I can take only horizontal forces, add those up, and get the horizontal acceleration.

我只能承受水平力， 将它们相加，得到水平加速度。

One result of compressing an arch is that it creates horizontal forces called thrusts.

压缩拱门的结果之一是产生称为推力的水平力。

This is the horizontal force of F4, not the vertical force.

这是F4的水平力，不是垂直力。

It just so happens that this horizontal force depends on a vertical force, which is the normal force.

碰巧这个水平力取决于垂直力，这是法向力。

Additional cables, called backstays, were connected to anchorages behind each tower to balance the horizontal forces, similar to the way suspension bridges work with their towers and abutment anchorages.

额外的缆索（称为后拉索）连接到每个塔后面的锚地，以平衡水平力，类似于悬索桥与其塔和桥台锚地的工作方式。

The second tension tie may have taken up much of its partner's stress and the pier supporting the arch may have been subject to a lot more horizontal force than it was designed to withstand.

第二个张力拉杆可能承受了其伙伴的大部分应力，并且支撑拱门的桥墩可能承受了比其设计承受的更多的水平力。