Introduction

In industrial enterprises, such as petrochemical industry, the original structural use and use environment have been changed due to mergers and acquisitions between enterprises or the change of upstream process, which requires housing inspection and identification and subsequent reinforcement and transformation.

 In recent years, as one of the reinforcement methods of reinforced concrete structures, carbon fiber reinforcement has been widely used in highway, bridge, tunnel and construction reinforcement projects. While carbon fiber itself has high strength and high elasticity, it also has the characteristics of light self-weight and good durability. 

General situation of Engineering

A foreign-funded chemical company purchased a paint and paint chemical plant. Due to the need of process upgrading and transformation, the foreign-funded company required housing inspection and appraisal of the main production plant. The inspected workshop is a three-storey reinforced concrete frame structure with pile foundation. The building area of the workshop is about 5200 m2. After testing by a professional inspection institution, it was found that the diameter of steel bars in the floor of the main workshop did not meet the original design requirements, and the necessary reinforcement measures should be taken for the inspected workshop.

Defect

The diameter and quantity of column longitudinal reinforcement by random inspection meet the design requirements. The deviation between the measured values and the designed values of column stirrup diameter and spacing by random inspection is within the allowable deviation range and meets the design requirements. The diameter and quantity of the bottom reinforcement of the selected beam meet the design requirements. The deviation between the measured values and the designed values of the diameter and spacing of the stirrups of the selected beam is within the allowable deviation range and meets the design requirements. There are three points in the diameter of the steel bar in the floor which do not meet the design requirements. The deviation between the measured and designed values of the steel bar spacing is within the allowable deviation range and meets the design requirements. The deviation between the measured and designed values of the geometric dimensions of columns and beams and the thickness of floor slabs is within the allowable deviation range and meets the design requirements.

After analyzing the inconsistencies of the three floor rebars, it is found that the diameters of transverse and longitudinal rebars are inconsistent. In the original design drawings, separate reinforcement is used for floor reinforcement. The upper support reinforcement and the lower through-long reinforcement of each slab are individually allocated, and the diameter spacing is different, which undoubtedly brings difficulties to the construction. The construction unit's builders are not serious enough to view the drawings, which will lead to the above problems.

Selection of Reinforcement Materials

According to the problems found, it is decided to consider the most disadvantageous situation of the production plant and design the reinforcement. It is assumed that the slabs with different diameters of steel bars in the two directions of floor slab bottom in the original design are all assumed to be smaller diameters ~8@200. Because only the bottom of the floor is strengthened, the structural analysis and calculation of each floor are carried out according to simply supported four sides.

The floor thickness of the factory building is 120 mm, and the minimum reinforcement ratio is p = Max (0.2, 45ft/fy)%=Max (0.2, 45*1.57/270)%=0.26%. Therefore, the minimum reinforcement ratio of the floor is 312 mm2 per extension meter. In the original design part, the structural reinforcement is (I~10@200). Considering the most disadvantageous situation ~8@200 (252 mm2 per extension meter), about 50% of the floor reinforcement of the second floor and the third floor do not meet the minimum reinforcement ratio requirement, so structural reinforcement is needed.

The selection of reinforcing materials is due to the following characteristics of carbon fiber reinforcement:

(1) Light self-weight, small space constraints in construction;

(2) High strength, flexibility, can wrap complex shape components, suitable for various components surface;

(3) Resistance to chemical corrosion and harsh environment such as acid and alkali;

(4) Anti-aging, excellent water resistance;

(5) The storage life is long, and the operation time is long. The base material can be concrete, masonry and other structural materials.

(6) High temperature resistance, creep resistance under load, good corrosion resistance and seismic performance.

Therefore, the production plant decided to adopt carbon fiber reinforcement scheme.

Conclusion

After taking the above measures, the CFRP reinforcement project of the main production plant of the chemical company passed the final acceptance, repaired the defects of the original plant at a smaller cost, dispelled the concerns of the subsequent owners, and successfully completed the acquisition.

There are many possibilities for technological upgrading and technological renovation in the later stage of industrial production plant, and many aspects are involved. Structural reinforcement and renovation create possibilities for the adjustment of technological layout. With the continuous improvement and maturity of design and construction method experience, carbon fiber reinforcement as one of the important methods of structural reinforcement and transformation increasingly reflects its reliability, economy and practical operability.