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84 This document presents guidelines for the level of damage to longitudinal barriers that requires repair in order to restore a barrier to operational performance. The guidelines are pre- sented in a format designed for use in the field by highway maintenance personnel. Included are guidelines for repair of w-beam, generic end-terminals, and guidance for repair of more severe barrier damage. The relative priority for repair is presented for each damage mode as described in Table 35. The following guidelines in Tables 36 and 37 are based on the performance of a damaged barrier if a second collision should occur. The second collision is assumed to occur at typical highway speeds of 100 km/hr (62.1 miles/hour) at an angle of 25 degrees. The guidelines are based upon the out- come of a second impactâshould it occur. The guidelines are not based upon the probability of a second impact to a previ- ously damaged barrier. The probability of a second impact will depend on many factors, e.g., traffic volume, and is be- yond the scope of this document. The probability of a second impact should be another factor that is considered when de- termining the repair priority of a damaged barrier section. C H A P T E R 1 6 A Field Guide for the Restoration of Longitudinal Barriers Table 35. Repair priority scheme. Priority Level Description High A second impact results in unacceptable safety performance including barrier penetration and/or vehicle rollover. Medium A second impact results in degraded but not unacceptable safety performance. Low A second impact results in no discernible difference in performance from an undamaged barrier.
85 Table 36. Summary of W-beam barrier repair thresholds. Damage Mode Repair Threshold Relative Priority Measurement One or more of the following thresholds: More than 9 in. of lateral deflection anywhere over a 25-ft length of rail Top of rail height 2 or more inches lower than original top of rail height High Post and Rail Deflection 6-9 in. lateral deflection anywhere over a 25-ft length of rail Medium Dama ge Le ng th , L D Maximum Lateral Ra il De fl ecti on Less than 6 in. of lateral deflection over a 25-ft length of rail Low 6-9 in. of lateral deflection between any two adjacent posts Note: For deflection over 9 in., use post/rail deflection guidelines. Medium Rail Deflection Only Less than 6 in. of lateral deflection between any two adjacent posts Low (W eak Post W-Beam Shown Only for Clarity. Each m easurement taken at the railâs middle fold) Ma xi mu m La te ra l Ra il Deflection Damage Length, L One or more of the 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) Medium Rail Flattening Rail cross-section height is between 9 and 17 in. Low Posts Separated from Rail 2 or more posts with blockout attached with a post/rail separation less than 3 in. 1 or more posts with a post/rail separation which exceeds 3 in. Medium 1 post with blockout attached with post/rail separation less than 3 in. Low Detache d Post s Note: 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)
86 Table 36. (Continued). Damage Mode Repair Threshold Relative Priority Measurement Missing/Broken Posts 1 or more posts Missing Cracked across the grain Broken Rotted With metal tears High Missing Post Missing Blockout Any blockouts Missing Cracked across the grain Cracked from top or bottom of blockout through post bolt hole Rotted Medium Twisted Blockouts Any misaligned blockouts 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. Low Missing Blockout More than 2 holes with a height less than 1 in. on a 12.5-ft length of rail Any holes with a height greater than 1 in. Any hole which intersects either the top or bottom edge of the rail , 1-2 holes with a height less than 1in. on a 12.5-ft. length of rail Non-Manufactured holes (such as crash- induced holes lug-nut damage, or holes rusted- through the rail) High Medium Height of non-manufactured hole More than 1 splice bolt Missing Damaged Visibly missing any underlying rail Torn through rail 1 splice bolt Missing Damaged Visibly missing any underlying rail Torn through rail Damage at a rail splice High Medium
87 Damage Mode Repair Threshold Relative Priority Measurement Vertical Tear Any length vertical (transverse) tear High Horizontal Tear Horizontal (longitudinal) 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. Medium Table 36. (Continued).
Damage Mode Repair Threshold Relative Priority Measurement Damaged End Post Not functional (sheared, rotted, cracked across the grain) High Anchor Cable Missing High Missing Anchor Cable Anchor Cable More than 1 in. of movement when pushed down by hand Medium Cable Anchor Bracket Loose or not firmly seated in rail Medium Cable Anchor Bracket 1â Stub Height Height which exceeds 4 in. Medium 88 Table 37. Summary of generic end terminal repair thresholds.
89 Damage Mode Repair Threshold Relative Priority Measurement Lag Screws (Energy Absorbing Terminals Only) Missing or failed lag screws High Loose or misaligned Medium Bearing Plate Missing bearing plate Note: Any damage extent below the threshold is assumed to be low priority. High (Missing Bearing Plate) (Correct Bearing Plate) (Misaligned Bearing Plate) Table 37. (Continued).
