Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
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Soldier Rev B
| 8.4 DESIGN FOR ICE AND COLLISIONS Bridges and other structures may need to be designed to withstand the force effects of ice and collision of vehicles or vessels (ships or barges. These are addressed under Extreme Event II conditions in AASHTO (2014) and are treated as independent events, although they maybe treated in tandem with other loading conditions, such as wind or water loads. These loads are typically applied to the structure, either the superstructure, columns/piers, or the pile/shaft cap. Unlike the scour and earthquake extreme event cases, these cases do not result in changes to the geotechnical conditions or resistance. Structural analyses are performed to resolve these loads into force effects at the top of the deep foundation elements for analysis of the individual foundation elements and foundation group. A detailed discussion of such structural analyses is beyond the scope of this manual but can be found in AASHTO (2014). Once the force effects are determined at the top of the foundation element, lateral load analysis is performed as discussed in Chapters 6 and 7 for individual foundation elements and groups. Within the LRFD design framework, the equation for the Extreme Event Limit State II is as follows οΏ½ πΎπΎ ππ ππ ππ = πΎπΎ ππ π·π·πΏπΏ + 0.5πΏπΏπΏπΏ + 1.0πππ΄π΄ + 1.0πΉπΉπΉπΉ + 1.0(πΌπΌπΆπΆ ππππ πΆπΆππ ππππ πΆπΆππ) Equation 8-6) Where Ξ³ I = Load factor. Q i = Force effect. Ξ³ p = Load factor for permanent loads (from Chapter 4). DL = Dead load. LL = Live load. WA = Water load. FR = Friction load. IC= Ice load. CT = Vehicular collision load. CV = Vessel collision load. The last term in the equation indicates that the loads from ice, vehicular collision, and vessel collision are treated as separate extreme events and not combined. However, the equation indicates that these extreme events are considered in conjunction with other loads, such as dead loads, live loads, water loads, and friction loads. 122 The resistance factor for lateral load resistance under extreme loads is 1.0, unless site or project specific considerations apply as discussed in Chapter 4. Download 6.03 Mb. Share with your friends:
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