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Many natural disasters cause not only critical situations for facilities and resident’s residents’ life, but also significant damage to economy. It is obvious that quick rescue action must be undertaken and that there are many problems due to the occurrence of secondary disasters at rescue worksite. Basing Based on the previous study of deployable structures and the concept of the multi-folding micro-structures, we propose a new type of foldable bridge in form of scissor structure called the Mobile-bridge?. In this paper, we discuss the vehicle passing test performed on the real-scale Mobile-bridge in order to evaluate its mechanical characteristics and application limits. Moreover, we verified the compatibility between the result of calculations and experiments by means of theoretical modelling. The results show that it is sufficient to treat the load as equivalent nodal forces applied at the joints without including the stiffness of the deck.

In recent years, the world has seen many kinds of natural disasters such as earthquakes, floods and tsunamis. In a case of our floods investigation, many residents suffered from bridge and road damage caused by very strong rains along several river branches in the northern Kyushu of Japan in 2012. Therefore, bridge designers or engineers have to consider how to rebuild the damaged infrastructure, and how to build new types of rescue systems, which can be quickly deployed, because rescue time is very important when trying to save lives in an emergency. Based on the previous study of the previous study of deployable structures and the concept of the multi-folding micro-structures [

The schematic view of the experimental, two-unit scissors model for a real scale mobile bridge (called as MB1.0) is shown in

In the final stage of expansion the scissors deployment angle is 60 degrees. The total length of the span is 7.0 m and the height of the bridge is 2.0 m. The total weight of the bridge including structural parts such as main members, shafts, and pins is 8.4 kN. The aluminum alloy components are made of the three-chamber hollow section, which uses A6N01 material, is used for the main member, the plastic bending moment is 20.1 kNm, and the ultimate bending strength is 39.9 kNm. The deck on which vehicles travel (called the aluminum alloy deck, hereafter) consists of A6063 extrusion sections. Only the portion of the aluminum alloy deck on which wheel loads act was constructed, because of weight saving. Moreover, the deployment action aims at shortening the construction time by uniting and interlocking the scissors member and the aluminum alloy deck. The properties of the A6N01 material are: E = 61.0 GPa, σ_{B} = 198.8 MPa, and σ_{y} = 180.0 MPa, while for the A6063 material E = 68.0 GPa, σ_{B} = 150.0 MPa, and σ_{y} = 110.0 MPa.

A Free Body Diagram (called FBD) for a unit of scissors structure is shown in _{0} and the angle of inclination is θ, the sectional length λ and height 2 h are L_{0}sinθ = λ and L_{0}cosθ = 2 h. So, the construction and storage of such a structure can be shown by the angle θ. This unit scissors structure

can be designed by using the equation of equilibrium. The equation of equilibrium concerning each the external force V_{A} − V_{E} and H_{A} − H_{E} is given as two expressions,

Looking at the members AE and BD that intersect as shown in

Let us consider the case of cantilever model which is pinned support for point A and point D. It is possible to use the matrix by arranging the four calculated equilibrium Equations (1)-(4) as shown in Equation (5).

Similarly, we can get equilibrium as Equation (6) in the simple beam model which is pinned support for point A and point B,

From the above results, unknown reaction forces can be obtained by considering the loading condition and the boundary condition for these.

Next, let us consider the mechanical model when adding the deck to the fundamental theory of the scissors structure, as discussed in the previous section. The unit scissors model with the deck is shown in

This section describes the ultimate strength test for deck and its results in order to check the safety of the aluminum alloy deck under vehicle loading.

The aluminum alloy deck with a vehicle traveling is shown in

The aluminum alloy deck was constructed of a steel pipe of φ = 20 mm which was pin-fixed at both ends. The loading plate, which supports a tire contact area, uses 175 mm × 175 mm steel plate and the rubber board according to guidelines of Eurocode for bridge design.

The load-displacement curve at the loading point is shown in

The stress distribution in the central section corresponding to the force of P = 4.5 kN, 5.0 kN, and 5.5 kN is depicted in _{y} = ±110 MPa shows the yield stress of the material A-6063. From _{max} = 28.7 kNm in the central part of the aluminum deck, and this value corresponds to yielded bending moment for the deck.

This section describes the outlines and results of the vehicles loading test using MB1.0. Moreover, experimental results are compared with theory of scissors and FE analysis.

Two kinds of vehicles, Honda STREET and Nissan AD van, were used for the vehicles loading test. The

STREET’s (Full length × full width × overall height) was (3195 mm × 1395 mm × 1870 mm), while the AD van’s (Full length × full width × overall height) was (4370 mm × 1895 mm × 1510 mm). The wheel base of the STREET was 1900 mm and the total weight of the STREET including the driver is 9.6 kN distributed 5.2 kN of front axis and 4.4 kN of rear axis. The wheel base of AD van was 2535 mm and the total weight of the AD van including the driver is 13.8 kN distributed 7.5 kN of front axis and 6.3 kN of rear axis.

From

From

The points which became clear from this research are followed as:

Through the bending test, it was proved that the load-carrying capacity of the aluminum deck was sufficient for vehicles passing over.

In the static loading experiment of MB1.0 it was found that measured strains caused by vehicles loading are consistent with previously obtained analytical values (difference less than 10%).

With a maximum loading weight of 13.8 kN, the main member and decks are within allowable stress, and it turned out that the vehicles about 10 kN could pass safely on MB1.0.

We appreciated that all manufacture of cradles were supported by Star Light Metal Industry Co., Ltd., Akashin Corporation, Sankyotateyama Inc., Japan Construction Method and Machinery Research Institute and FSC Co. Ltd which is supported by a grant.

Ichiro Ario,Yuki Chikahiro, (2015) A New Type of Bridge, Mobilebridge® to Super-Quickly Recover a Bridge. World Journal of Engineering and Technology,03,170-176. doi: 10.4236/wjet.2015.33C025