Pier reinforcement
Underwater pier strengthening technology

Underwater high static pressure and fatigue stress, water erosion, scour and wear, cavitation, cold region of freezing and thawing and erosion, chemical corrosion and electrochemical corrosion, ship collision, ice and earthquake, the environmental load (such as the biological attachment) and bridge upper structure of the work load and so on, all damage often leads to the formation of a bridge in the underwater structure of various defects, and not easy to found, these injuries, defects results in the decrease of bridge bearing capacity and durability, seriously endangers safety and life of bridge.
Therefore, it is of great significance to study a feasible, fast, convenient and low-cost bridge underwater structure strengthening technology.

A new caissons dry working method is used to reinforce underwater structures

Traditionally, underwater equipment or temporary steel sheet pile cofferdam are required to detect and strengthen the underwater structure of Bridges.
Japan penta-ocean construction company in view of the underwater structure reinforcement problem developed sinking steel box Method reinforcing piers technology (Neo - Dry Repair Method, NDR Method), the technology is in order to obtain Dry part of the implementation of the working environment of the water piers reinforcement and the development of the construction methods, the use of assembled steel caisson, the sinking around and around the bridge pier, set between steel caisson and bridge pier counterforce support deep water pressure resistance, set at the bottom of the steel caisson water stop device, forming a space, and water isolation for Dry reinforcement project to create a work environment,
It can be used to detect, repair and strengthen underwater structures of rivers and ports.

The construction process

(1) in order to prevent pollution of the surrounding rivers, a pollution prevention film shall be set up in the construction area to remove the silt deposited at the foot of the column.
(2) the temporary project shall set up the construction work platform, rely on the existing bridge piers, and set up lifting equipment.
(3) high speed water spraying gun is used for concrete surface treatment to remove the attachments on the pier surface.
(4) anchor holes at the bottom are made of rotary cutting and bending reinforcing steel anchor holes.
(5) flexural reinforcement is set up to inject adhesive for reinforcement fixation into anchor holes and implant flexural reinforcement.
(6) concrete panel prefabrication and assembly production precast concrete panel (produced by prefabrication factory), precast concrete panel is assembled in the site along the surrounding underwater, and the anchor bolt is fixed at the bottom for installation.
(7) no mortar shall be dispersed in the filling water
(8) the construction on the water includes the link of reinforced steel bars on the water, the assembly of precast concrete panel components on the water, the pouring of mortar on the water, and the use of low-shrinkage mortar on the water.
(9) temporary facilities shall be dismantled and strengthened, lifting equipment and other working facilities shall be dismantled, and pollution prevention film shall be removed.
The precast concrete slab is used as the outside formwork of mortar pouring when the precast concrete slab is used in the fast pier reinforcement method. The amount of steel used in the construction of the precast concrete slab is lower than that of the general steel formwork, and the transverse reinforcing steel embedded in the concrete slab can be used to strengthen the bridge pier against earthquake or shear.

Its assembly construction, fast speed, simple process, has the following process characteristics:

1) precast concrete panels with reinforced bars can provide shear strength;
2) bending reinforcement bar is set at the foot of bridge pier column to obtain the effect of bending reinforcement;
3) the transverse steel bar through the middle is used to enhance the ductility of the bridge pier to achieve constraint reinforcement;
4) the use of high durability precast concrete panels, long service life;
5) it is possible to strengthen without drainage, shorten the construction period and reduce the cost.

Introduces and summarizes the new caisson of dry method underwater structure reinforcement technology, among them, the new type of caisson steel caisson method using job created a dry operation environment for underwater structure reinforcement, strengthening work and have land, improve working environment and safety construction quality has a reliable guarantee, however, although the steel caisson reusable, first put into still larger.

Key words: pier reinforcement, bridge reinforcement, old bridge reinforcement