All ETDs from UAB

Advisory Committee Chair

Fouad H Fouad

Advisory Committee Members

Bo Dowswell

Robert W Peters

Christopher J Waldron

Ashraf Al-Hamdan

Document Type

Dissertation

Date of Award

2019

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

Fillet weld connections are very common in steel structures because they are easier and cheaper than other types of welded connections, such as groove welds. Several studies were performed on fillet weld of right dihedral angle, such as T-joints weld, to specify its capacity and failure mechanisms under different load directions. Nevertheless, the fillet weld strength analysis is based solely on the shear strength of the weld. Additionally, many of the current details commonly used for T-Joints were based on the requirements for groove welds. Fillet weld design concepts for skewed T-joints in the AWS D1.1 and AISC specifications are the same as the fillet weld of right T-Joints. Except for the weld throat dimension. Incomplete fusion may occur in fillet weld in acute angles. Also, the root opening requirement of being less than or equal to 3/16 in. is based on the fabrication tolerances in AWS D1.1. The main objective of this research was determining the capacity of fillet weld in skewed joints and developing practical design methods. Secondary objectives were determining the impact of changing weld’s dihedral angle, size, and loading direction on skewed weld strength and determining the total weld strength of the skewed joint. The study includes theoretical (mathematical models), analytical (finite element analysis modeling) and experimental investigations. The analytical model was validated and calibrated by the testing results. Thirty five Specimens were prepared for the experimental study. Different mathematical models were proposed and compared with the results of finite element analysis and testing to determine an accurate mathematical representation of skewed welds. Flux-cored arc welding process was used for the tested specimens. The base metal was A572 Grade 50 steel and the weld metal was 70 ksi strength electrode. The tensile mechanical properties of the weld metal were determined from ancillary tests. The welded skewed joints were fabricated with different changing parameters: the dihedral angle, weld size, and loading direction. The load-deformation curve and strength of the welds in skewed joints were recorded from testing. The curves were used in strain compatibility application of fillet welds on both sides of skewed T-Joints to determine if the individual strength of each side can be added to obtain the total strength of the joint. Practical design procedures for skewed weld that are guided by the AISC Steel Construction Manual were proposed and compared with current procedures. Design examples are provided to show the effect of the skewed weld angle on the design of fillet welds. Prequalified status for skewed T-joints was established. Additionally, symbol for skewed T-joints fillet weld were proposed to avoid the confusion with PJP weld symbol.

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Engineering Commons

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