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1.
《Wood material science & engineering》2013,8(6):392-403
ABSTRACTCross laminated timber (CLT) is a wood panelling building system that is used in construction, e.g. for floors, walls and beams. Because of the increased use of CLT, it is important to have accurate simulation models. CLT systems are simulated with one-dimensional and two-dimensional (2D) methods because they are fast and deliver practical results. However, because non-edge-glued panels cannot be modelled under 2D, these results may differ from more accurate calculations in three dimensions (3D). In this investigation, CLT panels with different width-to-thickness ratios for the boards have been simulated using the finite element method. The size of the CLT-panels was 3.0 m × 3.9 m and they had three and five laminate layers oriented 0°–90°–0° and 0°–90°–0°–90°–0°. The thicknesses of the boards were 33.33, 40.0, and 46.5?mm. The CLT panel deformation was compared by using a distributed out-of-plane load. Results showed that panels with narrow boards were less stiff than wide boards for the four-sided support setup. The results also showed that 2D models underestimate the displacement when compared to 3D models. By adjusting the stiffness factor k88, the 2D model displacement became more comparable to the 3D model. 相似文献
2.
Pseudodynamic (PSD) lateral loading tests were conducted on conventional post and beam timber frames with plywood-sheathed
shear walls to validate the dynamic model of wall panels, each with an opening of a different configuration. The lateral forces
were applied step by step at the top of the wooden frames by the computer-controlled actuator, and the displacement response
for the next step was computed on the basis of the input accelerogram of the 1940 El Centro earthquake scaled up to 0.4g. The test results were compared with those of the lumped mass time-history earthquake response analysis using the hysteresis
model with pinching. The results of the dynamic analysis with this global model consisting of the envelope curves, unloading
and reloading with pinching agreed well with the experimental results of the PSD tests of this type of earthquake record.
Some parametric studies may be necessary, however, to validate the model with different earthquake records. The hysteretical
parameters obtained in this study showed similar values for each of the wall panels with different opening configurations.
This makes it possible to use the model and parameters for the plywood-sheathed shear walls to estimate the dynamic behavior
of entire structures without conducting expensive PSD tests or shaking table tests. 相似文献
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Wood-based panels are subjected to cyclic panel shear load caused by wind and seismic forces in such an application as the sheathing of bearing walls. The fatigue behavior of structural plywood under panel shear load with two different loading frequencies was examined. Pulsating panel shear load with a triangular waveform and loading frequency of 0.5 or 5 Hz was applied to the plywood specimens. Stress−strain hysteresis loops were measured throughout the fatigue tests. Fatigue life was highly dependent on loading frequency at more than 0.5 stress level. The deterioration of mechanical property and damage accumulation in plywood specimen was observed to be slower at higher loading frequency at more than 0.5 stress level. Analyses based on energy loss suggest that panel shear load with higher loading frequency causes less damage to the plywood specimen during one loading cycle at higher stress level, and that the fatigue damage accumulation causing failure might be dependent on stress level although it seems to be unaffected by loading frequency. Based on these results, a new fatigue failure model for plywood specimen was qualitatively developed by combining Weibull’s weakest link model and Daniels’ fiber bundle model. 相似文献
5.
In this study, the duration-of-load effect on the rolling shear strength of cross laminated timber (CLT), with different cross-sectional layups (five-layer and three-layer), was evaluated. A stress-based damage accumulation model is chosen to evaluate the duration-of-load strength adjustment factor of the rolling shear strength of CLT. This model incorporates the established short-term rolling shear strength of material and predicts the time to failure under arbitrary loading history. The model has been calibrated and verified based on the test data from low cycle trapezoidal fatigue tests (damage accumulation tests) in the previous study. The long-term rolling shear behaviour of CLT can then be evaluated from this verified model. As the developed damage accumulation model is a probabilistic model, it can be incorporated into a time based reliability assessment of the CLT products, considering short-term, snow, and dead load only loading cases. The reliability analysis results and factors reflecting the duration-of-load effect on the rolling shear strength of CLT are compared and discussed. The characteristic of this modeling theory lies in that the verified model is also able to predict the duration-of-load behaviour of CLT products under arbitrary loading history, such as long-term dead load case; then, these predictions of time to failure from the damage accumulation model can elucidate duration of load by the stress ratio evaluation approach. The results suggest that the duration-of-load rolling shear strength adjustment factor for CLT is more severe than the general duration-of-load adjustment factor for lumber; this difference should be considered in the introduction of CLT into the building codes for engineered wood design. 相似文献
6.
Pseudodynamic (PSD) tests were conducted on plywood-sheathed conventional Japanese three-dimensional (3D) wooden structures.
Lateral load was applied to the edge beam of specimen structures to generate eccentricity loading. Specimens were based on
a combination of shear walls with openings in the loading direction and horizontal diaphragms with different shear stiffness.
The principle deformation of the horizontal diaphragm was torsion for rigid diaphragms and shear deformation for flexible
diaphragms. Lumped-mass time-history earthquake response analysis was conducted on the tested structures, and additional calculations
were conducted on structures with different eccentricity rates. Dynamic analyses were conducted by varying the masses and
the resistance of the walls in the loading direction. The simulated peak displacement response in the loading plane agreed
comparatively well with the PSD test results. The maximum displacement response on changing the wall resistant ratio showed
almost the same tendency as that obtained by changing the mass ratio up to an eccentricity rate of 0.3; however, the maximum
displacement response increased markedly beyond an eccentricity rate of 0.4. It was proved that the lumped-mass 3D model proposed
in this study was appropriate for conducting a parameter study on the 3D dynamic behavior of timber structures. 相似文献
7.
A half-scale model of a light-frame shear wall was developed to evaluate the racking performance of a fullscale shear wall (prototype). The effect of nail size on the performance of the shear wall was also investigated using models constructed with three types of nail. Materials for the model were determined through experimental methods, which included nail-head push-through, stud-to-sheathing nail connection, and static bending tests. Materials with which the model was made to be in similarity to the prototype were three-layer 4.8-mm plywood, 39.72-mm long nails, and 1 × 2 lumber cut from 2 × 4 studs. In accordance with ASTM E 72 and ASTM E 564, racking resistance tests were conducted on 20 shear walls. The results showed that the maximum load capacities of the prototype walls could be evaluated by the model without significantly different failure modes. Tests on the effect of nail size revealed that increasing the nail head diameter may improve the performance of shear walls.Parts of this paper were presented at the International Conference on Effective Utilization of Plantation Timber (ICEUPT'99), Chi-Tou, Taiwan, May 1999; and the World Conference on Timber Engineering (WCTE2000), Whistler, Canada, July–August 2000 相似文献
8.
The performance of plywood-sheathed shear walls is determined at the plywood-to-timber joints. In joints with dowel-type fasteners, such as nails and screws, the fastener is fractured under reversed cyclic loading (e.g., seismic force), reducing the ductility of the joint. The fracture is caused by low-cycle fatigue due to the reversed cyclic bending of the fastener. Therefore, evaluating the fatigue life is important for estimating the ultimate displacement. The main objective of this study is to estimate the ultimate displacement of the joints and to enable load–displacement calculation of single shear joints under reversed cyclic displacement when bending fatigue failure of the fastener occurs. Single shear tests were conducted under different loading protocols, and the damage performances of the fasteners were determined by subjecting them to reversed cyclic bending tests. Based on the results, the failure lifetimes of joints with dowel-type fasteners were estimated. In addition, the fracture mechanism of these dowel-type fasteners was elucidated. CN50-type nails and wood screws with dimensions of 4.1?×?38 and 4.5?×?50 mm were used as fasteners. The single shear tests showed that the smaller the displacements per cycle, the lower are the ultimate displacement and ductilities of the joints. Moreover, load–displacement relationship up to fastener failure can be approximately estimated by combining the yield model and failure lifetime. 相似文献
9.
A sensitivity study was performed with a nonlinear elastic finite element model for monotonie analyses of wood-framed shear walls. The objective was to provide information about simplifying a model of wood-framed shear walls with no significant loss in accuracy. The simplifications concern features such as slips in joints between frame members, slips in hold-down connections, and bearing between adjacent sheathing panels. The results from analyses of a shear wall with an opening of window shape show that the effect of constraint by the bearing between sheathing panels and slips in frame joints on the overall stiffness of the wall is limited. Thus, there are great possibilities for reducing the calculation time by not taking these phenomena into account, avoiding an excessive number of degrees of freedom and iterations. The influence of the simplifications on the distribution of vertical reaction forces along the wall is more significant. Furthermore, if each simplification is introduced separately, the effect on the overall stiffness is greater. The difference, however, is less than 10%. The failing pattern of the nail connections is also clearly influenced by the simplifications when they are introduced separately. The results from the analyses show that slips in frame joints can be sufficiently represented by those in connection with the opening. 相似文献
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11.
Effect of element type on the internal bond quality of wood-based panels determined by three methods
Three mechanical tests with different loading modes were conducted to evaluate the effect of element type on the internal bond quality of wood-based panels. In addition to the internal bond test, which is commonly used for mat-formed panels, interlaminar and edgewise shear tests were used to test oriented strandboard (OSB), particleboard, medium-density fiberboard (MDF) of two thicknesses, and plywood. The following results were obtained. Epoxy resin proved to be suitable for determining the interlaminar shear modulus instead of hot-melt glue. There was a linear relation between panel density and interlaminar shear modulus and a linear correlation between the interlaminar shear strength and internal bond (IB) strength for the mat-formed panels tested. OSB had the highest edgewise shear modulus, and MDFs had the highest edgewise shear strength in this study. The modulus/strength ratio also depended on both panel type and loading mode. The relation between the shear moduli determined from the edgewise and interlaminar tests indicated the characteristics of the shear properties of panels made of different elements.Part of this paper was presented at the Fourth International Wood Science Symposium, Serpong, Indonesia, September 2002 相似文献
12.
Satoshi Sakuragawa Yoshifumi Miyazaki Tomoyuki Kaneko Teruo Makita 《Journal of Wood Science》2005,51(2):136-140
The effect of visual stimulation from wood on the body was examined in a comparative study using full-sized hinoki wall panels and a white steel wall panel. Continuous blood pressure measurements were used as the physiological indicator. Sensory evaluation by the semantic differential (SD) method and the profile of mood states (POMS) test were performed to determine changes in psychological impression. Results showed that visual stimulation from hinoki wall panels had an emotional and natural impression upon humans. Blood pressure decreased significantly in subjects who liked them, and there was no significant increase in blood pressure in subjects who disliked them. Visual stimulation from the white steel wall panel made an unhealthy and closed impression and increased the sense of depression. In addition, there was stress and a significant increase in blood pressure in subjects who disliked them. Consequently, visual stimulation from hinoki and white steel wall panels had different physiological and psychological effects. Results also showed that the same visual stimulation induced different physiological responses depending on the values of the individuals.Part of this paper was presented at the 48th Annual Meeting of the Japan Wood Research Society in Shizuoka, April 1998 相似文献
13.
The inter-storey drift limitations are meaningful reference values for structural seismic performance evaluation. This paper presents an analytical investigation into the seismic performance of multi-storey cross-laminated timber (CLT) structures to obtain the drift limitations under different earthquake hazard levels reasonably. The Pinching4 model was used to simulate the nonlinear mechanical behavior of three types of connections used in CLT structures, and a numerical model was further developed to capture the lateral load-resisting properties of CLT shear walls. Moreover, three benchmark multi-storey CLT apartment buildings were designed using the Equivalent Static Force Procedure according to National Building Code of Canada (NBCC), and simplified structural models were developed for these buildings. Depending on the results from numerous time-history dynamic analyses, the empirical cumulative distribution functions (CDFs) of the maximum inter-storey drifts were constructed for the three benchmark buildings. The probability of non-exceedance (PNE) of inter-storey drift thresholds under different earthquake hazard levels was proposed and validated. It is recommended that for low-rise CLT buildings within three stories, values of 0.30%, 0.75%, and 1.40% can be considered as the drift limitations for frequent, medium, and rare seismic hazard levels, respectively. For mid-rise or high-rise buildings without three stories, 0.25%, 0.70%, and 1.30% can be considered as drift limitations. 相似文献
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In the previous report of this ongoing study, results of an extensive field survey were collated and a theoretical model was
proposed to predict the mechanical behavior of timber shear walls of traditional design in Taiwan. The initial objective of
the present report was to propose a simplified calculation method for estimating the initial stiffness and yield strength
of traditional timber shear walls. Based on the results of the field survey, a total of 15 full-scale specimens were tested
to verify the theoretical model and simplified calculation proposed previously. Good agreement was found from comparison of
analytical and experimental results. The results of this study show that the friction behavior between board units and beams
plays the major role in resisting the lateral force applied on the timber shear wall, followed by the resistance supplied
by embedment. The resistance provided by bamboo nails is minor due to the small section. Another trend found was that for
set dimensions of a timber shear wall, the board width can be increased to obtain higher stiffness and strength of the shear
wall. 相似文献
16.
正交胶合木(CLT)在木结构建筑中应用越来越广泛,特别是在中高层建筑物中。CLT作为楼盖构件使用时,承受柱或墙体施加的垂直荷载,因此CLT产品的设计及应用需要其横纹承压弹性模量和强度方面的参数;改善CLT横纹承压性能,也可以提高整体结构强度和建筑安全系数。文中主要介绍目前CLT横纹承压性能测试方法,总结CLT横纹承压性能影响因素方面的研究进展,以期为国内CLT研究提供参考。 相似文献
17.
Tamami Kawasaki Kweonhwan Hwang Kohei Komatsu Shuichi Kawai 《Journal of Wood Science》2003,49(3):199-209
The fundamental in-plane shear properties were investigated for the wood-based sandwich panel of plywood-overlaid low-density
fiberboard (SW) manufactured at a pilot scale to develop it as a shear wall. The shear test method using tie-rods standardized
for shear walls was applied to SW with dimensions of 260 mm square and 96 mm thick as a small shear wall and to plywood (PW)
and thick low-density fiberboard (FB). The shear modulus and shear strength of PW, FB, and SW were determined. To measure
the shear deformation angle, a displacement meter and strain-gauge were used. The shear moduli of PW (0.68 g/cm3) and FB (0.25–0.35 g/cm3) were 460 and 21–58 MPa/rad, respectively. The shear modulus of SW as a composite was analyzed. Some experimental models
of SW were proposed (i.e., rigid-α, rigid-β, flexible, and semirigid models). The shear modulus of SW (0.35–0.40 g/cm3) evaluated based on the rigid-α and semirigid models were 73–89 and 109–125 MPa/rad, respectively. The theoretical shear modulus of SW was calculated to
be 110–129 MPa/rad.
Received: May 9, 2001 / Accepted: June 26, 2002
RID="*"
ID="*" Part of this report was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, Japan, April
2000; and the 5th Pacific Rim Bio-Based Composite Symposium, Canberra, Australia, December 2000
Acknowledgments The authors express our deep gratitude to Mr. Noritoshi Sawada (Hokushin Co.), Dr. Wong Cheng, and their cooperative members
for their expert technical support for the preparation of manufacturing the thick fiberboard and sandwich panel. We are grateful
also to Drs. Min Zhang, Kenji Umemura, Wong Ee Ding, and Guangping Han for their great help and advice in manufacturing the
thick panels. The authors are grateful to Hokushin Co. for the fiber and resin and to Ishinomaki Gouhan Co. for the plywood.
We thank Mr. Makoto Nakatani for his expert assistance when preparing the specimens for the shear test. Funding provided by
the Research Fellowship of the Japan Society for the Promotion of Science for Young Scientists as a JSPS Research Fellow is
also gratefully acknowledged. 相似文献
18.
Minoru Okabe Motoi Yasumura Kenji Kobayashi Kazuhiko Fujita 《Journal of Wood Science》2014,60(1):49-58
Cross-laminated timber (CLT) panels consist of several layers of lumber stacked crosswise and glued together on their faces. Prototype sugi CLT floor panels were manufactured and bending tests were carried out under the different parameters of lumber modulus of elasticity (MOE), number of layers, thickness of lumber and thickness of CLT panels. On the basis of above tests, bending stiffness and moment carrying capacity were predicted by Monte Carlo method. MOE of lumber was measured by using grading machine and tensile strength of lumber was assumed to be 60 % of bending strength based on the obtained bending test. Bending stiffness EI of CLT panels could be estimated by adopting composite theory and equivalent section area. Experimental moment carrying capacity showed 12 % higher value than the calculated moment carrying capacity by average lumber failure method, and also showed 45 % higher value than the calculated moment carrying capacity by minimum lumber failure method due to the reinforcement of the outer layer by the neighboring cross layer. 相似文献
19.