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1.
【目的】为探明胶合木-钢夹板螺栓连接的动力性能和抗震性能,确保连接件在车辆、机械振动等动力荷载下的可靠性。【方法】针对胶合木-钢夹板螺栓连接的构造特点,考虑胶合木厚度和螺栓直径之比(厚径比)、螺栓顺纹间距、螺栓并列和错列布置方式等参数的影响,设计制作了4类13组共39个胶合木-钢夹板螺栓连接件,在低周反复荷载作用下进行滞回性能试验。【结果】试验结果表明:在单螺栓连接中,连接部位的破坏模式逐渐由"螺栓刚直"向"双铰"转化,胶合木销槽破坏模式逐渐由销槽整体承压破坏向两端部挤压破坏转变,试件滞回曲线基本都呈现饱满的弓形和棱形,具有良好的耗能能力和抗震性能,但其承载能力较低。在多螺栓连接中,螺栓和胶合木的破坏模式分别以"双铰"破坏和销槽端部挤压破坏为主,试件滞回曲线均呈现饱满棱形,该类试件在承载能力、抗震性能和耗能能力上均有大幅提升;随着螺栓顺纹间距的增大,试件的承载能力不断增大,但螺栓顺纹间距在200 mm时,极限荷载增幅趋于平缓,初始刚度增涨大幅放缓,且整体刚度退化与螺栓顺纹间距为250 mm时基本相同;螺栓并列布置滞回曲线饱满程度好于错列布置;螺栓双排布置承载能力比单排布置的承载能力更高,刚度退化更小。【结论】胶合木-钢夹板螺栓连接具有较好的耗能能力、抗震性能及延性性能;螺栓顺纹间距在200 mm时,抗震性能最佳;螺栓错列布置的抗震性能比并列要好,螺栓双排布置的抗震性能更优越。 相似文献
2.
Under varying climate conditions, cracks are commonly observed in bolted joints, owing to the shrinkage of wood and confinement from slotted-in steel plates and bolts. A three-dimensional finite element model was developed to investigate the mechanical behavior of bolted glulam joints with initial cracks. Wood foundation was prescribed in the model to simulate the local crushing behavior of wood surrounding the bolts. The behavior of wood in compression and the foundation were defined as transversely isotropic plastic in the software package ANSYS. Cohesive zone model was applied in the numerical analysis to consider the propagation of initial cracks and brittle failure of wood in the bolted joints under tension load. The numerical model was validated by the experiments conducted on full-scale specimens and it is indicated that the numerical model has good ability in predicting the failure modes and capacity of tension joints with local cracks. To further investigate the influence of crack number, length and locations, a parametric study was conducted with the verified model. Moreover, to study the effects of cracks on the behavior of bolted joints with different failure modes, another bolted joint including bolts with different strength grades and diameters was designed and analyzed in the parametric study, which was expected to have bolt yielding failure mode. It was found that the initial cracks can decrease the capacity and initial stiffness of tension joints by up to 16.5 and 34.8%, respectively. 相似文献
3.
Summary A previously developed model to predict the load-slip relationship for mechanical joints using one bolt subjected to lateral loading (Part 1) was extended to incorporate the rotational resistance of joints containing two bolts. The rotation is about the long axis direction of the bolts, and considers the wood members oriented at arbitrary angles to the grain. The model utilizes nonlinear translational springs to represent the parallel and perpendicular to grain components of the reaction force present on each bolt resisting the applied moment. A series of experiments were conducted to determine the spring constants of bolted joints in axial loading and to verify the predictions of the mathematical model. Bolted joints subjected to a pure rotation were tested using combinations of steel plates and wood side members experiencing bolt reaction forces at various angles of load to grain. The results indicated an excellent agreement between theoretical predictions and experimentally obtained data.The authors wish to extend thanks to the Colorado State Agricultural Experiment Station for their financial support and to the Fulbright-Hayes Foundation for the educational scholarship and research funding provided to the project 相似文献
4.
5.
Bond quality and joint performance between laminated veneer lumber (LVL) and metal plates were investigated. Commercially fabricated LVL made of Douglas fir veneer and bonded with phenol-formaldehyde resin as well as three types of epoxy adhesives were used. Various surface preparations and treatments were applied to ordinary steel, stainless steel, and aluminum plates to remove the weak boundary layer that is incompatible with the resin and form a stable adherend layer that is chemically and mechanically compatible with the resin. Small specimens were tested in shear to search the most suitable metal surface for bonding with LVL. Generally, shear strength obtained for the specimens bonded with aluminum plates was lower than those bonded with ordinary steel plates. Among them chemically treated (ChT) and roughened (R) surfaces have demonstrated superior performance. To investigate strength performance and bond quality, LVL beams jointed with metal plates were tested while bending. The best results were obtained for specimens bonded with zinccoated metal plates, though good results were obtained also for ChT and R plates. However, the fracture proved to be fragile when no drift pins were used, even for high-performance surface treatments. The usage of drift pins was necessary to add toughness and avoid the brittle status of the fracture. 相似文献
6.
This paper presents research on plywood frame corners jointed to glulam beams and columns by means of glued-in hardwood dowels. The frame corner was made of a solid block of ordinary plywood of the same width as the glulam beams and with plies parallel to the plane of the frame to avoid splitting due to stress perpendicular to the grain. Hardwood dowels with a diameter of 12mm and a maximum glued-in length of 120mm were glued into drilled holes in the plywood corner and glulam beam ends parallel to the grain direction of the beams to form a momentresisting joint. Static bending tests were conducted of frame corners with 100 X 200mm2 and 120 X 420mm2 beam cross sections. Bending capacities of the joints corresponding to a modulus of rupture of the jointed glulam beams of about 30MPa were obtained for both closing and opening moments for the small cross sections, and about 22MPa was obtained for the large cross sections. Simple design models for calculation of joint strength and rotational stiffness are also presented. 相似文献
7.
The shear strength of dowel-type timber connections with multiple slotted-in steel plates was estimated based on European
yield theory. The values calculated based on the yield theory were compared with experimentally obtained results. An experiment
was performed on dowel-type timber connections with two and three slottedin steel plates under lateral loads parallel to the
grain. The yield mode of the dowel-type connection assumed in this study corresponds approximately to the failure mode of
the connection obtained from the experiment. The shear strength of the dowel-type connections calculated based on the yield
theory showed good agreement with the results for shear strength obtained in the experiment. The yield theory was useful for
estimating the shear strength of the doweltype connection with multiple slotted-in steel plates. The shear strength of the
dowel-type connection was greatly affected by the spacing of the steel plates, the number of steel plates, and the timber
thickness. The values of these parameters that showed the proper shear strength of the dowel-type connection could be estimated
based on the yield theory.
Part of this paper was presented at the 9th Timber Engineering Forum of the Japan Timber Engineering Society, December 2005 相似文献
8.
Ali Awaludin Takuro Hirai Toshiro Hayashikawa Yoshihisa Sasaki Akio Oikawa 《Journal of Wood Science》2008,54(2):114-120
The adoption of a concept similar to the prestressing technique used in laminated wood decks of bridge structures might increase
the initial stiffness or ultimate resistance of dowel-type timber joints by applying pretension to their bolts. This study
investigated the effect of pretension in bolts on hysteretic responses and ultimate properties of moment-carrying timber joints
with steel side plates. A pretension of 20 kN that yielded a prestress level of 1600 kPa or about 90% of the allowable long-term
end-bearing strength of spruce species was applied to the bolts of prestressed joints. The superiority of the prestressed
joint over the non-pre-stressed joint was proved by very high hysteretic damping, equivalent viscous damping ratio, and cyclic
stiffness. At any given rotation level, hysteretic damping reduction and moment resistance decrement due to continuously reversed
loads were found to be small because bolt pretensioning minimized the pinching effect. This study showed that the hysteresis
loop of the prestressed joint can be obtained by adding the frictional hysteresis loop due to pretension force into the hysteresis
loop of the non-pre-stressed joint. Despite a great increase of initial stiffness, only slight increments in ductility coefficient
and ultimate moment resistance were found in the prestressed joint. 相似文献
9.
Glued laminated timbers (glulam) or planks 50mm thick were added to structural steel columns and beams as covering materials. The wood used in the glulam was sugi (Cryptomeria japonica D. Don) laminated with resorcinol resin adhesive between woods and epoxy resin adhesive between wood and steel. The 50mm thick planks of sugi around the steel were fixed with spirally threaded nails (screws), and 25mm long wood plugs were used to cover the tops of the nails. The 50mm thick glulam showed 1h of fire resistance. The temperatures of the flanges and webs of steel were 100°C at 1h and 200°C after 4h. The epoxy resin used to bond the wood and steel was an appropriate adhesive from a recycling perspective because it is easy to separate or peel from the steel. 相似文献
10.
Ali Awaludin Takuro Hirai Toshiro Hayashikawa Yoshihisa Sasaki 《Journal of Wood Science》2008,54(5):362-368
Previous experimental studies reported that bolt pretensioning greatly increases the initial stiffness and load-carrying capacity
of bolted joints. It is also a matter of great importance to structural designers to understand the effect of pretension on
the load-carrying capacities of bolted joints, and this study presents an extended yield model that considers the fastener’s
pretension force. In the extended yield model, the load-carrying capacity was defined as the load at a slip of 15 mm. The
ultimate fastener bending angle at the yielded cross section equivalent to this joint slip, which was affected by the fastener’s
axial force, was iteratively evaluated in numerical analyses. The introduction of bolt pretensioning largely increased the
joint slip resistance at initial loading, but it decreased the ultimate fastener bending angle. This decrease of fastener
bending angle resulted in a relatively low stiffness hardening (or secondary stiffness), which is caused by secondary axial
forces associated with embedment of steel plates into the wood member. Prediction was verified by the tests of 36 steel-to-timber
joints under three different pretension forces and two loading directions relative to the grain. Some of the observed load-carrying
capacities of the joints, particularly in loading perpendicular to the grain, however, were not as high as those expected
by the numerical analyses considering the given pretension forces. 相似文献
11.
Yasushi Nakashima Masaki Harada Tomoyuki Hayashi Masahiko Karube Tadashi Higashino 《Journal of Wood Science》2006,52(1):44-50
To study the shear strength of structural joints in sugi (Cryptomeria japonica D. Don) — Japanese larch (Larix kaempferi Carriere) composite glulam beams using structural connectors with double shear plates, shear tests were conducted on two
types of joint (post-beam and girder-beam). Two types of the composite beam (240 and 300 mm depth) were prepared for the tests.
Ordinary sugi glulam beam and Japanese larch glulam beam were also used as control specimens. The load—displacement curves
of joints in composite beams were somewhere between those of sugi and Japanese larch glulam beams. The shear strength of joints
in composite beams was higher than that in the sugi glulam beam control. However, the allowable loads of the joints in composite
beams were lower than those in the sugi beam with 240 mm depth. Large variation of maximum load of the joints in the composite
beams resulted in lower allowable load. 相似文献
12.
13.
为准确评价斜螺钉连接钢 木节点的剪切性能,探明其受力机理,以云杉胶合木、钢板和自攻螺钉作为研究材料,测试不同荷载方向与受力情况下斜螺钉连接节点的承载性能,将试验数据与国外规范中的计算模型进行对比,提高了侧边钢板 胶合木(钢 木)斜螺钉连接节点承载性能的预测能力。结果表明:自攻螺钉与剪切面之间的角度变化对其在钢 木节点承受剪 压复合应力的承载力影响不明显,当偏转为剪 拉复合应力时,节点承载力明显增大,并在30°~45°获得最大值;剪 压复合应力时,现行EC5公式计算剪 压节点的极限承载力非常不安全;EC5的刚度预测结果在剪 压复合应力区和垂直剪切面钉入时,与试验值吻合度很高,但对剪 拉区节点的滑移模量没有预测性;将Tomasi模型应用于斜螺钉连接钢 木节点滑移模量理论计算时,在45°~90°时与试验值吻合度极高。单颗自攻螺钉的抗拔刚度计算节点滑移模量的方法极为有效,具有较高的借鉴意义。 相似文献
14.
In this research, technological properties of glulam beams made from hydrothermally treated poplar (Populus deltoides) wood were investigated. Poplar wood blocks with dimensions of 6 (r)?×?10 (t)?×?73 (l)?cm3 were cut and hydrothermally treated in a stainless steel reactor at temperatures of 140 and 160°C for a holding time of 30?min. The treated wood blocks were initially air seasoned and then they were dried in a semi-pilot scale vacuum dryer to achieve moisture content (MC) of 12%. Conditioning of the treated and the untreated wood blocks was done prior to adhesive bonding. Afterwards the glulam beams (4 ply) were manufactured using polyurethane. In order to evaluate the physico-mechanical properties of the beams, density, equilibrium moisture content, water repellent effect (WRE), anti-swelling effect (ASE), mass loss (ML), wettability as well as surface roughness due to the hydrothermal treatment were determined in the treated wood and delamination, bond shear strength, tensile strength, MC and moisture-induced stresses as well as strains in cross-section of the beams were determined in the glulam beams. The results revealed that density, ML, ASE, WRE, modulus of elasticity, modulus of rupture and delamination were increasing and the others were decreased due to the hydrothermal treatment. 相似文献
15.
Koji Adachi Katsuhiro Takehira Tomoaki Soma Masafumi Inoue 《Journal of Wood Science》2010,56(6):502-506
The withdrawal strength of a bolt-nut connector made from wood-based material was evaluated. The thread strength of the wooden
bolt-nut connector was tested to select various parameters of the connector and the type of wood material; the wood materials
tested were hard maple, white oak, ebony, glue-laminated bamboo, and densified Japanese cedar. A plane model of wooden threads
with various thread angles was also evaluated. The results showed that the maximum failure load of the thread increased with
increasing bolt density and connection area, which was calculated from the diameter of the bolt and the thickness of the nut.
The withdrawal resistance after reaching the maximum load underwent a graded decrease because the bolt threads were broken
one by one. In addition, the thread strength depended on the thread angle. In the model with a thread angle of 90°, compressive
deformation in the transverse direction occurred prior to shear deformation along the root of the threads; the model with
this thread angle thus had higher strength than those with other angles. 相似文献
16.
《Wood material science & engineering》2013,8(2):88-98
ABSTRACTA glued-in rods' connection is generally constituted by a group of steel bars bonded by an adhesive into timber elements. In the past, most of the research focused on single-rod connections, in order to exploit the maximum resistance of the connection without accounting for interaction among bars or splitting failure in the timber member due to close edge distances or spacing between bars. Such interaction problems arise when dealing with multiple rods, thus requiring specific investigation to fully understand the behavior of the connection as a whole and to determine its capacity. In both cases, existing test procedures determine bond strength in specific geometrical configuration. The paper aims to determine the pull-out strength of single and multiple axially loaded steel rods bonded in glulam parallel to the grain differentiating the adhesive failure from the other failure modes. After an initial review of typical applications and existing design procedures, test results on single rod with confined or unconfined test setup on single rod at different embedment depths are presented and discussed, indicating that the confinement has a negligible influence on the pull-out capacity. Subsequently, interaction between bars is investigated by a specific unconfined configuration. The accounted parameters are the embedment depth of the bars, the dimensions of the timber section, and the spacing between bars. Results are discussed and compared with three-dimensional numerical simulations. Both experimental and numerical results suggest that the critical value at which the transition from pull-out to timber-related failure is observed depends on the mechanical properties of the timber and on the properties of the adhesive, such that a single value of spacing should not be provided in design standard if the full capacity of the adhesive is to be exploited. 相似文献
17.
Summary A nonlinear superposition model was developed to assess the load-slip behavior of bolted joints consisting of a single bolt subjected to lateral loading at angles of load to grain. This model characterizes the bolted joint as a pair of orthogonal nonlinear springs aligned parallel and perpendicular to the grain of the wood members. The spring stiffnesses are quantified by a logarithmic or exponential function depending upon whether the connection softens or stiffens with increasing slip. The spring deformations are superimposed to determine the movement of each component of the connection. Deformations of connected members are added vectorially to determine their relative displacement. Spring constant were determined experimentally using metal-to-wood connections. Thick steel side plates were employed to limit the system deformation to the wood component. Wood members were evaluated at angles of load to grain ranging from zero to ninety degrees. Once the spring constants had been determined, the model was executed to predict the load-slip behavior of wood-to-wood connections. These predictions were compared to experimentally obtained load-slip values. The results indicate that the nonlinear superposition concept is a valid approach to predict joint deformation at angles of load to grain.The authors express their gratitude to the Fulbright-Hays Foundation and the Colorado State Agricultural Experiment Station for their financial support of this study 相似文献
18.
Summary This paper describes a modelling approach to predict the behaviour of an elementary thin timber bolted joint. The application
concerns principally joints with steel side members; bolts have a constant 12 mm diameter with two ratios of end distance
to bolt diameter and two bolt clearances. The behaviour of the bolted joints is characterized by a double non linearity; the
first one is due to the contact area evolution between the bolt and the hole of the jointed elements. The second one is owing
to the evolution of plasticity on the wood. A spring element compatible with isoparametric plane finite elements represents
the contact evolution. The elastic-plastic wood is provided with a plastic flow rule according to the Tsa? criterion. This
study allows an investigation on the parameters characterizing the Tsa? criterion, particularly F12 which represents the interaction between the principal axis of orthotropy. A two-dimensional model is used. It permits the
assessment of the clearance bolt, joint dimensions, wood plasticity and wood grain angle effect on the joint behaviour. The
wood grain angle has a non negligible effect on the plastic strains distribution and it can create a parasite loading because
the joint tends to rotate even for an axial loading. The results showed a good agreement between experimental values given
by some authors and numerically-predicted stresses on the joint. So, the applications concern a two-dimensional joint with
anisotropic plastic material. The generalization in the three-dimensional modelling is desirable to take into account the
interaction between the wood and a metallic fastener in thick joints with different geometric characteristics. 相似文献
19.
Tomoyuki Hayashi Masahiko Karube Kouji Harada Toshihiro Mori Tomonori Ohno Kohei Komatsu Yasuo Lijima 《Journal of Wood Science》2002,48(6):484-490
A research project supported by the Japan Wood Working Machinery Association has been conducted since 1999 to examine the feasibility of sugi (Cryptomeria japonica D. Don) composite glulam beams reinforced with Douglas fir (Pseudotsuga menziesii Franco) lamination. This study, part of the project, was concerned with the strength properties of timber joints composed of composite glulams using newly developed structural steel connectors. Two types of beam were prepared: 10 plies (inner 6 plies sugi, outer 4 plies Douglas fir) and 8 plies (inner 4 plies sugi, outer 4 plies Douglas fir). Two types of structural steel connector, Haratec and Standard, were used for joining the beam with a post or a girder. The relation between load and deformation of the joints was represented as a typical nonlinear curve. Initial stiffness and maximum load of the joint composed of the composite glulam were in the range between those of sugi and Douglas fir. Strength properties of the joints varied with three variables: type of connector, depth of the glulams, and the type of joint. Thus, the allowable loads for the connectors should be determined for each combination of these variables. 相似文献