Applied Mechanics and Materials Vols. 166-169

Abstract: Ten full-scale fully grouted reinforced concrete masonry shear walls were tested under force-displacement controlled reversed cyclic lateral loads simulating seismic effects. Relevant experimental phenomena and data indicated four walls failing in shear failure and the other six walls failing in flexure to evaluate seismic performance under compress, flexure and shear combined action. The paper mainly examinates lateral bearing-load capacity through two parameters: initial crack and ultimate strength under different failure modes. Through experimental analysis it can be concluded that the shear strength at the initial crack and ultimate load improved with the increased applied axial stress, and the increment of the shear strength was different in shear failure and flexural failure modes. Meanwhile, the ratio of the initial crack load to ultimate load on shear mechanism was from 0.57 to0.59,which was more stable than that(from 0.52 to 0.66)on flexural mechanism. In other words, the applied axial stress have more significant influence on flexural failure walls than shear ones.

Abstract: By means of axial compressive and eccentric compressive tests of four Four-tube Concrete-filled Steel Tubular Laced Columns, to research the strain modes of these columns without yield point. Longitudinal strain and the hoop strain of column limbs, the Poisson ratio of combination of materials have been obtained.

Abstract: Considerable amount of studies on the ductility and flexural behaviour of normal and high strength concrete elements under static load can be found in literature. However, most of the previous theoretical investigations on moment-curvature (M-φ) relationship of concrete elements to calculate curvature ductility and flexural capacity did not take account of the strain-rate effect on the material models. M-φ analysis of concrete elements under dynamic loading are often conducted with material models developed for quasi-static load by applying Dynamic Increase Factors (DIF) to the material properties to reflect the strain-rate effect. Depending on magnitude and duration of applied dynamic load, element stiffness and boundary condition strain-rate varies over the cross section. Thus, the application of DIF to modify peak material properties often fails to reflect the strain-rate effect reliably. The improvement of using material model which incorporated strain-rate in its constitutive equations has been explored in this study. The effects of reinforcement amount, grade and concrete strength on curvature ductility for different strain rates have been studied using material models which have strain-rate effects included in theirs formulation. Based on the parametric study, a simple formula to estimate curvature ductility for concrete elements under explosive loads (high strain-rates) has been proposed.

Abstract: In this paper, graphene grown by Chemical vapor deposition (CVD) on a Cu foil in a cold-wall furnace was used to fabrication the graphene strain gauge. The graphene membrane was patterned to wire grid shape on the Cu substrate by photolithography method in the clean room. The pattern was transferred to PDMS substrate and seal by it also to make graphene in a stable surroundings. Through the standard calibration, it was calculated that the linearity and multiplicity of the graphene strain gauge both were 0.0076%F.S.. Which indicated the good quality of the gauge. The gauge factor was 2.4, as the highest value as that of the alloy strain gauge. We also find the graphene strain gauge output increase proportionally with increasing curvature of its deformation.

Abstract: Experimental studies showed that vertical cracks appeared along the cold-formed steel or the steel sheet on the adaptive-slit shear walls when the wall was subjected to horizontal earthquake loading, and the adaptive-slit shear wall experienced the loading process from the whole wall section to the slitted wall section. So the appearance and development of the vertical cracks can reflect the seismic behavior of adaptive-slit shear walls. According to the mechanical characteristics of the adaptive-slit shear walls, this paper proposed a method to calculate the cracking load. It is found that the calculated results has a good agreement with the experimental results.

Abstract: This paper analyzed the failure mode for crack in uniaxial compression according to the stress intensity factor, and obtain that the failure mode for crack in uniaxial compression is compression-shear. The wing crack was deformed, after the crack tip initiate. By analyzing the dimensionless stress intensity factor, we obtain that the failure mode for wing crack in uniaxial compression is tension-shear, and we obtain that the dimensionless stress intensity factor for wing crack decreased with inclined angle increased. The inclined crack propagation in uniaxial compression was numerically studied using rock failure process analysis code (rfpa), and obtain that one inclined crack in uniaxial compression formed mode I offset crack parallel to load direction in the end. The numerical results of failure mode are accordance with stress intensity factor.

Abstract: Concrete-filled steel tubular(CFT) columns are often used as the main supporting columns for high-rise buildings and has become a topic of academic concern. The past research about CFT most focused on its ultimate strength and mechanical behavior. The experiment method which is usually expensive and time-consuming. Other research methods include combining experimental data with appropriate theory to design or calculate the structural properties, and these methods tend to have a conservative assessment of the results. Therefore, some researches have been developing finite element model to simulate and analyze the ultimate strength and buckling condition of CFT and its component behavior. In this paper, finite element analysis is used to explore the mechanical behavior of CFT during exerting axial compression load. Contact pair settings and friction coefficient settings were compared with different pattern to investigate the accuracy of simulation and the mechanical behavior of CFT columns. Study found that the ultimate strength for CFT columns obtained by finite element analysis can achieve good accuracy, and in the mean time the mechanical behavior simulation of CFT columns with proper finite element settings could be achieved.

Abstract: Fast-growing poplar wood, Populus ussuriensis Kom, was used to prepare novel wood-polymer composite by the in-situ polymerization of methyl methacrylate (MMA) and styrene (St). SEM observation and FTIR analysis indicated that the resulted polymer well filled up wood cell lumen and physically reinforce wood matrix. The test results also proved that the mechanical properties of wood including modulus of rupture, modulus of elasticity, compression strength and hardness of were improved by 68.28%, 110.27%, 62.43%, 357% over those of Untreated Wood, respectively. Such wood-based composite could be potentially used as reinforced material in construction fields.

Abstract: The hollow flange beam (HFB) is a unique cold-formed steel section developed in Australia for use as a flexural member. This paper presents two kinds of new cold-formed flange-closed welding sections named HF1 and HF2 according to different section component and parameters of HFB. Nonlinear finite element method has been adopted to investigate the mechanical properties such as buckling mode, deformation process, rigidity, ductility and correlation curve of two kinds of new section members which being subjected to axial compression, flexure, combined compression and bending. Some conclusions can be drawn from above work that the new sections have some superiority properties, such as higher load carrying capacity and section modulus, sufficient section stiffener and the sub element local buckling hard to happen and so on. Being subjected to flexure and also being subjected to compression, combined compression and bending are suitable for the mechanical properties. The new cold-formed flange-closed welding section members can be applied to the experiment investigation deeply so as to be used in the practical engineering.

Abstract: This paper records the laboratory experiments on mechanical properties of bamboo plywood.According to related test codes, The mechanical properties such as bending modulus, bending capacities and shear modulus were calculated by specific formulas.All results were based on a series of tests conducted by the electronic universal testing machine and dial indicator . Bamboo plywood (including directed and nondirected) has satisfactory flexural and shear properties during the tests.Before tests,two surfaces of test block were defined as free surface and cutting surface corresponding to two loading directions.In different loading directions ,test block with the same size may behave different midspan deflections under the same cyclic load. Based on measured datas , the related mechanical modulus were gained , and the failure modes of bamboo plywood were discussed .