How were the arch bridges built in ancient China?

Because there is no specific architectural design record on how to build an arch bridge in ancient times, it is necessary to speculate on building an ancient arch bridge according to the actual scientific and technological level and productivity level in ancient times.

(1) Structural form and mechanical characteristics of arch bridge.

Under the action of vertical load, under the condition of reasonable arch axis, the arch, as a stressed member, should try to avoid the axial force and bending moment of the main bearing, so as to give full play to the characteristics of arch rib section as an axial stressed member and make efficient use of the member section. Now we know that the arch is an axial force member, so at the end of the arch, that is, the arch foot, X force and Y force are generated. Therefore, the key stress problem of arch bridge is the strength of arch rib itself and arch foot foundation under horizontal and vertical forces, and the arch bridge is more reflected in the horizontal force, that is, the arch bridge should eventually be a thrust structure.

(2) The structure and architectural ideas of ancient arch bridges in China.

Most of the ancient arch bridges in China are through arch bridges, that is, the deck system and transfer structure are above the arch ring, which is the so-called architectural arch, that is, the so-called through arch. The bridge deck bears the load directly, and then it passes under the arch ring and finally to the arch foot.

First of all, arch rib is a kind of compression member, and the ancient materials are mainly wood and stone (I will mainly discuss stone arch bridges and wooden arch bridges). Stone is a good masonry material, similar to concrete now. Choosing a good masonry material for compression members shows this link in the selection of materials by the ancients.

Then, regarding the arch axis radian mentioned, I also want to explain that the choice of arch axis today mainly depends on arc, quadratic parabola, high-order curve, catenary and so on. There is a key question, which mentions why the radian of the axis of the ancient arch rib is large, because the radian and the arch rib effect, that is, the compression characteristics can be reflected.

Finally, the choice of foundation. As we all know, the foundation of Zhao Zhouqiao is very good, and the problem involved here is not the so-called one-sided arch bridge. The so-called barge scouring and foundation settlement have a good control effect on Zhao Zhouqiao, and the foundation as the lifeline of the arch bridge is extremely critical.