As 1170.1 C3 floor loading - trolleys

[Settingsun]

Can someone help me with the reasoning for the occupancy C3 loads for trolleys vs no trolleys? According to the commentary, this refers to trolleys up to 3 kN weight. But the difference is 5 kPa vs 4 kPa, with 4.5 kN concentrated for both cases.

Why does a trolley that totals 0.75 m2 of 4 kPa loading require bumping the UDL? I can understand a slightly higher concentrated load but not designing for literally tonnes of additional load over an area.

Extra question: Are shopping centre car parks required to be designed for 5 kPa instead of the 2.5 kPa for occupancy F? Seems far fetched that a cleaner's trolley is twice the load of modern cars.

 

[human909]

Cars aren't that heavy and are quite a predictable maximum load. It is hard to get over 2.5kPA even if you pack the cars end to end and side by side. But if you have a look at a parking garage even when EVERY spot is taken in actualy ground area only about 50% is cars the rest is gaps between cars and thoroughfares.

People however can be quite heavy when they are packed together. Generally they people don't pack together like sardines often but when they do it can be quite a load. And the consequences of failure also coincides with the highest risk of failure. So you need to cater for high UDLs. There are plenty severe engineering accidents from under designed spaces holding large numbers of people.

Regarding the 4kPa vs 5kPa. Well I don't have the commentary in front of me so I can't comment. But I would presume they aren't talking about a 'cleaners' trolley. We are more talking about crowds of people here and the extra 1kPa is if wheeled vehicles for carrying items is in play.

 

[Settingsun]

"The term ‘wheeled vehicles’ refers to trolleys, cleaner’s carts, and other small vehicles up to 300 kg gross mass, but not to cars or trucks (see activities F and G)."

I just don't see how that can require a higher UDL. You'd need a lot of them packed in tight to the point you'd have to say it's a storage area. These wheeled vehicles are the only difference so must be the reason for increased design load.

Re car parks: I was just drawing the comparison between them and other floor loads, as car parks seems to be the only thing that isn't overspecified. I realise cars aren't that heavy but you can get crowds in car parks, eg one near me that has a view of fireworks gets packed once a year (doubt it crossed the designer'smind), or (I imagine) if a shopping mall were evacuated. And they certainly get trolleys and carts through them (a van could even have a monster trolley inside it so double load!) but only need half the design load. I'm currently of the opinion that 5 kPa was plucked from thin air but am curious.

I also wouldn't rely on empty roadways in car parks. They often get traffic jams banking up from the exit over several levels.

 

[human909]

I agree. The reason for increasing the load from 4kPa to 5kPa isn't obvious to me. But there is no doubt an obscure and barely relevant reason behind it. The same could be said about a bunch of the categories in that the floor loading list. EG how often is a theatre fly gallery or a drill hall built?

Some numbers do almost seem like they are picked out of thin air. But it is difficult writing code to capture everything precisely, and just one obscure example could end up driving the decision to pick X-value for a drill hall or for loaded trolleys and then it gets struck in the code for decades.

I also wouldn't rely on empty roadways in car parks. They often get traffic jams banking up from the exit over several levels.

True and that was something that did occur to me. But that still keeps the number well under 2.5kPa. Like I said if ever care water literally touching bumper to bumper and side to side you'd still be under 2.5kPa. In a traffic jam situation you might increase the floor area coverage from 50% to 70%. You'll still have plenty of free space.

If this is a car park where people congregate then the high value should take priority. Both engineering judgement and the code explicitly allows for this.

 

[Settingsun]

Best I've been able to dream up is the trolley causes the 4kPa crowd to crush together a bit closer to make a path for the trolley, giving 5kPa.

I did also start to wonder what the no-wheeled-vehicle area applies to in the disabled access age. You can get trolleys/carts anywhere these days and should always consider mobility scooters.

 

[rowingengineer]

This is a historical question, the 5kpa existed before the 300kg definition was added to the code.

As1170 80s addition would be a good place to review. Loading from live haven't been greatly reviewed since the 60s it has mostly been service reviews.

 

[Settingsun]

I can only go back to 1989. The numbers are the same but it's worded as loads other than crowds including wheeled vehicles.

I picked the parking/garage use category for the image because I was banging on about it earlier but the same load requirements are repeated in several other categories.

 

[blihpandgeorge]

whenever i have gone down the path to look at live loads i have found most are historic.

The 1981 AS1170.1 has more detail and alludes this to apply to hall ways/corridors (ie narrower spaces?) see attached extract

ps - how do you place a screenshot into a post?

 

[Settingsun]

Thanks, Blihpandgeorge. The attachment didn't arrive. There's a camera icon in the editing bar to insert images directly. See above the preview button (this is how it looks in phone, could be different on larger screen).

 

[blihpandgeorge]

Try Again!