[Boris]

If any Geeks or Architect types can help me out I would be obliged.

Need to calculate the effect on a reinforced circular beam set in the vertical plane.
Beam dia = 0.8m standard industry steel bar reinforcement matrix
Length = 7.5m
Force applied in the mid point in horizontal plane.
Speed of force 2 mph
Distance traveled 2 metres
Mass of object 500 tonnes

a) on impact would the beam suffer a devastating failure ?
b) how many impacts would need to occur before an failure could be expected?

c) as a) but distance of object to impact 5 metres

d) as c) but speed 5mph

My KE and Moments learning are many years in the past !!

[Sigga]

Ask a structural engineer, maybe... It sounds important enough.

Are you planning to drive your apartment building into a length of steel?

If so, can I watch?

[Boris]

I am waiting one to call me. However its just to quantify a feeling about a structure in a project I am interested in.

My experience says its not right and just need someone to do a rough calculation. Its basic( ish ) maths stuff but I didn't want to cock it up.

[hk.com]

The thing we don't know here is the tensile strength of the beam. Beams and beams vary. The density of the steel bars can vary and so grade of cement.

At 2Mph the impact will be around 1600 Tonnes.

The flat surface area of that mean assuming it is square is in the region of 6sqm. That means a loading at impact (assuming it is evenly) distributed of about 266 tonnes per sq meter.

We also have to forget the elasticity or lack of the beam and compare it against something we know. In HK the floor loading ratings for industrial buildings are about 700Kg/sqm. So you are asking a beam to take 380 times weight of an industrial floor per sqm.

Overall fat chance of the beam surviving at 2mph. I think you will need around 4 to 8 times the beams to be able to survive that impact.

[Boris]

As pointed out the beam has a diameter , therefore its circular NOT square.

An architect / structural geek would assume a standard made reinforcement formula for this item. As you an IT geek its not something you would know. FYI the info I see on the net is not understandable to me.

If anyone can find the standard equation relating to a reinforced concrete cylinder I may be able to do the rest.

What was your formula for the impact effective force?

FYI _ floor loading is subject to a factor of safety, maybe around 20 times. Otherwise I suspect you would have buildings crashing down all around the place

[hk.com]

Actually I made a mistake the impact is 444 Tonnes at 2mph. The formula is the standard formula for calculating momentum.

Yes I understand the beam is round. I turned things into a more favorable manner to see if the numbers even add up then. The beam being round it would receive the impact in a much smaller surface area, and would have worse odds to distribute the impact throughout the structure. Even at 6sqm, I was being very very generous.

[Boris]

The impact should not be measured in tonnes and I don't understand why you have used momentum as your base.

A mass KG traveling at a speed M/S exerts a force ( Kinetic Energy ) . Momentum would be the distance traveled from rest or a point in space after exertion of that force.

If a 500 tonne load hits at 2mph ( 3.2187kph ) the result is going to be measured in Joules or Newton Metres ( kg.m2/s2 )
I have this at 200,000 @ the slower speed and 1,250,000 @ the higher speed.

The important thing for me ( working without the info of the beam strength and elasticity ) is to find its initial bending moment and shear force calculation.

A question I have is
When making the load calculation . This is in KNS ( Kilo Newton Second ) so need reminding if the speed factor has to be used again when coming from KN, which already contains the speed element.

Also should the Shear stress be calculated at point of impact or at the support position of the beam. IE 2 points of shear stress (x ) Therefore each measure to be x/2

As you can see my mechanics calc is rusty.