This article has analyzed the current situation of old bridges,explained the advantage,application,structure and mechanics performance of the external prestress technology and pointed out its computing technology,current situation and prospect briefly.

This method advances exploration for the fast detection of numerous old bridges in China, and offers immense application foreground in practice.

Facing this situation, we must detect the existing bridge entirely first.

Owing to unfavourable circumstance, structure aging, vehicle weight incrasing and lack of maintaining, there exist inevitably structural defects in some existing bridges.

The repairing and strengthening techniques of old bridge;

Technical analysis of reinforcing old bridge with pre-stress method;

Load capacity of old bridge with fuzzy nearness comprehensive evaluation method;

The application of bonding steel plate method in old bridge strengthening;

According to current situations of old bridge the causes of quality faults and bearing capacity are analyzed, and the old bridge strengthening scheme is determined based upon those.

In this paper, firstly, the meaning of old bridge strengthening, the technology of bridge detecting and the principle of old bridge evaluation were introduced.

The application of joined reinforcing bar technique in the old bridge reinforcement;