ULTIMATE STRENGTH BEHAVIOR OF STEEL-
CONCRETE-STEEL SANDWICH COMPOSITE
BEAMS AND SHELLS

YAN JIABAO NATIONAL UNIVERSITY OF SINGAPORE
2012 ULTIMATE STRENGTH BEHAVIOR OF STEEL-
CONCRETE-STEEL SANDWICH COMPOSITE
BEAMS AND SHELLS

Acknowledgements

 I

ACKNOWLEDGEMENTS
Firstly, I would express my sincerest appreciation and gratitude to my supervisors, Prof.
Liew Jat Yuen, Richard and Prof. Choo Yoo Sang for their full support, supervision,
encouragements, constructive advices, generous guidance on my research work, paper
writing and presentation skills during the PhD study. I would also like to thank Prof.
Zhang Min-Hong, Prof. Marshall Peter William, and Assistant Prof. Qian Xudong for
their helpful suggestions and valuable discussions.
My sincere appreciation is dedicated to Dr. Kazi Md Abu Sohel, Dr. Chia Kok Seng, Dr.
Liu Xuemei, Dr. Lee Siew Chin, Mr. Xiong Dexin, Mr. Xiong Mingxiang, Mr. Li Ya and
Mr. Wang Tongyun for their continuous supports on research works and discussions.
My thanks also extend to all staff members at Concrete and Structural Engineering
Laboratory. Special thanks go to Mr. Koh Yian Kheng, Mr. Ang Beng Oon, Mr. Ishak
Bin A Rahman, Mr. Choo Peng Kin and Ms. Annie Tan for their generous, patient and
continuous help during the experiments.
I would thank all the friends and colleagues at my office during the year 2008 to 2012 and
friends at the Centre for Offshore Research & Engineering (CORE), NUS for every happy
moment we have shared during those years.
Finally, I would thank my wife (Ms. Chen Guiling), my parents, and my brother for their
moral supports, continuous love, understanding and encouragements. This thesis is
Acknowledgements

II 

dedicated to my family.
Table of Contents



strength)……… ……………………………………………………… 33 -
2.4.4 Strength of the SCS sandwich composite beams……………………… 39 -
2.4.5 Strength of SCS sandwich composite plates……………………………- 42 -
2.4.6 Punching shear strength of concrete shell………………………………- 49 -
2.4.7 Strength of SCS sandwich shell without shear connectors…………… 51 -
2.5 Finite element (FE) analysis on SCS sandwich structure…………………… 52 -
2.6 Summary of observations from the literature review…………………………- 53 -
CHAPTER 3 Novel shear connectors for SCS sandwich Composite structures
………………………………………………………………………………- 63 -
3.1 Introduction……………………………………………………………………- 63 -
3.2 Types of connectors………………………………………………………… 64 -
3.3 Prototype testing program…………………………………………………… 66 -
3.3.1 Specimens for the test…………………………………….………… 67 -
3.3.2 Material property……………………………………………………… 68 -
3.3.3 Test setup……………………………………………………………… 69 -
3.4 Test results…………………………………………………………………… 70 -
3.4.1 Failure modes and ultimate loads……………………………………… 70 -
3.4.2 Load-deflection behaviors………………………………………………- 71 -
3.5 Analysis and discussion of test results……………………………………… 72 -
3.5.1 Analysis on strength of SCS sandwich beams with UCU connectors… 73 -
3.5.2 Comparisons between UCU connectors and J-hook connectors……… 76 -
3.5.3 Comparison between J-hook connectors and headed shear studs………- 77 -
3.6 Summary………………………………………………………………………- 78 -
CHAPTER 4 Behaviour and strength of shear connectors in steel-concrete-steel
sandwich structures………………………………………………………………… 89 -
4.1 Introduction……………………………………………………………………- 89 -
4.2 Shear strength of J-hook connectors………………………………………… 91 -
4.2.1 Experimental program………………………………………………… 92 -
4.2.2 Test results………………………………………………………………- 96 -

5.2.2 SCS sandwich composite beams and test setup ……………………… 181 -
5.2.3 Strength of mechanical shear connector………………………………- 181 -
5.3 Analytical analysis on strength of SCS sandwich composite structure…… 182 -
5.3.1 Key concept……………………………………………………………- 182 -
5.3.2 Strength of mechanical connectors…………………………………… 183 -
5.3.3 Moment resistance of sandwich beam…………………………………- 185 -
5.3.4 Transverse shear resistance of sandwich beam……………………… 189 -
5.3.5 Deflection…………………………………………………………… 190 -
5.3.6 Strength of beam under combined bending moment and transverse shear
………… ………………………………………………………… 193 -
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5.4 Push out test and tensile test results…………………………………………- 193 -
5.4.1 Push out test results……………………………………………………- 193 -
5.4.2 Pull out test results…………………………………………………… 194 -
5.5 Beam test results and discussion…………………………………………… 195 -
5.5.1 Load deflection behavior………………………………………………- 195 -
5.5.2 Failure modes & maximum loads…………………………………… 195 -
5.5.3 Effect of shear span-to-beam thickness ratio………………………… 196 -
5.5.4 Effect of thickness of the steel face plate…………………………… 197 -
5.5.5 Effect of core material strength ……………………………………… 197 -
5.5.6 Effect of spacing of the shear connectors…………………………… 199 -
5.6 Finite element analysis on SCS sandwich composite beams with J-hook shear
connectors……………………………………………………………………- 199 -
5.6.1 General…………………………………………………………………- 199 -
5.6.2 Material model…………………………………………………………- 200 -
5.6.3 Element type and geometry of the model…………………………… 200 -
5.6.4 Contact and restraint conditions ……………………………………… 201 -

7.2 Applications and considerations…………………………………………… 298 -
7.3 Analysis on punching shear strength of SCS sandwich shell ……………… 302 -
7.3.1 Modified controlled perimeter for SCS sandwich composite shell……- 302 -
7.3.2 Punching shear strength of the core material………………………… 304 -
7.3.3 Punching shear strength of the steel face shell……………………… 306 -
7.4 Comparisons between the test results and predictions………………………- 307 -
7.5 Comparisons between the test results and the ice-pressure………………… 311 -
7.6 Design recommendations…………………………………………………… 311 -
7.6.1 Calculating punching shear strength of the SCS sandwich composite shell
(calculate the first peak strength of the structure)…………………… 311 -
7.6.2 Calculating punching shear strength of the surface skin steel shell (for
second peak strength of the structure)…………………………………- 312 -
7.6.3 Determine the ice-contact pressure from ISO 19906 and compare the
determined strength with the calculated punching shear resistance of the
shell…………………………………………………………………… 312 -
7.7 Summary…………………………………………………………………… 312 -
CHAPTER 8 Conclusions and recommendations……………………………… - 321 -
8.1 Review of completed research work…………………………………………- 321 -
8.2 Conclusions………………………………………………………………… 323 -
8.3 Recommendations for future works………………………………………… 328 -
References………………………………………………………………………… 331 -
Publications…………………………………………………………………………- 343 -
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VIII 
the J-hook connectors embedded in normal weight concrete (NWC), lightweight concrete
(LWC) and ULCC were widely investigated through 102 push-out tests and 79 tensile
tests. The push-out tests show the shear strength of the J-hook connectors are significantly
influenced by the geometry and strengths of the steel and concrete materials. Based on the
push-out test results, design formulae were developed to predict the shear strength and
describe the load-slip behaviors, respectively. Design approaches for tensile strength of
the J-hook connectors were also developed by modifying the ACI 318 and PCI codes.
Strength of the J-hook connectors under combined shear and tension loads were obtained
through FE analysis. All these developed design approaches offer the basic design guides
on the prediction of the SCS sandwich members.
Ultimate strength behavior of the SCS sandwich beams with shear connectors and ULCC
were evaluated through one- or two- point loading tests on 18 sandwich beams. Through
the experimental investigation, it reveals that shear span significantly influence the failure
modes and ultimate strength. Thickness of the steel plates, core material strength, and
spacing of the connectors influence the strength of the sandwich beams. Through the
comparisons between the strengths of the beams with the J-hook connectors and headed
shear studs, it revealed that the J-hook shear connectors provided equivalent ultimate
strength, ductility and stiffness to the beams with headed studs. Theoretical model was
developed to predict the strength of the SCS sandwich beams under combined shear force
and bending moment. The predicted strengths by this theoretical model agree well with
the test results. Moreover, nonlinear 3D FE model was developed for the analysis of the
sandwich beams with the J-hook connectors. The FE model exhibits good agreements on
the ultimate strength, deforming shape of the beams and cracks developed in the core
material. This offers a useful method for the analysis of the SCS sandwich beams.
Summary

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To date, there are no available design guides or tests on the SCS sandwich composite
shell structure with shear connectors. In this thesis, the ultimate strength performances of


LIST OF TABLES
Table 3.1 General comparisons among different connectors …………………… …- 80 -
Table 3.2 Details of the prototype beams…………………………………………… 81 -
Table 3.3 Results of prototype testing……………………………………………… 81 -

Table 4.1 Details of specimens in Batch A for push-out test ……………………… 106 -
Table 4.2 Details of specimens in Batch B for push-out test……………………… 107 -
Table 4.3a Concrete material properties of specimens in Batch A (At 28 day)…… 108 -
Table 4.4 Push-out test results and predictions by Eq. 4.2 of specimens in Batch A - 109 -
Table 4.5 Push-out test results and predictions by Eq. 4.2 of specimens in Batch B - 110 -
Table 4.6 Coefficients for proposed design formulae ……………………………… 111 -
Table 4.7 Material properties of the concrete mixture………………………………- 135 -
Table 4.8(a) Specimen for tensile test and results………………………………… 136 -
Table 4.8(b) Specimen for tensile test and results………………………………… 138 -
Table 4.9(a) Predictions by groups of equations method A~E…………………… 140 -
Table 4.9(b) Predictions by groups of equations method A~E…………………… 142 -
Table 4.10(a) Details of push-out test specimens………………………………… 167 -
Table 4.10(b) Details of push-out test specimens………………………………… 168 -
Table 4.11 Comparisons between FE predictions and test results………………… 169 -
Table 4.12 Detailed information and FE results of FE models…………………… 169 -

Table 5.1 Beam test specimen and specifications………………………………… 207 -
Table 5.2 Push out test specimens and specifications of J-hook connector…………- 208 -
Table 5.3 Details of the pull out test specimens…………………………………… 208 -
Table 5.4 Shear resistance of concrete………………………………………………- 208 -
Table 5.5 Shear resistance provide by steel connector………………………………- 209 -
Table 5.6 Push out test results and predictions………………………………………- 209 -
List of Tables



LIST OF FIGURES
Fig. 1.1 Ice-resisting wall for platforms in Arctic Ocean…………………………… 12 -
Fig. 1.2 Concept for fluted shell Arctic structure (Marshall, 2009)………………… 12 -
Fig. 1.3 Details of curved shell, radial bulkhead, and internal framing (Marshall,
2010)………………………………………………………………………………… 13 -
Fig. 1.4 Double skin structure (Wright and Oduyemi, 1991) ……………………… 13 -
Fig. 1.5 Illustrations on strengths of the SCS sandwich composite beam and shell
structure……………………………………………………………………………… 14 -

Fig. 2.1 Double skin SCS sandwich composite structure (Wright and Oduyemi,
1991) 55 -
Fig. 2.2 Illustration on linking the shear cracks of the overlapped shear studs………- 55 -
Fig. 2.3 Bi-steel structure…………………………………………………………… 55 -
Fig. 2.4 Different types of mechanical connectors (GARCÍA, 2004)……………… 56 -
Fig. 2.5 Test set-up of shells under concentrated loading (Birdy et al., 1985)……… 56 -
Fig. 2.6 Test set-up and dimensions of the specimens (Long, 1988; McLean et al.,
1990)………………………………………………………………………………… 57 -
Fig. 2.7 Test set-up of the SCS sandwich shells (Shukry, 1986)…………………… 57 -
Fig. 2.8 Failure modes of for anchors under tension force (a) Steel failure; (b) Pullout
failure; (c) Concrete breakout failure; (d) Side-face blowout ; (e) Concrete splitting (ACI
318-08, 2008) ……………………………………………………………………… 57 -
Fig. 2.9 Design philosophies on concrete breakout strength (Pallarés and Hajjar,
2010)………………………………………………………………………………… 58 -
Fig. 2.10 Strut and tie model for analysis of SCS sandwich beams (Xie et al., 2007) 58 -
Fig. 2.11 Stress block and the resultant force in the section ……………………… 58 -
Fig. 2.12 Dimension of the controlled perimeter…………………………………… 59 -
Fig. 2.13 Stress block and the resultant force in the section………………………… 59 -
List of Figures


Fig. 4.12 Effect of d on P
J
………………………………………………………… 116 -
Fig. 4.13 Effect of fck on P
J
(BA=Batch A; BB=Batch B)………………………… 116 -
Fig. 4.14 Predictions verified against the experimental ones ……………………… 117 -
Fig. 4.15 Scatter of ratios of test-to-prediction by different design equations………- 117 -
Fig. 4.16 Test and predicted load-slip curves (a) for NWC in Batch A; (b) for NWC in
Batch B; (c) for LWC in Batch A; (d) for LWC in Batch B; (e) for ULCC in Batch A; (f)
List of Figures

 XVII

for ULCC in Batch B. ……………………………………………………………… 118 -
Fig. 4.17 Failure modes of anchorage under tensile loading: (a)Steel failure; (b) pullout
concrete; (c) breakout; (d) side-face blowout; (e) concrete splitting (ACI 318,
2008)…………………………………………………………………………………- 144 -
Fig. 4.18 Methods of test on tensile strength of a pair of J-hook connectors……… 144 -
Fig. 4.19 Geometry illustration of the tensile-test specimens ……………………… 144 -
Fig. 4.20 Test set-up of the tensile test of J-hook connectors ……………………… 145 -
Fig. 4.21 Failure modes observed in tensile test of J-hook connectors…………… 146 -
Fig. 4.22 Effect of concrete strength on tensile strength of J-hook connector…… 147 -
Fig. 4.23 Effect of diameter of connector on tensile strength of connector…………- 147 -
Fig. 4.24 Effect of embedment depth on tensile strength of J-hook connector…… 148 -
Fig. 4.25 Effect of D/d ratio Fig. 4.26 Effect of fiber content……………………- 148 -
Fig. 4.27 Principles of calculating concrete breakout strength of the shear
connector…………………………………………………………………………… 148 -
Fig. 4.28 Calculation of projection area AN of the connector………………………- 152 -
Fig. 4.29 Frequency distribution of ratios of test results-to-prediction ratios by (a) Eqn.

Fig. 5.4 Push test set up and specifications of specimen…………………………… 217 -
Fig. 5.5 Tensile test setup ………………………………………………………… 217 -
Fig. 5.6 (a) 45° cone method (b) concrete capacity design (CCD) method……… 217 -
Fig. 5.7 (a) beam cross-section; (b) strain distribution; (c) stress distribution block; (d)
elastic force distribution; (e) plastic force distribution………………………………- 218 -
Fig. 5.8 Comparisons between the predictions and test results of push out test (J-
hook)…………………………………………………………………………………- 218 -
Fig. 5.9 Comparisons of the generalized P/P
u
-δ curves between the test and
predictions……………………………………………………………………………- 218 -
Fig. 5.10 Failure modes observed from the push out test……………………………- 219 -
Fig. 5.11 Observed failure modes from pull out test ……………………………… 219 -
Fig. 5.12 Load-elongation curve of pull out test…………………………………… 219 -
Fig. 5.13 Scatters of test-to-prediction ratios by the proposed design approaches in
Chapter 4, section 4.3 ……………………………………………………………… 219 -
Fig. 5.14 Effect of the parameters on the strength of the SCS sandwich composite
beams……………………………………………………………………………… 223 -
Fig. 5.15 Flexural failures……………………………………………………………- 224 -
Fig. 5.16 Vertical shear failures…………………………………………………… 224 -
Fig. 5.17 Connector failure………………………………………………………… 224 -
Fig. 5.18 Proposed FE model for SCS sandwich composite beams with J-hook
connector…………………………………………………………………………… 225 -
Fig. 5.19 FE verifications against the test results……………………………………- 226 -
Fig. 5.20 (a)~(f) Comparisons of the cracks in the core material between the FE model
and test……………………………………………………………………………… 227 -
Fig. 5.21 Scatter of the ratio of the experimental deflection-to-predicted deflection 228 -

List of Figures


Fig. 7.3 Illustration of tension membrane effect…………………………………… 318 -
Fig. 7.4 Scatters of ratios of test results-to-predictions by code or proposed
formulae…………………………………………………………………………… 318 -
Fig. 7.5 Comparisons of test results with predictions by codes and proposed
formulae…………………………………………………………………………… 319 -
Fig. 7.6 Comparisons of test results with predictions by code and proposed
List of Figures

XX 

formulae…………………………………………………………………………… 319 - List of Symbols and Acronyms

 XXI

LIST OF SYMBOLS AND ANRONYMS

Elastic Young’s modulus of steel material
H
Height of the headed shear stud connector
I
Second moment of area
t
K
Elastic stiffness of the mechanical shear connectors in the tension zone of concrete
under shear forces
c
K
Elastic stiffness of the mechanical shear connectors in the compression zone of
concrete under shear forces
J
N
Tension capacity of the J-hook connector
P
Applied shear load on the connector
J
P
Shear strength of the J-hook shear connector
u
P
Ultimate shear strength of the shear connector
Rd
P
Design shear strength of one single connector embedded in the concrete
List of Symbols and Acronyms

XXII

f
Ultimate strength of the steel material
ut
f
Ultimate strength of the steel anchors
ef
h Effective embedment depth, mm
c
t
Thickness of the compression steel plate, mm
s
t
Thickness of the tension steel plate, mm
w
Density of the concrete, kg/m
3
s
Spacing of connectors
x
The distance from the neutral axis to the top compression fiber of the concrete in
beam section