Components of the haunch prestressed concrete i beam and txgirder haunch design guide
Rev November Prestressed Concrete I-Beam and TxGirder Haunch Design Guide Components of the Haunch x Camber Camber is the upward de ection in the beam after release of the prestressing strands due to the eccentricity of the force in the strands The camber of the beam is usually the largest contribution to haunch As camber increases so does haunch Figure Camber of Beam Before Slab is Placed x Dead Load De ection The dead load de ection used in haunch calculations is the de ection due to the dead load of the slab only The dead load helps lessen the haunch As the dead load de ection increases the haunch decreases Note The dead load de ection calculated is for a cast-in-place slab Where prestressed concrete panels are used de ections used to screed the roadway surface will be di ?erent since the de ection due to the panels will already be there Figure Beam After Slab is Placed x Cross Slope The cross slope is the slope of the slab across the transverse section of the beam The cross slope correction CSC is the distance from the bottom of the slab to the top of the beam at the center of the top ange needed to prevent encroachment of the beam into the slab at the lowest point of the cross slope The CSC is needed for I-beams since the beams are placed vertically on the bearing pads As CSC increases the haunch also increases of CRev November Figure Cross Slope Correction x Vertical Clearance Ordinate VCO The VCO is the distance from the BGS reference line to the roadway surface The reference line is the chorded roadway surface between center of bearings The VCO is given in the BGS output as negative when the roadway surface is above the reference line and positive below the reference line When the VCO is negative crest curve the haunch decreases at center of bearing and when the VCO is positive sag curve the haunch increases at center of bearing Figure VCO with Respect to BGS Reference Line Figure All Haunch Components Working Together Minimum and Maximum Haunch Values For I-beams o The maximum haunch without reinforcing is ? o The minimum haunch at the center of bearing is ? for I-Beams to ensure there is haunch concrete under the prestressed concrete panels of CRev November o The minimum haunch at midspan is ? to accommodate bedding strips for prestressed concrete panels For TxGirders o The maximum haunch without reinforcing is ? o The minimum haunch at the center of bearing is ? to accommodate the thickened slab end since the TxGirder ange is too thin to notch like the I-beam o The minimum haunch at midspan is ? to accommodate bedding strips for prestressed concrete panels Steps to Calculating Haunch x Step Execute a preliminary BGS run using a beam framing option from - in the FOPT card On the BRNG card input a ??Depth Below the Reference Line ? or
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