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OCR for page 84
84 CHAPTER 16 A Field Guide for the Restoration of Longitudinal Barriers This document presents guidelines for the level of damage Table 35. Repair priority scheme. to longitudinal barriers that requires repair in order to restore Priority Description a barrier to operational performance. The guidelines are pre- Level sented in a format designed for use in the field by highway High A second impact results in unacceptable safety maintenance personnel. Included are guidelines for repair of performance including barrier penetration and/or vehicle rollover. w-beam, generic end-terminals, and guidance for repair of Medium A second impact results in degraded but not more severe barrier damage. The relative priority for repair is unacceptable safety performance. Low A second impact results in no discernible presented for each damage mode as described in Table 35. difference in performance from an undamaged The following guidelines in Tables 36 and 37 are based on barrier. the performance of a damaged barrier if a second collision should occur. The second collision is assumed to occur at ously damaged barrier. The probability of a second impact typical highway speeds of 100 km/hr (62.1 miles/hour) at an will depend on many factors, e.g., traffic volume, and is be- angle of 25 degrees. The guidelines are based upon the out- yond the scope of this document. The probability of a second come of a second impact--should it occur. The guidelines are impact should be another factor that is considered when de- not based upon the probability of a second impact to a previ- termining the repair priority of a damaged barrier section.

OCR for page 84
85 Table 36. Summary of W-beam barrier repair thresholds. Damage Mode Repair Threshold Relative Priority Measurement Post and Rail One or more of the High Deflection following thresholds: More than 9 in. of Maximum Lateral lateral deflection Rail Deflection anywhere over a 25-ft length of rail Damage Length, LD Top of rail height 2 or more inches lower than original top of rail height 6-9 in. lateral deflection Medium anywhere over a 25-ft length of rail Less than 6 in. of lateral Low deflection over a 25-ft length of rail (Weak Post W-Beam Shown Only for Clarity. Each measurement taken at the rail's middle fold) Rail Deflection 6-9 in. of lateral deflection Medium Only between any two adjacent Maximum Lateral Rail posts Deflection Note: For deflection over 9 in., use post/rail deflection guidelines. Less than 6 in. of lateral Low Damage Length, L deflection between any two adjacent posts Rail Flattening One or more of the Medium following thresholds: Rail cross-section height is more than 17 in. (such as may occur if the rail is flattened) Rail cross-section height is less than 9 in. (such as a dent to the top edge) Rail cross-section height is Low between 9 and 17 in. Posts Separated 2 or more posts with Medium from Rail blockout attached with a post/rail separation less Detached than 3 in. Posts 1 or more posts with a post/rail separation which exceeds 3 in. 1 post with blockout Low attached with post/rail Note: separation less than 3 in. 1. If the blockout is not firmly attached to the post, use the missing blockout guidelines. 2. Damage should also be evaluated against post/rail deflection guidelines. (continued on next page)

OCR for page 84
86 Table 36. (Continued). Damage Mode Repair Threshold Relative Priority Measurement Missing/Broken 1 or more posts High Posts Missing Missing Post Cracked across the grain Broken Rotted With metal tears Missing Blockout Any blockouts Medium Missing Missing Blockout Cracked across the grain Cracked from top or bottom of blockout through post bolt hole Rotted Twisted Blockouts Any misaligned blockouts Low and the top edge of the block is 6 in. or more from the bottom edge Note: Repairs of twisted blockout are relatively quick and inexpensive. Non-Manufactured More than 2 holes with High holes a height less than 1 in. on a 12.5-ft length of rail (such as crash- induced holes , Any holes with a lug-nut damage, height greater than 1 in. or holes rusted- through the rail) Any hole which intersects either the top Height of or bottom edge of the non-manufactured hole rail 1-2 holes with a height less Medium than 1in. on a 12.5-ft. length of rail Damage at a rail More than 1 splice bolt High splice Missing Damaged Visibly missing any underlying rail Torn through rail 1 splice bolt Medium Missing Damaged Visibly missing any underlying rail Torn through rail

OCR for page 84
87 Table 36. (Continued). Damage Mode Repair Threshold Relative Priority Measurement Vertical Tear Any length vertical High (transverse) tear Horizontal Tear Horizontal (longitudinal) Medium tears greater than 12 in. long or greater than 0.5 in. wide Note: for horizontal tears less than 12 in. in length or less than 0.5 in. in height, use the non-manufactured holes guidelines.

OCR for page 84
88 Table 37. Summary of generic end terminal repair thresholds. Damage Mode Repair Threshold Relative Priority Measurement Damaged End Post Not functional (sheared, High rotted, cracked across the grain) Anchor Cable Missing High Missing Anchor Cable Anchor Cable More than 1 in. of Medium movement when pushed down by hand 1" Cable Anchor Loose or not firmly seated Medium Bracket in rail Cable Anchor Bracket Stub Height Height which exceeds 4 in. Medium

OCR for page 84
89 Table 37. (Continued). Damage Mode Repair Threshold Relative Priority Measurement Lag Screws Missing or failed lag High (Energy Absorbing screws Terminals Only) Bearing Plate Loose or misaligned Medium (Correct Bearing Plate) (Misaligned Bearing Plate) Missing bearing plate High (Missing Bearing Plate) Note: Any damage extent below the threshold is assumed to be low priority.