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MASONRY ARCH BRIDGES LOAD CARRYING CAPACITY

MASONRY ARCH BRIDGES LOAD CARRYING CAPACITY. Simply Supported Beam Supporting single point load. Simply Supported Beam Supporting two point load. Simply Supported Beam Supporting UDL. Suspension cable with single point load. Suspension cable with two point load.

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MASONRY ARCH BRIDGES LOAD CARRYING CAPACITY

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  1. MASONRYARCH BRIDGES LOAD CARRYING CAPACITY

  2. Simply Supported Beam Supporting single point load

  3. Simply Supported Beam Supporting two point load

  4. Simply Supported Beam Supporting UDL

  5. Suspension cable with single point load

  6. Suspension cable with two point load

  7. Suspension cable with UDL load

  8. True Arch supporting single point Load

  9. True Arch supporting Two point Load

  10. True Arch supporting UD Load

  11. CONCEPT OF AN ARCH Concept first understood by Robert Hooke in 1865

  12. Components of Arch

  13. ELEMENTS OF AN ARCH BRIDGE

  14. Arch Bridges

  15. ARCH BRIDGES

  16. LOAD TRANSFER MECHANISM • Horizontal thrust on sub structure • Vertical load on foundation

  17. Analysis of Simple structures • Analysis of any structure is based on Equilibrium condition of forces- • For 3 dimensional structures- • Six conditions • ∑ Fx = 0, ∑ Fy = 0, ∑ Fz = 0, • ∑ Mx = 0, ∑ My = 0, ∑ Mz = 0, • For 2 dimensional structures- • 3 conditions • ∑ Fx = 0, ∑ Fy = 0, ∑ Mz = 0,

  18. Determinacy of structures • Structure is determinate if no. of unknown forces (member forces/support forces) are equal to equilibrium conditions. • Structure is indeterminate if no. of unknown forces (member forces/support forces) are more than equilibrium conditions. • Stability of any structure is directly proportional to Indeterminacy. • In real life situation, most of the structure are indeterminate

  19. If the indeterminacy is zero, structure is just stable and safe. • If indeterminacy is less than zero (-ve), structure will fail under load.

  20. Hinges Single span- 4 hinges

  21. FAILURE UNDER LOAD

  22. Single span- Sliding

  23. Single span- hinges and sliding

  24. MULTI SPANS - 7 HINGES

  25. MULTI-SPAN Bridge : 8 HINGES

  26. Example of load v/s hinge formation

  27. Example of Load v/s hinge formation

  28. LOAD CARRYING CAPACITY ASSESSMENT

  29. Exact ASSESSMENT OF ARCH BRIDGE IS DIFFICULT? • Least understood • Not taught in academic institutions • Inadequate coverage in codes and manuals of IR • Interaction of arch barrel & fill; fill & spandrel/parapet is yet not fully understood • Inadequate knowledge of construction details • Non-availability of drawings

  30. Construction details (not visible) • Ring thickening • Haunches and backing • Internal spandrel walls • Cross vaults and open spandrels • Materials (adjoining bridges can help) • Joints

  31. Possible extent of backing

  32. THICKNESS OF ARCH

  33. RING THICKNESS

  34. STAGES IN ASSESSMENT • Detailed field inspections of all the bridges. • The requisite geometrical parameters obtained from field inspections. • General condition of bridges recorded.

  35. Assessment Methods • MEXE METHOD • MODIFIED MEXE METHOD • RING • ARCHIE – M • Survey and tabulation method

  36. MEXE METHOD • First engineering method developed by Pippard & Ashby (1939) and Pippard (1948) for use in second world war. • MEXE established in 1963 after full scale load tests carried out in 1950s. • Given in UIC code 778-3R. • Empirical Method, no scope for parametric study.

  37. MEXE METHOD

  38. MEXE METHOD Q = Qp . K Where K = Kp . Ks . Km . Kv. Kc Kp: profile factor Ks: Shape factor Km : material factor Kv : condition factor Kc : crack factor

  39. MEXE METHOD • Obtain Qp in KNfrom graph for specific ring thickness at crown and span

  40. MEXE METHOD • Apply profile factor (Kp)

  41. MEXE METHOD • Apply shape factor (KS) from graph for rq to rc ratio

  42. MEXE METHOD • Material factor (KM) • Soft brick and soft stone = 1.0 • Hard brick = 1.2 • Mass concrete = 1.2 • Stone Masonry = 1.5

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