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Title: Column face bending of anchored blind bolted connections to concrete filled tubular sections
Author: Mahmood, Mohammed Shihab
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2015
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The closed form profile of the hollow sections makes it difficult to perform connections without welding. The so-called blind bolting techniques were introduced as practical alternatives to welding for connections to hollow sections. However, the majority of blind bolting systems are restricted to be used as simple connections due to their limited stiffness. Extended HolloBolt (EHB) is a promising anchored blind bolting system for concrete filled Structural Hollow Sections (SHS). It was developed at the University of Nottingham as a modified version for the Lindapter HolloBolt. Its ability for providing rigid or semi-rigid connection was assessed successfully. The tensile performance of the EHB was investigated and it showed similar behaviour to the standard bolts in terms of strength and failure mode. Bending of the column face component is one of the failure modes for EHB connections. However, there is insufficient data to estimate the strength and stiffness of this component. Therefore, this research is aimed at investigating the column face bending performance in EHB connections and devise analytical models for its strength and stiffness. These models can then be used under the component method for the design of the EHB connections. A comprehensive experimental programme was performed to examine the effect of varying the influential parameters on the component behaviour by testing 35 specimens. The tests involved applying monotonic pull-out load on the EHBs. Specimens with single row of two EHBs were tested to investigate the effect of concrete grade, column face slenderness ratio, bolt gauge distance, anchored length and concrete type. Specimens with double rows of EHBs (two in each row) were tested to investigate the effect of bolt pitch distance. The bending strength and stiffness of the column face component and the strain distribution at the hollow section were used to evaluate the effect of each parameter. The anchored behaviour was assessed by examining the concrete around the bolts at different stages of loading. ABAQUS 6.13 package was employed to develop 3D finite element models for the investigated specimens . The models were validated against the experimental results and they showed good agreement. Then they were used to conduct parametric study within the range of the validity of the model. Analytical models were devised to estimate the column face bending strength and stiffness. The component strength is assumed to be provided by the SHS plate bending and the anchored action. The SHS plate strength models were developed based on the yield line theory. The anchored strength was considered equivalent to the load required to initiate a concrete cone failure. The component stiffness models were formulated using elastic springs, one at each bolt location. The component stiffness was taken equal to the summation of the four springs stiffness as they act in parallel. The analytical models were validated with experimental and finite element data and they provided reliable results, which can be considered as a benchmark for the design of EHB connections. The study quantified the effect of each of the influential parameters on the component performance. The overall bending behaviour of the component was represented by quad-linear model. The stiffness of post yield parts of the model were considered as a percentage of the initial stiffness of the component. The main contribution of this work is the proposed strength and stiffness component models for column face bending for concrete filled SHS, that can be used for the design of connections made with extended and anchored HolloBolts. These models maybe later extended and generalized for other similar blind bolts connections.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available