Investigating the performance of slip resistant winter footwear. Jennifer Hsu

Transcription

1 Investigating the performance of slip resistant winter footwear Jennifer Hsu Falls and Mobility Network Meetingand Meeting May 9 th 2011

2 Challenging Environment Assessment Laboratory g

3 CEAL Motion Simulator

4 CEAL Motion Simulator

5 StreetLab

6 StairsLab

7 WinterLab

8 Slips and Falls 25 Non-fatal pedestrian injury rates by month Västmanland, Sweden, November 1989 to October 1990 (Adapted from Eilert- Petersson & Schelp, 1998) J F M A M J J A S O N D A systems perspective of slip and fall accidents on icy and snowy surfaces (Gao & Abeysekera, 2004) 8

9 Slip Resistance Coefficient of friction (COF) at the interface of the floor surface is the measure of slip resistance most commonly associated with slips and falls. i l i i d f ll Research on Slip Resistance Measurements A New Challenge (Kim & Nagata, 2008) As the difference between available co efficient of friction and required coefficient of friction increases, the number of slips and falls on level surfaces and on ramps increases. Predicting slips and falls considering required and available friction (Hanson, 1999) There is still no reliable method for measuring slip resistance on still reliable measuring slip resistance on contaminated surfaces. Slip resistance of the shoe floor interface under biomechanically relevant conditions (Redfern & Bidanda, 1994) 9

10 Slip Resistance In dragging friction and simulated heel strike tests on ice sharp hard cleats provide greatest friction. Slip resistance on icy surfaces of shoes, crampons and chains id fi i a new machine (Bruce et al., 1986), Slipperiness of footwear and mechanisms of walking friction on icy surfaces (Gronqvist & Hirvonen, 1995) SATRA test method is the current standard for testing slip resistant winter footwear Dry stainless steel Wet stainless steel Dry quarry tile Wet quarry tile SATRAslip SATRA slip resistance test apparatus test apparatus 10

11 Objective To determine how anti slip footwear available on the market perform while walking on level surfaces H 1 : Anti slip soles alter the timing and magnitude of frictional utilization on various walkway surfaces; H 2 : Frictional utilization on standard test surfaces are not the same as that on icy surfaces 11

12 Experimental Setup p 0.84 m 0.76 m 0.44 m 076m 0.76 m 0.84 m Force Plate Force Plate 12

13 Test Conditions & Footwear Surfaces: 1) Concrete: 3 C 2) Steel: 3 C 3) Wet Steel: Steel 3 3 C 4) Ice: 5 C overnight, 3 C for 2h 5) Wet Ice: 5 C overnight, 3 C for 2h Footwear: 1) Walking Boot A 2) Walking Boot B 3) Work Boot A 4) Work Boot B 13

14 Ground Reaction Forces Vertical Force (F V ) Horizontal Force (F H ) 1200 Concrete 1200 Concrete ce (N) Forc ce (N) Forc Time (s) Time (s) 1200 Ice 1200 Ice ) Force (N ) Force (N Time (s) Time (s) Step 1 Step 2 14

15 Utilized Friction COF U F F H V COFu Concrete & Work Boot A 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % of Step Subject 1 Trial 1 Subject 1 Trial 2 Subject1 Subject 1 Trial 3 Subject 2 Trial 1 Subject 2 Trial 2 Subject 2 Trial 3 Subject 3 Trial 1 Subject 3 Trial 2 Subject 3 Trial 3 t3 Til3 COFu Wet Ice & Walking Boot A % 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % of Step Subject 1 Trial 1 Subject 1 Trial 2 Subject 1 Trial 3 Subject 2 Trial 1 Subject 2 Trial 2 Subject 2 Trial 3 Subject 3 Trial 1 Subject 3 Trial 2 Subject 3 Trial 3 15

16 Available Friction Measured using a Neolite pad with an English XL Variable Incidence Tribometer (ASTM F1679) English XL on ice Concrete (no sand, Concrete (with sand, Steel (3 o C) Wet Steel (3 o C) Ice (0 o C) Ice (3 o C) Wet Ice (3 o C) 3 o C) 3 o C) COF A (y) 1 > COF A (x) > Direction of travel and direction concrete was brushed in 16

17 Available Friction 17

18 Slip Resistance Decreasing Slip Resistance Concrete Steel Wet Steel Ice Wet Ice Decrea asing Slip R Resistance Work Boot A Work Boot B Walking Boot BB Walking Boot A 0.08 (3, 1) 0.07 (1, 1) 0.09 (2, 1) 0.08 (5, 2) 0.14 (5, 2) 0.10 (14, 2) 0.12 (12, 3) 0.08 (57, 3) 18

19 Frictional Utilization COF Ice & Walking Boot B % of Step COF Wet Ice & Walking Boot B % of Step COF Ice & Walking Boot A % of Step COF Wet Ice & Walking Boot A Walking % of Step Utilized COF Available COF 19

20 Next Steps Can we use maximum negotiable up slopes and down slopes to assess footwear slip resistance?

21 Next Steps How can we optimize the placement and design of anti slip mechanisms to prevent slips, trips, and falls?

22 Acknowledgements