LRFD Article 3: LRFD for Substructures – Calibration of Resistance Factors for Pullout in MSE Walls Based on Fitting With ASD

Document Info

Title: LRFD Article 3: LRFD for Substructures – Calibration of Resistance Factors for Pullout in MSE Walls Based on Fitting With ASD

Authored By: Naresh C. Samtani, PhD, PE, BC.GE, F.ASCE

Report Date: April 2011

Sponsoring Agency: NCS GeoResources, LLC

Abstract

Mechanically Stabilized Earth (MSE) walls are one of the most common types of fill walls. The design of MSE walls includes an evaluation of the external and internal stability. Internal stability evaluation addresses two primary modes of failure of the soil reinforcements, (1) pullout and (2) tension breakage. In accordance with the framework of the Load and Resistance Factor Design (LRFD) approach as presented by American Association of State Highway and Transportation Officials (AASHTO, 2008), each of these failure modes must be assigned a different resistance factor. The resistance factors for the tension breakage failure mode are related to the structural characteristics of the soil reinforcement and are clear. However, there is confusion regarding the resistance factors for the pullout failure mode particularly when there are surcharges above or within the reinforced soil zone. This article discusses calibration of the resistance factors for pullout based on fitting with the Allowable Stress Design (ASD) approach (AASHTO, 2002) using the AASHTO-LRFD framework (AASHTO, 2008).