Dynamic increase factors, reinforced

Dynamic Strength. The dynamic design strengths for steel reinforcing and concrete are equal to their static design strengths times the appropriate Dynamic Increase Factor (DIF). 

Table I. Dynamic Increase Factors (DIF) for Reinforced Concrete...

Values for dynamic increase factors are presented in a variety of references although most are based on the same data source. Additional data has been produced in various test programs but has not been assembled into a central source. Much of the data that has been published is based on high strain rate tests and many of the recommended values are arbitrarily chosen. Table 5.A.1 provides recommended DIFs for reinforced concrete and masonry and Tabic 5.A.2 contains values for structural steel, cold-formed steel and aluminum. 

Considerable effort has been spent to explain the effect of reinforcement of elastomers by active fillers. Apparently, several factors contribute to the property improvements for filled elastomers such as, e.g., elastomer-filler and filler-filler interactions, aggregation of filler particles, network structure composed of different types of junctions, an increase of the intrinsic chain deformation in the elastomer matrix compared with that of macroscopic strain and some others factors [39-44]. The author does not pretend to provide a comprehensive explanation of the effect of reinforcement. One way of looking at the reinforcement phenomenon is given below. An attempt is made to find qualitative relations between some mechanical properties of filled PDMS on the one hand and properties of the host matrix, i.e., chain dynamics in the adsorption layer and network structure in the elastomer phase outside the adsorption layer, on the other hand. The influence of filler-filler interactions is also of importance for the improvement of mechanical properties of silicon rubbers (especially at low deformation), but is not included in the present paper. 

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