Statement from the expanded commentary means that the seismic part of the earth pressure needs to be considered only in those load combinations that includeĮ, but the load factor for strength design should be 1.4 and for ASD Pressures, on the other hand, are typically computed at ASD level. Static lateral earth pressure is considered to be an H load.Į in ASCE 7 is determined at strength level, and consequently has a loadįactor of 1.0 on it in the strength design load combinations and 0.7 in the ASD load Lateral earth pressure during ground shaking. Thisĭynamic earth pressure is superimposed on the preexisting static Walls during earthquake ground shaking is considered to be anĮarthquake load, E, for use in design load combinations. The dynamic lateral earth pressure on basement and retaining Q: For the purpose of the load combination equations, is the seismic lateral earth pressure considered a load due to lateral earth pressure,Įxpanded seismic commentary to ASCE 7-10 says theĮvaluation of Dynamic Seismic Lateral Earth Pressures. The same logic can be extended to retaining walls as well. Item 9 under ASCE 7-10 Section 12.3.4.1 (Conditions Where Value of ρ is 1.0) includes “Design of structural walls for out-of-plane forces, including their anchorage.” Opinion that the Redundancy Factor, ρ, should be 1.0 for basement walls and retaining walls, because the idea of redundancy does not really apply to wallsĭesigned for out-of-plane forces. A displacement at the top of the wall of 0.002 times the wall height is typically sufficient to develop the minimum active pressure state.” The amount of movement to develop minimum active pressure is very small. The term “Yielding Wall” only means that the walls “can move sufficiently to develop minimum active earth pressures.” The paper goes on to say: “Note that in this context, yielding refers to permanent displacement of the wall as a result of the seismic event and does not mean that stresses within the structural system were exceeded. Resource paper cited above (as well as ASCE 7-10 Section 15.6.1) talks about “Yielding Walls,” the walls are not actually yielding in the structural sense. In the case of lateral earth pressure, even though the The R-factor is used to account forĮnergy dissipation and inelastic deformation capacity of a structure. The same as that used for the building itself.ħ do not specifically address the application of the Response Modificationįactor, R, for basement walls or retaining walls. Wall is part of a building, and consequently, its I e should be How to determine Risk Category of a retaining wall for this purpose. The factor ( I e/ R), like we do when determining seismic base shear forĪ building? What about the Redundancy Factor, ρ?Įarthquake loads on retaining walls should be multiplied by the Importance Factor, I e per ASCE 7-10 Section 15.4.1.1, which requires that the importance factor be at least equal to that determined from ASCE 7-10 Table 1.5-2.ĪSCE 7-10 Section 15.6.1, Earth Retaining Structures, includes requirements on Q: Should we multiply the forces from seismic lateral earth pressure values by LRFD) should be verified with the registered design professional providing the Level, just like the static active pressure values. Seismic lateral pressures and loads are most commonly calculated at ASD Q: Okay, so the resource paper you mentioned above provides guidelines andĮquations for determining seismic lateral earth pressures. Lateral Earth Pressures." All three parts of the 2009 NEHRP Provisions For the registered design professional, discussion and guidance regarding different approaches for determining seismic lateral pressuresĬan be found in Part 3 of the 2009 NEHRP Provisions in Resource Paperġ2, titled " Evaluation of Geologic Hazards and Determination of Seismic Pressure be provided by the registered design professional preparing the 2012 IBC Section 1803.5.12, inĬonjunction with Section 1803.1, requires that dynamic seismic lateral earth Lateral earth pressures due to seismicity. How do we determine the dynamic seismic lateral earthĬorrect that ASCE 7-10 and the 2012 IBC do not specify any methods for calculating increase in However, those documents do not specify the methods forĬalculating these pressures. Pressures on basement and retaining walls of structures assigned to Seismic Design Category (SDC) D, E, or F due to design earthquake ground motions. IBC Section 1803.5.12 require inclusion of dynamic seismic lateral earth
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