Language：Japanese   Publisher：Architectural Institute of Japan  

<p>To investigate whether previous proposed method can estimate bending capacity and shear capacity of steel rebar - glulam timber composite beam, 15 full-scale beam specimens, which a 3 rebar-embedded lamina was bonded as upper and lower outer layer of beam, were applied to loading tests for bending failure or shear failure. Moreover, push-out loading test of rebar in wood test pieces cut-out from one of the tested beam specimens was conducted to verify estimation method for shear capacity determined owing to shear failure around rebar.</p>

DOI： 10.3130/aijs.87.205

Scopus

Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Architectural Institute of Japan  

<p>Recently, from viewpoint of Global Environment, timber, i.e., one of nature cycle materials, has been tried to be utilized as structural members of large timber buildings in Europe and North America. A representative timber of the members is Cross-laminated timber (CLT), however, CLT structural system very often restricts planning of building because of CLT being plate member. High-stiffness-strength-timber slender beam and column are significantly desired.</p><p>This study focuses a hybrid glulam timber with steel deformed bar (rebar) and Epoxy resin adhesive. Aim of this study is to propose an approach to predict elasto-plastic behavior of the hybrid timber column under lateral reversed cyclic loading, assumed to be attacked by big earthquake. The approach adopts a numerical calculation software for reinforced concrete(R/C) members, using Multi-spring model for R/C column yielded at its bottom by moment. The calculation results were verified with experimental results of hybrid columns previous reported in Reference 1, including skeleton curve, hysteresis loop, energy dissipation, and minimization of residual displacement.</p><p> </p><p>The results are summarized as followings:</p><p>(i) The RC's numerical calculation software is extremely useful for us to predict elasto-plastic behavior of the hybrid timber column because the column has no damages expect yielding of joint rebars between its column' bottom and RC foundation, until 1/50 radian of maximum drifts.</p><p>(ii) Skelton curves, reversed cyclic hysteresis loops, and amount of energy dissipation of the columns have been precisely predicted to the experimental results.</p><p>(iii) The length of the Multi-spring model for plastic hinge of the column could be recommended to be 7/8 of its column' depth.</p><p>(iv) Equivalent viscous damping factor of the column and final residual displacement in quasi-static free vibration immediately after target displacement, under the column bottom yielding, also were predicted on safe side.</p>

DOI： 10.3130/aijs.86.589

Scopus

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Architectural Institute of Japan  

<p>Recently, from view－point of Global Environment, timber, i.e., one of nature-cycle materials, is being tried to be utilized as structural members of large timber buildings in Europe and North America. </p><p>A representative timber of the members is Cross-laminated timber (CLT), however, CLT structural system very often restricts planning of building because of CLT being plate member. High-stiffness-strength-timber slender beam and column are significantly desired.</p><p> This study focuses a hybrid glulam timber beam with steel deformed bar (rebar) and Epoxy resin adhesive. The aim of this study is to clarify mechanism of suppressing bending creep of the hybrid beam by rebars and to develop method of estimating its relative creep coefficient in design. This paper reported creep behavior of hybrid glulam timber beams with a small size under 4-year term loading and additional coated beams under 1.5-year term loading. The coated beam specimens were prepared in order to investigate adverse effects of moisture on shear stiffness of wood around the rebars. The result and discussion of the two experiments are summarized as follows:</p><p>(ⅰ) Creep of curvature of the hybrid beam rapidly boosted against prediction based on assumption of Navier hypothesis, during same term in every year when humidity increases in Japan, i.e., July-September, as Fig.11.</p><p>(ⅱ) The boost results from position of rebar-embedded lamina in the beam section because moisture in air around beam percolates surface of its timber and decreases shear stiffness of wood part around rebars. One of basic ways to protect the decrease is to arrange the rebar-embedded lamina as the second layer from outer layer because adhesive layers between the outer layer and the second, as seen in Fig. 20, prevent the moisture from percolating the second layer , i.e., rebar lamina.</p><p>(ⅲ) This problem may occur in the small-sized beam, however, the real full-sized hybrid beam can readily prevent it in some ways as shown in Fig.20(b),(c), by using waterproof coating, burning marginal later, or refractory coating.</p><p>(ⅳ) The protected hybrid beam is estimated to significantly suppress its bending creep by rebars, as Relative creep coefficient C_φ of curvature in 50-year for design listed in Table 8. </p><p>(ⅴ) Deflection-stiffness of timber beam and hybrid beam rarely deteriorated during creeping, as Fig.25.</p><p>(ⅵ) A prediction method for relative creep fluctuating intensely owing to seasonal influence was proposed by using two - tangent lines on logarithmic chart, as Fig.21, Fig.22, and Fig.23.</p>

DOI： 10.3130/aijs.86.1190

Scopus

Authorship：Last author,　Corresponding author   Language：Japanese   Publisher：World Conference on Timber Engineering 2021, WCTE 2021  

Scopus

Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Architectural Institute of Japan  

<p> Recently, from view-point of Global Environment, timber, i.e., one of nature-cycle materials, has been tried to be utilized as structural members of large timber buildings in Europe and North America. A representative timber of the members is Cross-laminated timber (CLT), however, CLT structural system very often restricts planning of building because of CLT being plate member. High-stiffness-strength-timber slender beam and column are significantly desired.</p><p> This study focuses a hybrid glulam timber with steel deformed bar (rebar) and Epoxy resin adhesive.</p><p> Aim of this study is to reveal elastic-plastic behavior of the hybrid timber column under lateral reversed cyclic loading, assumed to be attacked by a large number of big earthquakes. Column specimens were designed to yield at columnreinforced concrete foundation connection by bending.</p><p> The result of loading test and its discussion are summarized as follows:</p><p> 　(i) Proposed connection of column and foundation demonstrated potential of minimizing damage and final residualdisplacement and protecting degradation of hysteresis loop of the column even if reversed cyclic loading by 8-bigearthquakes was applied.</p><p> (ii) The final residual displacement drift was minimized to be less than 1/400rad., which can be neglected by the eye ofhuman, by quasi-static cyclic reverse loadings resembled free vibration to reveal the re-centring of the column afterthe bottom flexural yielded at earthquakes.</p><p> (iii) The hysteresis loops, indicated spindle shape with no pinching and abundant energy dissipation as never observedin RC columns.</p><p> (iv) The column has a region near interface between column and foundation, where bending stiffness for the hybridglulam timber cannot generate, and an assumption that bending stiffness at the region is degraded as Fig. 22(b), produces fairly good estimation of lateral stiffness of the column until its yielding.</p><p> (v) Lateral stiffness and loading capacity of the column produced approximately as much as those of a reinforced concretecolumn replaced wood with concrete of compressive strength 30N/mm².</p>

DOI： 10.3130/aijs.86.107

Scopus

Authorship：Corresponding author   Language：Japanese   Publisher：World Conference on Timber Engineering 2021, WCTE 2021  

Scopus

Authorship：Last author,　Corresponding author   Language：Japanese   Publisher：World Conference on Timber Engineering 2021, WCTE 2021  

Scopus

Authorship：Last author,　Corresponding author   Language：Japanese   Publisher：World Conference on Timber Engineering 2021, WCTE 2021  

Scopus

Authorship：Last author,　Corresponding author   Language：Japanese   Publisher：World Conference on Timber Engineering 2021, WCTE 2021  

Scopus

Language：Japanese   Publisher：Architectural Institute of Japan  

<p> Recently, from view－point of Global Environment, timber, i.e., one of nature-cycle materials, has been tried to be utilized as structural members of large timber buildings in Europe and North America. A representative timber of the members is Cross-laminated timber (CLT), however, CLT structural system very often restricts planning of building because of CLT being plate member. High-stiffness-strength-timber slender beam and column are significantly desired.</p><p> This study focuses a hybrid glulam timber beam with steel deformed bar (rebar) and Epoxy resin adhesive. Aim of this study is to derive equations for internal stress of hybrid glulam timber beam by temperature and moisture content variation in its timber were derived from a differential equation. The result of derivation, numerical analysis, and its discussion are summarized as follows:</p><p> (i) A spring model for the hybrid glulam timber beam was proposed to derive the equations, by simplifying essential elements of the hybrid beam.</p><p> (ii) Effects on internal stress when temperature rises 60℃ or moisture content(MC) rises 3% were discussed; equations for axial stress of rebar and timber in way of beam axis, and bond stress around rebar at MC of 3% were suggested.</p><p> (iii) The equations were verified with numerical analysis for two beam cross sections with span lengths from 4-m to 20-m. Calculations by the equations were fairly good agreed with calculations by the numerical analysis.</p><p> (iv) Under natural environment in Japan, air temperature rises with air humidity, therefore effects on internal stress in the hybrid beam of timber temperature and moisture content are estimated to decrease. Also, large size timber utilized for the hybrid beam could not absorb air moisture compared with smaller size timber. Hereafter, standardization of temperature and moisture content for the hybrid beam will be required.</p>

DOI： 10.3130/aijs.85.1469

Scopus

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Authorship：Corresponding author   Language：Japanese  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：Japanese   Publisher：Architectural Institute of Japan  

&nbsp;Recently, from view-point of Global Environment, timber, i.e., one of nature-cycle materials, has been tried to be utilized as structural members of large timber buildings in Europe and North America. A representative timber of the members is Cross-laminated timber (CLT), however, CLT structural system very often restricts planning of building because of CLT being plate member. High-stiffness-strength-timber slender beam and column are significantly desired.<br>&nbsp;This study focuses a hybrid glulam timber with steel deformed bar (rebar) and Epoxy resin adhesive. Hybrid timber beams such as this study technique has been researched as we can recognize at several references^6)-17). No research, however, on duration of load factor of hybrid timber beam has been conducted.<br>&nbsp;Aim of this study is to reveal duration of load (DOL) factor of the hybrid timber beam under bending load. We conducted short-term loading test and long-term loading test. The short-loading test was conducted to identify maximum loading capacity necessary for stress level in long-term loading test.<br>&nbsp;The result of short-term loading test and its discussion are summarized as follows:<br>&nbsp;(i) The number of specimens of hybrid timber beam and timber beam, which each have same cross-section, was ten. Standard deviation (&sigma;hy) of maximum bending capacity of the hybrid timber beams was 41% of that (&sigma;w) of the timber beams. Mechanism of the deviation reduction by rebar is worth to be researched furthermore;<br>&nbsp;(ii) Standard deviation of bending moment at rebar yielding of hybrid timber beam is extremely small because same production rebars are used and property of the rebar is stable, whereas that of bending moment capacity of the timber beam is comparatively large because bending strength of timber is more variable;<br>&nbsp;(iii) Bending moment－curvature curve of the hybrid timber beam can be precisely predicted by calculation using Bernoulli-Euler hypothesis and appropriate stress- strain curve of rebar and timber.<br>&nbsp;The result of long-term loading test and its discussion are summarized as follows:<br>&nbsp;(iv) Nearly all of the data of DOL factors of the hybrid timber beams tested were more than value of Madison curve and conventional timber beam, and DOL factor after 50 years of the hybrid timber beam is predicted to exceed DOL factor, i.e. 55%, required by Japan's Building Standards Act;<br>&nbsp;(v) Equation (5) to predict DOL factor curve of the hybrid timber beam has been proposed, which is based on assumption: DOL factor of timber is calculated by Madison curve; all rebars have yielded in fracture of the beam, and; maximum bending moment capacity of the beam is equal to sum of its timber bending moment and its rebar bending moment. The equation predicted approximately experiment data of DOL factor of the hybrid timber beam: the all experiment data ranged within standard deviation (&plusmn; &sigma;hy) of bending moment capacity of the beam in short-term loading to curve by Equation (5) as seen in Fig. 11 (b);<br>&nbsp;(vi) Design methods of check to prevent bond failure around rebar and shear failure of web in the hybrid timber beam are described in order to ensure to fail under bending load. By the method, hybrid timber beam specimen of this experiment has been evaluated not to collapse by the bond failure and the shear failure after 50 years, and DOL factor after 50 years, which is predicted by Equation (5), has been evaluated to demonstrate its ability.

DOI： 10.3130/aijs.84.257

Scopus

Language：Japanese   Publisher：Architectural Institute of Japan  

Hybrid glulam timber beam reinforced with deformed steel bar (rebar) and epoxy resin adhesive is reported on followings:<br>1. Review of works of the hybrid timber beam, importance of increasing bending stiffness under short-term loading by 3-4 times of those of conventional glulam timber beam, and target of this study are described.<br>2. The hybrid timber beam adopted a large amount of rebar was tested by short-term loading.<br>3. Equations for allowable moment, bending strength, moment-curvature of the hybrid timber bam are proposed.<br>4. Equations for shear deformation of the hybrid timber beam are also proposed.

DOI： 10.3130/aijs.84.247

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Doctoral thesis  

二次壁を非構造化する設計法の開発を行った。

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