New devices to control, limit and damp the shocks and vibrations.

Serban, Viorel ; Mohora, Cristina

Abstract: The paper presents SERB--SITON method to control, limit and damp the shocks, vibration, and seismic movements with applications in buildings, technological equipments and pipe networks. The control is to be developed by means of SERB mechanical devices which have non-linear geometric stiffness with strengthening and controlled damping. SERB devices can be made in a large variety of dimensions, with high reliability and safety.

Key words: SERB devices, non-linear stiffness, control, damping, shocks, vibrations, seismic movements.

1. INTRODUCTION

In order to reduce the effects of shocks, vibrations and seismic movements on building equipment, piping, etc. this paper presents the results obtained by SITON on the concept, design, construction, experimental testing and application of new types of devices, called "SERB". These are capable to overtake large static loads, to allow displacements from thermal expansions or yielding of supports and can elastically overtake in any work position, large dynamic loads which they damp (Ispas et al., 2005).

The first industrial application related to shock & vibration reduction took place in 2003. It was aimed to isolate a 1250Kg forging hammer located in the Forging Workshop (IUS--Brasov, Romania) and the inlets and outlets pressurized air pipe.

The next application was to reduce the vibrations in the pipe networks in Heavy Water Production Plant (ROMAG-PROD in Drobeta Turnu Severin, Romania), and strengthen ground-floor and 5--storey building with reinforced concrete frame structure (NAVROM--Galati, Romania) etc.

The quality certification of SITON isolation was granted per DIN 4150 Standards, by measuring the vibration speed amplitude in several different locations.

SERB supports & devices are certified in Romania by TECHNICAL AGREMENT 016-03/144-2005 (Serban, 2005).

2. REDUCTION OF SHOCKS, VIBRATIONS AND SEISMIC MOVEMENTS AT EQUIPMENT

The shocks & vibrations generated by the operation of forging hammers (IUS--Brasov, Romania), are conveyed to the foundation ground affecting both the near building safety and the comfort of the surrounding building inhabitants (Serban, 2003). To reduce the vibrations, SERB-SITON isolation solution was applied in two cases (in 2003 and 2005).

SERB-SITON isolation solution is highly efficient because the average isolation coefficient experimentally obtained is about 97% for shocks generated by the operation of the forging hammer (Serban, 2005).

For small and average weight equipment and pipe networks, SERB supports and devices may be adjusted, after installation, in point of stiffness and damping capacity so to "tune" the entire assembly to shift from the resonance range.

3. REDUCTION OF SHOCKS, VIBRATIONS AND SEISMIC MOVEMENTS AT BUILDING

3.1 Case 1--Building Isolation

By the use of SERB-I mechanical devices to isolate buildings, the maximum seismic acceleration of the supra-structure is not exceeding 0.05 g if the devices can entirely overtake the foundation ground seismic movements.

[FIGURE 1 OMITTED]

The figures 1 and 2 illustrate the force displacement characteristics obtain by the dynamic tests conducted by means of some hydropulses with one element of SERB-I devices (Serban et al., 2005).

[FIGURE 2 OMITTED]

3.2 Case 2--Building distortion control

Building distortion control solution consists in the insertion of some SERB-B mechanical devices into the flexible building structure (usually steel frames or reinforced concrete frame). The devices are installed in the telescopic braces into the walls by means of which the relative level distortions are controlled (see fig. 3, 4). By this procedure a low transfer of the seismic movement from the foundation building and a reduction of the stresses in the structural elements are obtained. The telescopic braces allow a relative level displacement of 0.3%-0.5% of the storey height (function of the building type).

[FIGURE 3 OMITTED]

SERB-B devices offer the building seismic protection by the control, limiting and damping of the vibrations in the sense that the lengthening or shortening of the telescopic braces may limit the relative level displacements and the loads in the columns and beams to pre-set values.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

Figure 5 shows the SERB-B devices forces-distortions characteristics (KN - mm)

4. CONCLUSIONS

According to the results obtained by now, SERB type supports and devices proved that they can be made in a large variety of dimensions and mechanical parameters, with high reliability and safety. For this reason, such supports can be successfully employed to control, limit and damp the shocks, vibrations and seismic movements for any type of building, equipment and pipe network, NPP's inclusively. The average degree of isolation against shocks & vibrations is about 97% for certain cases (Serban et al., 2006).

Compared with the telescopic "unbounded braces SERB-B devices show the following advantages:

* Braces with SERB-B devices are non-linear and have damping even at very small distortions. The non-linearity in the case of SERB-B devices is of geometric type without overstressing the parts (components) responsible with the nonlinear behavior and damping of the device, a fact that guarantees a safe operation for a very large number of cycles (over [10.sup.10]).

* SERB-B devices can be pre-stressed at pre-set values and this allows the adjustment of the limit for which their distortion is starting as well as the value of the damping so that the dissipation of the seismic energy develops at small distortions of the building,

* SERB-B devices can stop, without shock, the structure distortion at the pre-set values providing the preservation of the structure integrity.

Compared with the hydraulic dampers, SERB-B devices show the following advantages:

* The hydraulic dampers are developing only a damping force while SERB-B devices are developing a damping force simultaneously with the development of a non-linear elastic force. This allows the control of the building vibrations, not only the damping.

* The number of cycles and the time-period for which SERB-B devices are guaranteed, are tens of times greater than those of the hydraulic dampers.

* SERB-B devices have a simple structure, low costs and the fabrication does not require special machining, as that of the hydraulic dampers.

5. REFERENCES

Ispas, C., Zapciu, M., Mohora, C., Anania, D. (2005) Theoretical and experimental studies of the spindle of high speed turning machine, Scientific Bulletin, serie C, Machine Manufacturing Technology, ISSN -1224-3264, Baia Mare 2005.

Serban, V, Sireteanu, T., Mohora, C., Anania, D. (2003) Smart devices against schocs and vibrations, Proceedings of the International Conference of Manufacturing Systems ICMAS 2004, Tome 49, ISBN 973-27-1102-7, Editura Academiei Romane, Bucuresti.

Serban, V. "Damping of Vibrations generated by the CM 1250 kgf forging hammer, located in Forging Shop SC IUS SA Brasov, Romania", Contract SITON nr. 209/17.07.2003.

Serban, V. Patent no. 119845/29.04.2005 Sandwich structure, device including the sandwich structure and device network for taking over and damping the loads for structure behavior control";

Serban, V.Technical Agreement 016-03/144-2005. Permanent Technical Council for Buildings, Bucharest, Romania.

Serban, V., Mohora, C., Anania, D., Lungu, B. (2006)--New supports for vibration&seismic motion protection of machines and equipment, International Journal Engineering&Automation Problems, Moscova, Rusia, ISSN 0234-6206, pag. 104-111.