Project Overview

(1) Provincial Highway S223 Meixian Jianying Bridge is located in Yanyang, Meixian County, across the Meijiang River in Meixian County, Guangdong Province. The total length of the bridge is 326.29m. The upper structure of the bridge is a 6X45m reinforced concrete steel arch. The lower structure uses reinforced concrete bored piles with a pile diameter of 1.4m. The bridge abutment uses a combined pile foundation and gravity abutment. In August 2007, the reinforcement and maintenance construction drawing design was completed. The reinforcement and maintenance design requires that the upper and lower structures of the bridge be reinforced. The solid web section of the main arch, the arch legs and the positive bending moment section of the chord are reinforced with unidirectional carbon fiber fabric.

(2) Meixian Y035 Line Jinjiang Bridge is located at the only passage between Bingcun and Hongguangcun on the north and south sides of the Yangtze River in Bingcun Town, Meixian County. The main bridge of Jinjiang Bridge adopts a 9-hole reinforced concrete rib arch structure with 2 holes at each end and a 10m reinforced concrete T-beam structure. The cross section of the bridge is composed of 4 arch ribs. The lower structure of the main bridge is a gravity-type solid pier and a caisson foundation. The bridge was built in 1934 and opened to traffic in 1948. After several reinforcements, it was tested by the Guangdong Provincial Highway Engineering Quality Monitoring Station in July 2009. The technical status of the bridge was assessed as a Category 5 bridge and it must be reinforced immediately before it can be used. The reinforcement design requires reinforcement of the upper and lower structures of the bridge, including all arch ribs in the mid-span of the arch rib bottom, upper chords, cross beams, damaged and exposed arch ribs and columns, and bridge deck slabs with cracks. After the bottom is repaired, it is reinforced with pasted unidirectional carbon fiber fabric.

Evaluation of the effect of unidirectional carbon fiber reinforced old bridge

After the completion of the reinforcement of the Jianying Bridge in Meixian County on Provincial Highway S223 and the Jinjiang Bridge on Meixian Y035 Line, regular monitoring over the past few years found that the carbon fiber and the original structural concrete surface are well bonded, without hollows and cracks. The reinforcement quality has been recognized by the construction unit and the design unit, achieved the design expectations and achieved satisfactory results.

Evaluation of the economic performance of carbon fiber reinforced old bridges

The carbon fiber reinforcement project does not require large construction machinery and auxiliary machinery, saving the cost of shifts. Carbon fiber is a lightweight and flexible material, which is easy to construct and reduces labor costs. Carbon fiber has good corrosion resistance and does not require regular maintenance, saving maintenance costs. For example, for Jinjiang Bridge on Meixian Y035 Line, the carbon fiber fabric reinforcement area is 1470.3 square meters, and the budgeted cost of carbon fiber fabric reinforcement is 1.3435 million yuan, which is converted into 913.8 yuan per square meter. The actual construction bid price is lower than the budgeted price.

Concluding remarks

To sum up, the unidirectional carbon fiber reinforcement technology can easily reinforce the stressed members in different parts of the bridge. It can achieve flexural reinforcement without damaging the original structure and hardly increasing the weight and section size of the structure. It is an effective new bridge strengthening technology. It should be noted that the renovation of the old bridge is different from the construction of the new bridge, and the risks and uncertainties are more complicated. Therefore, the construction sequence must be strictly followed during construction. Symmetrical construction must be carried out, and no upside-down and advanced construction is allowed. With the declining price of carbon fiber and the continuous accumulation of engineering practical experience, the advantages of unidirectional carbon fiber reinforcement technology will become more and more obvious, and the application in the reinforcement of old bridges will become wider and wider.