Bridge Design Report: Load Considerations, Girder and Bearing Analysis

This report provides a detailed analysis of bridge design, focusing on several key aspects. It begins with a discussion of load considerations, differentiating between dead and live loads, and explaining the importance of load factors, especially concerning dynamic loads from moving vehicles. The report then moves on to girder design, outlining how to classify cross-sectional shapes and the elements that need to be checked, including webs, flanges, and stiffeners. It also discusses the advantages of having a larger bottom flange. The report further delves into bearing design, explaining the features of laminated elastomeric bearings and their benefits. Finally, it touches upon bridge economics and the impact of design changes on seismic performance, providing a comprehensive overview of structural engineering principles and practices. The report references several research papers to support its findings.

BRIDGE DESIGN
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Question 4
Loads
As the magnitudes of the dead loads can be predicted easily as compared to live loads, the live
load factors are greater.
The impact factor for a bridge is mainly governed by dynamic / moving vehicular loads and
affects the superstructure. But for the expansion joint the effects might not be as pronounced,
thus although it may affect the slab but won't affect the global performance (Shin et al., 2016).
There are numerous load combinations to assess the impact or to find the design load while
designing a bridge. These are dead loads, live loads, earthquake loads, wind loads, etc.
The moving trucks indicate live / dynamic / moving loads which contribute significantly to
bridge failures. Unless we take into account these loads we cannot assess the serviceability of the
structure. These are temporary loads
If we just place a stationary truck then it will only act as dead load to the structure but we won't
be able to assess the impact on the entire bridge span w.r.t. time which is done by influence line
diagram.
For LL, the appropriate load factor actually depends on the combination.
For a combination of LL with DL it is 1.5
For LL with DL and EL it is 1.2
On an average for heavy mining trucks it is 1.33

Girder Design
How to check
The cross sectional shape of the compression members is divided as compact, non-compact, or
slender. It is done based on the ratio between the breadth and thickness of the plate members.
Local buckling is discussed as a phenomenon controlling strength of compression and bending
members. The cross-sections are classified into plastic, compact, semi-compact as well as
slender depending upon their moment-rotation characteristics.
The flexural capacity of an adequately braced beam depends on the slenderness ratio of the
compression flange and web. When the slenderness ratios are sufficiently small, the beam can
attain its full plastic moment and cross section is classified as compact
When the slenderness ratios are larger, the compression flange or the web may buckle locally
before a full plastic moment is attained and cross section is classified as non-compact
When the slenderness ratios are sufficiently large, local buckling will occur before the yield
stress of the material is reached and cross section is classified as slender
Which elements should be checked?
1. Web: The deep central vertical plate is called as a web in plate girder. It separates the two
flange plates by a required distance. Web is responsible to resist shear developed in the
plate girder (Veganzones et al., 2016).
2. Flanges: Flanges or flange plates are horizontal elements of plate girder which are
provided at the top and bottom and they are separated by the web. The main purpose of
flange plates is to resist the bending moment acting on the girder
3. Stiffeners :
Stiffeners are classified into two types

Horizontal stiffeners and vertical stiffeners
Advantages of having bottom flange lager than a top flange
Out of the number of structural terms going on, there is one in particular term called Bending
Stress which provides a basis on how to select a suitable member according to loading.
This basic fundamental states a crucial fact, no matter what kind of member you choose the
maximum stress will be resisted by the upper and lower edges or we can say, as we go towards
the center the amount of stress acting at that point will be lesser from the previous point (Xin et
al., 2017). Our aim is to provide maximum concentration of mass at a point undergoing
maximum bending stress.
Bearing design
Laminated elastomeric bearing features reinforced steel plates which are sandwiched between
layers of rubber via vulcanization as well as molding manufacturing process to form
homogeneous unit. Not only do such embedded steel plates limit excessive expansions, but as
well increase transversal, longitudinal alongside compressive strength and rotation capability in
comparison with plain elastomeric bearings (Yoo and Yoon, 2016).
Bridge Economics
It will be cheaper but consumer a lot of time to construct
Question 5
The change improves the seismic performance of bridges.

References
Shin, D.H., Chung, C.H., Oh, H.C., Park, S.J., Kim, I.G., Kim, Y.J., Byun, T.K. and Kang, M.G.,
2016. Structural behavior of precast concrete deck with ribbed loop joints in a composite
bridge. Smart Structures and Systems, 17(4), pp.559-576
Veganzones Muñoz, J.J., Pacoste, C., Pettersson, L. and Karoumi, R., 2016. The influence of the
edge beam on the structural behavior of bridge deck overhangs
Xin, H., Mosallam, A., Liu, Y., Wang, C. and Zhang, Y., 2017. Analytical and experimental
evaluation of flexural behavior of FRP pultruded composite profiles for bridge deck structural
design. Construction and Building Materials, 150, pp.123-149
Yoo, D.Y. and Yoon, Y.S., 2016. A review on structural behavior, design, and application of
ultra-high-performance fiber-reinforced concrete. International Journal of Concrete Structures
and Materials, 10(2), pp.125-142