Our Work
Over the years we have provided know-how and expertise on various projects involving earthquake engineering and instrumentation. In addition, published various articles in various journals or conferences. Some examples are presented below.
Office floor vibrations: modal parameter identification and vibration monitoring
Several people working on the 2nd floor of an office building complained about disturbing floor vibrations. The building consists of five floors. In the contrary to the other floors, the 2nd floor slab has no floor-to-ceiling secondary walls neither beneath nor on top of the slab. The modal parameters of four floors were identified using ambient vibration testing (AVT)-technology and a 5-kg-medical ball as a vibration generator. The fundamental natural frequencies of the floors were: 2nd: 7.4 Hz, 1st, 3rd and 4th: 11.5…12 Hz. To monitor the vibration intensity and to identify the source of the vibrations, a triaxial velocity sensor was subsequently mounted in a critical point of the 2nd floor slab. The vibrations were monitored for two months using a newly developed internet-accelerograph. This allowed on-line checking of the vibrations and downloading of the data on an external server on a daily basis. Processing of these data yielded that no other source of the vibrations could be identified than people walking on the floor. Rating of the measured vibrations according to ISO 2631 yielded that during working hours, the vibration level was up to 3.6 times higher than "satisfactory".
Systems and sensors for monitoring purposes
Monitoring of infrastructures in modern urban areas is centrally important to achieve, enhance and sustain human civilisation. This paper discusses the available and future possibilities and solutions for such monitoring purposes. Basic components and typical requirements of such systems, including generic hardware and software specifications are described. Different projects are presented to illustrate how a modern monitoring system can be realised with the help of latest measurement methods and technologies. An overview of the future expectations in the industry is given. Monitoring systems are unique. The utilised products must be flexible to serve the requirements. With the help of the modern technology and the latest developments in the industry as well as the increased understanding of systems and applications almost any project is possible. Efficient monitoring systems will contribute to reduced failure risk, timely operational and safety response, extended lifetime and better maintenance of infrastructures which are the building blocks of further growth, development and sustainability of our modern civilisation.
Seismic Instrumentation Of The Swiss Nuclear Power Plants
The share of Nuclear Power Plants in the overall electricity production in Switzerland is approximately 40 percent. Such important energy production assets require also lucid and up to date maintenance and operation procedures and facilities. Seismic instrumentation of most of the active Nuclear Power Plants in Switzerland have been upgraded to the state of the art technology as of June 2006. The upgrades were carried out within the framework issued by the Swiss Nuclear Authority, generally based on the regulations set forth by U.S. Nuclear Regulatory Commission. Gathering the experience gained during the upgrading of three out of four active plants, the typical approach of a distributed recording system is presented.
A dynamic uniaxial wide strip tensile testing of two geotextiles in isolation
Geotextiles must sustain static, and often dynamic loads, during the lifetime of the structure in which they are placed. A test apparatus is constructed to examine the tensile behaviour and performance of two different low strength nonwoven geotextiles under dynamic loading. The apparatus is designed as a vertical uniaxial dynamic tensile testing equipment for testing geotextiles in isolation. The nonwoven geotextiles examined both performed well under rigor- ous test conditions. Charts and tables showing the measurements taken during tests and the results of these observations are presented.
Blackbox concept can help promote widespread use of S2HM
A good example for a universally established worldwide status and performance monitoring system, which almost any person can relate to, is maybe the flight data recorder known as the “black box” in aircraft.
The broad concept of instrumental status and performance monitoring has been in use for about a century for keeping a watchful eye on many man-made structures and structural systems, and it has picked up an increasing momentum in the last few decades in comprehensiveness and intelligence.
Seismic instruments are being utilized with increasing success for Seismic Structural Health Monitoring (S2HM), regarding post-earthquake status and timely occupancy & service resumption of civil engineering structures, especially by virtue of the recent advances in the science and technology in their features and interpretation of their data. It is however a wonder why such use is not yet as established worldwide as the aircraft black box, although potential benefits of S2HM seem to be even higher considering the sheer number of civil structures located in high seismic risk areas, serving millions of people on a permanent basis.
Providing various examples of successful and large scale S2HM examples from Europe, this paper discusses utilization and promotion of such systems in the region currently, the motivations and initiatives towards a wider deployment of such systems, the difficulties or burdens facing such widespread use, along with suggestions to improve the establishment of S2HM systems as universally accepted and implemented attributes of civil engineering structures while proposing a concept similar to the aircraft black box.
An Analysis Method For Geosynthetic Reinforced Soil Structures Under Seismic Excitation
Reinforced soil structures are widely used in many urban and rural areas around the world, of which many are located in geographical regions with medium to high seismic activity. Most of these structures are parts of the lifeline network of the respective area. Therefore it is important to understand and if possible predict the behavior of these structures under an expected seismic activity. In this study an attempt is made to recall the rather old Finite Element program SSCOMP and to enhance the ability to use this program for the analysis of reinforced soil structures under given base excitations. The efforts consisted of regeneration of SSCOMP from printed material as an operational program, testing and verification of the regenerated program with respect to reports of earlier studies with the program, development and implementation of the pseudo-dynamic approach and the required script as the supplement processor, performing a number of numerical analyses and comparing the results with a case history of a centrifuge test and with the results of a commercial finite difference program FLAG. As a final step, an extended parametric sensitivity analysis for static and dynamic loading conditions is conducted. It is shown that SSCOMP, together with the implemented pseudo-dynamic approach, yields acceptable results to provide an insight on the expected behavior of the reinforced soil structures, given that the FE model, the relevant parameters and the obtained results are carefully selected, used and evaluated, respectively.
Analysis of the strong motion data of the 1995 Dinar, Turkey earthquake
Dinar earthquake (Mw 6.0, USGS) occurred on October 1, 1995 causing casualties and physical damage (Io = VII – VIII MSK). The earthquake was associated with predominantly normal faulting. The PGA in Dinar was 0.33 g. Strong motion data associated with the mainshock and aftershocks of the 1995 Dinar, Turkey earthquake have been analyzed to investigate the source, attenuation and site response parameters. Strong motion data were baseline corrected, local magnitudes were computed and inelastic attenuation parameters, seismic moments and corner frequencies were assessed. A parametric analysis is attempted to understand the correlation of damage distribution with the fault parameters. It is believed that the obtained data will complement the relatively scarce earthquake data associated with extensional regimes.