Safety in a Second Guardrail Testing

Transcription

1 BMT Fleet Technology Limited DB01 (Rev. DRAFT01) Safety in a Second Guardrail Testing Reference: 7830.FR (Issue 02) Date: 19 March 2012 BMT Fleet Technology Limited accepts no liability for any errors or omissions or for any loss, damage, claim or other demand in connection with the usage of this report, insofar as those errors and omissions, claims or other demands are due to any incomplete or inaccurate information supplied to BMT Fleet Technology Limited for the purpose of preparing this report.

2 7830.FR (Issue 02) SAFETY IN A SECOND GUARDRAIL TESTING FINAL REPORT 19 March 2012 Submitted to: Steve Beaudot Safety in a Second 532 Montreal Rd., Suite 436 Ottawa, Ontario K1K 4R4 Submitted by: BMT FLEET TECHNOLOGY LIMITED 311 Legget Drive Kanata, ON K2K 1Z8 BMT Contact: Dale Braun Tel: , Ext. 333 Fax: dbraun@fleetech.com BMT Fleet Technology Limited accepts no liability for any errors or omissions or for any loss, damage, claim or other demand in connection with the usage of this report, insofar as those errors and omissions, claims or other demands are due to any incomplete or inaccurate information supplied to BMT Fleet Technology Limited for the purpose of preparing this report.

3 BMT DOCUMENT QUALITY CONTROL DATA SHEET REPORT: Safety in a Second Guardrail Testing DATE: 19 March 2012 PREPARED BY: Dale Braun, M.Eng. P.Eng. Senior Engineer REVIEWED AND APPROVED BY: Aaron Dinovitzer, P.Eng Vice President Safety in a Second Guardrail Testing i

4 REVISION HISTORY RECORD Rev. No. Date of Issue Description of Change Issue Feb Initial Issue with drawing comments. Issue Mar Issued as Test Report only. Safety in a Second Guardrail Testing ii

5 ACRONYMS AND ABBREVIATIONS A m Shear area of the effective fusion face in mm 2 A w Area of the effective weld throat in mm 2 BMT FTL BMT Fleet Technology Limited F u Ultimate tensile strength of steel in MPa HSS Hollow structural section kn KiloNewton (or, lbf) lbf Pounds force (or kn) mm Millimetre MPa MegaPascals NDE Non-destructive examination X u Electrode ultimate tensile strength in MPa φ w Resistance factor for welded connections, 0.67 Safety in a Second Guardrail Testing iii

6 TABLE OF CONTENTS 1 GUARDRAIL SAFETY LOOP TEST Introduction Scope of Work STRUCTURAL CALCULATIONS Safety Loop for Fall-Arrest Attachment Shear Capacity of Bent Bar Safety Loop Welds at Base Plate and Square HSS Post Square HSS Post Welds at Base Plate Guardrail Post Guardrail Panel HSS Rail Sections Welded Wire Mesh Toeboard Mounting Pins for Adjustable Panel STATIC LOAD TENSION TESTS OF SAFETY LOOP STATIC LOAD TESTING OF POSTS AND PANELS Guardrail Posts Guardrail Panels CONCLUSIONS AND RECOMMENDATIONS Safety in a Second Guardrail Testing iv

7 LIST OF FIGURES Figure 4.1: Guardrail Post Safety Loop Tension Test Arrangement...7 Figure 4.2: Typical Guardrail Post Sample in Test Apparatus...8 Figure 4.3: Recorded Load-Displacement...9 Figure 5.1: Load Applied Laterally at Top of Post (1350 n or 300 lb shown) Figure 5.2: Load Applied Vertically Downward at Top of Post (1350 N or 300 lb shown) Figure 5.3: Load Applied Laterally at Top Rail (1350 N or 300lb shown) Figure 5.4: Load Applied Laterally at Panel Mid-Height (800 N or 180 lb shown) Figure 5.5: Load Applied Laterally at Toeboard (534 N or 120 lb shown) Figure 5.6: Load Applied Vertically Downward at Top Rail Figure 5.7: Load Applied Vertically Downward at Panel Mid-Height Safety in a Second Guardrail Testing v

8 REFERENCES A. Ontario Health and Safety Act, Ontario Regulation 213/91 Construction Projects, Part II: Section 26; B. CAN/CSA S16-01 Limit States Design of Steel Structures, 9 th Edition (2007); C. CSA Standard W59-03 Welded Steel Construction (Metal Arc Welding), (2003); and, D. CSA Standard W Certification of Companies for Fusion Welding of Steel (2003). Safety in a Second Guardrail Testing vi

9 1 GUARDRAIL SAFETY LOOP TEST 1.1 Introduction Safety in a Second supplied BMT Fleet Technology Limited (BMT FTL) with two (2) sample Guardrail Posts; two (2) fixed-span Guardrail Panels; and, two (2) adjustable-span Guardrail Panels for structural testing and evaluation. The evaluation consisted of (i) a review of the detailed drawings; and, (ii) for each Guardrail Post sample provided, a static load tension test of the fall-arrest attachment safety loop; and, (iii) for each Guardrail Post and Panel, a static load test to demonstrate the performance with respect to loads prescribed by the Ontario Health and Safety Act, Ontario Regulation 213/91 Construction Projects, Part II: Section Scope of Work The evaluation included the following activities: a. Review and Document Structural Design of the Guardrail System i. The configuration and dimensions of sample Guardrail Posts and Panels (fixed-span and adjustable-span) as provided by Safety in a Second are reviewed, including a visual check of the welded connections. ii. iii. By CAN/CSA S16-01 the factored resistances of the post and guardrail components are calculated based on the material information, details and dimensions described on the drawings. The calculated factored resistances of the components are compared to the loading requirements prescribed by the Ontario Health and Safety Act, Ontario Regulation (O.Reg.) 213/91, Part II: Section 26. b. Test the Guardrail Posts and Panels i. Tests are completed to demonstrate the load-carrying capacity of the two (2) sample Guardrail Posts and four (4) sample Guardrail Panels (fixed-span and adjustable-span) when subject to the minimum loads outlined in O.Reg. 213/91 Part II: Section 26. Additional loads are applied, up to a factor of 2.0, to demonstrate adequate safety margins in the design. ii. For the testing of the fall-arrest attachment lug, a tensile load was applied to the safety loop of the Guardrail Posts, aligned with the base plate. A load corresponding to the prescribed value of 22 kn (or, 5,000 lbf) was applied to demonstrate compliance for fall arrest attachment systems. The tensile test subsequently is extended to an overload level of 44 kn (or, 10,000 lbf) at a factor of safety of 2.0 without failure. c. Documentation, including a summary of the calculations, testing process and results. Safety in a Second Guardrail Testing 1

10 2 STRUCTURAL CALCULATIONS The following calculations were completed with reference to CAN/CSA S16-01 to determine the capacity of the members and welded connections related to the safety loop and for the resistance of the post and panel components. 2.1 Safety Loop for Fall-Arrest Attachment The structural resistance of the welds at the fall-arrest attachment on the Guardrail Post is evaluated by CAN/CSA S16-01 as follows Shear Capacity of Bent Bar The bent bar used for the safety loop has a nominal diameter of 5/8 (or, 15.9 mm) and a minimum specified yield strength of 350 MPa. The cross-sectional area of the rod is 199 mm 2. The factored shear resistance of the rod is: [1] Since V R P = 22 kn for fall-arrest, the bent rod is considered adequate in shear or tension Safety Loop Welds at Base Plate and Square HSS Post As fabricated, the welds associated with the safety loop correspond to partial penetration flare bevel groove welds with a 1/8 (or, 3.2 mm) fillet weld added. The minimum length of each weld is 30 mm used for calculation. The width of the fusion face for these welds is taken as 3/16 (or, 4.8 mm). The effective throat for these welds is taken as 1/8 (or, 3.2 mm). At the safety loop, there are four such welds connecting the loop to both the base plate and the square HSS post. The factored shear resistance of the welds is taken as the lesser of: (i) [2] (ii) [3] Where: φ w = 0.67, the resistance factor for welded connections; A m = 4.6 mm 30 mm = 138 mm 2, the area of the fusion face; A w = 3.2 mm 30 mm = 96 mm 2, the area of the effective weld throat; Safety in a Second Guardrail Testing 2

11 F u = 450 MPa, the ultimate strength for 350W steel by CAN/CSA G40.21M; and, X u = 490 MPa, the matching E490XX electrode ultimate tensile strength for 350W steel by CAN/CSA G40.21M. The calculated limiting shear resistance of the welded connection for the safety loop is 84 kn, or approximately 18,880 lbf Square HSS Post Welds at Base Plate As fabricated, the welds associated with the square HSS post at the base correspond to 3 legs of 1/8 (or, 3.2 mm) fillet welds around the perimeter of the HSS section (total length of 102 mm) plus one 30 mm leg of the flare bevel groove weld associated with the safety loop connection to the base plate. For the fillet welds, the width of the fusion face is taken as 1/8 (or, 3.2 mm). The effective throat for the 1/8 (or, 3.2 mm) welds is taken as mm = 2.3 mm The contribution from the flare bevel groove weld corresponds to 0.25 times the limiting value from Section 2.1, or kn = 21 kn. The factored shear resistance of the fillet welds is taken as the lesser of: (i) [4] (ii) [5] Where: φ w = 0.67, the resistance factor for welded connections; A m = 3.2 mm 102 mm = mm 2, the area of the fusion face; A w = 2.3 mm 102 mm = mm 2, the area of the effective weld throat; F u = 450 MPa, the ultimate strength for 350W steel by CAN/CSA G40.21M; and, X u = 490 MPa, the matching E490XX electrode ultimate tensile strength for 350W steel by CAN/CSA G40.21M. The calculated limiting shear resistance of the fillet welds is 51 kn, or approximately 11,465 lbf. Including the contribution for the single leg of the flare bevel groove weld, the total factored shear resistance for the welded connection at the base of the square HSS post is 51 kn + 21 kn = Safety in a Second Guardrail Testing 3

12 72 kn, or 16,186 lbf. Since the calculated capacity exceeds the fall-arrest attachment load of 22 kn (by a factor of 3.3), the welded connection is considered adequate. 2.2 Guardrail Post The structural resistance of the guardrail post, in response to an applied lateral (inward or outward) load is evaluated. For the evaluation of the post itself, it is assumed the Guardrail Post is anchored at the base plate in accordance with the requirements stated on the corresponding drawing. As fabricated, the post corresponds to a section 42 (or, 1067 mm) long section of HSS /8. The corresponding cross-sectional area and section modulus for the post is 418 mm 2 and mm 3, respectively. The factored resistance of the post is considered in terms of the shear and moment resistance, as follows: [6] [7] Note the contribution of the 1/2 (or, 12.7 mm) round bar brace is excluded to be conservative. For a load, P, of 675 N (or, 150 lb) applied at the top of the post (as for a cantilever), the corresponding specified shear and moment are as follows: [8] [9] In each case, the shear and moment resistance exceeds the applied shear and moment. For the limiting condition of bending moment at the base of the post, the factored resistance exceeds the specified moment by a factor of The factor of safety for the post associated with the resistance to bending about the base will be improved if the 1/2 round bar brace is included in the calculation. Thus, the resistance of the post is considered to be adequate with respect to the required loads for design. 2.3 Guardrail Panel The Guardrail Panel structure consists of HSS 1 1 1/8 with a welded wire mesh 3/16 (or, 4.8 mm) in diameter and with a spacing of 4 4. A toeboard is fabricated from a channel section C ga. (150 mm deep with a 25 mm flange and 2.0 mm thick). The HSS rail sections, having a maximum unsupported span of 2286 mm (or, 7.5 ), and the wire mesh are evaluated for the maximum required loads of 675 N (or, 150 lb) and 450 N (or, 100 lb), Safety in a Second Guardrail Testing 4

13 respectively. laterally. The toeboard is evaluated for a maximum load of 225 N (or, 50 lb) applied HSS Rail Sections For the HSS 1 1 1/8, the cross-sectional area and section modulus correspond to 275 mm 2 and mm 3, respectively. The minimum specified yield strength is 350 MPa. The factored resistance of the rail is considered in terms of the shear and moment resistance, as follows: [10] [11] For a load, P, of 675 N (or, 150 lb) applied to the top rail (whether laterally or vertically downward), the maximum shear occurs with the load adjacent to the end support, such that: [12] For a load, P, of 675 N (or, 150 lb) applied to the top rail (whether laterally or vertically downward), the maximum bending moment occurs with the load at mid-span, as follows: [13] Thus, since V R V max and M R M max, the Guardrail Panel HSS rail sections are considered adequate Welded Wire Mesh The wire used in the welded mesh has a diameter of 3/16 (or, 4.8 mm) with a minimum specified yield strength of 400 MPa. The nominal cross-sectional area is 18.1 mm 2. The tensile resistance of a single wire is as follows: The shear resistance of a single wire is as follows: [14] Since for a single wire T R P = kn and V R P, the wire is considered adequate in tension. [15] Safety in a Second Guardrail Testing 5

14 2.3.3 Toeboard The toeboard is fabricated from a piece of steel sheeting, 2.0 mm thick (or, 14 ga.) bent into the shape of a channel section and having an overall depth of 150 mm and a flange width of 25 mm. The corresponding cross-sectional area and minimum section modulus (for weak axis bending) are 390 mm 2 and mm 3. The maximum unsupported span of the toeboard channel is 2134 mm (or, 7 ). The minimum specified yield strength is 300 MPa. The factored resistance of the toeboard is considered in terms of the shear and moment resistance (with weak-axis bending), as follows: [16] [17] For a load, P, of 225 N (or, 50 lb) applied laterally to the toeboard, the maximum shear occurs with the load adjacent to the end support, as follows: For a load, P, of 225 N (or, 50 lb) applied laterally to the toeboard, the maximum bending moment occurs with the load at mid-span, as follows: [18] [19] Thus, since V R V max and M R M max, the toeboard channels are considered adequate Mounting Pins for Adjustable Panel The mounting pins for the adjustable panel correspond to 1/2 (or, 12.7 mm) diameter round bar welded to the sections of HSS 1 1 1/8 at two locations. The minimum specified yield strength of the round bar is 350 MPa. Each round bar is welded to the HSS section with a 1/8 (or, 3.2 mm) fillet weld all-around. The total length of weld is taken as πd = ( mm) = 40 mm. The factored shear resistance of one fillet weld is taken as the lesser of: (i) [20] (ii) [21] Thus, the calculated limiting shear resistance of one fillet weld is 20 kn, which exceeds the maximum specified shear of kn. Safety in a Second Guardrail Testing 6

15 3 STATIC LOAD TENSION TESTS OF SAFETY LOOP Two Guardrail Post samples were supplied and tested to confirm the performance of the safety loops in response to an applied tensile load of 22 kn (or, 5,000 lbf). The test assembly included a steel plate (thickness 12.7 mm), indicated in the schematic of Figure 3.1, to which the base plate of the Guardrail Post samples are bolted. The tension tests were conducted in a 300,000 lbf Satec Universal Baldwin test machine, as shown in Figure 3.2 for a typical Guardrail Post. Each test was completed at a quasi-static loading rate, with a constant cross-head displacement rate of 1/8 (or, 3.2 mm) per minute. The test includes a record of the load versus displacement, with the latter corresponding to the movement of the test frame cross-head. Plots illustrating the recorded load versus cross-head displacement are shown in Figure 3.3. For either Sample 1 or Sample 2, the maximum cross-head displacement recorded is approximately 0.60 (or, 15 mm) at the prescribed load level of 5,000 lbf. Note that the displacement of the safety lug does not correspond to that for the cross-head and would be less. Displacements of the specimens were not measured for this test. The condition of the safety loop for each sample was checked visually following each test. In each case, and up to the maximum applied load of 10,000 lbf, no deformation of the loops or the associated welded connections was observed. Reaction Steel connection plate for test apparatus Applied tensile load Figure 3.1: Guardrail Post Safety Loop Tension Test Arrangement Safety in a Second Guardrail Testing 7

16 (a) Overview (b) Safety Loop Connection to Test Apparatus Figure 3.2: Typical Guardrail Post Sample in Test Apparatus Safety in a Second Guardrail Testing 8

17 Maximum Load 10,054 lbf Applied Load, lbf Cross-head Displacement, in (a) Post Sample Maximum Load 10,315 lbf Applied Load, lbf Cross-head Displacement, in (b) Post Sample 2 Figure 3.3: Recorded Load-Displacement Safety in a Second Guardrail Testing 9

18 4 STATIC LOAD TESTING OF POSTS AND PANELS The Guardrail Posts and Panels provided were tested to demonstrate the performance with respect to the requirements of O.Reg. 213/91, to support the applied loads as follows: A point load of 675 N (150 lb) applied laterally to the top rail; A point load of 450 N (100 lb) applied vertically downward to the top rail; A point load of 450 N (100 lb) applied in a lateral or vertical direction to the mid-rail (or at mid-height); and, A point load of 225 N (50 lb) applied laterally to the toeboard. 4.1 Guardrail Posts To test the Guardrail Posts, a minimum lateral load of 675 N (150 lb) is applied at the top, consistent with the first objective of the applied loads described in O.Reg. 213/91. For the lateral load, each post was oriented horizontally and clamped at the base as a cantilever, consistent with the fixed support condition required for installation. A load of 675 N (150 lb) was applied at the end without permanent deformation. Subsequently, a maximum load of 1350 N (300 lb) was applied, corresponding to a factor of safety of 2.0. The tests were completed for both orientations of the posts for an applied inward or outward lateral load, as shown in Figure 4.1. The load was also applied vertically downward at the top support for the Guardrail Panel, as shown in Figure 4.2. In all cases, the Guardrail Posts supported the applied loads as required and for the overload condition with no plastic deformation observed. (a) Inward (b) Outward Figure 4.1: Load Applied Laterally at Top of Post (1350 n or 300 lb shown) Safety in a Second Guardrail Testing 10

19 Figure 4.2: Load Applied Vertically Downward at Top of Post (1350 N or 300 lb shown) 4.2 Guardrail Panels In the tests for which the load is to be applied vertically (with respect to its orientation when installed) the Guardrail Posts are spaced at 2290 mm (or, about 7.5 ) and used to support the panel samples. When the load is to be applied laterally (with respect to its orientation when installed), the panels were arranged horizontally on supports spaced at 2290 mm. The supports are not clamped and allow rotation of the panel ends consistent with a simple support condition. The applied minimum and maximum loads for each panel are listed in Table 4.1 and Table 4.2 for the loads applied laterally and vertically downward, respectively. Photographs of the Guardrail Panels subject to the various loads are shown in Figure 4.3 to Figure 4.7. Note the loads applied near the end supports were located approximately 180 mm (or, 7 ) from the support. Safety in a Second Guardrail Testing 11

20 Table 4.1: Guardrail Panel Laterally Applied Loads Minimum Load by O.Reg. 213/91 Maximum Applied Load Mid-Span Near End Support Mid-Span Near End Support Top Rail Panel Mid-Height Toeboard Table 4.2: Guardrail Panel Vertically Downward Applied Loads Minimum Load by O.Reg. 213/91 Maximum Applied Load Mid-Span Near End Support Mid-Span Near End Support Top Rail Panel Mid-Height Toeboard N/A N/A N/A N/A In all cases, the Guardrail Panels supported the applied loads as required and for the overload condition with no plastic deformation observed in the primary structure. For loads applied directly to the wire mesh, some minor deformation was noted. (a) Mid-span (b) Near end support Figure 4.3: Load Applied Laterally at Top Rail (1350 N or 300lb shown) Safety in a Second Guardrail Testing 12

21 (a) Mid-span (b) Near end support Figure 4.4: Load Applied Laterally at Panel Mid-Height (800 N or 180 lb shown) (a) Fixed-span panel (b) Adjustable panel Figure 4.5: Load Applied Laterally at Toeboard (534 N or 120 lb shown) Safety in a Second Guardrail Testing 13

22 (a) Mid-span (534 N or 120 lb shown) (b) Near end support (800 N or 180 lb shown) Figure 4.6: Load Applied Vertically Downward at Top Rail (a) Fixed-span panel (400 N or 90 lb shown) (b) Adjustable panel (800 N or 180 lb shown) Figure 4.7: Load Applied Vertically Downward at Panel Mid-Height Safety in a Second Guardrail Testing 14

23 5 CONCLUSIONS AND RECOMMENDATIONS Safety in a Second supplied two sample Guardrail Posts and four sample Guardrail Panels with corresponding detailed drawings to BMT Fleet Technology Limited (BMT FTL) for evaluation of the safety loop as a fall arrest attachment point and conformance with the loading requirements of O.Reg. 213/91 Part II: Section 26. The evaluation consisted of (i) a review of the detailed drawings; (ii) a static load tension test of the safety loop; and, (iii) a set of static load tests to confirm the performance with respect to the Ontario regulation. Based on the material strengths identified on the drawings, this evaluation has demonstrated that: The calculated factored resistance of the welded connections associated with the safety loop of 72 kn (or, 16,186 lbf) exceeds the proposed applied load of 22 kn (or, 5,000 lbf). The calculated factored resistances of the components of the Guardrail Posts and Panels exceed the loads prescribed by O.Reg. 213/91 Part II: Section 26. The structural performance of the safety loop and welded connection as tested meets the requirement to carry an applied static load of 22 kn (or, 5,000 lbf) without plastic deformation observed. Further, the structural performance of the safety loop and welded connection as tested was shown to carry an applied static load of up to 44 kn (or, 10,000 lbf), equivalent to 2.0 times the prescribed load level, without noticeable deformation. The performances of the Guardrail Post and Guardrail Panels as provided satisfy the loading requirements prescribed by O.Reg. 213/91 Part II: Section 26 as validated by the static load tests completed. The test results described in this report are specific to the geometry and materials used to fabricate the samples provided. Different load carrying capacities will be measured if different materials or structural configurations are used to fabricate the assembly. It is also noted that the capacity of the anchor bolts to support the prescribed load was not considered in this investigation. Safety in a Second Guardrail Testing 15

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