Guidelines for Shielding Bridge Piers (2018) / Chapter Skim
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From page 68... ...
68 Verification and Validation This chapter presents four examples that illustrate the use of the proposed LRFD bridge design procedures and RDG procedures for shielding bridge piers. Please reference Appendix A: Proposed LRFD Bridge Design Pier Protection Specifications and Appendix B: Proposed RDG Occupant Protection Guidelines for the proposed procedures.
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From page 69... ...
69 from the edge of travel as noted by the solid-white edge line (SWEL) of the primary lane.
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70 in Appendix F: Heavy-Vehicle Traffic Mix and Properties. Knowing that the functional classification is a rural collector, the user goes to the upper right section of Table 7 and selects the value corresponding to a 45-mph PSL and a critical pier component lateral resistance of 250 kips to find the value of 0.3710 (see Table 44)
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From page 71... ...
71 5.1.3.3 Probability of a Collision with an Unshielded Pier Component Given a Passenger Vehicle Encroachment: P(C|PVEi) The probability that an encroaching passenger vehicle will strike the pier system is a function of the offset of the pier component at the leading edge of each direction and the size of the bridge pier.
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From page 72... ...
72 pier component is 10 ft from the edge of the lane, and a w-beam guardrail is a little less than 2 ft wide depending on the particular design. RDG Table 5-6 shows that in both finite element simulations and crash tests, MASH TL-3 strongpost w-beam guardrails [i.e., the Midwest Guardrail System (MGS)
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Figure 37. Occupant protection shielding barrier for Example #1.
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74 RSAPv3 indicates a total of 0.0020 heavy-vehicle collisions per year with this three-column pier, which is 0.0007 heavyvehicle collisions more than predicted by the LRFD procedure for direct impacts with Column #1 from Direction #1 or Column #3 from Direction #2. As discussed in the previous paragraph, however, column failure is almost exclusively associated with impact with the leading column.
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From page 75... ...
75 Notes: COL = column, SYEL = solid-yellow edge line, BWLL = broken white lane line. Figure 38.
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76 the offset of the pier component at the leading edge of each direction and the size of the bridge pier component, as listed in Table 19 (i.e., Appendix A, Table C3.6.5.1-3)
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77 Table 57. Passenger vehicle base encroachment frequency for Example #2.
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78 for occupant protection even though shielding is not required to protect the bridge from collapse. 5.2.4 Shielding Barrier Layout Shielding is only required for vehicle occupant protection in Example #2, so a MASH TL-3 strong-post w-beam guardrail will be used.
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Figure 39. Occupant protection shielding barrier for Example #2.
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80 in the primary direction. The four pier columns are placed in the median tangent to the traveled way but 25 ft from the primary left edge and 20 ft from the opposing left edge.
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81 in Table 64 can be used in conjunction with Table 15 (i.e., Appendix A, Table C3.6.5.1-1) to calculate the sitespecific adjustment, as illustrated in Table 65.
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From page 82... ...
82 departures from Direction #2 since it is at the leading edge from that direction. The offset for Direction #2 is the 20-ft offset from the SYEL to the face of Column #4.
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83 probability of a failure-inducing truck collision was sufficiently high. There is, therefore, no need to check the RDG occupant protection procedure because a MASH TL-5 concrete barrier is already needed to shield the pier system from heavy-vehicle impacts.
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Figure 41. Pier protection shielding barrier for Example #3.
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85 calculations, so the risk assessment model is used to determine if the pier system should be shielded to minimize the risk of bridge failure due to a pier collision. Both columns are small, 2-ft-diameter circular columns, and the designer has determined that the lateral capacity of each is only 250 kips.
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86 divided highway so the user enters the divided highway portion of Table 13 with an AADT of 60,000 vehicles/day and 25% trucks to find that 0.0078 heavy-vehicle encroachments can be expected annually, as shown for reference in Table 75. 5.4.2.3 Probability of a Collision with an Unshielded Pier Component Given a Heavy-Vehicle Encroachment: P(C|HVEi)
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87 section of Table 7 (i.e., Appendix A, Table C3.6.5.1-4)
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From page 88... ...
88 3.25 ft of space from the back of the barrier to the face of the pier. A typical single-faced section of rigid concrete barrier is about 18 in.
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From page 89... ...
89 Parameter LRFD Procedure Direction RSAPv3 Direction #1 #2 #1 #2 Site-specific adjustment factor (Ni) 2.29 1.82 2.30 1.82 Base vehicle encroachment (ENCR)
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