- Date:20 Nov 2020
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6 1 2 5 Yield strength of the reinforcement fy shall not be taken more than 550 N mm2. As per Art 8 of BDS 1313 1991 Ref 3 the tensile strength of any bar shall be greater than. the actual yield strength measured in the tensile test by at least 15 for grades 250 275 350. and 400 and at least 10 for grade 500,3 0 Provision in ACI Code Ref 4. The ACI Code allows the deformed reinforcement as given in Art 3 5 3 of the Code. 3 5 3 Deformed reinforcement, 3 5 3 1 Deformed reinforcing bars shall conform to the requirements for deformed bars in. one of the following specifications,a Carbon steel ASTM A615 Ref 5. b Low alloy steel ASTM A706 Ref 6,c Stainless steel ASTM A955. d Rail steel and axle steel ASTM A996 Bars from rail steel shall be Type R. ASTM A615 A615 96a specifies bars of three minimum yield levels namely 40 000 psi. 300 MPA 60 000 psi 420 MPA and 75000 psi 520 MPa designated as Grade 40 300. Grade 60 420 and Grade 75 520 respectively The material as represented by the test. specimen shall conform to the requirements for tensile properties prescribed in Table 1. Summary of minimum ASTM strength requirements Table 1. Minimum Tensile,ASTM Minimum Yield,Product Designation Strength psi.

Specification Strength psi MPa, Reinforcing bars A615 Grade 40 40 000 280 60 000 420. Grade 60 60 000 420 90 000 620,Grade 75 75 000 520 100 000 690. A706 Grade 60 60 000 420 80 000 550 a,78 000 540,A996 Grade 40 40 000 280 60 000 420. Grade 50 50 000 350 80 000 550,Grade 60 60 000 420 90 000 620. a But not less then 1 25 times the actual yield strength. 3 5 3 2 Deformed reinforcing bars shall conform to one of the ASTM specifications listed. in 3 5 3 1 except that for bars with fy exceeding 60 000 psi the yield strength shall be taken. as the stress corresponding to a strain of 0 35 percent The values of fy and fyt used in design. calculations shall not exceed 80 000 psi except for prestressing steel and for transverse. reinforcement in 10 9 3 and 21 1 5 4, 10 9 3 Volumetric spiral reinforcement ratio s shall be not less than the value given by.

where the value of fyt used in Eq 10 5 shall not exceed 100 000 psi For fyt greater than. 60 000 psi lap splices according to 7 10 4 5 a shall not be used. 21 1 5 4 The value of fyt used to compute the amount of confinement reinforcement shall. not exceed 100 000 psi, The ACI Commentary stats that ASTM A615 includes provisions for Grade 75 bars in sizes. No 6 through 18 The 0 35 percent strain limit is necessary to ensure that the assumption of. an elasto plastic stress strain curve in 10 2 4 will not lead to unconservative values of the. member strength, 3 1 ACI Code Provisions for Minimum Slab Thickness. ACI code 9 5 2 1 specifies the minimum thickness of the non pre stressed one way slabs. using Grade 60 reinforcement as given in Table 9 5 a. 9 5 2 1 Minimum thickness stipulated in Table 9 5 a shall apply for one way construction. not supporting or attached to partitions or other construction likely to be damaged by large. deflections unless computation of deflection indicates a lesser thickness can be used without. adverse effects, 9 5 3 2 For slabs without interior beams spanning between the supports and having a ratio. of long to short span not greater than 2 the minimum thickness shall be in accordance with. the provisions of Table 9 5 c and shall not be less than the following values. a Slabs without drop panels 5 in,b Slabs with drop panels 4 in. 9 5 3 3 For slabs with beams spanning between the supports on all sides the minimum. thickness h shall be as follows, a For m equal to or less than 0 2 the provisions of 9 5 3 2 shall apply.

b For m greater than 0 2 but not greater than 2 0 h shall not be less than. and not less than 5 in,c For m greater than 2 0 h shall not be less than. and not less than 3 5 in, d At discontinuous edges an edge beam shall be provided with a stiffness ratio m not less. or the minimum thickness required by Eq 9 12 or 9 13 shall be increased by at least 10. percent in the panel with a discontinuous edge, Term ln in b and c is length of clear span in long direction measured face to face of. beams Term in b and c is ratio of clear spans in long to short direction of slab. 3 2 ACI Code Provisions for Minimum Reinforcement, 10 5 4 For structural slabs and footings of uniform thickness As min in the direction of. the span shall be the same as that required by 7 12 2 1 Maximum spacing of this. reinforcement shall not exceed three times the thickness nor 18 in. 7 12 2 1 Area of shrinkage and temperature reinforcement shall provide at least the. following ratios of reinforcement area to gross concrete area but not less than 0 0014. a Slabs where Grade 40 or 50,deformed bars are used 0 0020.

b Slabs where Grade 60,deformed bars or welded wire. reinforcement are used 0 0018,c Slabs where reinforcement. with yield stress exceeding 60 000 psi measured at a yield strain of. 0 0018 X 60 000,0 35 percent is used, 7 12 2 2 Shrinkage and temperature reinforcement shall be spaced not farther apart. than five times the slab thickness nor farther apart than 18 in. 3 3 ACI Code Provisions for Seismic Resistance, 21 1 4 2 Specified compressive strength of concrete f c shall be not less than. 21 1 4 3 Specified compressive strength of lightweight concrete f c shall not. exceed 5000 psi unless demonstrated by experimental evidence that structural. members made with that lightweight concrete provide strength and toughness equal to. or exceeding those of comparable members made with normal weight concrete of the. same strength, 21 1 5 2 Deformed reinforcement resisting earthquake induced flexural and axial.

forces in frame members structural walls and coupling beams shall comply with. ASTM A706 ASTM A615 Grades 40 and 60 reinforcement shall be permitted in. these members if, a The actual yield strength based on mill tests does not exceed fy by more than. 18 000 psi and b The ratio of the actual tensile strength to the actual yield strength. is not less than 1 25, 21 1 5 4 The value of fyt used to compute the amount of confinement. reinforcement shall not exceed 100 000 psi, 21 1 5 5 The value of fy or fyt used in design of shear reinforcement shall conform. 11 4 2 The values of fy and fyt used in design of shear reinforcement shall not. exceed 60 000 psi except the value shall not exceed 80 000 psi for welded deformed. wire reinforcement, ACI commentary states that Limiting the values of fy and fyt used in design of shear. reinforcement to 60 000 psi provides a control on diagonal crack width In the 1995. Code the limitation of 60 000 psi for shear reinforcement was raised to 80 000 psi for. welded deformed wire reinforcement Research has indicated that the performance of. higher strength steels as shear reinforcement has been satisfactory In particular. full scale beam tests described in Reference 11 19 indicated that the widths of. inclined shear cracks at service load levels were less for beams reinforced with. smaller diameter welded deformed wire reinforcement cages designed on the basis of. a yield strength of 75 ksi than beams reinforced with deformed Grade 60 stirrups. 4 0 Provision in British European Standard BS 4449 prEN 100800 Ref 7. 4 1 Properties of Reinforcement in British European Standard BS EN. Current British Standards for reinforcement are BS 4449 1988 bars and BS 4483 1985. welded fabric It is envisaged that when EN 10080 currently in draft form as pr EN 10080. is published Grade 500 bars and fabric will supersede Grade 460 The differences between. the current British Standards and pr EN 10080 are summarized in Table 2. Table 2 differences between the current British Standards and pr EN 10080. Property BS 4449 and BS 4483 prEN 10080, Specified characteristic yield Grade 460 N mm2 500 N mm2.

strength Grade 250 N mm2 not included,Bond strength for Deformed Type 2 High bond. Ribbed bars wires Deformed Type 1 Not included,Indented wires Plain rounds Not included. Plain bars wires, Ductility class now defined Not covered Class H or Class N this may. as elongation at maximum be, load and ultimate to yield deleted in the final version. strength ratio see note, NOTE All ribbed bars and all Grade 250 bars may be assumed to be Class H Ribbed wire.

welded fabric may be assumed to be available in Class H in wire sizes of 6 mm or over Plain. or indented wire welded fabric may be assumed to be available in Class N In design where. plastic analysis or moment distribution over 15 is used it is essential to specify ductility. class H as defined in prEN 10080 since this parameter is not covered by BS 4449 and BS. 4 2 Provision for Column in EN Code Ref 7, The Code provisions for column design are given below. 5 4 1 Columns, This clause deals with columns for which the larger dimension b is not greater than 4 times. the smaller dimension h,5 4 1 1 Minimum dimensions. 1 The minimum permissible transverse dimension of a column cross section is. 200 mm for columns of solid section cast in situ vertically. 140 mm for precast columns cast horizontally,5 4 1 2 Longitudinal and transverse reinforcement. 5 4 1 2 1 Longitudinal reinforcement, 1 Bars should have a diameter of not less than 12 mm.

2 The minimum amount of total longitudinal reinforcement As min should be derived from. the following condition, fyd is the design yield strength of the reinforcement. NSd is the design axial compression force,Ac is the cross section of the concrete. 3 Even at laps the area of reinforcement should not exceed the upper limit 0 08 Ac. 4 The longitudinal bars should be distributed around the periphery of the section For. columns having a polygonal cross section at least one bar shall be placed at each corner For. columns of circular cross section the minimum number of bars is 6. 5 4 1 2 2 Transverse reinforcement, 1 The diameter of the transverse reinforcement links loops or helical spiral. reinforcement should not be less than 6 mm or one quarter of the maximum. diameter of the longitudinal bars whichever is the greater the diameter of the wires of. welded mesh fabric for transverse reinforcement should not be less than 5 mm. 2 The transverse reinforcement should be adequately anchored. 3 The spacing of the transverse reinforcement along the column should not exceed the. lesser of the following three distances, 12 times the minimum diameter of the longitudinal bars. the least dimension of the column,4 The spacing should be reduced by a factor 0 6.

i in sections located above and below a beam or slab over a height equal to the larger. dimension of the column cross section, ii near lapped joints if the maximum diameter of the longitudinal bars is greater than. 5 Where the direction of the longitudinal bars changes e g at changes in column size. the spacing of transverse reinforcement should be calculated while taking account of. the lateral forces involved, 6 Every longitudinal bar or group of longitudinal bars placed in a corner should be held. by transverse reinforcement, 7 A maximum of 5 bars in or close to each corner can be secured against buckling by. any one set of transverse reinforcement,4 2 Design Provision for Beams in EN code. 5 4 2 1 Longitudinal reinforcement, 5 4 2 1 1 Minimum and maximum reinforcement percentage.

1 The effective cross sectional area of the longitudinal tensile reinforcement should be not. less than that required to control cracking see 4 4 2 nor less than. Where bt denotes the mean width of the tension zone for a T beam with the flanges in. compression only the width of the web is taken into account in calculating the value of bt. Sections containing less reinforcement than that given by Equation 5 14 should be. considered as unreinforced, 2 The cross sectional areas of the tension reinforcement and of the compression. reinforcement should not be greater than 0 04 Ac other than at laps. 4 3 Design Provision for Cast in Situ Solid Slabs in EN code. 5 4 3 1 Minimum thickness, 1 For a solid slab the absolute minimum thickness is 50 mm. 5 4 3 2 Flexural reinforcement,5 4 3 2 1 General, 1 For the detailing of the main reinforcement 5 4 2 1 applies. 2 Secondary transverse reinforcement should be provided in one way slabs generally this. secondary transverse reinforcement should be at least 20 of the principal reinforcement. 3 5 4 2 1 1 1 and 2 give the minimum and the maximum steel percentages in the main. 4 The maximum spacing of the bars is as follows, For the principal reinforcement 1 5h 350 mm where h denotes the total depth of the. For the secondary reinforcement 2 5 h 400 mm,5 4 3 2 2 Reinforcement in slabs near supports.

1 In slabs half the calculated span reinforcement should continue up to the support and be. anchored therein, 2 Where partial fixity occurs along one side of slab but is not taken into account in the. analysis the top reinforcement should be capable of resisting not less than one quarter of the. maximum moment in the adjacent span this reinforcement should be provided along a length. of not less than 0 2 times the adjacent span measured from the inner face of the support. 5 4 3 2 3 Corner reinforcement, 1 If the detailing arrangements at a support are such that lifting of the slab at a corner is. restrained suitable reinforcement should be provided. 5 4 3 2 4 Reinforcement at the free edges, 1 Along a free unsupported edge a slab should normally contain longitudinal and. Most steel used for reinforcement is highly ductile in nature Its usable strength is its yield strength as this stress condition initiates such a magnitude of deformation into the plastic yielding range of the steel that major cracking will occur in the concrete Since the yield strength of the steel is quite clearly defined and controlled this establishes a very precise reference in

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