tailieunhanh - Lifetime-Oriented Structural Design Concepts- P23

Lifetime-Oriented Structural Design Concepts- P23: At the beginning of 1996, the Cooperative Research Center SFB 398 financially supported by the German Science Foundation (DFG) was started at Ruhr-University Bochum (RUB). A scientists group representing the fields of structural engineering, structural mechanics, soil mechanics, material science, and numerical mathematics introduced a research program on “lifetimeoriented design concepts on the basis of damage and deterioration aspects”. | 618 4 Methodological Implementation Fig. . Location of drilling cores drilled out from various sections of the structure for further laboratory testings Figure . The total number of drilling cores was limited by logistical reasons within the deconstruction process and in order to ensure the structural stability also during and after the core-drilling. In order to get information on the actual concrete properties laboratory tests were performed according to the same methods described in . Experimental Investigation on Mechanical Concrete Properties According to the available construction drawings the concrete used for all structural members tested now was conform to the formerly strength grade B 450 3 which correlates at time of construction more or less with a C 30 37 according to the current standards. Due to lack of more detailed information it was assumed that the concrete composition in all parts of the bridge was the same. The maximum size of aggregates could be determined on the drilling cores to 32 mm. Non-Destructive Tests In order to determine the concrete s stiffness resp. the dynamic elastic modulus Edyn non-destructive ultrasonic tests US-measurements were performed. Comparing these results the mean values of Edyn are on a similar level of about Application of Lifetime-Oriented Analysis and Design 619 Table . Dynamic elastic moduli Edyn mean and their standard deviations SD of the concrete after a service life of 50 years for the different members of the bridge structural member number of specimens Edyn SD H N mm2 N mm2 main girder 12 49 700 4 200 cross girder 8 47 600 2 700 arches 17 50 600 3 300 carriageway slab 5 50 300 2 300 cantilever section 18 52 900 5 300 50 000 N mm2 within all investigated parts of the structure Table . The standard deviations SD in Edyn vary from 2 700 N mm2 to 5 300 N mm2. This scatter of in-situ concretes exceeds significantly the experiences on Edyn of laboratory