out of interest...

[empip]

Upshot .. good fastening involves the use of washers...

Not always - read about the West Gate bridge disaster

The introduction of the Report of the Royal Commission begins:

"On The 15th October, 1970 , at 11.50 am , the 367-ft span of the West Gate Bridge , known as span 10-11, being one of the spans on the western side of the River Yarra, suddenly collapsed. There can be no doubt that the particular action which precipitated the collapse of span 10-11 was the removal of a number of bolts from a transverse splice in the upper flange plating near to mid-span. The bolts were removed in an attempt to straighten out a buckle which had occurred in one of the eight panels which constitute the upper flange. The buckle in turn, had been caused by the application of kentledge in an attempt to overcome difficulties caused by errors in camber....

Some say multi tonne blocks of pig-iron (kentledge) some say concrete.

.......On the fateful day, Thursday 15th October 1970, Jack Hindshaw, the bridge building expert, instructed Barney Butters, a Boilermaker, and his Trades Assistant, Des Gibbson, to remove a number of bolts in an attempt to eliminate the bulge. This action was without any consultation with the Unions, the safety committee or the workforce. If we had known we would never have agreed to this procedure.
Instead of loosening these high tensile bolts and then removing them in the normal manner, powerful impact wrenches were used to tighten the bolts till they snapped. This was another short cut we didn't know about and certainly not a "Belt and Braces" procedure....

When these bolts had been removed Jack Hindshaw realised something was wrong as the steel was turning blue, the rust was spitting off and there was a groaning noise. He phoned World Services office on the ground and explained the situation. They directed him to immediately replace the bolts. But the bolts had all been broken in their removal, none were available.
At this stage there was plenty of time to clear the bridge, it could have been evacuated as a priority. But sadly it was not done.

Cannot find anything concerning washers?? I bet there was some damage limitation shennanegins going on.

I was expecting to read of mild steel washers used with high tensile bolts or something 'iffy' like that.

It's alright Toffee your structure should be sound... but then again..

 

[ban-all-sheds]

TBH I didn't read the report, I was going by what I'd been told by a structural engineer about what happened, which was basically:

1) The two halves of the bridge were not in vertical alignment when they met in the middle

2) A lot of weight was placed on the high end to get it to move down

3) This caused buckling further back

4) Bolts were removed to allow parts to shift

5) The holes were no longer in alignment, and so were enlarged

6) The bolts were now too small, so washers were used

7) Thus only the friction between the washers and the steelwork was stopping the plates/girders from moving. This was inadequate.

 

[ban-all-sheds]

Im off camping for the weekend so keeping fingers for good weather.

And if the weather is not good, what will you use instead of fingers?