PRESENTED BYM.GURU MURTHY0109111-01UNDER ESTEEMED GUIDANCE OF Dr.R.RAMESH REDDY,Professor, University College of Engineering, Osmania University ,Hyderabad.

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At one time, bridges on curved alignments were rare. However, times have changed and modern highway bridges and traffic separation structures are commonly built on a horizontal curve.

higher traffic volumes and speeds, geometric constraints of the urban environment, and improved structural forms that lend themselves to curved construction.

It is likely that the use of curved structures is going to increase, and that the geometries of some of these structures will continue to push the envelope with respect to the degree of curvature, span lengths and depths, the amount of required prestressing force, etc., it is evident that better guidelines are required for their design.

The box girder is an efficient form of construction for bridges because it minimizes weight, while maximizing flexural stiffness and capacity.Box girders offer better resistance to torsion, which is particularly benefit, if the bridge deck is curved in plan.Commonly used for highway flyovers.

*OutlineDevelop three-dimensional models of curved box girders using the computer program "STAAD PRO". Geometrical DetailsModelingAnalysisResults Interpretation

*Problem Reinforced Concrete Box Girder DeckGeometrical Details: Span : 30.00 m Simply Supported Condition, Single cell box girder Breadth : 12.00 m Depth : 1.80 m Curvature 0o, 10o, 20o, 30o, 40o

STAAD Pro. software is used

*1. Essentially a computer aided method for analysis of bridge decks.2. The method is applicable to bridge decks with simple as well as complex configuration with almost ease and confidence.3. The method is easy to comprehend and use.4. The analysis is relatively in expensive and proved to be reliably accurate for a variety of bridges.5. The grillage representation helps in giving the designer a feel of structural behavior of the bridge and the manner in which loading is distributed and eventually taken to the supports.

*The deck is idealized as a series of beam elements (or grillages), connected and restrained at their joints.Each element is given an equivalent bending and torsional inertia to represent the portion of the deck which it replaces.Bending and torsional stiffness in every region of slab are assumed to be concentrated in nearest equivalent grillage beam.Slab longitudinal stiffness are concentrated in longitudinal beams; transverse stiffness in transverse beams.

*When a bridge deck is analyzed by the method of Grillage Analogy, there are essentially five steps to be followed for obtaining design responses :Idealization of physical deck into equivalent grillageEvaluation of equivalent elastic inertia of members of grillageApplication and transfer of loads to various nodes of grillageDetermination of force responses and design envelopes andInterpretation of results.

* Bridge Deck Idealized Model (Deflected)

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Conclusions:

Based on the results generated by STAAD pro analysis the following conclusions were made: 1) Bending Moment in Box girder vary significantly with the location of the loadsLoad placed in Left Eccentricity Bending Moment in Outer Web greater than the Middle and Inner Web Load placed in Zero Eccentricity Bending Moment in Middle Web greater than the inner and Outer WebLoad placed in Right Eccentricity Bending Moment in Inner Web greater than the middle and Outer Web

= 10 = 20 = 30 = 40Shea Force (Fy) in KN454.13466.35478.75491.64Max. Bending Moment (Mz) in KN-m-2240.2-2285.74-2342.53-2411.97Max.Torsion (Mx) in KN-m549.79644.53743.6848.45Deflection (y) in mm4.134.605.165.87Rotations in radians0000

Whole Structure - Max bending moment (Mz) 2285.74 KN-m

*2)In all the loading condition all the webs it is phenomenally observe that Maximum Bending Moment highest in Outer Web (Cur-40)left eccentricity compare to Inner and Outer Web in Right and Zero Eccentricity3)Bending Moment increases with angle of curvature increases in Inner, Middle and Outer Web in the case of Left Eccentricity and Zero Eccentricity But in the case of Right Eccentricity curvature increases Bending Moment decreases in Inner, Middle and Outer Web

*Curvature increases Shear Force increases in Outer and Middle web but decreased in Inner Web when load placed in Left Eccentricity, Zero Eccentricity and Right Eccentricity Shear Force also changes w.r.t. to load positions when load placed eccentricity outer web get maximum Shear Force similarly when load placed in Right Eccentricity inner web greater SF then middle and outer webs

Figure 4.4 Whole Structure -Max Shear force( Fy) 466.352 KN

*Torsion values will be more in middle web compare to inner and outer web in all curvatureCurvature increases Torsion increases in Inner ,Middle and Outer webBut in Right Eccentricity curvature increases torsion decreases in Inner, Middle and Outer web

Whole Structure Mx 644.529 KN-m For Load Case20

*Curvature increases Displacement increases in Inner ,Middle and Outer webs in Left Eccentricity Zero EccentricityIn Right Eccentricity curvature increases. Displacement increases in Outer, Middle web Displacement decrease

Figure 4.5 Whole Structure Displacements (4.595mm at Node No.9 )

*The box girder is modeled and analyzed using the STAAD Pro. Software, this work also be done using other software like SAP, NISA and Ansys.Project is done on the simply supported case, same Box girder can be analyzed for continuous spans.The loading used in the present work is 70R Wheel load, there is a scope work future work to carry the analysis other type of loads and their combinations.

*References:C. S. Surana & R. Agarwal, Grillage Analogy in Bridge Deck Analysis, Narosa publishing House New Delhi.Edmund c. Hambly, Bridge Deck Behavior, first edition, Champman and Hall , John Wiley & sons, inc., New York 1976.Standard Specifications and Code of practice for Road Bridges, IRC: 6-2000, IRC8-2000.Heinere Ah Sha, Literature Review and Current Knowledge Horizontally Curved BridgesFrom GOOGLE search, Grillage method of analysis for designing a beam and slab type deck.From GOOGLE search Question re live load Distribution factors in AASTHO-LRFD.Effect of Girder spacing on Bridge Deck response, Peter J. Massarelli, Virginia Transportation Research Council, Charlottesville, Virginia.Bridge Deck Analysis, by Eugene J.OBrien and Damien L.Keogh Department of Civil Engineering, University College Dublin, Ireland.V.K.Raina, Concrete Bridge Practice: Analysis, Design and EconomicsA. R. cussens and R. P. Pama, Bridge Deck Analysis, John Wiley, 1975.Khaled M, Sennah M and John B Kennedy, Load Distribution Factors for Composite Multicell Box Girder Bridges, Journal of Bridge Engieering.

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