pst box girder bridge

PRESENTATION ON SUMMER TRAINING

BOX GIRDER BRIDGE

Presented by: Waseem sajad

BRIDGE: A bridge is a structure providing passage over an

obstacle without closing the way beneath.

Girder: A girder is a support beam used in construction. It is

the main horizontal support of a structure which supports smaller beams,

Box Girder Bridge:A box girder bridge is a bridge in which the main

beams comprise girder in the shape of a hollow box. The box girder normally comprises either prestress concrete, structural steel or a composite of steel and reinforced concrete. The box is typically rectangular or trapezoidal in cross-section.

Bridge type: - Box Girder Bridge.Total length = 265m.No. of spans = 5.No. of Piers = 4.Length of each span = 53m.Total width of deck = 12m.Carriageway width = 7.5m (2 lane)Footpath = 1.5m on each side of carriageway.Concrete Mix used = M15 (PCC) M50 (for Piers) M45 (for box

girder) M40 (for

abutments).

PIERS:PIER:

Foundation.

Length of pier cap = 5.5 m. (at top perpendicular to the direction of traffic) 2.65 m. (at bottom perpendicular to the direction of traffic)

Width of pier cap = 3.45 m. Total height of pier cap = 1.5 m. C/C of bearings = 4.3 m. (perpendicular to the direction of traffic) 2.25 m. (along direction of traffic)

Total width of deck slab = 12m.Carriageway width = 7.5m (2 lane)Footpath = 1.5m on each side of carriageway•Bottom flange:-Thickness = 450 mm.Width = 6.5 m.•Web:-Thickness = 500 mm (near supports) 300 mm (at mid span)•Deck slab:-Thickness = 400 mm. (near web)250 mm (at center line)300 mm – 200 mm (for cantilever portion, footpath)•Belister Block : -It is provided when cross-sectional area of box girder is not enough to provide sufficient no of profiles for prestressing, then additional required profiles are provided in Belister Block

ABUTMENT:

POST TENSIONING?

Post tensioning is a method of prestressing in which stressing of member/structure is done after the casting of concrete is done and it set into a hardened mass.

MIX DESIGN:-  M-45 (Mix) 53 grade cement:-For 1 m3 of MixAggregate 20 mm. = 620 kg. 10 mm. = 623 kg.Sand = 630 kg.Cement = 479 kg.Water = 167 kg.Admixture = 5100g. M-40 (Mix) 43 grade cement:-For 1 m3 of MixAggregate 20 mm. = 620.45 kg. 10 mm. = 620.45 kg.Sand = 549.13 kg.Cement = 479 kg.Water = 167.45 kg.Admixture = 5148g. 

Admixture used: WRA admixtureSuper plasticizing admixtureSulphonated Napthaline

POST TENSIONING

MATERIALS USED BEFORE CASTING

Duct pipes. spring shape helix made of reinforcing bar.

HYSD strands.Guide Cone.

EQUIPMENTS TO BE USED FOR TENSIONING

Bearings.Wedges (Master Grips).

Star Plate.Anchor Block.Collar.

Jack.Hydraulic Pump.Crane/Chain pulley Mechanism.Aluminum/Steel pipes of suitable diametre.

PROCEDURE:-

Place the duct pipes at designed position in smooth curves between the reinforcement with guide cones with helical spring made up of reinforcing bar at both ends of duct pipes and Insert designed no. of cables (HYSD strands) in duct pipes and cast the member. After designed no. of days stressing (tensioning) is done.

Clean all the cables with suitable solvent (petrol) and adjust bearing over cables at both ends.

Apply wax over wedges and grip them over cables to fix cables with bearings.

Fit the collar over bearing and adjust star plate on combination of collar and bearing.

Apply jack on above made combination then fit anchor block inside the jack.

Connect the jack to hydraulic pump and stress the cables.

GROUTING:

RELEASING OF STRESS FROM STRESSED STRANDS IN CASE SOME DAMAGE OR SOME OTHER MISHAPPENING.

THANK YOU