Studyonthe behaviorof box girder bridge

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/277715074 Study on the Behavior of Box Girder Bridge Thesis · January 2010 DOI: 10.13140/RG.2.1.2747.6641 CITATIONS READS 1,607 4 authors, including: Sri Kalyana Rama J BITS Pilani, Hyderabad 21 PUBLICATIONS 4 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Comparative Study on the Lateral Load Resistance of Multi-Storied Structure with Bracing Systems View project All content following this page was uploaded by Sri Kalyana Rama J on 05 June 2015 The user has requested enhancement of the downloaded file STUDY AND BEHAVIOUR OF BOX GIRDER BRIDGE A Project Report Submitted to Nagarjuna University In Partial fulfillment of the Requirements for the Award of the Degree of BACHELOR OF TECHNOLOGY with specialization in CIVIL ENGINEERING Submitted By: J.S.KALYANA RAMA (Y06CE050) V.R.RAGHAVA SUDHIR V.SAMPATH KUMAR (Y06CE039) (Y06CE044) V.VICKRANTH (Y06CE060) Under the Guidance of V.RAMESH, Asst Professor & Special Thanks to N.R.K.MURTHY, HEAD OF THE DEPARTMENT DEPARTMENT OF CIVIL ENGINEERING V.R.SIDDHARTHA ENGINEERING COLLEGE KANURU, VIJAYAWADA-520007 -I- APRIL -2010 STUDY AND BEHAVIOUR OF BOX GIRDER BRIDGE DEPARTMENT OF CIVIL ENGINEERING V.R.SIDDHARTHA ENGINEERING COLLEGE KANURU, VIJAYAWADA-520007 CERTIFICATE This is to certify that the project report entitled “STUDY AND BEHAVIOUR OF BOX GIRDER BRIDGE” is the bona fide work done by J.S.KALYANA RAMA Y06CE050 V.R.RAGHAVA SUDHIR Y06CE039 V.SAMPATH KUMAR Y06CE044 V.VICKRANTH Y06CE060 Under guidance and supervision of V.RAMESH, Asst.Professor, submitted in partial fulfillment of the requirements for the award of the Degree of Bachelor of Technology, in Civil Engineering by the Acharya Nagarjuna University (V.RAMESH) (Dr N.R.K MURTHY) GUIDE: HEAD OF THE DEPARTMENT Date Date: - II - ACKNOWLEDGEMENTS We take this opportunity first to express our deep sense of gratitude and gratefulness to our project guide, V.RAMESH, Asst.Professor, Department of Civil Engineering for his expert guidance, constant encouragement and support during all phases of our work We would also like to thank N.R.K.MURTHY, Professor, Department of Civil Engineering, D Y NARASIMHA RAO, Senior Engineer, Bridges and B SRIKANTH, Design Engineer, S.C.R Secunderabad for their valuable suggestions and encouragement in the successful completion of this Report We would also like to thank Dr N.R.K MURTHY, Professor and Head, Department of Civil Engineering for his cooperation in providing facilities for the successful completion of this Report We would also like to thank Dr.K.MOHAN RAO, Principal,V.R.SIDDHARTHA ENGINEERING COLLEGE for providing the state of the art facilities in the college We also take this opportunity to thank everyone who helped either directly or indirectly in bringing out the project report to the final form PROJECT ASSOCIATES: J.S.KALYANA RAMA (Y06CE050) V.R.RAGHAVA SUDHIR (Y06CE039) V.SAMPATH KUMAR (Y06CE044) V.VICKRANTH - III - (Y06CE060) ABSTRACT “When tension flanges of longitudinal girders are connected together, the resulting structure is called a box girder bridge” The behavior of box girder section for a general case of an eccentric load has been studied and presented its studies in chapter An encompassing review of literature has been made regarding construction and a summary of general specifications with reference to IRC:18 have been discussed in chapter Box girders can be universally applied from the point of view of load carrying, to their indifference as to whether the bending moments are positive or negative and to their torsional stiffness; from the point of view of economy An ongoing work has been taken as a case study for the present work Analysis principles for torsion and distortion effects are applied to the section selected, and found satisfactory Correspondingly, the problem has been analyzed and designed for flexure and shear by giving due considerations for torsional and distortional effects as a precautionary measure - IV - TABLE OF CONTENTS CERTIFICATE ACKNOWLEDGEMENTS ABSTRACT CONTENTS PAGE.NO INTRODUCTION TO BOX GIRDER BRIDGES Introduction Historical development Evolution Advantages Disadvantages Specifications BEHAVIOUR OF BOX GIRDER Flexure Torsion 10 Distortion 16 Warping of Cross section 18 Shear lag 19 Diaphragms 22 CONSTRUCTION AND GENERAL ARRANGEMENT 24 General Arrangement 25 Cast-in-situ Construction 26 Construction of Multi-cell -V- Box Girder 29 ANALYSIS OF BOX GIRDER BRIDGE 32 (CASE STUDY) Torsional Analysis 33 Distortional Analysis Beam On Elastic Foundation 35 DESIGN OF BOX GIRDER 39 Description 41 Span arrangement 41 Prestress 41 Design Data 42 Sectional properties 44 Bending Moment And Shear Force Calculations 45 Tabulation of Bending Moment And Shear Forces 49 Prestressing forces and other losses Calculations 51 Prestress in service condition 54 Shear force calculations 54 Design for shear 57 Design of Elastomeric Bearing 58 Deflection Calculations 62 Elongation Statement 63 - VI - Check for ultimate moment of Resistance 64 Design of Deck Slab 65 Design of cantilever deck slab beyond end diaphragms 68 Design of cantilever deck slab below Footpath 69 Provision of untensioned mild steel Reinforcement 71 Design of Intermediate Diaphragms 73 End diaphragms 76 Design of End block 77 CASE STUDY PICTURES 79 CONCLUSIONS 86 CONCLUSION AND FUTURE WORK 87 REFERENCES 88 - VII - CHAPTER INTRODUCTION -1- Introduction The continuing expansion of highway network throughout the world is largely the result of great increase in traffic, population and extensive growth of metropolitan urban areas This expansion has lead to many changes in the use and development of various kinds of bridges The bridge type is related to providing maximum efficiency of use of material and construction technique, for particular span, and applications As Span increases, dead load is an important increasing factor To reduce the dead load, unnecessary material, which is not utilized to its full capacity, is removed out of section, this Results in the shape of box girder or cellular structures, depending upon whether the shear deformations can be neglected or not Span range is more for box bridge girder as compare to T-beam Girder Bridge resulting in comparatively lesser number of piers for the same valley width and hence results in economy A box girder is formed when two web plates are joined by a common flange at both the top and the bottom The closed cell which is formed has a much greater torsional stiffness and strength than an open section and it is this feature which is the usual reason for choosing a box girder configuration Box girders are rarely used in buildings (box columns are sometimes used but these are axially loaded rather than in loaded in bending) They may be used in special circumstances, such as when loads are carried eccentrically to the beam axis “When tension flanges of longitudinal girders are connected together, the resulting structure is called a box girder bridge” Box girders can be universally applied from the point of view of load carrying, to their indifference as to whether the bending moments are positive or negative and to their torsional stiffness; from the point of view of economy -2- mm It therefore means that the diaphragms of 585 mm depth is spanning over 1200 mm, as a fixed beam Width of opening / span = 1.20 m Depth above opening = 585 mm Bending moment due to slab load = WL2 /12 = 2.92 KN/m Self weight of cross beam / diaphragm = 4.4 BM due to self weight of diaphragm = 0.05 KN-m Hence total dead load moment = 3.45 KN/m KN-m EFFECT OF LIVE LOAD “Class AA” (tracked) load placed directly over the diaphragm gives the maximum reaction and hence causes the maximum bending moment Fig:5-12 Load Transferred to diaphragm = 285.38 KN Therefore, with 25% impact = 356.73 KN As the width of opening is 1200 mm, only one track will come over opening and when the track is placed exactly in center (Across the width) maximum moments are obtained Co-efficient CAB for FEM = 0.125 x (1-a2/3) x W = 3.714 = 44.568 SUPPORT MOMENT Therefore, BM at A = CAB x L - 74 - KN-m (-ve bending moment near support) Total moment at A = 48.01 KN-m Depth required = 262.60 mm Overall depth available = 585.00 mm Effective depth = 535.00 mm Reinforcement required = 521.78 mm2 Using 20 mm dia bars No of bars required = 1.66 Nos Provide Nos TOR 20 mm bars at top as shown in the drawing SPAN MOMENT : Fig:5-13 Mc = 69.12 KN-m Net bending moment at mid span = 69.12 KN-m Dead load moment in span = 3.45 KN-m Net design BM in span = 72.57 KN-m Reinforcement required = 788.59 mm2 Using 20 mm dia bars No of bars required = 2.51 Nos Provide Nos TOR 20 mm bars at bottom as shown in the drawing DESIGN OF SHEAR : Shear Force (Live load) = 17.84 Dead load / Self weight shear force = 2.63 Total Design shear force = 181.00 KN - 75 - KN Shear stress = V/bxd = 1.21 < 2.50Mpa Maximum permissible shear stress for M40 grade of concrete is 2.50 Mpa as per IRC 21-2000 table –12A Shear Resistance of Concrete assumed as 20% Using 12 mm dia legged stirrups spacing required Sv = 156.08 mm Provide 12 mm dia @ 150 mm c/c 5.21 END DIAPHRAGM The end diaphragm has a thickness of 450 mm The load transferred from “ class AA” tracked Vehicle on end diaphragm will be much less, as compared to the intermediate diaphragm, however same reinforcement will be provided in the end diaphragms also Design for end diaphragm for lifting condition: In the event of replacement of Elastomeric bearings, it becomes necessary to lift the superstructure from its supports and accordingly suitable locations for placement of Hydraulic jacks for lifting the superstructure from over the bed blocks are marked in the sketch below This arrangement for lifting of superstructure induces bending moment and shear forces in the end diaphragms of the PSC superstructure for which suitable reinforcement will be provided as calculated below Fig:5-14 - 76 - Total Weight of half span of superstructure = 2507.8 KN Dead load reaction per bearing = C/c Distance between bearing and jack position = 0.625 m Maximum hogging moment 522.45 KN-m = 835.92 KN Depth required = 816.85 mm Overall depth available = 2000.00 Effective depth = 1950.00 mm Reinforcement required = 1483.52 mm2 Using 20 mm dia bars No of bars required Provide Nos, TOR 20 mm bars at top as shown in the drawing SHEAR Maximum shear force ( cantilever span) = 835.92 KN Shear Stress = 0.95 < 2.50 Mpa = V/bxd Maximum permissible shear stress for M40 grade of concrete is 2.50 Mpa as per IRC 21-2000 table –12A Assuring 20% shear resistance due to concrete Using 12 mm dia legged stirrups spacing required Sv = 227.10 mm Provide 12 mm dia @ 200 mm c/c 5.22 DESIGN OF END BLOCK BEARING STRESS BEHIND ANCHORAGES : (Clause 7.3) The maximum allowable bearing stress, immediately behind the anchorages is given by Fb = 0.48 fcj  (A2/A1) or 0.8 fcj whichever is smaller A1 = bearing area of anchorage ( 27 x 27) A2 = Area of concrete within member without overlapping (40 x 40) fcj = Concrete strength at the time of stressing Where The strength of concrete at the time of stressing shall not be less than - 77 - = 34600.0 KN/ m2 fb = Permissible bearing stress behind anchorage = 0.48 Fcj  (A2/A1) = 24604.4 KN/m2 or 0.80 Fcj = 27680 KN/m2 Maximum force in the cable after blocking = 145.00 Cable force after instantaneous losses = 0.00 (Elastic shortening, relaxation of steel, and seating of anchorage) = 145.00 Therefore, Bearinig pressure immediately behind the anchorages = 19890.3 KN/m2 < 24604 KN/m2 - 78 - CHAPTER CASE STUDY PICTURES - 79 - Fig: 6-1 STAGING OF PROPOSED BOX GIRDER BRIDGE OF SPAN 21mts Fig: 6-2 FRONT ELEVATION OF BOX GIRDER - 80 - Fig: 6-3 END DIAPHRAGM Fig: 6-4 ELASTOMERIC BEARING - 81 - Fig: 6-5 SPAN SHOWING SOFFIT SLAB IN BEARING LEVEL Fig: 6-6 PIER, BED BLOCK & BOXGIRDER - 82 - Fig: 6-7INTERMEDIATE DIAPHRAGM Fig: 6-8 PRESTRESSING CABLE IN LONGITUDINAL GIRDER - 83 - Fig: 6-9 PRESTRESSING CABLE IN SOFFIT SLAB Fig: 6-10 HYDRAULIC JACK OUTER DIAMETER - 84 - Fig: 6-11 CABLE LOCATED IN JACK Fig: 6-12 POST-TENSSIONING CABLE BY HYDRAULIC JACK - 85 - CHAPTER CONCLUSION - 86 - CONCLUSION AND FUTURE WORK An approximate method adopted in the box girder bridge design has been taken as a case study It revealed that the final stresses in concrete at transfer and service load stages very nominal when compared with allowable stresses But the factor of safety when checked against ultimate loads is only 2.0, and the box section selected when checked for torsional and distortional effects is found satisfactory A further study is sought in these respects for optimum usage of material strengths using software packages available is suggested - 87 - CHAPTER REFERENCES:  Strength of Materials- A Practical Approach by D.S.Prakash Rao  Bridge Superstructures by N.Rajagopalan  Concrete Box Girder Bridges by Jorg Schlaich and Hartmut Scheef  The Design of Prestressed Concrete Bridges by Robert Benaim  M.C.Tandon “Box Girders subjected to Torsion”, Indian Concrete Journal, February 1976  Koll Brunner C.F and Busler K ,”Torsion in structure” 1969 edition  Design of Bridges By N.Krishnaraju  IRC codes 5,6,18,21,22,78,83(part II)  IS CODES 456-2000, 1343 - 88 View publication stats