Bridge Overview

Zaozhuang Shizihe Bridge is located in Tengzhou City, Zaozhuang City, with a total length of 259.62m and a width of 9m+2×1.0m sidewalk. The upper structure is a 5×13m hollow slab beam + 6×20m reinforced concrete simply supported T-shaped beam + 5×13m hollow slab beam, which was opened to traffic in 1981.

Analysis of the main diseases and their causes

The bridge has been put into operation for more than 20 years. With the rapid development of the national economy, the traffic volume has continued to increase, the traffic volume has continued to increase, and the vehicle models have continued to become heavy, which has caused the bridge to increase its load. There are vertical and oblique stress cracks at the mid-span and 1/4 of the main beam of the T-beam, and the maximum crack width is 0.14 mm. The mortar on the concrete surface layer of the outer wing plates on both sides of the T-beam main girder and the webs on both sides of the web is aging and falling off in a large area. Local stirrups on the bottom of the main beam web are exposed and corroded, and concrete honeycombs and holes in some parts are severely exposed and corroded, which has seriously affected the performance of the bridge. There is an urgent need for high-tech reinforcement repair materials and construction techniques that are effective, durable, and easy to construct.

Reinforcement design

According to the evaluation and analysis of the test report, a reinforcement and maintenance plan was formulated: in order to enhance the bending resistance of the main beam, a carbon fiber sheet was pasted on the bottom of the T beam, and a carbon fiber sheet was pasted on the side of the beam end along a 45 degree direction to enhance the beam's shear resistance.

Carbon fiber sheet and structural adhesive

Carbon fiber reinforced plastic (CFRP) reinforced concrete structure technology belongs to the interdisciplinary of high-tech materials and civil engineering. At present, it has been rapidly developed and widely used in Japan, South Korea, the United States and other countries, Europe, and Taiwan. In the field of civil engineering, as a new type of concrete structure reinforcement material, carbon fiber sheet has the following characteristics compared with the traditional glued steel plate:

(1) High strength, light weight, small weight gain after construction;

(2) Good cutability, convenient construction and shaping, no large construction equipment, fast construction period, and easy quality assurance;

(3) Good corrosion resistance, not only resistant to cement alkali, but also applicable to corrosive environments such as salt erosion, with good aging resistance and long service life;

(4) Good seismic performance, especially suitable for reinforcement and transformation of concrete structures such as buildings, bridges, and underground tunnels;

(5) It has a wide range of applications and low overall cost, which saves a lot of funds needed for reconstruction.

After performance comparison and economic analysis, the 12K and T700 carbon fiber precursors imported from Japan’s TORAY are finally used. Modified by Shanghai Hummer Co., Ltd., it is woven into a carbon fiber unidirectional sheet suitable for structural reinforcement. Its characteristics are high strength, low performance dispersion, good stability, and easy construction and cutting

Engineering construction quality inspection and evaluation

After the completion of the construction, an on-site pull test was carried out to determine the bonding between the carbon fiber sheet and the concrete and the construction quality. The test results show that the construction quality is good, and the bonding between the fiber sheet and the concrete interface is very ideal (the positive tensile bonding strength is greater than the 2.5MPa required by the specification), and the effect of joint stress is achieved.

The bridge uses carbon fiber sheets produced in China to reinforce the bridge. The construction and testing prove that it is technically feasible, technically reasonable, convenient for construction, and saving money, which broadens new channels for the reinforcement of the old bridge. Engineering practice and test results show that the Horse series carbon fiber sheet has a stable structure, is not loosely cut, is conducive to resin infiltration, easy to eliminate bubbles, is convenient for construction, has fewer material defects, stable mechanical properties, and a dispersion coefficient of only 3.7. Fully meet the requirements of strengthening concrete bridges.