In the modern capacity design philosophy the ductility of the structure is being utilised in order to significantly reduce seismically induced forces resulting from severe earthquake events. At the same time, however, there is also a tendency of introducing a second lower level intensity where additional requirements of a serviceability limit state have to be satisfied in order to avoid structural damage under moderate earthquakes and to assure high lifetime and continued functionality especially for reinforced concrete structures. As the design of those structural members where no plastic hinges are permitted at any earthquake intensity is strongly affected by the reinforcement contents within the plastic hinge regions the main aim must be to minimise the required hinge reinforcement which is either defined by the ultimate limit state (severe earthquake) or the serviceability requirements (moderate quake). However, the more the ductility of structure increases the more the serviceability requirements will become an increasing influence on the reinforcement demand. On the basis of investigations of two types of piers for simply supported bridges- a single cantilever column of moderate ductility and a multi column system being characterised by high ductility - The effect of different serviceability requirements (strain limitation, crack width control) is shown and recommendations for a suitable serviceability limit state are formulated in order to be able to use the advantages of high ductile structures while additionally satisfying the demands regarding safety, displacements and damage control under moderate quakes.
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