Codes and Standards. Steel-Reuse Information Paper No.4. Action Plan 2000 on Climate Change

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1 Steel-Reuse Information Paper No.4 Codes and Standards Action Plan 2000 on Climate Change FACILITATING GREATER REUSE AND RECYCLING OF STRUCTURAL STEEL IN THE CONSTRUCTION AND DEMOLITION PROCESS

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5 APPENDIX: Research notes Structural steel standards C.E.S.A. S Steel Structures for Buildings until 1948 Composite construction allowed Type-A and Type-B C.E.S.A.-S39: Mild structural steel C.E.S.A.-S40: Medium structural steel Table 3 Steel Properties. (from C.E.S.A. S ) Steel type Chemical Analysis Yield stress (psi) Tensile strength (psi) Elongation 8 gauge (%) 60,000 72, E6/(tensile strength) 2 gauge (%) Mild Medium P acid P basic S Cu , min 0.5 of tensile strength Standards Material Properties after 1950: CSA-G 40-1: General requirements for delivery of rolled steel plates, shapes and bars for structural use CSA-G 40-2: Structural steel rivets CSA-G 40-3: Mild structural steel CSA-G 40-4: Medium structural steel CSA-G 40-5: Carbon steel plates of structural quality, plates 2 and under in thickness CSA-G 40-6: Structural silicon steel General notes: All revised and reissued in 1959; G40-1 reissued in 1959 and last revised in 1963 G has section headings Ladle analysis of molten steel from each heat of open-hearth or electric furnace is required by the Manufacturer to determine the percentage of carbon, manganese, phosphorous (P) and sulphur (S); of copper when copper (Cu) steel specifies; any other elements specified or restricted by the applicable specifications. Check analysis by the purchaser

6 Manufacturing process: open hearth or electric furnace; basic oxygen process added in 1959 Marking of steel required, typically of each piece but how to be done is vague (die stamp is referred to for plates). Tensile test and bend test (cold steel bent through 180 without cracking on outside; ratio of inside diameter to thickness specified) are prescribed; two of each per each heat. Speed of loading for loads over one half of the yield is defined. The test specimen is either flat bar 9 long (8 gauge length) of actual material thickness or greater thickness than 1.5 when ¾ thickness can be used or 2.5 long (2 gauge length) rod test can be done. G : Structural Steel for Locomotives and Cars change from mild steel previously used. G : Steel Sheet Piling introduced. Table 4 Steel Properties. (from G40 series 1959) Steel type Mild Medium Carbon plates Silicon steel * Chemical* Analysis Yield stress (psi) P acid P basic S Cu P acid P basic S Cu P acid P basic S Cu C P acid P basic S Silicon 27, Tensile strength (psi) 50,000 62,000 Elongation 8 gauge (%) 2 gauge (%) ,000 60,000 72, Grade A 24,000 Grade B 27,000 Grade C 30,000 Grade D 33,000 45, , , , ,000 80,000 95, Based on ladle analysis G , Structural steel for locomotives and cars G , Low and Intermediate tensile strength carbon steel plates of structural quality. Plates 2inches and under in thickness

7 CSA G : General requirements for delivery of steel plates, shapes, sheet piling and bars, for structural use Major differences in comparison with 1959 edition: Number of tests required is more precisely defined if there is a variation in tests from different heats or when the product size is less than 50 tons. It deals more elaborately with steel marking, especially for rolled sections which should be hot die stamped or embossed along the length of the web section of each piece or cold die stamped at one end of the web section of each piece. Remarking is required of all unmarked pieces removed from bundles and pieces cut from marked pieces. Colour marking is introduced (reference to ASTM A36). CSA G : Structural steels with improved resistance to brittle fracture This standard introduced three different grades of steel, namely A, B and C with the same strength but different chemical composition and different impact tests results (Grade A suitable for above zero F conditions, B for moderate cold temperatures and C for severe cold temperatures -25F to -60F). The maximum thickness of material covered by this Standard is 1.5 inches. The minimum yield strength is 40,000 psi for thicknesses up to 5/8 (38,000 psi for thickness between 5/8 and 1 and 36,000 psi for over 1 thickness). The tensile strength for all grades is between 65,000 and 85,000 psi. The thickness is related to web thickness for rolled sections. The minimum elongation in 8 inches is 20%. Marking of steel should be in accordance with G40.1 with colour marking as follows: Grade A: primary white plus secondary red Grade B: white Grade C: primary white plus secondary yellow Welding for surface repair should be done using low hydrogen electrodes E60XX or E70XX. CSA G : General purpose steel This new standard covers steel plates, shapes and bars used for riveted, bolted or welded connections in the structural field. It covers materials up to 2.5 inches thick. Steel can be manufactured by either open hearth, electric furnace, or the basic oxygen process, with material over 1.5 inches thick required to be made using a fine grain steelmaking practice. Table 5 Steel composition. (from G40.12) Steel type General Purpose Structural Steel * + Chemical* Analysis Max. C P S M Si+ Yield stress (psi) Tensile strength (psi) 62,000 Elongation 8 gauge (%) 2 gauge (%) 0.22 (0.25) 44, for thicknesses (40,000 for 0.04 (0.05) >1.5 thickness > (0.06) 1.50 (1.55) ( ) First value is from ladle analysis; value in the bracket from check analysis. Applies to material over 7/8 thick.

8 Colour identifying this steel is green. CSA G40 series G40.3, originally mild structural steel is not included. G and subsequently revised is referenced here. No change in properties from 1950 version except in chemical composition acid and basic phosphorus is deleted and replaced by the maximum percentage of phosphorus of from ladle analysis and from check analysis. The colour marking for this steel is orange. G40.6 is withdrawn Structural shapes were required to be embossed at intervals along the length of each structural member with the producer s name or brand. Color marking scheme introduced. CSA G : General requirements for rolled or welded structural quality steel This new standard defines products and processes, chemical composition, testing (types, specimens, method and frequency), defects, tolerances and their repair and markings. It applies to all types of steels described in G Section 15 deals with welded shapes which in turn refers to CSA W59.1 for welding specification. CSA G : Structural quality steels This is a new standard dealing with six types of structural quality plates, shapes, and bars for general construction and engineering purposes. It is to be used in conjunction with G , General requirements for rolled or welded structural quality steel. Standards G , G , G and G are referred to in this standard. It introduces different type of steel as described below: Type G General Construction Steel: meets the minimum strength, chemical composition may not meet welding under normal field condition or controlled shop conditions. Bolted application. Type W Weldable Steels: meet the minimum strength requirements. Suitable for welded construction where notch toughness at low temperature is not of a prime importance. Application in buildings, compression members of bridges. Type T Weldable Low Temperature Steels: used where the notch toughness at low temperature is a prime consideration, eg. Tension members of bridges. Type R Atmospheric Corrosion Resistant Structural Steel: these steels have corrosion resistance 4-times of regular carbon steels. Copper content not exceeding 0.02 percent. Suitable for exposed, unpainted application. Weldable, similar to type W. Type A - Atmospheric Corrosion Resistant Structural Steel with Improved Low Temperature Properties: similar to type R but has an improved notch toughness at low temperature. Type Q Quenched and Tempered Low Alloy Steel Plate: exhibits a very high yield strength and good resistance to brittle fracture. May be weldable, but caution should be exercised so that the heat affected zone does not impact adversely its properties. Application in bridges.

9 Table 6 Steel types and grades (reproduced form G ) Type G W T R A Q * Yield Strength, Ksi G 33W 38W 42W* 38T 44 44W 44T 50 50G 50W 50T 50R 50A 55 55W* 55T* 60 60G 60W 60T W 70T 60A 100Q Available in hollow sections only. Plates, bars and structural shapes are available in all grades except 42, 55 and 100. The chemical composition and tensile strength tests are conducted on all type. In addition to these tests, grades T,A and Q have impact tests and grain size tests. The steel manufacturing process is one of the following, basic open hearth, basic electric furnace or basic oxygen process. Special delivery conditions such as stress relieved, annealed, normalized can be specified. Chemical and mechanical properties are given. The appendix contains the table of equivalencies with ASTM, BS and ISO. CSA G : General requirements for rolled or welded structural quality steel This is a new edited version of 1973 standard. The references, text and tables revised but there are no significant differences in comparison with the previous standard. Amended in 1979 and CSA G : Structural quality steels There are no changes to types but grade 42 was eliminated and grade 33 is only available for type G and introduces grade 70A. Revisions published in1980. CSA G40.20-M1978: General requirements for rolled or welded structural quality steel (SI units) This is a new edition of CSA G which is in metric units. CSA G : Structural quality steels This is a new addition of CSA G which is in metric units. CAN3-G40.20-M81: General requirements for rolled or welded structural quality steel This is the second edition of this Standard published originally in1978. Revised and re-published in 1987and CAN3- G40.21-M81: Structural quality steels This is the second metric edition of this standard. It includes revisions to the imperial version of the standard. Revised and re-published in 1987and CAN/CSA G , General Requirements for Rolled or Welded Structural Quality Steel This is the third edition of this standard which was originally published in It includes all amendments published so far as well as amendments approved but not released. This Standard is in imperial units.

10 CSA G40.20/G : General requirements for rolled or welded structural quality steel/ structural quality steel CSA G40.20/G : General requirements for rolled or welded structural quality steel/ structural quality steel CAN/CSA-S6-00: Canadian highway bridge code Section 14.6 deals with the strength determination of existing bridge structures. According to this clause, the material strength can be determined adopting one of the following methods: 1. Review of original structural drawings and documents (the specified minimum yield strength of steel, compressive strength of concrete, yield strength of reinforcement). The values of yield strength from mill certificates should not be used but the guaranteed minimum strength for the steel specified should be used. 2. Test of samples from the bridge or its components. Samples should not compromise the structural stability, or integrity of the member. Location of each sample and its orientation should be recorded and any other information which may be useful when interpreting the test results. The test results should be evaluated and converted to the nominal material strength using A14.1 or other Approved method. See below. 3. Estimation by considering the date of construction. In the absence of more specific information, S6 recommends the use of the following values: Table 7 Default steel strength values (from CAN/CSA-S6-00) Date of bridge construction Before After 1975 Specified Fy, MPa Specified Fu, MPa Other approved methods. Equivalent material strength from tests Testing in accordance with CAN/ CSA-G40.20-M. At least three specimens should be tested. The yield strength is recorded for each test; if the coupon was taken from the flange, then its yield strength cam be increased by a factor of fy = (fy average 28)exp(-1.3ksV), where fy is yield strength to be used in the design check fy average is the average yield stress from the tests V is the coefficient of variation ks is the modification factor for coefficient of variation depend on number of strength tests n (see Table 8 below)

11 Table 8 Coefficient of Variation Modification Factors ks (from CAN/CSA-S6-00) n or more ks Resistance of steel members: There is an Adjustment Factor U which modifies the material factor. U varies from 1.00 for flexure, to 0.87 for shear, 1.01 for tension and compression, 1.27 for bolts and 1.32 for welds. National Building Codes First National Building Code, 1941 The NBC 1941 requires that the alteration and repair of an existing building in access of 50% of the assessed value must bring the entire building to its requirements for new construction. Change in the use of an existing building results in the need for entire building to comply with the requirements for new construction. The exemption applies to change in occupancy for which it can be demonstrated that the existing structure is capable of supporting new occupancy with loading described in Section 3.6. If only portion of a building has a change in occupancy, only that part of the building must be brought to the codes standards, provided there is a separation between the tow parts. Additions greater than 50% of the area of the existing building must have fire separation complying with a special occupancy separation (cl ) unless the existing building, addition and alterations are in compliance with the new code. Structural alteration shall be made to conform to the standards for new buildings. But the extent of such work is to be determined by the authority having jurisdiction. New materials and methods of construction are permitted provided their suitability and working stresses determined by a publicly owned or recognized laboratory are approved by authority having jurisdiction. Steel Medium structural steel conforms to C.E.S.A. S Mild structural steel conforms to C.E.S.A. S

12 Special steels conform to specifications approved by the authority having jurisdiction Unidentified structural steel is required to be tested by an approved laboratory in accordance with A.S.T.M. Standard E8-40T, Method of Tension Testing of Metallic Materials. Mild steel: the unit working stress permitted shall be 90% of those permitted for Medium Structural Steel. Unidentified structural steel: the unit working stress shall not exceed 6/10 of the yield point stress determined in accordance with A.S.T.M. Standard E8-40T, but in no case shall the stresses exceed those for mild structural steel. Loading Floor loads: (in pounds per square foot) Sleeping rooms or domestic rooms 40 Office 50 Corridors in hotels, hospitals 50 Corridors in public buildings 100 Assembly halls with fixed seating 60 Public spaces, dance halls, grandstands 100 Retail shops and stores 100 Wholesale shops and stores 125 Factories 125 Garages for passenger cars 75 Garages for trucks and busses 150 Sidewalks, driveways 250 Reduction of live load: Beams and girders: 15% when area supported by a member exceeds 200 square feet Columns, piers, walls, and foundation: the percentage reduction given in Table 1 (Section 3.6) and it is related to area supported (indirectly as the table deals with number of floors) and type of loading. Combination of wind and live load: for consideration of stresses in a structure and on the foundation from a combination of dead, live and wind, the assumed live load on floors can be reduced by one-half, provided the stresses or bearing pressure are not less than those resulting from a combination of dead and live loads. Ceiling load: 10 psf; ceiling joists must be able to support this load Snow load L: Roof with slope 20 or less shall be designed for snow load of 20 to 40 psf depending on the location. L = S + R,

13 Where: L is snow load S is sum of average snow falls in January, February and March, in inches over number of years R is sum of average rain falls in January, February and March, in inches over number of years L (in) Live load due to snow (psf) Less than More than Roofs with slopes in excess of 20, shall be designed for snow load L1 L1 = L [ (α 20)] Minimum total load on roof member for slopes less than 20 and area less than 500 sqft shall be designed for 50 psf (wind + snow) but excluding wind. Wind loads: On vertical surfaces: Wind pressure: 0 to 300 ft 20 psf Over 300 ft increase by lb/ft of height On plane sloping roofs (slopes both ways from the ridge) Windward face: measured normal to the plane of the roof 20 or less -12psf 20 to 30 (1.2 α 36) 30 to 40 (0.3 α 9) 60 9 Leeward face: suction of 9 psf Allowance for internal pressures or suctions: In normally enclosed buildings with percentage of openings n: Normal suction: ( n), or 9 psf, whichever is less Normal pressure: ( n), or 12 psf whichever is less For structures having open sides, e.g., grandstands Open side facing the wind: a pressure 12 psf Close side facing the wind: a suction 9 psf

14 Earthquake loads: The design provisions for every structure located in a region where destructive earthquake is probable (St. Lawrence basin- major shocks and elsewhere in Canada ref. Seismology in Canada Canada Year Book, 1938, pp.27-29): F is a horizontal force applied at structures centre of gravity W is the total dead load C is a constant depends on the soil conditions at the location C = 0.02, where soil allowable pressure more than 2000 psf C = 0.04, where soil allowable pressure less than 2000 psf For components: C = 0.25 for cantilevered parapets, walls, ornamentation, appendages C= 0.05 for bearing walls, curtain walls, enclosure walls, panel walls. The NBC 1953 This code is set up a set of by-law requirements. This code has climatic information which includes winter design temperatures (based on 2.5 % - i.e., 2.5% of temperatures fall below the listed value), mean annual total degree-days, min. January temperature, 15 minute rainfall, mean annual precipitation, maximum snow load on a horizontal surface, computed maximum gust speed, winter wind directions, earthquake probability. New materials and methods of construction are permitted provided their suitability and working stresses determined by a publicly owned or recognized laboratory are approved by authority having jurisdiction. Loads: The minimum loads are given. Occupancy loads: No change from the previous code; see Table 3.2. Snow load: Roof with slope 20 or less shall be designed for the uniformly distributed snow load L obtained from Chart 8, Part 2 of this NBC. For roofs with a slope x greater than 20, the snow load L1 shall be determined as follows: L1 = L [ (x 20)] The code suggests that loads in excess of those given may occur, where the following conditions are present, the shape, differences in roof levels, insulating qualities or orientation of a building or proximity to other buildings. No provisions for snow accumulation given. Rain: Load resulting from 24 hour rain accumulation on the roof should be used.

15 Wind: Structures of buildings less than 50 ft in height and where adequate transverse shear resistance is provided by walls or bracing members to which wind load is transferred by floor or roof diaphragm do not need to be designed for wind if approved. Calculation of wind load P: p = Cs (Ch V30)2, { or = Cs (p) where p is from Table 4.1.A.1} where Cs is coefficient consisting of the sum of appropriate coefficient from Table together with appropriate internal pressure factors. Ch is velocity height coefficient, Ch = (Hh/H30)1/7 for h up to 1000 ft. Internal pressures coefficient: One side open: Normal air infiltration: Wind overturning moment shall not exceed 75% of the moment of stability resulting from the dead load of the building, unless the building or structure is anchored to resist the excess overturning moment. Earthquake In earthquake zones (see Chart 11 of Part 2) all buildings with the exception of non-combustible construction Group C Division 2 One- or two-family dwellings must be designed to resist the horizontal force F applied in a horizontal direction at each floor or roof level. F = CW, Where: C is the numerical constant from Table C = 0.15/ (N + 4.5), where N is number of storeys There were three zones assigned: Zone 1 C Zone 2 2C Zone 3 4C W is the total dead load (live load should be included for warehouses and storage tanks). Steel Structural steel is to conform to CSA G40.4. Mill test reports properly correlated to the materials shall constitute sufficient identity of any material as to specifications. Unidentified structural steel: can be used if approved. Test if required shall be carried by an approved testing laboratory in accordance with CSA G40.1. The test results shall be used to determine the working stresses. The NBC 1953 was revised in In 1965 new addition of the code was issued as the first edition of what was anticipated a five-year cycle.

16 The NBC 1965 It is still intended as by-law which will be accepted by local municipality. Live load There are no changes in live loads due to occupancy or rather loads due to use. There are two live load reduction factors, one ( / A) for buildings used for storage, manufacturing, garage or assembly applied when a member support an area in excess of 900 sq. ft. and another factor ( / A) for any other occupancy when a member supports an area in excess of 200 sq. ft. Minimum loads for railings separating a change in elevation in access of 18 in., 150 lf/ ft laterally and 100 lb/ ft vertically to be considered separately from lateral load. Vibration due to equipment and machinery: it gives the magnification factor for equipment weight or its live load. Snow load It introduces modification of 80% (Cb = 0.8) to ground snow load given in the Supplement 1. Design snow load = Cb x ground snow load Supplement No. 3 gives factors to account for snow accumulation. It also allows reduction of Cb to 0.6 for exposed roofs. The ground snow load contours changed slightly as well as the magnitude of the snow load. Generally, there is no significant change in snow load for most locations. Wind load The minimum design wind load is given in climatic information included in Supplement No.1. This load should be modified for height above 40 ft. Or the following formula can be used: qh = q30 (h/30)1/5 The change in the exponent results in slightly greater values for design wind pressure. The minimum design load acting on a surface is again given as an algebraic pressure difference on both sides of the surface. Assistance with pressure coefficients is provided in Supplement No.3. Rain load There is no change in rain load. Earthquake load Significant changes in the determination of earthquake loading. The minimum base shear V = KW W is total dead load, including storage and weight of equipment and machinery, K = R* C*I*F*S R is the earthquake factor obtained from climatic information in Supplement No.1. It is a measure of earthquake intensity. C is a coefficient which reflects type of construction;

17 C = 0.75 for steel or reinforced concrete framed buildings with moment resisting connections, and sufficiently stiff floors diaphragm, and the frame alone must be able to carry 50% of the design based shear or shear walls reinforced in a ductile manner to carry design shear forces. C = 1.25 for all types of buildings I is importance factor; I = 1.3 for important bldg s. such as hospitals, power plants and large occupancy and 1.0 for the others. F reflects foundation conditions; F = 1.5 for buildings found on highly compressible ground and F = 1.0 for all other soil conditions S reflects number of storeys N is number of storeys S = 0.25/(9 + N) The distribution of the base shear V to shear at Fx each floor is in accordance with the ratio of (floor weight wx x height above the base hx) to the sum of (floor weight x height above the base) for all storeys. Also for the first time the overturning moment at base is given as M = Fx hx. Structural Steel All structural steel should be accompanied by a Certified Mill Test Report, or Manufacturer s certificate. The fabricator shall if requested provide an affidavit confirming that fabricated steel meets the specifications. Unidentified steel should be tested to identify both physical and chemical properties of steel in accordance with G Steel then classified and appropriate allowable unit stress is determined. The NBC 1970 This edition of the code contains for the first time the limit on lateral deformations; storey deflection to storey height of 1/500 and total deflection to total height of 1/500. It introduces T load; load due to contraction or expansion due to temperature changes, shrinkage, moisture, creep or differential settlement. The load combinations which have to be considered in structural engineering design. The load combination factor is introduced for the first tome; 1.0 for combination dead and live; 0.75 for combination of dead with live load and wind or earthquake; 0.65 for combination of dead load with live load and wind or seismic load and temperature. Dead load The weight of permanent equipment and forces due to prestressing are added to the list of dead loads to be considered. Live load There is no significant change in live loads; except more guidance is given to circumstances when live load conditions were not covered. Snow load No significant changes to snow load occurred.

18 Wind load The impact of wind is defined by designed wind pressure p: p = qcecgcp. This approach is similar to current NBC. The mean hourly wind pressures q which are used are not significantly different from