Footings Foundations

8/12/2019 Footings Foundations

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BUILDING TECHNOLOGY II

FOOTINGS AND FOUNDATIONS


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FOOTINGS

Footings are the first part of a house that is built,

and they stop your house shifting from its

intended position.

Every new house and extension will need new

footings, the footings will need to be specified by

an engineer ( or possibly architect if they are very

straight forward). There are a number of factors which will

determine the type of foundations you will need.


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SITE CONSTRAINTS

Each site is unique, the slope, soil type and

rock position will all affect the design of your

footings. If there is any slope to your site you

may need to do some cut and fill excavation or

you may have a site with uneven rock under

the soil. Footings need to have even bearing

on solid ground, this means that the concreteneeds to sit on rock or very hard compacted

earth.


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EXCAVATION

The excavation of footings will be done with a

bobcat or excavator. If you need to drill piers

then the excavator that you hire will need to

have a orger bit attachment. You may need to

consider how the excavator will access your

site and where the excavated earth will go, are

there some garden beds planned for near thehouse.


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HOW TO DECIDE WHICH FOOTING

SYSTEM TO USE:1. The type of house you are building:

If you are building a house which includes many of thefollowing, then your house will be heavy. This means that yourfooting system will need to be substantial to handle the higher

loads, and will typically come at an increased cost.

Concrete slabs

Double brick walls (known as "full-brick")

Multi-storey (particularly if concrete slabs are used forfloors at all levels)

Tile roofing

Large load-bearing concrete columns and walls ("framing").


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If you are building a house which includes many of thefollowing, then your house will be lighter and you will beable to use a foundation system which typically would notcost as much.

Steel frame (advantage is they are truly straight, andunaffected by vermin)

Timber frame

Virtually any floor system which is not concrete Cladded walls (metal or timber)

Metal roofing


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2. The type of ground you are building on


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DETAILS OF WOODEN FOOTING


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FOUNDATION

Foundations for wood-frame structures are built

to take advantage of the structures ability to

spread the load out over a wider area rather than

concentrating it on columns. Because of this, it isimportant for the footings to be placed deep

enough in the ground to avoid freeze/thaw cycles

There are two primary options for foundationsfor wood-frame structures: concrete and pressure

treated wood.


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PRESSURE TREATED WOOD

FOUNDATION


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By eliminating the concrete floor slab, wooden

foundations are best used in areas with heavy

precipitation, which can cause problems with

the concrete. It is important that the wood bepressure treated to ensure that the structural

stability of the wood is not compromised due

to insects and moisture.


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CONCRETE SLAB FOUNDATION


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DETAILS OF WOODEN FOUNDATION

A. Anchor boltsB. Ledger board

C. Joists (typical)

D. Band board

E. Vertical post

F. Concrete footing (shown with form)


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LESSON 1:FOUNDATION

UNIT1: FOUNDATION

Brief History

Therefore, whosoever heareth these saying of mine,

doeth them, I will liken him onto a wise man, whichbuilt his house upon a rock, And the rain descends,

and the floods came, and the winds blew, and beat

upon the house, and it fell not for it was founded

upon a rock.


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Matthew 7:24-25

The advanced knowledge brought about by the science of Geology andSoil mechanics have confirmed the rock foundation bed to be the most

stable medium where to lay the footing of the structure . The early buildings of the babylonian Empire constructed Raft or Mat

foundation from out of the sundried and burned bricks on top of flatmoulded earth which was filled up from 1.50m. to 4.50meters high Themany foundation was constructed to a thickness of 1.00. to 1.50meters ofbrick platform bound together by a natural asphaltic material forming a

solid foundation where the city walls, temples and public buildings, wereconstructed.

The Greeks extensively used marble blocks as foundation oftenly tiedtogether with metal band likewise, the Chinese buildings also used largestones carefully cut and accurately fitted to each other without the use ofmortar as evidently seen in the construction of the Great Wall of China.


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The Roman builders introduced various foundation types tosuit the soil condition Woodpiles were used on very soft

ground and ground and wooden mats were laid undergroundwhere masonry structure were built upon them. The Romanbuilders further developed, this early use of concrete, wasforgotten consisting of flat stone bonded with cement which,unfortunately, this erly use of concrete, was forgotten duringthe middle ages.

The introduction the grillage footing resolved the problem offoundation weight in the year 1880 when it was firstintroduced. The improved grillage footing made of steel railembedded in concrete was introduced in Chicago by JohnRoot in the year 1891. The advent of reinforced concrete in

the early part of 1890. superceded all these kind of footingdue to the advantage it offered in all aspect of buildingconstruction.


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UNIT2: SOIL AS A FOUNDATION

The earth underlying the building of man provides theultimate support of the structure against all elements ofnature. Thus, the soil where the building stand automaticallybecomes a material of construction Physically, soil is amaterial to carry load satisfactorily, a greater area of volume

of soil is necessarily required. Loads that are carried by thesteel, concrete, and wood has to be transmitted to the groundbut in needs a transfer device called foundation.

Foundation has its purpose, to transmit the collective buildingload to the in such a way that the supporting soil will not be

overstressed (load) and will not undergo deformation thatmay cause serious building settlement.


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A structural foundation performs properly only if thesupporting soil behaves properly. Building support is providedby a soil foundation system, which is an in separable

combination. Considering that soil foundation systemresponsible for proving support for the lifetime of thebuilding, all forces that may not over that time period must beconsidered. For the building to last, its foundation must bedesigned for the worst conditions that may develop.


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Typically, foundation design always include the

following1. the effect of the natures dead load plus

the live load

2. Load effects caused by wind, heat, water,earthquake

3. Explosive blasts


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Foundation are grouped into two boad

categories:

1. Spread footing

2. Mat or Raft foundations


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Shallow foundations includes:

a. Spread footing

b. Mat or Raft foundations


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Deep foundations also includes:

a. Piles

b. Pilesc. Caissons


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The Floating Foundations is a special category

of foundation and is not a different type but it

represents a special application of soil

mechanics principles to combination mat-caisson foundation


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The General types of foundations are:

1. Spread Footing

2. Mat or Raft Foundation3. Piles and Pier Foundation

4. Floating Foundation


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Spread footing

Spread Footing is typically of plan concrete or reinforced

concrete. Basically, it is used to spread put building column

and wall loads over a sufficiently large soil area.

Spread footing are constructed as close to the ground surface

as the building design permits and as controlled by local

conditions and building regulations. To be classified as spread

footing, the foundation does not have to be on shallow depth.

However, spread footing will be located deep enough into

ground if soil conditions or building design requires.


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The spread footing foundations for building columns and wall

have a common shape of:

1. Square

2. Rectangular

3. Trapezoidal

4. Long Strips


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Mat or Raft Foundations

The mat or raft foundation is considered a largefooting extending over a wide area. Frequently, theentire area is occupied by mat or raft foundation.

The mat foundation is adopted in a condition where

individual column footings (if used) would tend to becloser with each other or tend to overlap. The typeof foundation is utilized as a means to reducedifferential settlement between adjacent areas. Themat structure should be rigid and thicker than spread

footing to function effectively.


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Pile and Pier Foundations

Pile and pier foundation is intended to transmit structuralload through the upper zone of poor soil to a depth where theearth is capable of providing the desired support. The type offoundation is utilized where it is necessary to provideresistance to uplift or where is a possible loss of ground orerosion due to flowing water. Piles are slender foundationunits driven into place. Pier units are formed in place byexcavating an opening to the desired depth where concrete ispoured. Naturally, such foundations are large enough to allow

an individual to enter and inspect the exposed earth layer.


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A clear distinction between pile and pier type type foundationis not definite because of the changes and innovations inconstruction or installation methods. The developing practiceclassify all deep slender foundation units simply as pile typefoundation with terms such as driven, bored, or drilled alldeep slender foundation units simply as pile type foundationwith terms such as driven, bored or drilled and precast or castin place to indicate the method of installation and

construction . A caisson is a structural box or chamber that is sunk in place

or built in place by excavating systematically below thebottom of the unit which descends to the final depth.


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Open caisson maybe: box type or pile type. The top and

bottom are opening during installation. When in place, the

bottom maybe sealed with concrete if needed to keep out ofwater. Sometimes the bottoms are socketed into rock to

obtain a high bearing capacity.

Pneumatic caissons have the top and side sealed and use

compressed air to prevent water and soil from entering thelower chamber where excavations to advance the caissons

occur.


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Floating Foundation

The floating foundation is a special type of foundation appliedin location where deep deposits of compressible cohesivesoils exist and the use of piles is impractical. The floatingfoundation concept requires that a building substructure(below the ground structure) be assembled as a combinationmat and caisson to create a rigid box. This foundation isinstalled to a selected depth that the total weight of the soilexcavated for the rigid box is equal to the total weight of theplanned building. In theory, the soil below the structure occur

when the bottom of the excavation expands after excavationand recompresses during and after the construction


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Piles

By definition, piles is a structural member of

small cross-sectional area with reasonable

length driven down the ground by means of

hammer or vibratory generators.


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Piles are classified according to:

a. Type and size

b. Shape as to the cross-sectionc. Material


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As to the kind of material

a. Timber pile

b. Concrete pile

c. Metal pile


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The important functions and uses of Piles:

The decision to use pile foundation is the result of scientific

method of exploration and tests of the underlying soilconducted by designing engineers which were brought about

by any one of the following purpose:


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a. As friction pile at their bottom portion transmitting the load

through soft strata into stiffer lower strata.

b. As friction pile utilizing its full length.

c. As soil compactor

d. As end bearing column

e. As stabilizer of banks

f. As batter pile

g. As a dolphin

h. As sheeting


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Unless batter piles are intended to be effective in serving any

one of these functions, they should not be utilized, otherwise,

driving piles without any purpose will be expensive exercise in

futility.


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UNIT 3: POST AND COLUMUS

Wooden post

The traditional methods of construction utilizing wood as post

have been outmoded by reinforced concrete column and the

use of load bearing masonry blocks. The use of lumber in

most construction is now limited to floor and roof framing,

studs and joists, ceiling and paneling. Lumber material is fast

becoming are and costly despite of its being inferior in quality.

Lumber, which is most abundant and a cheap construction

material something ago has turned out to become hot itemtoday.


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For brief historical background, the construction of

building with wooden post is briefly discussed as

follows:

1. wooden post to rest on a concrete footing is dressed with

its bottom end squared and trimmed perpendicular at its side.

2. A charcoal or chalk mark is established along the face

length of the post connecting both ends. This marking willserve as the reference line for checking its vertical position

with the aid of plumb bob.


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3. From the bottom of the post, measure and indicate theheight of the girder and girts, make the necessary dap beforeits erection to assure that the girder and girts are in the

horizontal level. However, it is assumed that the concretefooting is horizontally leveled with the floor line.

4. The post could be erected manually using 2*3 lumberbraces and man power or by the use of rope and pulleymounted on a jump-pole.

5. Check the vertical position of the post on two sides with theaid of plumb bob, then have it permanent position. The size ofthe drill must be the same as that of the machine bolts.

6. With boring tools, drill a hole across the opposite strap andhave it bolted to its permanent position. The size of the drillmust be the same as that of the machine bolts.


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In most cases, not all wooden post selected for post

structures are straight. Some are bowed slightly curved but

thry could be corrected in the process of construction.

Bent posts are erected in a counter-bend position with other

post facing toward the outside of the building perimeter. After

mounting the girder and floor joist-straightening operation

could follow.

However, no attempt should be done through the use of a barclamp or a rope as shown in Figure 4-2. The common failure

of this process is the crushing of footing pedestal caused by

twisting of the wrought iron post strap. However, it could be

prevented with a proper diagonal and horizontal bracing atthe lower potion of the wooden post along the post strap.


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Column

Reinforced Concrete

The term column is loosely used in a general sense for anysupport such as a post or pier. The chief purpose of a columnis to support a floor and roof beam or arch. Most columns arefree standing; some however, are integrated, that is , part of

the circumference is embedded in a wall.


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Reinforced concrete columns are classified

into two:

1. Short column-when the unsupported height is not greaterthan times shortest lateral dimension of the cross section.

2. Long column-when the unsupported height is more than

ten times the shortest dimensions of the cross section.


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Columns are classified according to the types

of reinforcement used:

1. Tied column

2. Spiral column

3. Composite column

4. Combined column

5. Lally column


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The cross section of a column is either

1. Square2. Rectangular

3. Circular

4. Elliptical

5. Octagonal or any other geometrical forms depending upon

the needs and tastes of the designer.


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Tied Column

Tied column has reinforcement consisting of vertical or

longitudinal bars held in position by lateral reinforcementcalled lateral ties. The vertical reinforcement shall consist of at

least 4 bars with a minimum diameter of 16mm or number 5

steel bars.


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Lateral Ties-the ACI code on lateral ties

provides:

All non-prestressed bars for tied column shall be enclosed by

lateral ties of at least NO. 3 bar size for longitudinal bars NO.

10 or smaller and at least NO. 4 size for NO. 11, 14 and 18 and

bundled longitudinal bars. The spacing of the ties shall not

exceed 16 longitudinal bar diameter or the least dimension of

the column.


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The Code is specific as to the size of the lateral ties

required with respect to the size of the longitudinal

bars, which is the main reinforcement of the column,thus:

1. A No. 3 or 10mm lateral tie is required if the main

reinforcement of the column size is No. 10(32mm) or smaller.

2. No. 4(12mm) lateral ties shall be used if the main

reinforcement size of the column is either Nos. 11, 14 or

18(36mm, 45mm or 57mm) steel bars.


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The spacing of the lateral ties of a tied column is governed by

conditions:

1. That the distance should not be more than 16 times thediameter of the main reinforcing bar.

2. That the spacing should not be more than 48 times the

diameter of the lateral ties.

3. Spacing should not be more than the shortest dimension ofthe cross section of the column.


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To find the spacing of a lateral tie required for

a tie column the following illustration is

presented:

Determine the spacing of the lateral ties for

a tied column as shown in figure 8-3.


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Solution:

1. The diameter of the longitudinal bar is 20mm.

2. Multiply 16*20mm=320mm or 32cm

3. Multiply 48*10mm=480mm or 48cm.

4. The shortest dimension of the column is 35cm.

F th lt f th b t ti it ld b


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From the result of the above computation, it could be seenthat the least value found is 32cm. Therefore, the spacing ofthe lateral ties will be 32cm. On center.

When there are more than 4 vertical bars in a tied column,

additional ties shall be provided to hold the longitudinal barsfirmly to its designed position. The Code further states:

The tie shall be so arranged that every corner and thealternate longitudinal bar shall have lateral support providedby the corner of the tie having an inclined angle of not more

than 135 degrees and no bar shall be farther apart than 15cm.Clear on either side from such a laterally supported bar.


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Reinforcement Ratio and Limitation

The size and number of steel bars to be places in a tiedcolumn is governed by the proportion of its cross sectionalarea to the gross area of the column. The Code so providesthat:

The cross sectional area of the vertical reinforcement shallnot be less than 0.01 nor more than 0.08 times the gross areaof the column section.

Find the minimum and maximum steel bars that could beplaced in a tied column having a cross sectional dimension of

25*30cm. In figure 8-5.


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Solution:

A. Determine the Minimum Reinforcement Area:

1. The cross sectional area of the column is:25*30=750sq.cm

2. Find the minimum area of the vertical reinforcement area

0.01*750=7.5sq.cm

3. Convert this area to the size and number of steel barswith the aid of Table 10-1 and 10-4 Area of 4pcs. No. 5

(16mm) bar=8.04sq.cm


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B. Determine the Maximum Reinforcement Area

1. 0.08*750=60sq.cm Maximum area of steel bars.

2. Referring to Table 10-2

10pcs. Of No. 9(28mm) bars=61.6sq.cm

8pcs. Of No. 10(32mm) bars=64.3sq.cm


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From the result of the illustration (Figure 8-5), the minimum

steel bars that could be placed in a 25*30cm, column are 4pcs.

16mm. And the maximum are either 10pcs. 28mm. Or 8pcs.32mm.

dl d i l


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Bundled Bars in a Column

Difficulties have been experienced in placing concrete mixture

inside forms congested with steel bars. A column that is

heavily loaded with reinforcement has this serious problem

when large number of steel bars are positioned and held

individually by lateral ties. Bundled bars consisting of 2 to 4

bars tied in direct contact with each other is somethings

employed to using bundled bars is to accommodate therequired steel bars for the column and at the same time

provide enough space for the concrete thereby observing the

rules and specifications as to the spacing of bar limitation and

the required concrete protective covering.


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Failure of Tied Column

The failure of a tied column is by crushing and shearing

outward along an inclined plane where vertical bars fail by

bucking outward between lateral ties. The failure of a tied

column is said to be abrupt and complete and is considered to

be more disastrous than the failure of a single beam girder in

the same floor.


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Methods of Constructing Tied Column

There are three methods presented in constructing a tiedcolumn for a small and medium reinforced concrete structure:

1. Block laying after the concreting of tied column.

2. Concreting of the tied column after block laying.

3. Simultaneous concreting of columns and wall.


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Stock laying after the concreting of tied column.

This type of construction is actually erecting an isolated or

independent column providing steel dowels in anticipation ofthe installation of walls and partitions. There are two methods

adopted in setting tied column reinforcement of the column

on the footing by means of steel dowel embedded during the

concreting of the footing slab. The other is directly attaching

the main reinforcement itself to the footing slab

reinforcement, followed by concreting of the footing slab

ahead or monolithically with the column.

The constr ction proced res nder this method of block la ing after the


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The construction procedures under this method of block laying after theconcreting of the concreting of the tied column are as follows:

1. Install the scaffolding that will support the column reinforcement andits form. Usually, there are 4 pieces of lumber installed vertically around

the 4 corners of the column provided with horizontal members anddiagonal braces. The horizontal member of the scaffolding is verticallyspaced at about 1.00 meter between each layer.

2. Transfer the marking and reference point of the building from the batterboard to the upper and lower member of the scaffolding. By the use ofplumb bob, check the vertical projections of this marking.

3. Install the assembled tied column reinforcement directly to the footingslab reinforcement if concreting of the column and foundation aresimultaneous, or to the footing dowels if concreting of the foundation slabis ahead of the column.

4. Provide a temporary wood brace on top and lower members of thescaffolding across the column reinforcement. Insert these braces acrossthe tied column reinforcement to hold the bars to its vertical position. The

idea of inserting this brace across the tied reinforcement is to give way tothe mounting or installation of the column forms.

5. Verify the vertical position of the reinforcement in the row


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5. Verify the vertical position of the reinforcement in the rowof several columns in series both in either direction.

6. Install first the narrower side forms in opposite direction onits vertical position.

7. Do not cover the form until after the following accessorieshave been verified from the plan and installed, if there is:

a. Downspout

b. Electrical conduits and utility boxes

c. Stand pipe or fire hydrant d.Plumbing soil and water supply line e.Telephone line f.Burglar alarm line g.Intercom door bell line

h. Steel dowels for walls and partitions, etc.

8. Have the work inspected by authorized inspectors or


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8. Have the work inspected by authorized inspectors orsupervisions. This is done as a matter of procedures to giveaccess to the inspector to see everything inside the formbefore it is closed.

9. Before covering the form, see to it that the wide cover isprovided with charcoal line mark and nail as a guide to assurethe column size and in fixing the form to its vertical position.All dirt and debris inside the form shall be removed before

covering. 10. Do not leave the forms if it is not firmly set and completely

supported. Most of the bulging failures of forms are due tonegligence and the inherited manana habit attitude.

11. Verify if the form is provided with window opening for

pouring of concrete at lower elevation pouring of concrete athigh elevation is one cause of segregation of particles

Concreting of column after block laying of walls


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Concreting of column after block laying of walls

Under this type of construction, which is very common, the

wall footing and the column footing are worked and

concreted ahead. The column and the wall reinforcement areset into its final position followed by installing masonry blocks

then concreting of the column.


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The methods of construction are as follows:

1. After the excavation of the soil, guide post for block laying

is prepared and installed about the corner of the wall line.This guide post is usually lumber of the size from2*2 or 2*3

erected vertically in plumb line to serve as guide of the mason

for his block laying work.

2. Concretion of the wall footing is followed immediately byconcrete block laying. The idea is to have a strong bond

between the footing and the masonry block aside from the

saving in the use of mortar.

3 The tied column footing is concreted much ahead than the


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3. The tied column footing is concreted much ahead than thewall footing with the column reinforcement embedded on it.Masonry block laying stops where it meets the columnreinforcement.

4.after the block laying, the forms for the column are installedand properly braced, but see to it that accessories such asdownspouts, electrical conduits, etc. are also installed if calledfor the plans.

5.prior to the pouring of concrete mix to the column, theinside space of the forms are cleared with dirt, sawdust,debris and washed thoroughly then grouted before pouring ofconcrete.

The popularity of this method of construction is


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The popularity of this method of construction is

attributed to the following advantages:

1. This method of construction requires less material

for forms scaffolding and bracing.

2. Once the column form is mounted, G.I. tie wire

could be sufficient to hold the form in rigid position

3. The bond between the wall and the column isstronger than when they are connected by mortar as

in the other method of construction.

4. Cracks between the wall and the column are

unlikely or seldom appear on the surface.

h h l b d bl k l l d


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5. The horizontal bars used in block laying are laidcontinuously across the column reinforcement. This processminimize the horizontal overlapping of splices and

consequently eliminate the use of horizontal dowelssupposed to be inserted across the column in preparation forthe wall construction if column concreting is ahead of theblock laying.

6. The column will not be affected much by shocks or

vibrations caused by the removal of forms because thecolumn is laterally supported by the hollow block walls andonly two forms are to be removed.

7. The work is fast, easy, and economical with less destruction

of forms, lumber braces and supports, waste of nails andlabor aside from the handy handing in transferring andreinstalling of the forms.


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The methods of construction under the third category of

simultaneous pouring for column and walls in one setting of

mixing could only be made possible if the concrete mixture

for both the wall and columns are of the same proportions.

Otherwise, if the concrete proportion of column differs from

that of the wall, one structure must be poured ahead using

each specified mixture proportions. In such a case, the

column has the priority, which in effect, the methods ofconstruction fall under the first category.


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Spiral Column

Spiral column is the term given where a circular concrete coreis enclosed by spirals with vertical or longitudinal bars. The

vertical reinforcement is provided with evenly spaced

continuous spiral held firmly in position by at least three

vertical bar spacers. The column reinforcement is also protected by a concrete

covering cast monolithically with the core. Comparatively, this

type of column is stronger than the tied column and is

preferred for a slender (long) column in carrying heavy load.

Wh l d i i d li d i l l l t l


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When a load is imposed on a cylindrical column, a lateralpressure is exerted at the confining materials, whicheventually causes hoop tension in the spiral. A closely spaced

spiral, confining the concrete and vertical bar, counteracts thelateral expansion, while the concrete in the core increases itscarrying capacity. The sign of failure of spiral column isadvanced by the shell (protective covering) spall due toexcessive load, but failure of the column occurs only when the

spirals yield or burst. Unlike the tied column that fails abruptly, the spiral column

with heavy spirals shows a gradual and ductile failure.

Spiral reinforcement limitation and Spacing


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Spiral reinforcement limitation and Spacing

or cast in place of construction, the following should be observed:

1. The spiral column shall have a minimum diameter of 10 mm,

or 1cm.

2. The clear spacing between the spirals shall not be more

than 7.5cm. Or less than 2.5cm.

3. The longitudinal reinforcement area to the gross column

area shall not be less than 0.01 nor more than 0.08.

4. The minimum number of vertical bars shall not be less than

6 pieces of 16mm. Bar diameter.

Section 7-12 2 of the ACI Building Code provides that: Spiral


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Section 7 12 2 of the ACI Building Code provides that: Spiralreinforcement for compression members shall consists ofevenly spaced continuous spiral held firmly in place and trueto the line by vertical spacers. At least two spacers shall be

used for spirals less than 50cm. diameter, three for spirals50cm. to 75cm. In diameter and four spaces for more than75cm. Diameter.

When bigger size of steel bar is used for spiral such as 16mm.Or larger, three spaces shall be used for a spiral having 60cm.

diameterThe spiral shall be protected from distortion due tohanding and placing from the designed dimensions.


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Spiral Anchorage and Spacing

The anchorage of spiral reinforcement shall be provided byone and a half-extra turn of spiral bar or wire at each end of

the spiral unit. When splices are necessary for special bars itshall be tension lap splices with 48 bar diameters as minimumbut in no cases shall be less than 30cm. or welded.

The reinforcing spiral shall extend from the floor level in anystorey or from the top of the footing to the level of the lowest

horizontal reinforcement in the slab, drop panel or beamabove. Where beams or brackets are not present on all sidesof the column, ties shall extend above the terminal of thespiral to the bottom of the slab or drop panel. In a columnwith a capital, the spiral shall extend to a plane at which thediameter or width of the capital is twice that of the column.


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Composite, Combined and Lally Column

Composite column is another type of column where structuralsteel column is embedded into the concrete core of a spiralcolumn. The work involved under this type of column issimilar to that of a spiral column after the structural steelhave been set to its position.

The combined column is a column with a structural steelencased in concrete of at least 7cm. Thick reinforced withwire mess surrounding the column at a distance of 3cm.Inside the outer surface of the concrete covering.

The construction process of a combined column calls for the


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The construction process of a combined column calls for the

installation of the structural steel as the main reinforcement

followed by the attachment of the wire mesh covering. The

wire mesh serves as the holding rids of the encased concrete.Usually the wire mess is attached to the structural steel by

weld. The forms are similar to that of the tied column

construction as previously discussed.

Lally column is a fabricated post made of steel pipe providedwith a plain flat steel bar or plate which hold a girder, bear or

girts. The steel pipe is something filled with a grout or

concrete for additional strength and protection from rust and

corrosion.


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The Relationship Between the Material and the Structure

Building structure has to be distinguished from buildingmaterials. Although, the quality and durability of the materialis a prime consideration, material in its original form as a unithas nothing to do with the strength of participation insupporting load nor resisting forces unless utilized as part of

the structural. The combination of different building materialsthat make it into a building part is called building structure.The utilization of the different materials in the structure hastheir own purpose of service in counteracting the differentforces affecting the structure. This is where design comes in to

determine the sizes, quantity, quality, spacing, proportions,etc.

Although this subject matter is beyond the scope of this book


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Although this subject matter is beyond the scope of this book

to discuss stresses, moments, compression, torsion and the

like is considered as important matter since to discuss those

terms briefly will orient the beginner and future builders ofthe rudimentary knowledge on how these terms influences

the principle on designing structure. Likewise, the reacting

behaviors of the structure when different forces are applied

on it are also relevant in the knowledge of buildingconstruction.

Th diff t ki d f t th t t


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The different kinds of stresses that may act on

structures are:

1. Compressive Stresses2. Tensile (Tension) Stresses

3. Shear and Strain Stresses

4. Torsion Stress and Strain

Stresses on structures are usually brought


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Stresses on structures are usually brought

about by load, which are classified into three

categories:a. Live load

b. Dead load

c. Environmental load

Live Load refers to the occupancy load which is either


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Live Load-refers to the occupancy load, which is eitherpartially or fully in place or may not be present at all.

Dead load-are those loads that are distributed or

concentrated, which are fixed in position throughout thelifetime of the structure such as the weight of the structureitself.

Environment load-consist of wind pressure and suctions,earthquake, rainwater on flat roof, snow and forces caused bytemperature differentials.

Strength-is the cohesive power of the materials that resist anattempt to pull it apart in the direction of its fiber.

Ultimate Strength-is the maximum unit of stress developed at

anytime before rupture.

Moment is a kind of alteration or deformation produced by


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Moment-is a kind of alteration or deformation produced by

the stresses.

Strain-is a kind of alteration or deformation produced by the

stresses.

Stress-is an internal action set up between the adjacent

molecule of the body when acted upon by forces, or

combination of forces, which produces strain. Stress refers too

the pressure of load, weight and some other adverse forces orinfluences.

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