这是such ...that 的结果状语从句,意为：如此,以致
完整的句子是：The length of the bridge is such that the shape of the earth has to be taken into account.
一般such...that的句子是such用来做定语形容词修饰名词,句子通常写成：It is such a long bridge that ...
而在这个句子中such是形容词做表语用来用来说明主语(即The length of the bridge)的特征和状态的
句意：桥梁如此之长,以致不得不把地形考虑进去.
这个句子也可以改写为so...that的结果状语从句：The bridge is so long that the shape of the earth has to be taken into account.