Shallow foundation &stair case Pacific school Of engineering (BE 3rd sem) Subject: Building Construction (2130607) Gujarat Technical University Group Member : 131120106015 Godhani Nikunj A. 131120106007 Chovatiya Harsh Y. 131120106047 Shekhada Ketan K. 131120106022 Katariya Sanjay 131120106025 Khunt Bhavesh 141123106002 Patel Deep Guided by : VEKARIYA MAYUR S. Assistant Professor (Civil department )

Contents Introduction offoundation stair & stair case Types of foundation Types of shallow foundation Foundation in black cotton soil stair & stair case Definition and parts of Stair cases Types of stair cases Requirements Detailing principles Problems Art of Drawing Bar bending schedule Reference

TYPES OF FOUNDATION Foundation : It is the lowest part of a structure below the ground level which is in direct contact with the ground and transmits all the loads to the ground. Types of foundation : Shallow foundation (D≤B) deep foundation(D>B)

TYPES OF FOUNDATION Shallow foundations Deep foundations If depth of footing (D) is less than or equal to width of footing (B) , it is called shallow foundation. Deep foundations If depth of footing is more than the width of footing, it is called deep foundation.

TYPES OF SHALLOW FOUNDATION Spread footing 2) Combined footing 3) Strap footing 4) Raft footing 5)Grillage footing

1) Spread footing : In case of spread footing the base of footing is made wider so as to distribute the load over. There are four types :- A.wall footings B.reinforced concrete footing C. inverted arch footing D.column footing

A. Wall footing A spread footing for a continuous wall is called wall footing or strip footing. There are two type of wall footings :- a).Simple wall footing without mesonry offsets b). wall footing with masonry offsets.

a) Simple wall footing When the wall carries light loads or when the safe bearing capacity of soil is very high, is called as simple wall footing. Its shown as fig. (a) b) Wall footing with masonary offset when the wall carries heavy loads or when the safe bearring capacity of the soil is less the base width required will be more than ( 2t+2p) is called as wall footing with masonary offset. Its shown as fig.(b)

Rainforced concrete footing : In place where the walls are subjected to heavy loads and the bearring capacity of soil is the low . A 7 to 8 cm thick bed of lean concrete is usually provided below the rain forced concrete footing

C) Inverted arch footing : One of the drawblacks in this type of construction is that the and columns must be strong enough to resist the outward pressure caused by the arch action.

D) Column footing : They are used to support individual columns. Generally , 15 cm offset is provided on all sides of concrete bed.

2) Combined footing : A combined footing supports two columns. It may be rectangular or trapezoidal in shape. When the two columns are so close to each other that their individual footing would overlap. When the property line is so close to one column that a spread footing would eccentrically loaded when kept entirely within the property line.

Combined &strap footing

3) Strap footing : A strap footing consists of two isolated footing connected with a structual strap or a lever as shown fig. The strap is designed as rigid beam. A strap footing is mmore economical than a combined footing when the allowable soil pressure is relatively high and the distance between the columns is large.

4) Raft footing : A raft or mat foundation is a large slab supporting a number of columns and walls under the entire structure or a large part of the structure. When the allowable soil presuure is low. When the structure loads are heavy.

Foundations in Black Cotton Soil : Black cotton soil is dangerous for the building on account of its volumetric changes with the change of atmospheric conditions. The variation in thevolume of the soil is to the extent of 20 to 30 percent of the original volume. This tendancy of soil is on account of the presence of fine clay particles which swell when they come in contact with water. precautions for the safety of foundation in black cotton soil : 1) The raft and pile foundation should be adopted 2) The construction work should be carried out in dry season.

Types of foundation in black cotton soil : Strip or pad foundation Pier foundation Under reamed pile foundation Strip foundation : For medium loads , strip foundation and pad foundation may be provided , along with special design features as discussed below. Method-1:- This method is suitable when the soil, though expansive , has little sweeling pressure. Method-2:- Its used for soils of high swelling pressure and having high shrinkage properties .

2) Pier foundation : Pier are dug at regular interval and filled with cement concrete. The pier may reston good bearing strata. This gap would permit free vertical movement soil during swelling and shrinkage operation.

3) Under- Reamed Pile Foundation : An under reamed pile is a board casting situ concrete pile having one or more bulbs rounder reams in its lower portion. The Under reamed pile Diameter 20 to 50 cm and length 3 to 8 meter. Than spacing of piles is 2 to 4 meter. A single under reamed pile has only one bulb at the bottom. When two or more bulbs are provided at the base ,it is known as multi bulb under reamed pile. The vertical spacing between two varies from 1.25 to 1.50 times the diameter of bulb..

Precast Concrete Piles

Shallow Foundations Requirements Suitable soil bearing capacity Undisturbed soil or engineered fill Basic types or configurations Column footings Wall or strip footings

STAIR CASE Definition Stair cases are used for the purpose of giving access to different floors of a structure.

Type of steps: Filer Bullnose step Round ended step Splayed step Commode step Dancing step Winder

Types of stair cases Based on shape Quarter turn stair Straight stairs Dog legged stairs Open well or open newel stairs Geometrical stairs such as spiral, circular, etc. Bifurcated Stair Three Quarter turn Stair

Dog legged SC Straight SC Geometric SC

Straight Stair :

Bifurcated Stair :

Dog legged Stair :

Geometric stair :

Spiral stair:

Three Quarter turn stair :

CLASSIFICATION Based on type of span Horizontally spanning or transversely spanning SC Longitudinally spanning SC.

Guide lines for fixing the dimensions Rise (R) : 150mm to 180mm Tread (T) : 220 mm to 250 mm- for residential buildings. Rise (R) : 120 to 150 mm Tread (T) : 250 mm to 300 mm – for public buildings [T + 2R] : Between 500 mm to 650 mm The width of the stair 0.8 m to 1 m for residential building and 1.8 m to 2 m for public building.

Guide lines for fixing the dimensions Contd… The width of the landing is equal to the width of stairs. The number of steps in each flight should not be greater than 12 The pitch of the stair should not be more than 38 degrees. The head room measured vertically above any step or below the mid landing shall not be less than 2.1 m.

Design of stairs Design for maximum bending moment and check for maximum shear force. The depth is to be fixed from deflection criteria. Stair case slab is designed as a conventional slab. All rules regarding the detailing are similar to that of slab. Enough development and anchorage lengths for steel should be provided.

EFFECTIVE SPAN FOR LONGITUDINALLY SPANNING STAIRCASES Le LANDING WAIST SLAB WALL EFFECTIVE SPAN FOR LONGITUDINALLY SPANNING STAIRCASES WAIST SLAB SUPPORTED AT THE ENDS OF LANDINGS Case (a)

EFFECTIVE SPAN FOR LONGITUDINALLY SPANNING STAIRCASES GOING=G Le X Y EFFECTIVE SPAN FOR LONGITUDINALLY SPANNING STAIRCASES Le Case (b) Le=G +[ X +Y], X ≤1m AND Y ≤1m Le Case (c) Le=c/c of beams

Longitudinally spanning SC Detailing Steel at bottom longitudinally-tension Anchorage and development steel Distribution steel Row of chairs Nominal foundation for ground flight

Exercise A dog legged stair case is to be detailed with the following particulars: Clear dimension of stair case room=4.48 m x 2.1 m The floor to floor height is 3.2 m Width of each tread =250 mm Width of each rise = 160 mm Thickness of waist slab = 150 mm Width of flight =1m All round wall = 230 mm

Exercise contd., Both flights are supported at the ends of landing on 230 mm wall. (Landing and flight spans in the same direction) The first flight starts from the plinth level Main steel for each flight = #12@120 Distribution steel for each flight = #8@ 200 Use M20 concrete and Fe 415 steel. Draw to a suitable scale The plan of stair case Sectional elevation of the Ground flight Sectional elevation of the First flight Bar bending schedule

Solution Dimensioning: R=160 mm, T= 250 mm Floor to floor height = 3200mm No of rises = 3200/R = 20. Each flight has 10 rises. No of treads per flight=10-1 =9 Width of landing along flight = (4480-9x250)/2 = 1115mm. Going of flight=9x250 =2250mm Development length = 47φ= 47 x 12 = 564 mm

Exercise Plan of stair case 2100 PLAN 1115 mm 2250 mm Le = 4710 mm Gap=0.1m 2100 Clear dimension of stair case room=4.48 m x 2.1 m

Estimation of quantity of concrete Volume of concrete = L x B x D L= length along the central line in m-measured B=Breadth in m D=Thickness of slab in m Plus concrete in footing Weight of concrete, kg = Volume x density

Conclusion Types of staircases. Effective span concept. Requirements of staircase. Detailing of steel. Importance of development length and anchorages. Drawing to scale and bar bending schedule.

Reference :- www.whereisdoc.com www.authorstream.com Dr. R.P.Rethaliya, “ Building construction, “ Atul prakashan

The end Thank you very much