCEPTANCE
- ECONOMIC VIABILITY
- FINANCIAL VIABILITY
- TECHNICAL FEASIBILITY
- MANAGERIAL CAPABILITY
- ENVIRONMENTAL STABILITY
MONITORING - TIME SCHEDULE ADHERENCE
- COORDINATION
- RESOURCE AVAILABILITY AND USE
- PEOPLES PARTICIPATION
- BENEFIT FLOW
INPUTS - MATERIALS
- MANPOWER
- MACHINERY
- FINANCE
- IMPLEMENTATION PLAN
7. 7
IMPLEMENTATION - COORDINATION
PROCESS
- PARTICIPATION
- RESOURCE UTILIZATION
- TIME SCHEDULE ADHERENCE
OUTPUT - TARGETS AND THEIR ACHIEVEMENTS
OUTCOME - RESULTS GENERATED BY OUTPUT
8. 8
PREPARING A PROJECT EXECUTION PLAN
STEP 1: List of all the activities to be executed. (If the list is prepared according
to the department/agencies it is known as the work breakdown structure.
STEP 2 : Specify a Logical sequence in which the activities need to be executed
(this will indicates which activities will follow any given activity/which activities can
be taken up concurrent/parallel.
STEP 3 : Estimate/Specify the time duration for each activity.
STEP 4 : Assemble the activities in the form of a flow diagram (known as
network plan)
STEP 5 : Analyse the flow diagram
Some of the symbols, rotations, terms and their definitions used in the project
executed plan (PEP).
9. 9
a) Every activity has to begin with an event and end with another event
b) An event occur at a point of time
Examples - Receiving a promotion order
- Staff appointed
- Plant approved etc
a) An event is represented by a circle
Examples - Conduct a survey
- Prepare a proposal
- Identity beneficiaries
- Process the loan applications etc.
a) An activity is represented by line with an arrow
The event with which an activity begins is the predecessor event and the event with which it
ends is the successor event.
Predecessor Successor
(K)
(activity code)
4 weeks
Event (Activity duration) Event
5 7
10. 10
SITE INSPECTION & MONITORING
Engineering comprises of
1. Planning
2. Design
3. Construction
4. Quality control
5. Maintenance
Inspection : To ensure that the construction complies with the design, inspection
procedure should be set up covering materials, records, workmanship and
construction.
Object:- The objective is aimed at equipping the engineers with the required
know how and acquainting them with the recent developments in the field concrete
making materials and techniques with particular reference to workmanship and
quality control.
11. 11
Design: Design of structure presents two fold problems
1. Functional Design:- It has to be so constructed that it serves the need
efficiently for which it was intended.
2. Structural Design:- It has to be strong enough to resist the loads and
forces to which is subjected during its service.
12. 12
General:-
1. Scope of Work
2. Materials and Test standards
3. Construction Equipment
4. Contract Drawings and Specification
5. Site organization and planning, work program.
6. Smooth conduct of execution of work.
7. Quality Control.
8. Safety precaution in the site.
13. 13
PHYSICAL INSPECTION
1. Inspection of works of various stages
2. Sources of materials
3. Collection of materials at site, workmanship, equipment, supervision to be checked
at every level.
4. Assessment of quality on the above
5. Proper lab facilities at site assisted by experienced technicians
6. Review of detailed work program
7. Review of construction methods with reference to technical methods
8. Review of the test result and acceptance criteria.
9. Proper technical supervision of work to ensure their quality and conformity with the
standards and specification
10.Check list of every activity involved in the work, samples of all important materials
11.Review of site records.
14. 14
Pre detailing of the project
Pretender stage
Consultant
Detailed Feasibility study
Project preparation
Detailed Designs &
Drawing
Detailing of project
Selection of Contractor
Award of work
Contractor
Detailed study of site
Detailed study of project
document, Drawings
Planning of work and
construction schedule
15. 15
Note: Not to entertain changes in proposal
once approved unless and until is
unavailable due to regions beyond their
control.
16. 16
Advanced Planning for execution
Construction schedule of
Total project
Monthly Schedule
Weekly Schedule
Day Schedule for
Important activities
Materials
Form work
Equipments
Manpower
Schedule of Resources
17. 17
Quality Control/
Quality Assurance
Testing of Materials /
Fixures / Form Work
Acceptance Test with
The engineer Periodical check test
Daily/Weekly
routine test at
site lab
For Items of
Construction
Fixures/ Form Work
For item cube strength
For aggregates,
Fresh concrete
Cube strength etc
Inspection and Approval
Require for
Inspection & approval
to engineer as
prepared by
contractor
1. Method of construction
2. Shop drawings
3. Temporary work drawings
4. Construction schedule
5. All stage of construction activities
Inspection , checking &
Approval as per approved
drawings, specification
YesNo
Return to Contractor
With comments
18. 18
CONSTRUCTION PRACTICES
• Placing of concrete (As per clause No. 13.2 of IS 456/2000)
1. Design mix to be obtained.
2. The concrete to be deposited as nearly as practicable in its final position.
3. Avoid lengthy handling and segregation of mix.
4. The concrete shall be placed and compacted before initial setting of
concrete.
5. Avoid segregation or displacement of reinforcement form work.
19. 19
CONSTRUCTION PRACTICES
• Compaction (As per clause No. 13.2 of IS.456/2000)
1. Concrete to be compacted with pan vibrators for slabs and pin vibrators for
beams/columns
20. 20
CONSTRUCTION PRACTICES
• Slump Test (As per clause No. 13.2 of IS 456/2000)
1. For concreting of lightly reinforced sections, mass concreting with very low
and low degree of workability, the slump is to be between 25 to 75 mm.
2. For concreting with heavily reinforced sections with medium degree of
workability the slump is to be between 50 to 100 or 75 to 100 as directed by
Engineer-in-charge.
21. 21
CONSTRUCTION PRACTICES
• Stone masonary
1. Coursed rubble stone masonry
1. The face stones shall be squared on all joints with beds horizontal.
2. They shall be set in regular courses of uniform thickness fom bottom to
top throughout.
3. No face stone shall be less width in plan than 150 mm for walls of 400
mm thick 200 mm for walls of 450 mm thick and 250 mm for walls of 600
mm thick and above.
4. The face stones shall be laid headers and stretchers alternatively so as
to break joints.
5. The stones shall be solidly bedded, set in full mortar with joints not
exceeding 12mm and extend back into the hearting.
6. The height of the stone shall not exceed breadth at face nor the length
inwards.
2. Through stones and Headers
1. In all the works upto a width of 600mm, bond stones running though the
wall to be provided at an intervals of 2 m in each course.
2. For walls thicker than 600mm, a line of headers each headers each
header overlapping by 150mm minimum shall be provided from front to
back at 2 m intervals in each course.
3. The position of the stones shall be marked on both the faces.
22. 22
CONSTRUCTION PRACTICES
• Brick work
1. The thickness of joints in case of masonry with first class brigcks shall not be
more than 10mm.
2. In case of masonry with second class bricks joints shall not be more than 12
mm.
3. The bricks shall be thoroughly soaked in clean water.
4. The cessation of bubbles when the bricks are immersed in water is an
indication of thorough soaking of bricks.
5. The bricks shall be laid with joints full of mortar.
6. The face joints shall be racked by jacking tool when the mortar is green.
7. The wall construction shall be taken up truly plumb.
8. All courses shall be laid truly horizontal.
9. All vertical joints shall be truly vertical.
10.The thickness of brick course shall be kept uniform and with their frogs kept
upward.
23. 23
CONSTRUCTION PRACTICES
• Plastering
1. Water the brick wall before start of plastering.
2. Chicken mesh at joints of brick wall and R.C.C member to be provided.
3. Dry mixing of cement and sand is to be done on impervious platform.
4. Holes provided for scaffolding are to be closed along with plastering.
5. Level marking must be done in advance form time to time.
6. Chip off concrete surface before starting plastering.
7. Gaps around door window frames to be filled.
8. Base coat of plaster to be checked before application of finishing coat.
24. 24
SUMMARY OF QUALITY CHECKS TO BE DONE ON BULLDINGS WORKS.
• Bearing capacity of soil to be checked in advance.
• Material to be approved in advance.
• Quality of materials to be checked periodically.
• Steel to be obtained from main manufacturers only.
• Size of footings, pedestals, columns, beams are to be checked.
• Design mixes to be obtained in advance.
• Cover to the reinforcement as per structural requirement to be checked.
• Thickness of plastering to wall be checked.
• Proportion, workability and vibration of CC mix and cement mortar proportion be
checked.
• Cube samples be collected for testing in lab.
25. 25
GUIDE LINE FOR QUALITY IMPROVEMENT IN
BUILDINGS AND INTERNAL ROADS
Let us understand first by what we mean by the terms of Quality Control and
Quality Assurance.
Quality Assurance(QA):- To provide confidence that a product or facility will
perform satisfactorily is service. QA involves continued evaluation of the
activities of planning, design, development of plans and specification.
Quality Control(QC):- Normally refers to those tests necessary to control a
product and to determine the quality of the product being produced.
26. 26
To improve the quality in buildings and roads the following are
1. Approval of methodology statement and quality assurance plan is essential
to monitor the work.
2. Construction specification and estimate should provide effective quality
control.
3. Adequately trained staff and equipped agency for exercising quality control
should be set up.
4. Periodical approval of the quality control data should be made not only for
implementation during construction but also for effecting possible,
improvement in quality control and construction techniques themselves.
5. Updating of knowledge by on job training.
Statistical concepts of Quality Control
Statistical methods are used to as certain the range of values that can be
expected under the existing condition.
27. 27
Reasons for variation in concrete quality
1. Proportion of Ingredients
2. Quality of ingredients
3. Water cement ratio/workability
4. Method of mixing, placing, compaction and curing.
5. Work man ship
6. Weather condition
7. Form work – IS 14687
8. Admixtures – IS 9103
9. Material – Cement
Steel
Aggregates, water Conforming to
Bricks and other materials. relevant IS specifications
10.Quality of concrete is indicated in terms of strength. Impermeability,
homogeneity durability etc. Out of these compressive change is used to
define the acceptance criteria for concrete.
11.Durability of concrete: Main factors influencing durability are
1. The Environment
2. Cover to embedded steel
3. Type and quality of constituent of materials
4. Cement content water cement ratio of concrete.
28. 28
5. Workman ship, to obtain full compaction and efficient curing.
6. Shape and size of member
7. The degree of exposure anticipated for the concrete during its service
life.
8. Concrete Mix – Design Mix and Nominal Mix.
QA QC
Making sure the quality of a product is
what it should be
A highway agency responsibility.
Includes QC
Doing the right things.
Motivates good QC practices.
Making the quality of a product what it
should be
A producer/contractor responsibility
A part of QA
Doing things right
Motivated by QA and acceptance
procedures.
30. 30
Cement Concrete Road (Rigid Pavements)
1. Cement concrete pavements are relatively thin slabs laid directly
over soil sub grade or over sub base course. Stresses are caused in
cement concrete pavements due to wheel loads, seasonal variation in
temperature, changes in moisture content are other factors.
2. Warping stresses are introduced in CC pavement slab due to
temperature variation between the top and bottom of slab during 24hrs
of day.
3. Variation in temperature during different season of the year causes
expansion and contraction of the CC pavements are friction stresses
are developed at the bottom of the slab.
4. Compressive stresses are developed due to friction during
expansion and tensile stresses are developed during contraction of
slab.
31. 31
Design Principle
The principle is generally followed in the design of CC pavement, to
determine the maximum values of warping and load stresses for an
assumed trail thickness of pavement.
Design Strength
Generally the concrete pavement fails due to bending stresses, it is
necessary that the desing is based on the flexural strenght of concrete. The
Mix should be design that minimum flexural strength 45 kgs and modules of
elasticity is 3 x 105
kgs/cm2
32. 32
Flexible Pavement
The flexible pavement are constructed as a multi layer system consisting of
component layers, namely sub base, base course , binder course and surface
course.
Generally sub base course consists of granular materials laid in one or more
layers of same or different materials, depending upon the thickness
requirements.
Base course also consists of superior granular types, using crushed stone
aggregates such as WBM, crusher run macadam (CRM) or WMM, laid in
layers.
Binder and surface course generally consists of layers of bituminous mixer of
different specification.
As the lower pavement layers are subjected to lesser magnitude of stresses,
materials of lower strength could be made use of in the lower pavement layers.
Superior pavement layers which could with stand higher stresses and also
wear and tear due to traffic and environmental factors are used in upper layer.
33. 33
The overall performance of a pavement depends on the quality of construction
and the materials used for constructing the sub grade.
Construction operation:- The important operation are setting out, compacting
the natural ground supporting sub grade. Spreading materials in layers
compaction.
Granular Base and sub base:
The sub base and base course layer of flexible pavement is constructed with
materials to get higher CBR values materials like gravel, mourum, sand or
crushed stone are used. Base course are constructed using water bond
macadam/WMM/CRM specification. Stabilization techniques are also adopted
to construct sub and base course.
Granual Sub Base: (GSB)
Materials to be used for this work should be natural sand, mourum, gravel,
crushed stone or a combination depending on the grading required.
Water Bound Macadam (WBM)
WBM is one of the most commonly adopted specification for base/ sub course.
It is also often adopted as wearing course for low traffic volume roads. WBM
consisting of clean crushed aggregate mechanically interlocked by rolling and
bound together.
34. 34
Binding Material:- Binding material is used as a filler material for preventing
raveling, plasticity index value of binding material shell be less that 6.
Generally for 75 mm thick WBM layer, quantity of binding material required
would be 0.06 to 0.09 m3
per 10 m2
area and 100 mm thick 0.08 to 1.00 cum
per 10 m2
area
Note: In case of structure over soft higher compressible soil and organic fills
often requires that the weak ground be completely removed and replaced with
the selected earth.
Soil also can be treated to improve the properties.
35. 35
Key Factors to improve quality
1. What to Achieve:- Timely progress of construction along with the desired
level of quality.
2. How to achieve:- Methodology, work man ship, testing controls.
3. Who to Achieve:- Responsibilities of individual / organization/parties to the
contract.
Achievement of quality involves
1. Motivation
2. Committement
3. Professional Pride.
38. 38
GENERAL DESIGN CONSIDERATION
AIM OF DESIGN
Aim of design is to provide a safe and economic structure complying to the
users requirement.
METHODS OF DESIGNS
Structure and structural elements shall normally be designed by limit state
method. Calculations alone do not produce safe. Serviceable and durable
structures, suitable materials, quality control, adequate detailing and good
super vision are equally important.
DURABILITY, WORKMANSHIP AND MATERIALS
It is assumed that the quality of concrete, steel and other materials and the
workmanship, as verified by inspections is adequate for safety, serviceability
and durability.
DESIGN PROCESS
Design including design for durability, construction and use in service should be
considered as a whole. The realization of design objectives requires
compliance with clearly defined standards. For materials, production,
workmanship and also maintenance and use of structure in service.
39. 39
LOADS & FORCES
In structural design, account shall be taken of the dead, imposed and wind
loads and forces such as these caused by earth quake, and effects due to
shrinkage, creep temperature etc., where applicable.
DEAD LOADS
Shall be calculated on the basis of unit weights specified as per IS code 1911.
IMPOSED LOADS
Wind loads & snow loads shall be assumed in accordance with IS 875(2), (3), &
(4) respectively.
EARTHQUAKE FORCES
Shall be calculated in accordance with IS 1893, 4326.
SHRINKAGE, CREEP, AND TEMPERATURE EFFECTS
Shall be considered as per IS code 875 parts (5). Design and construction
practices have to be appraised critically in the light of experiences with
structural behavior in recent earthquakes.
40. 40
LOADS & FORCES contd..
ANALYSIS
All structures may be analysed by the linear elastic theory to calculate
internal actions produced by design loads. In lieu of rigorous elastic
analysis simplified analysis as given in 22.4 & 22.5 of IS 456 may be
adopted. With the aid of computer using STAAD PRO evaluation of
analysis and design of members has become simple.
FOUNDATION
Apart from structural systems, the various types of foundation to be
adopted based on the soil characteristics are discussed code of
practices IS 1904-1986 shall be followed for design of size of
foundation.
1. Strip foundation
2. Isolated footing with constant thickness
3. Isolated footing with variable depth.
4. Raft foundation.
41. 41
LOADS & FORCES contd..
DESIGN OF DEEP FOUNDATION
A deep foundation is one which derives its main strength and stability
from the depth of foundation and it is classified into
1. Pile foundation – IS 2911 cast in situ / pre cast piles.
2. Well foundation
FOOTINGS
Footings shall be designed to sustain the applied loads moments and
forces and the induced reactions and to ensure that any settlement
which may occur shall be as nearly uniform as possible, and the safe
bearing capacity of the soil is not exceeded. (IS code 1904).
MOMENT AND FORCES
Bending moment at any section shall be determined by passing
through the section a verified plane, which extends completely across
the footing and compacting the moment of the forces acting over th
entire area of the footing on one side of the sad plane.
42. 42
LOADS & FORCES contd..
SHEAR AND BEND
a. The critical section for this condition shall be assumed as a vertical section
located from the face of column, pedestal at a distance equal to the effective
depth of footing for footings on piles.
b. Two way action of the footing, with potential diagonal cracking along the
surface of truncated cone or pyramid around the concentrated load.
COMPRESSION MEMBERS
Column is a compression member, the effective length of which exceeds three
times the least lateral dimension
A compression member may be considered as short when the slenderness
ratio lix and ley are less than 12.
D b
Lex = effective length in respect of the major axis.
D = Depth in major axis.
Ley = effective length in respect of minor axis.
B = width of member.
49. 49
LOADS & FORCES contd..
MINIMUM ECCENTRICITY
All columns shall be designed for minimum eccentricity equal to the
Un supported length of column + lateral dimension
500 30
Subject to a minumum of 20mm
SHORT AXIALLY LOAD – MEMBERS IN COMPRESSION
The members shall be designed by considering the assumption when the
minimum eccentricity does not exceed 0.05 times the lateral dimension, the
members may be designed by the following equation.
Pu = 0.4 fck Ac + 0.67 fy Asc
P = Axial load on the member
Fck = characteristic strength of compression reinforcement
Asc = Area of longitudinal steel for columns.
Members subjected to combined axial load and uniaxial bending using sp 16
design aids for reinforced concrete to IS 456.
50. 50
LOADS & FORCES contd..
AS SUGGESTED BY BRESLER SUCH MEMBERS MAY BE
DESIGNED BY THE FOLLOWING EQUATION
(Mux)Ln + (Muy) Ln < 1.0
Mux 1 Muy1
Mux, Muy = Moment about x and y axes due to design loads.
Mux1, Muy1= Maximum uniaxial moment capacity for axial load of pu,
bending about x and y axes respectively.
Ln = Related to pu/pu2
Pu2 = 0.45 fck Ac = 0.75 fy Asc
Ln = pu = 0.4 fck Ac + 0.67 fy Asc
pu2 0.45 fck Ac + 0.75 fy Asc
MINIMUM REQUIREMENTS IN COLUMN
The cross sectional area of longitudinal reinforcement shall be not less
than 0.8% nor more than 6% of gross sectional area of column. Max
percentage of steel may be limited to 4% to avoid problems.
51. 51
HIGH RISE BUILDINGS
1. INTRODUCTION:- In metropolitan cities, where the pressure on land is rapidly
increasing due to rapid growth of industry and trend towards urbanization, vertical
expansion is the only answer. Multi storeyed buildings lead to greater
coordination. Between various departments and their efficient functioning.
General principles of planning and design of multi storayed have been discussed.
2. TYPES OF CONSTRUCTIONS
1. Conventional/RCC/Steel frames
2. PSC
3. Composite construction
3. SITING AND ORIENTATION OF MULTI STOREYED BUILDING
4. STURCUTURAL PLANNING: The planning of high rise buildings commence with
the evolution of geometric layout consistent with functional utility and the site
dimension and number of floors permission.
1. Buildings frames with exterior bracing for lateral loads.
2. Interior bracing with core walls.
3. Isolated columns.
4. Share walls
5. Staggered wall beam
6. Shear walls acting with frames
7. Single framed tube
8. Tube in tube
1. Inner tube formed by core walls and outer tube formed by closed spaced
columns and spandrel beam grid.
52. 52
5. CHOICE OF MIX
6. PRELIMINARY DESIGN OF RCC FRAME
7. DETAILED DESIGN OF RCC FRAME
1. Especially the wind & seismic loads have a tendency to cause over turning of
the sturgure and local bending moment on the columns.
2. The over turning effect will cause additional compressive force in the
columns on the leeward sides.
3. The duration of seismic loads may be few seconds and duration gust wind is
less than five minutes.
4. Probability of simultaneous occurrence seismic and wind is conservable less.
53. 53
1. EXPANSION JOINTS
1. CONCRETE
2. INSITU/RMC:- Ready mix concrete as per IS code 4926 approved by the
authority. Concrete is produced from centralized computer/controlled
batching plant that monitors weigh batching, water cement ratio, dosage of
admixture, moisture content etc., with precision, whereas the quality of site
mixture concrete is largely dependent on manual operation.
3. FORM WORK
4. ASSEMBLY OF REINFORCEMENT
5. CONCRETE OPERATIONS
6. FACILITIIES
1. PROVISON OF LIFTS
2. AIR CONDITIONS
3. WATER SUPPLY
4. SANITORY INSTALLATIONS
5. DRAINAGE PROBLEMS
6. WATER PROOFING OF ROOFS
7. SAFETY PRECAUTIONS
8. FIRE SAFETY PROVISION: For all tall structures a control room in the
entrance floor of buildings will communication system to all floors,
facilities to receive message from different floors, details of flour plan
along with details of fire fighting equipment shall be maintained in the
control room.
54. 54
Introduction to Seismic
1. Earth quake is a physical phenomenon caused by the shaking of ground.
2. The engineer needs to know the character and magnitude of forces reloaded
during earth quakes in order to design and construct structures which will realised
such forces.
3. Earth quakes result from the structural charges in the crust of the earth-called
tectonic the shock is usually due to sudden local failure in the crust by overstress.
4. Earth quakes are designated as
1. Shallow-@ depth less than 70 km
2. Intermediate-@ 70 to 300 km
3. Deep-@300 to 700 km below earth surface.
55. 55
Seismic Design
1. Seismic design and their application in construction practice have contributed a
positive sense of confidence with which to face the problem.
2. A structure is designed to resist the vertical acceleration 1g by virtue of its weight
only.
3. As such most of the seismic designs take into consideration only the horizontal
component of ground acceleration due to an earth quake.
4. Codes use the lateral stress formulae for arriving add stresses, that are likely to
disturb the structure during a shock.
5. Magnitude of lateral stresses would be a function of numbers of factors.
1. The ground acceleration due to an expected shock during the design life of
the project.
2. The weight of the structure.
3. Type of constructions.
6. During an earth quake, when the ground tends to move in one direction, the
lateral force exerts a shearing effect on the building above and hence referred as
“base shear” base shear force = F= a/g.W, Where a = (ground acceleration)
values (0.5 &0.02), g= Acceleration due to gravity, w=weight of the structure.
7. The total horizontal shape at each floor level is equal to seismic coefficient
multiplied by total dead loads plus design live road on the floors above the one
under consideration.
56. 56
General guidelines to minimize the risk of building foundation.
1. Structures built on loose soil/weak rocks will have to withstand greater risk
compared to founded on solid bed rock. This is due to that soil particles undergo
a lot of compaction during seismic shocks there by causing settlement.
1. Generally structures built on soft ground soil suffered damage many times
more than similar structures on hard rocky foundation.
2. Structures standing on alluvial soil received greater shaking due to lower
elastic modulus of soil than rock.
3. It is a fact that short buildings on rock, tall building on deep alluvial soil may
exhibit a very large amplification of ground motion in the structure causing its
damage or even collapse.
2. Foundation should be excavated to same level as far as possible continuous
types.
3. Super structure should be thoroughly tied up with the foundation by introducing
keys/ reinforcement to offer max, resistance against sliding at that level.
Roof
1. Minimize the lateral stresses
2. Projection beyond the roof level should be altogether avoided or kept minimum.
General
1. All the parts of same building- The foundation, super structure and the roof
should be firmly tied together so that entire structure act as a unit during a shock.
2. Uniform height should be given to structure.
3. Architectural fancies, cantilevers, arches and domes should be avoided.
57. 57
Behavior of concrete structures
1. Ability of the structure to sustain large deformation.
2. Rigid structure attracts higher loads than a flexible structure under seismic
condition.
3. Concrete being brittle is incapable of sustaining large deformation without
correctly detailed steel reinforcement.
4. Basic principle of earth quake resistant design is to ensure ductility (ability to
deform without rupture) of structure to absorb large deformation without damage.
5. Ductility of concrete structures can be ensured by proper Detailing the
reinforcement as per the relevant codes IS 4326 -1993.
6. Structure should be constructed to the standard specification.
7. Trained persons to be preferred for construction
Strong column and Weak Beam concept
When structure is subjected to lateral loads, as in case of wind or earth quake
forces, its behavior is governed not only by strength of beam column, but also by
capacity of beam column joints to sustain large lateral deformation.
58. 58
Foundation
1. Shallow footing, weaken their seismic resistances.
2. Uneven settlement of footing due to ground movement, especially at
shallow depth, may lead to primitive structural failure.
3. Multi storeyed structures with cellar, (under ground) may survive earth
quake better than those on shallow isolated footing.
4. Best way of building earth quake resistant structures is proper super
vision at every stage of planning, design and construction.
Certain aspects to be appraised for construction practices
1. Foundation (isolated footing)
2. Detailing (beam column, joints, stress reversal, ductility)
3. Planning (floating and staggered column, location of lift wells & cellar)
4. Restriction on structural heights
5. Spaces around structures to avoid sequential collapses.
6. Building materials
7. Stilt floors
8. Water tank on roof top
9. Masonary structures (load bearing walls / infills)
60. 60
MIX UP OF BARS
ELEVATIONELEVATION
PLANPLAN
ELEVATIONELEVATION
PLANPLAN
61. 61
STAGGERING BARS FOR CONTINUITY
IN COLUMNS
NOTENOTE::
ALTERNATIVELY IF STAGGERING IS NOT DONE, SPACING OF TIES SHALL BEALTERNATIVELY IF STAGGERING IS NOT DONE, SPACING OF TIES SHALL BE
REDUCED TO HALF THE NORMAL SPACING IN THE LAPPING REGION.REDUCED TO HALF THE NORMAL SPACING IN THE LAPPING REGION.
88. 88
BENDS, HOOKS AND LINKS
VARIOUS FORMSVARIOUS FORMS
OF LINKSOF LINKS
STANDARD BENDSSTANDARD BENDS
AND HOOKSAND HOOKS
89. 89
BEAM STIRRUPS
SINGLE LEGSINGLE LEG
DOUBLE LEGDOUBLE LEG
OPEN TYPEOPEN TYPE
DOUBLE LEGDOUBLE LEG
PARTIALLY OPENPARTIALLY OPEN
TYPETYPE
DOUBLE LEGDOUBLE LEG
CLOSED TYPECLOSED TYPE
DOUBLE LEGDOUBLE LEG
WELDED TYPEWELDED TYPE
MULTIPLE TYPEMULTIPLE TYPE
90. 90
ANCHORAGE FOR BEAM BARS
ANCHORAGE LENGTH
M 15 M 20 M 25
TENSION 50 x d 45 x d 40 x d
COMPRESSION 45 x d 40 x d 35 x d
Contd……
92. 92
REINFORCEMENT AT BEAM TO
BEAM SUPPORT
HORIZONTALHORIZONTAL
LOOPSLOOPS
EXTRA DIAGONALEXTRA DIAGONAL
OPEN STIRRUPSOPEN STIRRUPS
93. 93
TYPICAL DETAILS OF BEAM
INTERSECTIONS1. SECONDARY BEAM SHALLOWER
THAN MAIN BEAM
2. BOTH MAIN AND SECONDARY
BEAMS OF SAME DEPTH
3. BOTH MAIN AND SECONDARY
BEAMS OF SAME DEPTH
4. SECONDARY BEEM DEEPER
THAN MAIN BEAM
95. 95
DIFFERENT TYPES OF
TIES
SINGLE TIE DOUBLE TIE
DIAMOND TIE +
SINGLE LINK
DOUBLE TIES
SINGLE TIE +
DOUBLE LINKS
SINGLE TIE +
DOUBLE LINKS
SINGLE TIE +
DOUBLE LINKS
SINGLE TIE +
SINGLE LINK
NOTE:
1. TIE DIA :
¼ BAR DIA
2. TIE SPACING :
16 x BAR DIA
48 x TIE DIA
116. 116
CONSTRUCTION JOINT AT
BEAM - COLUMN
JUNCTION
- PERMITTED ONLY WHEN
CONCRETING OF
TAKEN UP IMMEDIATELY
AFTER CONCRETING
- INDICATES DIRECTION
OF CONCRETING
A
B
118. 118
PERMITTED ONLY WHEN
1. SHEAR RESISTANCE OF CONCRETE IS NEGLECTED.
2. INTERFACE TREATED AS HIGH IN THE DESIGNS AND
3. ADEQUATE DEVELOPMENT LENGTH OF
PROTRUDING REINFORCING BARS ENSURED.
- INDICATES DIRECTION OF CONCRETING
CONSTRUCTION JOINT AT
BEAM - COLUMN
JUNCTION
132. 132
1. Lateral loads (i) Wind loads
(ii) Earth quake loading
2. Serviceability (i) Lateral deflection of structures is lateral drift which is the
relative magnitude of lateral displacement at the top of
building with respect to its height.
(ii) Relative vertical deflection:
a. Thermal expansion/constraction of exterior column
b. Different axial load stresses in column and shear cores
leading to creep deformation of members.
c. Differential settlement of foundation for shear core and
adjacent columns
Structural systems (i) Frame buildings
(ii) Shear wall buildings
(iii) Staggered wall beam systems
(iv) Shear wall acting with frames
(v) Single framed tube
(vi) Tube – in – Tube
Frame In a framed type structure, the lateral displacement (drift) may be
two parts
• Due to bending in the columns and beams
• Due to axial deformation of columns.
STURCTURAL SYSTEM UNDER LATERAL LOADS FOR HIGH RISE STRUCTURES
146. 146
No structural maintenance should be necessary for dense
concrete constructed in accordance will the CODE OF
PRACTICE
CRACKS:-
1. For example if cracking is observed, one must be able to
distinguish between, cracks due to
1. overloading of properly designed structure or
2. caused by the structure being inadequately strong and on the
other
3. cracks induced by corrosion of reinforcement
4. by chemical action or by thermal effect
2. It is possible that the observed cracks are due to changes in
temperature/or /moisture, combined with restraint of deformation.
3. Also the cracks are stable, old cracks due to earlier shrinkage or
to initial thermal stress.
4. The water tightness of concrete is breached by weathering and
loading effects during the first stage.
5. Durability of concrete is a holistic criteria, depended not only on
environmental exposure condition but also on structural design
parameters, characteristics of concrete – making materials, mix
proportion, and concrete processing methods.
147. 147
PHYSCIAL CAUSES OF DETERIARATION
1. Loss of mass means due to abrasion, erosion, or cavitations.
2. Cracking due to normal temperature and humidity gradients, structural
loading, and exposure to temperature expresses such as frost action/fire
3. Structural cracks at early ages generally arose due to shrinkage strains
from cooling or drying.
4. Thermal shrinkage is of greater importance in large concrete elements.
CHEMICAL CAUSES OF DETERIEARATION
1. Hydrolysis of components of cement
2. Cation exchange reaction between aggressive fluids and cement paste.
3. Reaction involving the formation of expansive products.
SUPLHATE ATTACK
1. Degradation of concrete as a result of chemical reaction between
hydrated Portland cement are sulphate ions from an extreme source can
manifest in the form of expansion and cracking or progressive loss of
cohesiveness and strength of concrete
CORROSION OF REINFORCING STEEL
Deterioration of concrete due to corrosion of embedded steel manifest
itself in form of expansion, cracking and loss of cover. Loss of steel
concrete bond, and leaks to structural collapse. It occurs as a result of
electro chemical process.
148. 148
RCC Containing discontinuous
Cracks, micro cracks and pores
Increase in permeability Through inter
connected Cracks, micro cracks and
pores
1. Expansion of concrete due to increase
hydraulic pressures in pores caused by
a. corrosion of steel
b. sulphate attack on cement paste
c. alkali attack on aggregates
d. freezing of water
2. Reduction in concrete strength and
stiffness
Environmental action stage 1
1. Humidity & temperature
gradients
2. Cyclic loading and impact
loading
Environmental action stage ii
1. Penetration of water
2. Penetration of air
3. Penetration of acidic ions
gases, co2, cl, so4, so2,
No2
Cracking, spelling and loss
Of mass
A HOLISTIC MODEL OF CONCRETE DETERIARATON & ENVIRONMENTAL
EFFECTS
150. 150
SNO TOPIC DETAILS SUBTOPIC
1 Introduction - a. pcc & rcc
2 Design a. Workability, Durability,
Shrinkage
b. Mix Design
a. Grades of concrete
b. Design and Normal
Mix
c. Ready Mix Concrete
d. IS 10262
3 Materials a. Cement,
Aggregates,
Water
a. OPC 33,43,53
grades
PPC
IS 383
IS 456
4 Formwork a. Introduction a. Types of Form work
(Timber form, steel
forms, moving forms,
climbing forms)
b. Materials
c. Design of formwork
d. Striking period
151. 151
SNO TOPIC DETAILS SUBTOPIC
5 Production a. Production and
control
b. Transporting,
placing,campacting,
curing
6 Standards a. Tests ,
Analysis
Reports
IS 516
IS 1199
152. 152
Introduction:
Engineers have been designing these structures primarily on strength
and behavior considerations till recently. The life of a structure
depends upon the inherent strength, further there are other
considerations to be given due importance to have satisfactory service
during the expected life of the structure. Durability and life expectance
of a structure. Durability and life expectance of a structure depends
upon quality of basic materials used in the construction, relative
proportions of the components such as water, cement, aggregate and
admixtures and methods of construction.
Concrete is basically meant to last for ever without any major repair
and maintenance. However, deleterious agents in the environment or
in the ingredients itself often leads to premature deterioration of
concrete structures. Timely action in mitigating the distress
phenomena through repair and rehabilitation is essential fo sustaining
performance of such structures.
153. 153
Factors influencing the durability of concrete members.
One of the main characteristics influencing the durability of concrete it
its permeability to the ingress of water, oxygen, carbon dioxide,
sulphate, etc., with normal weight aggregates. A suitable low
permeability is achieved by having an adequate cement content, low
water cement ratio, by ensuring complete compaction of concrete and
by adequate curing.
The factors influencing durability include.
1. The environment
2. The cover to embedded steel
3. The type and quality of constituent materials
4. Cement content and w/c ratio of concrete
5. Workman ship, to obtain full compaction and efficient curing
6. Shape and size of members.
Concrete is more vulnerable to deterioration due to chemical or
climatic attack when it is in thin section. The life of the structure can
be lengthened by providing extra cover to steel, by chamfering the
corners or by using circular cross sections or by using surface coating
which reduce the ingress of water, carbon dioxide, etc.
154. 154
Check list of every activity involved in design, detail, execution,
supervision, quality/cost control etc., goes a long way in reducing the
chances of repetitive mistakes.
Construction
Construction is equally important as design and planning. One has to
follow the design and specifications to ensure good of work and
thereby ensuring durable structure. The construction engineer should
have a practical approach by proper supervision at site for quality
assurance and by following specifications. Etc.,
Seepage/leakage in buildings and their controlling methods
Excessive dampness in buildings is one of the major problems in
recent years. If such seepage/leakage is allowed to continue
unchecked, unhygienic conditions will prevail and also the building
may deteriorate to the extent that ultimately it becomes uninhabitable.
The source of seepage/leakage can be rain water, leakage in pipe lines
condensation or ground water.
155. 155
Spalling of concrete
This is a common problem being faced by the maintenance engineer.
Spalling of concrete causes in convenience, shabby look and more
affects the durability of structure.
Some of the reasons for spalling of concrete are as follows.
Defective design
1. Improper diameter of reinforcement bars
2. Use of substandard materials
3. Poor quality of construction
4. High water cement ratio
5. Seepage/leakage
6. Inadequate cover to reinforcement bar
7. Corrosion of steel
8. Lack of water proofing treatment in areas like terrace, sunken slab,
basement
9. Lack of external treatment for exposed concrete surfaces
10.Environmental conditions
11.Neglected maintenance.
156. 156
Large number of destructive and non destructive tests are available
to assess its state of concrete and techniques are also available to
combat various deteriorating causes.
Corrosion of steel
Corrosion of steel reinforcement in concrete structure is a common
phenomenon which require utmost attention. This occurs because
of in efficient design/drafting and poor construction. The other
reason for corrosion is seepage/leakage. Concrete with its inherent
porosity renders reinforcing steel susceptible to corrosion.
157. 157
To avoid corrosion of reinforcement, special care has to be taken
regarding the following:
1. Design mix
2. Water cement ratio
3. Grading of concrete
4. Cement content.
5. Quality cement, aggregate, water
6. Covert to reinforcement
7. Compaction, admixtures
8. Treatment to exposed surfaces
9. Environmental conditions.
Therefore, it is suggested that the dampness which is the main cause for
corrosion should be avoided by good design and quality construction to
achieve dense concrete.
158. 158
Rehabilitation of concrete structures.
All concrete structures deteriorate sooner or later. Deterioration
could be caused due to anyone or the combination of the following
factors.
1. Cracks
2. Structural deficiencies
3. Dampness
4. Spalling of concrete
5. Corrosion of reinforcement
6. Chemical action
7. Frost damage
8. Environmental conditions
Different admixtures are being used to take care of the various
factors to have a durable structure.
159. 159
Conclusions
However good the mix, the concrete in the structure will be good only if al
the concreting operations have been well executed. The structure has to be
properly designed, not only from the point of view of strength, but also with
respect to exposure to the local conditions.
Detailing of concrete members
Detailing of reinforcement plays a significant role in the performance of
concrete structures, including their long term behavior.
Detailing forms an important aspect of design of concrete structures. In
most cases, structural distress is not because of in accurate analysis or
design but due to improper or inadequate layout of reinforcement.
Reinforcement layout.
Proper layout of the reinforcement should be evolved. The layout should
take into account the strength and durability requirement as well as
economy of construction.
160. 160
Anchorage Reinforcement
Any bar subjected to stress to be anchored adequately beyond the
section at which it is required to develop the reqiured force. The
average length is usually expressed as a function of bar diameter. Ld
Anchorage of Reinforcement
Longitudinal bars should be anchored adequately beyond the face of
support in order to develop to required force in the post elastic stage
as well support requires offer transverse compressive stress which
has an effect on bond stress and thus require smaller anchorage
length compared to other region. Direct supports (walls or columns)
generally require smaller anchorage length than indirect support (inter
connected beams)
End supports
At least a third of longitudinal bars required for span moment in
beams or slabs provided with shear reinforcement should continue
beyond face of simple support or end support.
161. 161
Stirrups
Stirrups are designed to resist tensile stresses due to shear. The
vertical bars or stirrups must be anchored adequately in the
compression zone and be able to develop full tensile force without
excessive deformations.
Splicing of Reinforcement
Lap splices are used widely as an economical means to ensure the
continuity of the reinforcement. Reinforcement bars should be detailed
properly to transfer the forces from one set of reinforcement to
another without causing cracking in the surrounding concrete.
Slabs
Slabs are the most common structural elements and require simple
layout of reinforcement for usual case. Eg. One way two way slabs
under uniform distributed loading. Variation of bending moments in
slab permits curtailment of bars away from critical section.
162. 162
Beams
Bar size in beam should be small enough to restrict bond stress and prevent
spalling of concrete but large enough to provide adequate space for concrete to
flow.
Longitudinal bars
Codes of practice specify the maximum bar sizes and minimum spacing. If the
reinforcement in a beam is provided in more than one layer, they should be laid
exactly over one another to prevent sieve effect leading to honey combing. Bar
spacing should be adequate for concrete to flow, and for needle vibrators to
penetrate lower layers.
Additional web reinforcement
It is advisable to provide additional longitudinal bars along the depth of web if
the tension zone is deeper than about 50mm. In the absence of such
reinforcement some of flexural cracks that develop at eh beam soffit merge
together to form wider cracks at a bout mid height of web instead of stopping at
the level of tension bars. Additional bar of 10mm dia bars should be provided
on both sides of the web.
163. 163
Reinforcement in beam flangers
Adequate transverse reinforcement should be provided in the flange of T and L
beams to resist transverse tension. It is necessary to spread the tension
reinforcement in the flanges, and not concentrate in webs in order to reduce
cracking in flange.
There should be at least two bars within the web spaced not more than 200mm
for effective anchorage.
Beam column joints.
Joints are often are the weakest parts in a structural system. Improper detailing
of joints such as frame corners, may lead to premature failure of structures at
loads smaller than the design capacity of members. Obviously the joints should
be so detailed that they do not fail before the capacity of individual members I
exhausted. Detailing should be simple and permit proper compaction of
concrete.
Large radius of the bend bars reduces the lever arm and the flexural capacity of
concrete. It may also result in spalling of outside concrete. In such a case,
supplementary right angled bars may be added to protect the integrity of the
corner concrete outside the bend bar.
164. 164
Columns
Columns are predominantly subjected to compressive stresses. Longitudinal
reinforcement in column is provided not only to sustain compressive forces, but
also to withstand torsional and longitudinal moments, particularly due to creep
and shrinkage. Transverse reinforcement plays a significant role in controlling
cracking in columns and in ensuring ductile behavior. Longitudinal
reinforcement should not generally exceed 4% in order to avoid congestion
especially at splices.
It is usual to provide splices for columns bars at floor levels. However this
practice is not suitable for structures prone to earth quake loading. The region
of columns close to floor levels in the zone of potential plastic hinge formation.
Thus splices should be provided in the mid height of regions of columns, where
the bending moments are minimum. The splices of reinforcement in column
prone to earth quake forces are restricted to the middle half of column.
177. 177
PRINCIPLES OF MIX DESIGN
The important principles of Mix Design are broadly mentioned below:-
Design Requirements
1. Grade of concrete - M2O
2. Type of cement - OPC- 33, 43, & 53
PPC
3. Type & Size of aggregate - IS 383
[ natural sand, crushed stone]
4. Nominal maximum size of aggregate 40 mm/20mm/10 mm (IS 383)
5. Max/Min Cements content - Required for durability
consideration kg/m3
6. Type of mixing & curing water - Fresh portable washed/bore to be
used.
7. Max free water cement ratio by weight – Required for consideration of
strength/durability for different
exposures.
8. Degree of workability of concrete - Dependent on placing and
compacting condition
9. Air content - Inclusive of entrained air
10.Type of admixture used
11.Max/Min density of concrete
178. 178
12.Max/Min temperature of fresh concrete
Mix should be designed to obtain the concrete having desired durability,
workability, comparison strength not less than for the particular grade.
Design of Mix is carried out as
1. Determination of physical properties of concrete ingredient
1. Specific gravity of cement and aggregate
2. Gradation of aggregate
3. Compressive strength of cement
2. Estimation of w/c ratio
3. Selection of water content and ratio of fine aggregate to total aggregate (by
absolute volume)
4. Determination of quantities of various ingredient for one cubic meter of
concrete.
V=(W +c/sc + 1/p. Fa/SFa) 1/1000
V=(W + c/sc + 1/(1-p). Ca/SCa) 1/1000
V= Absolute volume of fresh concrete which is equal to gross volume (m3
)
minus volume of entrapped air)
W=Mass of water (kg) per m3
of concrete
C= Mass of cement (kg) per m3
of concrete
Sc=Specific gravity of cement
P=ratio of fine aggregate to total aggregate by absolute volume.
179. 179
Fa,Ca = Total mass of coarse aggregate (kg) per (m3
) of concrete.
SFa,SCa= Specific gravities of saturated surface dry fine aggregate and coarse
aggregates
Next Step:- Casting of Mixes
While casting , workability, compaction factor density and air content
are assessed.
Next Step:- Compressive strength of concrete 28 days age.
Next step:- Plot the for c/w ratio and average compressive strength of cube.
From the graph select c/w ratio for the required target strength and
quantities of various ingredient are worked out.
Target strength = Fck = Fck + 1.65 S
Where S= standard deviation (IS Code)
Fck = Characteristic strength @ 28 day
Fck = Target average compressive strength @ 28 days
180. 180
CONCRETE MIX DESIGN FORMAT BY TRAIL MIX METHOD
Example: Mix M20 Grade:
I.
1. Characteristic strength of concrete (fek) - 20 N/mm2
@ 28 days
(Target mean
strength to be
achieved)
2. Cement Type - OPC
3. Aggregate Type : 20 mm - Crushed
10 mm - Crushed
4. Fine aggregate - Course sand
5. Free Water cement ratio - 0.50
6. Max.free water cement ratio - 0.50
II.
1. Maximum aggregate size - 20 mm
2. Free water content - 160 Kg/M3.
181. 181
III.
1. Water content - 160+ 0.50
2. Minimum Cement content - 160 = 320 kg/M3
0.50
IV.
Relative density of aggregate:
1. Concrete Density = 2400 kg/M3
2. Total aggregate content = 2400-320-160+1920 kg/M3
V.
Grating of Fine aggregate percentage passing 600 – Um sieve = 60%
1. Proportion of Fine Aggregate: = 27%
2. Fine aggregate content : 1920 x 0.27 = 528 Kg/M3
3. Course aggregate content : 1920 – 528 = 1392 Kg/M3
Quantities: Cement Water Fine Course Aggregate
Per Cum. Kg. Aggregate 10mm – 20 mm
Trial Mix 320 Kg. 160 Kg. 528 Kg. 487 Kg. 905 kg
(35% + 65%)
182. 182
BUILDING MAINTENANCE, COMMON
DEFECTS AND REMEDIAL METHODS
Maintenance plays a vital role in the execution of buildings. Very often difficult problems
are encountered in the maintenance of building than in original work.
1. Every aspect of maintenance has to be carefully thought out in its entirety aiming at over all
sound ness of structure in all the seasons of the year. Most buildings may develop cracks
usually soon after construction and sometimes later. Much of the early cracking is
superficial, can be easily repaired.
2. Several factors contribute in producing defects. Before repairs or remedies are sought, one
needs to know the causes of cracking and its effects on the performance of the buildings.
3. Timely action in mitigating the distress phenomena through repair and rehabilitation is
essential for sustaining performance of such structures. Concrete is basically meant to last
for ever without any major repairs and maintenance. However deleterious agents in the
environment itself often leads to premature deterioration of concrete structures.
4. Cracks in buildings are common occurrence. A building component develop cracks
whenever stress in the component exceeds its strength.
183. 183
5. Durability can be achieved by proper maintenance. Therefore maintenance is
equally important as design and construction stages. But, maintenance is
always given a least importance. The importance given to planning and
execution of project is missing in maintenance activities. The more efficient
maintenance results in increase in life of structure and creates good image of the
society. The various problems in maintenance are occurring due to inefficient
design/planning and bad quality of construction. The designer shall use the best
quality of materials by which reduce maintenance problems. Most of the problems
in maintenance are repetitive type and directly affect the durability of structure.
Some of the problem are seepage/leakage, spalling of concrete and corrosions of
steel.
6. Principal causes of occurrence of cracks
1. Forces like Dead, Live, Wind, Seismic etc.
2. Foundation settlement
3. Moisture changes
4. Thermal variation
5. Chemical reaction etc
6. Poor workman ship
185. 185
1. Foundation:
a) Engineers need to know the character and magnitude of forces in order to design and
construct structures.
b) One has to study the system of soil below the earth surface at various levels under
ground depending upon the past experience.
c) Repairs to foundations are expensive. Structures should be founded as stable soils.
d) Certain soil deposits wherein wetting of the soil beyond a stress level causes steep
reduction in stiffness resulting from disruption of soil structure.
e) Subject to rate of loading, disruption in soil structures takes place at a faster pace than the
development of new structural bonds which leads to vertical deformation at locations of
higher stress due to disturbance of soil structures.
f) Problems associated with foundation in clay soil are well known. Swelling clays create
large uplift forces on the peripheral wall during rainy season. A reverse situation may
arise at region of moderate rainfall when the central region of a building founded an
clay soil is prone to swelling during dry spells.
a) Differential settlement due to unconsolidated fill.
b) Differential settlement due to uplift of shrinkage soil, shrink and expand with
changes in moisture content. Vertical and diagonal cracks are noticed in external
walls.
g) The problems of dampness in building requires a systematic approach to determine the
causes of leakage, the source from which are likely to prove effective.
186. 186
2. Walls
Walls are constructed using a variety of materials such as mud, stone, clay bricks, concrete
blocks, Fal-G Bricks etc. Common burnt clay bricks as per IS 1075-1951, Bricks shall be
hand or machine molded classifying Class1, Class2 Bricks maintaining characteristics like
water absorption to 20% and Efflorescence slight.
1. Although the walls are built of reasonably non- porous bricks, the mortar itself is
relatively porous and so rain water penetrate into to the mortar and will be finally
sucked up on the inside surface causing discoloration and dampness. The moisture
which was absorbed by the wall tries to escape by break through plaster, which otherwise
reduces the strength of materials in the wall. Porous mortar than water tight mortar for
plaster is advisable.
2. Faulty joints are common cause of entry by rain so that if bricks are adequate for their
purposes, pointing needs to be examined and mortar replaced.
3. Number of causes of failures of brick wall have been reported. High intensity wind causes
masonry walls to collapse due to their in adequate lateral restraint. Quality of bricks
workman ship. Spacing of pilasters, size of wall panels etc. Influence the lateral
resistance of the walls structure.
4. Generally walls constructed with RC columns with in filled brick walls have performed better
during cyclones.
5. Failures of brick masonry walls can be avoided by suitable choice of panel size which in
term would depend on the tensile strength of brick and quality/workman ship. It is advisable
for provide a continuous RC bond beam on top.
187. 187
6. Brick work may become cracked especially at door and window opening as a result of
excessive drying shrinkage. Rich cement mortar rendering, fail because they shrink
and crack. The familiar map pattern cracking is typical of drying shrinkage in
renderings.
7. Cement based mortars may be attached by sulphates derived from clay bricks themselves.
Some times from external sources such as sulphates bearing soils or flue gases. The attack
is gradual and occurs when the brick work remain wet for long periods, which produces
various forms cracking and deformation of bricks.
8. Junction of the concrete lintels and masonry walls and junction of RCC. Sun shades
and walls are vulnerable places for the penetration of moisture, as these two different
materials always give rise to their cracks at the junctions, water dripping on the wall
surface also causes dampness.
9. Finished surface of roof should have a slope of 1 in 80.
10. Special attention should be paid to junction of roofs and parapets, outlets to drain out to rain
water to be properly executed. Every 200 sft of roof areas should be provided with one
outlet.
188. 188
3 Concrete and RCC items
The common problems are
1. Seepage/leakage in buildings and their controlling methods: Excessive
dampness in buildings is one of the major problems in recent years. If such
seepage/leakage is allowed to continue unchecked, unhygienic conditions will
prevail and also the building may deteriorate to the extent that ultimately it
becomes uninhabitable. The source of seepage/leakage can be rain water,
leakage in pipe lines condensation or ground water.
Causes of seepage in building:
Seepage mainly occurs from walls and roof ceiling in buildings.
a) The causes of seepage/leakage through the roof are:
1. Lack of proper slope thereby causing stagnation of water.
2. Lack of proper drainage system
3. Lack of goals, coping etc.
4. Poor maintenance of pipe connection and joints.
5. Poor quality of construction.
b) Causes of seepage/leakage through the wall are
1. non provision of damp proof course.
2. lack of plinth protection
3. lack of chajja, facia over openings
4. poor orientation and wind direction
5. lack of stone cladding/water proof plastering and painting.
189. 189
Seepage controlling methods:
Water proofing treatment is necessary especially for areas like, water tanks, sunken
slabs, roofs, terrace gardens, foundations, planters, service floors, etc., As a
preventive measure in recent years a number of water proofing treatment methods are
being used by making use of different water proofing materials.
1. mud phuska with proofing materials.
2. multi layer asphalt treatment.
3. brick coba treatment.
4. chemical injection treatment.
5. polymer modified bitumen based treatment
6. glass fibre tissue based treatment (7 course)
7. lime based treatment
There are different water proofing methods available for pre and post construction
stages of buildings. By good design/planning constructions and maintenance, the
problem of seepage in buildings can be minimized.
190. 190
Spalling of concrete:
This is a common problem being faced by the maintenance engineer. Spalling of concrete
causes in convenience, shabby look and more affects the durability of structure.
Some of the reasons for spalling of concrete are as follows:
1. Defective design.
2. Improper diameter of reinforcement bars.
3. Use of substandard materials.
4. Poor quality of construction.
5. High water cement ratio.
6. Seepage/leakage.
7. Inadequate cover to reinforcement bars.
8. Corrosion of steel.
9. Lack of water proofing treatment in areas like terrace, sunken slab, basement.
10.Lack of external treatment fro exposed concrete surfaces.
11.Environmental conditions
12.Neglected maintenance.
Large number of destructive and non destructive tests are available to assess its state of
concrete and techniques are also available to combat various deteriorating causes.
191. 191
For repairing such affected areas different materials like cement, polymer, epoxy materials,
polymer modified bitumen are being used. Steps to be taken for repairing the affected areas
as:
1. Remove all loose materials.
2. Clean the areas with compressed air.
3. Remove rust from reinforcement
4. Apply anticorrosive paint.
5. Apply cement/resin/polymer based mortar
Corrosion of Steel:
Corrosion of steel reinforcement in concrete structure is a common phenomenon
which require utmost attention. This occurs because of inefficient design/ drafting
and poor quality construction.
To avoid corrosion of reinforcement, special care has to be taken regarding the following.
1. Design mix
2. Water cement ratio
3. Garding of concrete
4. Cement content.
5. Quality cement, aggregate, water
6. Covert to reinforcement.
7. Compaction, admixtures.
8. Treatment to exposed surfaces.
9. Environmental conditions.
Therefore, it is suggested that the dampness which is the main cause for corrosion
should be avoided by good design and quality construction to achieve dense
concrete.
192. 192
Scope of Investigations/ assessment of structural damage decision of
Restoration.
1. To assess the extent of structural damage to RCC elements of the building
2. To arrive at the residual strength of concrete and reinforcing steel.
3. Report covering the above aspects.
1. Debris inspection
2. Visual inspection of affected members.
3. Institution field testing.
4. Lab test
5. Damage classification of structural member.
Visual: 1. Surface appearance.
a. Condition of plaster/finish
b. Colour
c. Crazing
2. Structural condition.
a. Spalling.
b. Exposure and condition of main reinforcement.
c. Cracks
d. Distortion
e. Construction joint, honey combing, delimitation
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A) Condition of plaster and finish:
RC Members rendered with cement mortar which in general (1:3) may be cladded with other
materials (wood/marble etc.) condition of finishes are categorized as 1) unaffected 2)
peeling 3) substantial loss 4) total loss.
B) Colour of concrete may change as a result of heat due to fire.
C) Crazing: Development of fine cracks on surface of concrete due to sudden cooling of surface
with water is termed as crazing.
D) Spalling of concrete:
E) Cracks
F) Distortion in the form of deformation (deflection, twisting)
G) Honey combing/construction joints: due to original construction defects.
Delamination of concrete means that a layer of some part of concrete has separated out
from the parent body but still not fallen out, Hallow surroundings etc.
Remedial Measures
Hammer test, Core test compressive strength estimation. Based on the severity of the
damage of the structural members, different types of repairs methods are to be adopted to
restore their structural integrity.
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Class-I Superficial For repair, use cement mortar toweling
using cement slurry bonding.
Class-II General Minor structural repairs like restoring cover to
reinforcement using cement based polymer,
modified mortar polymer slurry as bonding
layer and nominal light. Fabric mesh or using
epoxy mortar over primary coat of epoxy
primer.
Class-III Principal Repair Where concrete strength is significantly
reduced strengthing to be carried out with
shot creting. In case of slabs and beam, and
Jacketing incase of columns. Bonding
material shall be epoxy formulation,
additional reinforcement shall be provided
in accordance with load carrying requirement
of member.
Class-IV Major repair Demolition and recasting.
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Material Specification: Relevant to B15 codes
1. Reinforcement: High strength deformed bar IS 1786-1979 and FC 415 Grade. Hard drown
steel wire fabric of 50 x 50 mm mesh size with 3 mm dia wire. Conforming to IS 1566 used
for slabs, beams, column, as requirement for concrete plastering by short crade process.
2. Epoxy formation: Epoxy primer, Epoxy adhesive, Epoxy mortar.
Epoxy grout are used as repair materials.
1. Epoxy resin: Araldiete
2. Hardness : x4 54, Hy825
3. Filler materials: Silica flour. Quartz sand mix No. 10
3. Polymer based Admixures: Trade name: “ Roff Bond Repair”
Cement concrete of jacketing of columns.
Outer layer of concrete with required reinforcement is cast around the existing column, after
necessary surface treatment. The bond between old concrete and newly concrete layer is
ensured with epoxy adhesive and shear key. Mix proposals for concrete for jacketing
process is 1:1:2 nominal mix 1 cement 1 course sand 2 graded stone aggregate (20 mm) to
increase load carrying capacting columns. Micro concrete can be applied.
Jacketing can be with cement concrete of mix (1:1:2)/Micro concrete with suitable mat
of steel, wrapping with woven reinforcing fabric to enhance to axial shear, flexural
tensile strength and durability.
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Cement concrete for shot creting:
Shot crete is cement mortar or cement concrete with course aggregate size maximum 10
mm conveyed through a hosepipe and pneumatically placed under high velocity on to a
prepared concrete or masonry surface. The force of Jet on surface compacts the shot crete
material and produces a dense homogenous mass.
Basically two methods of shot crete.
1. Wet process, 2. Dry Mix process
In west process al ingredients including water are mixed together before they are enter the
delivery house.
In Dry process: The mixture of damp sand and cement is passed through the delivery hose
to the nozzle where water is added.
The dry mix process is generally used in repair of fire damaged structure.
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Repair of cracks
1. Making groove of 12mm x 12mm size along length of cracks using chisel and hammer.
2. Washing the cracks with water under pressure and drying by blowing air.
3. Drilling holes 30mm to 40mm deep at 100mm space along length of cracks and clearing
holes with compressive air.
4. Providing grount parts in drilled holes with 12 mm dia aluminum nipple and sealing to crack
length and fixing nipples with epoxy putty.
5. Preparation of epoxy grant mix in small quantities weighing not more than 1 kg. mixed
thoroughly with a wooden stick in a clear mortar pan.
6. Pressure grouting at (6 to 7 Kg./Sqm.) and sealing the cracks with epoxy grout mix using
pneumatic grouting strong from lower mix and vertical till the grout mixing emerging from
next part. First part is closed and is reported.
Honey combing repair:
By injecting cement grouting through 12mm dia grouting nipple are inserted at 9 Nos/sqm
and upto 30 to 40 mm deep.
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New Materials
Innovative construction chemicals are being marketed in India by different agencies who
also have to technical know how for their application, to repairs of structures, sealing of
cracks in walls and roofs, repairing of defective joints, arresting of leakage in water retaining
structures.
The basic consideration and understanding of the factors responsible for the damage
to buildings is necessary both for correct diagnosis and repair, more important for
minimizing future trouble in new building by good design and good workman ship
“Prevention is better than cure”
