Abstract
The civil infrastructures deteriorate over time and their reliability is time variant. To mitigate the deterioration of
structures, the maintenance, monitoring, inspection, etc. are needed. To optimize the cost of structure, life-cycle design
of structure is urgently needed. Different from current structure design theories, the design index of life-cycle design
should be able to reflect the time variation of structure directly and provide reference for making maintenance decisions,
but the performance indices of current design theories can't meet these requirements. For the deficiencies above,
life-cycle design is introduced herein and life index of structure is defined. The properties, functions and determination
principles of the structural life index are concluded as well. An example is also presented, in which the process of
obtaining life index is demonstrated. The freeze-thaw action spectrum of Harbin is utilized and the life index of certain
common concrete under freeze-thaw action in Harbin is obtained herein. The result shows that the life index of that
concrete is only 6 years. The investigation will be helpful for controlling the structure life-cycle cost, and can promote
the development of life-cycle design.
