设计一种适合的膜非常困难:一方面要足够坚韧,以承受压力;但同时还要有渗透性,而且只能透水,不能透盐。
Devising a suitable membrane-tough enough to withstand the pressure while remaining permeable to water but not to salt-is harder than it sounds.
另一方面使核心混凝土在受荷初期就处于侧向受压的状态,弥补钢管对混凝土紧箍力出现太迟的缺陷。
And the steel tube provides lateral stress at initial period to make up the defect that constraining force comes up too late.
气流会破坏外壳,这一面是受压的。
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