Changing Hunan Dongwei Industrial Park into Huawei Factory Building

The main reinforcement methods are enlarged section reinforcement method, bonded FRP composite material reinforcement method, high-performance cement composite mortar reinforcement method and anchorage technology of planting steel bars used with structural reinforcement method.

1. Background of the project


In April of this year, the project of Changsha Intelligent Manufacturing Industrial Park of Weichuanli started in Wangcheng Jingkai District to build an Intelligent Manufacturing Industrial Park for the next 20 years in Changsha according to the industrial 4.0 standard. This is also the first batch of projects in Hunan's newly introduced top 500 enterprises, with a total investment estimated at more than 5 billion yuan.


As an important partner of Flextronics, Huawei Group will jointly build this intelligent manufacturing industry park project. According to the project plan, as soon as the third quarter of next year, the new Huawei mobile phone made in Changsha will enter the market.


2. Engineering survey


This project is a renovation and reinforcement project for the standard workshop of Dongwei Industrial Park. It is located in Chigang Road, Wangcheng, Changsha City. It was originally designed as a single five-storey frame building with a height of 22.8m. The foundation form is an independent foundation under the column.


The plant was completed and put into operation in 2015. Due to the modification of the original building function by the current constructor, the project needs to be reformed and strengthened.


The main modifications are as follows:

1. The load on the second floor with 4-10 axes crossing C~R axes is increased from 5.0 kN/m2to 12 kN/m2.

2. The load on the three-storey floor with 4-9 axes crossing A-T axes is increased from 5.0 kN/m2to 12 kN/m2from the original design.

3. One to six storeys, two to four axes intersect R~Q, one to four axes intersect K~L, and one to four axes intersect C~D new ladder.

4. Adding some new equipment to the roof.



According to the current situation of the project and the current national technical specifications and regulations, the reinforcement design of the above renovation is carried out. The main reinforcement methods are enlarged section reinforcement method, bonded FRP composite material reinforcement method, high-performance cement composite mortar reinforcement method and anchorage technology of planting steel bars used with structural reinforcement method.


On April 22, 2018, the renovation project of Dongwei Industrial Park, undertaken by Hunan Xiangqiangsheng Civil Technology Co., Ltd., was officially started, with a total construction period of 40 days and an actual total cost of more than 40 million yuan.


3. Construction technology


1. Post installed anchoring


(1) There should be no local defects in the concrete of the original component in the anchorage part of the planted bars. If there are defects, the reinforcement or reinforcement treatment should be carried out before the planted bars are replanted.


(2) The glue for planting bars must be special glue for supporting bars. It is strictly forbidden to mix bulk glue on site.


(3) The anchorage depth (ls) of planted bars in load-bearing structures should meet the design requirements. It is strictly forbidden to adopt the short-term pull-out test value or the recommended value of manufacturer's technical manual.


(4) When the reinforcement is planted according to the structural requirements, the anchorage depth should be satisfied:

Anchorage of tension steel bar: Max {0.3ls; 10d; 100mm}

Anchorage of compressive steel bar: Max {0.6ls; 10d; 100mm}

The correction factor of 1.5 should be multiplied for cantilever structures and components.


(5) Construction sequence of planting bars: positioning-drilling-gel-planting bars-solidification-pull-out test


Positioning: that is, according to the design requirements of the elastic line, to determine the position of planting bars.


Borehole drilling: In the pre-positioned drilling, the diameter of the hole is 4-6 mm larger than that of the steel bar planted. Mechanical hole-forming shall not affect the surrounding structural components, avoid the main reinforcement of the original structure, and shall not truncate the original stressed reinforcement.


Glue injection: pour in structural glue and use special glue gun to pour in.


Reinforcement: Rotate the required reinforcement into the borehole at a predetermined depth. When planting steel bars, the steel bars should be welded before planting; if there are difficulties, it must be welded later. The weld joint should be more than 15 days away from the concrete surface of the base material, and the root of the planted steel bars should be wrapped with wet towel impregnated with ice water.


Solidification: The process of solidification should not disturb the planted steel bar, and the construction of other processes can be carried out after solidification.



2. Technology of enlarging section of self-compacting concrete


(1) Firstly, the plastering layer or cushion on the surface of components should be chiseled out to the concrete base, and the defective parts of concrete (loose and damaged concrete) should be cleaned up to the solid base. Cracks in concrete should be treated as required, and corrosion of steel bar should be removed and cleaned.


(2) To chisel the concrete at the joint according to the requirements; the edges and corners of the wrapped concrete should be removed. Clean up the oil and slurry on the surface of concrete, and clean up the dust.


(3) Processing and binding of reinforcing bars and setting up of formwork should meet the requirements of specifications.


(4) The mixing and pouring of self-compacting concrete shall be carried out according to the product description. Before pouring, concrete foundation should be fully watered and infiltrated. When mixing concrete, the amount of water added is in accordance with the requirements of the product description. Gas should be guaranteed to escape freely and the pouring density should be guaranteed during the pouring process. Appropriate maintenance measures should be taken after completion of pouring.


(5) Make test blocks according to the requirements of specifications for inspection.


(6) The appearance quality after pouring should conform to the requirements of specifications.


3. Carbon fiber reinforcement


(1) The reinforced part must expose the concrete base, and the concrete surface must be firm, smooth and clean. The surface defect should be repaired by structural glue. The adhesive surface must be polished. The thickness of the surface should be 1-2 m M. After polishing, the smoothness should reach 5 m m/m. Component corner bonding should be polished into a circular arc, the radius of the arc is not less than 20 mm. After surface polishing, the surface dust should be thoroughly removed and the surface of concrete should be kept dry. If the surface water content of concrete is more than 4% before construction, the concrete should be dried. Components with cracks or honeycomb defects should be repaired with epoxy resin.


(2) Construction procedure: first, the adhesive resin is painted; then, when pasting the carbon fiber cloth, the roller is used to roll, and the extruded air bubbles are kept to stick densely. Do not disturb the bonding materials and reinforcement components within 48 hours after the bonding is completed. Rain, sand, dust and acid pollution should be avoided.


(3) When the sheet center line coincides with the beam center line, the deviation shall not be greater than 10 mm and the angle deviation shall not be greater than 5. Carbon fibre materials and original structures must be compact without empty drum.


(4) All kinds of adhesives and structural adhesives should be stored in the ambient temperature prescribed in their specifications, keep away from fire sources and avoid direct sunlight. The operation environment and construction site should keep good ventilation. Smoking and open fire are strictly prohibited in the workplace. All kinds of adhesives should not pollute the source of domestic water. Waste should be treated centrally according to environmental protection requirements.


(5) If serious defects or safety hazards are found in the concealed parts of the original structure or related projects during the reinforcement process, the construction shall be stopped immediately and the design unit shall be notified, and the construction shall be continued only after effective treatment measures have been taken.


(6) Surface protection treatment according to relevant requirements. If it is necessary to protect M20 high-performance crack-resistant mortar with 5 mm thick, sanding treatment should be carried out on the surface coating, and sanding construction should not affect the carbon fibers that have been pasted.


(7) Components strengthened with CFRP bonding method and corresponding parts shall not tear the bonded surface or hit the bonded surface with sharp tools in the future use. It is strictly forbidden to drill or open holes in the reinforcement parts and to disturb the structure destructively. It is strictly forbidden to weld or operate at high temperature in the sticking area in order to avoid the failure of the adhesive layer due to carbonization.


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