The construction method of continuous preflex bridge with a lighting up-down support

 

 A basic concept is to devisionally manufacture preflex beams according to span , in order to continue preflex composite beams, that is, when preplex composite beams are designed, the area of positive moment is similarly manufactured with simple preflex composite beam. But in the area of negative moment, a inner support is lifted up and bottom slab is placed, later a inner support is lifted down. this purpose is to introduce compressive stress in order to cancel  a tensive stress by a dead and live load.

 The merits of this method follow;

 It has no expansion joint. This method is economical.Because a material, self-load and construction time can be reduced.

 

Fig. 1 Structural diagram of 2 spans simple preplex bridge

 

Fig. 2  Structural diagram of 2 spans continuous preplex bridge

 

 

 

Construction method of 2 spans continuous preflex composite beam

 

Step1

Placing beams

Step 2

Loading of preflexion

Step 3

Placing concrete at lower flange and unloading

Step 4

Movement of a second support

Step 5

The lifting up a connected support

Step 6

The placing concrete of bottom and web at inner support

 

Step 7

The lifting down a connected support

Step 8

The placing concrete of bottom and web at positive moment area and of lower flange at negative moment area

Step 9

Paving a bridge with asphalt

 

Construction method of 3 spans continuous preflex composite beam

 

 

Step 1

Placing beams

Step 2

Loading of preflexion

Step 3

Placing concrete at lower flange and unloading

Step 4

Movement of a second support

Step 5

The lifting up a connected first support

Step 6

The placing concrete of bottom and web at inner first support

 

Step 7

The lifting down a connected first support

Step 8

The lifting up a connected second support

Step 9

The placing concrete of bottom and web at inner second support

Step 10

The lifting down a connected second support

Step 11

The placing concrete at all of positive moment areas

Step 12

Paving a bridge with asphalt