MAURER Seismic Protection
15Pages

I Structural Protection Systems MAURER SOHNE

| Structural Protection Systems Frankfurter Ring 193, 80807 Munchen / Germany 1.2. General aspects of seismic protection 3 1.2.1. Protection by energy distribution 3 1.2.2. Protection by basis isolation and dissipation 4 2.1.1. Low damping rubber bearings (LDRB) 7 2.1.2. High damping rubber bearings (HDRB) 7 2.1.3. Rubber bearings with lead core 7 2.2.1. Sliding bearings without recentering (SI) 8 2.2.2. Sliding isolation pendulum (SIP) - recentering 8 2.2.3. Double sliding isolation pendulum type D - recentering 9 3.1. Shock transmitter (MSTU) 3.2. Shock transmitter with overload...

1. Introduction Today’s state of art allows to adopt all kind of structures to the different loads due to traffic, wind, seismic events etc.. Thus the tensions are proportionally distributed to the whole structure or they are reduced from the beginning by isolation technique and additional damping. As each structure shows individual characteristics, no general concepts do exist for seismic protection. Project relevant choice of the mechanical components is required to individually calculate and design the structure for seismic events. A specially adapted seismic protection system avoids...

1.2.General aspects of seismic protection 1.2.1 Protection by energy distribution Longitudinal direction of bridge Energy distribution means, that the seismic energy proceeding from the subsoil is distributed to different structural components and thus significant energy accumulation is avoided. For this, special components, so-called Shock Transmission Units are used, which allow relative movements due to temperature differences and shrinking/creeping during normal service load (fig. 4). Only with seismic effects or other suddenly arising effects due to traffic or similar, MAURER Shock...

1.2.2. Protection by basis isolation and dissipation 2 Basis isolation and dissipation result in decreasing the energy applied to the system and the transformation from energy to heat. This is also designated as “energy approach”, which especially takes into account the energy character of a seismic event. Applying this systems means prevention of cost-intensive structural stiffening and attainment of maximum protection of persons and structure. acceleration of a nonisolated structure reduction of a acceleration of isolated structure periodical displacement Fig. 7: Characteristic response...

If flexible piles do exist – e.g. high piles in the middle of a bridge – the restoring force for the seismic protection system and the superstructure is guaranteed by the flexibility of the piles, which act as rod-shaped springs. In that case, longitudinally fixed bearings are installed on the flexible piles (fig. 10). Fixed and longitudinally fixed bearings do not allow any relative movements between pile and superstructure. Flexible piles are bending on a seismic event, thus creating restoring forces. At the same time, this system isolates the superstructure at least mostly from the...

2. Bearing elements for basis isolation 2.1. Elastomeric bearings 2.1.1. Elastomeric bearings Elastomeric isolators consist of several superposed steel sheets, which are connected by a special elastomer (fig. 13). The isolators transmit the vertical loads from the structure by simultaneous rotation and automaticl recentering, which is dependent on the height of the elastomer and its shear force. Lastmentioned is between 0.6 and 1.0 N/mm². Damping of the elastomeric isolators totals to 6 – 15 %, dependent on demands, and can thus individually be adjusted to each structure. However in many...

2.1.3. Rubber isolatores with lead core Similar to conventional rubber bearings the vertical load of a lead rubber bearing (LRB) with lead core is accommodated by the rubber. To increase the damping up to 40 %, additionally one ore more lead cores are vertically inserted into the rubber (fig. 14 & 16). In case of horizontal displacements, a distinctly higher resistance force is activated due to the lead core, that way providing a more complete hysteresis with higher damping effect (fig. 15). Fig.16: Rubber isolators with lead core (LRB) 2.2. Sliding isolators Sliding bearings consist of an...

2.2.1 Sliding isolators without recentering capacity (SI) Sliding isolators type SI (= sliding isolator) without recentering capacity consist of a horizontal sliding surface, allowing a displacement and thus dissipating energy by means of defined friction between both sliding components MSM® and stainless steel (fig. 20 & 21). The hysteresis curve of fig. 22 shows the typical course of friction force in dependence on the displacement direction, compared with a sliding isolation pendulum with recentering capacity. As, apparent from the hysteresis curve, no elastic energy is created, thus no...

2.2.2 Sliding isolation pendulum with recentering capacity (SIP) Compared with sliding isolators, sliding isolation pendula (SIPs) with recentering capacity have a concave sliding plate (fig. 24). Due to geometry, each horizontal displacement results in a vertical movement of the isolator. Thus a part of kinetic energy is transformed into potential energy. The potential energy, stored by the superstructure, which has been pushed to the top, automatically results in recentering the bearing into neutral position This restoring force can also be taken from the hysteresis curve for types SIP...

3. Hydraulic coupling and damping elements 3.1 Shock Transmitter MAURER Shock Transmission Units (MSTUs) are maintenance-free, hydraulic devices, to rigidly connect structures, which are moveable relatively to one another, in case of suddenly arising dynamical shocks as e.g. earthquakes, brake forces etc.. MSTUs are installed separately into the structure or combined with bridge bearings. In specialist literature also terms like Lock-Up Device (LUD), Rigid Connection Device (RCD), Seismic Connectors, Buffers or similar can be found for these mechanical devices. Dependent on the motion...