Five Key Points of Highway Bridge Structure Design (II)

2. Strengthening structural reinforcement:

 

Any damage and destruction of the concrete structure is generally the first crack in the concrete, cracks are a barometer reflecting the concrete structure disease, in turn, the presence of cracks will increase the permeability of concrete, providing a channel to make the erosion damage gradually escalate, concrete durability declining. When the concrete is cracked, the rate of erosion will be greatly accelerated, forming a vicious circle leading to further degradation of the durability of the concrete structure. Therefore, it is important to prevent and control cracks in concrete to improve the durability of concrete structures.

 

 

Control of concrete cracks, in addition to the normal use of the limit state in accordance with the requirements of the code to control the working cracks, it is more important to take structural measures to control the construction and use of concrete process a large number of non-working cracks. The “Bridge JTGD62″ highlights the strengthening of horizontal anti-shrinkage reinforcement and hoop reinforcement in the control of cracks, improve the horizontal anti-shrinkage reinforcement rate and hoop spacing provisions, its indicators are improved than the old bridge regulation, which is to prevent and control shrinkage cracks in the important structural measures.

3. Improve the quality of post-tensioning prestressing steel pipe compression:

The quality of post-tensioned prestressed steel pipe compression slurry is one of the key factors affecting the durability of prestressed concrete sorghum. The “Bridge JTGD62″ stipulates that the compressive strength of cement slurry for prestressing steel pipe compression slurry should not be less than 30MPa, and its water-cement ratio is 0.4~0.5. In order to reduce shrinkage, it can also be mixed with appropriate amount of expander by test The Guide for Durability Design and Construction of Concrete Structures. CCESO1-2004 believes that corrosion of prestressing steel bars can lead to structural sudden damage, which is not easily detected beforehand and must be given special attention in durability design and multiple means of protection. In this regard, for prestressed concrete structures that may suffer from chloride salt erosion, steel components such as prestressing tendons, anchors and connectors should be epoxy coated or zinc coated, and the pipes of post-tensioned prestressing system must have sealing performance, and instead of using metal spiral pipes, it is advisable to use high-density plastic waveform pipes with good sealing performance. Meanwhile, the pipe grouting materials and grouting methods should be verified by tests in advance to reduce the pores formed after the slurry hardens as much as possible, and vacuum grouting should be used, and an appropriate amount of rust inhibitor can be mixed into the grouting materials if necessary.

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