Extending balcony and a bridge

[BotusBuild]

Looking for some input/kind critique (he asks hopefully 🙂 ) Am I missing anything apart from the steel sizing for the bridge framework and finish? Is the bridge over-engineered?

 

We need to add a series of "struts" to extend the outer edge of the balcony to where it should be. The current I-beam is in three parts. The two joins in the middle connect to "perpendicular" I-beams. Each perpendicular I-beam (203 x 133 x ??) is supported on a square section post at the midpoint, and columns at the inner side of the balcony. The plan below shows this:

Each blue line above is a proposed new "strut".

 

Below is my proposed strut design to be provided to steel fabricators for quoting against. I'll have it red oxide painted (or will do it myself when it arrives)

 

At the left hand end of the balcony there is an opening through a poured concrete wall. From this we propose to install a "bridge" that will connect the end of the balcony back to a level area of parking created using concrete lego bricks for a retaining wall. Below is the proposed framework for that bridge (the opening is somewhat taller than shown in the Side View). We will then "deck" the framework once installed.

 

Bridge from balcony.pdf

[markc]

Hi, can we assume the beam should have been at the balcony edge and it’s the supporting beams that are short?

my concern would be torsional stiffness of the beam when you add the cantilevers and then a loaded deck (self weight, plus dead loads of balustrade etc. plus live loads of persons using the balcony and especially leaning on the balustrade). 

[JohnMo]

Isn't this why structural engineers exist? Plus with drops you should have a structural design certificate anyway.

 

Other than that no comment 

[BotusBuild]

1 hour ago, markc said:

can we assume the beam should have been at the balcony edge and it’s the supporting beams that are short?

Yes, that's a safe assumption.

1 hour ago, markc said:

my concern would be torsional stiffness of the beam

Agreed. I will be adding a wooden edge on the end of the cantilever, then 2x3 or 2x4 right across the whole width at 400mm c/c, before the final balcony coverage on top of those. The 2x3 or 2x4's should reduce the torsional impact.

[JohnMo]

47 minutes ago, BotusBuild said:

The 2x3 or 2x4's

All sounds dinky. My balcony structural engineer designed, was a combination of 10x2 and 6x2

[BotusBuild]

2 hours ago, JohnMo said:

10x2

Already have 8x2 installed every 400 c/c. The 2x3 or 2x4 will be screwed along each of these, probably every 400mm

[Mr Punter]

That will be quite a few holes in the web of the existing beam.

 

Have you worked out how you are going to fix the decking?

[markc]

The more I think about this the more I would go for taking the beam down and putting the extensions on the support beams even if that meant welding. Or I would be adding a 150 or 200mm channel at the ends to reduce the torsion loads at centre span