Contents of the 60TH Anniversary Series, Volume 9, Recent Experimental Investigations into the Strength of Ship Structures in Japan

The Society of Naval Architects of Japan

60TH ANNIVERSARY SERIES

VOLUME 9

RECENT EXPERIMENTAL INVESTIGATIONS

INTO THE STRENGTH OF SHIP

STRUCTURES IN JAPAN

By

Kazuo

with the collaboration of

JunkicM

Yoshikazu

Ko N l S H I M A K I

The Society of Naval Architects of Japan

Tokyo, 1964

C O N T E N T S

P R E F A C E

Page

CHAPTER 1. ON THE TRANSVERSE STRENGTH OF OIL TANKERS 1

Introduction 1 , 1 . 1 Methods of the Experiments w i t h Actual Tankers 3

1.1.1 Test Methods 3 1.1.2 Constructions of Subject Tankers 3

1.1.3 Subject of Experiments 4 1.1.4 Measuring Apparatuses 6 1.2 Progress and Results of Experiments 7

1.2.1 Progress of Experiments 7 1.2.2 Results of Experiments 10 1.2.3 Some Brief Considerations on the Results of Experiments 22

1.3 Calculation Methods of Transverse Strength of Tankers 28 1.3.1 Fundamental Formulas of Slope Deflection Method 28 1.3.2 Calculating Equations of the Transverse Strength of Tankers i n Accordance

w i t h the Slope Deflection Method 32 1.3.2.1 Equations f o r the transverse web frame 32

1.3.2.2 Effects of the horizontal girders 34 1.3.2.3 Effects of the shell plate, bulkhead and longitudinal girders on the center

line 36 1.4 Calculation on Actual Ships 40

1.4.1 Some Considerations on the Execution of Calculation 40

1.4.2 Results of Calculation 43 1.4.3 Investigation i n Comparison w i t h the Experimental Results on Actual Tankers 45

Conclusion 48 References 50

CHAPTER 2. STRESS DISTRIBUTION I N DECKHOUSE A N D SUPERSTRUCTURE.... 51

Introduction 51 2.1 Elastic Behavior of Deckhouse 51

2.2 Analysis of Deckhouse w i t h Shear Lag Effect 53 2.2.1 Analysis Based on the Energy Method 53 2.2.1.1 Assumption of stress distribution i n the structures 53

2.2.1.2 The condition of minimum strain energy 57 2.2.1.3 Correction of longitudinal stresses due to the change of upper deck reaction

forces 61 2.2.1.4 Analysis f o r a ship-structure subjected to uniform bending 65

2.2.2 Analysis Based on a Shear Deformation Theory 68

2.2.2.1 Basic equations 68 2.2.2.2 Solutions to the basic equations 73

2.2.2.3 Approximate method f o r the case of small value ot K 76 2.2.2.4 A solution f o r the case of infinitely large value of K 80 2.3 Approximate Analysis of Deckhouse and Superstructure Under Bending 82

ii CONTENTS

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2.3.1 Effective Area and Effective Moment of Inertia of Deckhouse 83

2.3.1.1 Effective area 83 2.3.1.2 Effective moment of inertia 87

2.3.1.3 Comparison between theoretical and experimental values of the effective

area ' 88 2.3.2 A n Approximate Analysis of Deckhouse Under Bending 89

2.3.2.1 Deckhouse supported by upper deck under which no, one or two transverse

bulkheads exist 89 2.3.2.2 Deckhouse supported by the upper deck under which many transverse

bulkheads exist 93 2.3.3 A n Approximate Analysis of Superstructure Under Bending 94

2.3.3.1 Stiffness factor, K 94 2.3.3.2 Approximate analysis of superstructure under bending 96

2.3.4 Simplified Formula f o r Bending of Superstructure 97 2.4 Investigation into the Infiuence of Side Openings and Corrugations of Side

Walls Upon the Behavior of Deckhouse 99 2.4.1 The Bending Theory of Deckhouse w i t h Many Side Openings of its Side

Walls 99 2.4.1.1 Deformation coefficient of side wall w i t h openings 99

2.4.1.2 Behavior of the superstructure w i t h openings, subjected to a tensile force 100

2.4.1.3 Deformation of the deckhouse at the opening under bending 102

2.4.1.4 Effective area 103 2.4.1.5 Effective moment of inertia 106

2.4.2 Bending Theory for Deckhouse w i t h Corrugated Walls 107 2.4.2.1 Bending theory for deckhouse constructed of vertically corrugated plates

without stiffeners 108 2.4.2.2 Bending theory for deckhouse constructed of vertically corrugated plates

and stiffened vertically 113 2.4.2.3 Bending theory for deckhouse constructed of horizontally corrugated plates 117

2.5 Comparison Between Theoretical and Experimental Results on Ship Models.... 119

2.5.1 Facilities for Ship Model Tests 119 2.5.1.1 Apparatus to apply bending 119

2.5.1.2 Ship model 120 2.5.1.3 Measurement of strains 120

2.5.2 Comparison of Theoretical Results w i t h Experimental Ones on a Model

Furnished by Deckhouse 121 2.5.2.1 Influence of the length of deckhouse on the shear lag effects 121

2.5.2.2 Comparison of tests results w i t h an approximate theory 123 2.5.3 Comparison of Theoretical Results w i t h Experimental Ones on a Model

Furnished by Superstructure 125 2.5.3.1 Comparison of theoretical results based on the approximate theory 125

2.5.3.2 Comparison of the results between the theory and simplifled ones 127 2.5.4 Comparison of Theoretical Results w i t h Experimental Ones on a Model

Furnished by Superstructure w i t h Side Openings 128 2.5.5 Comparison between the Theory and Experiments on the Model w i t h

Super-structures of Corrugated Plates 131 2.5.5.1 On the model w i t h superstructures of vertically corrugated plated 131

2.5.5.2 On the model w i t h superstructures of horizontally corrugated plates 135

CONTENTS i i i

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2.6.1 Test Results of the BRAZIL MARU and its Analysis 137

2.6.1.1 Ship construction of the BRAZIL MARU 137 2.6.1.2 Measured longitudinal strains on the BRAZIL MARU 138

2.6.1.3 Simplified model for analysis of the BRAZIL MARU 140

2.6.1.4 Evaluation of stiffness factor 140 2.6.1.5 Effective area and effective moment of inertia of the deckhouse of the

BRAZIL MARU 141 2.6.1.6 Calculation of longitudinal bending moment and deflection of the simpHfled

model 142 2.6.1.7 Comparison of the results between the experiment and theory regarding

longitudinal stresses 143 2.6.2 Test Results and its Analysis f o r a Submarine Chaser 144

2.6.2.1 Ship construction of a submarine chaser 144

2.6.2.2 Results of bending test 145 2.6.2.3 Analysis of test results 147

References 150

CHAPTER 3. STRESS CONCENTRATIONS AROUND STRUCTURAL DISCONTINUITIES

OF SHIPS ' 151

Introduction 151 3.1 Stress Concentration at the Hatchway Corner 152

3.1.1 Experimental Investigations on Large Size Models 152

3.1.1.1 Outline of the experimental researches 152 3.1.1.2 Experimental studies on the stress concentrations and methods of

reinforce-ment at the hatchway corner 153 3.1.2 Investigations Based on Results of Experiments on Actual Ships 162

3.1.2.1 Outline of the experiments on actual ships 162 3.1.2.2 Stress concentration at the hatchway corner of actual ships 163

3.2 Strength and Stress Concentration at the Intersection of Bottom Longitudinals

and Transverse Bulkhead of Tankers 173 3.2.1 Experimental Investigations on Large Size Models 173

3.2.2 Stress Measurements on Actual Ships and Comparison of Results Between

Models and Actual Ships 179 3.3 Other Investigations Regarding Stress Concentrations 180

3.3.1 Stress Concentrations i n the Vicinity of the Ends of Superstructure and

Deckhouse 180 3.3.1.1 Stress concentration i n the vicinity of bridge ends 180

3.3.1.2 Stress concentration around an entrance on deckhouse sides 187 3.3.1.3 Causes of damages at the ends of superstructure and deckhouse, and

precautions to be taken 189 3.3.2 Stress Concentration i n Brackets 194