1st Q Of Dos Assignment

QUESTION: Design a RCC retaining wall to retain earth up to a height of 15’. Base of the footing is to be placed 3’ below NSL. Soil has density of . Angle of internal friction of soil is

. Earth surface that is to be retained is

horizontal. Take Use

.

SOLUTION: Given that,

STEP 1 ASSUMPTION OF SIZES:

STEP 2 DESIGN OF STEM: i. Calculation Of Soil Pressure:

ii. Moment & Reinforcement Calculation:

iii.Selection of bars & spacing: Vertical Reinforcement On front face of wall:

Temperature & Shrinkage Steel:

iv. Check for shear:

v. Capacity of Section:

STEP 3 CURTAILMENT OF BARS: Bars are curtailed from top where B.M is

According to ACI code, the following value should be added in the curtailed value of steel, • •

• •

Maximum of above three values is selected, i.e. 12” is selected. So, Curtailment from top.

,

PLAN & SECTION

According to ACI code provide main steel on the side where there is no loading & provide same temperature and shrinkage steel on load bearing side.

Step 4

STABILITY CHECKS: There are three stability checks,

i.

Check For Overturning Moment

Sr. # 01 02 03 04

If this check is not OK then increase the thickness of toe, heel or stem as per requirement.

1 produces overturning moment & 2, 3 and 4 produces resisting moments.

ii. Check For Sliding Force:

Here is the coefficient of friction between soil and earth and its value lies between 0.3-0.45.

So we have to provide key under the base.

Key can be provided in different states as shown below,

Design of Key:

iii. Check For Bearing Capacity Of Soil:

If this check is not OK then increase the length of base “B”

If this check is not OK then increase “B”.

STEP 5 DESIGN OF TOE & HEEL:

i. Design Of Toe:

Taking moment about junction of toe and stem.

Selection of bars & spacing:

ii. Design of heel: Taking moment about junction of heel and stem,

Neglecting moment produced due to stresses. It will make our structure safer because it works as a FOS.

Selection of bars & spacing:

Temperature & Shrinkage Steel:

DETAILS OF STEEL IN TOE & HEEL