Beitrag zur Bestimmung der Tragfähigkeit bestehender Stahlbetonkonstruktionen auf Grundlage der Systemzuverlässigkeit

Opportunities for the conversion of existing structures are significantly dependent on the bearing capacity. This thesis deals with capacity reserves and deficits of existing structural concrete systems. The assessment is based on reliability theory. Differences between calculated reliability and target value are determined by probabilistic methods taking into account stochastic properties of load and resistance parameters. Compensation of possible reserves and deficits can be reached by modifying partial safety factors for the semi probabilistic proof. Previous proposals for modification of the partial safety coefficients refer to componential reliability. Reliability targets in structural codes are defined for a system as a whole. For systems with multiple failure modes this may require higher reliabilities for each elementary limit state. Taking into account the system context, modified partial safety factors for element proofs are inferred. For this purpose the failure of continuous slabs and beams is modeled in logical systems and system reliability is determined as well as essential failure influences. The assessment is carried out for specific material combinations of existing structures and different types of life loads. Partial safety factors are determined in an optimization process which leads to minimization of reliability differences. Reliability reserves result in reduced partial safety factors, deficits require higher coefficients. Significant increases of life loads are possible in combination with reserves due to improved design procedures in individual cases.