International Conference Timber Bridges

Proceedings of the International Conference Timber Bridges ICTB2010 Lillehammer, Norway September 12 -15, 2010 Editors: Professor Kjell A. Malo Ch...
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Proceedings of the

International Conference Timber Bridges ICTB2010

Lillehammer, Norway September 12 -15, 2010

Editors: Professor Kjell A. Malo Chief Engineer Otto Kleppe Chief Engineer Tormod Dyken

Organizers: Norwegian Public Road Administration NTNU, Norwegian University of Science and Technology NTI, Norsk Treteknisk Institutt Innovation Norway

Secretariat: Norwegian Public Road Administration P.O Box 8142 Dep NO-0033 Oslo, Norway www.vegvesen.no

© ICTB 2010 & Tapir Academic Press, Trondheim 2010

ISBN 978-82-519-2680-5

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Preface Over the past twenty years, timber bridge construction has gathered headway in many countries. Research in the area has produced significant results; new materials and connections have been developed and various structural systems have been explored. New developments have been presented in journals and at general timber construction conferences. The time was now ripe for a specialized international conference on timber bridges to present the state of the art. In Norway, the ready availability of timber and the tradition of utilizing timber in houses and other structures make it natural to consider timber an adequate construction material for bridges with spans of up to 100 meters or even more. Today, there are many timber bridges in Norway – both road and pedestrian bridges. Since 1995, the Norwegian Public Roads Administration has built more than 100 timber bridges with spans up to 70 meters. The main objective of the conference ICTB2010 at Lillehammer was to showcase and discuss the state of the art in timber bridge technology. The conference topics were: • Design aspects • Environmental aspects • Historical bridges • Protection and durability • Monitoring • Timber bridge aesthetics • Components, connections and detailing • Pedestrian bridge projects • Bridge decks • Composite bridges The primary emphasis of the conference was on the design of durable, environmentally friendly and cost-efficient timber bridges. Our hope is that ICTB 2010 can serve as a source of inspiration for designers, researchers, architects and others, working within the field of timber bridges.

Lillehammer, September 2010.

On behalf of the facilitating organizations, Børre Stensvold Bridge Director, Norwegian Public Roads Administration Conference Chair.

International Scientific Committee Professor em. Heinrich Kreuzinger, Technische Universität München, Germany Professor Kurt Schwaner, Biberach University of Applied Sciences, Germany Professor Gerhard Schickhofer, Graz University of Technology, Austria Professor em. Aarne Jutila, Helsinki University of Technology, Finland Professor Robert Kliger, Chalmers University of Technology, Sweden Research Engineer James Wacker, USDA Forest Products Laboratory, USA Professor Kjell Arne Malo, Norwegian University of Science and Technology, NTNU, Norway Amanuensis Nils Ivar Bovim, The Norwegian University of Life Sciences, Norway

Steering Committee Bridge director Børre Stensvold - Conference Chair, Norwegian Public Roads Administration Mr Erik Aasheim, Conference Co-Chair, Norsk Treteknisk Institutt (NTI) Professor Kjell Arne Malo, Programme Co-Chair, Norwegian University of Science and Technology, NTNU Mr Otto Kleppe, Programme Chair, Norwegian Public Roads Administration

Organising Committee Mr Otto Kleppe, Chair Norwegian Public Roads Administration Mr Nils Ivar Bovim, The Norwegian University of Life Sciences Mr Rune B. Abrahamsen, Sweco Norway Mr Åge Holmestad, Moelven Limtre AS Professor Kjell Arne Malo, Norwegian University of Science and Technology, NTNU Mr Erik Aasheim, Norsk Treteknisk Institutt (NTI) Mr Trond Arne Stensby Norwegian Public Roads Administration Mr Tormod Dyken Norwegian Public Roads Administration

Contents Key note lecture Kurt Schwaner, Germany: Timber Bridges - different countries, different approaches .....................

1-20

Design aspects Part I Michael Flach, Austria: How to design timber bridges ...................................................................... Per Kr. Ekeberg, Norway: Technical concepts for long span timber bridges .................................... Hauke Kepp, Norway: Thermal actions on timber bridges ................................................................ Kolbein Bell, Norway: Structural system for glulam arch bridges ....................................................

21-28 29-36 37-48 49-66

Design aspects Part II João Nuno Amado Rodrigues, Portugal: Use of composite timber-concrete bridges solutions in Portugal ........................................................ 67-78 Jarle Svanæs, Norway: Environmental timber bridges – verification of material properties of Kebony modified wood ......................................................... 79-88 Hilde Rannem Isaksen, Norway: Construction cost of Timber Bridges in Norway –A comparison with Steel and Concrete ............................................................................................. 89-98 Ove Solheim, Norway: New 4-lane Mjoesbridge in timber? ............................................................. 99-106

Environmental aspects Johanne Hammervold, Norway: Environmental analysis of bridges in a life cycle perspective ........ 107-118 Jarle Svanæs, Norway: Environmental friendly timber bridges – Environmental improvement through product development .............................................................. 119-122

Historical Bridges Tsuneo Igarashi, Japan: The 62nd reconstruction of a traditional wood bridge ................................ 123-130 Guillermo Iñiguez-Gonzáles, Spain: Remarkable ancient timber bridges up to the 1850´s. Part I: general review........................................................................................................................... 131-138 Miguel C. Fernández-Cabo, Spain: Remarkable ancient timber bridges up to the 1850´s. Part II: case studies and breakthroughs................................................................................................ 139-156

Protection and Durability Otto Kleppe, Norway: Durability of Norwegian timber bridges ....................................................... Anna Pousette, Sweden: Outdoor tests of timber beams and columns .............................................. Masahiko Karube, Japan: Report of the collapsed wooden bridges in Japan .................................... Elisabet Michelson, Norway: Polyurea based bridge membrane on wooden bridges .......................

157-168 169-178 179-194 195-204

Monitoring Thomas Tannert: Structural health monitoring of timber bridges ...................................................... 205-212 Anders Gustavsson, Sweden: Health Monitoring of timber bridges .................................................. 213-222 Tormod Dyken, Norway: Monitoring the moisture content of timber bridges .................................. 223-236

Antti Karjalainen, Finland: Bridge Information Modelling (BIM) and Laser Scanning In Renovation Design, Case Pyhäjoki Bridge ..................................................................................... 237-242 Jim Wacker, USA: Development of a Smart Timber Bridge Girder with Fiber Optic Sensors ......... 243-252

Timber Bridge Aesthetics Richard J. Dietrich, Germany: Six timber bridges of special interest ................................................ 253-258 Yngve Aartun, Norway: Timber Bridge Aesthetics –Design and function (+ tradition) .................... 259-266 Bernt Jakobsen, Norway: Spectacular Wooden Truss Bridges as Traffic Safety Enhancing Measures ....................................... 267-276

Components, Connections and Detailing Lars Bergh, Norway: Construction of timber bridges by prestressing prefabricated segments ......... 277-280 Bjørn A. Lund and Matteo Pezzucchi, Norway: Development of a new barrier system for stress laminated timber road bridge decks ........................ 281-296 Kjell Arne Malo, Norway: On Connections for Timber Bridges ........................................................ 297-312 Abdy Kermani, United Kingdom: Developments in stress-laminated arch construction for footbridges ................................................. 313-320

Pedestrian Bridge Projects Rolf Broennimann, Switzerland: Design, construction and monitoring of a bowstring arch bridge made exclusively of timber, CFRP and GFRP ................................................................. 321-328 José L. Ferández-Cabo, Spain: Construction aspects of a 19.2 m Timber Truss cantilevered view walkway in Vitoria, Spain ...................................................................................... 329-334 Anssi Laaksonen, Finland: Malminmaki Pedestrian Overpass .......................................................... 335-340 Julio Vivas, Spain: Design and installation of a covered timber footbridge over the A8 motorway in Bilbao, Spain .................................................................................................................. 341-350

Bridge decks Mats Ekevad, Sweden: Prestressed Timber Bridges - Simulations and experiments of slip .................................................... 351-358 Roberto Crocetti, Sweden: Anchorage systems to reduce the loss of pre-stress in stress-laminated timber bridges ..................... 359-370 Rune B. Abrahamsen, Norway: Bridge deck rehabilitation using cross-laminated timber .................................................................... 371-382

Composite bridges Aarne Jutila, Finland: Wood Concrete Composite Bridges – Finnish Speciality in the Nordic Countries ............................. 383-392 Jeno Balogh, USA: Testing of Wood-Concrete Composite Beams with Shear Key Detail ................................................ 393-398 Leander A. Bathon, Germany: Performance of single span wood concrete - composite bridges under dynamic loading .................. 399-402

International Conference on Timber Bridges (ITCB 2010)

Report of the collapsed wooden bridges in Japan 1988 Bachelor, and 1990 Master of Architectural Eng., Shinshu University 1990-1991 Assistant of Shinshu University 1994 Doctor of Eng., Shinshu University 1994- Researcher of FFPRI 1999 Senior Researcher 2006- Team leader

Masahiko KARUBE Team Leader, Evaluation Team of Connecting Performance Dept. of Wood Engineering (FFPRI) Tsukuba, JAPAN [email protected]

Summary We will reports the collapse of two wooden bridges. Both were made in 1990, and placed in west part of Japan. The Bongossi Bridge was built in March 1990 in south-west part of Ehime prefecture of Japan. And which was made with Bongossi (Lophia alata; other name: Azobe, Ekki) and stainless dowel fasteners. The Bongossi wood was well known by its high durability, but the bridge collapsed by its decay with white rot fungi and which was collapsed in September 1999 spontaneously. The destructive loaded bridge which was made with Douglas-fir was built in May 1990 in east part of Hiroshima prefecture of Japan. Because of the deterioration of some members, this 36m pedestrian truss bridge was replaced by steel bridge in December 2003 without the verification of residual strength performance. In March 2007, we rebuilt with original members and fasteners and after curing for the 15 month, we carried out the loading experiment in June 2008. Keywords: collapse, spontaneously broken, destructive loading, Bongossi, Douglas-fir, white rot fungi, deterioration, residual strength, failure prediction.

1.

Introduction

In September 1999, a wooden bridge was felt down. That was the first experience of collapse in Japan which was made by recent design method. We conduct a series of observation and survey of this bridge. Then, we found internal decay in almost of wooden members which were made of very durable wood Bongossi. In December 2003, a wooden bridge was removed without any verification of structural safety, and replaced by steel one just looks like former wooden bridge. The deterioration of some of the member of this wooden bridge was recognized in 2000, two years before this deconstruction. We collect all of wooden members, connectors and fasteners. And we reconstruct the bridge in research field in 2007. After 15 months curing, we conduct a destructive loaded in 2008. In this paper, I will introduce these two cases of collapsed bridges, and the possibility of detection of defects. According to the results of investigation and experiment, I will discuss the evaluation and design feedback for wooden structures. The facts will give a lot of suggestions to make good and long lasting wooden structures.

2.

Reports of the collapsed wooden bridge

2.1 CASE 1: A bridge spontaneously broken The wooden bridge fell in September, 1999. That was the pony truss form made of Bongossi, placed in Ehime Prefecture (south-western part of shikoku island Japan). The fall of the wooden bridge by a modern design doesn't have the example in Japan. And there is no report but a lot of existing wooden bridges of the same form either [1] [2].

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and not deteriorated. Each members of lower chord decayed over 80% in its cross section because it was folded by added joint members (see Fig. 4). Inspecting of this bridge, all the joint was made with double or single wood spliced joint. And the inner part of this spliced area rot terribly, especially the big areas of upper and lower chord joint, the connection of post to chord, and the connection of web member to chord. Also some of the member was rotten severely in the part between connections (see Fig. 5). There were many fruit body of fungi at several point of connection gaps and middle of members. The internal decayed materials were softened which seemed like sponge or damped cereal. The other members of bridge were so on. (See Fig. 6).

Fig. 4 Joint of lower chord: the rupture starting point and its cut section

Fig. 5 Connection of post to chord and its detail

Fig. 6 Cross cut section of lower chord Fruit body of fungi (on right)

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2.1.3 Verification of species The samples picked from the member of the rupture starting point. The species was recognized to Bongossi (The scientific name: Lophia alata Banks ex Gaertn. Bongossi is name of Germany. Azobe in Britain, Ekki in France.) by Tissue laboratory of Forestry and Forest Products Research Institute. The density of samples was 1.07g/cm3. According to the document [4], it was worth average value of Bongossi (Min: 0.95 – Ave.: 1.06 – Max: 1.10), decay durability is categorized to secondly durable class from five ranks, and it is suitable for water and marine structure. But also the document says the individual difference is large. 2.1.4 Verification of fungus From the picked samples, he decay fungi that causes the collapse was recognized to white rot fungi named Shiisarunokoshikake (The scientific name: Loweporus tephroporus) by Yasuhisa ABE who was the head of Decay disease damage laboratory of Forestry and Forest Products Research Institute. According to the document [5], the fungi exist widely and are known generally as hardwood decay fungi in Japan. And also the fungi have not special degradation power. 2.1.5 Investigations In this park, there were another 15.4m span bridges (Bridge No.1 and No.2) which are the same pony truss form to the collapsed wooden bridge (No.4). These two bridges (No.1 and No.2) were removed until the end of March 2010 because of serious internal decay as it cannot to support itself. To verify the soundness of these rest bridges, only a non-destructive investigation was conducted to Bridge No.1 and No.2. A preliminary investigation was done to arrange the fact correctly on September 21, 1999 and the detailed investigation was done on October 21 of the same year. Table 1 shows the investigation items of detailed investigation. In a preliminary investigation, the above-mentioned details until wooden bridge collapse and the situation were understood. In a continuing detailed investigation, the technique and applicability were examined whether the internal decay was discovered and diagnosed or not. Each metrology was verified by cutting the measured part actually and observing the presence of the decay and the degree. Table 1 Investigation Items INVESTIGATION Decay degree Non-Destructive observation Destructive assessment (Local destruction included) Structural safety

TECHNIQUE Human eye observation Slapping sound judgment Elastic repulsion power (SCHMIDT hammer) Ultrasonic wave transmission time measurement Pin resistance to penetration (PILODYN) Wood screw torque method Borehole camera observation Fracture surface and cut section observation Loading test

APPLICATION existence bridge and fall part

fall part existence bridge

2.1.6 Situation of fall Judging from the results of investigation, the scenario of wooden bridge collapse is divided into the following three stages. 1) Stage of decay : Damping rains at the internal surfaces of splice joint, the open cracks and/or checks of upper face of members. Decay beginning in damped area. Decay progresses into internal area although the face is in healthy state. Mechanical property decreases at decayed position. 2) Material rupture : Strength of the members falls below the demand design strength at the point of pre-drilled dowel-pin and bolt holes, and deflected complicated grains. The shear failure and the exfoliation along the boundary edge of the decay part. Some of the wood fiber breaks in tension. 3) Whole collapse : Lower chord breaks and apart. Upper chord of other side of the bridge buckled locally at the joint. The other lower chord breaks. Upper chords break in bending.

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2.2

CASE 2: A bridge destructive loaded

We conducted a destructive loading test of the existing truss wooden bridge in June 2008. This pedestrian bridge had been actually used for 13 years in prefectural nature park in the east of Hiroshima prefecture. The purpose of this experiment was to know the residual strength performance of this deteriorated wooden bridge, and possibility of failure prediction [6]. 2.2.1 Bridge as it was 2nd span

1st span ×12=36.3m 3m×

3m×6=18.3m

Middle ground

Down-stream

Up-stream

Fig. 7 ‘Kappa-Bashi’ bridge at Hiroshima Prefectural Yamanokyo Natural Park (2003/11/06, composite of 4 pictures) The destroyed wooden bridge is the first span of the through truss pedestrian bridge named ‘kappabashi’ built in May 1990 in Hiroshima Prefectural Yamanokyo Natural Park. It consisted of two spans arranged from the stream shape, the first span length was 36.3m and the second was 18.3m (shown in Fig. 7). Both spans were 2.7m height, and 2.3m effective width. All the wooden members of this bridge were made by Douglas-fir Glulam and treated with natural antiseptic paints, and the width was 220mm. The upper and lower cord depth was 262mm; diagonal member depth was 170mm except both truss ends was 228mm.The load bearing design was done by 350kgf/m2 as sidewalk live load, and 800kgf/m3 as dead load in accordance of specifications for roadway bridges in Japan (1980). The cord-to-diagonal member connections were made of bolted double steel side plate made from SS400 (JIS G 3101). [7] The deterioration of the wooden member was recognized in around 2000. In December 2003, the wooden bridge served in 13 years was replaced by quite similar shaped steel through truss bridge consisted by rectangular steel pipe covered with resin created wood like surface. The bridge had removed in December 2003 because of serious deterioration found in several wooden members [8]. And it had replaced by steel one because of reliability shortage to local government officer [9]. We collected all of the wooden members, steel connectors and fasteners and stored to indoor-warehouse after non-destruct evaluation of wooden members [10]. 2.2.2 Disassemble and reconstruction Before the de-construction, we conducted transfer experiment to move the 2nd span (18.3m) to the riverbed of middle ground. This experiment was a simulation of bridge inspection. Moving to a ground makes easier and safe to access and check of wooden members and its part. Because of the load capacity of lift was limited; the longer wooden bridges were divided in length at the upper and lower cord joint. After moving to the riverbed of middle ground, each bridge sections were politely disassembled to wooden members, steel connectors and fasteners [11]. In March 2007, we had rebuilt the 1st span (36.3m) with only the original members and fasteners, with assembling all parts to its original position. The abutments were made temporary in research field of Forestry Research Centre of Hiroshima Prefectural Technology Research Institute. After then, we monitored its weight, shape, and some of the specific values of wood members with nondestructive testing method [12]. After curing for the 15 month, we carried out the destructive loading experiment in June 2008.

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2.2.3 Destructive loading We had the destructive loading to reconstructed 36.3m bridge on June 18, 2008. Fig. 8 is an appearance immediately after collapse [13]. 130 earth and sand packed bags were prepared which was a cylindrical shape, its diameter was about 900mm, weigh about 320kg per a bag, total 400kN dead load. The bags were loaded on the deck at the half length of the bridge length in the middle of span passing through the lateral bracing between upper-cords (see Fig. 9).

Fig. 8 Appearance immediately after collapse (Down-stream direction is forward)

The bags were loaded as possible to spread evenly in the range. The position and the order are shown in right of Fig. 10. The dead load of whole structure was 218.4kN. When 12 bags were loaded, we checked whole system of loading and measuring taking a while. When 26 bags (94.4kN) loaded, we planned to have a rest, but the primary break was happened at the lower-cord of up-stream side truss in tension where there was recognized severe deterioration before loading (See Fig. 12).

Fig. 9 Scheme of earth and sand bag loading

After primary break, we continued loading as if the bridge was slanted laterally. Though we only could to load to down-stream side. When 42 bags loaded, there was no space to place the bag on the deck. We continued loading to place the bag on the bags. When the 53 bags (189.7kN) were loaded, secondary break was happened on upper-cord of down-stream side truss in compression, and the bridge was collapsed and felt down on the ground (See Fig. 13).

Fig. 10 Bag Loading position and its order

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3.

Results and Discussion

We applied many kinds of methodology for investigation and evaluation of the state of wooden bridges. These are some of the result divided into two categories; for detection and failure prediction, and for feedback to plan and design. 3.1 Detection and failure prediction There are two kinds of evaluations, relative and absolute. If we have a lot of reference, we can make some of the criteria and/or threshold value to detect the defects. That is a kind of absolute evaluation. But we do not have sufficient references and results, I will try to find the defects or worst point of the structural performance from a distribution map and histograms. We can get a value from some of evaluation methodology. The value might represent a state of point. Series of this point data makes a state of along a line, some of an area, surface, volume, section, part of member and whole structure. 3.1.1 Human eye observation and Slapping sound judgment In many observation and survey, human eye observation was widely done by many persons because of it’s very handily property among the number of inspection techniques. However, because the judgment value is subjective, it is not sure to become an absolute index. So the judged decay degrees have not a uniform judging scale from their personality and trained skills. The slapping sound judgment is also in the same situation. The result was not able to be said with an objective value. But also the results were very informative to other investigations 3.1.2 Elastic repulsion power A well known non-destructive strength evaluation method was applied to the CASE 1, some of members of fall part. SCHMIDT hammer is widely used in concrete structures to evaluate the elastic repulsion power [15]. But, an internal decay like this collapsed bridge member was not able to be detected though this method. 3.1.3 Pin resistance to penetration PILODYN is a one of the well known method of wood health indicator [16]. This handheld instrument measures resistance strength of pin penetration. External or surface deterioration will be detected as a depth of pin penetration with constant energy of compressed spring in the instrument. However, it was not suitable for detection in this situation of internal decayed section though the surface was comparatively healthy and Bongossi is too hard to penetrate in healthy state. 3.1.4 Ultrasonic wave transmission time measurement PUNDIT (Portable Ultrasonic Non-destructive Digital Indicating Tester, CNS Farnell Inc.) is measuring instrument that measures the time of the ultrasonic wave transmission, and also widely used non-destructive testing method in concrete structures. When this inspection technique was applied to the location where an internal decay estimated, ultrasonic wave propagation time was tend to take a longer time. To put it in other words, the velocity of ultrasonic wave propagation was decreased in the deteriorated part of wood. So the velocity is a good indicator of wood deterioration. At the deteriorated position, the velocity decreases from its deterioration of mechanical property, or where there has the longer path of ultrasonic wave transition. Fig.14 and Fig.15 shows the ultrasonic velocity distribution of bridge No. 1 and No.2 of CASE 1. The color painted spots shows the measured point of bridge and its member, and the spotted color shows the velocity ranks. The blue spot shows high velocity and where is in healthy state, and the red spot shows low velocity and un-healthy. This is a relative judgment, so we only could find deteriorated point relatively. But checking this worst point with any other local destructive evaluation method like drilling resistance, we can judge the state of whole structure. This NDT methodology is applicable to all kind of wooden structure with sufficient consideration of wave travelling paths and evaluated ranges.

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1

2

3

4

5

6

7

8

9

Upper 4 Upper 3

Upper 4 Upper 3

Lower 4 Lower 3

Lower 4 Lower 3

No. 1

Lower 2 Lower 1

Lower 2 Lower 1

Upper 2 Upper 1

Upper 2 Upper 1

1

2

3

4

5

6

7

8

9

7

8

9

Fig. 14 Ultrasonic velocity distribution of Bridge No.1 in CASE 1 1

2

3

4

5

6

Upper 4 Upper 3

Upper 4 Upper 3

Lower 4 Lower 3

Lower 4 Lower 3

No. 2

Lower 2 Lower 1

Lower 2 Lower 1

Upper 2 Upper 1

Upper 2 Upper 1

1

2

3

4

5

6

Fig. 15 Ultrasonic velocity distribution of Bridge No.2 in CASE 1

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There are some of similar instruments we could get from the market designed for concrete and so on. But strong pulse wave is necessary to measure the high attenuation materials like wood. Some instruments use a stress wave by hammering except electric generated ultrasonic wave. 3.1.5 Wood screw torque method To detect internal deterioration of CASE 1, we prepared the special method of wood screw torque method [17]. This method is consisted by following process. 1) Pre-bore the 3.5mm diameter penetrated hole at the measuring point of sample 2) Prepare the wood screw which has 3.2mm shank diameter and screw only 10mm at tip 3) Screw into the Pre-bored hole by torque wrench or driver 4) Measure the torque at some rotation angle or turn number 5) Plot the wood screw tip position and detected torque Fig. 8 shows the scheme of wood screw torque method and its results. From this diagram, the deteriorated depth and its range was clearly detected with using some ordinary tools. There are some methods to detect the state of wood along the depth; torque resistance in drilling a hole, thrust (penetration) resistance in drilling, screw withdrawing strength distribution in depth direction and so on. However, these methods induce some local destruction, but it is too small to affect some influence to structural safety to wood members. 25.

Screw torque (kgf・

Torque Wrench 20.

Thinner shank than Pre-bored hole Screw part

Wood (Base material)

Pre-bored hole

15. Healthy Healthy Moderate Deteriorate

10.

5.

0.

0.

5.

11.

17.

23. 29. 34. 40. 46. 52. Turn number: depth (mm)

58.

63.

Fig. 16 Scheme of wood screw torque method, and its results 3.1.6 Borehole camera observation Cutting a wooden member is quite simple to check the residual area where is good state and not affected any deterioration. But any of the members in structure cannot cut to check under use. In CASE 1, we applied borehole camera observation to some holes after applying wood screw torque method. Holes were expanded to 10mm in diameter and inserted borehole camera. Fig. 17 shows its captured image and we could get some similar vision to observe cut cross sections.

Fig. 17 Captured image of borehole camera Straight sight, side view from face to inside (from left to right)

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To insert a borehole camera, the larger diameter of hole was necessary than wood screw torque method. And checking the depth of camera, the state of wood along the hole can make from images, but images cannot evaluate the mechanical property. 3.1.7 Loading test The loading test was carried out to confirm the structural safety in CASE 1. And the relation to the flexure was confirmed. Fig. 10 shows the result of elastic deformation bridge No.1 and No. 2. Only in Bridge No. 1, residual deformation was detected. This residual deformation is expected as an embedment of foundation wood because of its stiffness is quite similar. Load (kg) 1200 1000 800 600 No.2 No.1

400 200 0 -1

0

1

2

3

4

5

6

7

Descending distance at middle of span (mm)

Fig. 18 Loading test, and its results In this case, structural safety was checked only up to the applied load at that time. There is no other information except the evidence of proof load. 3.1.8 Deformation of its shape Start 0 kN 50 kN (Just before) 94 kN Primary Break 94 kN 149 kN (Just before) 190 kN (mm) 0 -200 -400 -600 -800 -1000 1 5 Middle ground

Secondary Break 190 kN

9 13 17 Connection No.

21

25 Left bank

The vertical deformations of principal lowercord truss connections of CASE 2 destructive loading are shown in Fig. 19. This truss bridge was slightly deformed in beginning and it shows that still had enough stiffness. When after primary break, the bridge was slanted toward to up-stream side. The deformation was increased in proportion to bag loading. Before the primary break, the displacement is up to 25mm at the middle of 36m span. During the 60mm displacement of down-stream side truss, upper-stream side truss made a large deformation about 630mm and the bridge was slanted to up-stream side. Until the secondary break, load was doubled, and displacement was increased to about 220mm at the up-stream side truss, and to about 860mm at down-stream side.

Fig. 19 Vertical deformation of lower-cord Truss structure has higher stiffness as a whole structure with only few volumes of wooden members. So we cannot find deformation its shape induced by deterioration of wooden members at a glance. Fig. 20 shows the deformation of CASE 2 from just after rebuild (2007/03/29) to before destructive loading (2008/05/29). The bridge was suspended in the middle of the span. The up-stream deformation 58mm is greater than 51mm at down-stream. The difference is about 7 mm that is 12% of maximum deformation at up-stream. Also the position where the maximum deformation found is matched to the position of primary break.

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[9]

Kazuhiko F., “Say goodbye to Kappabashi-bridge”, Wood Industry, Vol. 59, No. 5, 2004, pp. 229-232

[10] Masaki H., Hirofumi N., Hideo K., Hirofumi I., Atsushi M., Yasushi H., Masahiko K., Kazuhiko F., and Yafang Y., “Non-Destructive Evaluation of Wooden Bridge Members served in 13 years”, JSCE 3rd symposium of wooden bridge and technology, 2004, pp. 139-146 [11] Masahiko K., Kazuhiko F., Atsushi M., Masaki H., Yasushi H., and Hiroshi W., “Study and Transfer Demonstration on Wooden Bridges served in 13 years”, JSCE 3rd symposium of wooden bridge and technology, 2004, pp. 133-138 [12] Masahiko K., Kazuhiko F., Kenichi T., Hirofumi N., and Atsushi M., “Re-build and It's Change of Wooden Truss Bridge which was replaced after 13years use”, JSCE 6th symposium of wooden bridge and technology, 2007, pp. 113-118 [13] Masahiko K., Tomoyuki H., Hideo K., Atsushi M., Kenta S., Kenji A., and Kazuhiko F., “Destructive loading test of a rebuilt wooden bridge served for 13 years”, JSCE 7th symposium of wooden bridge and technology, 2008, pp. 129-134 [14] Masahiko K., Kenji A., Kenta S., Kazuhiko F., Tomoyuki H. Hideo K., and Atsushi M., “Experimental analysis of a rebuilt wooden truss bridge destructive loading test”, JSCE 8th symposium of wooden bridge and technology, 2009, pp. 77-84 [15] The Japanese Society for Non-Destructive Inspection, Non-Destructive Testing method for Concrete Structures, Youkendo, 1994, 377p. [16] Toshinari T. et al., “Evaluation of Bending strength by non-destructive methods on western hemlock attacked by termites”, International Timber Engineering Conference, Vol. 3, 1990, pp. 673-680 [17] Masahiko K., “Internal strength estimation method of wooden material and the device”, Japan Patent, No.3616814, 2004

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