PCI 6th Edition

1. PCI 6th Edition Building Systems (Seismic)

2. Presentation Outline Building System Loads Seismic Structural Integrity LFRS – Walls LFRS – Frames Diaphragms

3. Seismic Changes Based on new changes to ASCE 7 and ACI 318 Based current seismic research and observations

4. Seismic Changes Some of these changes are: Recognition of jointed panel construction Recognition of strong and ductile connections in precast frames Recognition and requirements for connections in precast walls Recognition of jointed panel construction as an alternative to emulation of monolithic construction. Achieving ductile structural behavior by using “strong” connections that remain elastic while nonlinear action (plastic hinging) occurs in the member away from the connection. Modification of drift computation and limiting drift. Deformation compatibility of structural elements and attached non-structural elements. Additional soil type classifications. Special considerations for building sites located near seismic faults. Special considerations for structures possessing redundancy. Recognition of jointed panel construction as an alternative to emulation of monolithic construction. Achieving ductile structural behavior by using “strong” connections that remain elastic while nonlinear action (plastic hinging) occurs in the member away from the connection. Modification of drift computation and limiting drift. Deformation compatibility of structural elements and attached non-structural elements. Additional soil type classifications. Special considerations for building sites located near seismic faults. Special considerations for structures possessing redundancy.

5. Seismic Changes Additional changes are: Modification of drift computation and limiting drift Deformation compatibility of elements Additional soil type classifications Special considerations locations near seismic faults Consideration of redundancy and reliability in strength design requirements Recognition of jointed panel construction as an alternative to emulation of monolithic construction. Achieving ductile structural behavior by using “strong” connections that remain elastic while nonlinear action (plastic hinging) occurs in the member away from the connection. Modification of drift computation and limiting drift. Deformation compatibility of structural elements and attached non-structural elements. Additional soil type classifications. Special considerations for building sites located near seismic faults. Special considerations for structures possessing redundancy. Recognition of jointed panel construction as an alternative to emulation of monolithic construction. Achieving ductile structural behavior by using “strong” connections that remain elastic while nonlinear action (plastic hinging) occurs in the member away from the connection. Modification of drift computation and limiting drift. Deformation compatibility of structural elements and attached non-structural elements. Additional soil type classifications. Special considerations for building sites located near seismic faults. Special considerations for structures possessing redundancy.

6. Seismic Changes Design Forces are Based on Risk Previous codes based on 10% chance of exceedance in 50 years IBC 2000, 2003 codes based on 2% chance of exceedance in 50 years

7. Seismic Risk Soil factors Other regions of high seismic risk - not just west coast anymore

8. Practically every precast, prestressed concrete structure designed under IBC 2000 will require some consideration of seismic effects.

9. Seismic Performance Objectives Current design - minor damage for moderate earthquakes Accepts major damage for severe earthquakes Collapse is prevented of severe events

10. Seismic Performance Objectives In order to achieve the design objectives, the current code approach requires details capable of undergoing large inelastic deformations for energy dissipation.

11. Seismic Design Approach Emulation No special requirements for low seismic risk Chapter 21 requirements for moderate and high seismic risk Non-emulative design PRESSS Acceptance criteria for frames

12. Earthquake Loads – Equivalent Lateral Force Method Base Shear, V V= Cs·W Where: Cs - Seismic Response Coefficient W - Total Weight

13. Equivalent Lateral Force Method Limitations This method may not apply to buildings with irregularities in Seismic Design Categories D, E, or F

14. Earthquake Loads – Total Weight, W Dead Load of structure plus: 25% of reduced floor live load in storage areas live load in parking structures not included Partition load if included in gravity dead Total weight of permanent equipment 20% of flat roof snow load, pf where pf > 30 psf

15. Seismic Response Coefficient, Cs Function of Spectral response acceleration Site soil factors Building Period Response modification factors Importance factor

16. Seismic Response Coefficient, Cs Step 1 - Determine SS and S1 Step 2 - Determine site Soil Classification Step 3 - Calculate Response Accelerations Step 4 - Calculate the 5% Damped Design Spectral Response Accelerations Step 5 - Determine the Seismic Design Category Step 6 - Determine the Fundamental Period Step 7 - Calculate Seismic Response Coefficient

17. Step 1 – Determine SS and S1 From IBC Map From local building codes IBC 2003 CD-ROM Based on Longitude / Latitude Zip Code

19. Step 2 – Determine Site Soil Classification If site soils are not known use Site Class D Figure 3.10.7 (a) (page 3-111) From soil reports

20. Step 3 – Calculate Response Accelerations SMS = Fa·SS SM1 = Fv·S1 Where: Fa and Fv are site coefficients from Figure 3.10.7 (b) and (c) (page 3-111) SS spectral accelerations for short periods S1 spectral accelerations for 1-second period All values based on IBC 2003

21. Step 4 – Calculate the 5%-Damped Design Spectral Response Accelerations SDS = (2/3)SMS SD1 = (2/3)SM1

22. Step 5 – Determine the Seismic Design Category Table 3.2.4.1. Sometimes this restricts the type of Seismic Force Resisting System (SFRS) used (see Figure 3.10.8) (page 3-112)

23. Step 6 – (Approximate Period) Determine the Buildings Fundamental Period Where: Ct = 0.016 for moment resisting frame systems of reinforced concrete 0.020 for other concrete structural systems x = 0.9 for concrete moment resisting frames 0.75 for other concrete structural systems hn = distance from base to highest level (in feet) Ct = 0.016 for moment resisting frame systems of reinforced concrete in which the frames resist 100% of the required seismic forces and are not enclosed or adjoined by more rigid components that prevent that frame from deflecting when subjected to seismic forces .Ct = 0.016 for moment resisting frame systems of reinforced concrete in which the frames resist 100% of the required seismic forces and are not enclosed or adjoined by more rigid components that prevent that frame from deflecting when subjected to seismic forces .

24. Step 6 – (Exact Period) Determine the Buildings Fundamental Period Rayleigh’s formula Where: wi = dead load weight at Floor i di = elastic displacement at Floor i Fi = lateral force at Floor i g = acceleration of gravity n = total number of floors

25. Step 7 – Determine Seismic Response Coefficient, Cs Lesser of Where: R = Response Modification Factor Figure 3.10.8 (page 3-112) ? = Seismic Importance Factor

26. Step 7 – Determine Cs Minimum Value of Cs Special Cases In Seismic Design Categories E and F

27. Vertical Distribution of Lateral Force Where: Fx = Force per floor Cvx = Vertical distribution factor V = Base shear k = 1 - buildings with a period = 0.5 sec = 2 - buildings with a period > 2.5 sec hi and hx = height from base to Level i or x wi and wx = Level i or x portion of total gravity load For buildings with a period between 0.5 and 2.5, determine k by linear interpolation.For buildings with a period between 0.5 and 2.5, determine k by linear interpolation.

28. Location of Force in Plane Accidental Torsion calculated by assuming that the center of mass is located a distance of 5% of the plan dimension perpendicular to the applied load on either side of the actual center of mass Total torsion = sum of the actual torsion plus the accidental torsion

29. Seismic Drift Requirements Elastic Displacement Amplification Factor, dx Stability Coefficient Limits, q P-D Effects

30. Drift Limits Figure 3.10.9 (page 3-113)

31. Drift Amplification Factor, dx Where: dx = Amplified deflection of Level x dxe = Deflection of Level x determined from elastic analysis, includes consideration of cracking Cd = Deflection amplification factor (Figure 3.10.8) ? = Seismic Importance Factor The Cd factor represents an approximation of the post-yield or Non-linear displacement. The Cd factor represents an approximation of the post-yield or Non-linear displacement.

32. Stability Coefficient, ? Where: Px = Total vertical unfactored load including and above Level x ? = Difference of deflections between levels x and x-1 Vx = Seismic shear force acting between levels x and x-1 hsx = Story height below Level x Cd = Deflection amplification factor

33. Stability Coefficient, ? The stability coefficient is limited to: Where: ß = ratio of shear demand to shear capacity between Levels x and x-1

34. P-D Effects To account for P-? effects, the design story drift is increased by (1- ?)-1 If ? < 0.10, P-? effects may be neglected

35. Reliability Factor, ri Required in High Seismic Design Categories D, E, and F The Earthquake Force is increase by a Reliability Factor, ri 1.5 Maximum Required Value ri = 1.0 for structures in Seismic Design Categories A, B and C

36. Reliability Factor, ri For Moment Frames Where, for each level: Ai = floor area rmaxi = For moment frames, the maximum of the sum of the shears in any two adjacent columns divided by the story shear. For columns common to two bays with moment-resisting connections on opposite sides, 70% of the shear in that column may be used in the column shear summary.

37. Reliability Factor, ri For Shear Walls Where, for each level: Ai = floor area rmaxi = For shear walls, the maximum value of the product of the shear in the wall and 10/lw divided by the story shear.

38. Load Combinations U = 1.4(D+F) U = 1.2(D+F+T) + 1.6(L+H) U = 1.2D +1.6(Lr or S or R) + (1.0L or 0.8W) U = 1.2D + 1.6W + 1.0L + 0.5(Lr or S or R) U = 1.2D + 1.0E + f1L + 0.2S U = 0.9D + 1.6W + 1.6H U = 0.9D + 1.0E + 1.6H f1 = 1.0 Parking garages = 1.0 Live load = 100 psf on public assembly floors = 0.5 All others f1 = 1.0 for floors in places of public assembly, for live loads in excess of 100 psf, and for parking garages, otherwise, f1 = 0.5 D = Dead load F = Pressure of fluids of known density and controlled depths T = Effects of temperature, creep and shrinkage L = Live load H = Soil load Lr = Roof live load S = Snow load R = Rain load W = Wind load E = Seismic load f1 = 1.0 for floors in places of public assembly, for live loads in excess of 100 psf, and for parking garages, otherwise, f1 = 0.5 D = Dead load F = Pressure of fluids of known density and controlled depths T = Effects of temperature, creep and shrinkage L = Live load H = Soil load Lr = Roof live load S = Snow load R = Rain load W = Wind load E = Seismic load

39. Modification for Vertical Acceleration E = ?·QE ± 0.2·SDS·D Seismic Load Combinations Become U = (1.2 + 0.2·SDS)D + ?·QE + f1L + 0.2S U = (0.9 – 0.2·SDS)D + ?·QE + 1.6H

40. Modification for Vertical Acceleration E = ?·QE ± 0.2·SDS·D Seismic Load Combinations Become U = (1.2 + 0.2·SDS)D + ?·QE + f1L + 0.2S U = (0.9 – 0.2·SDS)D + ?·QE + 1.6H

41. Overstrength Factor, Wo Components within the Diaphragm Chord ties Shear Steel Connectors ?o = 2.0 - Seismic Design Categories C, D, E and F ?o = 1.0 - Seismic Design Categories A and B

42. Special Load Combinations U = 1.2D + fi·L + Em U = 0.9D + E Where: Em = Wo·QE + 0.2·SDS·D and Wo = Overstrength Factor

43. Overstrength Factor, Wo Connections from Diaphragms to Seismic Force Resisting System (SFRS) ?o = Seismic Design Categories C and higher Figure 3.10.8 (page 3-112)

44. Structural Integrity Requirements All members must be connected to the Lateral Force Resisting System (LFRS) Tension ties must be provided in all directions The LFRS is continuous to the foundation A diaphragm must be provided with Connections between diaphragm elements Tension ties around its perimeter Perimeter ties provided Nominal strength of at least 16 kips Within 4 ft of the edge Column splices and column base connections must have a nominal tensile strength not less than 200Ag in pounds All members must be connected to the lateral force resisting system and their supporting members. Tension ties must be provided in the transverse, longitudinal, and vertical directions and around the perimeter of the structure. The lateral force resisting system must be continuous to the foundation. A diaphragm must be provided with connections between diaphragm elements, with tension ties around its perimeter and around openings that significantly interrupt diaphragm action. Section 16.5.2.4 of ACI 318-02 requires perimeter ties to provide a nominal strength of at least 16 kips and to be within 4 ft of the edge. Column splices and column base connections must have a nominal tensile strength not less than 200Ag in lbs, where Ag is the gross area of the column in sq in. For a compression member with a larger cross section than required by consideration of loading, a reduced effective area, Ag, not less than one-half the total area, may be used. All members must be connected to the lateral force resisting system and their supporting members. Tension ties must be provided in the transverse, longitudinal, and vertical directions and around the perimeter of the structure. The lateral force resisting system must be continuous to the foundation. A diaphragm must be provided with connections between diaphragm elements, with tension ties around its perimeter and around openings that significantly interrupt diaphragm action. Section 16.5.2.4 of ACI 318-02 requires perimeter ties to provide a nominal strength of at least 16 kips and to be within 4 ft of the edge. Column splices and column base connections must have a nominal tensile strength not less than 200Ag in lbs, where Ag is the gross area of the column in sq in. For a compression member with a larger cross section than required by consideration of loading, a reduced effective area, Ag, not less than one-half the total area, may be used.

45. Structural Integrity Requirements Precast vertical panels connected by a minimum of two connections Each connection is to have a nominal strength of 10 kips Precast diaphragm connections to members being laterally supported must have a nominal tensile strength not less than 300 lbs per linear ft Connection details allow volume change strains Connection details that rely solely on friction caused by gravity loads are not to be used Precast walls, other than cladding panels, must be connected across horizontal joints by a minimum of two connections per panel. Each connection is to have a nominal tensile strength of not less than 10 kips. When design forces result in no tension at the base, these connections are permitted to be anchored into an appropriately reinforced slab on grade. If panels are too narrow to accommodate two connections, a single connection is satisfactory, as long as it is connected to adjacent panels. Where precast elements form roof or floor diaphragms, the connections between the diaphragm and those members being laterally supported must have a nominal tensile strength not less than 300 lbs per linear ft. To accommodate volume change strains (temperature and shrinkage) in supported beams, tie connections are typically located at the top of the member, with elastomeric pads used at the bottom-bearing surface. Such ties can be accomplished by welding, bolting, reinforcing steel in grout joints or bonded topping, or by doweling. Connection details that rely solely on friction caused by gravity loads are not to be used. Exceptions may be permitted for heavy modular unit structures where resistance to overturning or sliding has a large factor of safety.Precast walls, other than cladding panels, must be connected across horizontal joints by a minimum of two connections per panel. Each connection is to have a nominal tensile strength of not less than 10 kips. When design forces result in no tension at the base, these connections are permitted to be anchored into an appropriately reinforced slab on grade. If panels are too narrow to accommodate two connections, a single connection is satisfactory, as long as it is connected to adjacent panels. Where precast elements form roof or floor diaphragms, the connections between the diaphragm and those members being laterally supported must have a nominal tensile strength not less than 300 lbs per linear ft. To accommodate volume change strains (temperature and shrinkage) in supported beams, tie connections are typically located at the top of the member, with elastomeric pads used at the bottom-bearing surface. Such ties can be accomplished by welding, bolting, reinforcing steel in grout joints or bonded topping, or by doweling. Connection details that rely solely on friction caused by gravity loads are not to be used. Exceptions may be permitted for heavy modular unit structures where resistance to overturning or sliding has a large factor of safety.

46. Lateral Force Resisting Systems (LFRS) Rigid frames and shear walls exhibit different responses to lateral loads

47. Influential Factors The supporting soil and footings The stiffness of the diaphragm The stiffness LFRS elements and connections Lateral load eccentricity with respect to center of rigidity of the shear walls or frames The relative flexural and shear stiffnesses of the shear walls, and of connections.The relative flexural and shear stiffnesses of the shear walls, and of connections.

48. Shear Wall Systems Most common lateral force resisting systems Design typically follows principles used for cast-in-place structures

49. International Building Code(IBC) Requirements Two categories of shear walls Ordinary Special

50. ACI 318-02 Requirements Created an additional intermediate category, but has assigned no distinct R, ?o and Cd

51. ACI 318-02 Wall Definitions Defines all shear walls as “structural walls” Three levels of definition Ordinary structural (shear) wall Intermediate precast structural (shear) wall Special precast structural (shear) wall

52. Ordinary Structural (Shear) Wall Wall complying with the requirements of Chapters 1 through 18 No special seismic detailing

53. Intermediate Precast Structural(Shear) Wall Wall complying with all applicable requirements of Chapters 1 through 18 Added requirements of Section 21.13 Ductile connections with steel yielding 1.5 factor for non-yielding elements IBC imposes restriction that yielding be in the reinforcing

54. Special Precast Structural (Shear) Wall Precast wall complying with the requirements of 21.8. Meeting the requirements for ordinary structural walls and the requirements of 21.2 Requires precast walls to be designed and detailed like cast-in-place walls, “emulative” design Meet the connection requirements of Section 21.13.

55. Design Guidelines for Shear Wall Structures Evaluation of building function and applicable precast frame Preliminary development of shear wall system Determination of vertical and lateral loads In a warehouse type structure, it is common to include the exterior walls as part of the lateral load resisting system. In parking structures, shear walls can be located at stair and elevator towers, at the perimeter or ramped bays, at selected locations on the perimeter of the structure, or any in combination of the above locations a. Provide at least three non-collinear walls to ensure torsional as well as direct lateral resistance. b. Overturning will often be the governing criterion. Thus, the first choice is to use shear walls that also function as bearing walls. c. Arrange shear walls so that they minimize restraint due to volume changes. d. Consider whether the shear walls could be individual full height walls (vertical joints only). e. Consider the practicality of shipping and erection when selecting the size of wall panels. f. Balance the design requirements of the shear walls with the design requirements of the associated diaphragms. Determine the vertical gravity loads that are applicable to each of the shear walls. Use the applicable seismic design criteria to determine the magnitude of lateral load at each floor, and compare with wind loading. Choose the critical condition for design. In a warehouse type structure, it is common to include the exterior walls as part of the lateral load resisting system. In parking structures, shear walls can be located at stair and elevator towers, at the perimeter or ramped bays, at selected locations on the perimeter of the structure, or any in combination of the above locations a. Provide at least three non-collinear walls to ensure torsional as well as direct lateral resistance. b. Overturning will often be the governing criterion. Thus, the first choice is to use shear walls that also function as bearing walls. c. Arrange shear walls so that they minimize restraint due to volume changes. d. Consider whether the shear walls could be individual full height walls (vertical joints only). e. Consider the practicality of shipping and erection when selecting the size of wall panels. f. Balance the design requirements of the shear walls with the design requirements of the associated diaphragms. Determine the vertical gravity loads that are applicable to each of the shear walls. Use the applicable seismic design criteria to determine the magnitude of lateral load at each floor, and compare with wind loading. Choose the critical condition for design.

56. Design Guidelines for Shear Wall Structures Preliminary load analysis Selection of shear walls Final load analysis Final shear wall design Diaphragm design Determine the overturning moment, the lateral in plane shear and the axial load at the base of each of the shear walls. a. Review the preliminary choice of shear wall size and location. b. Modify the number, location, and dimensions of shear walls as necessary to satisfy the requirements at the base of each. It is economically preferable that foundations not be subject to uplift. Based on the final location and dimensions of shear walls, perform the final lateral load and vertical load analysis to determine the design load for each of the shear walls. Consider shear stiffness as well as flexural stiffness when distributing lateral loads to the shear walls. Design the shear wall reinforcement and the connections to the associated diaphragms. Where there is insufficient length of shear wall available to accommodate the necessary number of shear connectors, consider using an element in the plane of the diaphragm (drag strut) as an extension of the shear wall to pick up additional connectors to the diaphragm. Consider the additional requirements necessary to satisfy the structural integrity provisions of the code (see Section 3.3). a. Design the diaphragms to respond elastically to applied lateral loads in order to prevent formation of plastic regions in any diaphragm. See Section 3.8 for a more detailed discussion of diaphragm design. b. Design the diaphragms as beams, provide the necessary tensile reinforcement for each chord, and choose shear connectors using design procedures of Chapter 6, or shear reinforcement using shear-friction methods. c. Consider the additional requirements necessary to satisfy the structural integrity provisions of the code (see Section 3.3). Determine the overturning moment, the lateral in plane shear and the axial load at the base of each of the shear walls. a. Review the preliminary choice of shear wall size and location. b. Modify the number, location, and dimensions of shear walls as necessary to satisfy the requirements at the base of each. It is economically preferable that foundations not be subject to uplift. Based on the final location and dimensions of shear walls, perform the final lateral load and vertical load analysis to determine the design load for each of the shear walls. Consider shear stiffness as well as flexural stiffness when distributing lateral loads to the shear walls. Design the shear wall reinforcement and the connections to the associated diaphragms. Where there is insufficient length of shear wall available to accommodate the necessary number of shear connectors, consider using an element in the plane of the diaphragm (drag strut) as an extension of the shear wall to pick up additional connectors to the diaphragm. Consider the additional requirements necessary to satisfy the structural integrity provisions of the code (see Section 3.3). a. Design the diaphragms to respond elastically to applied lateral loads in order to prevent formation of plastic regions in any diaphragm. See Section 3.8 for a more detailed discussion of diaphragm design. b. Design the diaphragms as beams, provide the necessary tensile reinforcement for each chord, and choose shear connectors using design procedures of Chapter 6, or shear reinforcement using shear-friction methods. c. Consider the additional requirements necessary to satisfy the structural integrity provisions of the code (see Section 3.3).

57. Moment Frame Classifications Three Classifications Ordinary Moment Frame Intermediate Moment Frames Special Moment Frames Based on Detailing Seismic Design Categories The same frame with different rebar details can be Ordinary, Intermediate or Special.The same frame with different rebar details can be Ordinary, Intermediate or Special.

58. Ordinary Moment Frames Seismic Performance Categories A & B ACI 318 Chapters 1 to 18 Response modification factor, R = 3

59. Intermediate Moment Frames Seismic Performance Category C ACI 318 only defines intermediate as cast-in-place Response modification factor, R = 5

60. Special Moment Frames Seismic Performance Categories D, E, and F Yielding will be concentrated in the beam, Strong column -weak beam behavior Special Moment frames ACI 318 Sections 21.2 through 21.6 Response modification factor, R = 8

61. Diaphragms A diaphragm is classified as rigid if it can distribute the horizontal forces to the vertical lateral load resisting elements in proportion to their relative stiffness Long-span applications suggest that many precast diaphragms may in fact be flexible

62. Diaphragm Design The distinction between rigid and flexible diaphragms is important not just for diaphragm design, but also for the design of the entire lateral force resisting system.

63. Diaphragm Classification Flexible diaphragm Lateral deflection twice average story drift Rigid diaphragm Not flexible Implies capability to distribute load based on relative stiffness of LFRS elements

64. Steps in the Design Method Step 1 - Calculate and compare distribution and diaphragm forces Based on rigid diaphragm action Based on flexible diaphragm action Step 2 - Check of diaphragm deformation with respect to drift limits Step 3 - Check attached element drift limits Step 4 - Adjustments in vertical element stiffness and placement to limit drift

65. Diaphragm Design Forces Based on Wind and Seismic Events Wind Combined windward and leeward wind pressures Act as uniform load on building perimeter Distributed to the LFRS based on diaphragm behavior

66. Seismic Diaphragm Design Forces Separate calculations from the design of the LFRS Diaphragm Design force, FP Seismic Design Categories B or C Fp = 0.2·IE·SDS·Wp + Vpx Where Vpx – represents forces from above levels that must be transferred through the diaphragm due to vertical system offsets or changes in stiffness. Vpx – represents forces from above levels that must be transferred through the diaphragm due to vertical system offsets or changes in stiffness. Vpx – represents forces from above levels that must be transferred through the diaphragm due to vertical system offsets or changes in stiffness.

67. Seismic Diaphragm Design Forces Seismic Design Category D 0.2·IE·SDS·wpx< Fp < 0.4·IE·SDS·wpx Vpx – represents forces from above levels that must be transferred through the diaphragm due to vertical system offsets or changes in stiffness. Vpx – represents forces from above levels that must be transferred through the diaphragm due to vertical system offsets or changes in stiffness.

68. Diaphragm Detailing Wind and Low Seismic Hazards Moderate Seismic Hazards Seismic Design Category D - Topped Systems High Seismic Hazards - Untopped Systems

69. Wind and Low Seismic Hazard Seismic Design Category A Strength requirements imposed by the applied forces, No Amplification Seismic Design Category B Requires the design of collector elements Does not require forces to be increased by over strength factor, ?o (Revised from IBC 2000)

70. Moderate Seismic Hazard Topped and Pretopped Systems Seismic Design Category C Concrete wall systems have special requirements IBC 2003 Diaphragm must include special continuous struts or ties between diaphragm chords for wall anchorage. use of Sub-Diaphragms, the aspect ratio of is limited to 2½ to 1

71. Moderate Seismic Hazard Walls classified as Intermediate Precast Walls Collector elements, their connections based on special load combinations Need to include overstrength factor Ductile connections with wall interface The body of the connection must have sufficient strength to permit development of 1.5fy in the reinforcing steel the interface with the wall must be with ductile connections including the reinforcing steel that would yield prior to crushing of the concrete. The body or mechanical parts of the connection (e.g., plates, welds, etc.) must have sufficient strength to permit development of 1.5fy in the reinforcing steel. the interface with the wall must be with ductile connections including the reinforcing steel that would yield prior to crushing of the concrete. The body or mechanical parts of the connection (e.g., plates, welds, etc.) must have sufficient strength to permit development of 1.5fy in the reinforcing steel.

72. Seismic Design Category (SDC) D Topped Systems Untopped Systems Not implicitly recognized in ACI 318 - 02 Section 21.2.1.5 permits a system to be used if it is shown by experimental evidence and analysis to be equivalent in strength and toughness to comparable monolithic cast-in-place systems The provisions for precast diaphragms that are included in ACI 318-02 are for topped composite and topped non-composite diaphragms, so untopped diaphragms are implicitly not recognized. Section 21.2.1.5 of ACI 318-02, The provisions for precast diaphragms that are included in ACI 318-02 are for topped composite and topped non-composite diaphragms, so untopped diaphragms are implicitly not recognized. Section 21.2.1.5 of ACI 318-02,

73. SDC D – Topped Systems High strain demand across the joints Reinforcing steel needs to be compatible with this demand Use of larger wire spacing or bars may be needed Mesh in the topping must take the entire shear across the joint. Correct lapping to maintain diaphragm integrity These provisions include systems with the topping composite with the precast components and systems with the topping noncomposite part acting alone. The composite system requirements recognize that connections may be part of the design proportioned and detailed to transfer forces. They require that the interface be “clean, free of laitance, and intentionally roughened.” These provisions include systems with the topping composite with the precast components and systems with the topping noncomposite part acting alone. The composite system requirements recognize that connections may be part of the design proportioned and detailed to transfer forces. They require that the interface be “clean, free of laitance, and intentionally roughened.”

74. SDC D – Topped Systems Specific provisions in ACI 318-02 Chord steel determined from flexural analysis Shear strength based entirely on reinforcement crossing the joint: Vn = Acv·rn·fy Where Acv = thickness of the topping slab ?n = steel ratio of the reinforcement These provisions include systems with the topping composite with the precast components and systems with the topping noncomposite part acting alone. The composite system requirements recognize that connections may be part of the design proportioned and detailed to transfer forces. They require that the interface be “clean, free of laitance, and intentionally roughened.” These provisions include systems with the topping composite with the precast components and systems with the topping noncomposite part acting alone. The composite system requirements recognize that connections may be part of the design proportioned and detailed to transfer forces. They require that the interface be “clean, free of laitance, and intentionally roughened.”

75. SDC D – Topped Systems ACI 318-02 minimum spacing requirement of 10 in Diaphragm f -factor = vertical element fshear -factor May result in f = 0.6, based on ACI 318-02 Section 9.3.4 Diaphragm phi-factor must be no greater than that used in the shear design of the supporting vertical elements (columns or walls). Diaphragm phi-factor must be no greater than that used in the shear design of the supporting vertical elements (columns or walls).

76. Questions?