1. Ma Su Wit Yi Mon

2. DEPARTMENT OF CIVIL ENGINEEARING

3. VARIATION OF JOINT FORCES
IN STEEL TRUSS BRIDGE
SUPERVISOR STUDENT
Dr. Kyaw Kyaw Ma Su Wit Yi Mon
Department of Civil Engineering Roll No. C-34 (M.E. Thesis)

4. Objectives of the Study
 To know the components of steel truss bridge.
 To know how to design a superstructure of steel truss
bridge.
 To understand the concepts of the influence line analysis
of steel truss bridge with the application of STAAD-Pro
structural software.
 To study about the variation of joint forces in steel truss
bridge.
 To safe the failures because of the effects such as
seismic, wind, traffic loads, and so on.

5. Scope of the Study
 Only superstructure of steel truss bridge will be designed.
 In this study, American Association of State Highway and
Transportation Officials (AASHTO) will be used.
 The live load is chosen HS 20-24 for six lanes.
 The structure will be analyzed by using STAAD-Pro
structural software and study for joints design and
preliminary design.
 Parallel Chord Warren truss will be designed.
 The bridge type is simple span truss bridge.

6. Implementation Programs
 Study on theoretical background for steel truss bridge.
 Study on configuration of proposed bridge.
 Study on preparation for analysis of bridge.
 Study on modeling analysis of bridge using STAAD-Pro
structural software.
 Study on joints design of steel truss bridge.
 Discussions, conclusions and recommendation for the
study of variation of joints forces for steel truss bridge.

7. Applicable span of Truss Bridge
Truss brides are generally applied within the following range.
1. Simple truss bridge is in the range of 55 meter to 85 meter
span.
2. Continuous truss bridge is in the range of 60 meter to 300
meter span.
3. Cantilever truss bridge is in the range of 300 meter to 510
meter span (in Japan, only one bridge has longer span than
200 meter, and that is Minato Ohashi, with 510 meter span.
Among the 3 types of bridges, the simple truss bridge
or the continuous truss bridge, either with approximate 60
meter to 100 meter span is usually applied.

8. Characteristics of Truss Bridge
1. Truss which is a frame structure composed of straight
members is built by connecting the members with pins
or by a member analytically regarded as connected with
pins.
2. As load is regarded to work on the panel point only, no
bending moment and shear forces but only axial force
works to the members composing the truss.
3. Due to problems of wearing of pins and gathering rust,
gusset plates are mostly used to connect the members
by use of high-tension bolts.
4. Bending moment occurs in the members and the
secondary stress is expected to arise due to bending.
5. However in case of ordinary truss bridge, influence of
the secondary stress can be ignored.

9. Advantages of Truss Bridge
Mountain Region
1. When the members are difficult to be transported to the site and
when the conditions of construction is restricted.
2. When a bridge in a curve alignment is required, a horizontal
bent continuous bridge or a deck truss bridge with brackets can
selected.
Open Field Region
1. Assurance of space below the bridge soffit due to adoption of
through bridge
2. Long span bridge over the mouth of a river or the coast.
3. Double-deck bridge having upper and lower 2-layer road
surface.

10. Disadvantages of Truss Bridge
1. As it is composed by many members, maintenance
requirements such as repainting is needed.
2. The sight view from the driver in case of through
bridges.

11. Over all height of truss
and length between panels
1. For simple truss, the truss height is 1/7-1/8 time the span
length and the length between panels is 1/6-1/8 time the
span length.
2. For continuous truss, the truss height is 1/9- 1/10 time
the span length and the length between panels is 1/8-
1/10 time the span length

12. Components of Superstructure of a Steel Truss Bridge
1. Upper Chord
2. Lower Chord
3. Upper Lateral Bracing
4. Lower Lateral Bracing
5. Portal Bracing
6. End Post
7. Bearing
8. Diagonal Member
9. Vertical Member
10. Floor Beams
11. Stringers
12. Sway Bracing
13. Upper Lateral Strut
14. Sway Strut
15. Gusset

14. Thank You
Ma Su Wit Yi Mon