(1) reasons for preloading

Check the safety of supports to ensure construction safety;

Eliminating the influence of foundation inelastic deformation and support inelastic deformation is beneficial to the control of bridge deck alignment.

2 the first generation: ton bag preloading

Advantages: the pressing weight can be guaranteed;

Disadvantages: high cost, poor safety, cumbersome lifting, slow speed, and the ton bag can be reused up to 5 times;

Scope of application: no water, small volume, convenient sand taking.

3 second generation: Precast concrete

Advantages: the pressing weight can be guaranteed;

Disadvantages: high cost, good safety, cumbersome transportation and high reuse rate;

Advantages of the fourth generation: safety, convenience and low cost;

Disadvantages: unable to reach the design preloading weight;

Scope of application: rich water source and difficult lifting.

Fourth generation: open water bag (Wuhan suanda company leads the marketization)

Advantages: safe, convenient and low cost;

Disadvantages: unable to reach the design preloading weight;

Scope of application: rich water source and difficult lifting.

Fifth generation: Reinforced PVC water bag (invented by Wuhan suanda company)

Advantages: safe, convenient and low cost;

Disadvantages: construction personnel need a strong sense of responsibility;

Scope of application: abundant water source.

Sixth generation: rubber water bag