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SNS COLLEGE OF ENGINEERING

SNS COLLEGE OF ENGINEERING. RESEARCH SEMINAR PRESENTATION 18.01.14 Dr.D.Vijayalakshmi . Professor & Head Department Of Civil Engg. Research is: Search for knowledge Scientific invention Movement from known to unknown Voyage of discovery. Research is

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SNS COLLEGE OF ENGINEERING

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  1. SNS COLLEGE OF ENGINEERING RESEARCH SEMINAR PRESENTATION 18.01.14 Dr.D.Vijayalakshmi. Professor & Head Department Of Civil Engg

  2. Research is: • Search for knowledge • Scientific invention • Movement from known to unknown • Voyage of discovery. Research is • defining and redefining problems • formulating hypothesis or suggested solutions • collecting, organizing and evaluating data • making deductions and additions • reaching conclusions. Research is • Desire to face the challenge in solving the unsolved problems • Desire to get intellectual joy of doing some creative work • Desire to be of service to society • Desire to get respectability.

  3. Begin with the end in mind. PRE REQUISITE • Research gap • Research methodology • Research plan. • Research Approach • Logical theoretical • Quantitative, experimental • Qualitative, observational • Thesis Organization

  4. Be confident. • Record your progress. • To crystallize your thoughts. • To accomplish your daily task. • To track your progress. • To have material to draw on. • Not toforget what you were thinking two weeks ago. • Work on your strengths not weaknesses. • Exercise regularly. • Be smart. Research is your life, not your supervisor’s.

  5. EXPERIMENTAL AND THEORETICAL STUDIES ON CONFINED STEEL CONCRETE COMPOSITE BEAMS UNDER COMBINED BENDING AND TORSIONby D. Vijayalakshmi(06ZA003) Dr. R. Mercy Shanthi Dr. D. Tensing Joint Research Supervisor Research Supervisor

  6. OUTLINE OF PRESENTATION • Introduction • Literature Survey • Experimental Programme on CSCC beams • Test Procedure and Test Results • Analysis of Ultimate Strength of CSCC beams under combined loading • Evaluation of Test results • Finite Element Analysis • Discussion of Test Results • Conclusions and Recommendations

  7. 1. INTRODUCTION • General • Composite Construction • Steel Concrete Composite Construction • Confined Steel Concrete Composite Beam • Concrete beam shuttered with cold formed steel sheet by means of shear connectors and top bracings • Research Methodology • Research Schedule

  8. RESEARCH SCHEDULE

  9. OBJECTIVES OF PRESENT STUDY • Behaviour of CSCC beam under combined loading (bending and torsion) • Interaction equation between bending and torsion • Effect of bending moment on the torsional strength • Effect of shear connectors on the ultimate strength of beam • Effect of bond force on the ultimate strength of beam • Effect of dimension of beam on the ultimate strength of beam • Effect of spacing of bracing on the ultimate strength of beam • Comparison of Deflection results with ANSYS

  10. SCOPE OF PRESENT STUDY • 32 Nos of CSCC beams - pure bending, pure torsion and combined bending and torsion • Beam size 150 x 230 x 2300mm and 150 x 300 x 2300mm • Sheet thickness – 1.2 mm and 1.5 mm • Bracings – 148 x 10 mm • Spacing of bracings – 100 mm and 150 mm • M25 grade of concrete • Reinforcement: 2 nos of 8 mm diameter • Mix ratio - 1:1.47:2.72 with W/C 0.45

  11. EXPERIMENTS ON BEAM ELEMENTS • 32 beams under four groups • Method of construction-Fabrication of trough and concreting • The various parameters of test programme includes • Thickness of sheet • Crossection • Spacing of bracing

  12. 4. TEST PROCEDURE AND RESULT 4.1 Pure Bending • Group A-8 beams • Two point loading • Test setup with instrumentation

  13. OBSERVATION • Initial separation of sheet • First crack at 40% of ultimate load • Propagation of crack, crushing of concrete, failure of bracing and yielding of steel

  14. 4.2 PURE TORSION • Group D-8 beams • Test setup Test setup for Pure Torsion

  15. OBSERVATION ABOUT THE BEHAVIOR OF BEAMS • Diagonal cracks close to 45degrees at top • Bracings act as ties and restrict the torsional deflection and improves the torsional capacity • Well defined failure • Separation of sheet occurs • Inclined cracks develop at top and propagates to longitudinal sides and crack widens followed by failure of connectors • Failure occurs at vicinity of bottom face and rotation about longitudinal axis near bottom face

  16. 4.3 COMBINED BENDING AND TORSION • Group B- 8beams 30% of ultimate theoretical torque followed by the flexural load till failure • Group C- 8beams 60% of ultimate theoretical torque followed by flexure till failure. • Test setup

  17. OBSERVATION ABOUT THE BEHAVIOR OF BEAMS • Angle of twist and twisting moment increases linearly • Sheets are separated first • Bracing at top delays the failure • Crack widens • Rotation at failure occurs near the top face

  18. THEORETICAL INVESTIGATION 5. ANALYSIS Crack pattern under pure torsion

  19. Beam subjected to flexural moment and torsion Failure of a piece of chalk under torque

  20. MODES OF FAILURE Idealised pattern for Mode 1 failure Idealised pattern for Mode 2 failure Idealised pattern for Mode 3 failure

  21. Equation for Mt1 External moments are due to • Bending • Twisting Internal moments are due to • Component of tensile force in the bottom sheet. • Component of tensile force along longitudinal reinforcement. • Component of tensile force in the side sheet. • Component of bond force at bottom between • The concrete and sheet • The concrete and connector

  22. 5) Component of bond force at sides between • The concrete and sheet • The concrete and connector • From the equilibrium of internal and the external moments about an axis parallel to the neutral axis and located at mid-depth of the equivalent compression zone, the following equation is obtained

  23. Equation for X1 Forces considered to derive x1 acting perpendicular to the plane which contains neutral axis and is perpendicular to the top face of the beams are; • Component of tensile force in longitudinal reinforcement • Component of tensile force in bottom sheet • Component of bond force at bottom between • The concrete and sheet • The concrete and connector • Force in concrete compression zone

  24. From the equilibrium of forces acting perpendicular to the plane which contains the neutral axis and is perpendicular to the top face of the beam, the following equation is obtained

  25. COMPARSION OF THEORETICAL AND EXPERIMENTAL RESULTS

  26. CONCLUSIONS BEHAVIOUR IN PURE BENDING • Bracings at top delays the separation of sheet and there by failure • Followed by local buckling of sheet, formation of cracks and crushing of concrete and yielding of steel • The deflection varies linearly up to the yield point in pure bending • Local buckling of sheet starts at 40-50% of the ultimate load at pure bending

  27. BEHAVIOUR IN PURE TORSION • The bracings at top contribute significantly to the torsional strength of the beam • Failure observed in two stages – before cracking and after cracking • Before cracking behaviour is affected very little • After cracking mode of failure is observed by width of cracks and rotation at vicinity of the beam • Cracks starts at 25-30% of ultimate torque value in pure torsion and combined bending and torsion

  28. BEHAVIOUR IN COMBINED BENDING AND TORSION • The composite beams subjected to combined bending and torsion is characterized by three modes of failure • The mode of failure predicted in the analysis do not agree with the observed mode of failure • Upward deflection in Group C beams • In combined bending and torsion, both B and C group beam exhibits Mode 1 failure. This may be due to the confinement of sheet on three sides and the interfacial bond between the concrete and connectors

  29. RECOMMENDATIONS • The effect of shear is not accounted in generating the equations of ultimate strength under combined loading. The research can be extended to include the effect of shear and the shear strength capacity of the connectors • The effect of placing the shear connectors at salient locations of the beam must be studied • The equations can be developed for the beams subjected to constant bending moment and applying twisting moment till failure • The equation can be developed to find the angle of twist under combined loading and comparison can be made for both theoretical and experimental value of angle of twist • The research can be extended with profiled sheeting as confinement

  30. Extension of analysis to formulate the design methodology of the composite beams under pure torsion and combined bending and torsion can be made • The beams can be tested for negative bending • Extension of analysis to formulate the design methodology of the composite beams under pure torsion and combined bending and torsion can be made • The beams can be tested for negative bending • The cross-section other than the rectangular cross sections can be tried for combined loading in composite beams

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