ErschĂĽtterungsmessungen Schwingungsmessungen  

Concerning hard- and software we are closely co-operating with GeoSIG Ltd, Othmarsingen, a Swiss world-wide leading company in the monitoring field (www.geosig.com), However, rci dynamics is responsible for planning, execution and processing of such tests.

Corak Engineering, Zurich, (www.corak.ch), is our partner in the cases where monitoring the health of civil engineering structures (e.g. cracks, displacements etc.) is asked for.

Sensors
Three-dimensional geophones GSV 320 (L_GSV320.pdf) or GSV 310 ( gsv_310.pdf), In some cases MEMS-Accelerometers.

Data Acquisition
GCR-16 Recorder (L_GCR16d.pdf). Remote control and data download using a GSM connection.(Project Stallikon).

IA-1 Recorder (L_IA-1.pdf). This is the optimum solution in cases where continuous high-frequency data acquistion is needed. In these cases a broadband internet connection should be available to allow easy data download ( 2005 eurodyn paris mainau.pdf).

Monitoring and Signal Processing
GeoDAS software package (L_GeoDas.pdf).

The standard situation can be described as follows: Adjacent to existing buildings construction activities are planned. These activities include e.g. using of heavy equipment, blasting or ramming. The owners of the existing buildings want to make sure their structures are not damaged due to the planned construction activities.

As a first step, the state-of-health of the existing buildings (cracks) has to be carefully defined and documented by a third party. We rely on Corak Engineering here (http://www.corak-ch).

As a second step, instrumentation and admissible levels of vibration, in most cases of velocity (see last parapraph) have to be defined. Based on our experience we can offer consultancy here.

The standard procedure consists of installing two measurement devices, one on the foundation, the other one at the top floor. These usually consist of a GSV-320 plus a GCR-16 with GSM-modem. They measure, acquire and store the 3D-velocity vibrations.  Unless the admissible level is surpassed, the daily report contains a graphic display of the measured maximum values per minute. In case of the admissible value being surpassed immediate action is taken (see below) (Project Stallikon).

Permanent Recording: The admissible level agreed on not being surpassed, the GCR-16 device stores the maximum-per-minute value for all three directions plus the vectorial sum of the three on a local chip. Daily or weekly downloading of this data is performed using a GSM connection between GCR-16 and our office.

Event Recording: In case the admissible level being surpassed, two things happen: a) A respective alarm is distributed to up to four recipients via GSM, and, b) the GCR-16 stores the measured signals continuously during a time window and with a pre-trigger time to be chosen. The sampling rate can be chosen to e.g. s = 100 Hz or s = 200 Hz. Downloading of the stored time signals can also be performed using the GSM connection.

Comprehensive solutions. There are cases where more than one structure is to be monitored and/or where monitoring consists of high-frequency, 24-hours-per-day data acquisition for several weeks. It is then necessay to dispose of a high-speed internet connection. (Downloads: 2007 ISMA Leuven Mainau.pdf).

Again, concerning hard- and software we would rely on GeoSIG LTd. (www.geosig.com). This company solves such comprehensive problems on a world-wide basis. The hardware core part would be an IA1 connected to a GSV-320. The IA1 downloads the locally stored data files (3D with s = 100 Hz for 24 hours equals to 17 MB) to an internet server. This data can be downloaded to the office computer on demand. This procedure covers the problem of longterm, high-frequency monitoring of three channels. In case of more channels having to be monitored, a CR-5 or its portable version CR-5P should be used (L_CR-5.pdf, L_CR5P.pdf).

Rating of measured vibration levels:

Structures: SNV 640'312a, DIN 4150-2. These standards offer very vague rules when it comes to rating the probability of damages due to vibrations. We offer consultancy in this quite delicate matter.

Human Beings: ISO 2631, DIN 4150-3. These standards are formulated very clearly and are hence easy to use.