Hysteretic response of an innovative blind bolted endplate connection to concrete filled tubular ...

352 Pages·2017·38.48 MB·English

by  Christine Middleton

The University of
Nottingham
Department of Civil Engineering
Hysteretic response of an innovative blind
bolted endplate connection to concrete
filled tubular columns
by
ZHIYUWANG
Thesis submitted to the University of Nottingham for
the degree of Doctor of Philosophy
January 2012
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ABSTRACT
Concrete filled steel tubular (CFT) columns can employ the advantages of
both materials: steel and concrete. Connection to such columns, however, is
problematic. This isespecially so ifthe required connection is both bolted and
moment-resisting.
To address this issue, a novel blind-bolted and moment-resisting connection to
CFT column has been developed. This connection uses an innovative blind-
bolt, introduced in previous research at the University of Nottingham and is
termed the Extended Hollobolt (EHB). The EHB has been developed to
provide sufficient tensile resistance and stiffness for the connection to develop
resistance to moment. Previous research work has studied the performance of
this connection under monotonic loading. The performance of such connection
under cyclic loading, however, is not yet investigated. The work presented in
this thesis addresses this gap inknowledge.
This thesis reports on a series of full scale testing ofjoints consisting of beam
endplates connected to CFT columns using this blind bolt. The test
connections were constructed with relatively thick endplate so as to isolate the
CFT column and the blind bolt as the relatively weak elements in the
connection system. This study focuses on the behaviour of the connections
, with principal failure modes attributed bythe blind bolt and the CFT column.
The experiments were conducted to obtain insights into the hysteretic
moment-rotation relationship, available ductility & energy dissipation capacity,
observe typical failure modes, and develop relevant understandings of the
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Extended Hollobolt-endplate connection subjected to cyclic loading. The
selected connection details were chosen to examine the influential parameters
ofthejoint hysteretic moment-rotation behaviour.
From the experimental results, two representative failure modes, bolt fracture
and column face bending failure, were observed and categorized in relation to.
the connection configuration. The connection behaviour are described and
compared with respect to the influences of bolt grade.. cyclic loading
procedure, tube wall thickness and concrete grade.
Based on the experimental hysteretic moment-rotation relationships, an
evaluation of the cyclic characteristics and an analysis' of the cumulative
damage were carried out for the two representative connection categories. The
joint hysteretic moment-rotation response was assessed in term of
degradations of strength, stiffness, ductility, and energy dissipation. The use of
damage levels and stages in the interpretation of damage evolutions for the
connection behaviour is also described in this thesis. The findings of
cumulative damage analysis suggest that the energy based cumulative damage
index outweighs the other indices in characterizing the progressive damage
process of the connections in this study. This is especially the case for those
related to hysteresis loops at repeated cycles of each loading amplitude.
Following the experimental study. 3D nonlinear finite element models of the
connections were developed to analyse the mechanical response of the
connection. The comparison of the numerical and experimental moment-
rotation envelope curve is discussed with respect to related geometric and
material parameters. The connection failure modes and displacement :
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distributions were further examined as a supplement to the experimental
findings that were necessarily limited by instrumentations.
This work also presents mathematical models for the hysteretic moment-
rotation relationships simulating the loading, unloading and reloading
segments of the hysteresis loops. Characterizing parameters were introduced
to,allow for the softening slope, linear segment slope, and degradations of
.strength and energy dissipation.
This study concluded that the proposed finite element model simulates well
the beh~viour of the connection with good prediction of the moment-rotation
envelope curves and of the failure mode. It isalso concluded that the proposed
mathematical models define well the non-linear loading and unloading paths
with reasonable accuracy. It is finally claimed that the Extended-Hollobolt
endplate connection provides a stable improvement in strength and stiffness
under cyclic loading compared with other similar connections.
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LISTS OF CONTENTS
ABSTRACT ii
LISTS OF CONTENTS vi
LISTS OF TABLES xii
LISTS OF FIGURES : xiiii
NOTATIONS xx
ABBREVIATIONS ......................................................................•............... xxiii
TRADEMARKS xxii
ACKNOWLEDGEMENT ................................•......................................... xxiiii
DECLARATION xxivv
CHAPTER 1 1
1.1 BACKGROUND 1
1.2 JUSTIFICATION FOR THIS RESEARCH 5
1.3 RESEARCH QUESTIONS 9
1.4 RESEARCH AIM AND OBJECTIVES 10
1.5 RESEARCH METHODOLOGIES ; 10
1.6 OUTLINE OF CONTENTS 11
CHAPTER 2 15
2.1 INTRODUCTION 15
. 2.2 PREVIOUS STUDIES ON TENSILE BEHAVIOUR OF BLIND BOLTED
CONNECTIONS 15
2.3 PREVIOUS STUDIES ON MONOTONIC BEHAVIOUR OF BLIND BOLTED
BEAM TO COLUMN MOMENT CONNECTIONS 28
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2.4 PREVIOUS STUDIES ON CYCLIC BEHAVIOUR OF BOLTED ENDPLATE
BEAM TO COLUMN CONNECTIONS •••••••••••.•••••••••••••••.••••••••••••••••.••••••••••••.•••••••• 39
2.5 PREVIOUS NUMERICAL STUDIES OF BLIND BOLTED CONNECTIONS .... 55
2.6 PREVIOUS ANALYTICAL MODEL STUDIES OF BEAM- TO-COLUMN JOINTS
56
2.7 CONCLUSION AND NEEDS FOR FURTHER RESEARCH ••.•••••••••••••••••••••••58
CHAPTER 3 ~ 62
3.1 INTRODUCTION ••••••••••••••••••••••••••••••••••••••••••.••••••••••••••••••••••••••••••••••.••• 62
3.2 TESTING PROGRAM •••••••••.•••.•••.•.•••••••••...•••••••••••••••••••••.••••• :•••••••••••••••63
3.2.1 Connection details 63
3.2.2 Material properties 67
3.2.3 Fabrication a/test specimens 71
3.2.4 Testset-up ·· 73
3.2.5 Instrumentation :..; 79
3.2.6 Quasi-static cyclic loadingprocedure and control system 88
3.3 MEASUREMENT OF JOINT ROTATION AND MOMENT 91
3.3.1 Joint rotation measurement 91
3.3.2 Joint moment measurement 93
3.4 DETERMINATION OF YIELD POINT FROM FORCE-DISPLACEMENT
CURVES 96
3.5 CONCLUDING REMARKS 99
CHAPTER 4 100
4.1 INTRODUCTION : 100
4.2 FAILURE MODES 100
4.3 114
HYSTERETIC MOMENT-ROTATION RELATIONSHIPS
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