CONTENTS
SECTION
PAGE
I. FOREWORD
1
A. Photographs and Diagrams
4
II. SYNOPSIS
9
III. FACTS
10
A. Summary of Work Prior to October 1968 and Questions Which Remained Unresolved at That Time
10
1. Field Operations Completed as of October 1968
10
2. Laboratory Work Reported in Interim Report
11
3. Observed Facts and Witness Testimony Inadequately Explained at the Time of Interim Report
12
4. Logical Framework for the Conduct of the Investigation
13
B. Field Investigations Since September 1968
19
1. Further Examinations at Reassembly Site
19
a. Hanger connection at U13N
20
b. Cleavage fractures in hangers
20
c. Cleavage fracture in lower chord
20
d. Scars and deformations in Ohio tower
20
e. Presence of numerous cleavage fractures
21
2. Detailed Survey of the Extent of Corrosion on Eyebars Chain and Stiffening Trusses
22
3. Experimental Measurements on the St. Marys Bridge
23
a. Natural modes and frequencies
23
b. Dynamic response due to moving vehicle
23
c. Secondary effects in chain bent post and other members
23
d. Susceptibility of eyebars joints to rotation
24
e. Lateral distortions due to single lane loads
24
C. Laboratory Investigations Since September 1968
25
1. Laboratory Investigations at the National Bureau of Standards
25
a. Chemical and metallurgical examination of eyebars steel
25
b. Metallurgical and mechanical tests of eyebars steel
32
c. Fractographic and microprobe studies of fracture in eyebars No. 330
34
d. Chemical and mechanical tests of A7-24 steel
37
e. Examination of fracture in hanger U17N, part 12C
39
f. Examination of fracture in chord member L12-L13N
42
g. Rivet failures in joint U13N
42
h. Other NBS investigations
45
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