Environmental Influences and Design of Structures

In the railroad industry, structures usually are designed by applying static load assumptions. In reality, however, cyclic loading, creep, temperature, and environmental influences occur which should be considered in adhesive joint design. Generic physical models taking into account all the possible effects are not applicable for a practical design concept. 

Multiplication of factors is sometimes used in order to cover each single influence. However, this quite conservative approach results in over-dimensioned joints which cannot be reahzed in practice. Furthermore, accelerated aging tests 

For the adhesive joints which were investigated here, only some aspects wiU be discussed. The general results can be summarized as follows. A one-year exposure of bonded single lap shear samples to European and Californian ch-mates did not show any influence on the static strength of the joints. Higher temperatures (70 °C) reduced the strength by a factor between 0.25 and 0.65. 

Low temperatures seemed to have httle influence on strength. Water immersion for one month yielded a reduction in strength by a factor of about 0.8. Very strong influences were detected for some cleaning agents. 

S-N curves have to be determined at each relevant temperature. 

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