All ETDs from UAB

Advisory Committee Chair

Ian E Hosch

Advisory Committee Members

Fouad H Fouad

Robert W Peters

Christopher J Waldron

Hongyu Zhou

Document Type

Dissertation

Date of Award

2016

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

The clearance distance (a.k.a. stand-off distance) of the anchor bolt for double-nut moment joints is the distance between the bottom of the leveling nut and the top of concrete foundation. Previous research has investigated the effect of different loading conditions on the behavior of anchor bolts that have uniform stand-off distances. However, there currently are no studies in the technical literature that have investigated the behavior of anchor bolts with uneven stand-off distances. In the past, uneven stand-off distances have resulted from topographical limitations and leveling practices during construction. The anchor bolt stand-off distance discrepancy imposes an irregular stress distribution within the anchor group which is severe for anchor bolts with the largest stand-off distances. The main objective of this research is to investigate the effect of uneven stand-off distances on the stress distribution of the anchor bolts within the double-nut moment joint connection. An analytical approach was developed to analyze the behavior of anchor bolts with stand-off distances subjected to torsion, direct shear, and moment that transferred from the acting static loading on the superstructure. This method is applicable for those connections having uniform, uneven, excessive, and non-excessive stand-off distances. The approach is based on the load distribution method used in the analysis of shear walls subjected to wind and seismic loading. The analytical method was validated using the experimental data provided by ALDOT/UAB Project #930-680. A finite element analysis (FEA) was conducted using the SAP2000 software. Four factors were investigated: number of anchors, diameter, minimum stand-off distance, and surface angle. A percentage below 2% was found when comparing the forces determined by the FEA model and those computed using the analytical approach. The analysis has revealed that the forces are distributed on the anchors based on the stiffness of the individual anchor bolt and the proximity of the anchor to the center of the rigidity. The research provided a comparative design methodology using the analytical approach and AASHTO (2013) for uneven anchors. AASHTO exhibited a 41.9% increase in normal stress and a 34.1% reduction in shear stress when comparing with the analytical stresses.

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