Simplified Methods on Building Construction

TABLE 5-4 PHILIPPINE STANDARD

COMPARED WITH ASTM STANDARD
(SECTIONAL AREA)

Philippine Nominal Unit Weight REMARKS

Standard Sectional Kilogram/
. Designation Area mm 2 Meter

6 (mm} 28.27 0.222 10.7% smaller than ASTM No. 2
10 (mm) 78.54 0.616
12 (mm) 113.10 9.887 10.22% larger than ASTM No. 3
16 fmm) 201.10 10.7% smaller than ASTM No.4
20 (mm} 1.577
314.2 1.6% larger than ASTM No. 5
25 (mm} 2.463 10.22% larger than ASTM No.6
28 (mm) 491.9 3.848
32 (mm) 2.9% smaller than ASTM No.8.
36 (mm} 615.75 4.827
4.49<¥o smaller than ASTM No. 9
804.25 ~.305
1017.9 1.6% smaller than ASTM No. 10
7.980
.97% larger than ASTM No.n

TABLE 5-5 STEEL GRADE AND STRENGTH PER mm 2

ASTM Yield Point/Strength Tensile Strength
Philippine
(minimum} (minimum)
STANDARD
Newton/ Kg. Force psi Newton/Kg. Fo·rc:e psi

mm 2 mm 2 mm 2 mm 2

Grade 60 Grade 410 41.808 60.00 620 63.22 90,000
Intermediate Grade 275 28.042 40,000 480 48.95 70,000
Grade 230 24.453 33,350 390 39.77 55,000
Grade 40 .
Structural

Grade

5-3 PRESTRESSED STEEL

Prestressed steel is used in three forms:

1. Wire strand

2. Single wire
3. High strength bar

90

The wire strand are of even wire types where the center wire is

enclosed rigidly by hexagonal outer wires with a pitch of 12 to 16

times the nominal diameter of the strand. The diameter of the
strand ranges from 1!4 to 1fz inch (6mmto 12mm). Prestressing wire

diamet~r ranges from .192 to .276 in. (5 to 7mm) made out from

cold drawn high carbon steel.

High strength alloy steel bars for prestressing ranges from 3/4"
to 1 3/8" {20 to 36 mm) diameter.

5-4 WELDED WIRE FABRIC

Aside from the individual reinforcing bars, welded fabric is
sometimes used for reinforcing concrete slab and other similar

structure such as shells. Siz• and spacing of wire may be similar for

both ways or might be different depending upon the detail of the
design.

5-5 IDENTIFICATION OF STEEL BARS

How to distinguish the different grades and sizes of bars is a
problem that one might accidentally use a lower strength or smaller
size of steel bars from what is being required.

All deformed bars are provided with distinctive markings iden·
tifying the· manufacturer usually by an initial and the bar size

number from 3 to 18 including the type of steel such as:

N - for Billet A- for Axle Rail sign- for rail steel

Additional marking for identifying high strength steel bars:

,...s• ~·• 1. ~~~ c•~ •o
• 1.....0 ... ~~1:)· 1$

Marking System
Figure 5-2

91

TABLE 5-6 STANDARDIZED REINFORCING AND PRESTRESSING STEELS

Product ASTM Minimum Yield Minirnum Tensile
Specification G"de Strength
Stren9th
KSI MPa
KSI MPa

Reinforcing Bar A615 40 40 276 70 483
A616 60 414 90
Bar mats A617 60 50. 345 620
Wire, smoth 50 60 414 80
A706 60 40 90 552
Deformed 40 60 276 620
Welded wire 60 414 70 483
60 60 414 90
fabric, smooth (538 max) 80 620
Deformed *Al84,*A704 (78max) 483
A82 70 517 80 552
Prestress Bar A496 75 517
75 85 552
Prestress wire 85
Prestress 65 586
70
Strand 127.5 586

A185 Type 1 120 448 75 517
A497 Type II 483 80 550
A722 188-200 880 150 1034
827 150 1034
A421 212.5 1296-1330 235-250 1620-1725
229.5
A416 250 1465 250 1725
1580 270 1860
270

* Same as reinforcing Bars

TABLE 5-7 MINIMUM DIAMETERS OF BEND FOK
STANDARD HOOK

Bar Size Minimum Diameter

No.3 -8 6 bar diameter
8 bar diameter
No.9 -11 10 bar diameter

No. 14-- 18

Example : lf2" (l.l/ em} rounu uo• "v "'"' .....cuneter"'"
3 inches or 7.6 em. diameter for hook.

Note: Hooks are not effective in adding compression

resistance of reinforcement.

92

Figure 5-3

Standard Hook

5 - 6 BAR CUT OFF AND BEND POINTS

1. Every bar ~hould be continued to at least a distance to the
effective depth of the beam or 12 bar diameter whichever is larger.

2. The Code requires that at least 1/3 of the positive moment
of steel (bottom bars) must be continued uninterrupted along the
sam~ face of the beam a distance of at least 6 inches ( 15 em) into
the support.

3. At least 1/3 of the negative moment reinforcing bars Should
be extended beyond the extreme position not less than 1/16 the
clear beam whichever ~s the grMter.

~~~------- ,.......-----+f

EndS,.

Figure 5-4

93

5- 7 BAR SPLICING

1. Tension bars may be spliced through:

a. weld ing
b. sleeves
c. tying
d. mechanical devices which provides full positive

connection between the bars.

2. Compression bars may be spliced by:

a. tapping
b. direct end bearing
c. welding
d. mechanical device which will provide full positive

co n n e c t i o n.

. ..
The Code specif ies·. the compressive splice should not be less
than 12 inches (30 em) long."

5-8 BARSPACING

1. The ACI Code specifies that the minimum clear distances

between the adjacent steel bars shall not _be less than the nominal

diameter of the bars or 1 inch 25 mm. for column, this require-

ment was increased to ll/2 bar diameter or ! 1/2 inches or 4 em.

2. Where beam reinforcement are placed in two or more layers,

the clear distances between layers must be. not be less than l -inch

(25 mm.) and the ·bars in the upper layer should be placed directly

above those in the bottom layers. ·

3. In walls and slabs other than concrete joist construction,

the p rincipal reinforcement shall be spaced not farther apart than

three times the wall or slab thickness nor-more than 18 inches or

45cm.

4. The clear distance between pretensioning steel at each end

of the member shall be not less than four times the diameter of

individual w ires nor three time~ the diameter of the strand~

5. The clear spacing between spirals shall not exceed 3 inches
(7.5 em.) odess than 1 inch (25 mm), havi.ng a minimum diameter

94

of 10 mm. Spiral splices shall be48 b4ar diameter minimum but not

less than 12 inches (30 em.) or welded. ·

6. Lateral ties shalf be at least no. 3 bars spaced not to exceed

16 times the longitudinal bar diameter or 48 tie bar diameter orr

the least dimension of the column.
7. Shrinkage and temperature reinforcement shall not be

· placed farther apart than 5 times the slab thickness nor more than

18 inches or 45 em.

5-9 CONCRETE PROTECTION FOR REINFORCEMENT

The following minimum concrete c.over shall be provided for

reinforcing bars, prestessing tendons, or ducts. For bar bundles the

minimum cover shall equal the equivalent of the bundle but should

not be more than 2 inches (5 em.) or the tabulated minimum,

whichever is greater. ·'

TABLE 5-8 PROTECTIVE COVERING FOR STEEL

REINFORCEMENT

Minimum cover in

Cast-in place concrete (non-prestressed) Inches em.*

Cast against and perrreanently exposed to earth 3 8.0

Exp~d to earth or weather: 5.0
4.0
_ No. 6 through No. 18 bars • • • • • • • • • • • • • 2

No. 5 bins 16 mm. wire and smaller ..•..•••.·Hz

Not exposed to weather nor in contact with the l!!z 4.0
ground: 3/4 2.0
Slabs, walls, joists:

No. 14 and No. 18 bars . • • • • • • . . . • .
No. 11 and smaller • • • . • . • • • • • . • • . •

Beams, girders, columns: l!!z 4.0-
· Principal reinforcement, ties stirrups or

spirals •. ·• • . . • . . . . . • • • • . . . . • • • .

Shells and folded plate members: 3/4 2.0
liz 1.5
No. 6 bars and larger • • • • • • • • • • . • • .

No.5 bars 16 mm. wire and smaller • . •

95

Pre-cast Concrete (manufactured under plant} Min imum cover in

control conditions) tn ches em.*

Exposed to earth or weather: 1112 4.0
Wall panels: 3/4 2.0

No. 14 and No. 18 bars . . . . . • . . • . . . . . . • . 2 5.0
No. 11 and smaller . . . . . . . . . . . . . . . • . . . . . 11f2 4.0
lit'•
Other members:
No. 14 and No. 18 bars . . . . . . . . . . . . • . . . .
No. 6 through No. 11 .. : . . . . . . . . . . . . . . .•.
No. 5 bars, 16 mm. wire and smaller . . . . . . .

Not exposed to Weather nor in contanct with the 3.2
ground: 1.0
Slabs, walls, joists:
No. 14 and No. 18 bars . . . . . . . . . . . . . . . . lV• 4.0
1.0
No. 11 and smaller ............•...•... 5/8

Beams, girders, columns:
Principal reinforcements . . . . . . . . . . . . . . . . llfz
Ties, stirrups or spirals .. ..... . .·. . . . . . . • 3/8

Shells and felded place members:

No. 6 bars and larger ................ . 5/8 1.6
1.0
No. 5 bars, 16 mm. wire and smaller . 3/8

*Values rounded to the next whole number.

Pre--stressed concrete members-prestressed and non- Minimum Cover

prestressed reinforcements, ducts and end fittings Inches em.

Cast against and permanently exposed to earth 3 8.0

Exposed to earth or weather: 2.5
Wall panels, slabs and joists . . . . . . • • • . . . . . . . . 1 4.0
Other members ...............•..•........ llf2

Not exposed to weather not in contact with the 2.0
ground;
Slab, walls joists . . . . . . . . . . . . . . . • . . . . . . . . . 3/4

96

Beams, girders, columns: 4.0
Principal reinforcements. . • . • . • . • . • . • . • • • l'h 2.5
Ties, stirrups or spirals • • • • • • • . • • . • . • • • . • 1

Shells and folded plate members: 1.0
Reinforcement 16 mm. and smaller • • • • • • • • 3/8 2.0
Other reinforcements • • • . • • . . . • . . • . . . . . . 3/4

TABLE 5-9 PHILIPPINE STANDARD STEEL BARS
COMPARED WITH ASTM STANDARD: DESIGNATIONS,

AREAS AND UNIT WEIGHT PER METER

Cross Unit weight

Bar No. Nominal Diameter· Sectional Area per meter

Inches mm (mm}2 kilogram kg.

2 1!4 6 28.27 0.222

3 3/8 10 78.54 0.616
4 ll2
5 5/8 12 113.10 0.887

6 3/4 16 201.10 1.577
7 7/8
20 314.2 2.463
81
22 280.13 2.980
9 11/8
10 ll/4 25 490.87 3.848
11 1 3/8
14 1 3/4 28 615.75 4.827
18 21/4
32 804.25 6.305

36 1,017.9 7.980

45 1,590.43 12.469

57 2.551.76 20.005

5-10 BUNDLE OF BARS

For large girders and columns, bundle bars is allowed and these
bundle act as one unit reinforcement with no more than 4 in any
bundle provided that stirrups or ties enclosed the bundle. The
Code specifies that:

1. Not more than two bars shall be bundled in one plane

2. Typical bundle shape are triangular, square or L-shaped
pattern.

3. Bars larger than No. 11 shall not be bundled in beams
or girders. .

4. Individual bars in a bundle cut off within the span of
flexural members shall terminate at different points with at
least·40 bar diameters staggered.

97

5- 11 CONTROL OF CRACKS

1. Cracks are minimized through the use of deformed steel
bars.

2. A larger number of small bars is more effective in mini-
mizing crack width than a smaller number of large bars having the
same total cross-sectional area. ·

5-12 METAL REINFORCEMENT SPECIFICATIONS:

The ACI building code requirements for reinforced concrete
Specifies;

1. Deformed Billet-Steel Bars for Concrete Reinforcement

shall be (ASTM A615). If No. 14 or 18 bars meeting this
· specifications are to be bent, they shall also be capa-

ble of being bent, 90 degrees at a minimum temperature
fo 42° C around a ten-bar diameter pin without cracking
transverse to the axis of the bar.
2. Rail-Steel Deformed Bars = (ASTM A616). If bars are to
be bent, they shall meet the bending requirements of AS.TM
614
3. Axle-Steel Deformed Bars = Shall be ASTM A617
4. Bar and rod mats for concrete re inforcement shall be the
dipped type conforming with the Specifications for ASTM
A184.
5. Plain wire for spiral reinforcement shall be Cold-Drawn
Steel wire for concrete reinforcement ASTM A82.
6. Welded plain wire fabric for concrete reinforcement shall
conform to the specifications of Welded Steel Wire Fabric
ASTM A185. Welding intersections shall be spaced not
farther apart than 30 em in the direction of th~ principal
reinforcement.
8. Welded deformed wire fabric for concrete reinforcement
shall conform to the specification for of ASTM A497.
Welded intersection shall be spaced not farther apart than
40 em in the direction of the principal reinforcement.
9. Wire and tendons in prestressed concrete shall conform
with the specifications for Uncoated Seven-wire ·Stress-

98

Relieved Strand for Prestressed Concrete ASTM A416 or
ASTM A421. Strands other than A416 or A421 may be
used provided that they conform to the minimum require·

f ments of these specifications and have no properties which

make them less satisfactory than those listed under A416

k. or A421. ·

10. Grade B of specifications for welded and seamless steel

pipe ASTM A53.

11 . .Specifications for Structural Steel ASTM A36

12. Specifications for High Strength Low Alloy Structural

Steel ASTM A242
13. For High-Strength Structural Steel ASTM.A440

14. High-Strength Low Alloy Structural Manganese Vanadium
Steel ASTM A441.

15. High-Strength Low Alloy Columbium-Vanadium Steel of
Structural Quality ASTM A572

16. For High Strength Low-Alloy Structural Steel with 50,000
psi or 344,7!?0 kPa minimum yield point to 10 em thick

ASTM A588.

It is interesting to note that the present manufactured steel
bars is either smaller or larger in cross sectional area compared to
the· ASTM standard as shown ~~:m Table 5-4. In the absence of
standard specifications that regulates the manufacture of steel bars
when the Metric System super<:eded the English Measure, manu-
facturers produced steel bars having diameters. at almost in incre-
ment of one millimeter which created problems and confusion.
Lately the Board of Standard has agreed to standardize the manu-
facture of steel bar diameters as follows:

Diameter Millimeter Bar No.
Designation
Inches Equivalent
2
If• . . . . . . . . . . . . . . 1 mm 3
4
3/8 ............... lOmm 5
6
lf2. . . . .. . . . . . . . . . 13 mm 8
9
5/8. ..... ........ 16 mm
10
3f4............... 20 mm 11
14
1· ................ 25 mm
18
1 1/8" . .. ......•... 30 mm

1 lf• . . . . . . . . . . . . . . . 35 mm

1 3/8 .............. 40 mm

1 3f4 • •.•••••••. •. • . 45 mm

211• •.....•. : •.... •. 60 rnm

99

6CHAPTER

FOUNDATION

6- 1 MIEF HII10RY

Builders and laymen throughout the ages have realized the
importance of building structure on • strong foundation. Jesus

Christ on his remarkable sermon before the multitude of people

said: ''Therefore, whoso.v• h,areth these saying of

mine, and doeth them, I will liken him unto a wise man,

which built his house upon a r.ock. And the rain descend,

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

the house: and It fell not: for it was founded upon the

rcx:k."

Mathew 7 : 24- 26

The advanced knowledge brought about by the science ot
Geology and Soil Mechanics have confirmed the rock foundation
bed to be the most stable medium where to lay the footing of a
structure.

The early builders of the Babylonian Empire constructed Raft
or Mat Foundation from out of the sun-dried and burned brid<!s
on top of a flat moulded earth which was filled up and raised from
1.50 m to 4.50 meters high.· The mat founda.tion was constructed
to a thickness of 1.00 to 1.50 meters of brick platform bound
together by a natural asphaltic materials forming a soiid founda·
tion where the city walls, temples and public buildings were con-

structed.

The Greeks t:tas extensively used marble blocks as foundation
oftenly tied together with metal band. Marble being abundant in
Greece becomes the chief construction materials extensively used
in their articulate temples, carvings and statues.

L:.lke~se. the Chinese builders also used large stones carefu(ly

.cut and -ac~tely titted to each other without the use of mortar

as evid~ntly.~ in the construction of the Great Wall of China.

The Romal)i Builders, introduced various foundation type to
~uit the ~~~! ce)nditions. Wood piles were used .on a very soft

100

ground and . wooden mats were laid underground where masonry
structure were built upon them, the Roman builders further devel-
oped the construction of Built-up foundation consisting of flat
stone bonded with Roman cement which. unfortunately, this early
use of concrete has been forgotten during the Middle Ages.

The introduction of the Griltage Footing resolves the problem
of foundation weight in the year 1880 when it was first introduced.
Consequently, the improved grillage footing made of steel· rail
embedded in concrete was introduced in Chicago by John Root in

the year 1891. The advent of Reinforced Concrete in the early
part of 1890 superceded all these kind of footings due to the ad-

vantages it offers in al.l aspect of building construction.

Foundations

Foundation .is that portion of the structural elements that carry
or support the superstructure of the building. Foundation is fur-
ther defined as the substructure wh1ch is usually placed below the
surface of the ground that transmits the load of the building to
the under-lying soil or rock.

Footing

Footing is that portion of the foundation of. a structure which
directly transmits the column load to the underlaying soil or rock.
In short, footing is the lower portion of the foundation structure.

Fomdation Bed -refers to the soil or rock directly beneath

the footing.

.COl.UN

·,.oottllo

Figure 6-1

Foundation Nomenclature

101

Footings are classified into two types, the wall and column
footings. Walt footings is a strip of reinforced concrete wider than
the wall which distributes the load to the soil. Column footing on
the otherhand, is also classified into the following types:

1. Isolated or Independent footing
2. Combined footing
3. Continuous footing
4. Raft or Mat footing
5. Pile footing or foundation
6. Grillage footing

6- 2 WALL FOOTING

In wall footing, the main reinforcements are pla_ced at right
angle perpendicular to the wall uniformly spaced with each other
Longitudinal reinforcement parallel with the wall are laid to assist
in bridging soft portion associated with the almost uncertain varia·
tion of soil conditions. A steel percentage equals to 0.2 to 0.3% of
the cross sectional area of concrete is said to be adequate except
on unusual cases.

-I-'-

~::.:_~-,~ ;r_-rrp~ij I 15 em ;; v~~.~p· ·· .· ~·

I• ~0_ 60 em 1- Property LlneL,.I------1

Figure 6-2

6- 3 ISOLATED OR INDEPENDENT FOOTING

This kind of footing represents the simplest and most eco-
nomical type usually in the form of:

a. Square Block Footing
b. Square Slope Footing
c. Square Stepped Footing

TABLE6-l SAFE LOAD FOR SQUARE IN[)EPENOENTCOLUMN FOOTING

1:... 20,000 l* J'. - 3000 J)lli I tI 3 "... 1-
. -~PI' I
"- 12 .. - 10 I Q.

,·,-.Ew.,..••75 '•· -- 7153.6,.0, ,. Two-way rei'nforcement
" .. 240 poi
uniformly spaced ) ,

r Width ~ '-3" clear

Ban E&ch W,.y ' B~E&c.hW~q B.nEaohW~q

8q. Footi.Da Sq. Footln& Sq. :l'oo._
... r. - r. - ... r. - r. - ~ r.- r. -Col. ~Col.Col.
Lotod,
~· ~la.
~c..L Cal

2600 8000 l(jpe In. 2500 3000 la. 2l500 3000
- - - -Width, D~tb, - - r - -
F~In . . No. Si~e No. Si~e Width, ~tb. ~·Wid&h. No.Si~e No.Sise
l't-In. . No. SUe No.Sise
1'\-In.

Soil~2000psf Soil ~re-4000 . . • Soil ~ure-6000 ptl

.. .20 12 10 8-4 40 12 a-3 10 1-' 64 100 12 4·2 13 13-' 11-4
10 8-4 &-4 12 12-4 11-4 150 11--6
40 12 80 12 4-7 200 16-5
.$.-a4 · 250 12 5-1 16 16-4
eo 12 6-D 12 11-4 7--6 120 12 6-8 15 16-4 t().J; 300 14 6-11 17 111-5 12-6
80 12 6-7 13 11-5 11-6 160 14 6-6 16 6-1 19 17-5 15-6
16 14-5 H-5 16 7-3 21 15-6
100 12 7-6 14 14--6 14-5 200 H 7-4 19 12-6 12-6

120 12 8-2 16 16-5 15--6 240 16 8-Q 20 14-6 14-6 31;0 16 s7--1s0 28 17-6 13-7
140 12 .89--181 17 13-6 13-6 280 16 8-8 21 17-6 17-6 400 18 24 16-7 16-7
160 14 18 .15-6 320 16 9-3 23 15-7 15-7 450 18 8-11 25 17-7 17-7
ltl ·180 lt 10.2 19 17-6 360 16 9-11 24 17-7 17-7 500 20 9-5 26 16-8 14-3
to-e200 It 20 19-6 19-6 400 18 10-5 ~ 20 9-ll 28 16-3 16-8
25 14-8 14-3

220 lt 11-3 21 16-7 16-7 u o 18· 11-0 'P 12-9 12-9 600 22 lo-4 28 17-3 17-8
240 16 11-10 21 17-7 17-7 480 20 11-6 'l1 14-9 14-9 650 2ll 10.9 29 19-8 19-8
22 18-7 18-7 520 liO 11-11 28 15-9 16-9 700 22 11-2
260 16 12-3 31 20-8 20-8
16 12-10 28 15-8 15-3 30 16-9 16-9 750 24 11-7 31 17-8 17-9
16-8 16-8 30 17-9 17~ 800 1Z.O 82 18-11 18-9
le 13... lU
ua2o8o0
..... I 560 20 12-5
600 22 12-10

0w • Reproduced lice doe Amerie11n Coocre~ lul.itu'- aeiaj(IIICIIIl Ccma.U [).,i,.,. HoNl'-11:.

The reinforcement for square footing is usually placed in the

direction parallel to both sides spaced uniformly and perpendicular
with each other.

.J&. • • I.

I

I'

I
I

I

... I

SQUARE 8LOCK SQUARE SLOPED SQUARE STEPPED

Figure 6-3

To use the above table consider the following example:

Problem:
A square column with a general dimension of 12" x 12" is to

support an axial load of 100,000 lb. with the following data:

Bearing capacity of soil= 2,000 psf

f'c for concrete = 2,500 psi
= 1,125 psi
fc for concrete =20;000 psi

fs for steel

Determine the dimensions and reinforcement for a two-way
square footing:

Solution: 1. By illustrative analysis

L0-'0 - 10 ,00~ 1~.

0 1z.. Figure 6-3

li'"

104

2. Referring to the Table 6 -1; under soil pressure fs.= 20,000

psf the value along 100 kips Joad and column size 12"- the width
of the footing will be 7'- 5.. while the depth is 14".

3. The number and size of reinforcement under f'c =2,500 psi
are 14 pes. of No.5 steel bars one-way. .

4. Since the reinforcement is two-way, another 14 pes. No.5
is necessary on the opposite direction.

5. The footing will then be as follows;

*/JIt Pt5. lfAqS-

•OTH WAYS.

j..... """I

Figure 6- 3b

Tt~e effective use of Table 6-1 could be either:
1. To determine the dimension of the concrete footing

and the size of the reinforcement Including its spacing.

2. To determine the load that could be carried by a foot-

ing of a given dimension and reinforcement. .

PROBLEM:
The values given on Table 6-1 and the accompanying illustration

were· all in English measure. Solve for its equivalent in Metric
System using the following convertion factor:

Multiply. by . to get

pounds per square foot (psf) 47.88 pascals
pounds per square fo9t (psf) 4.882
pounds per square inch (psi) .074 kg./sq.m.
pounds per square inch (psi) .703
inch 2.54 kg.fsq. em.
kips
454.5 kg./sq. m•

em.

kilograms

105

6- 4 COMBINED FOOTING

The use of independent footing for extension columns some-
times meet difficulties on property line were footing projection
beyond the exterior wall is not allowed. Under this situation, com~

bined footing or strip footing is employed to avoid tncroachment
to an adjoinin~ property and at the same time satisfy the bearing
capacity requirement of the foundation. Combined footing is ·em·
ployed when two or more columns are spaced closely to each
other that their footing will almost or completely merge . The

main reinforcement in a combined footing is laid along the longi·
tudinal direction assuming that the footing acts ~s one way slab.
Transverse reinforcement is also placed at the bottom of the foot-
ing near the column where the critical section for transverse bend- ·

ing is taken at the faG'S of the column pedestal. Consequently,
footing reinforcementS are spaced closely to the center of the
column than the outer portion.

Combined footing is either:

a. Rectangular b. Trapezoidal
. Tlt•"~ZOIUL

11

II 1 - - - - - J
I. •, '
I

Figure 6 7'"· 4
106

6 - 5 CONTINUOUS FOOTING
Continuous footing is sometimes classified as wall footing

which supports sev~ral columns in a row. It is either:
a. Inverted Slab Footing
b. Inverted Tee Footing

Gt~O FOUNDATIOI'I

INVERTED- T

Figure 6 - 5
6 - 6 RAFT OR MAT FOOTING

Unless deep foundation is required by the soil condition, Raft
footing is preferred. This type of footing occupies the entire
area beneath the structure and carry the wall and the column loads.
When a building is too heavy that individual or combined footing
would cover about 'h of the building area, the Raft' footing is
likely to be economical.

The Raft footing is either made of an inverted slab provided
with a .capital or pedestal at the bottom of the column or an·
inverted slab with partitions as the stem ofT-Beam connected to
the raft where the column rests at their intersections. Other types
· are shown in Figure 6-6.

107

CANTILEVER FOOTING

:: ::: II TMICitEMED SLAB

A UNif'ORllll SLAS

C BEA!Iol &. GIA0£.11 ,.LOOII.D . T·UAM WITH IMDEP!:MDUT

RAFT OR MAT FOUNDAlION

Figure 6·6

108

6- 7 PILE FOUNDATION

When a foundation bid fs too weak to support o Raft footing,
there is on urgent need to provide o suitable material where to

transfer the excess load to a greater depth wherein piles or pier
is the answer.

6-8 PILES

The use' of piles have been employed by the early builders to
support private and public buildings which was found iri the cons-
truction of the Romans. The brJdge across the Rhine ·River is
afso supported by piles constructed during the rule of Julius
C:oesor. Piles were Jikewise found near the lake of Lucerne and
New Guinea, construction which where built about A.D. 200. The

Campanile of Venice after its destruction have been found oUt to

be resting on wood pHes which according to history has been
driven os .arly as A.D. 900 and yet after the destruction ·of
the Compardle, ~ piles were found out to be In oblo1ute per-

fect condition tNt 4t was even reused for pH• foundation.

Pile - is a structural member of small cross-sectional area with
·reasonable length driven down the ground by means of hammer or
vibratory generator.

Pier- refers to a large cross-sectional dimension, each capable

of transmitting the entire load from a single column down to a

stable stratum. ·

Piles are classified according to:

1. Type and size

2. Shape as to the cross-section

3. Materials

As to the kind of materials:

1. Timber pile

2. Concrete pile
3. Metal pile

109

CHAMFERED POINTED SQUARE

TIMBER PILES

WOOD PILE

Fig ure 6- 7 ·

6-9 THE IMPORTANT FUNCTIONS OR USES OF PILES

The decision to use pile foundation is the result of scientific
method of exploration and tests of the underlying soil conducted
by the designing Engineer which were brought about by any of the

following purpose:
1. As friction pile at their bottom portions in transmit·

ting the load through soft strata into stiffer lower strata.

2. As friction pile utilizing its full length.
3. As soil compactor.
4. As end-bearing columns
5. As stabiHzers of banks
6. As better piles
7. As a dolphin
8. As sheeting

Unless batter piles are intended to be effective in serving any

one of these functions, they should not be used, otherwise dri-
ving piles without any purpose will be an exercise in futi.lity.

110

Soft"'...,,., Friction

sOft material load~rrying

or soil "'bje(t . material
to scour

Rock friction
load-earrylnl
materiaf

A• End·Bearinc A$ Frl~:tlon Pile& A$ Friction Piles
Columns In ~r Poltlon\ for Full length

looaa
mettfitl

As Stabilizers of Banks As Soil
Compactor$

·,.

As Batter Piles, Fender Piles,
Dolphin,, and Sheeting

Uses of pilea.

Figure 6- 8

111

6-10 QUALITY AND DURABILITY OF PILES

Pile should be selected properly to possess a quality capable of
resisting without damage to the following:

1. To resist crushing under vertical load
2. To resist crushing during the process of driving. Timber
piles are not susceptible to withstand high stresses due to hard
driving that requires a desirable penetration on a highly resistant
layer. In driving piles, it is very important to select the right type
of hammer and the number of blows to prevent breakage and create
damage on the pile head, piles driven by steam hammer at 15,000
ft. pound (20,340 joules) energy should not exceed three to four
blows per inch or 25 mm. to prevent breakage or brooming of the
piles, the normal resistance of pile is from 6 to 8 blows per inch
or 25 mm. which is normal and commonly specified.
3. To resist handling stresses. Timber piles should be capable
of resisting breakage or other damages that may result from hand·
ling, hauling and impact in loading or unloading.
4. To resist tension from uplift forces, heaving of soil or re·
bound in the process of driving. Timber piles shall be strong
enough to counteract the uplift forc~s and expansion of soil
including the rebound action received in the process of driving.
5. To resist horizontal and eccentric forces that will cause
bending when applied on it.
6. To resist curvature bending and column action for the por-
tions not receiving lateral support from the ground when freely
standing in air, water or a very liquid mud.

Pile Selection

In selecting the use and types of piles the following factors
are considered:

1. Availability of supply 8. Carrying capacity

2. Expected life span 9. Proximity of structure

3. Deterioration condition 10. Cost

4. Types of underground

5. Method of placing

6. Length of piles

7. Characteristic of structure and ,loading

112

Economic comparison should be based on the cost of the
entire foundation instead on the cost of the pile alone.

6-11 TIMBER PILES

Timber pile is not new in the field of construction. Vitruvius
in his writing described the Roman builders to have been using

timber piles in their foundation work as early as 58 A.D. It shows

that even the early builders during the Roman Empire dispensation
have recognized the importance of providing a structure with a
strong foundation. The use of stone, bricks and· cemented slab
footing have already been employed by the Egyptian, Romans,
Babylonians and the Mayan and Yucatan builders. The discovery of
cement by the Romans associated by the demand for a massive
structures have prompted the early builders to study the nature
and behavior of soil in carrying a massive load. It is during this
stage that timber piles were introduced in making foundation. With
the advent of power equipment used in building construction, pile
driving would not be difficult as that of the Romans way of driving
piles crudely through manpower.

TABLE 6- 2 WOOD PILE LENGTH AND DIAMETER

Diameter of Butt (em.) Minimum Tip
Diameter em
Length of Pile Min. em Max em

Under 12 meters 30 45 20
13m to 18m 32 45 18
Over 18 meters 35 50 15

The diameter of the piles shall be measured in their peeled

condition. When the piles is not exactly round, the average mea-
surement may be used. The butt diameters for the same length of

pile shall be uniform as possible. Piles shall be peeled removing atl
the rough bark and at least 80% of the inner bark and no less than
80% of the surface on any circumference shall be cleaned wood.

No strip of inner bark remaining on pile shall be over 2 em. wide

and 20cm.long. All knots shall be trimmed close to tl'le body of
·the pile.

113

6- 12 DETERIORATION OF WOOD PILES

Wood piles are subject to deterioration caused by decay, insect
attack, marine borer attack, mechanical wear and fire. Timber
piles are said to be durable when driven below the normal water
level, on the otherhand, the life span of timber pile above water
!J level even if treated with creosote under pressure will only last for

a duration of about 40 years. Tirriber piles penetrated by salt

water are subject to deterioration caused by marine organism called
Teredo and limnoria. Wood piles under attack by marine borer
maybe terminated within a few years under extreme favorable
condition of which no amount of chemical treatment could cure
in any manner.

6-13 PROTECTION OF TIMBER PILES:

The methods of wood protect ion depends upon the local con-
ditions, types of expected economic life of the structure, severity
of service, e(!se of repairs, costs, etc. The two methods applied in
eliminating or reducing wood attack are:

1. Poiso ning the wood by creosote through pressure

treatment.
2. Mechanical protection.

Untreated wood piles is capable of resisting decay indefinitely
if d riven below the normal water table. CreosOte treatment protects
the outer surface of wood through penetration of the chemical
that ranges from 20 to 25 mm. Piles shall retain preservative in at
least the amount given in the following table.

TABLE 6-3 MINIMUM PRESERVATION PER CUBIC METER

OF WOOD

Uses and Type Type of Processing
Empy Cell Process Full Cell Process

General Use 190 Kg. 320 Kg.
Marine Use 200 Kg.
350 Kg.

114

6- 14 PILE DRIVING

Before driving piles, adequate knowledge and preparation had

already been made such as. gathering of data, underground explora-

t ion and soil tests and the use of pile which were brought about by

the result of the struct ural design. Driving of pi les involves some

considerations which some of them are enumerated as follows:

1. The timber pile to be used shall be free from sharp, short

or reverse be~d because crooked piles with sharp bend will only

create trouble during t he process of driving. ,

2. See to it that the taper of the pile shou ld be uniform from

the butt to the tip.

3. The butt of the pile should be square or chamfered to fit

in the pile cap.

4. The t ip of the pile is either pointed or squared. Pointed

t ips sometimes cause the pile to drive out of vertical position that

in most cases square tip is preferred.

5. Timber pile shall be driven by the right type of hammer
because it cannot resist high stresses due to hard driving lthat is
required to penetrate highly resistant layer of soil. Timber piles
could not be driven against a very h igh soil resistance without
damage and are rarely specified to receive driving load in excess of
(30 tons) 298 kilonewton but usually restricted to (25 tons) 250
KN or less. The tip of the timber pile which could be easily
damaged is protected by t he use of steel shoes, on the otherhand
the butt is also provided with an ample protection by the use of
cushion block.

6. Pile cushion should be attached at the hammer base in
order to reduce the impact stresses and at the same instance pro-
long the life span of the hammer. The hammer is rat ed based upon
the energy per blow where the rated energy is the product of the
weight of the ram and the height of the fall less the friction energy
loss on the ram guide.

Driving hamm~r dif fers greatly in the manner in which they
deliver energy to the anvil or hammer cushion. The ham111er
cushion are of two different types, the soft and the hard type.
The soft type is sometimes made of wood and asbestos which are
very common although there are other types being developed. The
hard type cushion contains alternating disks of aluminum and
micarta which is considered to be efficient in its performance after

l15

several use while others which are of low quality such as wood

chips or coiled steer cable are rarely specif ied .

T he pile cushion elements does not only protect t he top of
the pile as well as the hammer from t he high stresses but also deliver
significant influence on the wave stresses that is being developed
in the process of pile driving such as:

a. It affects the driving characteristics of the pile
b. The depth to which it can be driven
c. The load carrying capacity

The selection of the type and dimension of cushion block that.
gives satisfactory result including the type of the hammer are of
two categories:

a. To assure a maximum driving force in the pile equal to
the maximum capacity of the pile without overstressing the pile.

b. As much as possible to transmit the maximum energy
of the hammer to the pile.

The lack of contro l an d selection .of the right cushioning
materials which is usually recommended by the manufacturer in
their catalogue of the types of cushion block for a certain driving
hammer will permit a degree of subterfuge or escaping of the
device t o avoid impact force.

7. Driving sequence of pile shall be given attention for it
might affect the penetration of the pile into the ground. The
central piles in a group shall not be left until the last has been
driyen to a definite depth, o therwise, this might be dangerous to
cause damages to th.e piles previously driven.

8. Driving piles near a reta ining wall should be given careful
attention for it may cause displacement and damage t o the adjo in·
ing struct ure due to the vibration of the soil.

9. Over driving indicates bending of piles, hammer bouncing,
cutting of driving plate into the pile and separation of wood along
the annual growth rings which causes head brooming. Careless
driving procedure such as unusually hard compaction of the cushion,
block tilting of the head cap, non axial blows and uneven pile
head causes damage to the pile. The head failure due to impact
of driving could be prevented by banding before drivi.ng.

116

' - --A-1...:.
PlL'E. DRIV\1-16

Figure 6 - 9

TABLE 6-4 PENETRATION RESISTANCE AND SOIL

PROPERTIES BASED FROM THE STANDARD PENETRATION
TEST

Sand Clay
Fairly Reliable Rather Unreliable

Number .of blows R~lative Number of blows

per meter Density per meter :Consistency

0-12 Very loose 3 very soft
12-30 loose 6-12 soft
30-90 medium 12-24 medium
90 - 150 dense 24-45 stiff
over 150 over 90 hard
very dense

TABL£ 6-5 RANGE OF SKIN FRICTION FOR VARIOUS

SOIL

1. Silt and soft mud ... .... . 240 to 480 kg.jsa.m.
2. .Silt compacted • • . . •....
3. Cl.ly and sand .. ••..•.... 580 to 1,700 kg.jsq. m.

4. Sand with some clay ••.. •. 2.440 to 4,880 kg./sq. m.

5. Sand and Gravel . . . . .... . 1,950 to 3,900 kg./sq. m.

2,930 to 4,880 kg./sq. m.

117

6 -: 15 CONCRETE AND PIPE PILES
Concrete piles are class ified into two types:

1. Cast-in-place 2. Precast piles (prestressed)

a. cased
b. uncased

CUed piles- is cast inside a metal shell form which are left in

the ground.

Uncased piles - eliminate the metal casing or shell which in-
variably reduces the cost. The methods of construction are as
follows:

· 1. An open end pipe is driven into t he ground, clean it out
then f ill the hole with concrete and finally, the pipe is withdrawn.

2. Heavy drive is dragged into the ground by dropping a ham-
mer directly on plug of fresh concrete. The pipe is removed pro-
gressively as additional concrete mixture is rammed inside the pipe.

3. Pumping concrete under continous pressure through a hol-
low shaft of an auger, the hole is drilled by an auger which is then
pulled out f rom the ground. Consequently concrete is then pumped
into the shaft .

4. Pipe piles usua lly has a diameter of 25 t o 75 em. with a
thickness t hat varies from 2.5 to 4.5 mm.

J;K,,., _{)ti""

co,.. IMo.J

Tltilt·
tW>/4Jtf

P'l"

._...,__fwr~..~ - -1 C#MIV,. C<>rr~tr~ Pr!dulol _.,.,.,..
ff>ilt cylt'nllrl~tll l'rm.ittd,.. in(F)
...,..,,-~-6~,,t,i_tttl,drf;,'·.,.,,.Ct,,l,l .. ........~~-..,-.·..-.~.,._
~'"' *u
#/tou/11,,... IV--
. (!VaJ""Dt>d) d~ iltlo
._... ,_,._.,,.,.,...-~-.~y
p/Uif ~·h>l "Y
~,-.~
Dr,..,, <D'Vt s~ll, dr1~n ~~
tiMNHy -f'IINJ Flu~,.,_..., -·"'·(,,.,..,.,
tNilltdi'GWI'J I¥1Y't ~JtP'f'"dOIJir off,_h~ $/s,l( dri_.

m.-dr;l

- t>itH IJ'l/f'(f frip~tit9 lfiJ,.. Slt,l/lilkd willloul

wilht:'OI'tcr.-IC'. 1>,61>•H. w illt'I:D<nc-.hl. ttrtlnd,.;l.

fllrm~o) (Cob;} (rr.anlri) (MonolviM'

Figure 6 -10

118

6-16 PRECAST CONCRETE PILE

Precast concrete piles are reinforced to resist high stresses ·
caused by the hammer in driving. Precast pile reduces tension
cracking caused by handling and driving. This type of piles are
~ighly resistant to deterioration even when used above the normal
water table. The presence of high concentration of magnesium or
~dium sulphate salts in the water may cause deterioration of the
ieinforcement in the piles through cracks, or thin protective c;on-
rete covering. Covering will spall-off as rust continues to develop.

co(a) steel bonds
welded to reinf.

. (b)

I'

0I

I

I (c )

a) COMMON T 'fPE USEO FOR BRIDGE TR E. STLES.

b) FUENTES PILE.
e) 8RUMSPILE PRESTRESSED CONCRETE PROVIDED

WITH ORIVING FIT OF STEEl.. HR·RULE.

Figure 6 - 11

6- 17 DETERIORATION OF CONCRETE PILES

1. Deterioration above the ground is caused by weather and

air borne destructive elements.

2. Underground deterioration is not common unless water

contains destructive alkali, acid or salt. Other destructive elements·

may come from the chemical and industrial manufacturing plants.

3. Deterioration in sea water is caused by mechanical and

chemical action

4. Damage due to handling and driving of the concrete pile.

5. Defects in the manufacture of concrete pile. ·

6-18 METAL PILE

Metal is an excellent material for pile because of its strength

character.istics to withstand hard driving and rapid penetration

into the ground, relatively with small material displacements. The:

different metal piles used in building constructions are: 1

1

i

1. H-piles which are suitable in penetrating into rocks or any·.

hard materials with ease in driving and least effect in time. .,

2. Box pile- is suitable materials for pile on sliding bank or 1\

in deep water. .

3. Rail piles - the railroad rails are used by welding 3 rails \

~ogether at head and base to form a unit pile. i

1

I

\
i

I

H·"IU 1.,

•• u H I

= I

I

I

1

Figure 6 -12

6-19 DRIVING EQUIPME.NT I

The. early builders in their way of driving piles used mauls, I
ratchet winch rams, treadmill drivers, water wheel drivers or gang
operated rams. The first modern steam pile driving machine was I
invented and introduced by Nasmyth in 1845 designed as a drop
hammer for wood piles which was then modified into a handle I
single acting hammer. At present, piles are driven into the ground
by means of a hammer or a vibratory generator. The hammer it
operates between a pair of parallel guide suspended from a standard
lifting crane. The bottom of the guides connected at the base of 1
the crane boom by means of a horizontal member called spotter.
The spotter is adjustable to permit a plumb position of driving i
piles and the hammer is axially guided by steel rail which was i
incorporated in the guides. 1

1

120 1

{

1

I

TABLE 6-6 PROPERTIES OF SELECTED IMPACT PILE HAMMERS

Rated Energy Make Model Stroke Weight
Joules ft·lb
Blows at Rated Striking
Typea Per Energy Parts

Minuteb (em.) (Kg.)

9,844 7,260 Vulcan 2 s 70 73 1,363
1,186 8,750 MKTC 42 727
1,776 13,100 MKT 983 DB 145 47 1,363
15,000 Vulcan
20,340 15,100 Vulcan 1083 DB 105 90 2,272
20,475 1 38 2,272
s 60
50C
OF 120

21,696 16,000 MKT DE-20 DE 48 243 909
24,679 DE 86-90 90 1,818
25,967 18,200 Link-Belt 440 DE 95 47 2,272
26.442 OF 100-110 40 2,954
26,442 19,150 MKT 118 90 2.954
s 60
19;500 Raymond 65C

19,500 Vulcan 06

30,374 22,400 MKT OE-30 DE 48 243 1,272

30,510 22,500 Delmag D-12 DE 42-60 243 1,250
33,052 24,375 Vulcan 0 3,408
s so 97

33,086 24,400 Kobe K13 DE 45-60 259 1,304
33,154 24,450 Vulcan
soc OF 111 40 3,636
-----
s 50 97 3,636
35,256 26,000 Vulcan 08

35,662 26,300 Link-Belt 520 DE 80-84 110 2.304

43,392 32,000 MKT OE-40 DE 48 243 1,818
44,070 32,500 MKT 97 4,545
44,070 32,500 Vulcan SlO s 55 97 4,545
010 s
50

44,070 32,500 Raymond 00 s 50 97 4,545

48,816 36,000 Vulcan 140C OF 103 38 6,363

53,833 39,700 Delmag D-22 DE 42-60 97 5,681
55,053 40,600 Raymond 000 2 204
s 50 243
56,002 41,300 Kobe
K-22 DE 45-60 259 2,204

s56,952 42,000 Vulcan 014 60 90 6,363
s66,105 48,750. Vulcan 016
60 90 7,385

S a • single-acting steam; DB= double acting steam;
OF • differential Acting steam; DE= diesel.

b = after development of significant driving resistance.

c =for many-years known as McKiernan-Terry.

121

The different types of driving equipment are:

1. Drop hammer or impact hammer
2. Air or Steam hammer

a. Single acting hammer
b. Double acting hammer

3. Differential acting hammer
4. Diesel hammer

Drop Hammer - usually falling on the fresh concrete as in the

installation of franki pile (Figure 6-10)

Air or su-n Hammer - operates by litting .a- ram by air or

steam pressure then allowed to fall by gravity with or without the
pressure of air or steam. If the fall is due to gravity alone the

hammer is classified as Single Acting.

If air or steam pressure supports the downward fall, the ham-
mer is said to be DoW,Ie Acting or differential depending upon t he
detail of the construction.

DieseJ Hammer- are of two types:

a. Open ended
b. Closed ended

Open Ended Type - the ram falls by gravity and lifted by

the explosion of fuel and compressed gas in the chamber
between ~he bottom of the ram and tt:le anvil block at the
housing base.

Closed Ended Hammer - the housing forms a bounce

chamber where air is compressed by the rising ram, the com·
pressed air then acts as spring that control the rise of the ram
and thereby shorten the stroke, the stored energy returns the
ram to downward stroke.

Too. high pressure will cause the hammer to jump off the

pile, such behavior is known as racking which usually cause

damage to the equipment.
The weight of the ram including its height of' fall plus

other informations regarding the different types of drivng
equipment are shown on Table 6-6.

122

..~........e.tt

CUs.tiO.
Ol'r.tt HIEAO

Pit,.£ tVSMM*

.,.... _. OPf 10trfAl.
a IIIIILI:• KTM ITUM IJ 011••111010 DIIIIL M - ·

Figure 6- 13

TABLE 6- 7 CUSTOMARY RANGE OF WORKING LOADS

IN DRIVING PILES . Load in tons

Type of Pile

Timber 8 fnches or 20 em. tip diameter 15-20
Concrete precast or prestressed
25 - 60.
10 in. - 25 em. diameter 60-200
18 in.- 45 em. diameter
30'7 50
Steel Pile or shell, concrete filled 45 - 70
not mandril driven 50-80
60- 90
10314" x .188 pipe 100-200
1()34" x .250 pipe 100-120
10¥4" X .250 p ipe
50- 70
123/4' x .250 pipe
14 x .312 pipe. so- ·go
16 x .375 pipe
100- 150
Steel H section 150-200
HP lO .x 12
HP 12 X 53

HP .14 x 89

HP 14 X 117

123

6-20 PILE SPACING

The efficiency of the pile in serving the purpose for which it
was intended should be maximized not only through proper selec·
tion of the types and length, the correct type of driving hammer
nor the right way of driving application but also the spacing which
also plays an important role in the efficient performance of the pile
in supporting superstructural load. ·

A. The effect of too close pile spacing are:

1. Creation of large horizontal pressures in driving

particularly on a relatively uncompressible underground layer

which sometimes cause damage to t he piles being. driven or

that has already been driven. .

2. The carrying capacity of the soil where the group
of piles acts may be less than the whole sum of the fractional
capacities of the soil that encloses the individual piles if too
closely spaced to each other.

B. The effect of wider spacing of piles:.

1. Wider spacing has the tendency of readily perm it-
ting the latter piles in group to penetrate the same depth of
the first pile which in effect gives uniform bearing and settle-
ment.

2. Wider spacing of piles reduce heaving and tension
damage including the possibility of crushing the outer surface
of the piles.

3. The value of the group may be increased and the
piles serves efficiently if spacing is increased.

Piles intended to serve a marine structure which are exposed
to receive wave action should be spaced at a min imum of 5 times

its diameter apart to'reduce countercurrent, whirlpool and abrasion.

6- 21 DRIVING OF PILES THROUGH AN OBSTRUCTION

In case of obstruction met during the pile driving such as
boulders, rocks or thin stone strata, an advance rod sounding jets
or diamond drill rigs is advanced before driving wood piles.

124

Pilot pile is also used before driving timber or concrete pile, an
beam, H pile or mandrell is used for this purpose. Spudding is
also applied by raising and lowering the piles with heavy precast
piles every after little driving progress.

There are several methods applied in placing piles such as;

1. By driving 7. Washing O!-!t
2. Jetting
8. Sand pumping
3. Boring
4. Ramming 9. Blowing out
5. Jacking 10. Coring
6. Pulling Down 11. Drilling
12. Explosive

,:

6- 22 CAUSES OF PILE DEFLECTION IN DRIVING

In the process of driving piles, deflection cannot be avoided

which causes the pile to penetrate the soil out of plumb. Deflec-

tion of piles during the process of driving maybe brought about by

the following: '

L Piles may glance-off to an obstruction or hit a scoping bed

rocks.

2. In soft clay, piles tend to bend toward previously installed

close-by piles due to the soil softening from remoulding during the

driving.

. 3. Bowing of the jet pipe caused by the weight of the hose

that causes piles in jetting group to penetrate out of plumb.

4. The lower portion of a batter piles sometimes tend to sag

and cau.ses curvature.

6- 23 SETTLEMENT OF FOUNDATION

The different causes of settlement due to loads imposed on the
soils are:

1. Soil bearing capacity failure including partial failure or

creep.
2. Failure or deflection of the foundation structure.
3. Shear distortion of the soil
4. Compression of the soil.

125

Other factors that contribute to the settlement or movement
of foundati.on are:

1. Subsidence due to mines or caves beneath the surface
2. Subsidence due to underground erosion
3. Landslide and creep of the underground
4. Vibration and shock of loose cohesionless soils
5. Lowering of the water table
6. Soil shrinkage by dessication or exhaustion or increase of

soli mixture
7. Lack of lateral support in excavations
8. Heave or swell - slow movement due to horizontal dis-

placement of soil vein or stratum

9. Chemical Action·- this includes decay of materials

The settlement caused by these factors are considered as in-
directly related to the superstructure load imposed on the soil.

. .6-24 FAILURE OF PILE FOUNDATiON
The failure of the pile foundation may result from any of the
following causes:

1. Lack of adequate boring
2. Inaccurate soil classification
3. Soft strata under tip of pile
~. Inadequate driving formula (wrong data)
5. Improper size of hammer cause insufficient penetration,

too light or damaged if too heavy
6. Misinterpretation of load
7. Damaged ofencased piles
8. Buckling of piles
9. Breaking of piles
10. Vibration that cause'lateral or vertical movement

11. Flowing strata caused by adjacent excavation or bank

sloughing
12. Tension failure of concrete pile for lack of reinforcement

13. Eccentricity due to bowing or falling out of plumb
14. Decay due to lower ground water level
15. Insect and marine borer attack and corrosion
16. Disintegration of concrete due to poor quality of concrete

126

or reactive aggregate
17. Collapse of the thin shell of the piles
18. Overweight due to earthfill.

REMEDIES:

1. Early repair such as encasement or replacement
2. Removal of partial load
3. Underpinning

6-25 GRILLAGE 'FOOTING

The early attempt to increase the area of footings and to mini·
mize the load was made possible through the introduction of gril-
lage footing to replace the oldest way of building foundation by
the use of masonry structure made out from various sizes of stones
joined by mortar. With the advent of reinforced concrete at the
early part of 1900, grillage footing became obsolete. Almost all
constructions are now dominated by the use of the new materials.

JC
Wf'

GRILLAGE fOOTING

Figure 6-14

12·7

fCHAPTER

SOIL TEST

UNDERGROUND EXPLORATION

Foundation design is primarily based from the result of sub-
surface investigation. The Engineer who has to make the design
must have a reasonably accurate conception of the physical pro--
perties and arrangement of the underlaying soil. The most suitable

method under a wide variety of soil conditions is by drilling a hole

into the ground and extracting samples for identification or testing.
The investigation of the underlaying materials as to its consistency
or relative density of the deposit could be made by penetration
test or other methods which do not require sampling.

7-1 AUGER BORING

The simplest device for boring a hole in the ground is the
Auger. The two varieties of hand auger commonly used for soil
investigations are the helical auger and the Iwan or post hole auger.
A portable power driven helical augers are available from 8 to
30 em. oftenly used for making deeper holes.

.. IWAI&OR POST
HOL£ AUG£R
WASH BORING
Figure 7-1

7- 2

The methods applied in wash boring is to drive a piece of
metal tube of 5 to 10 em. diameter to a depth of 1.50 to 3.00 m.,

128

the tube or casing is cleared out by a chopping bit fastened to the

lower portion of the wash pipe inserted inside the tube or casing.

Water is forced down through the wash pipe by means of a high
velocity pump to rinse the fragments of soil through the annular

space between the tube and the wash pipe. This method is similar

to the process of installing an underground water pump where the

pipe is cleaned by wash pipe and water. ·

7- 3 HOLLOW STEM.AUGER BORING

A truck mounted driving rigs turn the auger into the soil
rapidly to a depth of more than 60 meters using continuous flights
of auger with hollow stem where sampling tools are operated.
Auger with 6 or 8 em. diameter are commonly used.

II.I.IGER SMAFT t~EF'<RIC~

SAhiPLEIIt \LEGS OF PIPE
ROD

2 CHOPPH4G BIT
REPL ACEO BY
HOLLOW- STERN AUGER I PLI!O WHilE ADVANCING SAMPLING SPOON
AUGER.2 PLU<I liE MOVED 1>"0 !SAMPLE~~ ltiSER1ED
WASH 80RtN G
i'O GET SAio'Pt.E Of SOIL.

Figure 7- 2 F1gure 7- 3

7-4 ROTARY DRILliNG

Is the most rapid method for penetrating highly resistant
materials such as rocks, clay or even sand. The rotary boring dia-
meter ranges from 5 em. to 20 em. (2 to 8 inches).

1.29

t4rf4f'

::.~:~~.}!~~,.~

Fiqure 7- 4

7- 5 PERCUSSION DRILLING

Percussion drilling is sometimes called cable tool drilling used
when wash boring or auger boring could not penetrate exception-
ally hard strata of soil or rocks.

7- 6 PENETROMETER

A device used to investigate and measure the consistency of

cohesive deposit or relative density of cohesionless strata without
the necessity of drilling and getting samples. If the penetrometer is
pushed steady into the soil, the procedure is called Static penetra·
tion test, when driven into the soil it is called Dynamic Penetration
Test.

Static Penetration test is preferred for cohesive soil while
Dynamic penetration test is good for very hard deposits. Both
give satisfactory result for cohesionless soil. Standard penetration
test is the most widely used in the United States; it is done by
dropping a 60 kg. hammer into a drill rod from a height of .70 m.,
the number of blows to make a penetration of 30 em. is regarded
as the penetration resistance.

7- 7 DUTCH CONE PENETRATION

A 600 cone with a base area of 10 sq. em. is attached to the
bottom of a rod protected by a casing, at a rate of 2 em. per
second, the cone is pushed by the rod into the ground, the cone is
slightly. larger than the pipe to minimize friction. Another method

130

of soil testing by means of a cone penetrometer is by driving a
drop hammer into the ground with constant height of fall, the
number of blows per 30 em. penetration of the point is con·
tinuously recorded and when the point reaches its final depth.

the pipe is withdrawn and the cone is left at the bottom of the

hole. The dutch cone penetration test is the most rapid and eco·
nomical method being adopted recently.

R~o
tASIN(i

Figure 7-5

COIIt

7- 8 VANE SHEAR TEST

The vane aparatus for shear testing clay soils in place consist
of four vertical rectangular blades bolted at right angles to a ver~
tical shaft. The vane is pushed into the soil and then twisted until

the soil is ruptured in a cylindrical form, shear strength is com-

puted from the maximum moment needed to rapture the soil
and the dimension of the soil cylinder.

Figure 7-6

131

7- 9 STANDARD LOAD TEST

The Building Code on load test so provides:
"Where the bearing capacity of the soil is not definitely

known or is in question, the Building Official may require
load tests or other adequate proof as to the permissible safe
bearing capacity, at that particular location. To determine
the safe bearing capacity of the soil, It maybe tested by

loading an area not less than .18 sq. m. (2 square ft.) to not

less than twice the maximum bearing capacity desired for use.
Such load shall be sustained by the soil until no a(jdltional
settlement takes place for a period of not less than 48 hours
in order that such desired bearing. capacity may be used.
Examination of sub-soil conditions may be required when
deemed necessary."

The load test procedures will be as follows:

1. Dug to the dep1 r of soi'l to be tested usually the proposed

footing level. ·

2. . The pit width should be at least 5 times the plate width.

3. The square plate with a general d.imension of .30 x .60 m

is set on a levelled bottom of the pit.

4. Place the load on top of the plate by a platform loaded

with concrete blocks, cement or jacking with a calibrated hydra-

ulic jack against a beam properly anchored down the earth.

5. Measure the settlement by the level instrument or by a

micrometer dial gage mounted on a support independent of the

loading system.

f6. Apply the load to an increment of about one tenth the

estimated failure load· or the proposed design load until com-

plete bearing capacity failure or twice the design load is reached.

7. Each ·increment is maintained constant which settlement

readings are made at regu lar but increasing interval such .as 1, 2, 5,

10, 20, 40, and 80 minutes. ·

8. The load test result express only the short term loading

of the model and not necessarily the long term loading of a full

sized footing. Extrapolation is necessary in order to be able to

use the data for design.

The results found in the load test requi re careful interpretation

for it may in some instances be· misleading specially if the subsoil

132

is not uniform for a considerable depth below the base of t.he pro-
posed foundation.

Figure 7·· 7

In determining the dimension required for a foundation, it is the

designers responsibility and duty to ascertain first the allowable
bearing capacity of the soil. The local Building Code authorities
should be consulted of the allowable bearing capacities to be
adopted in design. In the absence of such information, boring or

load test is necessary. Table 7·1 is presented for reference pur-

poses.

TABLE 7- 1 ALLOWABLE BEARING CAPACITY OF

VARIOUS SOILS

Underground Kg. per pounds per ton per kilopascal!
classification
sq.m. sq. ft. sq. ft. k Pa

A.lluvial soil 4,891 1.000 1k 54
Sof clay 9,782 2,000 1 107
Firm Clay 19,564 4,000 2 215
19,564 4,000 2 215
Wet sand 19,564 4,000 2 215
Sand and Clay mixed 29,345 6,000 3 322
Firm Dry sand 39,128 8,000 4 430
Coarse dry sand 58,690 12,0001 6 644

Gravel 78,256 16,000 8 860
Gravel & sand well 97,818 20,000 10 1,073
195,636 40,000 20 2,146
cemented 244,545 50,000 25 2,681
Hardpan or Hard shale 782,545 160.000 80 8,580
Medium Rock
Rock under Caisons
Hard Rock

133

8CHAPTER

POST AND COLUMN

8-1 DEFINITION
Post"" Refers to a piece of timber of either cylindrical, square

or other geometrical cross section placed vertically to support a
building; a compression vertical member not continuous from
story to story is also called post.

Column = Refers to a vertical structure used to support a

building made of stone, concrete, steel or the combination of the
above materials.

Story = Is the space in a building between floor levels or

between a floor and a roof above.

8- 2 WOODEN POST

Unlike other parts of the building that could be easily replacea,
wooden post shall be selected out from the best quality of lumber
under the classification of the first or second group for strength
and durability. Treated lumber is also used as wooden post in the
absence of hardwood lumber.

Wood post are erected in the following manner:

1. After dressing the wood post, the bottom portion is
evenly cut with the atd of the steel square.

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

length of the post connecting the opposite end. This
marking will serve as the reference line for checking its
vertical position.
3. From the bottom of the post, indicate -the distance
where the girder and girts will be attached and make
the necessary dap before its erection.
4. The post could be erected manually with the aid of
2 x 3 lumber braces or by the use of rope and pulley
anchored on a jump-pole.
5. Check the vertical position of the post on two sides by
the aid of plumb-bob. Have it braced on four sides and
~ail the wooden post temporarily to the post strap.

134

6. With the use of boring tools. dril1 a hole across the two

straps and have it bolted to its per~anent positions.

- -·P...JM~L;n~t
._ _.. ..._..... ..~-H

· fi:of>• M
Bof Clomp

... 'I

I j· I r·Jt j_ ·1

IL 1-- --- ·l

'- -· -_I bl CORRECTING TNE 8E ND
POST
ol EltlCTION OF WOOO POST

Figure 8-1

TABLE 8- 1 DIMENSION OF WOODEN POSTS OR SUPORTALES

Maximum Maximum Maximum Required Maximum

Types of Building Height of Height Spacing Finished Size of

1st Floor Total (m) of Post (m) Suportales

1 storey shed 4.00 3.50 10 X lOcm ·
1 storey shed 3.00
1 storey shed 5.00 4.00 lOx lOcm

1 storey house or 5.50 4.00 12.5 x 12.5 em
6.00
chalet l.OOm 7.00 3.60 12.5 x 12.5 em
8.00
2 storey house or 3~00m .9.00 3.00 12.5 x 12.5 em
2 storey house
4.50m 4.00 12.0 x 15.0 em
2 storey house 5.00m
2 storeyhouse 4.50 17.5 x 17.5 em

4.50 20.0 x 20.0 em

'11i:

Logs or tree trunk supportales may be utilized as post in its
indigenous traditional type of construction, provided, that they
are of the sizes and spacing capable to sustain vertical loading
equivalent to the loading capacity of the posts and spacing as pro-
vided for on Table 8-1.

COMMENTS:

Bent post could be corrected in the process of construction,

but no att6mpt should be made to correct the bent unless proper

bracing and adequate support be made first, otherwise, the found-

ation pedestal might break-up during the operation. The usual

failure of this nature is the crushing of the pedestal brought

about by the twisting of the wrought iron post strap. ·

At present, the trend is to avoid the use of wooden post in

building construction under the following considerations:

1. Reinforced concrete column appears to be cheaper and

durable.than the wood post.

2. Commercial lumber nowadays are taken from young

trees thereby producing inferior quality of lumber.

3. Hardwood is scarce and could hardly be found in big

lumber or sawmills. ·

4. The cracks between the wooden post and the concrete

wall is inevitable aside from its prominence on the wall

· finished.

5. Wooden post is susceptible to decay brought about by

moisture insect, worms, termites and the like.

8- 3 REINFORCED CONCRETE COLUMN

Reinforced concrete is at preseRt the most popular and widely
used materials for column of buildings instead of wooden post
regardless of its size or height.

Reinforced concrete columns are classified as:

1. Short Column = When the unsupported height is not
greater than ten times the shortest lateral dimension of the
cross sect ion.

2. long Column = When the unsupported height is more

than ten times the shortest lateral dimension of the cross
section.

136

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

!--Lateral
t1es

Tied Column Spiral Column Composite Column Combined Column

Figure 8 ·.2

8- 4 TIED COLUMN

T.ied column· has reinforcement consisting of vertical or longi-
tudinal bars held in position by lateral reinforcement called lateral
ties. The vertical. reinforcement shall consist of at least 4 bars
with a manimum diameter of No.5 or 16 mm steel bars.

Lateral ties= The ACI Code so provides:
"All non-prestressed bars for tied column shall be enclosed

by lateral ties of at least No. 3 in size for lon9.itudinal bars No.
10 or smaller and at least No. 4 in size for No. 11, 14 and 18
and bundled longitudinal bars. The spacing of the ties shall not
exceed 16 longitudinal bar diameter, 48 tie bar diameter or the
least dimension of the column".

The Code is specific that 13/8") or 10 mm diameter steel bar
shall be used as lateral ties for a column reinforced with 32 mm or
smaller longitudinal bars. Likewise, 12 mm steel bar shall be used
as lateral ties for column with longitudinal reinforc'3ment having
a diameter from 36 to 57 mm including those longitudinal bun-
dled bars.

137·

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

three factors:
1. Should not be more than 16 times the diameter of the
longitudinal or main reinforcing bar.

2. Should not be more than 48 times the diameter of the

lateral ties.
3. Not more than the shortest dimension (side) of the column.
To find the spacing of lateral ties required for a tied column,
the following illustration is presented:

Hlustration:

Determine the spacing of the lateral ties for a tied column
as shown on Figure 8 - 3.

0- -lG,.m ~.20"""~ .fO '"'·

---IDN•m IQ.,..rn ...J

\

Figure 8-3

Solution:

a. The diameter of the longitudinal bar is (3/4"1 or 20 mm
The diameter of the lateral ties is (3/8") or 10 mm

b. Multiply: 16 x 20 mm =32 cm ·

c. Multiply: 48 x 10 mm ::= 48 em

d. The shortest side of column =30 em

From the result·of the above computation, it could be readily
seen that the least value found Is 30 em. therefore, the spacing of
the lateral ties will be af 30 centimeters on center.

When there are more than 4· vertical bars in a tied column,
additional ties shaU be provided in order to hold the longitudinal
bars firmly to its designed position. The Code further states:

"the ties shall be so arranged that every corner and the
alternate longitudinal bar shall have lateral support provided
by the corner of the tie having an inclined angle of not more
than 135 degrees and no bar shall be farther apart than 15 em
clear on either side from such a laterally supported bar."

138

[g] J[: J: ll ~

lo~ ;orran~ttntno> ~onfurllliftlt 111 ACI Coot .

JI. II ( ]

Figure 8-4

=Rein~ement Ratio 1nd Limitation The size and number of

tosteel bars be plac,ed in a tied co lumn is governed by the pro-

portion of its cross sectional area to the gross area of the column.

"The cross sectional area of the vertical reinforcement
shall not be less than .01 nor more than .08 times the gross
area of the column section.••

Illustration:

Find the .mm1mum and maximum steel bats that could be

placed in a tied column having a cross sectional dimension of

. ,. .-..(10" x 12") or 25 x 30em.
I{) · 29 Mt'l"'l ~

D-- ~·\C.mm .
MINIMUM REINFORCHIIEI/T

Figure 8-5

Solution:

A - Minimwn Reinforcement:

a. Solvo for the cross sectional area of the column,

25 x 30 =750 sq em

(10" x 12""' 120 sq in)

139