Existing Building Questions

[Den32]

Working with an existing building and need some input.

1. Exterior Clay Masonry Bearing Walls built circa 1850's - 3 wythes (13" total thickness), 2 stories tall. Some areas of water deterioration & mortar loss that will require remediation, but otherwise brick and mortar in good shape.
- What is reasonable Compressive Strength / Mortar Type to assume for this without testing?

2. Steel beams circa 1939 - per AISC Historical Charts, likely ASTM A9-34 steel.
- Anyone know weldability of this steel? I did a search on aisc.org and didn't found anything. Likely add cover plates, so 3/16" fillet welds (light welding)

3. Wood joists bearing on steel beam top flange.
- Is it reasonable to assume the wood joists 'brace' the beam top flange even though there is no direct connection (just by assuming 'skin friction' between joist/steel)?

Thanks.

 

[dik]

It's not likely possible to 'guess' a mortar strength due to the huge variation. Some mortars, lacking hydraulic characteristics, can essentially be sand. At the time the original wall was constructed, the mason likley sourced his own lime products. You have to be careful about repairs; the new work should 'mimic' the old wall for strength and porosity. Do not use Portland cement mortar.

Also the three wythe wall would use the porosity of the brick and mortar to remove moisture from within the building. This should be maintained or the entire building envelope be reviewed. There have been significant changes in lifestyles since the building was constructed... air tight construction and a greater time indoors, both, contributing to a much greater moisture content within the building.

Check Sliderule's website for a paper on Historic Masonroy/Brick...

Dik

 

[countervail]

3--

No timber joist are not really heavy enough to assume that they provide lateral restraint by bearing (as say a pre-cast plank floor would).

You can use a timber plate along the top of the beam and then bolt it to the beam and the joists.

or

Use metal angles bolted / tek screwed to the beam and to the joists.

or

Depending on beam depth, set the joists in between the flanges and pack tight with timber blocking.

 

[Ron]

If built in the 1850's, the mortar is not a portland cement mortar, but more likely a lime putty mortar. This material has much lower strength than portland cement mortar and if exposed to repetitive wetting/drying is likely friable, with only light cementation.

Strength of this material varies from about 300 psi to 600 or 700 psi....not strong by typical mortar standards of today.

Your steel is a mild steel and likely weldable, but extract a coupon and get it tested.

The wood will not brace the flange as you described.