A division of Canam Group

Transcription

1 s and Girders Catalogue A division of Canam Group

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3 TABLE OF CONTENTS Products, services and solutions General information The advantages of using steel joists... 5 Description of a joist girder....5 Definition....5 Components of a joist girder...5 Advantages of joist girders... 6 Steel... 7 Design standards Quality assurance Accessories Material / Metric... 8 Axes convention... 8 Section properties Material / Imperial Axes convention Section properties Bridging...13 Specifications Bridging line requirements / Metric...14 Bridging line requirements / Imperial...15 Spacing for bridging / Metric Spacing for bridging / Imperial Knee braces Material weights Standard details Extensions Maximum duct openings / Metric Maximum duct openings / Imperial Geometry and shapes Standard shape Non-standard shapes Special shapes Minimum and span Shoes Particularities Bearing on concrete or masonry wall Bearing on steel Details Ceiling extension Flush shoe Bolted splice Bottom chord bearing Cantilever joist and joist girder identification Standard connections Surface preparation and paint Paint standards Paint costs Colours s exposed to the elements or corrosive conditions Vibration Steel joist floor vibration comparison Special conditions Special joist deflection Deflection of cantilevered joists Camber...39 Special loads and moments Various types of loads Transfer of axial loads Unbalanced loads Load reduction according to tributary area End moments Gravitational moments Wind moments or joist girder analysis and design s adjacent to more rigid surfaces s with lateral slope Anchors on joists Special joists girder to column connections Bearing reaction Bearing on top of the column Bearing facing the column Bearing facing the column with center reaction Standards CAN/CSA S16-01 standards (16. Open-web steel joists) and CISC commentaries selection tables Metric Imperial girder selection Graphics / Metric Graphics / Imperial girder specifications Information required from the building designer Checklist - joist design essential information checklist Take-off sheet - quotation Sales offices and plant certifications Canam is a trademark of Canam Group Inc.

4 Products, services and solutions Canam specializes in the fabrication of steel joists, joist girders, steel deck, purlins and girts, and welded wide-flange shapes. We also design and fabricate the Murox high performance building system and Econox foldaway portable buildings. Canam offers customers value-added engineering and drafting support, architectural flexibility and customized solutions and services. Another Canam solution, the BuildMaster approach, has redefined the way in which buildings are designed and built by offering a safer, faster and greener process that can reduce field erection time by between 15% and 25%. Factors such as product quality, worksite supervision and construction time are critical in the execution of any project, big or small, and Canam's reputation for reliability simplifies these considerations for customers. In addition to a rigorous jobsite management process that is specifically designed to ensure that deadlines are met, our cutting-edge equipment, skilled employees and high quality products are also key in allowing Canam to keep its promises. Whatever your project, we will meet your requirements while also complying with all applicable building codes. Another aspect of our exceptional service is just-in-time delivery as per customer specifications. To eliminate delays, components are transported by our very own fleet, which stands ready to ensure on-time delivery, regardless of the location. Depending on the region and worksite, Canam can transport components measuring up to 16 ft. (4.9 m) wide and 120 ft. (36.5 m) long. Canam is one of the largest steel joist fabricators in North America. CAUTIONARY STATEMENT Although every effort was made to ensure that the information contained in this catalog is factual and that the numerical values presented herein are consistent with applicable standards, Canam does not assume any responsibility whatsoever for errors or oversights that may result from the use or interpretation of this data. Anyone making use of this catalog assumes all liability arising from such use. All comments and suggestions for improvements to this publication are greatly appreciated and will receive full consideration in future editions. 4

5 General Appuis information sphériques THE ADVANTAGES OF USING STEEL JOISTS Using a steel joist and steel deck system for floor and roof construction has proven itself to be a most advantageous solution. It can result in substantial savings based on: Efficiences of high-strength steel; Speed and ease of erection; Low self-weight of roof and floor construction allowing for smaller columns and foundations than for a concrete structure; Increased bay dimensions, which reduces the number of joists and columns and simplifies building erection; Greater floor plan layout flexibility for the building occupant due to the increased bay dimensions; Maximum ceiling height due to installation of ducts through the joist web system; Easy adaptation to acoustical insulation systems; Floor and roof composition having long-term resistance to fire, as established by the Underwriters Laboratories of Canada (ULC). DESCRIPTION OF A JOIST GIRDER DEFINITION A joist girder is a primary structural component of a building. Generally, it supports floor or roof joists in simple span conditions, or other secondary elements (purlins, wood trusses, etc.) evenly spaced along the length of the joist girder. The loads applied to a spandrel joist girder come from one side, while on an inside bay the loads are applied on either side of the joist girder. COMPONENTS OF A JOIST GIRDER An open web joist girder, or commonly known as a cantruss at Canam, is composed of a top chord and a bottom chord, which are usually parallel to each other. These chords are held in place using vertical and diagonal web members. In conventional construction, a joist girder rests on a column and the bottom chord is held in place horizontally by a stabilizing plate. The standard main components are: 1. Top and bottom chords: two angles back-to-back with a gap varying between 25 mm (1 in.) and 76 mm (3 in.), 2. Diagonals: U-shaped channels or two angles back-to-back, 3. Verticals: U-shaped channels, boxed angles or HSS, 4. Shoes: two angles back-to-back. Vertical Top chord Shoe Diagonal Bottom chord Components of a joist girder 5

6 Appuis General sphériques information ADVANTAGES OF JOIST GIRDERS The use of open web joist girders is widespread in North America, mostly in the United States, for roof construction of commercial and industrial buildings. The joist girders are advantageous compared with conventional load bearing systems composed of beams with a W profile. Here are the various options for supporting systems when designing a steel building: Simple beam Gerber system girder Carrying system Economical factors associated with the specification of joist girders include the following: 1. The steel used in joist girders has a yield strength higher than steel used for shaped or welded beams: 380 MPa (55 ksi) versus 350 MPa (50 ksi). 2. Better cost control for material purchases (angles) on the Canadian market compared with importing the beam sections. 3. Open web joist girders are lighter than the full web beams of the same. 4. The speed and ease of site erection improves jobsite co-ordination. 5. The joist girders can be used to facilitate the installation of ventilation ducts and plumbing as compared to a beam. Beam Mechanical conduits girder Passage of mechanical conduits 6

7 General information L girder s girder Optimal rectangular bay Cold formed angle Hot rolled angle Approximately 1.5 x L If a larger opening is required, a diagonal member can be removed if the top and bottom chord are reinforced. The building designer must consider the following to ensure the economical use of joist girders: 1. Longer spans of joist girders are preferred as this reduces the number of columns inside a building. 2. Greater s reduce the size of the top and bottom chords for increased weight savings. 3. Bay arrangement should be repetitive since designing and fabricating many identical pieces will reduce production costs. 4. Regular joist spacing must be maintained by the building designer by lining up the joists on either side of the joist girders. 5. Rectangular bays are recommended, in a roof or floor system using joist girders and joists, where the longest dimension corresponds to the joist span, while the shortest dimension corresponds to the joist girder span. An optimal rectangular bay would typically have a ratio of joist span to joist girder span of approximately Bearing shoes are used for economical joist girder to column connection, usually 191 mm (7.5 in.) deep, bolted to the top of the column or on a bearing bracket on the web or the flange of the column. STEEL Our joist and joist girder design makes use of high strength steel purchased in accordance with the latest issue of the standards below: Cold formed angles and U-shaped channels: ASTM A1011; Hot rolled angles and round bars: CAN/CSA-G40.20/G DESIGN STANDARDS and joist girder design is based on the latest issue of the design standards in effect: Canada: United States: CAN/CSA S16 01 SJI CAN/CSA S NBCC 2005 QUALITY ASSURANCE Over the years, we have established strict quality standards. All our welders, inspectors, and quality assurance technicians are certified by the Canadian Welding Bureau (CWB). We do visual inspections on 100% of the welded joints and non-destructive testing if required. Distribution Centre I Cornwall, Ontario Notes: This catalog was produced by Canam, a business unit of Canam Group Inc. It is intended for use by engineers, architects, and building contractors working in steel construction. It is a selection tool for our economical steel products. It is also a practical guide for Canam joists and joist girders. Canam reserves the right to change, revise, or withdraw any product or procedure without notice. The information presented in this catalog was prepared according to recognized engineering principles and is for general use. Although every effort has been made to ensure that the information in this catalog is correct and complete, it is possible that errors or oversights may have occurred. The information contained herein should not be used without examination and verification of its applications by a certified professional. 7

8 Accessories MATERIAL METRIC AXES CONVENTION Y Y Y X X X y X x y x Y Y SECTION PROPERTIES Material (in.) Grade (MPa) ROUND AND SQUARE BARS Forming Mass (kg/m) Area (mm 2 ) l (10 3 mm 4 ) r (mm) x Y y x 1/2 350 Hot rolled / Hot rolled /8 350 Hot rolled / Hot rolled /4 350 Hot rolled / Hot rolled /8 350 Hot rolled / Hot rolled Hot rolled /8 350 Hot rolled square 350 Hot rolled U SHAPES Material (in.) (in.) (in.) Grade (MPa) Forming Mass (kg/m) Area (mm 2 ) y (mm) Axis X-X l xx (10 3 mm 4 ) r xx (mm) l yy (10 3 mm 4 ) Axis Y-Y 1 x 5/8 x Cold formed x 0.8 x Cold formed x 0.85 x Cold formed x 1 x Cold formed x 1 x Cold formed x 1.05 x Cold formed x 1.1 x Cold formed /8 x 1.27 x Cold formed /8 x 1 3/8 x Cold formed /8 x 1 3/8 x Cold formed /4 x 1 1/2 x Cold formed /4 x 1 3/4 x Cold formed /8 x 2 x Cold formed r yy (mm) 8

9 Accessories METRIC DOUBLE ANGLES (LONG LEGS BACK-TO-BACK) Material (in.) (in.) (in.) Grade (MPa) Forming Mass (kg/m) Area (mm 2 ) y (mm) Axis X-X r yy with different gaps Axis Z l xx (10 6 mm 4 ) 1 x 1 x Cold formed x 1 x 7/ Hot rolled x 1 x Cold formed x 1 x 1/8 380 Hot rolled /8 x 1 1/8 x Cold formed /8 x 1 1/8 x Cold formed /4 x 1 1/4 x Cold formed /4 x 1 1/4 x 1/8 380 Hot rolled /4 x 1 1/4 x 3/ Hot rolled /8 x 1 3/8 x Cold formed /2 x 1 1/2 x Cold formed /2 x 1 1/2 x 1/8 380 Hot rolled /2 x 1 1/2 x 5/ Hot rolled /2 x 1 1/2 x Cold formed /2 x 1 1/2 x 3/ Hot rolled /8 x 1 5/8 x Cold formed /8 x 1 5/8 x Cold formed /4 x 1 3/4 x Cold formed /4 x 1 3/4 x 5/ Hot rolled /4 x 1 3/4 x Cold formed /4 x 1 3/4 x 3/ Hot rolled /8 x 1 7/8 x Cold formed /8 x 1 7/8 x Cold formed x 2 x Cold formed x 2 x Cold formed x 2 x 3/ Hot rolled x 2 x Cold formed x 2 x 7/ Hot rolled x 2 x 1/4 380 Hot rolled /8 x 2 1/8 x Cold formed /8 x 2 1/8 x Cold formed /8 x 2 1/8 x Cold formed /4 x 2 1/4 x Cold formed /4 x 2 1/4 x Cold formed /8 x 2 3/8 x Cold formed /8 x 2 3/8 x Cold formed /2 x 2 1/2 x Cold formed /2 x 2 1/2 x Cold formed /2 x 2 1/2 x 1/4 380 Hot rolled /2 x 2 1/2 x 5/ Hot rolled /8 x 2 5/8 x Cold formed /4 x 2 3/4 x Cold formed /8 x 2 7/8 x Cold formed x 3 x Cold formed x 2 x 5/ Hot rolled x 3 x 5/ Hot rolled x 3 x 3/8 380 Hot rolled /8 x 3 1/8 x Cold formed /2 x 3 1/2 x 3/8 380 Hot rolled x 3 x 3/8 380 Hot rolled x 4 x 3/8 380 Hot rolled x 3 x 1/2 380 Hot rolled x 4 x 1/2 380 Hot rolled x 4 x 9/ Hot rolled x 3 1/2 x 1/2 350 Hot rolled x 5 x 1/2 380 Hot rolled x 5 x 9/ Hot rolled x 5 x 5/8 380 Hot rolled x 6 x 9/ Hot rolled x 4 x 5/8 350 Hot rolled x 6 x 5/8 380 Hot rolled x 6 x 3/4 300 Hot rolled x 8 x 3/4 300 Hot rolled x 8 x Hot rolled r xx (mm) 12.7 (mm) 19 (mm) 25 (mm) 35 (mm) 45 (mm) 60 (mm) r z (mm) 9

10 Accessories MATERIAL IMPERIAL AXES CONVENTION Y Y Y X X X y X x y x Y Y SECTION PROPERTIES Material (in.) Grade (ksi) ROUND AND SQUARE BARS Forming Mass (plf) Area (in. 2 ) l (in. 4 ) r (in.) x Y y x 1/2 50 Hot rolled /16 50 Hot rolled /8 50 Hot rolled /16 50 Hot rolled /4 50 Hot rolled /16 50 Hot rolled /8 50 Hot rolled /16 50 Hot rolled Hot rolled /8 50 Hot rolled square 50 Hot rolled U SHAPES Material (in.) (in.) (in.) Grade (ksi) Forming Mass (plf) Area (in. 2 ) y (in.) Axis X-X l xx (in. 4 ) r xx (in.) l yy (in. 4 ) Axis Y-Y 1 x 5/8 x Cold formed x 0.8 x Cold formed x 0.85 x Cold formed x 1 x Cold formed x 1 x Cold formed x 1.05 x Cold formed x 1.1 x Cold formed /8 x 1.27 x Cold formed /8 x 1 3/8 x Cold formed /8 x 1 3/8 x Cold formed /4 x 1 1/2 x Cold formed /4 x 1 3/4 x Cold formed /8 x 2 x Cold formed r yy (in.) 10

11 Accessories IMPERIAL DOUBLE ANGLES (LONG LEGS BACK-TO-BACK) Axis X-X r yy with different gaps Axis Z Material Grade Mass Area y l Forming xx r xx 1/2 3/ /8 1 3/4 2 3/8 r z (in.)www (in.) (in.) (ksi) (plf) (in. 2 ) (in.) (in. 4 ) (in.) (in.) (in.) (in.) (in.) (in.) (in.) (in.) 1 x 1 x Cold formed x 1 x 7/64 55 Hot rolled x 1 x Cold formed x 1 x 1/8 55 Hot rolled /8 x 1 1/8 x Cold formed /8 x 1 1/8 x Cold formed /4 x 1 1/4 x Cold formed /4 x 1 1/4 x 1/8 55 Hot rolled /4 x 1 1/4 x 3/16 55 Hot rolled /8 x 1 3/8 x Cold formed /2 x 1 1/2 x Cold formed /2 x 1 1/2 x 1/8 55 Hot rolled /2 x 1 1/2 x 5/32 55 Hot rolled /2 x 1 1/2 x Cold formed /2 x 1 1/2 x 3/16 55 Hot rolled /8 x 1 5/8 x Cold formed /8 x 1 5/8 x Cold formed /4 x 1 3/4 x Cold formed /4 x 1 3/4 x 5/32 55 Hot rolled /4 x 1 3/4 x Cold formed /4 x 1 3/4 x 3/16 55 Hot rolled /8 x 1 7/8 x Cold formed /8 x 1 7/8 x Cold formed x 2 x Cold formed x 2 x Cold formed x 2 x 3/16 55 Hot rolled x 2 x Cold formed x 2 x 7/32 55 Hot rolled x 2 x 1/4 55 Hot rolled /8 x 2 1/8 x Cold formed /8 x 2 1/8 x Cold formed /8 x 2 1/8 x Cold formed /4 x 2 1/4 x Cold formed /4 x 2 1/4 x Cold formed /8 x 2 3/8 x Cold formed /8 x 2 3/8 x Cold formed /2 x 2 1/2 x Cold formed /2 x 2 1/2 x Cold formed /2 x 2 1/2 x 1/4 55 Hot rolled /2 x 2 1/2 x 5/16 55 Hot rolled /8 x 2 5/8 x Cold formed /4 x 2 3/4 x Cold formed /8 x 2 7/8 x Cold formed x 3 x Cold formed x 2 x 5/16 50 Hot rolled x 3 x 5/16 55 Hot rolled x 3 x 3/8 55 Hot rolled /8 x 3 1/8 x Cold formed /2 x 3 1/2 x 3/8 55 Hot rolled x 3 x 3/8 55 Hot rolled x 4 x 3/8 55 Hot rolled x 3 x 1/2 55 Hot rolled x 4 x 1/2 55 Hot rolled x 4 x 9/16 55 Hot rolled x 3 1/2 x 1/2 50 Hot rolled x 5 x 1/2 55 Hot rolled x 5 x 9/16 55 Hot rolled x 5 x 5/8 55 Hot rolled x 6 x 9/16 55 Hot rolled x 4 x 5/8 50 Hot rolled x 6 x 5/8 55 Hot rolled x 6 x 3/4 44 Hot rolled x 8 x 3/4 44 Hot rolled x 8 x 1 44 Hot rolled

12 Accessories Athletic Facility I Terrebonne, Quebec Bombardier Centre I La Pocatière, Quebec Alphonse-Desjardins Sports Complex I Trois-Rivières, Quebec 12

13 Accessories BRIDGING SPECIFICATIONS The CAN/CSA S16-01 standard specifies a bridging system to assure steel joist stability. Some important points to consider are: Maximum slenderness ratio by bridging type; Minimum capacity of the bridging system; Service load criteria; Maximum unsupported lengths for the top and bottom chords of the joist; Erection criteria; Bridging system requirements for special support conditions. The two types of bridging used and their maximum unsupported length are as follows: Horizontal bridging 300 x r z Diagonal bridging 200 x r z The horizontal bridging type is most commonly used to stabilize joists. Attachment of diagonal and horizontal bridging to joist chords with a minimum capacity of 3kN is in accordance with clause of CSA S The selection tables for horizontal and diagonal bridging angles presented herein meet the slenderness and minimum capacity criteria. The bridging system performs two main functions: To assure joist stability during erection by providing lateral support to the top and bottom chords of the joists; To hold the joists in the position shown on the drawings, normally vertical. In general, the bridging must be spaced along the chords so that the laterally unsupported distance does not exceed: Top chord 170 x r yy Bottom chord 240 x r yy For safety reasons, a line of cross bridging is recommended for joists having a span longer than 12.2 m (about 40 ft.). No construction loads shall be placed on the joists until the bridging system is completely installed. Once installed, the steel deck generally offers sufficient rigidity to provide the lateral stability to the top chord. The resistance of decking and joints must be verified by the joist designer to ensure that adequate lateral support is provided to the top chord. For the bottom chord, bridging must be designed with the maximum slenderness ratio criterion of this tension member. If the bottom chord is subject to compression loads, due to uplift forces or other compression causing forces, a system with more bridging lines must be used. If uplift forces are applied to the joist, a line of bridging is required at the first bottom chord panel point at both ends of the joist. The length of horizontal bridging supplied by Canam is based on a maximum lap of 150 mm (6 in.). The ends of the bridging system on a beam or masonry wall must comply with clause of the CAN/CSA S16-01 standard. Certain joist loading conditions require special bracing systems. Note that this reference is to bracing rather than bridging. Members supplied in these cases must meet the criteria of clause 9.2 of CAN/CSA S Two such cases are cantilever joists and perimeter joists that laterally support the top of wind columns. 13

14 Accessories BRIDGING LINE REQUIREMENTS The following tables are a guide to evaluate the number of top and bottom chord bridging lines for a joist having a uniformly distributed load. The number of lines is based upon the maximum allowable spacing between the lines at the top chord. This number can vary with chord angle separation and chord sizes. As previously mentioned, when uplift forces are applied to the joist, additional bridging lines are required near both ends of the bottom chord. METRIC TABLE FOR SELECTING THE NUMBER OF BRIDGING LINES Factored load (kn/m) Service load (kn/m) (m) Legend 0 line 2 lines 4 lines 1 line 3 lines

15 Accessories IMPERIAL TABLE FOR SELECTING THE NUMBER OF BRIDGING LINES (ft.) Factored load (plf) Service load (plf) ,035 1,140 1,245 1,350 1,455 1, , , Legend 0 line 2 lines 4 lines 1 line 3 lines 15

16 Accessories SPACING FOR BRIDGING METRIC MAXIMUM JOIST SPACING (mm) FOR HORIZONTAL BRIDGING Bridging angle size L 1 1/4 x 1 1/4 x L 1 1/2 x 1 1/2 x L 1 5/8 x L 1 3/4 x 1 3/4 x L 2 x 2 x 1/8 L 1 1/2 x 1 1/2 x L 1 3/4 x 1 3/4 x 1/8 L 2 x 2 x ,720 2,240 2,420 2,620 2,970 (mm) MAXIMUM JOIST SPACING (mm) FOR DIAGONAL BRIDGING Bridging angle size L 1 1/4 x 1 1/4 x 0.090* L 1 1/2 x 1 1/2 x L 1 5/8 x L 1 3/4 x 1 3/4 x L 2 x 2 x 1/8 L 1 1/2 x 1 1/2 x L 1 3/4 x 1 3/4 x 1/8 L 2 x 2 x ,420 2,980 3,220 3,490 3, ,420 2,970 3,220 3,480 3, ,410 2,960 3,210 3,480 3, ,400 2,960 3,200 3,470 3, ,390 2,950 3,190 3,460 3, ,380 2,940 3,190 3,450 3, ,370 2,930 3,180 3,450 3, ,350 2,920 3,170 3,440 3, ,340 2,910 3,160 3,430 3, ,320 2,890 3,140 3,420 3, ,300 2,880 3,130 3,400 3, ,270 2,850 3,100 3,380 3,860 1,000 2,220 2,810 3,070 3,350 3,830 1,100 2,170 2,770 3,040 3,320 3,810 1,200 2,120 2,730 3,000 3,280 3,770 1,300 2,680 2,950 3,240 3,740 1,400 2,630 2,910 3,200 3,700 1,500 2,570 2,850 3,150 3,660 1,600 2,510 2,800 3,100 3,620 1,700 2,440 2,740 3,040 3,570 1,800 2,370 2,670 2,980 3, * To use with welded diagonal bridging or bolted diagonal bridging with maximum 10 mm (3/8 in.) bolt diameter. Note: The diagonal bridging must be tied at mid-length.

17 Accessories IMPERIAL MAXIMUM JOIST SPACING (ft.) FOR HORIZONTAL BRIDGING Bridging angle size L 1 1/4 x 1 1/4 x L 1 1/2 x 1 1/2 x L 1 5/8 x L 1 3/4 x 1 3/4 x L 2 x 2 x 1/8 L 1 1/2 x 1 1/2 x L 1 3/4 x 1 3/4 x 1/8 L 2 x 2 x (in.) MAXIMUM JOIST SPACING (ft.) FOR DIAGONAL BRIDGING Bridging angle size L 1 1/4 x 1 1/4 x 0.090* L 1 1/2 x 1 1/2 x L 1 5/8 x L 1 3/4 x 1 3/4 x L 2 x 2 x 1/8 L 1 1/2 x 1 1/2 x L 1 3/4 x 1 3/4 x 1/8 L 2 x 2 x * To use with welded diagonal bridging or bolted diagonal bridging with maximum 10 mm (3/8 in.) bolt diameter. Note: The diagonal bridging must be tied at mid-length. 17

18 Accessories KNEE BRACES To provide lateral support to the bottom chord of the joist girders, knee bracing is used. These knee braces are installed into position where required at joist support locations and generally on both sides of the joist girder. They join the top chord of the joist girder to the bottom chord of the joist as illustrated below. A knee brace selection table is provided based on a maximum allowable slenderness ratio of 200 x r z. In some cases, installation of knee braces can be avoided by extending the bottom chord length of some joists when the joist girder is similar to that of the joist that it supports. When a joist girder is used to support girts instead of joists, the knee brace system may not be recommended. Usually for girt shapes we use cross braces tied at midlength as lateral support to the joist girder when the spacing between joist girders (girts span) is less than 6,000 mm (20 ft.), or when the girt section thickness is smaller than 2.3 mm (3/32 in.). In all other cases, the standard knee brace system may be used. The building designer should take into consideration that the knee brace stabilizing the bottom chord of the joist girder induces loads on the girts at the connection points. TYP. girder girder APPROX. 45 TYP. By Canam By Canam Knee braces - detail 1 Knee braces - detail 2 girder Knee braces - detail 3 METRIC MAXIMUM KNEE BRACE LENGTH L (mm) Brace angle size L 1 1/2 x 1 1/2 x L 2 x 2 x L 2 1/2 x 2 1/2 x 3/16 L 3 x 3 x L 1 1/2 x 1 1/2 x 5/32 L 2 x 2 x 5/32 L 2 1/2 x 2 1/2 x L 3 x 3 x 1/4 L 1 1/2 x 1 1/2 x 3/16 L 2 x 2 x 3/16 L 2 1/2 x 2 1/2 x 1/4 L 3 x 3 x 5/16 1,470 1,990 2,480 2,980 IMPERIAL MAXIMUM KNEE BRACE LENGTH L (ft.) Brace angle size L 1 1/2 x 1 1/2 x L 2 x 2 x L 2 1/2 x 2 1/2 x 3/16 L 3 x 3 x L 1 1/2 x 1 1/2 x 5/32 L 2 x 2 x 5/32 L 2 1/2 x 2 1/2 x L 3 x 3 x 1/4 L 1 1/2 x 1 1/2 x 3/16 L 2 x 2 x 3/16 L 2 1/2 x 2 1/2 x 1/4 L 3 x 3 x 5/

19 Accessories MATERIAL WEIGHTS The tables below can be used as a guide to establish in which direction the joists should be orientated compared to the joist girders for a particular bay area and various total uniform factored loads. They are also a guide for the building designer to evaluate the dead load of joists and joist girders to be used for design. METRIC ESTIMATED SELF-WEIGHT OF JOISTS AND JOIST GIRDERS (kpa) Bay area (m 2 ) / girder ratio Factored uniform load (kpa) (m) J.G. (m) IMPERIAL ESTIMATED SELF-WEIGHT OF JOISTS AND JOIST GIRDERS (psf) Bay area (ft. 2 ) / girder ratio Factored uniform load (psf) / ,100 1/ , , ,600 1/ , , ,200 1/ , , ,700 1/ , , ,200 1/ , , (ft.) J.G. (ft.) 19

20 Accessories The weight of the main materials included in a floor or roof system is reproduced below. The density of certain materials is also indicated. This table allows the designer to quickly evaluate the dead and live loads to specify on drawings and specifications. MASS/WWCES TO USE FOR DESIGN (Using normal density concrete) kg/m 3 kn/m 3 Material pcf 7, Steel 490 2, Aluminum 165 2, Glass (plate) 161 2, Concrete (stone, reinforced) 150 2, Brick (common) Wood (hard or treated) maximum Wood (soft or dry) minimum 22 1, Water (fresh, 4 C) Ice Snow (wet) maximum Snow (dry, packed) maximum Snow (dry, fresh fallen) 8 1, Paint (52% of weight solids) Oils Alcohol Gasoline 42 1, Sand and gravel (wet) 120 kg/m 2 kn/m 2 Material psf Steel deck P-3615 (up to 0.91 mm) Steel deck P-3615 (1.21 to 1.52 mm) Steel deck P-2436 (up to 0.91 mm) Steel deck P-2436 (1.21 to 1.52 mm) Steel deck P-3615 composite (100 mm total slab) Steel deck P-3615 composite (150 mm total slab) Steel deck P-2432 composite (140 mm total slab) Steel deck P-2432 composite (200 mm total slab) Roofing 3 ply asphalt (no gravel) Fiberglass insulation (batts 100 mm) Fiberglass insulation (blown 100 mm) Fiberglass insulation (rigid 100 mm) Urethane (rigid foam 100 mm) Insulating concrete (100 mm) Gypsum wallboard (16 mm) Sprayed fire protection (average) Ducts, pipes, and wiring (average) Plaster on lath/furring (20 mm) Tiled ceiling with suspension and fixtures (average) Hollow core precast (200 mm N.D. no topping) Hollow core precast (300 mm N.D. no topping) Plywood or chipboard (20 mm) Hardwood floor (20 mm) Wood joists 38 mm x 286 mm (400 mm c/c) Carpeting Ceramic (20 mm) on Mortar bed (12 mm) Hollow concrete block 150 mm thick (cells empty) Hollow concrete block 200 mm thick (cells empty) Hollow concrete block 300 mm thick (cells empty) Hollow concrete block 150 mm thick (1 of 4 cells filled) Hollow concrete block 200 mm thick (1 of 4 cells filled) Hollow concrete block 300 mm thick (1 of 4 cells filled)

21 Standard details EXTENSIONS An extension designates a continuation beyond the normal bearing of the joist. The extension can be the top chord only or the full of the joist, in which case, it is referred to as a cantilever joist. The extended top chord section varies according to the following conditions: the design loads, the extension length, the deflection criterion, and the conditions of bearing and anchorage. The section can be reinforced if required. In a section without reinforcement, the extension material is the same as the top chord of the joist. A reinforced section has 2 or 4 angles as extension material, or 1 or 2 channels having a higher capacity than that of the top chord between the bearings. Also, a reinforced section projects into one or several interior panels such that the joist can resist bending and shearing forces brought on by the extension of the top chord. Variable A B C A B C Bearing Bearing Section A Section B Section C Top chord extension Section reinforced with 2 angles Variable A B C A B C Bearing Section reinforced with 4 angles Section A Section B Section C Bearing Cantilever joist A B C A B C Bearing Section A Section B Section C Section reinforced with 1 channel A B C A B C A B C A B C Bearing Section A Section B Section C Bearing Section reinforced with 2 channels Section A Section B Section C Section without reinforcement 21

22 Standard details The tables below serve as a guide to determine a suitable shoe based on uniform loading and a maximum extension length. The extensions are based on the maximum capacity of a 2-channel section without any slope. This is an economical section for this kind of condition. The maximum top chord extension is determined by the bending and shear resistance of the section, or by the deflection of the extension, which is limited to L/120 with a fixed end. In fact, the joist and its extension are analyzed simultaneously in a matrix calculation. METRIC MAXIMUM TOP CHORD EXTENSION (mm) Factored load (kn/m) Effective shoe Service load (kn/m) (mm) ,920 1,750 1,620 1,520 1,450 1,380 1,330 1,290 1,240 1,200 1,150 1,130 1, ,390 2,170 2,010 1,900 1,800 1,700 1,650 1,550 1,500 1,450 1,400 1,350 1, ,750 2,500 2,350 2,200 2,050 1,950 1,900 1,800 1,750 1,650 1,600 1,550 1, ,050 2,800 2,600 2,450 2,300 2,200 2,150 2,050 2,000 1,900 1,850 1,800 1, ,300 3,000 2,800 2,650 2,550 2,450 2,350 2,250 2,200 2,100 2,050 2,000 1,950 IMPERIAL MAXIMUM TOP CHORD EXTENSION (ft.) Factored load (lb./ft.) Effective shoe Service load (lb./ft.) (in.) The building designer must make allowance for sufficient shoe when the top flange is not horizontal or in case of bolted assembly. In this case, the clear is less than the shoe. Shoe Clear 22

23 Standard details MAXIMUM DUCT OPENINGS ING of Canada I Saint-Hyacinthe, Quebec P 305 mm 12 in. D S H R S L Warren Geometry; H 350 mm (14 in.) 610 mm (TYP) 24 in. (TYP) H D S R L S Modified Warren Geometry; H 400 mm (16 in.) METRIC Warren Geometry Modified Warren Geometry DIMENSIONS OF FREE OPENINGS FOR VARIOUS JOISTS AND JOIST GIRDER CONFIGURATIONS Configuration (mm) Opening (mm) H P D S L R , , , , , girder , , , , Note: Final dimensions of free openings should be verified with Canam s joist design sheet. When duct-opening dimensions exceed the limits above, some web members must be removed. The shear forces are then transferred to the adjacent web members of the top and bottom chords. The chords will need to be reinforced; this will limit the maximum height of the free opening as well. The maximum opening height should be limited to the joist minus 200 mm (8 in.). If the opening height cannot be limited to this value, contact Canam. Because the shear forces carried by the web members increase along the joist toward the bearing, the location of the duct opening is more critical near the bearings; more shear forces must be transferred to the top and bottom chords. For this reason, the duct-opening center must be located away from a bearing by a distance of at least 2.5 times the joist. The best location (for economical reasons) is at the mid span of the joist. Location must be greater than: 2.5 x H 100 mm (4 in.) min. H 100 mm (4 in.) min. Pratt Geometry Location must be greater than: 2.5 x H 100 mm (4 in.) min. H 100 mm (4 in.) min. Modified Warren Geometry 23

24 Standard details MAXIMUM DUCT OPENINGS IMPERIAL DIMENSIONS OF FREE OPENINGS FOR VARIOUS JOISTS AND JOIST GIRDER CONFIGURATIONS Configuration (in.) Opening (in.) H P D S L R girder Warren Geometry Modified Warren Geometry H H P 305 mm 12 in. D S R S L Warren Geometry; H 350 mm (14 in.) 610 mm (TYP) 24 in. (TYP) D S R L S Modified Warren Geometry; H 400 mm (16 in.) Note: Final dimensions of free openings should be verified with Canam s joist design sheet. When duct-opening dimensions exceed the limits above, some web members must be removed. The shear forces are then transferred to the adjacent web members of the top and bottom chords. The chords will need to be reinforced; this will limit the maximum height of the free opening as well. The maximum opening height should be limited to the joist minus 200 mm (8 in.). If the opening height cannot be limited to this value, contact Canam. Because the shear forces carried by the web members increase along the joist toward the bearing, the location of the duct opening is more critical near the bearings; more shear forces must be transferred to the top and bottom chords. For this reason, the duct-opening center must be located away from a bearing by a distance of at least 2.5 times the joist. The best location (for economical reasons) is at the mid span of the joist. Location must be greater than: 2.5 x H 100 mm (4 in.) min. 100 mm (4 in.) min. Pratt Geometry Location must be greater than: 2.5 x H 100 mm (4 in.) min. 100 mm (4 in.) min. H H Modified Warren Geometry 24

25 Standard details TransAlta Rainforest I Calgary, Alberta Agora, Collège Saint-Sacrement I Terrebonne, Quebec Avon Canada I Pointe-Claire, Quebec 25

26 Standard details GEOMETRY AND SHAPES The geometry refers to the web profile system. The standard geometry types are presented below: Modified Warren Warren In some cases, a joist could have 2 geometrical types. For architectural considerations, the building designer can specify a fixed geometry applicable to a joist group. More than one geometrical type may be specified. However, panel alignment of joists having varying lengths and loading conditions may not be possible. s are usually evenly spaced along a joist girder which can combine two types of geometry as shown below where a Warren type is combined with a modified Warren geometry. Pratt Combined geometries The panel points of a joist girder are usually located where joists are bearing. Depending on the joist spacing, the design engineer can add intermediate panel points to design the optimum joist girder for the loading conditions and the span. The different panel point configurations presented below can be specified by the building designer for architectural purposes or large duct openings. Type G: The panel points where the joists are bearing correspond to the intersection of the two diagonals at the top chord. Type G configuration Type VG: The panel points where the joists are bearing correspond to the position of the secondary web members (verticals) on the top chord. Type VG configuration 26

27 Standard details Type BG: The panel points where the joists are bearing correspond to the position of the secondary web members (verticals) and the intersection of the two diagonals at the top chord. Type BG configuration The shape of a joist may depend on its use and the type of roofing system requested by the customer. It can take one or more of the following shapes: STANDARD SHAPE Parallel chords NON-STANDARD SHAPES ** Variable (typ.) 1 slope 1 slope 3 slopes Variable (typ.) 3 slopes Variable Variable (typ.) 2 slopes 2 slopes Variable 3 slopes Variable (typ.) Variable (typ.) 4 slopes 4 slopes R Bowstring SPECIAL SHAPES ** Depending on the radius of curvature, the angles composing the top and/or bottom chord could require a rolling operation. * The building designer must consider in the design that the shapes can produce significant horizontal forces and/or movement on the supporting structure due to the deflection of the joist. ** Non-standard shapes and special shapes are more expensive due to their complexity. R 1 Barrel * Scissor R 2 Scissor * 27

28 Standard details MINIMUM DEPTH AND SPAN For fabrication reasons, the building designer must consider that minimum joist is limited to 200 mm (8 in.) and minimum joist span is limited to mm (8 ft.). For shorter spans, joist substitutes, usually made of 1 or 2 channels, can be specified by the building designer or proposed by Canam. SHOES The standard shoe dimensions vary according to product and span: Product Depth Min. length 2,450 mm (8 ft.) 15,200 mm (50 ft.) 100 mm (4 in.) 100 mm (4 in.) 15,200 mm (50 ft.) 27,400 mm (90 ft.) 125 mm (5 in.) 100 mm (4 in.) 27,400 mm (90 ft.) and over 190 mm (7 1/2 in.) 150 mm (6 in.) girder All lengths 190 mm (7 1/2 in.) 150 mm (6 in.) However specific customer requests can be accommodated. The shoe must always be specified at the gridline. For joists on which the left and right bearings are not at the same level (sloped joist), the exterior and interior shoe s are determined in such a way as to respect the at the gridline. To ensure that the intersection point of the end diagonal and the top chord occurs above the bearing, the minimum shoe should be specified according to the slope of the joist and the clearance of the supporting member from the gridline. 12 (imperial) 250 (metric) Interior shoe Exterior shoe Shoe at gridline Interior shoe Shoe at gridline Exterior shoe x Depth at gridline Clearance 28

29 Standard details METRIC MINIMUM SHOE DEPTH (mm) Clearance of bearing (mm) Sloped joist (x/250) IMPERIAL MINIMUM SHOE DEPTH (in.) Clearance of bearing (in.) Sloped joist (x/12) / PARTICULARITIES BEARING ON CONCRETE OR MASONRY WALL The building designer shall allow for a bearing plate for the joist girder. The plate shall be in accordance with CAN/CSA S Standard if used for a masonry wall and CAN/CSA A Standard if used on concrete. The plate shall have minimum dimensions in length and width to ensure a minimum bearing for the joist girder of 150 mm (6 in.) and to allow the horizontal legs of the seat to be welded to the bearing plate. BEARING ON STEEL The joist girder shall be extended on the steel support to respect the minimum bearing of 100 mm (4 in.). The building designer must ensure that the type of connection and bearing support used respect this criteria. 29

30 Standard details DETAILS CEILING EXTENSION A A Section A FLUSH SHOE A flush shoe can be used when the joist reaction does not exceed 45 kn (10 kip). BOLTED SPLICE In certain cases, joists are delivered in two sections. This is usually done because of transportation considerations, difficult installation conditions in an existing building, or dipping tank dimension limitations when a joist receives hot galvanization treatment. A bolted splice is usually made at mid span. The number and position of plates and bolts can vary according to the loads to be transferred. We use high-strength bolts that meet ASTM A325 or ASTM A490 standards. A B B A Section A Bolted splice at top chord Section B Bolted splice at bottom chord 30

31 Standard details Depending on dimensions and quantities, joists can be fabricated as a single piece that is split into two sections for shipping, or fabricated as two separate pieces. In the plant, two additional metal tags are attached to the central part of the joist to ensure correspondence of male and female parts. s fabricated as a single piece will have two identical metal tags in the central part of the joist. On the other hand, joists fabricated as two separate pieces will have different metal tags. Example of identification for a joist fabricated as a single piece: Male and female section tags T1 T1-1 T1-1 Erection drawing mark tag If multiple joists with the same mark are fabricated, placement of the male section of the first joist must correspond with placement of the female section of the first joist, and so forth in the same manner. Examples: T1-1 with T1-1, T1-2 with T1-2, etc. Example of identification for a joist fabricated as two separate pieces: Male and female section tags T1 T1-L T1-R Erection drawing mark tag If multiple joists with the same mark are fabricated, the male sections can be arranged with any female section of the joist. They will be identified in the following manner: T1-L with T1-R. BOTTOM CHORD BEARING When the joist bearing is on the bottom chord, the top chord must be laterally supported with bridging. CANTILEVER JOIST A cantilever joist can have bearing on the top or bottom chord. The bottom chord must be adequately braced to resist compression loads caused by the cantilever. It is good practice to install a bridging row next to the joist support as well as at the end of its cantilevers. Bottom chord bearing Top chord bearing Top chord bearing requires bolted splices on the bottom chord. 31

32 Standard details JOIST AND JOIST GIRDER IDENTIFICATION s and joist girders are identified on erection drawings by piece marks, examples: T1, T1A, J1, M2, etc. s and joist girders from the same family (T1, T1A) usually have the same chords but differ in terms of connections. Identical joists and joist girders have the same piece mark. Piece marks are indicated on the drawing near one of the ends of the line representing the joist or joist girder. At the plant, a metal identification tag is attached to the left end of the joist or joist girder. It is essential that the joist or joist girder be erected so that the metal tag is positioned at the same end of the building as indicated on the erection drawing. STANDARD CONNECTIONS Use of Canam standard connection details is strongly recommended for the following reasons: Standardization of fabrication information; Faster drawing checking; Minimized risk of error. However specific customer requests can be accommodated. The standard connection details can be downloaded from the Canam web site at: Below is the list of available connection details: s bearing on steel structures; s bearing on concrete structures; girders bearing on steel structures; girders bearing on concrete structures. Nemaska First Nation Sports Complex I Nemiscau, Quebec Hillcrest Curling Facility I Vancouver, British Columbia 32

33 Surface preparation and paint Surface preparation plays a significant role in paint performance. Adequate surface preparation allows the paint to adhere to structural steel, providing improved protection against corrosion. The level of preparation and the paint application method both depend on the type of environment to which the steel will be exposed. Thanks to ultramodern equipment selected to meet the most demanding requirements, Canam Group is poised to offer surface preparation, metallizing and painting services for all types and scales of structural steel and metal components. Treatment processes are based on the latest technologies in order to achieve optimum results. PAINT STANDARDS In 1975, The Canadian Institute of Steel Construction (CISC) in cooperation with the Canadian Paint Manufacturers Association (CPMA) published reference documents related to the paint specifications for structural steel. The CISC/CPMA 1-73a paint standard applies to a quickdrying one-coat paint for use on structural steel that provides adequate protection against exposure to a non-corrosive environment as found in rural, urban, or semi-industrial settings, for a period not exceeding six months. Painted structural steel building components using this standard should not be used on permanent exterior exposed applications. Exposure of this product in coastal or high industrial areas may cause advanced deterioration of paint applied to this specification. Surface preparation may be limited to Solvent Cleaning (SSPC SP1) or Hand Tool Cleaning (SSPC SP2). Because of possible noncompatibility of this paint with finish coats, this shop applied paint is not recommended for use as a primer for the application of a multi-layer paint system. The CISC/CPMA 2-75 paint standard applies to a quick-drying primer for use on structural steel. This one-coat primer provides acceptable protection when exposed to a mainly non-corrosive environment as found in a rural, urban, or semi-industrial settings, for a period not exceeding twelve months. Painted structural steel building components using this standard should not be used on permanent exterior exposed applications. Exposure of this product in coastal or high industrial areas may cause advanced deterioration of paint applied to this specification. Final surface preparation must be done by Brush-Off Blast Cleaning (SSPC SP7). This layer of primer is usually covered with a finish coat according to the paint supplier s recommendations. Dip coating is commonly used to apply paint for one or more of the above standards. When compared with spraying, experts in the field recommend application by dipping because it provides improved coverage of exposed surfaces. Although a coat of paint applied by dipping does not create an even dry film layer, it does not reduce its protection against corrosion. PAINT COSTS Canam uses a single type of paint that meets both the CISC/CPMA 1-73a and CISC/ CPMA 2-75 specifications. The cost difference is mainly the result of two factors: surface preparation (SSPC SP2 or SSPC SP7) and the method of primer application (dipping or spraying). The following table compares paint costs according to final surface preparation and paint application methods for both paint standards. For example, for CISC/CPMA 1-73a type paint using SSPC SP2 final surface preparation, it is noted that spray painting is twelve times more expensive than dipping. 33

34 Surface preparation and paint Paint type SELECTION TABLE FOR PAINT COSTS Surface preparation Paint application cost factor Dipping Spraying CISC/CPMA 1-73a SSPC SP CISC/CPMA 2-75 SSPC SP Canam may apply paint that meets standards other than those specified in this document. Prices and delivery schedules are adjusted accordingly. For example, certain types of paint require nearly 24 hours before handling the joists. COLOURS Standard paint colour is gray. Red paint is optional. JOISTS EXPOSED TO THE ELEMENTS OR CORROSIVE CONDITIONS A high performance anti-corrosive paint is recommended for specification on joists permanently exposed to the elements or corrosive conditions during their service life. The building designer must pay special attention to item of the CAN/CSA standard. If a minimum thickness of material is required, it must be indicated on the drawings and specifications. When specified, joists may be hot dipped galvanized. Brush off blast cleaning surface preparation (SSPC SP7) is recommended to prevent scaling problems. In the galvanization process, the joists are acid washed, rinsed, and then dipped in a zinc bath at a temperature of 450 C (840 F). The and span of joists are limited by the size of the subcontractor s galvanizing tanks. (Reference: For strict conditions of hygiene, such as for meat products or food processing, it is recommended that the building designer specifies sealed welds. If the welds are not sealed, there is a risk that the acid used in the cleaning process remains trapped between the surface of the steel and causes acid bleeding through ruptures in the zinc film caused by pressure. The building designer must limit specification of sealed joints unless absolutely necessary because sealed joints require additional shop time. For galvanization, the thickness of the top and bottom chords shall be at least 4 mm (0.157 in.), and 3 mm (0.118 in.) for the web members, to avoid permanent deformation of the chords from overheating. Galvanized joists may also be painted. The building designer must ensure compatibility between the paint type and the galvanization product. 34

35 Vibration STEEL JOIST FLOOR VIBRATION COMPARISON The increased use of longer spans and lighter floor systems has resulted in the need to address the problem of floor vibration. The building structural designer must analyze floor vibration and its effect on the building end users and specify the proper characteristics to reduce vibration. The behavior of two-way flooring systems has been studied using models and in-situ testing. Several simplified equations have been developed to predict floor behavior and damping values for walking induced vibration and have been established according to the type of wall partitions and floor finishes. These equations are now part of Appendix E, a non-mandatory part of CSA standard S16 since In 2005, the National Building Code also addressed this issue at the Appendix D of the user guide. Steel Design Guide no. 11 Floor vibrations due to human activity, jointly published by the American and Canadian institutes of steel construction in 1997, contains more recent information on the subject. This guide covers different types of floor vibrations and is one of the main references of Appendix E of standard CAN/CSA S The formulas shown in these publications allow the user to define the vibration characteristics of a floor system: the initial acceleration produced by a heel drop and the natural frequency of the system. These two parameters allow the designer to verify if the floor system will produce vertical oscillations in resonance with rhythmic human activities or with enough amplitude to disturb other occupants. The amplitude of the vibrations will decay according to the type of partitions, ceiling suspensions, and floor finish. The decay rate will also influence the sensitivity of the occupants. This information is not readily available to the joist supplier. The joist supplier usually receives only the floor drawings and general joist specifications and this information is used for joist design. Furthermore, the following examples show that the design of a joist, for which spacing,, span, bearing support, and dead loads have all been predetermined by the project structural engineer, cannot be easily modified to reduce floor vibration induced by walking below the annoyance threshold for the other occupants. The example is given for office floors where the annoyance threshold is defined as a floor acceleration of 0.5% of the gravity acceleration. For floors in a shopping centre, the threshold would be an acceleration of 1.5% of the gravity acceleration. This higher threshold means that the occupants are less disturbed by vibrations produced by walking loads. 35

36 Vibration TYPICAL OFFICE FLOOR USED AS BASE In the example, the joists have a 9,000 mm (29 ft.-6 ¼ in.) span, a 500 mm (approx. 20 in.), and are spaced at 1,200 mm (3 ft.-11 ¼ in.) on center. The joists are bearing on beams at both ends on 100 mm deep seats. We consider that the beams will only be partially composite for vibration calculations because of the relative lack of lateral stiffness of such a bearing seat. The beam span is 7,500 mm (24 ft.-7 ¼ in.) with joists on one side only. The floor is composed of a 100 mm (4 in.) concrete slab, including the 38 mm (1 ½ in.) steel deck profile. The loads are as follows: Structural steel 0.25 kpa ( 5 psf) Steel joists 0.20 kpa ( 4 psf) Deck-slab of 100 mm 1.87 kpa (39 psf) Ceiling, mechanical & floor finish 0.50 kpa (10 psf) Partitions 1.00 kpa (21 psf) DEAD LOAD TOTAL 3.82 kpa (79 psf) LIVE LOAD 2.40 kpa (50 psf) From the Canam catalog, select a joist with a 9-meter (29 ft in.)span to support the following load: w f = 1.2 m x (3.82 x x 1.5) = kn/m The 9-meter (29 ft.-½ in.) selection table indicates that joists with a 10.5 kn/m factored capacity will weigh 16.7 kg/m and that 66% of the service load will produce a deflection value of span/360. By reducing the simple span deflection formula under uniform load for span/360, we obtain the following approximation of the moment of inertia: I joist = 23,436 x percentage x w s x (span) 3 where I joist = moment of inertia in mm 4 percentage = value shown in table for deflection / 100 w s = total service load (total factored load / 1.5) span = span of joist in meters I joist = 23,436 x (66 / 100) x (10.5 / 1.5) x (9) 3 = 79 x 10 6 mm 4 The center of gravity of the joist can be assumed to be at mid : A joist chords = I joist / ( / 2) 2 = 1,263 mm 2 A beam can be chosen from the selection tables published by the CISC (assuming that the beam supports joists on both sides): W530 x 74 (W21 x 50) with F y = 350 MPa (50 ksi) and a moment of inertia of 156 x 10 6 mm 4 Notes: This example is based on International System of Units (SI) measurements. An approximate conversion of certain values is provided in parentheses for reference purposes. Take care not to confuse composite moment of inertia and modified moment of inertia (equation 3.15) with effective moment of inertia (equation 3.18) in Guide No. 11. The moment of inertia specified on the drawings must be the joist moment of inertia based on the top and bottom chords. Always specify the type of moment of inertia that is indicated on the drawings. 36

37 Vibration ALTERNATIVE 1 If a slab of 140 mm (5 in.) instead of 100 mm (4 in.) is used, the dead load increases and the size of the joists and beams will also increase. Structural steel 0.25 kpa ( 5 psf) Steel joists 0.20 kpa ( 4 psf) Deck-slab of 140 mm 2.79 kpa (58 psf) Ceiling, mechanical & floor finish 0.50 kpa (10 psf) Partitions 1.00 kpa (21 psf) DEAD LOAD TOTAL 4.74 kpa (98 psf) LIVE LOAD 2.40 kpa (50 psf) From the Canam catalog, select a joist with a 9-meter (29 ft in.) span to support the following load: w f = 1.2 m x (4.74 x x 1.5) = kn/m The table indicates that the joists will weigh 18.2 kg/m and that 64% of the service load will produce a deflection value of span/360. I joist = 23,436 x (64 / 100) x (12 / 1.5) x (9) 3 = 88 x 106 mm 4 The center of gravity of the joist can be assumed to be at mid : A joist chords = I joist / ( / 2) 2 = 1,400 mm 2 This time, the beam chosen from the CISC selection tables (considering that the beam support each side of the joists): W530 x 82 (W21 x 55) with Fy = 350 MPa (50 ksi) and Ix = 478 x 10 6 mm 4 Note: This example is based on International System of Units (SI) measurements. An approximate conversion of certain values is provided in parentheses for reference purposes. ALTERNATIVE 2 Starting from the base example, we consider that the structural engineer of the building clearly indicates that the size of the joists should be doubled to reduce floor vibration. Using the data of those 3 conditions, with the proposed equations of Steel Design Guide no. 11 published jointly by the American and Canadian institutes for steel construction, we obtain the vibration properties shown in the following comparison table: 37

38 Vibration Parameter COMPARISON OF VARIOUS ARRANGEMENTS Base Alternative 1 (increased thickness of slab by 30 mm) Alternative 2 (increased joist moment of inertia) Peak acceleration a o (% g) 0.80 % 0.50 % 0.57 % System frequency f (Hz) length (mm) 9,000 9,000 9,000 (mm) spacing (mm) 1,200 1,200 1,200 Composite joist moment of inertia (10 6 mm 4 ) Deck (mm) Slab-deck thickness (mm) Slab-deck-joist dead weight (kpa) Additional participating load (kpa) Beam size W530 x 74 W530 x 82 W530 x 74 Beam span (mm) 7,500 7,500 7,500 This comparison shows that the vibration characteristics improve by adding dead weight rather than by doubling the joist non-composite moment of inertia. One must note that the alternative 2 used did not sufficiently improve the vibration properties of the floor to lower their amplitude to below the annoyance threshold for offices. Additional calculations indicate that using a 125 mm (5 in.) deck-slab with a 100% increase in the joist and beam sections would lower the vibration amplitude to below the annoyance threshold of 0.5% of g. The building designer controls the main parameters affecting floor vibration characteristics and he or she should make the vibration calculations to find an economical solution. The information supplied in this catalog will allow the structural engineer to evaluate the vibration properties of the floor during the initial design. The structural engineer of the project should always specify the proper slab thickness and the minimum moment of inertia of the steel joists to have a floor with vibration characteristics below the annoyance threshold based on the type of occupancy. The joist designer will ensure conformity to the minimum moment of inertia required by the building designer for the joists (see clause vibration). Please note that the analysis of floors subject to rhythmic vibrations (dance floor) is different from that performed for vibrations caused by walking (Steel Design Guide, no. 11 Floor vibrations due to human activity, chapter 5). Finally, here are a few tips to obtain satisfactory vibration behavior: increase the thickness of the concrete slab; increase beam moment of inertia; give special consideration to perimeter beams and joists; add shear transfer elements or shear studs between the beam and the concrete slab to obtain a composite action; reduce the span of joists and beams; increase joist moment of inertia. 38

39 Special conditions SPECIAL JOIST DEFLECTION Appendix D of the CAN/CSA S16-01 standard provides recommended maximum values for deflections for specified design live and wind loads. The following are the maximum values of appendix D recommended for the vertical deflection: Building type Specified loading Application Maximum Industrial Live Members supporting inelastic roof coverings. L/240 Live Members supporting inelastic roof coverings. L/180 Live Members supporting floors. L/300 Maximum wheel loads (no impact) Maximum wheel loads (no impact) Crane runway girders for crane capacity of 225 kn and over. L/800 Crane runway girders for crane capacity of 225 kn. L/600 All others Live Members of floors and roofs supporting construction and finishes susceptible to cracking. L/360 Live Members of floors and roofs supporting construction and finishes not susceptible to cracking. L/300 Notes: As mentioned in Appendix D, the designer should consider the inclusion of specified dead loads in some instances. For example, nonpermanent partitions, which are classified by the National Building Code as dead load, should be part of the loading considered under Appendix D if they are likely to be applied to the structure after the completion of finishes susceptible to cracking. Please note that the concrete cover at the centre line of the joist will be reduced by the amount of camber provided minus the deflection realized under self weight of the concrete alone. This must be accounted by the designer of the building with respect to the serviceability and fire resistance, etc. 1,000 mm (3 ft.-3 in.) DEFLECTION OF CANTILEVERED JOISTS It is important to note that in the calculation of the allowable deflection of cantilevered joists, we consider that the cantilever end length "L" is equivalent to twice its length, as mentioned in Commentary D of the National Building Code of Canada (NBC) 2005 User's Guide. Therefore, for a 1,000 mm (3 ft.-3 in.) cantilever end length with a deflection criteria of L/240, the maximum allowable deflection is 2 x 1,000/240 = 8 mm ( 5 16 in.). CAMBER Camber is specified by the building designer on the plans and specifications. Unless otherwise indicated by the designer, the standards are applied as stated in Clause of the CAN/CSA S16-01 Standard and the joist girders are cambered to compensate for the deflection due to the dead load. girders with a span of 25 m (82 ft.) or more are cambered for the dead load plus one half of the service load. In some cases, camber must be restricted for joists and joist girders adjacent to non-flexible walls. 39

40 Special conditions SPECIAL LOADS AND MOMENTS Canadian standards classify loads in the following manner: permanent, service, seismic, and wind loads. For limit states design, loads are factored and combined to obtain the worst possible effect. Loads applied to joists and joist girders can be uniform, partial, concentrated, axial, or moment. Snow pile up loads represent a special partial load case. Uplift loads are applied in an upward direction and should always be specified as a gross uplift load. Loads can be applied to the top chord, the bottom chord, or to both chords. When specifying the dead load, the building designer should always include the self-weight of the joists and bridging. Unless clearly specified, Canam will assume that the self-weight of joists is included in the total dead load. TRANSFER OF AXIAL LOADS Wind and seismic loads are usually transferred by the roof diaphragm to the axes of the vertical bracing system. The seismic loads transferred have a cumulative effect along these axes. The building design engineer specifies these loads on the plans and specifications. The transfer of an axial load between joists along the axes of the vertical bracing system, may require the reinforcement of the first panel at top. VARIOUS TYPES OF LOADS Uniform load Partial load Triangular Uniform Snow pile up load A (axial) (axial) Concentrated load (axial) (axial) Axial: an additional load specified by the building designer must be considered. At a specific location At any panel point Anywhere A Lateral load Axial load Moment load Section A-A Transfer of axial loads 40

41 Special conditions A A Section A-A Supplied by the steel contractor unless otherwise noted. The building designer may consider a lateral factored capacity of 4.5 kn (1,000 lb) for the joist seats for the transfer of the deck shear forces to the girder top chord. Adding shear connectors between the joists on the girder increases the capacity to transfer diaphragm shear forces. The building designer should specify the effort to ensure that the detail of the connexion (round holes) is considered. Depending on the specifications of the building designer, axial loads between two joist girders may be transferred to the top chord as follows: By angles placed under the top chord of the joist girders (suggestion 1); By a transfer plate placed on the top of the top chord (suggestion 2); By a transfer plate placed between the two angles of the top chord of the joist girders (suggestion 3); A Transfer on an axial load by two angles placed under the top chord Suggestion 1 Supplied by the steel contractor unless otherwise noted. Supplied by the steel contractor unless otherwise noted. A Section A-A Transfer of an axial load by a plate placed between the angles of the top chord Suggestion 3 Without a transfer piece using the capacity of the joist girder shoes (suggestion 4). Transfer of an axial load by a plate placed on the top of the top chord Suggestion 2 Transfer of an axial load using the shoes Suggestion 4 Although not illustrated, the transfer of an axial load by the base of the shoe, usually requires bracing of the first panel of the top chord. In the case where a joist girder has adjacent bracing, the effect is represented by an axial load applied to the bottom chord. and Transfer of an axial load at the bottom chord 41

42 Special conditions UNBALANCED LOADS As with a steel supporting beam, the joist girder can have an unbalanced load on its longitudinal axis. s distributed on either side of the joist girder may be at different lengths or the loads they support may vary. This situation causes torsional stress in the joist girder, which will be considered by the joist girder designer. Therefore the designer could specify larger chords and web members for the joist girder and add additional knee braces between the bottom chord of the joist girders and the joists bearing on them. However, to avoid unbalanced loads, the joists must be staggered on each side of the joist girder: girder girder girder girder R1 R2 2 m m m m m m m m 6-8 girder 2 m m 6-8 girder 2 m 6-8 New spacings for staggered joists 1.9 m 6-2 R1 R2 Unbalanced loading girder top chord Centre of reaction C L s are staggered as required Staggered joists The offsetting of joists bearing on the joist girder will be considered by Canam during the design stage. LOAD REDUCTION ACCORDING TO TRIBUTARY AREA Although a joist girder may have a tributary area that is much larger than that of a joist, a reduction of the live load allowed by the National Building Code of Canada in Clause is very limited. In fact, no reduction is permitted for a live load due to snow or an assembly area designed for a live load less than 4.8 kpa (100 psf). The reduction is applicable for a specific use and a minimal surface area (reference: NBC 2005, Clauses and ). 42

43 Special conditions END MOMENTS GRAVITATIONAL MOMENTS The use of a joist or joist girder in a rigid frame relieves the top chord and carries the compression loads to the bottom chord. End moments, as specified by the building designer on the plans and specifications, result in the analysis of a frame with defined moments of inertia. It is recommended that the building designer specifies minimum and maximum limits of inertia to ensure that the frame is designed according to the analysis model. Gravitational moments The moment of inertia of the joist girder may be estimated using the equation below in either metric or imperial. METRIC I = 1,596 M f D where I = Moment of inertia of the joist girder (mm 4 ) M f = Factored bending moment (kn m) D = Depth of joist girder (mm) Note : M f may be calculated by considering a uniform load applied to the joist girder. M f = (1.25DL + 1.5LL) x l x L 2 8 where DL = Dead load (kpa) LL = Live load (kpa) l = Tributary width of joist girder (m) L = girder span (m) IMPERIAL I = M f D where I = Moment of inertia of the joist girder (in. 4 ) M f = Factored bending moment (kip ft.) D = Depth of joist girder (in.) Note : M f may be calculated using a uniform loading applied to the joist girder. M f = (1.25DL + 1.5LL) x l x L 2 8,000 where DL = Dead load (psf) LL = Live load (psf) l = Tributary width of joist girder (ft.) L = girder span (ft.) 43

44 Special conditions WIND MOMENTS Horizontal wind loads on a joist or joist girder in a rigid frame may cause alternating moments as shown beside. Consequently, the joist will be analyzed with opposite moments. Examples: Case No kn m and + 10 kn m Case No kn m and - 10 kn m JOIST OR JOIST GIRDER ANALYSIS AND DESIGN The erection plans, supplied by Canam, usually instruct the erector to fasten the bottom chord after all of the dead loads have been applied. In this way, the joist or joist girder follows the condition for simple span condition under dead loads. In the case of end gravity moments, Canam will assume that they are caused only by the live load, unless otherwise specified by the building designer. When end moments are specified, the joist or joist girder shall first be designed to support loads on simple span condition. Then according to the combination of defined loads in the codes, different loading scenarios can be generated during analysis of the joist or joist girder. Each element shall be designed for worst-case conditions, whether simple span or with end moments. In addition to providing the end moment values applicable to the joist or joist girder, the building designer must pay special attention to ensure that the end connections develop the moments for which the building was designed. As in the case of the transfer of axial loads, the transfer of loads generated by an end moment may require the reinforcement of the first panel at top chord or by another type of reinforcement calculated according to the load. The end moment transferred to the joist girder can divide into forces in opposite directions (couple) applied to the top and bottom chords. For a connection with a transfer plate, the couple is calculated as follows: Wind moments Connection at bottom chord with a tie joist plate T f = C f = M f d e where T f = C f = Axial force (kn or kip) M f = Factored moment connection ((kn m or kip pi) d e = Effective joist girder (m or ft.) Transfer plate supplied by the steel contractor unless otherwise noted. T f or C f M f d e T f or C f Stabilizer plate supplied by the steel contractor unless otherwise noted. Transfer of the loads via a transfer plate 44

45 Special conditions For a connection where the loads are carried by the shoe base, the axial force increases due to a shorter moment arm. T f = C f = M f d e where T f = C f = Axial force (kn or kip) M f = Factored moment connection ((kn m or kip pi) d e = Effective joist girder (m or ft.) girder shoe T f or C f M f d e T f or C f Stabilizer plate supplied by the steel contractor unless otherwise noted. Transfer of the loads by the shoe base e Since the loads transferred by the base of the shoe create significant eccentricity, normally the first panel must be reinforced by the joist girder engineer. Vertical eccentricity at bearing due to the axial load Different types of reinforcement of the first panel are presented below. e e e A- Addition of a strut B- Addition of stiffener plate Different types of reinforcement of the first panel C- Shoe extension A A Only in the case or we must transfer from the efforts. Section A-A Standard connection at bottom chord with a stabilizer plate Some connections to the bottom chord of joist or joist girder use an angle welded to the column and a tie joist plate shop welded to the joist girder. However, this type of connection, as shown beside, is no longer recommended. A standard connection with a stabilizer plate is more simple and gives the same lateral stability. The steel contractor usually supplies the steel plate on the column at the location of the bottom chord of the joist girder. The plate is inserted between the vertical flanges of the bottom chord angles. A plate should have a thickness of 13 mm (½ in.) or 19 mm (¾ in.). A hole in the stabilizer plate allows the column to be plumbed with guy wires. The transfer of forces from the column to the bottom chord is achieved by welding the angles of the bottom chord to the plate, as indicated beside. 45

46 Special conditions JOISTS ADJACENT TO MORE RIGID SURFACES s adjacent to non-flexible walls or to beams and joists having a much shorter span, must have less deflection. The deflection limitation is necessary to avoid potential problems resulting from too large a movement differential.these problems tend to occur in the central part of the joist. To avoid an abrupt transition from the permitted deflection, it is recommended to change the deflection limit gradually, for adjacent joists having spans in excess of 12 m (40 ft.): 25,000 Line with increased stiffness 1 st joist Criterion = 25,000 / 50 = nd joist Criterion = 25,000 / 70 = rd joist Criterion = 25,000 / 90 = 278 L/500 L/360 L/280 Adjacent joist Deflection criterion Metric (mm) Imperial (ft.) 1st joist / 50 / nd joist / 70 / rd joist / 90 / th joist / 110 / th joist / 130 / th joist Criterion = 25,000 / 110 = 227 L/240 min. Note: In all cases, the deflection criterion (usually under the service load) must be greater than or equal to that specified on the customer drawings or mentioned in the specifications. Example: = 25 m; deflection criterion under service load = L / 240 Another solution consists of placing a perimeter joist with a sliding assembly on the supporting wind column. This also allows for easier building expansion in the future. Given the weak lateral rigidity of a joist, when it is acted upon laterally by the top of the wind column, the structural engineer must assure transfer of the load into the roof diaphragm or another horizontal bracing system. JOISTS WITH LATERAL SLOPE Building designers should request joists with a lateral slope only when absolutely necessary as this is not an economical approach. When using standing seam metal roofs, the joist top chord must be checked for in plane and out of plane (lateral) loads when the lateral slope exceeds what is required for normal roof drainage (2%). With steel deck attached to the top chord of the joists, the diaphragm action of the deck should be sufficient to brace the joist top chord as long as the lateral slope does not exceed 6%. Special consideration is also required for long-span joists. Since these components are subject to lateral deformation during installation, special dispositions may be required during the erection process. It could be advantageous to consider using steel deck with a higher gage in order to ensure the lateral support of joists. The following paragraphs explain what is required to provide resistance to the out of plane load component for the other cases. When a joist is installed with a lateral slope, a portion of the vertical load applied to the roof acts upon the joist laterally. Therefore, the lateral load must be considered when calculating the size of the top chord and the bridging. In this case, the bridging system plays a more important role. Wind column 2 1 A Bridging lines B Horizontal bracings Slope Slope s Typ. Wind thrust given by the designer. C 46

47 Special conditions For slopes 15 that are symmetrical between both sides of the summit, horizontal bracing is not required if the structural bridging rows are attached to the ridge because the horizontal forces from each slope cancel each other. For slopes 16, the difference between the forces generated by unbalanced loads must be taken into consideration. The use of horizontal bracing or steel deck with a higher gage therefore becomes necessary. s ANCHORS ON JOISTS It is not recommended to subject joists to torsion loads. Anchors that are attached to joists will cause significant torsion. The installation of a frame between two joists will prevent deformation and obtain an economical design. Anchorage Not recommended Recommended First Alliance Church I Calgary, Alberta 47

48 Special conditions SPECIAL JOISTS Canam can design and manufacture special joists to suit the conditions required by the building designer. A non standard joist can have particular assembly conditions and/or a special shape as described on page 27. Connecting a joist to a primary support like a truss, a beam or a column by others means than a standard shoe, or replacing some joist components to accommodate the connection of beams or other pieces, will make a special joist. Depending of the shape, special loading conditions may apply as per the Canadian standards in force. The building designer must clearly provide the special loading conditions on the specification documents and on the drawings. A special joist, very deep for example, may also require special shipping arrangements. The expertise of Canam in design and fabrication goes much higher than manufacturing only standard products. Haverstraw Marina I West Haverstraw, New York 48

49 Special conditions R C R girder reaction JOIST GIRDER TO COLUMN CONNECTIONS BEARING REACTION This section is intended to present to the building designer possible positions of the joist girder on the column. Consider the following three types of connections: bearing on top of the column, bearing on a bracket facing the column, and bearing facing the column but with a reaction at the center. For the first two types, the impact of connecting one or two joist girders to the column is also presented. BEARING ON TOP OF THE COLUMN A bearing on top of the column is the most economical solution. Sufficient shoe, usually 190 mm (7.5 in.), allows a reaction close to the center of the column. However, the slope of the end diagonal of the joist girder along with the width of the column may move the position of the reaction away from the center of the column. In general, the reaction of the joist girder occurs at the center or to the outside of the centerline of the shoe. Even if there is only one joist girder bearing on top of the column, an extension of the shoe to completely cover the column does not guarantee that the reaction will be located at the center of the column. As previously mentioned, the physical limitations may approach or move away from the reaction. When two joist girders are bearing on top of a column, their reactions are produced closer to the exterior faces of the column. Unbalanced reactions caused by varying bay dimensions, different bay loads, or by unbalanced loading conditions, as prescribed in the National Building Code of Canada, may cause bending stress in the column. girder reaction on top of the column R1 C R2 Reactions of two joist girders on top of the column The building designer must consider these special conditions when designing the column. ING of Canada I Saint-Hyacinthe, Quebec girder sitting on a bracket connected to the web of a column 49