Week 4 Challenge

Week 4 Challenge

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Challenge

SShubhankar Chakravarty8 Oct 2022

Aim :- Design of Abutment foundation as per IRC 6, IRC 78 and IRC 112

1. Design the abutment foundation as per IRC 6 loads. Optimize the design as per IRC 112.

The load acting on abutment foundation are calculated by using Serviceability Limit State (SLS) and Ultimate Limit State (ULS) criteria methods. All provided details are given below.

Basic Design Data-

Span and Cross section			Unit

1	C/c of exp joint	14.4	m
2	C/c of bearing	13.4	m
3	Dist. Of bearing to exp joint	0.5	m
4	Total Deck width	12	m
5	Carriage width	9	m
6	Footpath width (One Side)	1.5	m
7	Width of Crashbarrier	0.5	m
8	Width of median	0.5	m

Superstructure Details

1	No fo girders	4
2	Spacing of girder	3	m
3	Cantilever on both sides	1.5	m
4	Depth od superstructure	1.22	m
5	Wearing coat thickness	0.065	m
6	Dist. of FRL from bearing of least height	10.9	m
7	Bearing thickness	0.065	m
8	Pedestal thickness	0.25	m
9	Bearing + pedestal thickness	0.315	m

Level

1	Height of Substructure	Assumption	6	m
2	Scour Level	MSL	226.58
3	Min. Founding level reqd		224.25
4	HFL		229.5
5	Clear cover for dirt wall		50	mm
6	Clear cover for abutment cap		50	mm
7	Clear cover for abutment stem		75	mm
8	Clear cover for foundation		75	mm

Material Used

1	Grade of concrete	fck M	35
2	Design strength of concrete	fcd	15.63
3	Grade of Steel	fyk Fe	500
4	Design strength of steel	fyd	434.78
5	Density of RCC		2.5
6	Density of Wearing coat		2.2
7	Coef. Of thermal expansion of concrete		1.2	E-05/ c
8	Shrinkage strain		2	E-04
9	Modulus of elasticity of Steel	Es	200000	Mpa
10	Modulus of elasticity of Concrete	Ecm for M35	32000	Mpa
11	Mean axial tensile strength of concrete	fctm	2.8	Mpa

Dimension of the abutment
			Unit
1	Length of the abutment at top	1.64	m
2	length of the abutment at bottom	1	m
3	Width of abutment	12	m
4	width of median wall	3.5	m
5	Width of footing	6.3	m
6	Width of heel	3.5	m
7	Width of toe	1.8	m
8	Heel thickness	1	m
9	Toe thickness	1	m
10	Stem thickness	1	m
11	Dirt wall thickness	0.3	m
12	Depth of abutment cap varying	0.3	m
13	Depth of abutment cap uniform	0.3	m
14	Return Wall thickness	0.5	m

Soil Parameter

1	Angle of shear resistance	30
2	Density of dry backfill	2	t/m3
3	Density of submerged backfill	1	t/m4
4	Net SBC	25	t/m5
5	Gross SBC (LWL)	33.42	t/m6
6	Gross SBC (HFL)	27	t/m7
7	Live Load surcharge	1.2	m
8	Type of soil	median	soil
9	Coefficient of friction	0.5

Dimension of the abutment

1	Length of abutment at top	1.64	m
2	Length of abutment at bottom	1	m
3	Width of abutment	12	m
4	Width of median wall	3.5	m
5	Width of footing	6.3	m
6	Width of heel	3.5	m
7	Width of toe	1.8	m
8	Heel thickness at root	1	m
9	Toe thickness at root	1	m
10	Stem thickness	1	m
11	Dirt wall thickness	0.3	m
12	Depth of abutmernt cap varying	0.3	m
13	Depth of abutment cap uniform	0.3	m
14	Return wall thickness	0.5	m

In the assignment partial safety factor are consider from IRC 6 Annex - B (clause no 202.3 ). It is consider for the verification of "COMBINATION OF LOADS FOR LIMIT STATE DESIGN"

Load Calculation

Dead Load and SIDL

Dead Load
		Load	unit
1	Total Dead Load of super structure	199	t
2	DL reaction on one Span	99.5	t

SIDL 1

1	Weight of crash barrier	28.8	t
2	Weight of media	14.4	t
3	Weight of footpath	16.2	t
4	TOTAL SIDL	59.4	t
5	SIDL 1 reaction one span	29.7	t

Summary of loads from superstructure

At Bearing Level

Load Item	P	ML	MT	HL	HT
Load Item	t	t-m	t-m	t-m	t-m
Dead Load	99.5	0	0	0	0
SIDL 1	29.7	0	0	0	0
SIDL 2	14.256	0	0	0	0

At abutment Shaft bottom level

Load Item	P	ML	MT	HL	HT
Load Item	t	t-m	t-m	t-m	t-m
Dead Load	99.5	0	0	0	0
SIDL 1	29.7	0	0	0	0
SIDL 2	14.256	0	0	0	0

At Foundation Bottom Level

Load Item	P	ML ( About toe)	MT (about footing C/c)	HL	HT	With Resp to toe
Load Item	t	t-m	t-m	t-m	t-m
Dead Load	99.5	228.85	0	0	0	2.3
SIDL 1	29.7	68.31	130.977	0	0
SIDL 2	14.256	32.7888	0	0	0

Live Load

1 lane 70 R (Wheeled)		Total	98.532	t
				Eccentricity in Transverse dieection
	Live Load reaction						length of the vehicle on vehicle ( L type)	2.79	m
1	Ra	66.152	t	Total width of deck	12	m	length of the vehicle on vehicle ( L type)
2	Rb	32.38	t	Half of total width	6	m	C/g of one vehicle	1.395	m
3	Braking force	19.7064	t	One side crash barrier	0.5	m	Min wheel spacing 2 lane	1.2	m
4	Change in reaction due to breaking force	4	t
5	Vertical force on abutment, Max	70.152	t	Total length of bridge (Except CB)	5.5	m	Total C/g of one vehicle	2.595
6	Vertical force on abutment, Min	62.152	t
7	Longitudinal Movement	0	t/m
8	Horizontal force = Fh/2	9.8532	t	Eccentricity if transver directio			2.905
9	HL	9.8532	t
10	Tranverse Ecentricity for 1 lane 70R (Wheeled)	2.905	m
11	Transverse movement	203.79156	t/m

2 lane Class A (Vehical)		Total	82	t
				Eccentricity in Transverse dieection
	Live Load reaction						length of class A vehicle	1.8	m	2	nos
1	Ra	63.7	t	Total width of deck	12	m	length of class A vehicle
2	Rb	18.29	t				Min distance between 2 vehicle	0.9
3	Braking force	16.4	t	Half of total width	6	m	C/g of one vehicle	0.9	m	1.8
4	Change in reaction due to breaking force	2	t				Total vehicle	1.8
5	Vertical force on abutment, Max	65.7	t	One side crash barrier	0.5	m	Min wheel spacing 2 lane	0.15	m
6	Vertical force on abutment, Min	61.7	t
7	Longitudinal Movement	0	t/m	Total length of bridge (Exceept CB)	5.5	m	Total C/g of one vehicle	2.85
8	Horizontal force = Fh/2	8.2	t
9	HL	8.2	t
10	Transverse ecentricity 2 lane class A vehical	2.65	m	Eccentricity if transverse direction			2.65
11	Transverse movement	174.105	t/m

Live Load Summery

Live load case	Max Load	Min load	ML	MT	HL	HT
1 lane Class 70 R ( Wheeled)	70.152	62.152	0	203.7916	9.8532
2 lane Class A	65.7	61.7	0	174.105	8.2

Summery

	At Bearing Level

	Load Item	P	Load (Min)	ML	MT	HL	HT
	Load Item	t		t-m	t-m	t-m	t-m
	Dead Load	99.5	-	24.875	0	0	0
	SIDL 1	29.7	-	7.425	0	0	0	0.25	m
	SIDL 2	14.256	-	3.564	0	0	0
	Live Load	70.152	62.152	17.538	203.7916	9.8532

Force at abutment bottom level

Load Item	P	Load (Min)	ML	MT	HL	HT
Load Item	t		t-m	t-m	t-m	t-m
Dead Load	99.5	-	111.44	0	0	0
SIDL 1	29.7	-	33.264	0	0	0	1.12	m
SIDL 2	14.256	-	15.96672	0	0	0
Live Load	70.152	62.152	78.57024	203.7916	9.8532

Force at footing bottom level

Load Item	P	Load (Min)	ML	MT	HL	HT	ML due to HL
Load Item	t		t-m	t-m	t-m	t-m	0
Dead Load	99.5	-	228.85	0	0	0	0
SIDL 1	29.7	-	68.31	0	0	0	0	2.3	m
SIDL 2	14.256	-	32.7888	0	0	0	0
Live Load	70.152	62.152	161.3496	203.7916	9.8532		-91.86

Earth Pressure Load

Angle of shear resistance	30
Density of dry backfill	2	t/m3
Density of submerged backfill	1	t/m4
Net SBC	25	t/m5
Gross SBC (LWL)	33.42	t/m6
Gross SBC (HFL)	27	t/m7
Live Load surcharge	1.2	m
Type of soil	median	soil
Coefficient of friction	0.5
alpha	90
beta	0
delta	20
ka	0.297
kah	0.279
kav	0.102
kp	6.105
kph	5.738
kpv	2.088

Normal case - LWL
Force due to Earth pressure	128.304	t
Lever arm, 0.42 H	2.52	m
Moment, ML	323.32608	tm

HFL case
E1	16.2	t
E2	109.5	t
E3	92.2	t
Total	217.9	t
ML	207.35	tm

Weight of Substructure

Description	Weight	Lever arm	ML	Lever arm	ML abt toe
	t	m	tm	m	tm
Abutment shaft	154.40		0.00	2.30	355.12
Abutment cap	26.64		0.00	2.30	61.272
Dirt wall bracket	3.71	0.97	3.61	2.97	11.026125
Dirt wall	9.63	0.67	6.45	2.97	28.6011
Total	194.38		10.06		456.01923

Weight of Substructure	194.38	t
Buoyancy on stem	-51	t
Long. Movement due to buoyancy	-117.3	tm

Weight of structure
Self weight of footing
Total Volume of foundation	53.34	m3
Total Weight of footing	133.35	t
Buoyancy force	-53.34	t
Lever arm	3.15	m
ML-foundation	420.0525	tm
ML-buoyancy	-168.021	tm

	Return wall
	Total weight				59
	Moment, ML				304.6

Design Checks

OVERTURNING STABILITY CHECKS
Load	Unfactoresd ML (t-m)		Factors	Resisting ML (t-m)	Overturning ML (t-m)
Dead Load	228.85	R	0.95	217.4075
SIDL 1	68.31	R	0.95	64.8945
SIDL 2 (Wearing)	32.7888	R	1	32.7888
Weight of Substructure	456.01923	R	0.95	433.21826
Weight of footing	420.0525	R	0.95	399.04988
Weight of soil above footing	3604.1	R	0.95	3423.895
Live Load	203.7916	R	0	0
Earth pressure load	323.33	O	1.5	0	-484.995
Earth pressure load	207.35	R	0	0	0
Live load surcharge	-453.5	O	1.2	-544.2	-544.2
Live load	174.105	O	1.5	261.1575	0
				MR	MO	Without Seismic Case	With Seismic Case
			Total	4288.211	-1029.195	Without Seismic Case	With Seismic Case
		FO =	MR / MO	4.17	SAFE	2	1.5

SLIDING STABILITY CHECK
Load	Unfactored HL (t)		Factor		p min (t)		Factor	Factored P min (t)
Dead load	0	R	0.95	0	99.5	R	0.95	94.525
SIDL	0	R	0.95	0	29.7	R	0.95	28.215
SIDL (Wearing Coat)	0	R	1	0	14.256	R	1	14.256
Weight of Substructure	0	R	0.95	0	194.38	R	0.95	184.663375
Weight of Footing	0	R	0.95	0	133.35	R	0.95	126.6825
Weight of soil above footing	0	R	0.95	0	1086	R	0.95	1031.7
Live Load	9.8532	S	1.5	14.7798	62.152	R	0	0
Earth pressure	217.9	S	1.5	326.85	128.304	R	0	0
Live load surcharge	85.4	S	1.2	102.48	0	U	1.2	0
			Total	444.1098				1480.041875
	Mu	0.5
		FS =		1.67		SAFE

Base pressure check
Area of footing, A = L X B	75.6	m2
Section modulus about trans. axis Zl ( L x B2) /6 =	79.38	m3
Section modulus about Long. axis Zt ( B x L2) /6 =	151.2	m3

Load for base pressure
Loads	P MAX	P MIN	ML	ML DUE TO P	MT
Dead load	99.5	94.525	0	228.85	0
SIDL	29.7	28.215	0	68.31	0
SIDL (Wearing Coat)	14.256	14.256	0	32.7888	0
Live load	70.152	62.152	-91.85	161.3496	203.7916
Earth pressure	128.3	128.3	-323.33	207.35	0
Live load surcharge	0	0	0	0	0
Weight of Substructure	194.38	194.38	0	495.945	0
Weight of the footing	133.35	133.35	0	420.0525	0
Weight of soil above tie	1086	1086	-1033	3604	0
Total	1755.638	1741.178	-1448.18	5218.6459	203.7916

	Eccentricity								0.85	m
	Longitudinal Movement								658.57	tm

				P max	P min	ML	MT
	Load Combination 1			1755.638	1741.178	658.57	203.7916

	Combine for base pressure

	p1= ( P / A ) + [(ML) / ZL ] + [(MT) / ZT ]
				32.86698
	p1= ( P / A ) + [(ML) / ZL ] - [(MT) / ZT ]
				30.17132
	p1= ( P / A ) - [(ML) / ZL ] - [(MT) / ZT ]
				13.57847
	p1= ( P / A ) - [(ML) / ZL ] + [(MT) / ZT ]
				16.27413

Combination of base presssure and design of founation
					For p max
	P max	P min	ML	MT	p1	p2	p3	p4
ULS condition	2430.99	2418.99	1507.9	209.85	52.54	49.76	11.77	14..55
Service condition	1755.638	1741.178	658.57	203.7916	32.86698	30.17132	13.57847	16.27413

					For p min
					p1	p2	p3	p4
					52.54	49.76	11.77	14..55
					32.67571	29.98005	13.38720	16.08286

Factored Loads for design
Loads	Factors	PMAX	PMIN	ML	ML DUE TO P	MT	Factored PMAX	Factored PMIN	Factored ML	Factored ML DUE TO P	Factored MT
Dead Load	1.35	99.5	99.5	0	228.85	0	134.325	134.325	0	308.9475	0
SIDL	1.35	29.7	29.7	0	68.31	0	40.095	40.095	0	92.2185	0
SIDL (Wearing coat)	1.75	14.256	14.256	0	32.7888	0	24.948	24.948	0	57.3804	0
Live Load	1.5	70.152	36.38	-91.68	203.7916	203.7916	105.228	54.57	-137.52	305.6874	305.6874
Earth pressure	1.5	128.3	128.3	323.33	207.35	0	192.45	192.45	484.995	311.025	0
Live Load Surcharge	1.2	0	0	0	0	0	0	0	0	0	0
Weight of Substructure	1.35	194.38	194.38	0	456.019225	0	262.413	262.413	0	615.6259538	0
Weight of Footing	1.35	133.35	133.35	0	420.0525	0	180.0225	180.0225	0	567.070875	0
Weight of soil aboe the footing	1.35	1086	1086	1033	3604.1	0	1466.1	1466.1	1394.55	4865.535	0
						Total	2405.5815	2354.9235	1742.025	7123.490629	305.6874

ECC		0.85	m
ML		1480.7213	tm


PMAX	PMIN	ML	MT
2405.5815	2354.9235	1480.7213	305.6874

Design of Footing

ULTIMATE LIMIT STATE
Grade of Concrete	fck	M35
Design strength of concrete	fcd	15.63
Grade of steel	fy	Fe500
Desight Strenght of steel	fyd	434.8
Modulus of elasticity of steel	Es	200000	Mpa
Modulus of elasticity of concrete	Ecm for M	32000	Mpa
Cu=		0.416xu
xu,lim/d		0.617
Rlim=Mu,lim/bd2	0.809fcd(xu/d)(1-0.416*xu/d)

Calculation of Reinforcement Design of Heel Slab
Calculation of Reinforcement Design of Heel Slab
Overall depth of section	1000	mm

BM due to soil pressure	127.282	tm
BM due to Self weight	-47.82	tm
BM due to weight of soil above	-103	tm
Net BM =	-33.53	tm
Design moment per m width	-33.53	tm		36.54
Effective depth required	`sqrt (Mu)/(R*b)`

Effective depth required =	310.342	mm
Eff. Depth available, d =	912.5	mm	OK
Area of steel required	1328.6	mm2
Dia of main reinforcement =	25	mm

	Provide	25	dia bars	at	200	mmc/c
Area of steel provide		4908.7	mm2	OK


Check for minimum and maximum Reinforcement as per IRC 112

2. Detail the steel in shallow foundation for abutment.

Bar details:-

Top bar

1a no.:- main curtail bar

1 no. :- main bar full lenght

Buttom bar

3a no. :- main bar

3 no. :- main full lenght bar

Distribution bar

2 no.

3. How a shallow foundation different in flyover and in river bridge?

Shallow foundation is used when we have good bearing strata available below the soil. If not, then we will go for deep foundation.

For the flyover bridge shallow foundatin is prefered because foundation is not coming in contact with water. Due to this, effects due to scouring and liquifaction need not be considered. As per IRC we have to provide foundation depth 2 meter below the soil.

The river bridge is coming directly contact with water so we have to first calculate the scouring effect, and then, by using that data, we have to decide the depth of the foundation. Shallow foundation shall be provided if we have good bearing strata available below the foundation. If not, we will go for deep foundation.

Weight of wearing coat

SIDL 2 reaction on one side