Abstract: The electromagnetic shielding effectiveness (SE) of cement based composites filled with carbon black and carbon fiber were discussed in this paper. Results show the SE of cement composites will get obvious improvement as the carbon black mass fraction increases beyond 6%. Carbon fiber is a much more effective additive than carbon back. The shielding effectiveness were gradually improved with the increase of content of carbon fiber, the maximum attained 21 dB at 1.5GHz. Adding carbon black and carbon fiber, SE of the cement based materials get more upward gradient, the maximum SE reached 27 dB in tested frequency range.
Abstract: This paper mainly studies the deflection under short-term loading of recycled course aggregate reinforced concrete beam is calculated by using of the formula of short-dated rigidity in code for design of concrete structures. According to testing the flexural performance of 6 recycled course aggregate beams with the same section size, different replacement ratio of recycled coarse aggregate of 0%, 50%, 70%, 100% respectively and different percentage reinforcement of 0.68%, 0.89%, 1.13% respectively, analyzes relation between deflection and replacement ratio of recycled coarse aggregate, deflection and percentage reinforcement, compare measured value and calculated value using of current codes and make statistical analysis this data . By regressing and analyzing the experimental data from literature, supplied short-dated rigidity modified formula of recycled course aggregate beam. The calculation results are in good agreement with the experimental data. The formula of short-dated rigidity can accurately calculate deflection under short-term loading of recycled course aggregate reinforced concrete beam, and can be referenced in engineering practice and correlative regulations.
Abstract: The effect of replacement of Portland cement by ground limestone as well as its specific surface Blaine (SSB) on the physical-mechanical properties of fresh and hardened cement paste is studied. The binder was composed of cement and limestone, which was prepared by eight replacement levels of limestone powder (0,5,10,15,20,25,30 and 35%) of binder by mass and four levels of SSB (300,600,800 and 1000 m2/kg). Test results demonstrated that the water requirement of normal consistency and the setting times(initial and final) decreased obviously as the replacement level of limestone powder increased and the extent of reduction was noticeable with the increase of SSB of limestone powder. The compressive strength of mortar incorporating different replacement levels and various SSB of limestone powder increased steadily with ages. The compressive strength decreased with the increase of replacement level of limestone, while as increased with the increase of SSB at the same replacement level and ages. The SSB influence factor was created to describe the effect of SSB of limestone powder on the compressive strength. The strength activity index of limestone powder concerning the replacement levels, SSB of limestone powder and mortar ages was established. The grade of limestone powder was suggested in order to reasonable utilization.
Abstract: Straw fibers were modified by acrylic acid coating treatment, and mechanical properties of straw fibers reinforced gypsum composite were investigated. Wax emulsion was added in order to improve waterproof properties of gypsum composite. Surface modification effect of straw fibers and micro-morphology of gypsum composite were analyzed by scanning electron microscope, infrared spectrometer and mercury porosimeter. The mechanism of modified straw fibers and wax emulsion in improving performances of gypsum composite was discussed.
Abstract: The surface of the PP fibers were modified by acrylic acid and grafted by suspension in water medium. The effect of modified PP fibers on mechanical properties of cement mortar was studied. The microstructure of fibers surface, the active functional groups of fibers and the profile of cracked samples were analyzed by SEM and IR. The results show that, crylic acid was grafted on surface of PP fibers after modification; the flexural strength of cement mortar reinforced by modified PP fibers improved markedly, compared with cement mortar reinforced by ordinary PP fibers.
Abstract: Based on observed temperature values in Beiluhe on Qinghai–Tibet Plateau, this paper sets up a regression equation using statistics methods between the temperature at shallow ground depth (0.5 m)and the direct solar radiation on embankment horizontal surface. There is a good linear relation between the temperature and the solar radiation after the phase difference is removed. Correlation coefficient R2 is 0. 9321, and the regression equation is: T = aQ – b where, T—temperature (°C) on horizontal surface of shallow ground (0.5m); Q—solar radiation after the phase difference is removed (W.m-2); a,b—constants, is 0.5552and 16.549, respectively. The equation is validated and allows the temperature on horizontal surface of railway embankments. Whether it applies to other places needs further study. And based on this conclusion, combining with the law of documents and materials, and considering local factors, such as vegetative cover, snow, lithology, soil moisture and so on, we further prove there is obvious linear relation between the temperature and the direct solar radiation on horizontal surface.
Abstract: Owing to some problems in the existent plywood products such as weak shear capacity and weak wear intensity, as while as the large consumption of crude wood resources, prestressed laminated strand lumber (PLSL) is proposed in this paper, in which the multiple integration method and prestressed technology are adopted to obtain a higher strength. More significantly, used wood can be reused as the raw material of PLSL, then the crude wood will be conserved and the cost will be lowered. To study its mechanical properties, the commercial software ANSYS is adopted to establish the finite element models of PLSL. The diameter and spacing of prestressed steel wire, the magnitude of the prestress and the width of the lumber are some factors considered. Based on the nonlinear finite element buckling analysis of these lumbers, some major conclusions are summarized as follows: (1) The improvement of strength is comparatively obvious to use PLSL compared with the traditional plywood products; (2) The ultimate bearing load is rising along with the increase of the diameter of the prestressed steel wire and the width of the lumber; (3) The ultimate bearing load is descending with the increase of the spacing of the prestressed steel wire; (4) The ultimate bearing load is rising along with the increase of the magnitude of the prestress at first, but when the prestress reaches a certain level, the ultimate bearing load starts to descend.
Abstract: The visco-elastic behaviors of coated fabrics are important for the design of membrane structure. In this paper, Ferrari 1002 is taken as the research object. The tests of creep and stress relaxation are carried out under five temperatures (23, 40, 50, 60, and 70 ) and three initial stresses (4, 15, and 26 kN/m), respectively. Results show that temperature and initial stress has great effects on the visco-elasticity of coated fabrics. With temperature and initial stress increasing, the visco-elastic behaviors are more obvious. The creep strain can be ignored compared with the corresponding elastic strain. After 24h, the remaining stress is less than 80% the initial stress. This paper can be references for the design of membrane structure.
Abstract: In the equivalent water depth truncated model test design of a deepwater semi-submersible platform, the viscous damper is designed to simulate the contribution of mooring damping to total damping of floating platform. The dissipated energy by a mooring line from the floating platform as a result of its oscillation is applied to calculate the mooring-induced damping. The mooring line and seabed interaction is based on the hypothesis of rigid seabed. The fluid drag force and inertia force on the mooring line are calculated according to the Morrison formula. The non-liner dynamic analysis of mooring line is executed in the time domain based on the finite element method. The mooring induced damping is obtained from the results. The value difference of mooring induced damping between the truncated and full-depth mooring line is linearized to provide parameter for the design of viscous damper.
Abstract: This article examines, from the energy viewpoint, a new lightweight, slim, high energy efficient, light-transmitting envelope system, providing for seamless, free-form designs for use in architectural projects. The research was based on envelope components already existing on the market, especially components implemented with granular silica gel insulation, as this is the most effective translucent thermal insulation there is today. The tests run on these materials revealed that there is not one that has all the features required of the new envelope model, although some do have properties that could be exploited to generate this envelope, namely, the vacuum chamber of vacuum insulated panels (VIP), the monolithic aerogel used as insulation in some prototypes, reinforced polyester barriers. By combining these three design components — the high-performance thermal insulation of the vacuum chamber combined with monolithic silica gel insulation, the free-form design potential provided by materials like reinforced polyester and epoxy resins—, we have been able to define and test a new, variable geometry, energy-saving envelope system.