Why did the Advertising Standards Authority have to rule on what should be common knowledge? What is HAVS monitoring best practice, what do insurers say and could zero monitoring be the best option? You would have thought that the issues surrounding wrist-mounted vibration monitors had already been thoroughly settled. Apparently not so in the minds of some. The following is an outline of some of the very costly myths associated with
Ground, Building and Plant Vibration
A complete range of vibration measurement, evaluation and control services for the construction and demolition industries that extend well beyond conventional monitoring.
We not only provide a complete range of conventional services covering all aspects of environmental and occupational noise and vibration for the construction and demolition industries, but also a range of additional innovative management and control techniques based on our unique engineering expertise. These are not only re-defining what constitutes best practice under the regulations and standards, but are also dramatically reducing project costs and delays. Our reputation is based on the results we have achieved from introducing new procedures and techniques into a largely traditional industry.. Specific areas of expertise include:-
- Vibration sensitive equipment installation: – metrology – machining – computers..
- Electronic fabrication plant vibration specifications: – source diagnosis..
- Structural building vibration: – structural responses – office floors – human response to vibration..
- Piling / demolition / construction vibration monitoring / assessment: – best practice control and management – limits..
- Vibration from industrial premises: – monitoring – source identification – vibration limits – vibration control..
- Transportation vibration: – building damage – transmission ..
Construction and Demolition Vibration
Noise and Vibration Management and Control Innovations – more options, reduced costs….
The following are some of the innovations we have brought to the industry ….
- Vibration testing – party walls, slab short-circuits: rapid evaluation of vibration transfer paths, reduces costs and guesswork
- Continuous vibration monitoring (and noise) – real-time feedback (SMS) cuts costs and complaints: eliminate exceedence notification time lag – real-time site activity control and reduced costs
- Demolition noise and vibration scheduling / prediction tools: – activity scheduling for prediction and management of demolition noise and vibration levels v targets
- Pile cap / concrete raft explosive demolition – vibration prediction and PR presentations
ENVIRONMENTAL VIBRATION MONITORING AND CONTROL CASE STUDIES
Heathrow Terminal 3 Piling Noise and Vibration Monitoring
Building a new terminal 3 multi-storey park above the Heathrow Express underground station was a major technical challenge. Piles had to be bored 40m into the ground very close to access and train tunnels – without disturbing structures or personnel. BAA selected INVC to carry out an extensive vibration and noise monitoring programme over several months. The turn-key project involved installing an array of transducers in the tunnels with detailed analysis and continuous remote monitoring of the piling vibration via GSM. The INVC designed system also included a facility to alert key personnel automatically via SMS text message if the vibration exceeded threshold trigger values.
Shard of Glass Demolition: Site Noise and Vibration Monitoring / Logging / PR
Adjacent to London Bridge Station and Guy’s Hospital…
Whilst the Shard is the tallest building in the UK, we were involved when it was a hole in the ground. The location abuts London Bridge Station with Guy’s Hospital just across the road. You could scarcely have asked for a site that was potentially more sensitive to noise and vibration. Keltbray, the demolition contractor, wanted to use the technically advanced explosive techniques developed by the Controlled Group to remove the pile cap in the basement of the office block on the site. Removing this massive slab of concrete by conventional means would have extended the project by c 2 – 3 months – but noise and vibration were potential deal-breakers. We were asked to provide the noise and vibration predictions, logging and monitoring services required to justify the decision both in terms of potential risks and to minimise the duration of the process and the environmental impact. We also provided key multi-media presentations to all the parties involved (station, hospital, security etc) to present the predictions and provide the technical reassurance necessary to assuage any concerns about noise and vibration issues.
Piling and Train Vibration Assessment – controlling piling vibration
A detailed vibration assessment of the impulses from a drop-hammer piling operation was carried out in response to concerns from local residents about potential structural damage to their houses. The results showed that the vibration level was very close to the DIN 4150 damage limit guidelines which posed a question as to possible claims for compensation. Instead of halting piling operations, however, a detailed vibration analysis allowed modifications to be developed for the pile helmet. These reduced the ground vibration by 65% to well below the structural damage criteria, allowing the project to continue on schedule. In a similar case involving piling near a railway line, we reassured the residents by demonstrating that whilst the piling operations were subjectively very evident, the passage of trains actually generated a very similar level below the structural vibration damage criteria.
Building Demolition Vibration Management – Best Practice
Demolition vibration was causing problems in the adjacent office block. A very extensive and costly array of conventional vibration monitoring systems was in use as part of a time consuming and unsuccessful management process leading to potentially very costly delays to the project. Our detailed building vibration analyses proved that the cost and hassle of the extensive vibration monitoring could be eliminated and that introducing a number of counter-intuitive demolition vibration management procedures would significantly reduce the problem. Coupled with developing a purpose designed project vibration management software tool, the “best practice” noise and vibration management process for the project was simplified and re-defined, minimising the likelihood of further costly delays.
Office Floor Vibration “.. it makes me feel seasick ..”
One of the open-plan office floors in a very prestigious new office development had been designed with a very low profile to provide more space within the building. Unfortunately it had a natural frequency of 3.6Hz and low damping and as staff walked across the floor, the vibration amplitude would rapidly build-up. After a few steps, the whole floor would be oscillating causing PC monitors to sway and some staff to complain of incipient motion sickness. Based on a detailed analysis of the structure and response, a minimal set of disguised stiffening beams were designed and fitted (to avoid impinging on the open feel of the office). These increased the vertical stiffness by 70% and introduced more damping, solving the problem.
Rolling Mill Vibration Control – ground-borne environmental vibration control from industrial plant
A Local Authority had been investigating complaints about ground vibration from residents near a factory using rolling mills. Narrow band frequency analysis of the vibration revealed two distinct and separate types of vibration – tonal vibration at 18.25 Hz (and harmonics) plus a regular “thump”. The source of the “thump” was traced to roller backlash caused by bearing wear at the transfer gear end of a particular mill. The tonal component was diagnosed as excessive vibration at the tooth mesh frequency of the pinion on another mill caused by worn teeth on the gear. The “thump” could be eliminated by replacing the bearings. However, as production requirements precluded immediate down-time, the interim solution recommended was to avoid running at idle and to adjust the clamping force to minimise the backlash. Inspection of the pinion gear source showed very worn pinion drive tooth flanks in mesh with “new” flanks on the driven gear. The tonal vibration was eliminated “on-the-spot” by reversing the pinion. This case study illustrates the benefits of sophisticated diagnosis coupled with engineering expertise. A low cost solution to a complex and intractable problem was implemented within hours of arriving on site.
Computers Servers, Sensitive Equipment Vibration Limits, Monitoring and Control
We have considerable experience of establishing ground and building borne vibration limits and specifications for a range of vibration sensitive equipment. These range from computer systems and hard disks, servers, metrology equipment, electron microscope and nanotechnology facilities and electronic fabrication plant . Our speciaiist expertise allows us to determine the best practice building vibration monitoring and control regimes for these vibration sensitive facilities and, if necessary, to design bespoke monitoring systems.