The Real Time Control for Earthquake Engineering Applications

The progress in active, hybrid and semi-active vibration control technique in various countries has already led to some promising results, not only for the control of wind or machinery induced vibration, but also for the seismic protection.

However, there are still several questions and tasks open for future research and technology development, prevailingly in optimisation of devices and control processes. Necessary verifications of reliability and safety interfere with reasonable initial and service costs. Under these circumstances, the control software is a crucial part of the methodology and vibration control technique.

For verification of such systems reliability, the real time control algorithm and software were developed and analysed in extensive numerical studies of authors. At present the control device is the subject of seismic tests under variable adverse conditions.

Verification laboratory tests create the part of works done under EU FP5 Human Potential Programme: Transnational Access to Major Research Infrastructures. HPRI-CT-1999-00046 ECOLEADER-SER (2000-2003), Subcontract 2865.03- Semi-active control near the base of asymmetrical structures. The testing facilities of ENEL-ISMES Seriate Italy were proposed for tests, namely MASTER shaking table and separate HJS hydraulic jack system. 

The shaking table MASTER (MultiAxes Shaking Table for Earthquakes Reproduction) is one of the most important installations in Europe for experimental studies in the structural dynamics. Besides the classical support of the earthquake engineering, the performances, dimensions and payload capacities of MASTER allow a wide range of applications both in civil and electromechanical fields. This facility was used for the first group of tests and it is foreseen also for the third group of tests.

Independent HJS hydraulic jack system was used for the second group of tests and it is foreseen also for the third group of tests together with MASTER shaking table. Interconnection of original HJS system with real time control software from outside control computer was successively tested and verified on single mass model. The information given in Figures 1 and 2 suggests promising behaviour of tested model and remarkable mitigation of the model vibration.

Earthquake is a sudden event and comes to the structure like unknown time history that should be overcome by control system. The quick and reliable response is the basis of actually effective seismic response mitigation.

As far as the second group of tests was realised without use of shaking table, the external source of unknown independent disturbance input had to be used. Such inputs were created by:

·     impact tests (Fig. 1) and

·     external source excitation (Fig. 2).

The external source of excitation has appeared as unexpected input that helped in testing of the control algorithm efficiency. Independent specimen was subjected to seismic tests on MASTER shaking table. During some stages of these tests the shaking table motion caused induced subsoil vibration that travelled through foundations also to HJS base and excited tested single mass model.  Upper part of Figure 2 gives the information about the model response changes when the control was switched on, the lower part describes the situation of the model response when the control was switched on and then switched off again.

The impact tests utilised general force impulse. The model response can be seen in Figure 1. The upper part represents the case when no control was introduced, while the lower part gives the information about the model response when the real time control came into play. It can be seen that the drastic decrease of response came very soon after the impact excitation.

Figure 1. Response of single mass system to impact excitation results of laboratory tests.

Figure 2. Response of single mass system to induced seismic excitation – results of laboratory tests.

The research is not finished yet. The authors are aware that not only software but also devices alone are continuously subjected to modifications and improvements. Therefore, besides many direct connections they welcome the response of any nature or comparative studies. The participation and support of ENEL-ISMES staff, namely G.Franchioni and G.Bergamo is gratefully acknowledged.

E. Juhasova¹, M. Juhas² & V. Svrcek²

¹Earthquake Engineering Laboratory ICA SAS

²Department for Automation and Control MEF SUT