Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 25
25 Table 15. Pendulum testing summary for vertical tears. Time of Impact Maximum Damage Test # End Max Crash Speed Deflection* Mode Fixture Deflection Performance (km/hr) (mm) (ms) 01-2 3-Cable 32.7 767 136 Containment Undamaged 03-2 2-Cable 30.9 739 140 Containment 07-1 2-Cable 28.3 610 140 Containment Penetration, 01-3 3-Cable 32.0 592* 84 Vertical Tear Tear at center (4 in.) Penetration, 03-5 2-Cable 32.8 533* 90 Tear at center Vertical Tear Containment, 08-2 2-Cable 32.9 711 144 (0.5 inch) Tear at center w-beam section. For the 4-inch tear, the width of the tear was Again, the post-rail connection at the splice remained intact 0.5 inches at the w-beam edge and tapered to a point. For the while the post-rail bolt pulled through the rail at the non- 0.5-in (13 mm) tear, the width of the tear was approximately splice location. 4 mm (0.15 inches). For the 0.5-inches (13 mm) vertical tear damage in Test 08-2, the barrier was able to contain the pendulum mass with a maximum deflection of 711 mm (28 inches). A vertical tear 4.3 Results developed from the bottom tip of the induced vertical tear, In Test 03-5, the barrier section with a 4-inch (102 mm) ver- at 13 mm from the w-beam edge, and continued (roughly tical tear was unable to contain the pendulum mass impact- straight downward) through approximately half of the w-beam ing at 20.4 mph (32.8 km/hr) (see Table 15). Impact speed cross section. The overall damage and close-up views of the was computed by analysis of the high-speed overhead video tear propagation are shown in Figure 18. footage. A vertical tear developed from the bottom tip of the induced vertical tear and continued (approximately straight 4.4 Recommendation downward) through the entire w-beam cross section result- ing in a complete transection of the w-beam at the impact Pendulum testing of a strong-post w-beam barrier with a location. Based on an analysis of the overhead high-speed vertical (transverse) tear resulted in complete rail rupture. video data, the deflection of the rail was 533 mm (21 inches) This was due both to the loss in an available cross section to at 90 ms after initial impact, which was just prior to penetra- carry the tensile load as well as the introduction of a stress tion of the w-beam section. At 118 ms after initial impact, the concentrator. Although the vertical tear in the pendulum test w-beam was completely transected. The overall damage and was relatively severe (roughly one-fourth of the w-beam cross the post damage due to impact are shown in Figure 16. Other section), the research team believes that any vertical tear rep- than at the damage location, there were no other tears evident resents a stress concentrator sufficient to cause further tear- in the w-beam. ing should the barrier be subjected to a secondary impact. A The right portion of Figure 17 shows time sequence snap- second pendulum test was conducted for a small vertical tear shots of Test 03-5 obtained from the high speed camera posi- of 13 mm (0.5 inches) in length. A pendulum impact at 20 mph tioned overhead. The performance of the analogous 3-cable caused this small tear to grow ominously to a length of 4 inches test (not shown), Test 01-3, was very similar with the pen- The research team concluded that no vertical tear is safe. To be dulum penetrating the barrier section due to a full cross- cautious, the research team has classified vertical rail tears of section tear at the impact location. Post damage and relative any length as a damage mode that should be repaired with movement of the w-beam sections at the splice was similar. high priority (Exhibit 1.0).
OCR for page 25
26 Undamaged Rail, Test 03-2 (30.9 km/hr) 4-inch Vertical Tear Damage, Test 03-5 (32.8 km/hr) 0.02 s 0.06 s 0.03 s 0.06 s 0.10 s 0.14 s 0.09 s 0.12 s 0.18 S 0.22 s 0.15 s 0.18 s 0.26 S 0.30 s 0.21 s 0.24 s Figure 17. Sequential overhead photographs for undamaged section (left) and 4-inch vertical tear damage (right). Figure 18. Test 08-2: overall damage (left) and detail views of the additional tearing caused by the pendulum impact (center), and post damage at splice location (right).
OCR for page 25
27 Exhibit 1.0. Recommendations for vertical tear damage repair. Damage Repair Threshold Relative Mode Priority Horizontal Horizontal (longitudinal) tears greater than 12 in. long or greater Medium tears than 0.5 in. wide should be repaired with a medium priority. Note: for horizontal tears less than 12 in. in length or less than 0.5 in. in height, use the non-manufactured holes guidelines.