Reinforced Concrete Design help

[Kieran]

Hello all,

Having trouble answering this question as part of a course on Mechanics of Solids, just wondering if anyone can point me in the right direction to start?

A 2.45m by 2.45m reinforced concrete footing support a 400mm by 400mm column. The service load of the column and footing can be taken as 1050kN. The design load on the column is 1450kN, the effective depth of the footing is 450mm. The allowable bearing capacity of the soil is 200kN/m^2. Concrete grade 25. Steel Grade 400Y

a) Check the area of the footing.

B) Determine the area of tension steel reinforcement for bending and choose a suitable diameter for the steel reinforcement.

c) Check the beam shear

d) Check the punching shear.

NOTE: I have the answers, but have no idea how to arrive at them!

Thanks for your time in advance.

Kieran

 

[MA_PE]

Here's my stab at it.

You have a .4m x .4m column coming down on a 2.45m x 2.45m pad. Assuming ity is centrally located (typical) that means there is 1.025m overhang of the footing on each side.

a.) check bearing using service loads 1050kN / 2.45^2 = 175kN / m^2 This is less than 200kN/m^2 therefore bearing is OK

b.) look at the overhang as a cantilever beam fixed at one end with a uniform load of 1450kN/2.45^2m = 242 kN/m^2 on it. Determine the design moment and then assuming a 450mm beam with 75mm concrete cover calculate the required flexural steel.

c.) check the same beam for shear

d.) get the shear load and perimeter at "d" from the face(s) of the column and check against the punching shear provisions of the code (I assume that the problem statement is referecing ACI.)

I hope this helps.

 

[Kieran]

Thanks for the reply, it is helping.

The problems I'm having are still for calculating b. c. and d., I understand a. now, but there is a severe lack of information about reinforced concrete for my class, and having the lecturer away from uni presently and the exam tomorrow I'm in a bit of a jam. What I need essentially is the equations used to calculate b, c and d. As then hopefully I can apply them to similar problems in the exam tomorrow. If you could supply those that'd be a huge help to a struggling student.

Regards,

Kieran