Nothing happens until the excitatory stimulus exceeds a certain "threshold" value. 兴奋性刺激超过某一临界值以前毫无反应。
The evolution of damage is determined by damage hardening condition, failure occurs when the hardening of damage reaches its critical value. 损伤演变由损伤强化条件决定，当损伤强化达到临界值时，混凝土发生破坏。
