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ラグスクリューボルト接合部の引抜き時における応力伝達機構の解明 CiNiiでみる

著者名:
瀧野 敦夫  室伏 祐美  大坪 祐介  森 拓郎  中谷 誠  小谷 竜城  功刀 厚志 

抄録:

 In this study, the experiments and a three-dimensional finite element analysis were conducted to verify the stress distribution in the glulam at the Lagscrewbolt (LSB) joints. In this paper, a well-formed and uniform three-dimensional finite element analysis model is used to understand the stress distribution in detail and to examine the effects of different cross-sectional sizes and LSB lengths on the stress distribution.

 The experimental results (Fig. 6), using from 75-mm square to 120-mm square cross-section glulam, showed that the values of strain gages attached to the sides of the glulam gradually increased from the sides of the glulam toward the center of the cross-section, which differs from the assumption that the stress distribution within the same cross-section is constant, which is assumed by the existing theoretical equations.

 Since the analysis using standard values for material constants with reference to existing literature resulted in a larger initial stiffness than the experimental results, reducing the shear modulus of elasticity in the fiber direction to 1/4 showed a good agreement with the experimental results (Fig. 9 and Fig. 10). In the analysis model with different material constants around LSB, a material constant of 1/20 times of the standard value was used, which corresponds to the experimental results (Fig. 9 and Fig. 10). However, there are still some issues that need to be considered regarding the modeling method. The shear stress distributions along the LSB showed a concave shape (Fig. 12), where the shear stress of the elements adjacent to the LSB at the end of glulam and the deepest part was larger than the theoretical equation. On the other hand, one of the outer elements showed a nearly uniform shear stress distribution in the depth direction. Stress distributions within the same cross-section at specific depths showed that shear stress decreases from the center of the glulam (LSB side) to the outermost edge of the glulam (side of the glulam) for all cross-section sizes (Fig. 14). On the other hand, normal stresses did not decrease at the outermost edge at 75- and 87.5-mm square cross-sections, while those at 100-, 120- and 200-mm square cross-sections showed a gradual decrease toward the outermost edge (Fig. 14). However, some stress loading was also observed in the elements near the outermost edge. The effective cross-sectional area borne by the stresses used in the existing theoretical equations was investigated (Fig. 17). As a result, if the effective cross-sectional area is assumed to be constant, the ratio of stress borne in the effective cross-section to the total cross-section decreases as the cross-section of the glulam increases (Fig. 19). It was found that in order for the stress borne in the effective cross-section to exceed 80% of the total, it was necessary to increase the effective cross-section as the cross-section of glulam increased. For the same cross-section of glulam, the ratio of stress borne in the effective cross-section decreased as the length of the LSB increased. Therefore, even if the load is the same, the stress is generated in the entire cross-section of the glulam as the LSB becomes longer.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
97-106 , 
ISSN:
1340-4202

拡張型鋼管杭で補強された砂質土地盤の鉛直支持力 CiNiiでみる

著者名:
黒柳 信之  伊藤 淳志  山崎 雅弘 

抄録:

 The authors have proposed a new ground reinforcement method using expansion steel pipe piles, which expand diameter from 36 mm to 54 mm by injecting high pressure water into a steel pipe deformed into the heart shape and sealed the both ends. The proposed method aims to increase the bearing capacity of the small building foundation, and to prevent the differential settlement of a small building on poor sandy ground.

 In continuation of the research, this study focused on using the expansion steel pipe piles in composite ground, and vertical loading tests were carried out at both an artificial site and two natural sites composed of sandy soil.

 The ground at the artificial site was prepared by backfilling sandy soil into a pit with dimensions of 1500 mm width, 4250 mm length and 2300 mm depth. In addition, two natural sites consisting mainly of sandy soil were selected and loading tests were conducted at five locations in each.

 At the artificial site, comparison experiments were conducted in order to investigate the settlement behavior and bearing capacity of composite ground containing simple steel pipe piles with the same diameter as the expansion steel pipe piles. At the natural sites, the effect of ground reinforcement was confirmed by changing the size and shape of the foundation and the number of expansion steel pipe piles. In addition, FEM analysis using the artificial site as a model was performed and the effect of the expansion steel pipe piles on improving the ground bearing capacity was investigated. The findings obtained in this study are as follows:

 1) At the artificial site (average converted N-value of 2.6), results from the loading tests on composite ground containing simple steel pipe piles show that the ultimate bearing capacity of the composite ground was equal to the sum of the ultimate bearing capacity of the piles and that of the ground. However, in the case of composite ground containing expansion steel pipe piles the ultimate bearing capacity was 15% higher than the sum of the ultimate bearing capacity of the piles and that of the ground.

 2) At the natural sites (average converted N-values of 6.5 and 5.4), the ultimate load was not reached during loading tests on composite ground containing expansion steel pipe piles, however after the initial stage of subsidence the bearing capacity of the composite ground was almost equal to the sum of the bearing capacity of the piles and the bearing capacity of the ground.

 3) From the results of the 3D FEM analysis, which used the loading tests at the artificial site as a base model, it became clear that the effect of expansion of the expansion steel pipe piles on the compaction of the surrounding ground was greater for ground with a smaller Young's modulus (or converted N-value), and that this in turn gave a greater increase in the bearing capacity of the composite ground.

 4) From the above results of the loading tests and FEM analysis, it can be inferred that expansion of the expansion steel pipe piles in composite ground with a converted N-value of approximately 3 or less will lead to an increase in the bearing capacity of the ground.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
89-96 , 
ISSN:
1340-4202

発射打込み鋲(PAF)の構造部材への接合(その1):デッキプレート接合部の耐力 CiNiiでみる

著者名:
吉敷 祥一  アプリヤーディ・ジャスミン アニーサ  巽 信彦  渡辺 英一  岡田 雄吉  長谷部 優  飯島 孝幸 

抄録:

 Power actuated fasteners (PAF) are fasteners shaped like smaller construction nails which are installed using a driving tool with enhanced power and are one of the preferred tools for connecting metal decking due to the fast installation time and consistent quality. However, not enough research has been conducted on the fundamental strengths of PAF connections and structural engineers are concerned about their effect on structural components, especially plastic deformation capacity. Therefore, in this paper, evaluation models for the tensile and shear strengths of PAF joints were discussed through experiments as well as observations on the JSSC requirements for PAF spacing and edge distance of both beam flange and deck plate.

 2 types of tensile tests were conducted to investigate the ultimate strength and failure modes of tensile loading on PAF joints. In tension, PAFs have 2 main failure modes, which are pin pull-out failure and deck plate pull-over failure. Pin pull-out strength can be evaluated by multiplying shear stress by the contact area between the pin and the steel embedment. For the pin pull-out failure, the maximum strength is in proportion to the contact area, and the ultimate shear stress was obtained for each shape of PAF. On the other hand, deck plate pull-over failure was observed in specimens with lower strength of steel grade, SPCC. It is assumed that deck plate pull-over failure is caused by shear stress applied at the lateral surface of a cylindrical area at the deck plate with the diameter of the pin head and the thickness of the deck plate. Furthermore, it could be shown that the evaluation model based on deck plate shear failure around the pin head can evaluate the maximum strength obtained from the experiments.

 Shear tests were conducted mainly to observe the ultimate strength and failure modes of the deck plate in shear. The failure modes are classified into tear-out and bearing of the deck plate. The experiment results showed that the JSSC requirement for edge distance of deck plate is effective to avoid the tear-out failure of deck plate. On the other hand, the bearing strength of deck plate could be evaluated by an equation from the AISI standard. Finally, compared to puddle welding conducted in previous researches, it is found that these strengths are proportionate to the PAF's diameter.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
135-144 , 
ISSN:
1340-4202

薄層支持層における杭先端支持力特性に関する研究(その2):模型杭載荷試験による支持力機構の検討 CiNiiでみる

著者名:
山崎 雅弘 

抄録:

 The pile end bearing capacity is reduced when the pile is constructed on the thin bearing layer overlying clay layer. This paper focuses on the bearing capacity mechanism based on the results of the model pile test. The soil tank of the test is semi-cylindrical. The side of the tank is constituted by a semi-cylindrical steel plate and a flat acrylic board. The ground displacement can be observed through the acrylic board. In addition of the pile load and settlement, the ground displacement as photograph and the horizontal earth pressure in the thin bearing layer were recorded. These records were shown in the following figures. (1) distribution of the ground vertical displacement (2) distribution of the ground maximum shear strain (3) pile load and the settlement relationship and the horizontal earth pressure and the settlement relationship.

 The figures (1) and (2) lead to the recognition that there are two types of the bearing capacity mechanism. The one occurs if Hs/d is 3 or more (Hs is the thickness of the bearing layer. d is the pile diameter.), and is that the shear strain zone stays around the area below the pile end and does not develop. The other occurs if if Hs/d is 2 or less, and is that the shear strain develops downward vertically from the pile end outside to the clay layer. The latter is punching failure that the cylindrical shear strain zoon makes a columnar ground which moves downward with the pile. The bearing capacity of the punching failure is the sum of the shear resistance force of the columnar ground side surface and the base resistance force from the clay layer.

 The figure(3) shows the phenomena that the pile load reduction and horizontal earth pressure reduction occur at almost the same settlement. It can be explained by the punching failure model because of the strong relation between the shear resistance force of the columnar ground side surface and the horizontal earth pressure. The explanation enhances the existence of the punching failure.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
77-87 , 
ISSN:
1340-4202

圧縮力が作用する冷間成形リップ付溝形断面部材の数値解析結果に幾何学的初期不整が及ぼす影響 CiNiiでみる

著者名:
三井 和也  渡辺 茜  小橋 知季  五十嵐 規矩夫 

抄録:

 Thin waled cold-formed steel member is manufactured by cold-forming a galvanized steel sheet of less than 2.3 mm. It is possible to manufacture a variety of cross-sectional shapes with less expensive manufacturing equipment than the conventional hot rolling process. This thin waled cold-formed steel member allows for greater customization (different web, flange and lip width) that can cater for many industrial applications of flooring, roofing, or modular building systems. In this thin waled cold-formed steel members, since the width-to-thickness ratio of the plate elements that make up the cross-section is large, local buckling is likely to occur at the plate elements before the maximum strength is reached. In addition, since a unique buckling mode called distortional buckling that includes the collapse of the cross-section is occurred, one of the important research subjects is to analyze the buckling behavior in detail and to establish a quantitative evaluation method of member strength. Numerical analysis by the finite element method is a useful tool for analyzing the complex buckling behavior of thin waled cold-formed steel members. However, regarding the validity of buckling behavior combined with eigenvalue analysis, there are very few studies that analyzed in detail the effect of changes in initial imperfections on the analysis results, and it is necessary to clarify the application range of the method that introduces the initial imperfections based on the eigenvalue analysis results.

 In this paper, the effect of initial imperfections in the finite element analysis on the buckling behavior of cold-formed lipped channel steel member is investigated. Firstly, the buckling behavior and its buckling mode are clarified by stub column tests. Then, the effect of the differences in the shape of the initial imperfections in finite element analysis is investigated.

 From the stub column tests, the following are found.

 1) In the case of a cross-section that satisfies the required lip width and the maximum strength is determined by local buckling, the maximum strength can be evaluated by accumulating the maximum strength of each plate element. On the other hand, in the case of a cross-section that does not satisfy the required lip width, the maximum strength determined by local buckling cannot be evaluated by this method.

 2) Based on the DSM, the local bucling and the distorsional buckling strength are evaluated on the safe side. Also, the coupled buckling strength, which does not directly specified, can be evaluated on the safe side.

 3) In the case of a cross-section that does not satisfy the required lip width, the buckling mode changes due to the initial geometric imperfections. From the numerical analysis results with initial imperfections as parameters, the following are found.

 4) The buckling mode determines the maximum strength changes in the cross-section that does not satisfy the required lip width due to the difference in the shape of the initial imperfections. On the other hand, regardless of the required lip width requirement, the shape of the initial imperfect has a small effect on the maximum strength.

 5) Regardless of the conformance of the required lip width condition, the analysis condition that introduces the maximum imperfection obtained from the larger value of the web or flange width-to-thickness ratio and eq. (5.a) into the analysis model based on the first-order eigenmode can almost reproduce the maximum yield strength obtained from the short column compression test.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
157-167 , 
ISSN:
1340-4202

人力加振による杭頭のインパルス応答を用いて弾性領域における杭頭の静的ばねを推定する方法 CiNiiでみる

著者名:
成田 修英  大沼 満  川幡 栄治  阿部 秋男  新井 寿昭  沼本 大輝  佐藤 武  福田 健  小阪 宏之  久世 直哉  飛田 喜則  岸本 剛  小川 敦  冨田 祐介  内田 崇彦 

抄録:

 Recently, there are few construction works in vacant lot. Many construction works take place after demolishing the existing building. In such case, reuse of the existing piles is reasonable. We need a way to verify the performance of the existing piles for reuse. Therefore, in this paper, we proposed a simple method for estimating the static elastic pile-head spring using the impulse response excited by human power. We also proposed a simple method to simulate the impulse response of the pile-head.

 The steps for the proposed estimation method are as follows:

 1. Attach the accelerometer to the target pile-head.

 2. Hit the pile-head with an impulse hammer to obtain the time series data of the input and response of the pile-head.

 3. Calculate the impulse response of the pile-head by using the data.

 4. Pile-head spring we want is the reciprocal of the impulse response.

 Dynamic model proposed to simulate pile-head response is a beam-on-Winkler-foundation considering its own inertial force. Assuming homogeneous subgrade and applying some boundary conditions to the model, closed-form solutions of pile-head response can be obtained. By using these solutions, we can simulate the pile-head response easily.

 As a verification examination, we compared results of the proposed methods with results of static load tests. We conducted the examination on a total of five piles at three locations. As a result, we confirmed that the results of proposed methods agree with the results of static load test.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
65-75 , 
ISSN:
1340-4202

等曲げモーメントを受ける連続補剛H形鋼梁の弾塑性横座屈に及ぼす横曲げ拘束効果 CiNiiでみる

著者名:
木村 祥裕  佐藤 唯 

抄録:

 In design standard for steel structures (AIJ 2005), the boundary condition of beams under lateral buckling load is provided as simple support. Meanwhile, beams are often jointed to box-shaped columns with high torsional rigidity as shown in Figure 1. Therefore, beam ends have fork restraint by high torsional rigidity of column on lateral buckling, which is considered the rotational effect between warping and fully fixed supports.

 On the other hand, long span main beams may not possess the full plastic strength due to lateral buckling, so that many lateral braces should be set up along the beams to prevent the lateral buckling deformation (AIJ 2010). When non-structural members such as folded roof plate are directly jointed to beams, they may be used as the continuous braces. However, in Japanese design code, the non-structural members are not considered as braces. Kimura, Yoshino, and Ogawa (2013) clarified the lateral buckling behavior for H-shaped beam with continuous braces when the boundary condition of the beams is simple support.

 This paper evaluates the effect of fork restraint on elastic lateral buckling load for H-shaped beams with continuous braces under the uniform flexural moment and Saint-Venant torsional rigidities in energy conservation equations. In this study, two types of loading conditions are considered, where the upper flange's compressive load is larger than the lower flange's one (loading condition, Type A), and where the upper flange's compressive load is smaller than the lower flange's one (loading condition, Type B). The continuous braces rigidity is divided into the lateral rigidity, ku, and rotational rigidity, kb, as shown in Fig. 1. In the case of Type A, lateral rigidity is effective for preventing lateral deformation of compressive upper flange, whereas in the case of Type B, rotational rigidity is effective for preventing torsional deformation. Considering fork restraint by column, elastic lateral buckling load of beams with continuous braces are expressed as the loads between warping and fully fixed support.

 This study is conducted by the following procedures:

 ・ The elastic lateral buckling load with warping and fully fixed support under flexural moment is developed by energy method, and can be calculated with Eqs. (11)~(13). Considering fork restraint by column, elastic lateral buckling load of beams with continuous braces are expressed as the loads between warping and fully fixed support. The results are verified by eigenvalue analyses.

 ・ The elasto-plastic lateral buckling behaviors of the beams are simulated by elasto-plastic large deformation analysis. The lower bound of the elasto-plastic lateral buckling stress of the beams are evaluated according to the buckling curve of bending member provided by Recommendation for Limit State Design of Steel Structure (AIJ), using proposing modified equivalent slenderness ratio.

 ・ The relationship between the total value of the stiffing force of the whole continuous braces and the maximum value was grasped. In the case of warping fixed support, the total value is about 60% of the upper bound value. Next, it decreases as the fork rigidity increases, and is about 35% in the case of fully fixed support.

 ・ The upper bound of rotational stiffening moment and lateral stiffening force of continuous braces is evaluated by Eqs. (24) and (25) based on the ratio of flexural and torsional rigidities of beams when the lateral buckling of beams with fork restraint by column occur.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
145-155 , 
ISSN:
1340-4202

縮小立体架構の載荷加熱実験結果に基づく鋼架構の火災時応力再配分の評価 CiNiiでみる

著者名:
齋藤 真美  岡﨑 智仁  河野 守 

抄録:

 It is well known that even if a heated column collapses in fire, the axial load that the bucked column has sustained can be redistributed to the peripheral members by the shear forces of the beams arraigned in above stories than the fire compartment room. Thus, a frame having high degree of redundancy can be avoid overall collapse even if some of heated columns lose load carrying capacity. Many researchers have been reported in literature, however, most of the previous studies focused on the analytical investigation of in 2D frames. Stress redistribution in 3D frame is not investigated fully. In the recommendation for fire resistant design of steel structures (Architectural Institute of Japan, 2017), only the stress redistribution of a planar frame is considered. The stress redistribution for multiple frames is not considered.

 In this study, fire tests and numerical analysis with scaled down steel moment frames were carried out to grasp the stress redistribution mechanism in 3D frame. The test frame was steel frame with 2-span 3-layer structure, and members in the second story of a perimeter frame are heated. Two types heating conditions were apllied : only the center column and connecting three beams were heated, and the center and two corner columns and connecting beams were heated. The columns and beams were heated while a constant load was applied at the top of columns. By the fire test and numerical analysis, the following 1)~3) were clarified.

 1)By the thermal elongation of the heated column, compressive axial forces are generated in the columns located above and below the heated column. A tensile axial force is generated in columns adjacent to the heated column. As the axial rigidity of heated column deteriorates, and the column shrinks and, the tensile force developed in the adjacent columns decrease, after the heated column fails to bear the applied load, the compression axial force that has been sustained by the heated column is redistributed to the adjacent column by shear forces developed in the beams. In the 3D frames, stress redistribution occurs in multiple planes of the frame.

 2) Considering the formation of plastic hinges during fire test by the thermal stress, the mechanism of stress redistribution can be evaluated by the elastic numerical analysis with simple fiber model. After plastic hinges are formed in the heated members and peripheral members, the influence of the thermal stress on structural behavior becomes extremely small.

 3) In this fire test, not all the ends of beam were plasticized. The shear forces of the beams at this time were evaluated by numerical analysis. After both ends of beam reach their full moment capacity, stress redistribution capacity is evaluated from fully plastic moments and length of beams located in the above stories than the fire compartment room.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
169-179 , 
ISSN:
1340-4202

建築物のさらなる超高層化に向けた等価質点モデル化手法(その2):新たな曲げせん断モデルを用いた建物応答の曲げ・せん断分離手法 CiNiiでみる

著者名:
渡井 一樹  前田 周作  笠井 和彦  佐藤 大樹  鈴木 庸介 

抄録:

 When a super-tall building is designed, a member-to-member model is constructed to represent the assembly of columns, beams, walls and so on. The seismic response analysis using this model is computationally expensive and outputs large amount of data. Therefore, an equivalent mass-spring system with a small number of elements and short analysis time is useful at the initial design stage. Since the influence of bending deformation becomes large as building becomes taller, it must be simulated by the equivalent mass-spring system. The companion paper (Part 1) therefore proposed a simplified method to formulate such an equivalent system, and named it as the bending-shear model. In this paper, we extend the modeling method to and verify the model accuracy for various super-tall buildings.

 We consider four different buildings heights from 80m to 400m, as well as three different structural frames such as moment resisting frame, center core frame, and outrigger frame combined with center core. The method can be easily applied to these various frame types because the bending stiffness is calculated using only horizontal displacement given as the overall responses, in contrast to existing method that considers deformations of all the vertical members. Note however that the pure moment loading analysis discussed in the companion paper is modified to cover different systems mentioned above, considering their distinct distributions of column axial deformations.

 The bending stiffness of bending-shear model obtained with the pure bending moment analysis is larger than member-to-member model appear to under story moment and shear forces. Therefore, the proposed method corrects the bending stiffness of bending-shear model. Correction coefficient is designed to the second natural period of bending-shear model match member-to-member-model. As such, the second eigenvector and third natural period and eigenvector match fairly well regardless of the structural frame type. Moreover, the building responses can be easily separated into bending and shear components by using the bending stiffness and shear stiffness obtained the proposed method. This is the first method that can clearly evaluate the contribution of each shear and bending components to each mode.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
21-31 , 
ISSN:
1340-4202

塔状比の大きい上部構造物・杭基礎-地盤系の遠心載荷実験に基づく液状化地盤における鋼管杭の終局メカニズム CiNiiでみる

著者名:
木村 祥裕  的場 萌子  田村 修次 

抄録:

 Steel piles below high-rise buildings may carry larger varying axial force generated by the overturning moment than those below low- or medium-rise buildings. On top of that, the subgrade lateral stiffness reduces drastically due to the soil liquefaction during a significant earthquake. Steel pile's horizontal strength may decrease due to the lower position of the inflection point. In this paper, centrifugal tests of the superstructure with high height-to-width aspect ratio, steel piles, and the liquefied soil system are presented. The collapse mechanism and the horizontal load bearing capacity of steel piles in the liquefied soil are clarified.

 Fig. 1 shows the model and instruments. The specimen consists of a superstructure with mass, a footing beam with mass, two bending plates, four piles, and a saturated sand layer. Table 2 shows specimen parameters, which are the height-to-width aspect ratio of the superstructure and the relative density of the soil. The centrifugal tests were performed under the centrifugal acceleration of 40 g.

 Figs. 5-18 show response time histories of Case 1-Case 6. The bending strain at the pile head gradually increases toward the one side after the soil liquefaction and reaches the maximum value, εb,max. After reaching εb,max, the piles of all specimens collapse, except for Case 4. As presented in Fig. 20, in the case of the same Dr values, the sum of pile head's shear forces, ΣQph at εb,max are approximately equal regardless of the height-to-width aspect ratio. An additional shear force generated by pile's P-Δ effect, QPΔ,pl, accounts for the largest part in ΣQph. On the other hand, in the case of high height-to-width aspect ratio, the value of QPΔ,pl is smaller issued from larger additional shear force generated by the superstructure's P-Δ effect, QPΔ,s.

 Fig. 21 shows the relationship between pile's strength on the centrifugal tests and the M-N interaction curves of design criteria. Ratios of pile's varying axial force to pile's flexural buckling strength, Npl/Ncr0, are the same until at εb,max regardless of the height-to-width aspect ratio. For piles subjected to the dead load and the varying axial compression force of all specimens, the combinations of axial force and bending moment at εb,max are distributed roughly following the ultimate strength curve as presented in Ref. 6. On the other hand, the results of the pile subjected to the dead load and the varying axial tensile force in the case of Dr=30% are lower bound to the M-N interaction curve as shown in Ref. 9 and those of the case of Dr=60% approximately reach that curve.

 As presented in Figs. 22-24 and table 3, steel piles' collapse mechanism is concluded as follows. Pile's bending moment reaches pile's full plastic moment, vrMpc,cr0, at the top and the bottom of the pile subjected to the varying axial compression force. In the case of Dr=60%, pile's bending moment also approximately reaches vrMpc,cr0 at those points of the pile subjected to the varying axial tensile force due to the increase of the distribution ratio of superstructure's and footing beam's shear force after at εyc.

 As shown in Fig. 24, it is concluded that steel piles' horizontal load bearing capacity can be evaluated easily using steel piles' horizontal strength based on the location of the inflection point in the liquefied soil and pile's plastic bending strength reduced by initial axial force.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
53-63 , 
ISSN:
1340-4202

多層建築物内の上下の床に固定された軽量な曲げ棒に作用する地震時の慣性力と強制変形について CiNiiでみる

著者名:
石原 直  元結 正次郎  吉敷 祥一  沖 佑典 

抄録:

1. Introduction

 In the seismic design of secondary systems (SS) such as nonstructural components, inertial and relative displacement effects are usually considered independently. But the reason for this independence is not clarified enough. In past researches, response spectrum methods have been proposed to analyze three-dimensional piping. Those methods are too complicated to apply for the seismic design of SS in general buildings. It seems useful to obtain basic knowledge for the practical design of SS by studying both effects with a simple typical model.

 In this paper, seismic responses due to both effects are studied for SS modeled as light-weight bending beams fixed to the upper and lower floors in a multistory building through response history analysis.

2. Mathematical model and analysis method

 Lumped-mass shear-type models and uniform bending-beam models are used for structural frames and SS respectively. The boundary conditions of SS are pin-ends and fixed-ends. The former condition is for comparison and has no effect of relative displacement. Structural frames and SS are assumed to be linear.

 A modal analysis method is derived. For inertial effect, responses of modes of structural frames are used as inputs to those of SS.

3. Response histories and peak sectional forces

 A three-story model is used as a structural frame. The first natural period is set to be 0.6 sec. except for some cases, while those for SS with pin-ends and fixed-ends are set to be 0.4 and 0.176 sec. respectively for almost cases. Ground motion to the structural frame is an artificial one with a response spectrum corresponding to the lower seismic design level in Japan.

 Response histories are shown to confirm the characteristics of responses of SS and phases of effects of inertia and relative displacements. Peak sectional forces along the height of SS are shown. Variations in those peak values due to the change of the natural period of structural frame and SS are shown in spectral form.

4. Conclusion

 The results of this paper are summarized as follows.

 (1) A modal analysis method has been derived.

 (2) Characteristics of the responses of SS such as pseudo-static responses have been confirmed.

 (3) The primary mode of SS is dominant in responses by inertial effects.

 (4) Even if the natural frequency of SS is increased by changing the boundary condition from pin-ends to fixed-ends, it may be impossible to decrease seismic responses due to the effect of relative displacements.

 (5) Because forces due to the effects of inertia and relative displacement are often in-phase, both effects should be appropriately combined in design.

 (6) Seismic responses of SS increase with increase or decrease its natural frequency.

 (7) While seismic responses of SS with pin-ends decreases as the natural frequency of the structural frame decreases, those with fixed-ends increase.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
43-51 , 
ISSN:
1340-4202

動吸振器効果を狙った大重量副振動系を有する制震架構の地震入力に対する汎用的な応答評価手法に関する考察 CiNiiでみる

著者名:
矢口 友貴  栗野 治彦 

抄録:

 The TMD (Tuned Mass Damper) is an effective structural control device that has been undergoing continuous development since the 1980's. However, in most situations, its mass has been limited to less than 1% of that of the entire building due to restrictions such as weight limitations and spatial difficulties. As a result, in early studies related to dynamic mass dampers, efforts were focused on how to compensate for the small mass ratio with active control technology. Although performance has been improved by hybrid control technology, devices for controlling structures during major earthquakes have not been put into use for a long while because of the problems of energy supply and stroke control. However, since the 2010's, there has been rapid development of TMDs that are effective against major earthquakes. Mass ratios of 5% have been successfully realized, and adopted in several actual existing high-rise buildings.

 Furthermore, recent studies have examined the utilization of a part of a structure's weight as a dynamic mass damper. Because a much larger mass ratio can be provided than a conventional TMD, these types of structures can potentially achieve superior seismic control. In addition, the response reductions of a main-system and a sub-system can be made compatible. The authors proposed a stroke control strategy and a practical response evaluation method based on response spectrum in a past study. However, although this strategy is effective in the initial stage of design, we pointed out that several features needed to be developed, such as accuracy of the stroke estimation against earthquake input, how to expand to complicated MDOF systems, and versatility for sub-system parameter fluctuations.

 This paper presents a response evaluation methodology for a seismic control structure that includes large-weight sub-systems as dynamic mass damper. The fundamental idea of the methodology is to consider the sub-system's stroke as amplification caused by the interaction with the main-system from that of the independent sub-system. First, the concept of the proposed response evaluation method based on a 2DOF model is introduced. Then the strategy for expanding the method to a MDOF system, including a system with multiple sub-systems, is presented. After conducting several examinations concerning the influence of the sub-system's parameter variation based on random vibration theory, practical expressions are derived that describe the relations between variation and response. Finally, the accuracy and validity of the proposed method are discussed through numerical analyses based on earthquake input.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
33-42 , 
ISSN:
1340-4202

終局時におけるSC杭の変形性能に着目した解析的研究 CiNiiでみる

著者名:
小原 拓  河野 進  浅井 陽一  木谷 好伸  後庵 満丸 

抄録:

 In the 2011 Tohoku earthquake and the 2016 Kumamoto earthquake, some buildings were demolished because of damages to precast concrete piles near the pile head. In Japan, superstructures are designed using working stress design for intermediate earthquakes and a lateral load carrying capacity check for severe earthquakes. However, substructures are not required to be designed for severe earthquakes and the structural performance of piles in terms of moment capacity, shear capacity, and ductility after yielding of members is not clear. For better seismic performance, steel-encased precast concrete piles (hereafter, SC piles) are often used at the pile head in low and mid-rise buildings in Japan. Extensive experimental works have been conducted recently to study the flexural performance of SC piles i.e. moment capacity and curvature. However, the study of numerical model which includes the effect of steel buckling is not investigated when SC piles have high axial force. In this paper, the numerical analysis by using multi-spring model (hereafter, MS model) was conducted to reproduce the experimental results of five SC piles with axial force ratio, 0~0.35. It was also clarified the drift angle at ultimate condition by using the simplified formula based on concrete ultimate strain, neutral axis depth and plastic hinge length.

 Lateral load – drift angle relations were well simulated with the numerical model by MS model until ultimate capacity. In analysis, ultimate capacity tended to reach when concrete crushing happened. The modelling of steel buckling was important to reproduce the hysteresis loop with high accuracy. The ratio of experimental and numerical maximum shear force was 1.02~1.08 except for the positive direction of specimen SC6. In the drift angle at 95% times maximum capacity defined as ultimate capacity, analytical results had good agreement with experimental results. The equation on AIJ guidelines was also shown to compare with ultimate capacity in the tests. In all specimens except for the specimen SC7, the calculation underestimated experimental values and this equation was found that it is not able to apply for SC7, which is small steel thickness.

 In this study, the revised simplified equation was also shown to reproduce the ultimate capacity. The revised equation was simplified and consisted of concrete ultimate strain, neutral axis depth and plastic hinge length. Concrete ultimate strain and plastic hinge length were the same value with MS model. Neutral axis depth was calculated by the regression equation considered the effect of axial force ratio. As the results, the computation of ultimate drift angle was able to reproduce experimental results. However, this computation tended to overestimated the test result of SC6, which is high axial force ratio, 0.35.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
117-126 , 
ISSN:
1340-4202

異形鉄筋の交差溶接接合性能に及ぼす溶接条件の影響 CiNiiでみる

著者名:
岡田 健良  高橋 辰弥  金久保 利之 

抄録:

 1. INTRODUCTION

 The authors have developed the footing beams in double layered main bars with cap-tie system and cross-welding joint between main bars and stirrups. However, welding conditions in cross-welding joint have not been sufficiently clear. The objectives of this study are to investigate the influence of welding conditions on welding strength and fracture patterns and to evaluate the structural performance of beam specimens with the parameters of welding conditions.

 2. WELDING STRENGTH TEST OF CROSS-WELDING JOINT

 The welding strength test using cross-shaped specimens is experimentally investigated. The test parameters are the combinations of reinforcing bars and the welding conditions. The bars of D16, D19 and D22 are selected as main bars, and D10, D13 correspond to stirrups. In the first series test, electric current (11,500 - 16,000A) and energization time (5 - 30cycle) are varied. As the results, three types of fracture patterns are observed (weld peeling, welding point breakage and breakage of base bar). In the case of D10 stirrup, the welding strength exceeds the yield strength of base bar by integrated current of over 4000A・s, and breakage of base bar is observed by integrated current of over 6500A・s. In the case of D13 stirrup, the welding strength exceeds the yield strength of base bar by integrated current of over 5000A・s.

 In the second series, electric current (10,000 - 18,000A) and welding pressure (3 - 7kN) are varied. As the results, the welding pressure has little influence on welding strength and fracture patterns. The energization time of 20 or 26cycle is not enough to avoid weld peeling for the combinations of D16, D22 main bar and D13 stirrup.

 3. LOADING TEST OF BEAM SPECIMEN

 In order to confirm the structural performance of the footing beams (main bars and stirrups are welded), the anti-symmetrical cyclic loading test for actual-size beam specimens is conducted. The test parameters are conditions of welding and the target concretestrength. All specimens are designed to show shear failure before flexural yielding of main bars to evaluate the shear capacity. The electric current and energization time is set to 13,000A and 30cycle for specimens No. 1-1 and No. 1-4, respectively, to have enough welding strength (breakage of base bar, called A-Type). The electric current for specimens No. 3-3 and No. 3-4 is set to 7,000A to show weld peeling (called B-Type). As the results, the maximum load and initial stiffness of A-Type specimens show similar or higher ones comparing with those of conventional beam specimens. B-Type specimens show the remarkable decrement of shear force after the loading cycle of 1/33 rad. The maximum loads ofA-Type specimens can be evaluated by shear capacity calculated by the conventional method.

 4. CONCLUSIONS

 1) The cross joint strength of reinforcing bars by flash butt welding increases as the integrated current also increases.

 2) The integrated current by which the sufficient joint strength can be obtained differs by the combinations of main bars and stirrups.

 3) The beam test results indicate that the maximum load and stiffness of A-Type specimens show similar or higher ones comparing with those of conventional beam specimens.

 4) B-Type specimens show smaller stiffness and the maximum load and remarkable decrement of shear force after the maximum.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
127-134 , 
ISSN:
1340-4202

ガスケットのリップ部の簡易水密性評価法の提案 CiNiiでみる

著者名:
塚越 雅幸  冨永 雄悟  上田 隆雄  川端 芳英  中山 一秀 

抄録:

 In this study, watertightness performance of gaskets used as sealing members for glazing, such as curtain walls, was investigated. There are various shapes of gaskets, but this study focuses on a general commercially available gasket used in building construction work that consists of a part for fixing the glass and ensuring watertightness. A gasket is sandwiched by the glass and the frame, and the reaction force provides watertightness performance and a fixing force of the glass. A simple watertightness evaluation test method of the lip part of gasket was proposed. In the proposed simple watertightness evaluation test method, watertightness performance of the lip part of the gasket was examined by applying a negative pressure corresponding to wind pressure acting on a building's wall during a typhoon, and visually observing the water leakage. In addition, change in pressure applied, that is, the rate of pressure decrease due to water leakage, was measured. Intensity of negative pressure and lip pressure of the gasket were used as parameters for the experiment. Effect of degradation over time of the gasket was also considered as a factor to reduce watertightness performance of the lip part. Since the gasket's material was EPDM, gasket specimens under lip pressure were exposed to a high temperature environment (100℃) as an accelerated degradation test.

 When the gasket was installed following specification design, water leakage did not occur, even though a pressure of -2.0 kPa corresponding to a wind speed of 36 m/sec simulating a typhoon was subjected to it. However, when a stronger simulated typhoon pressure of -3.0 kPa was applied, water leakage was observed at the lip part. Water leakage occurred earlier when deformation of the gasket was less than the specification design condition assuming errors such as glass and frame size. The gasket material tended to harden with deterioration over time, and the greater the residual deformation, the earlier water leakage occurred. An approximate curve of the reduction rate of negative pressure in the vessel during the test was created, and the coefficient of reduction rate of negative pressure in this equation was defined as the water tightness constant.

 As a result, it was found that water tightness constant decreased exponentially with a decrease in lip pressure caused by deterioration of gasket and errors in glass and frame shape, overall a slight change in lip pressure had a significant effect on water tightness performance. Since water tightness performance showed a high correlation with lip pressure, stress around the lip part of the gasket was analyzed using FEM. From results of FEM analysis, lip pressure was estimated to be 0.67 N/cm in the gasket with residual deformation due to deterioration over time. This value was about half that of a sound gasket's condition. It was calculated that if the gasket had deteriorated, reduction rate of pressure would be about 13 times as fast as that of a sound gasket when a negative pressure of -3 kPa was applied. As described above, when residual deformation due to deterioration occurred, lip pressure was reduced and watertightness performance was greatly compromised. Therefore, it is desirable to design a gasket shape that takes into account the effects of deterioration of the gasket.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
1-9 , 
ISSN:
1340-4202

摩耗促進試験機の実在建築物床への適用性の検討:摩耗による床のすべり抵抗の変化の即時推定方法に関する研究 その3 CiNiiでみる

著者名:
福田 眞太郎  工藤 瑠美  藤井 佑太朗  横山 裕 

抄録:

 Floor slip resistance is one of the important performances of floor for daily safety of building users. About floor slip resistance, an evaluation method based on Coefficient of Slip Resistance: C.S.R is established by Ono et al. Recently, C.S.R is widely used for designing or choosing floor material to building floor. However, this is based on measurement result by unused floor material. There are many floor materials which are easy to change slip resistance by influence of people walking abrasion. In order to secure safety of slip resistance after used in building floor, it is necessary to establish prediction method of changing slip resistance by walking abrasion.

 In previous study, abrasion acceleration machine has been developed. This machine have abrasion piece with polishing cloth mounted on wheel, and abrasion is acceleration as the wheel rotate and the abrasion piece rubs floor surface. By laboratory experiment, it has been revealed that this machine can reproduce changing slip resistance of 40, 000 steps of simulated walking by wheel rotating 600 times for 30 minutes. However, relationships between abrasion burden at actual building floor and abrasion burden by the machine have not been investigated. Therefore, there is lack of data in order to predict life-time of floor material from a viewpoint of slip resistance.

 In this study, applicability of abrasion acceleration machine for actual building floor was investigated. Method and procedure of research in this study is shown below.

 1) By measuring C.S.R for floor materials in actual building floors, changing slip resistance by daily using is grasped. And abrasion burden of the floor materials such as number of the building users is also grasped.

 2) Relationships between abrasion burden and changing slip resistance by the abrasion acceleration machine are grasped by using test specimen which is same floor materials as 1) and unused condition.

 3) Applicability of the abrasion acceleration machine for actual building floor is confirmed by comparing results of 1) and 2). And relationships between abrasion burden at actual building floors and by the machine are grasped.

 We chose as research objects 3 floor materials: Floor-sign-sheet, resin convex attached floor, anti-slip coating floor. These satisfy all following conditions.

 ・It has construction example at actual building floors. And number of days used and users a day can be grasped.

 ・It is available of unused condition floor mat

 ・It is easy to change slip resistance by walking abrasion.

 Finally, following results are clarified in this study.

 1) In 3 floor materials, changing slip resistance in actual building floors have been roughly in agreement with changing slip resistance by abrasion acceleration test. In other words, the abrasion acceleration machine can apply for actual building floor with a high probability.

 2) Equivalent number of the machine rotations to 10,000 users walking was calculated and it was classified for each user behavior. As a result, areas where users stand for a short time and turn have significantly more abrasion burden than areas where users walk simply.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
11-20 , 
ISSN:
1340-4202

柱脚が曲げ降伏する鉄筋集成材柱の弾塑性性状に関する実験的研究(その1):長方形断面柱の水平加力実験 CiNiiでみる

著者名:
塩屋 晋一  伊集 貴洋  大田 崇央  春口 綱慶 

抄録:

 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.

 This study focuses a hybrid glulam timber with steel deformed bar (rebar) and Epoxy resin adhesive.

 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.

 The result of loading test and its discussion are summarized as follows:

  (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.

 (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.

 (iii) The hysteresis loops, indicated spindle shape with no pinching and abundant energy dissipation as never observedin RC columns.

 (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.

 (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.


出版年月日:
2021 , 
巻:
86 , 
号:
779 , 
ページ:
107-116 , 
ISSN:
1340-4202

STUDY ON SHAPE FACTOR FOR CALCULATING SHEAR DEFORMATION(STUDY ON SHAPE FACTOR FOR CALCULATING SHEAR DEFORMATION) CiNiiでみる

著者名:
小野里 憲一 

抄録:

出版年月日:
2020-12 , 
巻:
, 
号:
778 , 
ページ:
1687-1687 , 
ISSN:

挿入型鉄筋定着工法の構造性能 その2:小支圧板を有する後付け定着筋の定着性能 CiNiiでみる

著者名:
杉山 智昭  小野 英雄  五十棲 雄高  渡辺 英義 

抄録:

 In the case of repair and reinforcement of an R/C structural frame, and installation of new members for extension and reconstruction, it is necessary to anchor such as main bars and wall reinforcement bars of new members to the existing frame. In this case, the anchor is required to reliably transfer the tension of the rebar to the existing frame. The purpose of this research is to propose a post-installed headed rebar anchor method with high reliability both in structural performance and workability, and to evaluate the anchorage performance of the method.

 In the second part of this paper, experiments in a relatively long embedment length were carried out to clarify the effects of factors such as the concrete edge distance and the number of anchors for the bond behavior of the rebar and the bearing behavior of the small headed plate. The long embedment length assumes a situation where bond deterioration near the joint surface (near the load end) and bond resistance in the length direction shift for actual use.

 The following results were obtained.

 (1) The bond strength on rebar surface of proposed method is equal to or higher than that of the cast-in-place deformed bar under the seismic load and the long-term load. The small headed plate is useful for ensuring uniform bond resistance over the entire length of the embedment length and contributes to an increase in anchor strength due to bearing resistance.

 (2) Bond strength decreases when anchoring near the concrete edge or multiple rebars are close to each other, but by using a long anchoring length, it is possible to ensure the tensile strength of the anchoring bars. In addition, there is no difference in performance depending on the construction direction.

 (3) It can be said that the bond strength on rebar surface of this method is estimated to the allowable bond stress of AIJ reinforced concrete calculation standard and bond strength of AIJ design recommendation for composite construction. The small headed plate contributes 10 to 30% increase in anchor performance.

 (4) Anchorage behavior due to long embedment length can be simulated by reducing local bond strength in consideration of a concrete cone failure strength and edge and group effects.


出版年月日:
2020-12 , 
巻:
, 
号:
778 , 
ページ:
1587-1597 , 
ISSN:
1340-4202