Steel bridge structure without intermediate bracing system (IBS) has been widely used in several countries and one of them is Japan. In this type of structure, the main steel girder is not reinforced by the stiffeners. The stiffness of the main girder is enhanced with steel plate directly welded to the top flange of the main girder, forming the “beams–system”. The reinforced concrete deck slab with the set of main girder and steel plate works compositely through steel shear connectors whose shape is C (channel) or I character. As for steel bridge structures, the main role of shear connectors is shear resistance between the concrete deck slab and steel girder plate in the exploitation stage. However, previous research has shown that the density of shear connectors influences on the stability as well as the stiffness of the bridge structure. Therefore, it has approved that this appurtenance is able to not only have the ability of shear resistance but also enhance the stiffness of the steel bridge structure which is particularly surveyed with the type of especial bridge structure – the steel bridge structure without IBS. Hence, the shear connectors in this kind of bridge structure are deliberately researched as an extra role in the construction stage. The following factors of the channel shape shear connectors would be researched for evaluating their impacting level on the stability of the special steel bridge structure: the properties (the length and the moment of inertia of the cross-section) and the density on the steel plate. Through the analysis of impacting level to the stability of three mentioned factors (the length and density of the shear connectors; the moment of inertia of the cross-section), the expected result is as following: 1) The minimum density of shear connectors is proposed. 2) The influence of the moment of inertia of the cross-section, the density, and the length on the stability is quite clear. 3) As for the economy, the optimal designed range among three factors is also suggested.

Nowadays, steel bridge structure is becoming the trend of highways and bridges construction industry on not only the material characteristic but also its ability to be manufactured easily and reduce the constructing time. However, this structure still has its own disadvantages. One of the most critical factors greatly influencing the performance of the whole structure is the buckling capacity of the main girders, especially during construction stage. The most common solution for increasing the structure’s buckling capacity is to provide it with discrete bracing along the girder’s length. The designing of bracing for steel bridges requires high precision. If the design of the system is much stiffer than it demands, the structure will easily be prone to fatigue problems. In the other hand, if the bracing design does not meet its required stiffness, the whole structure’s stability will greatly reduce. Presently, many projects are designed too sufficiently leading to a huge waste of cost and time. Therefore, the expected results of this study are to propose an optimal design process for the bracing system design of steel I girder simple span bridges and a finite element model of a real-life steel bridge to confirm the reliability of the specification proposed.