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Shear Behavior of Structural Lightweight

Concrete Beams A Thesis

Submitted to the Faculty of Engineering

Ain Shams University for the partial Fulfillment

of the Requirement of M.Sc. Degree

In Civil Engineering

Prepared by

Eng. Ashraf Freeg Saad Ragab

B.Sc. in Civil Engineering, June 2010

Higher Institute of Engineering – El Shorouk Academy

Supervisors

Prof. Dr. Ayman Hussein Hosny khalil

Professor of structural engineering

Faculty of Engineering, Ain Shams University, Cairo, EGYPT

Ass. Prof. Sherif Kamal Elwan

Associate Professor, Structural Engineering Department

Higher Institute of Engineering – El Shorouk Academy, Cairo, EGYPT

2017

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Shear Behavior of Structural Lightweight

Concrete Beams A Thesis For

The M.Sc. Degree in Civil Engineering (STRUCTURE ENGINEERING)

By Eng. Ashraf Freeg Saad Ragab

B.Sc. in Civil Engineering, June 2010

Higher Institute of Engineering – El Shorouk Academy

THESIS APPROVAL EXAMINERS COMMITTEE SIGNATURE

Prof. Dr. Mohammed Abo Zied Tarkhan

------------------

Prof. Dr. Amr Hussien Zaher

------------------

Prof. Dr. Ayman Hussien Hosny Khalil ------------------

Date: / /2017

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STATEMENT

This dissertation is submitted to Ain Shams University, Faculty of

Engineering for the degree of M.Sc. in Civil Engineering.

The work included in this thesis was carried out by the author in the

department of Structure Engineering, Faculty of Engineering, Ain Shams

University, from 2013 to 2017.

No part of the thesis has been submitted for a degree or a qualification at any

other University or Institution.

The candidate confirms that the work submitted is his own and that

appropriate credit has been given where reference has been made to the work

of others.

Date: - / / 2017

Signature: - ----------------

Name: - Ashraf Freeg Saad Ragab

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ABSTRACT

This research program was conducted to investigate the shear

behavior of structural lightweight concrete beams subjected to two-

point load. For this purpose, a finite element model using the

computer package ANSYS Ver.10 was developed, verified, and

implemented in an extensive parametric and analytical study.

All the necessary steps to create the models which are prepared

to investigate the behavior of structural lightweight concrete beams in

shear. The experimental results for shear of structural LWC beams

presented in the literature were used to verify the analytical study.

The experimental results were compared with finite element results to

verify the accuracy of finite element models. All beams had a

rectangular cross section of 150 mm wide and 300 mm total depth.

The beam effective depth was set to 275 mm. The clear span of the

tested beams was fixed for all beams to be 2000 mm but the total

length of beams was 2300 mm. All beams were tested under two-

point load.

A total of twenty-four beams (all beams are simply supported)

were analyzed. The analyzed beams were chosen to investigate the

effect of various parameters including using structural lightweight

concrete instead of ordinary concrete, variation of shear

reinforcement, and variation of cross section of the beams. The

breadth, depth, and length of the analyzed beams were 150, 300, and

2000 mm, respectively. Based on the analysis of results obtained

from finite element modelling of simply supported reinforced-

concrete beams, several conclusions are drawn as follow.

Insignificant enhancement in the ultimate load occurred when

using structural lightweight concrete instead of ordinary concrete.

Providing longitudinal shear reinforcement in reinforced concrete

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beam increases its ultimate capacity in shear. Using longitudinal

shear reinforcement instead of stirrups reduces its ultimate capacity in

shear. Increasing in the ultimate load occurred when using flanged

section instead of R-section. Reduction in the stiffness occurred when

using lightweight concrete instead of ordinary concrete. Providing

longitudinal shear reinforcement in reinforced concrete beam

increases the stiffness of beams. Using longitudinal shear

reinforcement instead of stirrups has minor effect on the stiffness of

beams. Increasing in the stiffness of beams occurred when using

flanged section instead of R-section.

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Acknowledgment

I would like to thank ALLAH for his blessings all the

way till I finished this research and throughout my life.

I wish to express my deep appreciation and gratitude to my supervisors for

their great effort in solving all the problems during this research and for their

valuable advice and encouragement,

Prof. Dr. Ayman Hussein Hosny khalil

Ass. Prof. Sherif Kamal Elwan

In addition, I would like to thank my colleagues for their help and advice

during this research.

Finally, but of great importance, I wish to express all the meanings of love,

gratitude and appreciation to my family (my father, my mother, my wife, my

brother and my sister) for their support and continuous prayers for me till

finishing this thesis.

Ashraf Freeg Saad Ragab

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CONTENTS vi ACKNOWLEDGEMENT ...................................................................................

vii CONTENTS ..........................................................................................................

X LIST OF FIGURES .............................................................................................

xv LIST OF TABLES ...............................................................................................

xvi LIST OF SYMBOLS............................................................................................

1 Chapter 1 ..............................................................................................................

2 1.1General .............................................................................................................

3 1.2 Research Objectives .......................................................................................

3 1.3 Thesis Outline .................................................................................................

5 Chapter 2 ..............................................................................................................

5 2. LITERATURE REVIEW ................................................................................

6 2.1 Introduction ....................................................................................................

7 2.2 Historical Background of Lightweight Concrete .........................................

8 2.3 Technical Definition of Lightweight Concrete .............................................

9 2.4 Classification of Lightweight Aggregates (LWA) ........................................ 9 2.5 Classification of Lightweight Concretes (LWC) [26] ..................................

11 2.6 Innovative Mix Design for Lightweight Concrete .......................................

12 2.7 Comparison of Foamed Concrete and Normal Concrete ...........................

12 2.8 Modulus of Elasticity and Stress-Strain Relationships ...............................

16 2.9 Compressive Strength ....................................................................................

18 2.10 Tensile Strength ............................................................................................

21 2.11 Previous Research on the Shear Behavior of LWC Beams .....................

21 2.11.1 Experimental Researches .........................................................................

29 2.11.2 Theoretical Researches .............................................................................

33 2.12 Finite Element Method ...............................................................................

33 2.13 Need for the Current Research ..................................................................

35 Chapter 3 ..............................................................................................................

35 3. FINITE ELEMENT ANALYSIS ...................................................................

36 3.1 Introduction ...................................................................................................

37 3.2 Ansys Program Description ..........................................................................

37 3.3 Non-linear Behavior in ANSYS Program ...................................................

37 3.4 Structural Element Types .............................................................................

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37 3.4.1 SOLID 65 .................................................................................................... 38 3.4.2 LINK8 .......................................................................................................... 39 3.4.3 SOLID45 ..................................................................................................... 31 3.5 Modeling of Reinforcement .......................................................................... 32 3.6 Sensitivity Study ............................................................................................

32 3.6.1 Introduction ..................................................................................................

32 3.6.2 Shear Transfer Coefficient ...........................................................................

33 3.6.3 Tensile Strength ............................................................................................

33 3.6.4 Modulus of Elasticity ...................................................................................

33 3.6.5 Failure Criteria For Concrete ........................................................................

37 3.7 F. E. Model Verification Using Experimental Data ....................................

37 3.7.1 Introduction ..................................................................................................

51 3.7.2 Element Type ..............................................................................................

51 3.7.3 Real Constants ............................................................................................

51 3.7.4 Material Properties ....................................................................................

58 3.7.5 Modeling and Meshing ...............................................................................

61 3.7.6 Loading and Boundary Conditions ...........................................................

61 3.7.7 Nonlinear Solution and Failure Criteria ..................................................

62 3.7.8 Verification of the Proposed Finite Element Model ................................

68 Chapter 4 ...............................................................................................................

68 4. Parametric Study…………………………………………………………….

69 4.1 Introduction ......................................................................................................

69 4.2 Description of The Analyzed Beams ................................................................

71 4.3 Material Properties ...........................................................................................

71 4.4 Investigated Parameters ....................................................................................

72 4.5 Determination of Reinforcement ...................................................................

73 4.6Results and Discussion .................................................................................... 73 4.6.1 Crack Patterns and Modes of Failure ........................................................ 73 4.6.1.1 Mechanism of Cracking in ANSYS ......................................................... 77 4.6.1.2 Crack Patterns .......................................................................................... 81 4.6.1.3 Cracking Loads ........................................................................................ 82 4.6.2 Loads at Failure ........................................................................................... 82 4.6.2.1 General ..................................................................................................... 83 4.6.2.2 Effect of Using LWC ............................................................................... 83 4.6.2.3 Effect of Variation of Shear Reinforcement .......................................... 83 4.6.2.4 Effect of Cross Section ............................................................................ 83 4.6.3 Deflection at Failure .................................................................................... 83 4.6.3.1 General ...................................................................................................... 83 4.6.3.2 Effect of Using LWC ................................................................................ 85 4.6.3.3 Effect of Variation of Shear Reinforcement ........................................... 85 4.6.3.4 Effect of Cross Section .............................................................................

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92 4.6.4 Load-Deflection Curves............................................................................... 92 4.6.4.1 General ..................................................................................................... 92 4.6.4.2 Effect of Using LWC ............................................................................... 94 4.6.4.3 Effect of Variation of Shear Reinforcement .......................................... 97 4.6.4.4 Effect of Cross Section .............................................................................. 98 4.6.5 Stress in Reinforcement ..............................................................................

105 Chapter 5 ............................................................................................................... 105 5.ANALYTICAL STUDY .................................................................................... 106 5.1 Introduction .................................................................................................... 106 5.2 ACI 318-14 ....................................................................................................... 109 5.3 EUROCODE .................................................................................................... 112 5.4 Recommendation for Egyptian Code ................................................................ 113 Chapter 6 ...............................................................................................................

113 6. SUMMARY AND CONCLUSIONS ............................................................... 114 6.1 Summary ......................................................................................................... 114 6.2 Conclusions ..................................................................................................... 117 6.3 Suggestions for Future Research ................................................................... 118 REFRENCES ........................................................................................................

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LIST OF FIGURES Figure (2.1) – Approximate unit weight and use classification of lightweight aggregate

concretes [72]………………………………………………………. 9

Figure (2.2) – Bi-linear stress-strain diagram for cross-section design DIN 4219 T.2 [45]

………………………………………………………………………… 15

Figure (2.3) – The obtained stress-strain curve for foam balls lightweight concrete cube

[1] …………………………………………………………………………… 16

Figure (2.4) – Relationship between mix density and 28 day cube compressive strength

[1] ……………………………………….…………………………... 18

Figure (2.5) – Types of tension tests …………………………………….……… 19

Figure (2.6) – Relationship between the splitting tensile strength and the cube

compressive strength of FBLWC [1] ………………………………..…….… 21

Figure (3.1) – A schematic of the element [25] ………………….……………….. 38

Figure (3.2) – LINK8 geometry [72] ……………………….…………………….. 39

Figure (3.3) – SOLID45 geometry [72] …………………….…………………….. 31

Figure (3.4) – Models of reinforcement (a) discrete; (b) embedded; and (c) smeared [72]

………………………………………………………………………………... 31

Figure (3.5) – Numerical load versus different values of shear transfer coefficient for

open crack ………………………………….…………………….…………………….. 33

Figure (3.2) – Numerical load versus modulus of elasticity ……………………..…….. 33

Figure (3.7) – 3-D failure surface for concrete [25] …..………….…………………….. 36

Figure (3.8) – Reinforcement and concrete dimensions of beams tested under shear (B1,

B2, B3, and B4) ……………….…………………………………………...... 38

Figure (3.9) – Reinforcement and concrete dimensions of beams tested under shear (B5,

B6, B7, and B8) …………………………………………….…………………………..

39

Figure (3.10) – Simplified compressive uniaxial stress-strain curve for concrete [37]

…………………………………………………………………………………………….. 55

Figure (3.11) – Stress-strain curve for steel reinforcement …………………………….. 57

Figure (3.12) – Element connectivity [29] ……..…..………….…………………….. 58

Figure (3.13) – Geometric mesh of concrete, steel plate, steel support ………..…….. 59

Figure (3.14) – Reinforcement configuration for (B1) ……………..………………... 59

Figure (3.12) – Reinforcement configuration for (B2), (B3) …………………….. 61

Figure (3.12) – Model of boundary condition and loading ………………………. 61

Figure (3.12) – Experimental and numerical load versus mid span deflection plots of B1

tested by Wessam Antar et al. [11] …………………………………………..

63

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Figure (3.18) – Experimental and numerical load versus mid span deflection plots

of B2 tested by Wessam Antar et al. [11] ………………………………………

64

Figure (3.19) – Experimental and numerical load versus mid span deflection plots

of B3 tested by Wessam Antar et al. [11] ……………………………………….

65

Figure (3.20) – Experimental and numerical load versus mid span deflection plots

of B4 tested by Wessam Antar et al. [11] ………………………………..………...

65

Figure (3.21) – Experimental and numerical load versus mid span deflection plots

of B5 tested by Wessam Antar et al. [11] ………………………………..………...

66

Figure (3.27) – Experimental and numerical load versus mid span deflection plots

of B2 tested by Wessam Antar et al. [11] ………………………………..………...

66

Figure (3.23) – Experimental and numerical load versus mid span deflection plots

of B2 tested by Wessam Antar et al. [11] ………………………………..………...

67

Figure (3.24) – Experimental and numerical load versus mid span deflection plots

of B8 tested by Wessam Antar et al. [11] ………………………………..………...

67

Figure (4.1) – Cross-section for all the tested beams …………………………….. 71

Figure (4.2) – Integration points in concrete solid element, Kachlakev [72] …….. 76

Figure (4.3) – Cracking sign, Kachlakev [72] ……………………………………. 76

Figure (4.4) – Typical cracking signs occurring in finite element models,

Kachlakev [29]: (a) Flexural cracks; (b) Compressive cracks; (c) Diagonal tensile

cracks ……………………………………………………………………………….

77

Figure (4.5) – Crack patterns of beams (1); (2); (3) and (4) …….………………... 78

Figure (4.6) – Crack patterns of beams (5); (6); (7) and (8) …….………………... 79

Figure (4.7) – Crack patterns of beams (9); (10); (11) and (12) …….……………. 79

Figure (4.8) – Crack patterns of beams (13); (14); (15) and (16) ….……………... 81

Figure (4.9) – Crack patterns of beams (17); (18); (19) and (20) ………….……... 81

Figure (4.10) – Crack patterns of beams (21); (22); (23) and (24) …………….…. 81

Figure (4.11) – Deflection at failure of beam (1) ………………………………… 86

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Figure (4.12) – Deflection at failure of beam (2) ………………………………… 86

Figure (4.13) – Deflection at failure of beam (3) ………………………………… 86

Figure (4.14) – Deflection at failure of beam (4) ………………………………… 86

Figure (4.15) – Deflection at failure of beam (5) ………………………………… 87

Figure (4.16) – Deflection at failure of beam (6) ………………………………… 87

Figure (4.17) – Deflection at failure of beam (7) ………………………………… 87

Figure (4.18) – Deflection at failure of beam (8) ………………………………… 87

Figure (4.19) – Deflection at failure of beam (9) ………………………………… 88

Figure (4.20) – Deflection at failure of beam (10) ……………………………...... 88

Figure (4.21) – Deflection at failure of beam (11) ……………………………….. 88

Figure (4.22) – Deflection at failure of beam (12) …………………………….. 88

Figure (4.23) – Deflection at failure of beam (13) …………………………….. 89

Figure (4.24) – Deflection at failure of beam (14) …………………………….. 89

Figure (4.25) – Deflection at failure of beam (15) …………………………….. - 89

Figure (4.26) – Deflection at failure of beam (16) …………………………….. 89

Figure (4.27) – Deflection at failure of beam (17) …………………………….. 91

Figure (4.28) – Deflection at failure of beam (18) …………………………….. 91

Figure (4.29) – Deflection at failure of beam (19)……………………………….. 91

Figure (4.30) – Deflection at failure of beam (20) …………………………….. 91

Figure (4.31) – Deflection at failure of beam (21) …………………………….. 91

Figure (4.32) – Deflection at failure of beam (22) …………………………….. 91

Figure (4.33) – Deflection at failure of beam (23) …………………………….. 91

Figure (4.34) – Deflection at failure of beam (24) …………………………….. 91

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Figure (4.35) – Load-deflection curve of Rec. Sec. beams (Group1) ………….……. 93

Figure (4.36) – Load-deflection curve of T Sec. beams (Group2) ……………..……. 93

Figure (4.37) – Load-deflection curve of L Sec. beams (Group3) ……………..……. 94

Figure (4.38) – Load-deflection curve of Rec. Sec. beams with stirrups ………..…. 95

Figure (4.39) – Load-deflection curve of T Sec. beams with stirrups ………..…. 96

Figure (4.40) – Load-deflection curve of L Sec. beams with stirrups ………..…. 97

Figure (4.41) – Load-deflection curve of beams (1, 5, 9, 13, 17 and 21) …..………. 98

Figure (4.42) – Stress in reinforcement of beam (1) ……………………………. 98

Figure (4.43) – Stress in reinforcement of beam (2) ……………………………. 99

Figure (4.44) – Stress in reinforcement of beam (3) ……………………………. 99

Figure (4.45) – Stress in reinforcement of beam (4) ……………………………. 99

Figure (4.46) – Stress in reinforcement of beam (5) ……………………………. 99

Figure (4.47) – Stress in reinforcement of beam (6) ……………………………. 111

Figure (4.48) – Stress in reinforcement of beam (7) ……………………………. 111

Figure (4.49) – Stress in reinforcement of beam (8) ……….…….…….…….…. 111

Figure (4.50) – Stress in reinforcement of beam (9) ……………………………. 111

Figure (4.51) – Stress in reinforcement of beam (10) …………….………..…… 111

Figure (4.52) – Stress in reinforcement of beam (11) …………..…….………… 111

Figure (4.53) – Stress in reinforcement of beam (12) …………………………... 111

Figure (4.54) – Stress in reinforcement of beam (13) …………………………... 111

Figure (4.55) – Stress in reinforcement of beam (14) …………………………... 112

Figure (4.56) – Stress in reinforcement of beam (15) …………………………. 112

Figure (4.57) – Stress in reinforcement of beam (16) …………………………. 112

Figure (4.58) – Stress in reinforcement of beam (17) …………………………. 112

Figure (4.59) – Stress in reinforcement of beam (18) …………………………. 113

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Figure (4.60) – Stress in reinforcement of beam (19) …………………………. 103

Figure (4.61) – Stress in reinforcement of beam (20) …………………………. 103

Figure (4.62) – Stress in reinforcement of beam (21) ………………………….. 113

Figure (4.63) – Stress in reinforcement of beam (22) ………………………… 113

Figure (4.64) – Stress in reinforcement of beam (23) ………………………….. 113

Figure (4.65) – Stress in reinforcement of beam (24) …………………………. 113

Figure (5.1) – Comparison among failure loads ……….…………………………. 112

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LIST OF TABLES

Table (2.1) Mix proportions/m3 for the LWC ……………. .……….………………… 12

Table (2.2) Characteristics of foamed concrete and normal concrete …………………… 12

Table (3.1) Details of beams tested under shear ………….………..………….. 37

Table (3.2) Real constant for beams (steel reinforcement) …………..….…….. - 51

Table (3.3) Linear isotropic material properties for LWC model ………..……… 53

Table (3.4) Linear isotropic material properties for O.C. model …..….………. 53

Table (3.5) Nonlinear material properties for concrete model ……...…………. 53

Table (3.6) Multi-linear isotropic material properties for LWC model ….……. 53

Table (3.7) Multi-linear isotropic material properties for O.C. model ….…….. 55

Table (3.8) Linear isotropic material properties for long. RFT ……….………. 56

Table (3.9) Bilinear isotropic material properties for long. RFT ……………… 56

Table (3.10) Linear isotropic material properties for stirrups …………………. 57

Table (3.11) Bilinear isotropic material properties for stirrups ………………... 57

Table (3.12) Linear isotropic material properties for steel plate ………………. 57

Table (3.13) Nonlinear analysis ……………………………………………….. 62

Table (3.14) Comparison between experimental and finite element failure loads .. 63

Table (4.1) Description of the analyzed beams ……………….………………….. 71

Table (4.2) The cracking load of all modeled beams ……………….………………….. 82

Table (4.3) The failure load of all modeled beams …………………..…………… 83

Table (6.1) The failure and analytical load of all modeled beams (ACI 318-14) ….…… 118

Table (6.2) The failure and analytical load of all modeled beams (EUROCODE) ….…… 111