CONCRETE BRIDGE DESIGN STANDARDS 4

[Ramezsayed EIT]

Hey

please see two attached photos of a concrete bridge being built next to exiting residential building.

( I don't want to mention the country but the wind speed is around 80 mph)

since I am not expert in bridges design I need some answers to the following with some references please:

1-what is the max clearance from the bridge side to the building ?

2-the bridge foundation is isolated footing on piles and the footing of the existing building is raft foundation ( both of them on caly soil) will the weight of the bridge affect the foundation of existing buildings?

3-the spacing from the bridge to the building now is very small, do you think the bridge will have a side sway some how and it will lean on the building and affect its structural integrity?

4-i am assuming accidents may happen, will be any impact load can be applied on the existing

building ?

you can raise any other concerns if you want !

 

[mchen96]

Ok... I've never seen something like that. Talk about building on the edge...

The country matters a lot since it will state which code applies to your region. I'll post some general answers below; however, it's important to remember that some (or all) of these things may or may not apply in your region. Without calculations, its also difficult to say how significant some of these effects might be. Anyways, in order:

1-what is the max clearance from the bridge side to the building ?

The structural code for bridges (AASHTO) does not have a stated minimum clearance between structures. That being said, city codes (which vary by region) do tend to have clearances. Fire codes also tend to have a minimum clearances between structures.

2-the bridge foundation is isolated footing on piles and the footing of the existing building is raft foundation ( both of them on caly soil) will the weight of the bridge affect the foundation of existing buildings?

If the bridge is on end-bearing piles, there should be no impact at all. If the bridge is on friction piles, there could be a limited amount of settlement, although I don't think it would affect a raft foundation significantly (unless the soil is very poor).

3-the spacing from the bridge to the building now is very small, do you think the bridge will have a side sway some how and it will lean on the building and affect its structural integrity?

I'm more worried about the opposite. The building may be pushed towards the bridge by the wind, closing the gap. I wouldn't expect any significant sidesway of the bridge due to wind, since the buildings block the wind on both sides. Note that this assumes there are no seismic effects to consider in your area. If seismic is a concern, the gap between structures should be able to accommodate the expected seismic deflection (in other words, gap > [expected bridge deflection] + [expected building deflection]).

4-i am assuming accidents may happen, will be any impact load can be applied on the existing

Impact loading should get applied on the (rigid) bridge barrier, which should prevent vehicles from hitting the building. That being said, I would definitely want a TALL barrier. If a truck impacts the barrier, the top of the truck may tilt into the building, which would be, well, bad. See the following image, which shows how much a truck may tilt past the barrier (assuming a TL-4 barrier, image from the AASHTO Roadside Design Guide)

you can raise any other concerns if you want !

I'd double check the local fire code. Those windows and balconies probably don't have fire-rated windows. I'm not sure if this situation is specifically covered by the fire code (a street on the 5th floor with 0 clearance?), but it's definitely a concern.

Seismic may or may not be a big concern in your area. Bridges usually follow a strong beam-weak column design, which means that the bridge will sway a lot under an earthquake (and will most likely hit the building).

If you have truck traffic in the bridge, the barrier should be tall enough to prevent the truck from tilting into the building.

 

[JAE]

1-what is the max clearance from the bridge side to the building ?
[red]Unlimited maximum clearance. The minimum (smallest) clearance should account for bridge sidesway and building sidesway with either wind or seismic responses. There's no way for anyone here to determine that based on a simple photograph.[/red]

2-the bridge foundation is isolated footing on piles and the footing of the existing building is raft foundation ( both of them on caly soil) will the weight of the bridge affect the foundation of existing buildings?
[red]If the piling go deep enough and don't draw down the adjacent soils via skin friction - for example if they are end bearing piling - then the bridge may not have much affect on the shallower mat foundations of the buildings. But without all the information about piling type, depth, soil characteristics, etc. there's no way to accurately answer this.[/red]

3-the spacing from the bridge to the building now is very small, do you think the bridge will have a side sway some how and it will lean on the building and affect its structural integrity?
[red]It might[/red]

4-i am assuming accidents may happen, will be any impact load can be applied on the existing
[red]If a car or truck comes flying off the roadway I'd be worried about the residences behind those windows watching television!!![/red]

 

[STrctPono]

Wow! I'm in awe of that photo.

I know others have answered but I am just providing my opinions/experience on the matter.

1-what is the max clearance from the bridge side to the building ? There are no set minimum clearance requirements that are set forth by Bridge Design codes that I use. The most prudent thing to do would be to run a response spectrum analysis on the two different structures and check their lateral displacement. Assume there is a chance that they will both be at their max displacement while out of phase from one another and use that clearance as a bare minimum, but geeze, I would think that is a theoretical number and that you would still want some extra buffer beyond that. That sucks for the people that have to live in those buildings.

2-the bridge foundation is isolated footing on piles and the footing of the existing building is raft foundation ( both of them on caly soil) will the weight of the bridge affect the foundation of existing buildings? As mchen96 noted, the bridge should have little to no effect on the building but the building has a real probability of having an effect on the bridge. Even if they are end bearing piles, the raft foundation could impose a lateral force onto the piles during a seismic event.

3-the spacing from the bridge to the building now is very small, do you think the bridge will have a side sway some how and it will lean on the building and affect its structural integrity? I think that if pounding is a possibility due to an undersized separation between the structures then yes, you could potentially have one or both of the structures damaged.

4-i am assuming accidents may happen, will be any impact load can be applied on the existing Standard impact railing in the US is anywhere between 18" to 56" depending on design use, Average daily traffic, and vehicle design speed. The railing would deflect and the truck itself wraps over the top of the barrier in an impact so if it is really close then yes, it could be a hazard. I would hope they designed a very tall barrier with a sound barrier on top of that.

 

[IDS]

I am reminded of an incident on an elevated motorway structure in Saudi Arabia in the early 1980's:

1. A few weeks after the structure was opened to traffic a truck impacted the bridge barrier, started to overturn, and went through the steel railings on top of the concrete barrier.
2. The overturning was slow enough to allow the driver to jump out of the cab onto the concrete.
3. The truck fell to the road below, where it landed on its roof in the middle of a busy traffic light controlled intersection.
4. All the lights were red.
5. No-one was driving through red lights and no-one was hurt.

Now this incident was so unlikely that it will probably never happen again, but it is only stages 2-5 that were unlikely.

Figure 5-31 posted by mchen96 looks like the best bet for an explicit code requirement that elevated roadways should not be built that close to residential building structures.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[r13]

I would hope they designed a very tall barrier with a sound barrier on top of that.

Watched a video on YouTube recently, a passenger car flew into building from adjacent express way. The surprising thing is the driver has only suffered slight wounds. Noise can drive the residents to nuts though.

 

[Retrograde]

In my part of the world there are mandated requirements for setback of buildings from property boundaries for fire safety (or fireproof construction).

I feel sorry for the people living in those buildings who just had their balconies enclosed and windows blocked. Not to mention the noise.

Let's hope this doesn't happen.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1589266940/tips/111_b2diko.webp[/url]

 

[Lomarandil]

The official stance is that those buildings are illegal construction within the designated right-of-way. So the building owner's fault, not the bridge.

Thankfully in a low seismic zone. Still too close for that, for the vehicular collision reasons mentioned.

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just call me Lo.