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ACI 318-05 Building Code requirements for Structural Concrete and Commentary
This code I am sharing today defines and explains one by one all the provisions of the American Concrete Institute (ACI) Building Code i.e. ACI 318-08.

ACI Building Code 318-08

This code provides minimum requirements for design and construction of structural concrete elements of any structure erected under requirements of the legally adopted general building code of which this code forms a part. In areas without a legally adopted building code, this code defines minimum acceptable standards of design and construction practice. For structural concrete,  f c′  shall not be less than 2500 psi. No maximum value of f c′  shall apply unless restricted by a specific code provision.

Contents

Introduction
Chapter 1—General Requirements
Chapter 2—Notation And Definitions
Chapter 3—Materials
Chapter 4—Durability Requirements
Chapter 5—Concrete Quality, Mixing, And Placing
Chapter 6—Formwork, Embedded Pipes, And Construction Joints
Chapter 7—Details Of Reinforcement
Chapter 8—Analysis And Design—General Considerations
Chapter 9—Strength And Serviceability Requirements
Chapter 10—Flexure And Axial Loads
Chapter 11—Shear And Torsion
Chapter 12—Development And Splices Of Reinforcement
Chapter 13—Two-Way Slab Systems
Chapter 14—Walls
Chapter 15—Footings
Chapter 16—Precast Concrete
Chapter 17—Composite Concrete Flexural Members
Chapter 18—Prestressed Concrete
Chapter 19—Shells And Folded Plate Members
Chapter 20—Strength Evaluation Of Existing Structures
Chapter 21—Special Provisions For Seismic Design
Chapter 22—Structural Plain Concrete
Appendix A—Strut-And-Tie Models
Appendix B—Alternative Provisions For Reinforced And Prestressed
Appendix C—Alternative Load And Strength Reduction Factors
Appendix D—Anchoring To Concrete
Appendix E—Steel Reinforcement Information
Commentary References
Index

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Treatment of dampness in walls in many ways

Dampness is the cause, reason and initiator of many defects and diseases in all sorts of construction from roads and transport systems to building and housing facilities. It might be a headache for you in rainy season and it might not let you sleep easily because of the danger and consequences of its presence. This post will let you know how to treat if your walls or building is being effected by dampness as well as will give you remedial measure that will ensure safety of your structure from all such devastating defects.

Dampness in walls

Before applying any remedial measure to a damp wall there should be free escape for any water that has already entered in the wall.

Silica Solution is transparent and very effective in resisting dampness.

Internal Treatment of walls 

Internal treatment of affected walls would consist of removing the old plaster, applying a slurry coat of neat cement with a water proofing compound and then cement rendering with a dense mortar, of 1:2 with integral water proofer added.

Another internal treatment for damp walls is the application of an impervious coating of some material or a coating of bitumen or tar followed by blinding with sand and plastering.

Preventing Dampness in walls

The following methods are also used for preventing dampness in walls

a) Two parts by weight of coal tar and one part by weight of pitch are put in a vessel, heated and stirred, until the mixture is sufficiently liquid. It is then applied on walls, and is found to keep out dampness very wall.
b) Spray or paint the walls with a solution of sodium silicate, followed by a solution of calcium chloride, which forms an insoluble silicate.

If dampness is confined to one position near ground floor level above the D.P.C., it may be due to a hole or crack in D.P.C. through which moisture can pass into the wall alone.
Dampness below ground level may be due to lack of sub-soil drainage, absence of vertical D.P.C.

Repelling Materials

Water repelling compounds are mixed in cement to make it water repellant, Examples are;
a) Chemically active ….. sodium and potassium soaps
b) Chemically inactive ….. calcium soaps and resin oils

Concept of Reinforced Earth

Reinforcement in the form of steel or synthetic strips called geo-strips are placed within an embankment, containing soil in various layers compacted mechanically; the granular material of embankment is linked by means of friction. The embankment becomes a self supporting structure, such a structure is called reinforced earth structure.

Earth Reinforced with Geo-strips and Reinforced Earth Panels

Concept

Construction of reinforced earth is a very simple process. The principle concept of reinforced earth is similar to that of a reinforced concrete that contains steel, aggregates and fines. In reinforcing earth process we reinforce the earth by means of steel or synthetic geo-strips.

Stresses that are generated within the embankment is transferred and resisted by these reinforcing strips. 

Concept of Reinforced Earth Works (REW)

History

Constructions using these techniques are known to have existed in the 5th and 4th millenniums B.C. Since early civilizations, man has attempted to use soil with other materials to enable it for being used for his necessities. Typical early use includes us of branches of tree etc. to support tracks over marshy areas and to build hutments. Structures are also built by insects and birds using mud and leaves.  These are all familiar sights even today. This kind of principle is also used in building parts of Great Wall of China and the Babylonian Ziggurats i.e. temples.

Great Wall of China

In the 19th Century Passel used tree branches to reinforce back fills in order to reduce the earth pressure and thereby economize the retaining walls. 

Textile material was perhaps first used in road construction in south Carolina in the early 1930s. The first use of a woven synthetic fabrics for erosion control was made in 1958 by Barrett.

Construction

Reinforced earth system consists of following items;

a) Facing or the skin of the embankment
b) Reinforcing geo-synthetic strips
c) Soil in lifts or layers

During the construction phase we first do a lean within the boundary of embankment upon which the reinforced earth panels or skin of the reinforcement is placed. In this boundary of panels we place the selected material containing fines and gravels in lifts or layers. Each lift is mechanically stabilized by using a roller. We in this case don’t use sheep foot roller or vibratory roller, we use simple steel drum roller to do the compaction as well as ensuring stability of the structure.

The skin or reinforced earth panels have a path or passage for geo-synthetic strips which is called connectors mostly they are in C shape so they are called C-Connectors.

A bridge Abutment

These strips after passing through C-Connector is jointed with a reinforced steel bars placed at center in a specified distance. With each lift the process repeats and as a result we get a well compacted reinforced earth embankment. Water sealant foam is applied between each panels to ensure it as a water tight structure.

Advantages

Following are some of few positivity in Reinforced Earth Works

Reinforced Earth Panels Facing

a) Easy Placement

Construction is repetitive and simple, panels, strips, granular fill and then compaction

b) Positive Connection

Galvanized reinforcing strips are connected to concrete panels with structural bolts

c)    Engineered Backfill

Alternating layer of reinforcing strips and backfill are applied and compacted.

d)   Structural Facing

TerraClass facing panels are easily handled by placement crew.

Defects in Brick Work and their Remedies

"sulphate attack on mortars, unsound materials, frost action, corrosion of iron and steel, crystallization of salts, linear changes resulting from variation in moisture content"

While doing brickwork and after the brick is completed there are certain defects which has to be faced, these defects they must be avoided and remedial measure must be taken. These defects not only ruins the physical quality and aesthetics of the project but also ruins its structural strength. So to avoid any mishap and loss we must know what are certain defects in brick work and how to avoid them. 

Common defects occurring in Brick work are; sulphate attack on mortars, unsound materials, frost action, corrosion of iron and steel, crystallization of salts, linear changes resulting from variation in moisture content. 

Sulphate attack on mortars

Sulphate attack leads to expansion of mortar, thereby causing cracking of brickwork, spalling of brick edges, deterioration of mortar, wide horizontal and vertical cracks in the plaster and falling of the plastered surface. 

The cause of this attack is the chemical action between the sulphate salts in bricks and constituents of Portland cement. 

Sulphate Attack on Bricks

This action is rapid in the presence of water and hence wherever moisture penetrates, excessive dampness occurs. This type of defect may be prevented by preventing moisture penetration. It will avoid the defect to a large extent. Bricks of low sulphate content and the sulphate resisting cement should be used. 

Unsound Materials

Unsound materials cause the formation of small pits at the mortar joints. General expansion and cracking of brick work is visible. Unsoundness in lime is caused by the presence of un-slaked particles of lime. Similarly un-slaked lime particles may be present in the bricks also. 

Unsound Material

Frost action

Defects due to frost action would cause cracking in brickwork. Prevention of water accumulation would prevent this defect.

Corrosion of Metals

Brickwork may get opened or cracked or stained due to corrosion of metals lying adjacent to it. Unprotected iron and steel are liable to get corroded when acted upon by moisture and they increase in bulk, thereby causing cracks in masonry. 

Corrosion of Bricks due to Metals

Protecting the metal surface with cement mortar up to a layer of 1 to 2 cm thick is essential to prevent corrosion.  Partially embedded steel or iron members should be surrounded with bituminous compound for portions not embedded in mortar. 

Metal Corrosion 

Crystallization of Salt and Efflorescence 

This is a prominent defect in brick masonry. In moist climate, in damp places, like basements or under leaky gutter, masonry often gets disfigured by the formation of a white deposit called efflorescence. Deposit originates from the mortar and frequently spreads over a part or entire face of the wall. 

Efflorescence 

Absorbed water dissolves the salts of sodium, potassium and evaporating, forms a crystalline deposit on the surface. In addition to unsightly appearance, the crystallization of salts in the pores of the bricks or mortar may cause disruptive expansion resulting in disintegration due to cracking. 

To avoid Efflorescence do not use porous bricks in contact with limestone. Protect brickwork against contamination of salt-bearing materials during building operations. Bricks should be thoroughly soaked during construction. Correct design of DPC should be used. 

Shrinkage Effects

Brick work may crack due to the shrinkage movements arising from changes in moisture content. This defect is more common with concrete and lime mortars. 

Shrinkage Effects

Good quality bricks should be used in dry condition. All of work should be protected from rain. 

India to build world's highest railway bridge Chenab Bridge in Jammu Kashmir

You might have travelled above 1000 feet in aero-plane but you must not have travelled at that much height with a Railcar, But Indian engineers are ready to lift such a bulky weighty weighing car of iron to a height 35 meters more than that of Eiffel Tower.

"The Project worth more than 90 million is being handled by the Railway Corporation. It includes more than 25 thousands tones of steel."

Background of the Project

Currently Guizhou Province of China is enjoying the world’s tallest railway bridge which stands over Beipanjiang River but despondently this record is about to break in 2016 as its height of 275 meters is by no means near to 359 meters which is the expected height of arch-shaped steel railway bridge.

Steel cranes in Operation (AFP Photo/Prakash Singh)

The northern areas of Jammu and Kashmir State hosts spectacular mountainous region and at such a height the railcar can’t cross the Chenab River, but thanks to Civil Engineering of newest era that gave the principles to rule the world.

Excavator being Operated (AFP Photo/Prakash Singh)

According to a local News agency this bridge is expected to be ready by December 2016. The steel structure has obviously a poor vibrating dampness  characteristics, for this reason safety and precautions have been made to avoid any devastating earthquake and wind speeds.

Project currently in development stages

The Project worth more than 90 million is being handled by the Railway Corporation. It includes more than 25 thousands tones of steel. Due to the difficult typography of the area few of the tones has to be transported by Helicopters.

Project Purpose

The Project named as Chenab Bridge spanning Chenab River between Bakki and Kauri, in Reasi Distric of Jammu and Kashmir. Due to questions on its safety and stability the project had been stopped in 2008 after which it is restarted in 2010 due to assurance and deep model study of the project.

Huge cranes (AFP Photo/Prakash Singh)

This highest railway bridge in World would make you scarier than riding the roller coaster that will bring everything eaten. :D

So just wait and see

Video of the Project

Here is a AFP Official Video of the World's Tallest Railway Bridge

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What is Formwork, Shuttering, Scaffolding, Shouring

During construction of reinforced concrete works as well as their maintenance, we need to support the structure as long as it is in its premature state or plastic state as it could not even bear its own load. After the suitable duration of time, i.e. when concrete sets enough to take its own load, these temporary supports are removed systematically.

Here are some of the definitions that must be known to a construction engineer as well as civil engineer.

What is Formwork:

Concrete construction in the modern building works has achieved considerable importance, roughly speaking 80% of civil engineering works utilize concrete for their constructions. Concrete being plastic material in fresh state, has to kept within an enclosure (moulds) till it gain reasonable strength, this temporary structure which has to be built for any concrete member is called “Formwork”.

shuttering, formwork, scaffolding, shoring

Formwork is thus a sort of mould used for pouring fresh or plastic concrete. It is closed from all sides and can carry the hydrostatic load of fluid concrete, additional load due to vibration, and load of men and machinery. Formwork should be such that it can be easily removed after hardening of concrete.

Timber, plywood panels or steel sheets are used for formwork. Timber is the most common material for formwork construction, it is easy to work with and it is also economical. However the use of steel forms thus gained lot of popularity in the recent years. They can be obtained for all types of structures. The initial cost of steel forms may be high but they can be repeatedly used for a number of times.

What is Shuttering?

Shuttering is a temporary plateform constructed with the help of wooden planks, wooden logs, steel rods or bamboos over which formwork is supported and ultimately pouring of concrete is done.

What is Scaffolding?

Scaffolding is a grid of bamboo, wooden planks or circular steel pipes by which labour can have access to any point of the structure to be constructed and further formwork and shuttering can rest over it. Steel scaffolding is most commonly used as it is easy to dismantle and reassemble.

What is Shoring?

Shoring is the temporary support given to the existing structure for repair purposes. When dismantling any central building, the surrounding building is also temporarily supported.

What is Timber, Merits, Demerits Growth and Structure

Variety of Construction Materials are being used now a days depending upon the availability and transportation cost, lesser the material available expensive will be the structure and as a result structural engineer might have to think to change the material accordingly. In mountains where brick is not easily available due to less availability of plain surface timber is preferred, similarly in areas where there is great danger of earthquake and light structure is needed Timber is preferred.  

In this post I will be sharing with you some key terms related to Timber engineering, merits demerits, of timber, growth of trees and structure of trees. It is a series of post related to timber construction so stay tuned for more updates. 

Timber Construction

"In developed nations like the United States, timber is used as lumber in the construction industry and to produce furniture, pulp and paper, and wood-based composites."

Definition of Timber:

“Wood which is suitable for building or any other civil engineering purpose is called Timber”

When it is a port of living tree it is called standing Timber.When that tree has been felled it is called Rough Timber. When it is sawn or converted into various forms it is called “Converted Timber”

Uses of timber

Despite of the aesthetic use of timber for decoration and finishing work, Timber is used as a structural material in houses as well as structural components like beams, columns, slabs etc. Because Timber is easily available in hilly and cold areas it is used for partial and full insulation. Some times Timber is used to construct Small Span bridges as well, we can see many of the bold bridges being that of timber along with the cables. Similarly in past Railway engineers used Timber as sleepers under the railway track to bear the thrust of the steel rail gauges and to provide them stability as well. 

Merits and De-merits of Timber

Timber is cheap and economical as it is easily available, in comparison to concrete where which need specified gradation of aggregates and sand as well which is not readily available in some hilly backward areas. Timber can be cut easily to any shape as required in the shape of column, beam or even you can construct truss out a timber log. Timber is durable and long lasting as far as it is dynamite proof. It is harder and light weight which enhances its ability to be constructed on sites of low bearing capacity soils. 

"Early citizens in the Massachusetts Bay Colony started to refer to sawed planks as lumber"

But Timber has some demerits as well, It can easily be attacked by insects which can convert whole of the structure into powder just in few days. Moisture and water logging problems in few areas are destructive for it. It is less strong as compared to steel and concrete. In some plain areas it is very costly and environmental hazards and new environmental laws and regulations do not appreciate its usage. 

Classification of Timber (Trees)

There are two types of trees depending upon their mode of growth;

Endogenous 

Exogenous

Endogenous

They grow inward in longitudinal fibrous mass. Examples are banana, bamboo, palm and cane.Their stem is rough and light yet it is flexible enough to be useful for engineers.

Exogenous 

They grow outward by the addition of one concentric ring every year. These concentric rings are called annual rings. The no of concentric rings indicates no of years or age of that tree. Exogenous trees are mostly used for engineering purpose.

Exogenous trees are further classified into two types;

a) Trees yielding soft wood, 

        a. Conifers or evergreen

        b. Trees with pointed leaves

        c. Deodar, pine, chir, kail belong to this group

b) Trees yielding hard wood,

        a. Deciduous with broad leaves

        b. Teak, sal, shisham belong to this group

Growth and Structure of Timber Trees

The growth is done in summer and autumn season;

In spring, roots suck a solution of salt from the soil, this solution is than transmitted to the branches and leaves. The salt solution losses moisture because of evaporation, then it absorbs carbon dioxide from the atmosphere, then in the presence of sun light this solution is transformed into a viscous solution called a sap.

In autumn this sap is descend below the bark where it gets thick and its transformed into wood forming a cambium layer. Cambium layer is again with the passage of time gets thicker and thicker and is then form an annual ring. The modullary rays carry the sap from inside the bark to the interior of tree getting itself nourished. 

Structure of Timber Construction

The cross-section of the an exogenous trees shows the following structure

i) Pith or Medalla

ii) Annual Rings

iii) Heart wood

iv) Sap wood

v) Cambium layer

vi) Medullary rays

vii) Bark

Pith

The first formed round dark portion of the tree is called pith, around pith annual rings are formed the pith, when the plant is young contains large amount of fluid and it nourishes the plant. It dies up and decays when the plant becomes old. 

ANNUAL RINGS

Woody fibre formed and arranged in concentric rings around the pith are called annual rings, they are called annual because each year one ring is developed, with the help of annual rings we can find the age of tree by counting dark or bright rings, each annual ring consists of two parts outer part being darker and inner one being lighter. The outer portion is dark, solid as compared to inner portion. Wood formed during spring season is called spring wood and the wood formed during summer season is called summer wood. 

Bark or Cortex

It is the outermost protective covering of the tree which is exposed to air. 

Heart Wood or Duramen

The central rings surrounding the pith and is near to the pith is generally darker and is called heartwood. It is non-active part of the tree and generally gives rigidity or strength to the trees.

Sap Wood

Ring near to the bark or away from pith is generally lighter in color and is weaker as well, its main task is to provide sap from root to branches. Heart wood  is generally harder than sap wood thus it must be used for all types of engineering works and sap wood must be avoided as is not rigid is more exposed or liable for decomposing. 

Cambium Layer

Rings between bark and sap wood constitutes cambium layer, it is that part which is not yet converted into wood. If the cambium layer is exposed to atmosphere by removing the bark it will result in ultimate death of the tree.

Medullary Rays

These are thin horizontal veins radiating from the pith towards the bark. The main purpose of modularly rays is to carry sap from inner to bark, and they also keep the inner or outer rings bound together. 

What is Brick Masonary and some important terms civil engineers must know.

When bricks are laid in mortar in a proper systematic manner, they form a homogeneous mass, which can withstand forces without disintegration. This mass of the structure, so made by the use of bricks is called "Brick Masonry" or simply "Brick work".

Bricks are of uniform size and shape, light in weight, durable, fire resistant, have high resale value, low maintenance cost and are easily available in plain areas.

Brick Masonry is commonly used for construction of ordinary as well as important buildings in plain areas now-a-days.

Some Important Terms Used in Brick Masonry

What is Brick Masonry?

(1) BRICK

An artificial structural element in the form of a rectangular block of clay is called a “Brick ".

Bricks can be manufactured of any required shape and size. The sizes of some standard bricks are given as follows:

These sizes are called "Nominal, designated or format sizes" and are used while estimating the number of bricks in a given volume of structure.
The actual sizes in which bricks are manufactured, are slightly smaller to allow for the layer of mortar present all around the brick, usually taken as 3/8 in thick. The Actual or Work size of English standard brick, which is mostly used in Pakistan, is usually taken as 8 5/8 in 4 1/8 in x  2 5/8 in.

(2) FROG

The depression provided in the face of a brick is called a "Frog". 

It is provided in the brick to achieve the following purposes:

(a) To form a key of mortar in between any two adjacent courses of brick work, so as to increase the lateral strength of the structure.

(b) To reduce the weight of the bricks, so that the bricks can be laid with convenience.

(c) To provide a place for putting the impression of trade-mark or the year of manufacturing of the bricks.

(3) POSITION OF BRICKS

(a) The position of brick, when laid with its Frog upward in the horizontal plane, is termed as "Brick on bed".
(b) The position of the brick when laid on its side "9 in  x  3 in", with frog in the vertical plane is called "Brick on edge".
(c) The position of brick when laid on its side "4 1/2 in  x  3 in", with frog in the vertical plane is called
"Brick on end".

(4) COURSE

Each horizontal layer of bricks laid in mortar in a brick work is called a "course".

(5) STRETCHER

Brick, laid with its length horizontal and parallel with the face of the wall or other masonry member is called a "Stretcher" 

and a course, in which, all the bricks are laid as Stretchers is called a “Stretching course" or "Stretcher course".

(6) HEADER

A brick laid, so that only its end shows on the face of a wall is called a "Header" and a course, in which all the bricks are laid as headers, is known as "Heading Course" or "Header course".

(7) QUOIN

The external corner of the wall is called a "Quoin".

(8) QUOIN BRICK

The brick, which forms the external corner of a wall is known as "Quoin brick".

(9) QUOIN HEADER

A corner header, in the face of wall, which is a stretcher in the side wall is known as "Quoin header".

(10) QUOIN STRETCHER

A corner stretcher in the face of a wall, which is header in the side wall is known as "Quoin stretcher".

(11) BRICK BATS

The pieces of bricks, cut long their length and having width equivalent to that of a full or half brick are called "Brick bats".

Some common Brick Bats are shown below:

(12) QUEEN CLOSER

Queen closer is a brick, which is half as wide as full brick and is made by cutting a whole brick lengthwise into two portions.
These are generally used next to the Quoin header for creating bonds in brickwork.

(13) KING CLOSER

A brick, whose one diagonal piece is cut off one corner by a vertical plane passing through the center of one end to the center of one side.

It is actually 7/8 of a full brick but is usually called a 3/4 brick

(14) BEVELED CLOSER

A brick cut longitudinally along a vertical plane, starting at the middle of one end to the far corner.
One quarter of the brick is cut off in this way.
           

(15) BULL NOSE BRICK

 
A  brick with rounded corners is called a “Bull Nose Brick”
                               

(16) SQUINT BRICKS

These bricks are used to construct acute (>90 degree) or obtuse (< 90 degree) corners in brick masonry.
These are special forms of bricks.

(17) JAMB

The vertical sides of door or window openings provided in a wall are known as "Jambs".

(18) REVEALS

The part of the Jamb opening , which is exposed between a door or window frame and the face or back of a wall is known as "Reveal".

(19) SILL

The horizontal part (either of timber, concrete, stone, metal, etc) at the bottom of a door or window, supporting the vertical members of the frame is known as " Sill " and its height window base from the floor level is known as " Sill level ".

(20) MORTAR

The paste obtained by mixing a binding material and a fine aggregate in suitable proportions in addition to water is known as "Mortar".

Cement and Lime are used as binding materials and Sand, Surkhi, Cinder, etc. are used as fine aggregates. The mortars are named according to the type of binding material used in their preparation such as, cement mortar, lime mortar, etc. The mortar prepared from simple earth is known as "Mud Mortar". The mortar not only acts as a cementing bed between any two courses of bricks but also, gives strength to the structure by holding the individual bricks together to act as a homogeneous mass.

Credits

These notes have been developed by Prof. Dr. Liaqat Ali Qureshi (UET, Taxila Pakistan)