Seismic Design and Detailing of Reinforced Concrete Structures Based on CSA A23.3 - 2004

1. Seismic Design and Detailing of Reinforced Concrete Structures Based on CSA A23.3 - 2004 Murat Saatcioglu PhD,P.Eng. Professor and University Research Chair Department of Civil Engineering The University of Ottawa Ottawa, ON

2. Basic Principles of Design Reinforced concrete structures are designed to dissipate seismic induced energy through inelastic deformations Ve Ve = S(Ta) Mv IE W / (Rd Ro) Ve /Rd Ve /Rd Ro D

3. Basic Principles of Design Inelasticity results softening in the structure, elongating structural period S(T) S1 S2 T1 T2 T

4. Basic Principles of Design Capacity  Demand It is a good practice to reduce seismic demands, to the extent possible…. This can be done at the conceptual stage by selecting a suitable structural system.

5. To reduce seismic demands… • Select a suitable site with favorable soil conditions • Avoid using unnecessary mass • Use a simple structural layout with minimum torsional effects • Avoid strength and stiffness taper along the height • Avoid soft storeys • Provide sufficient lateral bracing and drift control by using concrete structural walls • Isolate non-structural elements

6. Seismic Amplification due to Soft Soil

7. Liquefaction

8. Liquefaction

9. Liquefaction

10. To reduce seismic demands… • Select a suitable site with favorable soil conditions • Avoid using unnecessary mass • Use a simple structural layout with minimum torsional effects • Avoid strength and stiffness taper along the height • Avoid soft storeys • Provide sufficient lateral bracing and drift control by using concrete structural walls • Isolate non-structural elements

11. Use of Unnecessary Mass

12. Use of Unnecessary Mass

13. Use of Unnecessary Mass

14. Use of Unnecessary Mass

15. To reduce seismic demands… • Select a suitable site with favorable soil conditions • Avoid using unnecessary mass • Use a simple structural layout with minimum torsional effects • Avoid strength and stiffness taper along the height • Avoid soft storeys • Provide sufficient lateral bracing and drift control by using concrete structural walls • Isolate non-structural elements

16. Effect of Torsion

17. Effect of Torsion

18. Effect of Torsion

19. Effect of Torsion

20. Effect of Torsion

21. Effect of Torsion

22. Effect of Torsion

23. Effect of Torsion

24. To reduce seismic demands… • Select a suitable site with favorable soil conditions • Avoid using unnecessary mass • Use a simple structural layout with minimum torsional effects • Avoid strength and stiffness taper along the height • Avoid soft storeys • Provide sufficient lateral bracing and drift control by using concrete structural walls • Isolate non-structural elements

25. Effect of Vertical Discontinuity

26. Effect of Vertical Discontinuity

27. To reduce seismic demands… • Select a suitable site with favorable soil conditions • Avoid using unnecessary mass • Use a simple structural layout with minimum torsional effects • Avoid strength and stiffness taper along the height • Avoid soft storeys • Provide sufficient lateral bracing and drift control by using concrete structural walls • Isolate non-structural elements

28. Effect of Soft Storey

29. Effect of Soft Storey

30. Effect of Soft Storey

31. Effect of Soft Storey

32. To reduce seismic demands… • Select a suitable site with favorable soil conditions • Avoid using unnecessary mass • Use a simple structural layout with minimum torsional effects • Avoid strength and stiffness taper along the height • Avoid soft storeys • Provide sufficient lateral bracing and drift control by using concrete structural walls • Isolate non-structural elements

33. R/C Frame Buildings without Drift Control

34. Buildings Stiffened by Structural Walls

35. To reduce seismic demands… • Select a suitable site with favorable soil conditions • Avoid using unnecessary mass • Use a simple structural layout with minimum torsional effects • Avoid strength and stiffness taper along the height • Avoid soft storeys • Provide sufficient lateral bracing and drift control by using concrete structural walls • Isolate non-structural elements

36. Short Column Effect

37. Short Column Effect

38. Seismic Design Requirements of CSA A23.3 - 2004 Capacity design is employed….. Selected elements are designed to yield while critical elements remain elastic Design for Strength and Deformability

39. Load Combinations Principal loads: 1.0D + 1.0E And either of the following: 1) For storage occupancies, equipment areas and service rooms: 1.0D + 1.0E + 1.0L + 0.25S 2) For other occupancies: 1.0D + 1.0E + 0.5L + 0.25S

40. Stiffness Properties for Analysis • Concrete cracks under own weight of structure • If concrete is not cracked, then the structure is not reinforced concrete (plain concrete) • Hence it is important to account for the softening of structures due to cracking • Correct assessment of effective member stiffness is essential for improved accuracy in establishing the distribution of design forces among members, as well as in computing the period of the structure.

41. Flexural Behaviour of R/C

42. Flexural Behaviour of R/C

43. Section Properties for Analysis as per CSA A23.3-04 Beams Ie = 0.40 Ig Columns Ie = acIg Coupling Beams without diagonal reinforcement Ave = 0.15Ag Ie = 0.40 Ig with diagonal reinforcement Ave = 0.45Ag Ie = 0.25 Ig Slab-Frame Element Ie = 0.20 Ig Walls Axe = awAg Ie = aw Ig

44. Seismic Design Requirements of CSA A23.3 - 2004 • Chapter 21 covers: • Ductile Moment Resisting Frames (MRF) • Moderately Ductile MRF • Ductile Shear Walls • Ductile Coupled Shear Walls • Ductile Partially Coupled Shear Walls • Moderately Ductile Shear Walls

45. Ductile Moment Resisting Frame Members Subjected to Flexure Rd = 4.0 Pf≤ Agf’c /10

46. Beam Longitudinal Reinforcement

47. Beam Transverse Reinforcement No lap splicing within this region

48. Formation of Plastic Hinges

49. Beam Shear Strength

50. Beam Shear Strength • The factored shear need not exceed that obtained from structural analysis under factored load combinations with RdRo = 1.0 • The values of q = 45o and b = 0 shall be used in shear design within plastic hinge regions • The transverse reinforcement shall be seismic hoops