Vibration monitoring in old residential buildings subject to traffic v 2

[Etonbridge]

Traffic calming speed humps are being installed in an ancient High Street, with resulting potential vibration damage to adjacent buildings with minimum foundations. Is there advice available on a monitoring regime which might indicate extent and frequency of vibration damage to buildings constructed in traditional brickwork with lime mortar??

 

[bazaka]

I might be asking a dumb question but have chicanes been considered to slow the traffic?

 

[Etonbridge]

Chicanes have been considered, but not considered appropriate in this situation.

 

[rchanke]

I've used a small inexpensive Peak Particle Velocity (PPV) gauge called a Blastmate, made by Instantel. The gauge measures the PPV at ground surface and can be placed at different distances from the point of interest. Since the PPV diminishes with increasing horizontal distance, you can determine this local relation by placing the gauge at varying distances. You then will need to determine the PPV threshold for the critical structures in question.

 

[Etonbridge]

Thanks for this latest advice. I can search out Blastmate, but is there any advice on how to determine PPV threshold for a particular structure??

 

[dik]

Can you install a series of stop sighn to slow or divert traffic?

Dik

 

[Etonbridge]

The humps are already in place. The reason for the original enquiry is that there may be a need to monitor the effect of damage to local old buildings, to recommend or otherwise alternative ways of calmig traffic in this sensitive area.
We need to find out first if there is a genuine problem, to allay fears of local frontages.

 

[GeoPaveTraffic]

Etonbridge, you hit the nail on the head; determining allowable velocities is the problem. There have been many studies about allowable blasting velocities but I don't know of any for more continous velocities due to traffic. Also, realize the frequency is at least as important as the velocity.

I have also used the blastmates and they can be made to work very well.

 

[rchanke]

A common PPV threshold you may see is 2.0 inch/second. I believe this number originally came from the mining and blasting industry. More conservatively, I've seen 1.0 and 0.5 specified on some construction projects but I believe these to just be arbitrary numbers pulled from out of the air.

 

[Etonbridge]

Thank you for the input. I am seeking advice from Blastmate suppliers in this country.

 

[Ron]

For older buildings, you would likely be looking to limit PPV's in the 0.5 in/sec range. Probably the best reference for this is Richart, Hall, and Woods textbook on vibrations.

The condition you have given will result in very low frequency and probably low amplitude. These are usually not a big problem for buildings; however, checking to get the actual magnitude is better.

Some departments of transportation have limit data that you might reference. The the Florida Department of Transportation....they have a procedure to monitor vibrations during construction with PPV limits.

 

[Etonbridge]

The most relevant information found so far in the UK is BS 7385 and particularly Table 1, which gives recommended distances between road and buildings for various soil types.
TRL Report 235 also is helpful, so I am closing down this enquiry, thank you for your help.

 

[chris1468]

You may want to refer to the US Bureau of Mines recommendations. It basically gives you a line of probability based on PPV and frequency. As mentioned in previous thread, a standard in many specs calls for action if the PPV exceeds 0.5 IPS. This is based on the US Bureau of Mines compilation of data that notes that the probability of plaster cracking is most likely to happen if the PPV exceeds this level at a frequency less than 10 Hz. It also notes that the probability of structural damage is most likely to occur if your PPV is greater than 2.0 IPS at frequency at or below 40 Hz. Basically you need to monitor frequency and PPV and if possible Peak Particle discplacement. Some noted a Blastmate, GeoSonics also has some very fine models for continuous monitoring and also trigger monitoring.

 

[eric1037]

You have to be careful with the US Bureau of mines numbers. They are for discrete events, not long-term, continuous vibrations.

Although vibrations monitoring may provide a general indication of the possibility of damage, you just don't know until you observe the behaviour of the building.

I wouldn't hang my hat on vibrations monitoring alone. A complete review of the existing condition should be performed. In addition, crack monitors and surveying benchmarks should be installed and monitored to determine if there is any movement.

The best way to determine if there is damage is to continually monitor the structures. If you start to see signs of damage, then you need to do something.

 

[Grouser]

Etonbridge

Sounds like you have a great opportunity for a research project! An older building, or five, to be removed could be monitored for distress with increasing PPV and some guidelines could be established. I'll bet the historic boards and transportation department would give some funding.

Cheers

 

[OhDanny]

Etonbridge

You may want to check out the German standard DIN 4150.

Cheers

 

[mdhshanwil]

I recently attended a presentation by Gerald Verbeek of VMS-Profound (

http://www.dfi.org/memdetail.asp?id=3648)

in which he described the practice of vibration monitoring for structures. The discussion was not constrained to pile-driving, and actually touched on your specific problem (installation of speed bumps near historic structures).

He specifically referenced the DIN 4150 (part 3--1999) and BS 7385 (part 2--1993) standards, but went into detail with the Dutch SBR-2002 standard. The SBR defines 3 classes of structures (incl one for historic bldgs) and 3 types of vibrations (incidental, repetitive, continuous)and goes on to provide recommended allowable measured vibrations for each case, dependent on vibr frequency (and several correction factors).

Also, Caltrans has set some limits, including 2.0 mm/s for continuous vibrations and historical structures.