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1 Concrete Resin Bonded and Mechanical Anchors. 2 Purpose: Develop a design procedure for resin bonded and mechanical anchors to be used in the ODOT BDDM.

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Presentation on theme: "1 Concrete Resin Bonded and Mechanical Anchors. 2 Purpose: Develop a design procedure for resin bonded and mechanical anchors to be used in the ODOT BDDM."— Presentation transcript:

1 1 Concrete Resin Bonded and Mechanical Anchors

2 2 Purpose: Develop a design procedure for resin bonded and mechanical anchors to be used in the ODOT BDDM

3 3 Design Codes Used: Mechanical Anchors: American Concrete Institute (ACI) Appendix D of ACI 318-08 (PCI Design Handbook referenced for conformity) Resin Bonded Anchors: International Code Council (ICC) Section AC308

4 4 General Description: Mechanical Anchor: A pre-installed or cast-in-place metal anchor. Pre-installed anchors have headed or hooked ends and are cast in the concrete. Post installed anchors placed in drilled holes and have an expanding mechanism near the bottom of the anchor that applies compressive stress to the surrounding concrete in order to provide tensile resistance of the anchor. Resin Bonded Anchor: A post-installed metal anchor that is bonded to the concrete with an epoxy resin that is injected into the drilled hole after the anchor is placed.

5 5 Mechanical Anchors

6 6 Single Mechanical Anchor Capacities Nominal Tensile Strength φN n > N ua N n is the design tensile strength of the mechanical anchor based on the critical failure mode. N ua is the factored applied tensile load to the mechanical anchor.

7 7 Steel Strength of Anchor in Tension Nsa = (A se,N )(f uta ) A se,N is the effective cross sectional area of the anchor. f uta is the steel tensile strength of the anchor = 1.9f ya but not more than 125,000 psi.

8 8 Concrete Breakout Strength – Single Anchor

9 9 N cb = (A nc /A nc0 )(ψ ed,n )(ψ c,n )(ψ cp,n )(N b ) A nc is the area of the rectangle with sides located 1.50 h ef from the center of the anchor but not beyond the actual edge of concrete. h ef is the effective embedment length of the anchor. A nc0 is the area of the square with the length of each side equal to 3h ef.

10 10 Concrete Breakout Strength – Single Anchor Anc Shall not exceed A nc0. ψ ed,n = 0.7 + 0.3c a,min, ψ ed,n < 1.0 1.5h ef c a,min = the distance from the center of the anchor to the edge of the concrete. ψ c,n = 1.25 for cast-in anchors, and 1.4 for post-installed anchors.

11 11 Concrete Breakout Strength – Single Anchor For post-installed anchors, ψ cp,n = 1.0 if c a,min > c ac ψ cp,n = c a,min if c a,min < c ac c ac ψ cp,n shall not be taken less than 1.5h ef /c ac c ac = 2.5 h ef for undercut anchors c ac = 4 h ef for torque controlled anchors c ac = 4 h ef for displacement controlled anchors

12 12 Concrete Breakout Strength – Single Anchor For cast-in anchors, ψ cp,n = 1.0 ___ N b = (k c )(λ)f c (h ef ) 1.5 k c = 24 for cast-in anchors k c = 17 for post-installed anchors λ = 1.0 for normal weight concrete

13 13 Pullout Strength – Single Cast-in Anchors Only N pn = (ψ c,P )(N P ) ψ c,P = 1.4 for uncracked concrete ψ c,P = 1.0 for cracked concrete N p = 8A brg f c For headed studs or headed bolts Np = 0.9f c e h d a For hooked bolts A brg = Net bearing area of bolt or stud head e h = minimum length of hook in hook bolt d a = anchor diameter

14 14 Blowout Strength – Single Anchor

15 15 Blowout Strength – Single Anchor ____ __ N sb = 160c a1 A brg λf c c a1 = Distance from anchor to nearest edge of concrete A brg = Net bearing area of bolt or stud head λ = 1.0 for normal weight concrete

16 16 Blowout Strength If the distance (c a2 ) from the center of the anchor to the edge of the concrete that is perpendicular to the edge for c a1 is less than 3c a1, the value N sb shall be modified by the factor; [1+ (c a2 / c a1 )]/4 1 < c a2 < 3

17 17 Strength Provided By Reinforcement If reinforcement is provided and is developed on both sides of the breakout surface, the design strength of the reinforcement can be used instead of the concrete breakout strength.

18 18 Group Mechanical Anchors in Tension The following design specifications are from Appendix D of the American Concrete Institute (ACI) Manual of Concrete Practice, 2008, Part 3. General Equation for Mechanical Anchor Tension Capacity for Group Anchors Nominal Tensile Strength φN n > N ua N n is the design tensile strength of the mechanical anchors based on the critical failure mode. N ua is the factored applied tensile load to the mechanical anchors.

19 19 Group Mechanical Anchors in Tension Steel Strength of Anchors in Tension N sa = (n)(A se, N )(f uta ) n = Number of anchors in a group A se,N is the effective cross sectional area of a single anchor. f uta is the steel tensile strength of the anchor = 1.9f ya but not more than 125,000 psi.

20 20 Concrete Breakout Strength in Tension – Group Anchors N cbg = A nc (ψ ec,n )(ψ ed,n )(ψ c,n )(ψ cp,n )N b A nc0 A nc is the area of the rectangle with sides located 1.50 hef from the centerline of the outside anchors of the group but not beyond the actual edge of concrete. A nc shall not exceed nA nc0 where n is the number of tensioned anchors in the group. h ef is the effective embedment length of the anchor. A nc0 is the area of a single anchor failure zone which is a square with the length of each side equal to 3h ef.

21 21 Concrete Breakout Strength in Tension – Group Anchors ___1___ ψ ec,N = 1+ 2e N < 1 3h ef e N = eccentricity of the load on tension anchors ψ ed,n = 0.7 + 0.3c a,min, ψ ed,n < 1.0 1.5h ef c a,min = the distance from the center of the anchor to the edge of the concrete. ψ c,n = 1.25 for cast-in anchors, and 1.4 for post-installed anchors.

22 22 Concrete Breakout Strength in Tension – Group Anchors For post-installed anchors, ψ cp,n = 1.0 if ca, min > c ac ψ cp,n = c a,min if c a,min < c ac c ac ψ cp,n shall not be taken less than 1.5h ef /c ac c ac = 2.5 h ef for undercut anchors c ac = 4 h ef for torque controlled anchors c ac = 4 h ef for displacement controlled anchors

23 23 Concrete Breakout Strength in Tension – Group Anchors For cast-in anchors, ψ cp,n = 1.0 ___ Nb = k c λfc ( h ef )1.5 kc = 24 for cast-in anchors kc = 17 for post-installed anchors λ = 1.0 for normal weight concrete

24 24 Pullout Strength – Cast-in Anchors Only N pn = (ψ c,P )N P N pn = Pullout strength of a single anchor ψ c, P = 1.4 for uncracked concrete ψ c,P = 1.0 for cracked concrete N p = 8A brg f c For headed studs or headed bolts

25 25 Pullout Strength – Cast-in Anchors Only N p = 0.9f c e h d a For hooked bolts A brg = Net bearing area of bolt or stud head e h = minimum length of hook in hook bolt d a = anchor diameter

26 26 Blowout Strength – Group Anchors N sbg = (1+ s/6c a1 ) N sb N sbg is the nominal blowout strength of a single anchor in a group of anchors. s = the distance between the outer anchors along the edge. ___ ___ Nsb = 160c a1 A brg λf c c a1 = Distance from anchor to nearest edge of concrete

27 27 Blowout Strength – Group Anchors A brg = Net bearing area of bolt or stud head λ = 1.0 for normal weight concrete If the distance (c a2 ) from the center of the anchor to the edge of the concrete that is perpendicular to the edge for c a1 is less than 3c a1, the value Nsb shall be modified by the factor; (1+ c a2 )/4 c a1 1 < c a2 < 3

28 28 Strength Provided by Reinforcement If reinforcement is provided and is developed on both sides of the breakout surface, the design strength of the reinforcement can be used instead of the concrete breakout strength.

29 29 Mechanical Anchor – Single Anchor Shear General Equation for Shear Strength of Anchor φV n > V ua V n is the design shear strength of the mechanical anchor based on the critical failure mode. V ua is the factored applied shear load to the mechanical anchor.

30 30 Nominal Steel Shear Strength For cast-in headed stud anchors: V sa = A se,vf uta For post-installed anchors: V sa = 0.6A se,vf uta

31 31 Nominal Steel Shear Strength A se,V = cross-sectional area of anchor in shear f uta = material strength of the anchor = 1.9 f ya but not more than 125,000 psi f ya = the specified yield strength of the anchor material Where anchors are used with built-up grout pads, the nominal strength shall be multiplied by 0.80.

32 32 Concrete Breakout Strength of Anchor in Shear

33 33 Concrete Breakout Strength of Anchor in Shear V cb = A Vc (ψ ed, V )(ψ c,V )(ψ h,V )(V b ) A Vc0 A Vc is the area of the exposed vertical face of the concrete failure section. The maximum area of this surface is equal to 3c a1 x 1.5c a1 = 4.5c a1 2 c a1 is the distance from the centerline of the anchor to the exposed face of concrete. A Vc is limited by the existing edges of concrete that encroach into the fundamental failure area.

34 34 Concrete Breakout Strength of Anchor in Shear C a2 is the distance along the exposed surface from the edge of the concrete to the centerline of the anchor. A Vc0 = 4.5c a1 2 ψ ed,V = 0.70 + 0.30 c a2 < 1.0 1.5c a1 ψ cV = 1.4 for anchors located in a region where analysis shows no concrete cracking at service loads.

35 35 Concrete Breakout Strength of Anchor in Shear ψ cV = 1.0 for anchors in cracked concrete with no supplementary reinforcement or edge reinforcement smaller than a #4 bar. ψ cV = 1.2 for anchors in cracked concrete with reinforcement of a #4 bar or larger between the anchor and the edge of concrete. ψ cV = 1.4 for anchors in cracked concrete with reinforcement of a #4 bar or greater between the anchor and the edge of concrete, and with the reinforcement enclosed within stirrups spaced at no more than 4 inches. ________ ψ h,V = 1.5c a1 / h a > 1.0

36 36 Concrete Breakout Strength of Anchor in Shear h a is the thickness of the member in which the anchor is located, measured parallel to the anchor axis. ___ ___ V b = [7(l e /d a ) 0.2 d a ] λ f c (c a1 ) 1.5 l e = Load bearing length of the anchor for shear d a = Anchor diameter λ = Light weight concrete factor

37 37 Concrete Pryout Strength of Anchor in Shear

38 38 Concrete Pryout Strength of Anchor in Shear V cp = k cp N cb k cp = 1.0 for h ef < 2.50 k cp = 2.0 for h ef > 2.50 N cb = concrete breakout strength in tension for anchor

39 39 Strength Provided By Reinforcement If reinforcement is provided and is developed on both sides of the breakout surface, or encloses the anchor and is developed beyond the breakout surface, the design strength of the reinforcement can be used instead of the concrete breakout strength.

40 40 Mechanical Anchor Group Shear General Equation for Shear Strength of Anchors φV n > V ua V n is the design shear strength of the mechanical anchors based on the critical failure mode. V ua is the factored applied shear load to the mechanical anchors.

41 41 Nominal Steel Shear Strength For cast-in headed stud anchors: V sa = n(A se, V )(f uta ) For post-installed anchors: V sa = n0.6(A se, V )(f uta ) n = number of anchors

42 42 Nominal Steel Shear Strength A se,V = cross-sectional area of anchor in shear f uta = material strength of the anchor = 1.9 f ya but not more than 125,000 psi f ya = the specified yield strength of the anchor material Where anchors are used with built-up grout pads, the nominal strength shall be multiplied by 0.80.

43 43 Concrete Breakout Shear Strength of Anchors V cbg = A Vc (ψ ec,V )(ψ ed,V )(ψ c, V )(ψ h,V )V b A Vc0 A Vc is the area of the exposed vertical face of the concrete failure section. The maximum area of this surface is equal to (3c a1 +s 1 )(1.5c a1 ) c a1 is the distance parallel to the shear force from the centerline of the outside anchors to the exposed face of concrete. s 1 is the spacing between the outside anchors in the group measured parallel to the failure plain.

44 44 Concrete Breakout Shear Strength of Anchors A Vc is limited by the existing edges of concrete that encroach into the fundamental failure area. A Vc0 is the projected failure area for a single anchor A Vc0 = 3c a1 x 1.5c a1 ψ ec,V = 1/[1+ (2e v /3c a1 )] e v = the eccentricity of anchors loaded in shear in the same direction

45 45 Concrete Breakout Shear Strength of Anchors ψ ed,V = 0.70 + 0.30 c a2 < 1.0 1.5c a1 c a2 is the distance perpendicular to the shear force along the exposed concrete surface from the edge of the concrete to the centerline of the nearest anchor. ψ cV = 1.4 for anchors located in a region where analysis shows no concrete cracking at service loads. ψ cV = 1.0 for anchors in cracked concrete with no supplementary reinforcement or edge reinforcement smaller than a #4 bar.

46 46 Concrete Breakout Shear Strength of Anchors ψ cV = 1.2 for anchors in cracked concrete with reinforcement of a #4 bar or larger between the anchor and the edge of concrete. ψ cV = 1.4 for anchors in cracked concrete with reinforcement of a No. 4 bar or greater between the anchor and the edge of concrete, and with the reinforcement enclosed within stirrups spaced at no more than 4 inches. ________ ψ h,V = 1.5c a1 / h a > 1.0 h a is the thickness of the member in which the anchor is located, measured parallel to the anchor axis.

47 47 Concrete Breakout Shear Strength of Anchors ___ ___ V b = [7(l e /d a )0.2 d a ] λ f c (c a1 ) 1.5 l e = Load bearing length of the anchor for shear l e = hef for anchors with constant stiffness over the full length of the embedded section. l e shall be no greater than 8d a d a = Anchor diameter λ = Light weight concrete factor according to ACI 8.6.1

48 48 Concrete Pryout Shear Strength of Anchors V cpg = k cp N cbg k cp = 1.0 for h ef < 2.50 k cp = 2.0 for h ef > 2.50 N cbg = concrete breakout strength in tension for group anchors

49 49 Strength Provided By Reinforcement If reinforcement is provided and is developed on both sides of the breakout surface, or encloses the anchor and is developed beyond the breakout surface, the design strength of the reinforcement can be used instead of the concrete breakout strength.

50 50 Single Resin Bonded Anchor in Tension The following design specifications are from the Acceptance Criteria for Post-Installed Adhesive Anchors in Concrete Elements published by the International Code Council (ICC). These specifications are planned to be incorporated into the 2011 edition of the American Concrete Institute (ACI) Building Code.

51 51 Single Resin Anchor Tensile Strength N a = A Na (ψ ed,Na ) (ψ p,Na )(N a0 ) A Na0 A Na = the actual horizontal base surface area under the resin bonded anchor. It is a rectangle with sides limited to a distance of c cr,Na or c a,min from the anchor which ever is least. c a,min = minimum edge distance c cr,Na = s cr,Na 2 _________ s cr,Na = 20d τ k,uncr /1450 < 3 h ef

52 52 Single Resin Anchor Tensile Strength h ef = embedment depth d = anchor diameter τ k,uncr is the bond strength of the resin based on uncracked concrete. ______ τ k,uncr = k c,uncr h ef f c < Manufacturers value for resin π d kc, uncr = 24

53 53 Single Resin Anchor Tensile Strength A Na0 = (s cr,Na ) 2 = the projected area of failure surface of a single anchor A Na shall not be greater than A Na0. ψ ed,Na = 0.70 + 0.30c a,min < 1.0 c cr,Na ψ p,Na = max(c a,min ; c cr.Na ) c ac ψ p,Na = 1.0 if c a,min > c ac

54 54 Single Resin Anchor Tensile Strength c ac = 1.50 h ef if h ef < 8d d = anchor diameter c ac = h ef 2 + 1.33 h ef if h ef > 8d 48d N a0 = (τ k,uncr )(π)(d)(h ef )

55 55 Group Resin Anchor Tensile Strength Nominal Tensile Strength N a = A na (ψ ed,Na )(ψ g,Na )(ψ ec,Na )(ψ p,Na )N a0 A Na0 A Na = the actual horizontal base surface area under the resin bonded anchor group. It is a rectangle with sides limited to a distance of c cr,Na or c a, min, which ever is least, from a line through the outside rows of anchors c cr,Na = s cr,Na 2

56 56 Group Resin Anchor Tensile Strength _________ s cr,Na = 20d τ k,uncr /1450 < 3 h ef d = anchor diameter τ k,uncr is the bond strength of the resin based on uncracked concrete. ______ τ k,uncr = k c,uncr h ef f c < Manufacturers value for resin πd A Na0 = (s cr,Na ) 2 = the projected area of failure surface of a single anchor

57 57 Group Resin Anchor Tensile Strength A Na shall not be greater than A Na0. ψ ed,Na = 0.70 + 0.30c a,min < 1.0 c cr,Na ψ g,Na = ψ g,Na0 + [ (s/s cr,Na ) 0.5 (1- ψ g,Na0 )] ψ g,Na is the group failure surface factor __ __ ψ g,Na0 = n – [ (n – 1) (τ k,cr / τ k,max,cr ) 1.5 ] > 1.0 n is the number of tension loaded anchors in a group

58 58 Group Resin Anchor Tensile Strength _____ τ k,max,cr = k c,cr h ef f c πd k c,cr = 17 for cracked concrete ψ ec,Na is a modification factor for eccentrically loaded anchor groups. 1 _ ψ ec,Na = 1+ 2e N scr,Na

59 59 Group Resin Anchor Tensile Strength e N is the eccentricity of the load on the group of anchors This equation is valid for e N < s/2 s = Anchor spacing ψ p,Na = max(c a,min ; c cr.Na ) c ac ψ p,Na = 1.0 if c a,min > c ac

60 60 Group Resin Anchor Tensile Strength c ac = 1.50 h ef if h ef < 8d d = anchor diameter h ef = embedment depth c ac = h ef 2 + 1.33 h ef if h ef > 8d 48d c a,min = minimum edge distance N a0 = (τ k,cr )(π)(d)(h ef )

61 61 Single Resin Anchor Shear Strength Nominal Shear Strength V cp = min [ (k cp )(N a ) ; (k cp )(N cb ) ] k cp = 1.0 for h ef < 2.5 in. k cp = 2.0 for h ef > 2.5 in. N a = A Na (ψ ed,Na )(ψ p,Na )N a0 A Na0 A Na = the actual horizontal base surface area under the resin bonded anchor. It is a rectangle with sides limited to a distance of c cr,Na or c a, min from the anchor which ever is least.

62 62 Single Resin Anchor Shear Strength c cr,Na = s cr,Na 2 _________ s cr,Na = 20d τ k,uncr /1450 < 3 h ef h ef = effective embedment depth of anchor d = anchor diameter τ k,uncr is the bond strength of the resin based on uncracked concrete. ______ τ k,uncr = k c,uncr h ef f c < Manufacturers value for resin π d

63 63 Single Resin Anchor Shear Strength k c,uncr = 24 A Na0 = (s cr,Na ) 2 = the projected area of failure surface of a single anchor. A Na shall not be greater than A Na0. ψ ed,Na = 0.70 + 0.30c a,min < 1.0 c cr,Na ψ p,Na = max(c a,min ; c cr.Na ) c ac ψ p,Na = 1.0 if ca,min > c ac

64 64 Single Resin Anchor Shear Strength c ac = 1.50 h ef if h ef < 8d d = anchor diameter h ef = embedment depth c ac = h ef 2 + 1.33 h ef if h ef > 8d 48d c a,min = minimum edge distance N a0 = (τ k,uncr )(π)(d)(h ef ) N cb = A Nc. ψ ed,N. ψ c,N. ψ cp,N.N b A Nc0

65 65 Single Resin Anchor Shear Strength A Nc = is the area of the rectangle with sides located 1.50 h ef from the center of the anchor but not beyond the actual edge of concrete. A nc0 is the area of the square with the length of each side equal to 3h ef. A nc Shall not exceed A nc0. ψ ed,n = 0.7 + 0.3c a,min, ψ ed,n < 1.0 1.5h ef c a,min = the distance from the center of the anchor to the edge of the concrete.

66 66 Single Resin Anchor Shear Strength ψ c,n = 1.25 for cast-in anchors, and 1.4 for post-installed anchors. For post-installed anchors, ψ cp,n = 1.0 if c a,min > c ac ψ cp,n = c a,min if c a,min < c ac c ac ψ cp,n shall not be taken less than 1.5h ef /c ac

67 67 Single Resin Anchor Shear Strength c ac = 2.5 h ef for undercut anchors c ac = 4 h ef for torque controlled anchors c ac = 4 h ef for displacement controlled anchors __ Nb = k c λ f c h ef 1.5 kc = 24 λ = 1.0 for normal weight concrete

68 68 Group Resin Anchor Shear Strength Nominal Shear Strength V cpg = min [ (k cp )(N ag ) ; (k cp )(N cbg ) ] k cp = 1.0 for h ef < 2.5 in. k cp = 2.0 for h ef > 2.5 in. N ag = A na (ψ ed,Na )(ψ g,Na )(ψ ec,Na )(ψ p,Na )N a0 A Na0

69 69 Group Resin Anchor Shear Strength A Na = the actual horizontal base surface area under the resin bonded anchor group. It is a rectangle with sides limited to a distance of c cr,Na or c a,min from the outside rows of anchors, which ever is least. c cr,Na = s cr,Na 2 __________ s cr,Na = 20d τ k,uncr /1450 < 3 h ef h ef = effective embedment depth of anchor d = anchor diameter

70 70 Group Resin Anchor Shear Strength τ k,uncr is the bond strength of the resin based on uncracked concrete. ______ τ k,uncr = k c,uncr h ef f c < Manufacturers value for resin π d k c,uncr = 24 A Na0 = (s cr,Na ) 2 = the projected area of failure surface of a single anchor A Na shall not be greater than nA Na0 where n is the number of anchors in tension in the group.

71 71 Group Resin Anchor Shear Strength ψ ed,Na = 0.70 + 0.30c a,min < 1.0 c cr,Na ψ g,Na = ψ g,Na0 + [(s/s cr,Na ) 0.5 (1- ψ g,Na0 )] __ __ ψ g,Na0 = n – [(n – 1)(τ k,cr /τ k,max,cr ) 1.5 ] > 1.0 s = Anchor spacing τ k,cr = Bond strength in cracked concrete _______ τ k,max,cr = k c,cr (h ef )(f c )

72 72 Group Resin Anchor Shear Strength k c,cr = 17 ψ ec,Na = 1/[1+(2e N /s cr,Na )] ψ p,Na = max(c a,min ; c cr.Na ) c ac ψ p,Na = 1.0 if c a,min > c ac c ac = 1.50 h ef if h ef < 8d d = anchor diameter, h ef = embedment depth

73 73 Group Resin Anchor Shear Strength c ac = h ef 2 + 1.33 h ef if h ef > 8d 48d c a,min = minimum edge distance N a0 = (τ k,uncr )( π )(d)(h ef ) N cbg = A Nc (ψ ec,N )(ψ ed,N )(ψ c,N )(ψ cp,N )N b A Nc0 A Nc = is the area of the rectangle with sides located 1.50 h ef from the center of the anchor but not beyond the actual edge of concrete.

74 74 Group Resin Anchor Shear Strength A nc0 is the area of the square with the length of each side equal to 3h ef. A nc Shall not exceed A nc0. ψ ec,N = 1/[1+(2e N /3h ef )] e N = eccentricity of tension anchors ψ ed,n = 0.7 + 0.3c a,min, ψ ed,n < 1.0 1.5h ef c a,min = the distance from the center of the anchor to the edge of the concrete.

75 75 Group Resin Anchor Shear Strength ψ c,N = 1.4 for post installed anchors ψ cp,n = 1.0 if c a,min > c ac ψ cp,n = c a,min if c a,min < c ac c ac ψ cp,n shall not be taken less than 1.5h ef /c ac _ N b = k c λ f c h ef 1.5 k c = 17 for post-installed anchors λ = 1.0 for normal weight concrete


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