An experimental study on the design method of a real-sized Mobile Bridge for a moving vehicle

Transcription

1 Mobile and Rapidly ssembled Structures I 93 n experimental study on te design metod of a real-sized Mobile ridge for a moving veicle Y. ikairo, I. rio, M. Nakazawa, S. Ono 3, J. olnicki-szulc 4, P. Pawlowski 4 &. Graczykowski 4 epartment of ivil and nvironmental ngineering, irosima University, Japan epartment of ivil and nvironmental ngineering, Tooku Gakuin University, Japan 3 Japan onstruction Metod and Macinery Researc Institute, Japan 4 epartment of Intelligent Tecnologies, Institute of Fundamental Tecnological Researc, Poland bstract Many natural disasters can cause not only a critical situation in local resident s lives and facilities but also significant damage to te economy. ltoug we ave to undertake quick rescue actions for tese damages, tere are many recovery problems, due to te occurrence of secondary disasters at eac rescue worksite. Looking at previous studies of deployable structures and te control regulation of te multi-folding micro-structure, we propose a new type of foldable bridge, wit a scissors structure called te Mobile ridge TM. In tis paper we discuss veicles passing a test on a real-scaled Mobile ridge, so as to evaluate its mecanical caracteristics and application limits. Moreover, we verify te compatibility amongst te results of te analysis, te calculations and te experimental values by means of a teoretical approac and metod. From tese results, if design of Mobile ridge is simplified, we understood tat it is sufficient to treat te load as equivalent nodal force applying te pins witout te stiffness of te deck.. Keywords: Mobile ridge TM, scissors type of emergency bridge, aluminium alloy materials, veicle loading test. doi:.495/mr48

2 94 Mobile and Rapidly ssembled Structures I Introduction In recent years, te world as seen many kinds of natural disasters, suc as eartquakes, floods and tsunamis. In te case tat we are investigating a very large flood along several brances of te Yamakuni River in Kyusu, nortern Japan, a lot of areas suffered from bridge and road damage. Terefore, te designers or engineers of bridges ave to consider ow to rebuild a damaged infrastructure and ow to build a new type of rescue system, wic can be implemented quickly, because rescue time is very important wen trying to save lives after an emergency. From a previous study on te optimization structure and deployable structure of bridges [ 4], we propose a new type of emergency bridge by te name of te Mobile ridge TM (M), wic can be expanded and stored for concrete disaster recovery system [5]. ltoug te upper and lower cord members of a bridge are main elements, wic resist te bending moment in a general truss bridge, te M can be built using a scissors mecanism for a bridge formation and resist sectional force in spite of lacking te one member [6 9]. scissors structure, wic is applied to te structural form of an M, is typically a deployable structure tat as good storage and conveyance performance and is tusly named because its structural form combines te member in te sape of scissors. Te joint tat connects te member of scissors is named a pin-junction, wic is joined by a flexible inge and te pin joining section is called a pivot, wic exists in te central portion of a scissors member intersect. Te advantages of tis structure are as follows: ) ven if tere are few members for te construction of te scissor structure, its deployment and storage can be performed quickly, ) its assembly, conveyance, and demolition is easy and 3) because te scissors structure can deploy and store all units by one control force, if te flexibility increases, its deployment performance is igly efficient and more useful. In tis paper, we discuss te veicles passing a test on te real-scaled Mobile ridge (called M.) in order to evaluate its mecanical caracteristics and application limits for scissors type of bridge. Moreover, we verify te compatibility amongst te results of te analysis, te calculations and te experimental values by means of a teoretical approac and metod. Outline of te real-scaled Mobile bridge Te scematic view of te experimental, two-unit scissors model for a real-scaled mobile bridge (M.) on wic veicles can load is sown in Figure. Wen deployment starts, te member gradually slopes and te span is extended. Moreover, because te deck is sated in M., te deck works wit te member as deployment progresses. Following tis, te scissors deployment angle is at an angle of 6 degrees. Te total lengt of te span is 7. m and te eigt is. m. Te total weigt, considering te structural parts, suc as te main member, te saft and te pin of te bridge, is 8.4 kn. Te aluminum alloy component of te tree-room ollow section, wic uses 6N material, is

3 Mobile and Rapidly ssembled Structures I 95 used for te main member, te surrender bending moment is. knm and te ultimate bending strengt is 39.9 knm. Te deck on wic te veicles travel (ereafter called te aluminum alloy deck) consists of an 663 extrusion section. Only a portion of te aluminum alloy deck was constructed te section upon wic te weel loads act because of weigt saving. Moreover, te deployment action aims at sortening te construction time by uniting and interlocking te scissors member and te aluminum alloy deck. Te 6N material is = 6. GPa, σ = 98.8 MPa and σ y = 8. MPa, wile te 663 material is = 68. GPa, σ = 5. MPa and σ y =. MPa. Store Under developing Finis construction 6.m 7.m Figure : Te stretcing beavior of M.. 3 Teory of scissors mecanism 3. Te mecanics of a unit scissors structure Free ody iagram (called F) for a unit of scissors structure is sown in Figure. Wen te lengt of te members is L and te angle of inclination is θ, te sectional lengt λ and te eigt are L s in θ = λ and L cosθ =. So, te construction and storage of suc a structure can be sown by te angle θ. Tis unit scissors structure can be designed by using te equation of equilibrium. Te equation of equilibrium concerning eac of te external forces and is given as te following two expressions;, () () Looking at te members and, te intersect is sown in Figure 3. It is calculated tat te two equilibrium equations of moments occur at Point, as in te following; Member of : M, (3) Member of : M (4)

4 Figure : F of a unit scissors structure. Figure 3: ontinuity conditions of eac member. Let us now consider te case of te cantilever model, wic as a pinned support for point and point. It is possible to use a matrix by arranging te four calculated equilibrium equations eqn () eqn (4), as sown in eqn (5); (5) Similarly, we can get equilibrium as eqn(6) in te simple beam model, wic as a pinned support for point and point ; (6) From te above results, unknown reaction forces can be obtained by considering te loading condition and te boundary condition for tese. λ θ L 96 Mobile and Rapidly ssembled Structures I

5 Mobile and Rapidly ssembled Structures I Mecanics of a scissors structure in te consideration of deck Next, let us consider te mecanical model wen adding te deck to te fundamental teory of te scissors structure, as discussed in te previous section. Te unit scissors model wit te deck is sown in Fig. 4(a), and te F, wic is made of te unit scissors and eac independent deck, is sown in te Fig. 4(b). Figure 4(a) sows te wole of te structure wit a moving load, suc as a veicle. veicle passes over te deck between nodes and. ccording to te weel load, te reaction forces on te supports occur in te deck, as sown in Figure 4(b). Te reaction force tat arose in te deck is transmitted to te main member of a scissors unit, as an external force, P and P. ecause te weel load transmitted from te deck canges wit weel positions, it is tougt tat te stress distribution, wic occurs in te scissors member and te deck, canges depending on te position of te veicles. θ P P P P (a) (b) Figure 4: F of a unit scissors structure wit deck. (a) Wole system, (b) F of te deck. 4 xperimental evaluation for te load-carrying capacity of te aluminium alloy deck Tis section describes te bending fracture experiment and its results in order to ceck for te safety of te aluminum alloy deck under veicle loading. 4. Outline of te aluminum alloy deck Figure 5 sows te aluminum alloy deck wit a veicle traveling. Te lengt of te deck is 3 mm wit a widt of 5 mm. Te quality of te material is 663-T5 and is formed by welding two types of ollow extrusions togeter; one wit a widt of mm and te oter wit a widt of mm. Te weigt of one panel is 49N. 4. xperimental conditions Te aluminum alloy deck was created by setting a steel pipe of φ = mm to bot ends of te pin fixing part. Te loading plate, wic supposes a tire contact area, uses a 75 mm 75 mm steel plate and a rubber board for prevention, consulting te urocode for bridge designs.

6 98 Mobile and Rapidly ssembled Structures I Welding bead Pitc of ead Loading Plate ross-section sape ross-section ross-section 4.3 xperimental results Figure 5: Scematic diagram of te deck. Te load-displacement curve at te loading point is sown in Figure 6. Te orizontal axis sows te displacement of te ead part of te loading macine and te vertical axis sows te increment of te load. Until P = kn, te load is increased by. kn and after P = kn, te load increases by kn until P = 4 kn. fter observing P = 4 kn, te load was removed and te residual displacement and strain on te aluminum alloy deck was cecked. Ten, te displacement was increased by δ = mm. Te aluminum alloy deck lost its bearing force, sowing a maximum load of 5. kn and te experiment ended. Figure 6: Load displacement curve. 4.4 istribution of te stress in te central cross-section position Te stress distribution in te central section is depicted in Figure 7 at te times of P = 4.5 kn, 5. kn and 5.5 kn. Te stress values (MPa) are sown on te vertical axis and te distances (mm) from te neutral axis are sown on te orizontal axis. Moreover, te line of σ y = ± MPa sows te yield stress

7 Mobile and Rapidly ssembled Structures I 99 of te quality of te material From Figure 7, we can see tat te undersurface first surrendered at te time of P = 5. kn. So, te serviceability limits for te load of te deck was as muc as 5. kn. t tis time, te maximum bending moment was M max = 8.7 knm in te central part of te aluminum deck and tis value yielded te bending moment for te deck. Figure 7: istribution of te strain values at central section of te deck. 5 Te veicle loading test using M. In tis section, te outlines and results of te veicles loading test using M. are described. Moreover, te experimental results are compared wit an equilibrium elastic teory of scissors and F analysis. 5. eicles outline Two kinds of veicles a onda STRT and a Nissan van were used for te veicles loading test. Te STRT s (full lengt*full widt*overall eigt) was (395 mm*395 mm*87 mm), wile te van s (full lengt*full widt*overall eigt) was (437 mm*895 mm*5 mm). Te weel base of te STRT was 9mm and te total weigt of te STRT concluding a driver is 9.6kN distributed 5.kN of front axial and 4.4kN of rear axial. Te weel base of van was 535mm and te total weigt of te van concluding a driver is 3.8kN distributed 7.5kN of front axial and 6.3kN of rear axial. 5. eicles stop position and loading condition From Table, it can be seen tat te measurement was performed five times. Wen te front weel, te axle (tat is defined ere as te intermediate part of te front and te rear weel) and te rear weel came to a specific point and stopped and te value of te strain was measured. Te stop positions were at te center of te deck for te first unit scissors and te central part of M.. Two cases of loads were used, as seen in Table. One case depicts te STRT,

8 Mobile and Rapidly ssembled Structures I wic is a ligt veicle and te oter case depicts te van, wic is a standard-sized car. In loading ase, te additional weigt was loaded from ase te backseat of te veicles and ran. Table : Loading conditions. Load case Type of Loading condition(kn) veicle Total Front axis Rear axis STRT an Table : eicles stop positions. ase eicle stop position Front weel enter of first slab Weel axis enter of first slab Front weel enter of M. Weel axis enter of M. Rear weel enter of M. 5.3 erification of te frame analysis We analyzed M. by utodesk Inventor. Te analysis was possible by using internal programming (NSYS) wic was interlocked in te. To identify all te elements, a beam element was used. Te analysis was done by paying attention to te Pattern, in wic te maximum strain occurred wit te veicles in te stop position. Te analysis models are sown in Figure 8. Te dead load consists of te main member, te saft, and te deck. Figure 8 (a) is te strict model considering te deck and Figure 8 (b) is te simple model not considering te deck. Te strict model made te weel load on te deck, wic acted on te weel position after veicle loading acted on te floor version, as sown in Figure 8 (a). Te simple model made te weel load on te pin, wose member intersects in te way of an equivalent nodal force, as seen in Figure 8 (b). Te live load, as depicted by te red arrow acts according to te weel load and te yellow arrow depicts te equivalent nodal force. s a boundary condition, te saft part of bot ends is fixed into te pin fixation in a simple beam state. P3 P P (a) (b) Figure 8: analytical model: (a) Strict model, (b) simple model.

9 Mobile and Rapidly ssembled Structures I 5.4 Results of te experiment Figure 9 (a) and (b) sows te strain distribution wen te veicle was loaded in te center of te bridge. Figure 9 (a) portrays a member, wic stands in a row like a type of mountain from te supports and Figure 9 (b) pays attention to te member, wic is in a free-state and te target is colored in red. Moreover, te blue mark in te figure sows te position of te strain gage. It can be seen tat te experimental and analytical values are less tan te allowance strain (= με) for loading veicles from up until 3.3 kn. maximum strain of about 5 με occurred in te member intersection part, so tere was a safety ratio of nearly double tat of te yield strain. (a) (b) Figure 9: istribution of strain in te central M.: (a) Member ends-supports, (b) member ends-free. From Fig. 9 (a) we can see tat te maximum strain was measured at 5 με by te circumference of te pivot of te first unit and te minimum strain was measured by te circumference of te pivot of te second unit.. ecause te distribution of te strain almost equaled in te compression and te tension area, it turned out tat te member s influence on te bending moment was great. ltoug accuracy ad variations in comparison wit te analytical results, te maximum value was distributed witin %. Fig. 9 (b) sows tat ardly any strain from te member occurred around ± με, wic was in an end-free state. It turned out tat te analytical results also sowed te same tendency and te bending moment did not act on te member, but te strain rose wit a little axial tension.

10 Mobile and Rapidly ssembled Structures I 6 onclusion Te points wic became clear from tis researc are followed as: ) Troug te bending test, it was proven tat te load-carrying capacity of an aluminum deck is sufficient for veicles to pass over it. ) In te static loading experiment, it was found tat te strain cange arose in M. at te time of te veicles loading and it was consistent wit an analytical value of less tan %. 3) Wit a maximum loading weigt of 3.8 kn, te main member and decks are witin allowable stress, and it turned out tat te veicles of about kn could pass safely. cknowledgements Tis researc was supported for r. I. rio by a Grant-in-id-Scientific- Researc ase Researc () of JSPS in 3. We appreciated tat all experiments were supported by Japan onstruction Metod and Macinery Researc Institute. Moreover, we appreciate tat a sample of te aluminum materials were offered by Star Ligt Metal Industry o., Ltd. in Japan. References [] J. olnicki-szulc, P. Pawlowski and M. Wiklo: ig-performance impact absorbing materials te concept design tools and applications, Smart Materials and Structures: Int. J. Non-Linear Mecanics, pp , 3. [] I. rio and. Watson: Structural Stability of Multi-Folding Structures wit ontact Problem: Int. J. Non-Linear Mecanics, ol. 34 ( ), pp [3] I. rio and M. Nakazawa: Nonlinear ynamics beavior of Multi-Folding Microstructure Systems based on Origami Skill: Int. J. Non-Linear Mecanics, ol. 45(4), pp ,. [4] I. rio and.. Kim: Micell Problem for te Stiffness Formation of Structural esign in 3 imensional Space: Proc. of Optimizational Symposium in JSM, 7, pp , 6. [5] I. rio: Structure wit te expanding and folding equipment as a patent (No ), 6. [6] I. rio, Y. Tanaka, M. Nakazawa, Y. Furukawa and Y. ikairo: Researc and development of te ig-efficiently foldable structure (nalysis), Proc. of Space Structure and Material Symposium in JX, ol. 5, pp. 4 7, 9, (in Japanese). [7] Y. Tanaka, I. rio, M. Nakazawa, Y. Furukawa and Y. ikairo: Researc and development of te ig-efficiently foldable structure (xperiment), Proc. of Space Structure and Material Symposium in JX, ol. 5 pp. 8, 9 (in Japanese).

11 Mobile and Rapidly ssembled Structures I 3 [8] I. rio, Y. Tanaka, M. Nakazawa, Y. Furukawa and Y. ikairo, evelopment of te prototype of a new emergency bridge based on te concept of optimized structure, Journal of Structural ngineering, JS, ol. 64, pp., (in Japanese). [9] I. rio, Y. Furukawa, Y. Tanaka, Y. ikairo, S. Matumoto, M. Nakazawa, I. Tanikura and S. Ono: ynamic ibration of a Prototype eployable ridge based on MFM, Te proceedings of te 9t World ongress on omputational Mecanics and 4t sian Pacific ongress on omputational Mecanics WM/POM,,. [] M. Nakazawa and I. rio: Mecanical Property of eployable mergency ridge ased on te Scissors Structures, Journal of safety problems, ol. 5 pp , (in Japanese).