Archive for April, 2011

LRFD vs SLD for Micropiles Comparison

Load and Resistance Factor Design (LRFD) is the predominant design method utilized today for reinforced concrete and structural steel, and is the primary focus of the relatively new AASHTO LRFD Bridge Design Specifications. Historically, micropile design has been performed mainly with Service Load Design (SLD) and Allowable Stress Design (ASD) methodologies and most of the design manuals and specifications in existence prior to 2008 were based on SLD and ASD concepts. The AASHTO LRFD Bridge Design Specifications document offers the most comprehensive LRFD guidance for geotechnical engineering features in the United States (and maybe the World) today. The use of this LRFD design specification is mandated by the majority of State DOTs for use in designing highway bridges and highway structures governed by it. The AASHTO LRFD specification adopted a micropile design section in 2008.

In recent DFI / ADSC Micropile Seminars, there have been a number of questions regarding the proper use of LRFD for micropiles. On May 4, 2011, at the DFI / ADSC Micropile Seminar in Little Rock, AR, I will give a presentation that will cover the fundamentals of LRFD as it applies to micropiles, and will provide a comparison with SLD methodology. We will work through an example analysis problem where we will see how every aspect of micropile axial design compares between SLD and LRFD. We will be looking specifically at FHWA and IBC Service Load Design compared to AASHTO LRFD design. This covers pretty much all the current bases for mainstream micropile design. I have never seen this type of comparison presented so don’t miss out.

Register HERE. Hope to see you in Little Rock!