The method of improving stiffness at the inner support in the steel box girder.

  Because the construction work of existing steel box composite girder bridge is faster than the other method, it has been widely constructed in the inside and outside of the country.
Because of grate the torsion, that has many advantage for the curve bridge but has comparative big section, noise and vibration.

  Steel box composite gird bridge by concrete-fill and lifting support method.

  Because the construction work of existing steel box composite girder bridge is quick  than the other method, it has widely constructed in the inside and outside of the country. Because of grate the torsion, that has many advantage for the curve bridge but has comparative big section, noise and vibration. There are so different between maximum magnitude of positive moment and negative moment. The section choice of bridge whole length is non economic and because   the floor slab's section is large, neutrality axis give way to the upper part. So the upper and lower stress of steel not be in balance. The other a fault of previous steel box girder bridge is extension that happened at inner support part by additional dead and live load. Therefore it becomes  not composite section, floor slab is cracked and   stiffness  is declined. Fault at welding area is due to the shear flow's disturbance by changing top and bottom flange thick into various shape.

  Steel box composite gird bridge by concrete-fill and lifting support method.
(The new method No.270 appointed by MOCT [Ministry of Construction& Transportation])
(Patent a public notice  Number. 10-1999-007688)

 This method's purpose is improving stiffness necessary to negative moment area by shear connector installed and casting concrete on the bottom of the negative moment area of the steel box to steel box girder.Otherwise,  improving stiffness necessary for taking off tension force when design load applied by using the up-down method, compressive stress installed on the negative moment area of upside of deck plate concrete. This method is more extend a span of bridge than existed steel box bridge and case of making a variety section of the positive-negative moment area, most extend a span of bridge.Otherwise prevent a decay in the steel box by  being installed concrete at the bottom of the negative moment area and obtain effect that absorbed noise or shake.And This method can reduce a fault of welding area by changing top and bottom flange thick into relatively simple.

 The method of improving stiffness at the inner support in the steel box girder.

  45m 2 span continuous  bridge 's section property and  comparison in the amount of materials

  Reduced effect of steel materials.
    flange's thickness and hight's simultaneous reduction and maximum curtailment of  steel

  existing steel box gird bridge's section  property
    steel : SM490
    concrete : The floor plate - 270 Kg/§²

  The main position's section

  The variation of flange

 The method of improving stiffness at the inner support in the steel box girder.

  The effect of reduction on girder height

 flange's thickness and hight's simultaneous reduction and maximum curtailment   of  girder height

The main position's section
 

The section and the amount of materials's comparison
 

    3.5% reduction of steel amount¡ægirder height 10% reduction(220cm¡æ198cm) 

 The method of improving stiffness at the inner support in the steel box girder.

  40m-50m-40m45m 3 span continuous bridge's section property and     comparison in the amount of materials

  Reduced effect of steel materials.

 Flange's thickness and hight's simultaneous reduction and maximum      curtailment of  steel amount

  existing steel box gird bridge's section  property
   steel : SM 490
   concrete : floor plate 270 Kg/§²

  The main position's section

  The variation of flange

 The method of improving stiffness at the inner support in the steel box girder.

  improved steel box gird bridge's section  property
  steel : SM490
  concrete : The floor plate - 270 Kg/§² casting concrete :-400 Kg/§²

  The main position's section

  The variation of flange

  The section and the amount of materials's comparison

    girder height 6% reduction  a condition ¡æ14.9% reduction of steel amount

 The method of improving stiffness at the inner support in the steel box girder.

  The effect of reduction on girder height

 flange's thickness and hight's simultaneous reduction and maximum curtailment   of  girder height

The main position's section
 

The section and the amount of materials's comparison
 

    4.6% reduction of steel amount¡ægirder height 15% reduction(200cm¡æ170cm)

 The method of improving stiffness at the inner support in the steel box girder.

  The example of design

  2@65m 2 span continuous bridge

  The main position's section

  The variation of flange

  a reference

  In the case flange width of section presented in the example of design is 3m ,   extensible maximum span length is possible to 75m.

 The method of improving stiffness at the inner support in the steel box girder.

  65m-75m-65m 3 span continuous bridge

  The main position's section

  The variation of flange

  a reference

  In the case flange width of section presented in the example of design is 3m ,   extensible maximum span length is possible to 75m.

 The method of improving stiffness at the inner support in the steel box girder.

  The process of construction work in 3span continuous bridge

  1?is lifting-up support, 2?is lifting-down support, 3?points slab concrete and
4?indicates concrete that is cast in lower part of the steel box girder at the range
of negative moment.
 

 The method of improving stiffness at the inner support in the steel box girder.

  simple-multi span steel box girder bridge for rahmen by Down-up.(patent a public notice  Number. 10-2000-058716)

 This method in simple pan composite girder construct is treated as fixed-moved support and it has fall-rise moved support It have introduce compressing stress on the floor slab concrete of negative moment area and the lower flange of positive moment in fixed support. The method of construct in multi-span composite girder structure have fall-rise a pier part support of both ends. It have the floor slab con'c of inner support and the lower flange of positive moment area introduce compressing stress. Because moment in fixed support is distributed at a bridge pier, share about external force of beam is reduced. So girder height and span can expect reduction and extension effect about 20%. Moreover, Parapet wall of one side abutment in fixed support and floor slab con'c places as one body therefore expansion joint and lower part can realize excellent effect and it has considerable aseismicity. In the multi-span case, because support's falling and rising work is  accomplished  in a bridge pier, work's convenience and safety being superior by  far. And it can remove construction joint's occurrence by simultaneous placing  of  floor slab con'c. 

 This method in simple-span can happen big moment in fixed support. First it has buried H-steel and after welding of connection plate for steel box the lower part flange's connection on the upside, it has connect completely by lower part flange and bolt or welding. Here, at bridge seat and parapet wall take out bar in advance. Including the upper part floor slab, bridge seat, parapet wall and steel box girder's web also lower part flange is placed the same time. So it can do part of complete fixed support. Steel box girder is reinforced by install of stiffener. Not only the upper flange steel girder but web install the stud, there it has greatly improved the con'c composite effect.

 The method of improving stiffness at the inner support in the steel box girder.

  2span continuous steel box gird composition bridge

 The method of improving stiffness at the inner support in the steel box girder.

  The process of construction work in 3span continuous steel box gird composition bridge