Bridging Of Open Web Steel Joists And Joist Girders-Books Pdf

Bridging of Open Web Steel Joists and Joist Girders
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frequently subject to a net uplift force creating compression in the bottom chord where the. bottom chord PERMANENT BRIDGING will provide the necessary buckling resistance. FIGURE 1 CONSTRUCTION LOADS SET ON UNBRIDGED FIGURE 2 POTENTIAL CONSEQUENCE OF SETTING A. UNANCHORED JOISTS BUNDLE OF DECK ON UNBRIDGED UNANCHORED. Since 1984 representatives of the steel community have worked with the Department of Labor. and the Occupational Safety and Health Administration OSHA to establish new rules for the. safe erection of structural steel and as part of that rule safe erection standards for Open Web. Steel Joists As stated in the Federal Register OSHA 2001. By this notice the Occupational Safety and Health Administration OSHA revises the. construction industry safety standards which regulate steel erection The final rule enhances. protections provided to workers engaged in steel erection and updates the general provisions that. address steel erection The final rule sets performance oriented criteria where possible to. protect employees from steel erection related hazards such as working under loads hoisting. landing and placing decking column stability double connections hoisting landing and placing. steel joists and falls to lower levels, The OSHA Safety Standards supplement the SJI Specifications and Table 1 summarizes the. Federal Regulations that are included in 29 CFR 1926 757 Open web steel joists related to the. erection of joist products,ERECTION BRIDGING, The SJI K Series and LH and DLH Series Load Tables SJI 2005 show the total safe. uniformly distributed loads for standard products at various spans As the span increases for a. particular joist designation the uniformly distributed load carrying capacity decreases The. Load Tables also indicate when the span becomes too great for a particular joist designation to. be erected without ERECTION BRIDGING, Standard K Series joists that require ERECTION BRIDGING are indicated by the RED. SHADED area in the Load Tables SJI 2005 and are found in the OSHA Safety Standards. 1926 757 Table A Erection Bridging for Short Span Joists OSHA 2001 This table gives. the minimum span for each shortspan joist designation e g 26K8 and indicates when. ERECTION BRIDGING must be installed ERECTION BRIDGING is the bolted diagonal bridging that. is required to be installed prior to releasing the hoisting cables If Table A indicates that. ERECTION BRIDGING is Not Mandatory NM the joists can be spaced out attached and then. bridged in accordance with the SJI Standard Specifications for Open Web Steel Joists K Series. Section 6 SJI 2005, TABLE 1 SUMMARY OF FEDERAL REGULATIONS 29 CFR 1926 757 OPEN WEB STEEL JOISTS. Description Applicable Section s, Column or tie joists at or near columns must be bolted 757 a 1 and 2.
Increased strength of column or tie joists up to 60 foot span 757 a 3. Column or tie joists over 60 foot span to be set in tandem and fully bridged 757 a 4. Any supporting structure must be stabilized prior to setting joists or Joist Girders 757 a 5. Joists must be prevented from unintentional displacement prior to installation 757 a 6. Joists shall not be modified without the approval of the project structural engineer of 757 a 7. record SEOR, Unless panelized joists in bays of 40 foot or greater span must be bolted to their 757 a 8. supports unless constructability does not allow, Joists and Joist Girders shall not be used as anchorage for fall arrest systems 757 a 9. A bridging terminus point must be established before any erection bridging is installed 757 a 10. Joists and Joist Girders need to be attached to the support structure 757 b 1 2 and 3. and c 1 and 2, Only a certain number of employees are allowed on joists until bridging is installed and 757 c 3 and 4. Joists that require erection bridging are specified in Tables A and B 757 d 1. Erection bridging requirements are defined for joist spans over 60 feet through 100 feet 757 d 3 and over. 757 d 2 over 100 feet through 144 feet 144 feet 757 d 4. There are additional bridging requirements for bottom chord bearing joists 757 d 5. Bolted diagonal erection bridging must be shown on the joist placement plans 757 d 6. Loads placed on joists shall not exceed their capacity 757 e 1. No construction loads shall be placed on unbridged unanchored and unattached joists 757 e 2. Joist bridging bundles may not exceed 1000 lbs 757 e 3. Metal decking or deck accessory bundles may not exceed 4000 lbs and may only be set 757 e 4. on partially bridged joists under certain conditions. Construction loads shall be placed within 1 foot of the bearing surface of the joist end 757 e 5. The required bolted diagonal ERECTION BRIDGING for K Series joists must be installed as. the row of bridging nearest the mid span of the joist The ERECTION BRIDGING must also be. anchored to prevent lateral movement of the joist prior to the hoisting cables being released see. Section 6 This can be accomplished by securing the bridging to a fixed object such as a wall. steel beam or other stable portion of the structure OSHA refers to this anchorage point as a. bridging terminus point, Standard LH Series joists that require ERECTION BRIDGING are indicated by the RED or. BLUE SHADED areas in the Load Tables SJI 2005 and are also found in the OSHA Safety. Standards 1926 757 Table B Erection Bridging for Long Span Joists OSHA 2001 This. table gives the minimum span for each longspan joist designation e g 32LH06 and indicates. when ERECTION BRIDGING must be installed ERECTION BRIDGING is the bolted diagonal. bridging that is required to be installed prior to releasing the hoisting cables If Table B. indicates that ERECTION BRIDGING is Not Mandatory NM the joists can be spaced out. attached and then bridged in accordance with the SJI Standard Specifications for Longspan. Joists LH Series Section 105 All standard DLH Series joists require ERECTION BRIDGING as. indicated by the BLUE or GRAY SHADED areas in the Load Tables SJI 2005. The required bolted diagonal ERECTION BRIDGING for LH Series joists depends on its. length Where the span of the steel joist is less than 60 feet the bolted diagonal ERECTION. BRIDGING must be installed as the row of bridging nearest the mid span of the joist Where the. span of the steel joist is over 60 feet through 100 feet the required bolted diagonal ERECTION. BRIDGING must be installed as the two rows of bridging nearest the third points of the joist. Where the span of the steel joist is over 100 feet through 144 feet as indicated by the GRAY. shading all rows of bridging are considered ERECTION BRIDGING and must be completely. installed The bridging row s must be anchored to prevent lateral movement of the joist see. Section 105, The shaded areas of the Load Tables were established based on the typical joist self weights.
and the typical minimum top and bottom chords sizes from a survey of joist manufacturers. plus the weight of an erector taken as 300 lbs The equation was developed by Minkoff using. the Rayleigh Ritz method with an assumed sinusoidal lateral and torsional deformation. Minkoff 1975 Galambos 1993, For special joist designs the Specifying Professional cannot check the Minkoff equation. without knowing the exact joist section properties So a conservative comparison can be made. to a standard joist type that would be found in the Load Tables or the joist manufacturer can be. contacted to determine the need for ERECTION BRIDGING Since all ERECTION. BRIDGING will in turn become CONSTRUCTION BRIDGING the more severe. CONSTRUCTION BRIDGING criteria are used to establish the ERECTION BRIDGING. forces sizes and connections,Column Joists, Joists located at or near column lines see Figure 3 are referred to as OSHA Column Joists tie. joists strut joists or OC joists The current OSHA Safety Standards for Steel Erection 29. CFR Part 1926 require that where columns are not framed in at least two directions with solid. structural steel members joists at column lines shall be field bolted and the joist bottom chords. must be restrained by a vertical stabilizer plate OSHA 2001 The bearing seats of Column. Joists will always be provided with slotted holes so that bolts can be inserted at the time of joist. placement Where constructability does not allow a steel joist to be installed directly at the. column the OSHA Safety Standards state that an alternate means of stabilizing the tie joists. shall be installed on both sides near the column, When the current OSHA Safety Standards for Steel Erection Final Rule became effective. it contained the following requirement for Column Joists. Where steel joists at or near columns span 60 feet or less the joist shall be designed with sufficient. strength to allow one employee to release the hoisting cable without the need for erection bridging. An Inspection policy and procedures for OSHA s steel erection standards for construction. was subsequently issued on March 22 2002 and following that on July 18 2003 an OSHA. Notice Extension of enforcement policy on column joists was issued The effective date of. that enforcement policy was originally extended to July 18 2004 or until a new directive was to. be issued OSHA has now extended this policy indefinitely The policy is as follows for all. joists at or near columns that span 60 feet or less employers will be considered to be in. compliance with 1926 757 a 3 if they erect these joists either by 1 installing bridging or. otherwise stabilizing the joist prior to releasing the hoisting cable or 2 releasing the cable. without having a worker on the joists, The SJI conducted extensive research to develop design methods in an effort to meet this. original OSHA provision for Column Joists Emerson 2001 Ziemian et al 2004 The. research was to produce procedures for SJI member companies to use in the design of Column. Joists In attempting to develop these design procedures it was necessary to make assumptions. regarding field conditions that could affect the strength of Column Joists After careful. consideration of the wide range of variability in field conditions the SJI member companies. determined that for some joist lengths there are no existing joist designs that would provide the. necessary stability even with the vertical stabilizer plate Therefore OSHA not withstanding. the SJI can not recommend that employees ever be allowed on unbridged joists SJI member. companies use the DANGER TAG shown in Figure 4 to warn the erection companies that the. Column Joists or tie joists will not support the weight of an employee unless the joist is properly. stabilized and bridged, If a Column or tie joist spans more than 60 feet it needs to be set in tandem with an adjacent.
joist with all bridging installed unless an alternative method of erection is used that provides the. same stability This alternative method needs to have been designed by a qualified person and. be included in a site specific erection plan see OSHA 1926 752 Site layout site specific. erection plan and construction sequence A site specific erection plan allows the employer. to develop alternative means and methods that provide employee protection equivalent to the. provisions of the Federal Regulations, FIGURE 3 COLUMN JOIST BEING CONNECTED BOTTOM CHORD IS FIGURE 4 TYPICAL SJI. KNIFED IN BETWEEN VERTICAL STABILIZER PLATE MANUFACTURER S DANGER TAG. ATTACHED TO COLUMN JOIST,Joist Girders, Joist Girders are primary structural members that are normally supported by structural steel. columns however they can also bear on steel plates on masonry or concrete supports Joist. Girders must be erected singly as shown in Figure 5 They can be underslung and rest on the. top or side of the columns or be square ended and frame into the columns. A loose connection of the bottom chord angles to the column or other support is required. during erection in order to stabilize the bottom chord laterally and to help brace it against. possible overturning These plates knife in between the bottom chord angles that are spaced. apart see Figure 6 A vertical stabilizer plate is required to be furnished on each column by. the structural steel supplier minimum size 3 4 x 6 x 6 in and must extend at least 3 in below. the bottom chord of the Joist Girder If a stabilizer plate cannot be used because of a. constructability issue some other means of laterally stabilizing the Joist Girder must be. provided Any final connection if required of the Joist Girder bottom chord to the column. should be in accordance with instructions from the EOR. Since Joist Girders are erected without ERECTION BRIDGING a minimum stiffness. relative to the overall length is required and is given in section 1003 4 a The radius of. gyration of the Joist Girder top chord about the vertical axis shall not be less than the Joist. Girder span divided by 575, FIGURE 5 JOIST GIRDER BEING SET ON TWO FIGURE 6 JOIST GIRDER BEARING ON STRUCTURAL STEEL COLUMN. COLUMNS WITH TWO CONNECTORS WITH VERTICAL STABILIZER PLATE. BRIDGING FOR CONSTRUCTION LOADS, After any required ERECTION BRIDGING is installed and the hoisting cables have been released. the remaining bridging rows these would be called CONSTRUCTION BRIDGING need to be. installed before the application of additional construction loads Under no circumstances are. construction loads of any description to be placed on unbridged joists As previously described. many joists are laterally unstable until the joists are properly bridged and the bridging and the. joists are properly anchored The joists should be completely bridged immediately after final. placement and end attachment is completed in accordance with OSHA and SJI requirements. Construction loads are defined in the OSHA Safety Standards as any load other than the. employee s the joists and the bridging bundles These loads include the weight of metal deck. bundles and individual sheets being placed the weight of multiple Erectors placing the deck. and the equipment loads such as welding machines and leads hand tools bridging for adjacent. bays etc The Standard strictly prohibits placing construction loads on unbridged joists and. gives the proper procedure for landing bridging bundles on unbridged joists see. 29CFR1926 757 e 1 2 and 3 It is critical that the magnitude of construction loads on any. one joist be limited and it is advisable that the loads be placed as close as possible to the ends of. the joist There is an exception for the placement of a bundle of decking after the installation of. at least one bridging row but not all bridging rows if certain stringent conditions are met Any. Erector who allows construction loads to be placed on unbridged joists is in direct violation of. the Federal Regulation as well as the Steel Joist Institute s K Series Specifications Section 6. and the LH and DLH Series Specifications Section 105 SJI 2005 and may be held liable for. any injuries sustained if an accident should occur. The SJI Standard Specifications for Open Web Steel Joists K Series Section 5 4 SJI 2005. requires that each bridging connection resist a nominal unfactored horizontal force of not less. than 700 pounds Section 5 4a The spacing of the bridging rows shall be determined by the. radius of gyration of the top chord about its vertical axis and shall not be less than l 145 and to. meet this criteria the quantity of top chord bridging rows shall not be less than as shown in. Table 5 4 1 The number of rows of bottom chord bridging shall not be less than the number of. top chord rows Section 5 4c the top and bottom chord bridging rows may be spaced. independently,TABLE 5 4 1,NUMBER OF ROWS OF TOP CHORD BRIDGING.
Refer to the K Series Load Table and Specification Section 6 for required bolted diagonal bridging. Distances are Joist Span lengths in feet See Definition of Span preceding Load Table. Section One Two Three Four Five,Number Row Rows Rows Rows Rows. 1 Up thru 16 Over 16 thru 24 Over 24 thru 28,2 Up thru 17 Over 17 thru 25 Over 25 thru 32. 3 Up thru 18 Over 18 thru 28 Over 28 thru 38 Over 38 thru 40. 4 Up thru 19 Over 19 thru 28 Over 28 thru 38 Over 38 thru 48. 5 Up thru 19 Over 19 thru 29 Over 29 thru 39 Over 39 thru 50 Over 50 thru 52. 6 Up thru 19 Over 19 thru 29 Over 29 thru 39 Over 39 thru 51 Over 51 thru 56. 7 Up thru 20 Over 20 thru 33 Over 33 thru 45 Over 45 thru 58 Over 58 thru 60. 8 Up thru 20 Over 20 thru 33 Over 33 thru 45 Over 45 thru 58 Over 58 thru 60. 9 Up thru 20 Over 20 thru 33 Over 33 thru 46 Over 46 thru 59 Over 59 thru 60. 10 Up thru 20 Over 20 thru 37 Over 37 thru 51 Over 51 thru 60. 11 Up thru 20 Over 20 thru 38 Over 38 thru 53 Over 53 thru 60. 12 Up thru 20 Over 20 thru 39 Over 38 thru 53 Over 53 thru 60. Last digit s of joist designation shown in Load Table. See Section 5 11 for additional bridging required for uplift design. The SJI Standard Specifications for Longspan Steel Joists LH Series and Deep Longspan. Steel Joists DLH Series requires that each bridging connection to the joist must be able to. resist a horizontal force not less than that specified in Table 104 5 1 Section 104 5e Where. two attachment points to a joist are utilized each attachment must be able to resist one half of. the bridging force given in the table The spacing of the bridging rows shall be determined by. the radius of gyration of the top chord about its vertical axis and shall not be less than l 170. and to meet this criteria the maximum spacing of lines of top chord bridging shall not exceed. the values in Table 104 5 1 The number of rows of bottom chord bridging shall not be less. than the number of top chord rows the top and bottom chord bridging rows may be spaced. independently Section 104 5d SJI 2005,TABLE 104 5 1. LH DLH MAXIMUM SPACING OF,HORIZONTAL BRACING,SECTION N LINES OF TOP CHORD. UMBER BRIDGING,02 03 04 11 0 3352 mm 400 1779,05 06 12 0 3657 mm 500 2224.
07 08 13 0 3962 mm 650 2891,09 10 14 0 4267 mm 800 3558. 11 12 16 0 4876 mm 1000 4448,13 14 16 0 4876 mm 1200 5337. 15 16 21 0 6400 mm 1600 7117,17 21 0 6400 mm 1800 8006. 18 19 26 0 7924 mm 2000 8896, Number of lines of bridging is based on joist clear span dimensions. Last two digits of joist designation shown in load table. Nominal bracing force is unfactored, The bracing force that a joist imparts to the bridging is based on three assumptions The.
first is an initial out of straightness taken as L 920 The second is the resultant total nominal. bracing force of 0 0044P Then since horizontal bridging rows must be continuous and each. joist is braced from both sides the total bracing force is divided by two and rounded to achieve. 0 0025P where P represents the chord axial force and the third assumption relates to the. construction stress in the top chord and the axial force P that it creates For K Series joists the. bridging criteria are based on a top chord axial construction ultimate stress Fcr of. approximately 17 ksi Due to the continuity of the top chord on either side of the bridging. attachments a k factor of 0 9 is used in calculating the top chord slenderness ratio Hence for. an ultimate Euler stress of approximately 17 ksi and a k factor of 0 9 the permissible. slenderness ratio l ryy is set to 145 for K Series as given above. LH and DLH Series joists are similar except that the assumed construction stress is taken. as approximately 12 ksi and the resultant slenderness limit l ryy is 170. Therefore the nominal compressive force that accumulates in a horizontal bridging row is. Pbr 0 0025 n At Fconstruction, Fconstruction is approximately 17 ksi for K Series joists and 12 ksi for LH and. DLH Series joists as noted above,At is the top chord area. n the number of joists, For horizontal bridging n is taken as eight joist spaces This is due in part to the fact that the. construction loads tend to be localized rather than spread uniformly over an entire bay and to. the probability that not all joists in a bay would exhibit the maximum out of straightness at any. given time For horizontal bridging the bracing force Pbr must be taken in compression. Diagonal bridging creates a load path whereby the forces are resolved at each braced joist space. and do not accumulate However recall that the bracing force was divided by two on the. presumption of continuous bridging on each side of the joist chord Since continuity is not. required of diagonal bridging rows and to allow the diagonal bridging force to be considered. only in tension then n is taken as two for diagonal bridging. The tables provided in the SJI Specifications for bridging sizes are based upon the force Pbr. for the typical top chord areas for a given designation Table 2 6 1a of the SJI Code of Standard. Practice gives the maximum joist spacing for certain horizontal bridging sizes based on joist. chord section numbers for K Series joists and using k 0 9 for the bridging design and Table. 2 6 1b provides the same for LH and DLH Series joists Diagonal bridging is only subjected. to tension forces and so the bridging size is governed by a slenderness limit between. connections of 200 rather than by strength,TABLE 2 6 1a. K SERIES JOISTS,MAXIMUM JOIST SPACING FOR HORIZONTAL BRIDGING.
BRIDGING MATERIAL SIZE,Round Rod Equal Leg Angles, 1 2 dia 1 x 7 64 1 1 4 x 7 64 1 1 2 x 7 64 1 3 4 x 7 64 2 x 1 8 2 1 2 x 5 32. 13 mm 25 x 3 mm 32 x 3 mm 38 x 3 mm 45 x 3 mm 52 x 3 mm 64 x 4 mm. NUMBER r 0 20 r 0 25 r 0 30 r 0 35 r 0 40 r 0 50, 3 30 mm 5 08 mm 6 35 mm 7 62 mm 8 89 mm 10 16 mm 12 70 mm. ft in mm ft in mm ft in mm ft in mm ft in mm ft in mm ft in mm. 3 3 5 0 6 3 7 6 8 7 10 0 12 6,991 1524 1905 2286 2616 3048 3810. 3 0 4 8 6 3 7 6 8 7 10 0 12 6,914 1422 1905 2286 2616 3048 3810. 2 7 4 0 5 8 7 6 8 7 10 0 12 6,787 1219 1727 2286 2616 3048 3810.
Refer to last digit s of Joist Designation, Connection to joist must resist a nominal unfactored 700 pound force 3114 N. Recently the SJI has begun to investigate the difference between the assumed K Series. construction stress of 17 ksi verses 12 ksi for LH and DLH Series joists Preliminary findings. indicate that the construction stress has very little to do with the chosen joist series but is. heavily influenced by both the span and depth of a joist For a given span length and joist. spacing the construction load will arguably be the same regardless of joist depth while the top. chord construction stress will clearly be less for a deeper joist On this basis equations were. developed for the new SJI Standard Specifications for Composite Steel Joists CJ Series SJI. 2007 in which Fconstruction and the top chord slenderness limit varies depending on the depth and. span length as follows,Fconstruction 12 2 ksi, l br 100 0 67 d j 40 j r y but not greater than l br 170 ry. It is anticipated that a similar methodology may be adopted for K LH and DLH Series joists. in the future However they would not exactly match the CJ Series equations because the CJ. Series allows for an ultimate top chord construction stress in excess of 17 ksi This is due to the. fact that composite joist top chords are inherently smaller than comparable non composite top. chord sizes and the maximum span to depth ratio is greater for composite than non composite. TABLE 2 6 1b,LH SERIES JOISTS,MAXIMUM JOIST SPACING FOR HORIZONTAL BRIDGING. SPANS OVER 60 ft 18 3 m REQUIRE BOLTED DIAGONAL BRIDGING. BRIDGING MATERIAL SIZE,Equal Leg Angles, 1 x 7 64 1 1 4 x 7 64 1 1 2 x 7 64 1 3 4 x 7 64 2 x 1 8 2 1 2 x 5 32. 25 x 3 mm 32 x 3 mm 38 x 3 mm 45 x 3 mm 52 x 3 mm 64 x 4 mm. r 0 20 r 0 25 r 0 30 r 0 35 r 0 40 r 0 50,5 08 mm 6 35 mm 7 62 mm 8 89 mm 10 16 mm 12 70 mm.
ft in mm ft in mm ft in mm ft in mm ft in mm ft in mm. 02 03 04 4 7 1397 6 3 1905 7 6 2286 8 9 2667 10 0 3048 12 4 3759. 05 06 4 1 1245 5 9 1753 7 6 2286 8 9 2667 10 0 3048 12 4 3759. 07 08 3 9 1143 5 1 1549 6 8 2032 8 6 2590 10 0 3048 12 4 3759. 09 10 4 6 1372 6 0 1829 7 8 2337 10 0 3048 12 4 3759. 11 12 4 1 1245 5 5 1651 6 10 2083 8 11 2718 12 4 3759. 13 14 3 9 1143 4 11 1499 6 3 1905 8 2 2489 12 4 3759. 15 16 4 3 1295 5 5 1651 7 1 2159 11 0 3353,17 4 0 1219 5 1 1549 6 8 2032 10 5 3175. Refer to last two digit s of Joist Designation, Connection to joist must resist force listed in Table 104 5 1. In certain design applications that utilize bottom bearing or square ended joists the product. is designed to bear on the bottom chord This produces a top heavy condition Therefore. their ends must be restrained laterally in accordance with the SJI Standard Specifications K. Series Section 5 4d or LH and DLH Series Section 104 5f SJI 2005 This is accomplished. by means of an additional row of diagonal bridging placed at or near the bearing support ends of. the joists as they are being erected Where a bottom bearing joist is extended beyond its support. to form a cantilevered end a row of diagonal bridging near the support should first be installed. In addition the structural drawings may indicate a row of diagonal bridging in the cantilevered. portion to provide lateral stability If the joists have bottom chords extended over and. connected to a column beam wall or other structure the connection should be made in. accordance with the structural drawings and or instructions from the EOR. BRIDGING FOR PERMANENT LOADS, Top chord bridging serves a role as PERMANENT BRIDGING in the absence of a deck. diaphragm as is the case with a standing seam roof applied directly to the joist top chords. Sections 5 8 g and 104 9 g of the SJI Standard Specifications SJI 2005 for K Series and. LH DLH Series joists respectively provide the requirements for the horizontal bridging. design The compressive force equation is,Pbr 0 0025nP. This equation is similar to the equation given above for CONSTRUCTION BRIDGING but. here n is not limited to eight and is equal to the total number of joists between end anchors P. represents the actual top chord design force rather than the chord area times an arbitrary. construction stress, Bottom chord bridging is always PERMANENT BRIDGING and either limits slenderness.
for bottom chords in tension or braces the bottom chord laterally for compression forces such. as those present in a net uplift loading case Traditionally and for simplicity in the field the. bottom chord bridging size is equal to the size as determined for the top chord. When uplift forces are a design consideration a row of bottom chord bridging is required. near each end of shortspan joists in accordance with the SJI Standard Specifications K Series. Sections 5 6 and 5 11 and longspan joists in accordance with the SJI Standard Specifications. LH and DLH Series Sections 104 7 and 104 12 SJI 2005. For a Joist Girder the ends are laterally braced by the stabilizer plates as discussed. previously However additional brace points may be required along the girder span length. either to limit the slenderness ratio for bottom chords in tension or to laterally brace the bottom. chord in compression In this case PERMANENT BRIDGING is added in the form of bottom. chord bracing BCB or knee bracing This consists of separate individual pieces of material. furnished by the joist supplier to be attached either by bolting or welding from the bottom. chord of the joist to the bottom chord of the Joist Girder. CONCLUSIONS, This paper has summarized the Steel Joist Institute and OSHA requirements for steel joist and. Joist Girder bridging and has categorized those requirements by the three functional purposes. of bridging As a complement to what is in the Specifications some of the underlying theory. equations and references for bridging have been provided Future research with regard to joist. bridging is likely to include a review of the construction stress levels a unification of the K. Series and LH and DLH Series bridging requirements and a better understanding of the. accumulation of bridging forces due to net uplift,REFERENCES. Emerson M R Stability of Unbraced Steel Joists Subject to Mid Span Loading A Thesis Presented to the Faculty. of Bucknell University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Civil. Engineering Lewisburg PA 2001, Galambos T V Bracing of Trussed Beams SSRC Specialty Conference IS YOUR STRUCTURE SUITABLY. BRACED Milwaukee WI April 1993, Hodge P T and Galambos T V A theoretical study of the lateral performance of steel joists when restrained by. bridging and standing seam deck In Partial Fulfillment of a Master s of Science in Civil Engineering at the. University of Minnesota MN 1986, Minkoff R M Stability of Steel Joists During Erection Research Report No 39 Washington University Aug.
OSHA Federal Register Department of Labor Occupational Safety and Health Administration 29 CFR Part 1926. Safety Standards for Steel Erection Final Rule 1926 757 Open Web Steel Joists Washington DC January. SJI 42nd Edition Catalog Standard Specifications Load Tables Weight Tables for Steel Joists and Joist Girders. Steel Joist Institute Myrtle Beach SC 2005, SJI First Edition Composite Steel Joist Catalog Standard Specifications for Composite Steel Joists Steel Joist. Institute Myrtle Beach SC 2007, SJI Technical Digest 9 Handling and Erection of Steel Joists and Joist Girders Steel Joist Institute Myrtle. Beach SC 2006, Ziemian R D Schwarz J E Emerson M R and Potts D R Stability of Unbraced Steel Joists Subject to. Mid span Loading 2004 Annual Stability Conference Structural Stability Research Council Long Beach.


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