A timber deck and grating deck are often applied to pedestrian suspension bridge with a length of less than 200m and width of less than one lane. It is necessary to consider the effect of deck type on displacement of deck, the tension of the main cable and vibration characteristics. In this study, we focuse on pedestrian suspension bridge that is actually built, and consider the displacement of deck, cable tension and vibration characteristics appling timber deck, grating deck and CLT deck. As a result of analysis, timber deck has same performance as the grating deck.

 Laminated veneer lumber (LVL) can be bent to a smaller radius of curvature than glued laminated timber (glulam) owing to its thin veneers. This property makes curved LVL suitable for various applications, including timber columns, beams, walls, and wooden bridges. To assess the strength properties of curved LVL, we conducted destructive experiments under end-thrust loading. The results revealed that the reduction in strength performance due to curvature averaged only 6.4% for specimens with a radius of curvature of 420 mm. Notably, the reduced strength of curved LVL was significantly less than that of curved glulam. Furthermore, there was no observed reduction in the modulus of elasticity of curved LVL with a decrease in the radius of curvature. To further understand the strength properties of this material, particularly in splitting failure, it is necessary to conduct destructive experiments under end-pull loading.

 In May 2023, a timber bridge that has been popular as a waterside bridge collapsed. The bridge is an arch bridge made of Ekki from West Africa and has been in service for 27 years. Many similar timber bridges were built in Japan in the 1990s. Based on the results of overseas construction, it was said that it would be maintenance-free and could be used for 50 years, but it became clear that it would decay in a short period of time in Japan. It is thought that the reason why many timber bridges like this were built was due to the influence of the myth of the permanent bridge at the time, which believed that maintenance-free bridges were good. Bridge inspections and early repairs are now taken for granted. By studying this bridge, we will formulate the methods of bridge maintenance and consider what is necessary to protect and nurture timber bridges and the lessons that can be learned.

 At depths below the groundwater level, wood is not susceptible to biodeterioration such as decay and termite damage, and thus has begun to be used in countermeasures against soil liquefaction that occurs in areas with shallow groundwater conditions. One advantage of using wood is the long-term storage of carbon fixed in the wood. However, this carbon storage effect is not internationally recognized, so there is a need to accumulate scientific knowledge on this carbon storage effect as a carbon dioxide sink. Accordingly, we conducted an excavation site investigation on logs that had been driven into the ground 8 years earlier as a soil liquefaction countermeasure. We present the groundwater level observation records at the site, and the condition of the logs at 2, 4, and 8 years after their installation. The results of this investigation show that the logs were sound after 8 years despite some logs being above the groundwater level.

 In recent years, cross-laminated timber (CLT) has been used in multi-story wooden buildings and in the civil engineering field. However, the manufacturing and construction costs of CLT hinder its use. Hydraulic presses are used to manufacture domestically produced standard CLT panels. However, some factories overseas manufacture CLT panels using vacuum presses, whose manufacturing cost is lower than hydraulic presses. Although the compression pressure of the vacuum press is small, only a vacuum pump can be used to press with large sheet covering the material, and CLT of various sizes and shapes can be manufactured with lower manufacturing costs. This study aims to examine the possibility of using vacuum presses in the manufacture of CLT made from domestic timber. Test species and adhesive conditions were prepared using vacuum presses and hydraulic presses respectively, and bending performance and adhesion durability were evaluated.

 Pedestrian bridges over mountainous areas in Akita Prefecture are in danger of falling because of heavy snow load during winter. The most trivial approach to prevent such snow trouble is increase stiffness of the bridges, while the approach is not so efficient for season-depending load increase. In this study we propose deck-openable timber bridge, whose deck is openable so that the opening can make snow fall down for winter period. In order to estimate the snow reduction performance of the deck-openable bridge, we carried out outdoor exposure test in one of the heaviest snowfall areas in Akita Prefecture.

 As a result, the snow load was reduced by 50% compared to the case of the deck-closed form of the deck-openable bridge.

 The authors are developing a new timber truss bridges which can be folded in small size, for recovery from disaster. It can be constructed quickly at the disaster site because it is unfolded and assembled in a short time after the transportation by a track in folded condition. In our previous studies, it was confirmed that the construction time was two and half hours by the outdoor test using full scale model with 9.9m span. The assemble of the bridge was done by only human power without using any electronic tools and was done smoothly. However, the bridge has the problem of weight and cost since it needs three kinds of steel members ; connection plates to make a truss panel, connection plates to connect truss panels each other and hinges to fold the bridge. Therefore, the objective of this study is to reduce the steel plates and to make a new hinge structure which has the function to connect truss members and to fold and unfold the bridge. Also, here in this study, the tensile strength of this new hinge is obtained by tensile tests using loading machine. At last, the outdoor construction test is carried out and measured the construction time. As a result of the test, construction man-minute is 1267 under rain condition.

 When using wooden products outdoors, periodic inspection and diagnosis is recommended, and by detecting decay early and replacing parts appropriately, it is possible to use them safely for a long time. In order to efficiently perform inspections and diagnoses without relying on individual experience and ability, objective quantitative discrimination criteria and simple diagnostic methods are required. In this research, using the PILODYN penetration depth (Pe value) obtained from ground part of the column of an entry prevention fence of a high-standard road treated with antiseptic, we investigated a method for early detection of deterioration based on the estimated residual strength, the Pe value distribution of sound materials, and the difference from the Pe value of sound materials (ΔPe value). As a result, if the service life limit is defined as being less than 1/3 of the initial strength, the service life was calculated to be approximately 15 years, which is equivalent to the service life calculated from the ΔPe value. With the method using the Pe value distribution of sound timber, signs of deterioration could be detected approximately 10 years after construction. Application of the results of this research is expected to improve the efficiency of inspection and diagnosis.