Key Engineering Materials Vols. 326-328

Abstract: The mechanical properties of rock under high temperature, high geostress and high pore pressure are the basic and important information to assess the safety of underground engineering in west China. Based on the environmental conditions of the west route of south-to-north water transfer project in west China, a series of triaxial tests at confining pressures (0 to 60MPa) and temperatures (25°C to 70°C) as well as pore pressure (0 to 10MPa) have been conducted for a sandstone. It is reported that under the temperatures varying from 25°C to 70°C, the strength of the rock increases with the increment of confining pressure, while the deformation modulus of the rock doesn’t change distinctly with the increment of confining pressures. It is also indicated under the temperatures condition in the experiments, when the confining pressure is lower than 40MPa, the strength of the rock increases with the increment of temperature, whereas when the confining pressure is higher than 40MPa, the strength of rock tend to decrease with increment of temperature. It is further shown that the strength decreases with increasing pore pressure, and the decreasing rates tend to decrease with the increment of confining pressures.

Abstract: It is very important to choose a similar material which simulates rock mass correctly in geo-mechanics model test. In this paper, we introduce similar material research status and analyze the principle of selecting and compounding. According to the experiences of similar material research, we develop a new similar material (we call it iron barites sand cementation material, abbreviate IBSCM) through hundreds of compounding experiment. This similar material is made up of iron ore powder, barites powder, sand, rosin, alcohol and gypsum powder. Iron ore powder, barites powder and sand are main materials, the solution of rosin and alcohol is glue, and gypsum powder is regulator. Specimen mechanics tests show that different rock mass can be simulated by the model materials with different materials compounding. The new similar material is easy to buy and its price is cheap, and it has some advantages, such as high density, stable performance, easy dryness, and easy cutting. The new similar material can simulate a lot of rock mass, so it is an ideal similar material. At last, we apply this new type similar material to tunnel geo-mechanical model test and gain the ideal result.

Abstract: This paper presents the results of an investigation on the force transfer mechanism in an embedded column base of a composite structure. In the experimental program, eighteen push-out specimens were tested. The factors influencing the mechanism of force transfer were the amount of confining reinforcement, compressive strength of concrete, and diameter of stud connectors. The results of experiment indicated that force transfer could be characterized into two stages, and the factors governing each stage were identified. The first stage was governed by the bond strength between the steel column base and the concrete. The second stage begun after chemical debonding and was governed by the shear strength of stud connectors as well as the frictional strength between the steel and the concrete. Based on the experimental results, the equations to estimate the bond strength, the friction strength, and the shear strength of stud connectors were proposed. The load carrying capacity of an embedded steel column base could be predicted by taking the sum of the shear strength of stud connectors and the friction strength. The predicted load carrying capacity was found to agree well with the experimental results over various range of concrete stress.

Abstract: In the construction of composite bridge structures, various types of shear connectors are usually used to provide an efficient load transfer and the composite action of two or more different materials. In the previous work conducted by authors, a new type of the shear connector was introduced, which is the perforated shear connector with flange heads (T-shaped perforated shear connector), and the structural behavior of the shear connector was discussed based on the results of push-out tests. For the practical design of new shear connector, it is necessary to develop the equation for the prediction of the load carrying capacity of the shear connector. In this study, the existing design equations for the Perfobond shear connector were briefly analyzed and the equation for the prediction of the shear capacity of T-shaped perforated shear connector was suggested empirically. By comparing the results obtained by the suggested equation, the existing equations for the Perfobond shear connector, and the experiment, the applicability and effectiveness of the suggested equation was estimated.

Abstract: Measurement of fiber orientation distribution state is very important constituent to find out decision of processing condition of product or mechanical special quality of moldings in fiber reinforced polymer composite material. Therefore, reliable measurement method of fiber orientation angle distribution is established, and need researcher about simplicity measuring method urgently the nondestructiveness. In this research, to investigate about accuracy of fiber orientation angle distribution measurement of fiber reinforced composite material by intensity method, find fiber orientation function value that is measure of fiber orientation distribution state constructing fiber orientation simulation picture by plotter changing diameter and length and orientation state of fiber. Recognize this fiber orientation simulation picture by image scanner, and measure fiber orientation angle distribution state by this realized intensity information. This time, I wish to measure reliable fiber orientation angle distribution comparing fiber orientation function calculation value saving in the advance with fiber orientation function value that is measured by intensity method. The results show that measurement accuracy of the fiber orientation angle distribution by intensity method is affected by the fiber aspect ratio when the total length of oriented fiber is same. The average gradient of fiber orientation function is 0.94 for 1000mm of the total fiber length and is 0.93 for 2000mm when the fiber aspect ratio is over 50. Measurement accuracy by intensity method is about 94% and the reliable data can be obtained by intensity method.

Abstract: The study for cyclic load-displacement relationship and seismic characteristics of square Concrete-Filled Steel Tubular (CFT) columns is experimentally and analytically conducted. Nine CFT column specimens are tested under constant axial loading and monotonically increasing lateral loading. For predicting the strength and ductility of CFT columns, fiber analysis technique is used. The analytical results show reasonable agreement with experiment results and the moment capacity of CFT columns is predicted with reasonable accuracy using the fiber model. The influence of the steel tube on the lateral response of CFT columns is studied for the evaluation of seismic performance.

Abstract: Bending collapse behaviors and energy absorption characteristics of aluminum-GFRP hybrid tube beams were evaluated by using experimental tests combined with theoretical analysis. Hybrid tube beams composed of glass fiber-epoxy layer wrapped around on aluminum tube were made in autoclave with the recommend curing cycle. The hybrid tube beams showed a considerable improvement in their bending performance. The maximum bending moment and specific energy absorption of the hybrid tubes were higher than those of the aluminum tubes. They were also evaluated as a function of ply orientation and thickness of GFRP layer. A modified theoretical model was developed to predict the resistance to the collapse of hybrid tube beams subjected to a bending load. Theoretical ultimate bending moments and moment-rotation angle curves of hybrid tube beams were in good agreement with experimental ones. Hybrid tube beams strengthened by GFPR layer with 90°/0° and 45°/-45° ply orientation showed an excellent bending strength and energy absorption capability, respectively. Therefore, on the basis of above results, it was concluded that aluminum-GFRP hybrid tube beams might be employed as reinforcing and/or energy absorbable light weight space frame.

Abstract: Polycarbonate/multiwalled carbon nanotubes (PC/MWNT) nanocomposites with different contents of MWNT were successfully prepared by melt compounding. The mechanical properties of the PC/MWNT nanocomposites were effectively increased due to the incorporation of MWNTs. The composites were characterized using scanning electron microscopy in order to obtain the information on the dispersion of MWNT in the polymeric matrix. In case of 0.3 wt% of MWNT in the matrix, strength and modulus of the composite increased by 30% and 20%, respectively. In addition, the dispersion of MWNTs in the PC matrix resulted in substantial decrease in the electrical resistivity of the composites as the MWNTs loading was increased from 1.0 wt% to 1.5 wt%.

Abstract: The development characteristics of impact-induced damage in carbon-fiber-reinforcedplastics (CFRP) laminates were experimentally studied using a drop-weight impact tester. Five types of CFRP laminates were used to investigate the effect of stacking sequences and thicknesses. The efficiency of absorbed energy to impact energy was different for CFRP laminates with different stacking sequences or thicknesses. The DA/AE ratio of delamination area (DA) to absorbed energy (AE) was almost the same for CFRP laminates with the same stacking sequence regardless of the thickness. We found that the DA/AE ratio could be used as a parameter to characterize the impact damage resistance in CFRP laminates with different stacking sequences.

Abstract: The strain distribution around the unstiffened and stiffened circular cutout of the isotropic stainless steel (ANSI type 304) and the GFRP laminated composite cylindrical shells subjected to axial compression are studied. The experimental results are obtained and compared with numerical analysis. In experiment, the strain is measured around the circular cutout by strain measuring system under the axial uniform compression loading. The numerical analysis is performed by the commercial finite element code ANSYS. The strain concentration factor (SCF) is defined to investigate the strain concentration around the circular cutout. The SCF of the stainless steel cylindrical shell with a stiffened cutout is decreased 39% in experiment and 50 % in numerical analysis. The SCF of GFRP laminated composite cylindrical shell is decreased 22% in experiment and 31 % in numerical analysis.