Vibration Cracking

[stairmaster]

We were called to a job to investigate cracking in a brick building which was said to be caused by the vibrations from driving in sheet piling for a gas line. The distance from the sheet to the corner of the single story building is 108' the front face of the building is 46' long and goes back 80' and there were no expansion joints. What I found odd was that there were only cracks on the front of the building and no where else. Is this typical in buildings which have seen cracking caused by vibration?

 

[msquared48]

Well, without a wall plan, I would have to assume more openings on the front wall than the rear, and no side openings. This means a weaker front wall, that would intuitively be more susceptible to cracking.

Mike McCann, PE, SE (WA)

 

[JAE]

Cracking could be from a lot of "other" things that the vibration. In fact, vibration typically has not been a cause for cracking in many buildings I've investigated with piling or excavation done nearby.

A lot of times the cracking was from previous foundation settlements, south-facing walls with larger thermal effects, etc.

If you look at the crack you can sometimes find soft, worn edges or paint/sealant inside the crack that suggests an older crack.

Per Mike above, without more info we are just suggesting issues to consider.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[oldestguy]

I'd think that it will be necessary to really prove this the owner would have to invest in a study whereby there are vibration monitoring equipment set up on the building and between it and a source of vibration, using the same type of hammers and sheets. Unless the owner's expert has done these sort of tests in the past and his experience can prove the sheet driving caused it, an expert on the other side would not have much trouble winning the case for the contractor.

Other factors, such as control joints (or lack), sun exposure, age or work, etc. proof of condition before and after enter.

 

[Brad805]

This is where owners or contractors need before and after pictures. Many times these are a case of an owner wanting someone else's insurance to do some renovations. We have been involved in a few of these and it is hard to prove unless you have a lot of specifics or earlier pictures.

 

[asixth]

We call them dilapidation reports. Contractors engage an engineer or other suitably qualified building professional to report on the defects of the neighbouring properties prior to construction in case a neighbour tries to claim damages.

Same happens with insurance claims after a damaging weather event. Even if the property isn't damaged some people will try to claim "other damages" on insurance.

 

[Ron]

Agree with above. Wall more susceptible to cracking. Look closely at cracks to determine approximate age. As JAE noted, older cracks have different appearance.

As for the vibration, a lot depends on the soil conditions and water table location. While there will be both airborne vibration and direct transmission, the direct transmission is the one more likely to cause damage. A lot of vibration energy can be dissipated in 100 feet and there's a reasonably large difference between perceptibility and structural damage when considering vibration. As OG noted, there should be testing to determine the actual vibration levels as this is site-specific.

The group doing the work that causes the vibration has an obligation to protect adjacent structures. In some states, it is a law. In others, though not a law, it's a prudent thing to do because of potential liability. The approach I recommend when dealing with adjacent structures is to do a detailed pre-construction survey (with video) of buildings that would potentially be affected by the vibration, then set vibration monitoring devices up at various locations with alarm triggers if the vibration levels reach certain set points. All cracks on existing buildings should be mapped, measured and marked to see if they grow during the vibration events.

 

[BUGGAR]

It's probably too late now but there are portable seismic measuring tools (Sprengnether or something like that) that you can use to monitor buildings while driving piles. We had to use them in New York when a lady claimed our blasting operations threw her off her toilet.

 

[oldestguy]

Couldn't help it, but wife agreed. It wasn't the blasting.