Advanced Materials Research Vols. 446-449

Abstract: Talc powder is widely used in building engineering, especially preparation for coating, waterproof material and ceramics. With increasing demands for building material quality, the requirement for the particle fineness and particle-size distribution of talc power becomes higher than ever. A new method of process parameters analysis on turbo air classifier for talc powder is put forward in this paper. The effect of the two process parameters on a classification performance index is reflected visually through the 3-D drawing based on Matlab, so the one-dimensional process parameter analysis method is expanded to the two-dimensional process parameters analysis method. In the present study, a turbo air classifier is used as the classification system and fine talc powder is used as materials. The sample data is gathered through setting different process parameters. The experiment results show that process parameters analysis can be implemented quickly and visually. In actual production applications of turbo air classifier system, the user can select the suitable process parameters flexibly considering the production requirements according to the 3-D meshes based on Matlab. This method is also applicable for classification of other powder.

Abstract: The energy saving of office building plays an important role in large-scale public building energy saving. This paper analyzed the energy waste phenomena and problems, found the office building energy efficiency weaknesses and correction, on basis of researching and testing a large public building energy consumption system in Tianjin.

Abstract: In this paper，the ultimate bearing capacity of unstifened overlapped CHS K-joints is investigated by using the finite element method with influence of weld and non-weld on joint ultimate capacity under brace different bearing capacity. with angle of chord and brace is increasing ultimate capacity to lowed more and more small，which hidden weld is non-weld by one brace is pulled and other is pressured. ultimate capacity no influence to hidden welded and non-welded by both brace is pulled.

Abstract: The AB2 type hyperbranched poly(amine ester) (HBPAE) can be used as adsorbent to adsorb nitrite from aqueous solution due to a large number of terminal hydroxyl groups, where the hydrogen-bonds could formed between OH and NO2-. However, the hydrophilic properties of HBPAE limited their utility in the application because of the difficulties in removing adsorbent from nitrite solution after the adsorption was finished. The hydrophilic properties of the HBPAE were changed by means of end capping method, where the trichloroctadecylsilan (OTS) was adopted as the hydrophobic alkyl chains. The modified HBPAE by OTS can be separated from the aqueous solution. The adsorption kinetics of nitrite from aqueous solutions onto modified HBPAE was investigated to show the pseudo-first-order kinetic mechanism. The equilibrium adsorption data were found to be well fitted by Freundlich isotherm equation.

Abstract: Lying-tensile concrete creep device was designed, and the device was used at the early age of concrete in measuring the tensile elastic modulus, creep and tensile strength. Meanwhile, the using of the device to determine the parameters has been authenticated. Tests show that the usage of the device not only can determine the early age of concrete creep, elastic modulus, but also can maintain constant loads without stabilized device.Study shows that under the same conditions, the ultimate tensile strength of the concrete which were measured creep should be lower than than that of non-creep of concrete . The earlier the loaded age, the greater decreased of ultimate tensile strength, it indicats that the creep of concrete has a certain weakening effect on concrete bearing strength.

Abstract: Penetration of concrete targets was simulated based on self-compiled program generating two-dimensional random aggregate model. Random convex polygons were used to simulate the aggregate particles of concrete, HJC model to describe constitutive relations of the aggregates and mortar while concrete targets are subjected to large strains, high pressure and high strain rate. With this model, the Forrestal's penetration test was simulated by ls-dyna software. By comparing the calculated results with the test data, It is shown that random aggregate model can be applied to simulate the dynamic destruction problems of concrete-like materials.

Abstract: Most of the previous researches on the concrete-filled steel tube are restricted to deterministic approach. To give a clearer insight about random properties of circular concrete-filled steel tube, reliability analysis is carried in the present study. Material and geometrical nonlinear analysis of a circular concrete-filled steel tube is performed with a three-dimensional degenerated beam element, which can efficiently obtain the structural nonlinear responses. Through the combination of first order reliability method and nonlinear finite element analysis, the reliability about ultimate resistance capacity of the concrete-filled steel tube is investigated. The influences of parameters such as material strength, slenderness, initial geometrical imperfection, and etc. on reliability of circular concrete-filled steel tube column are studied. Some conclusions obtained from reliability analysis may be beneficial for rational analysis and design of the concrete-filled steel tube in practical engineer structures.

Abstract: Damping evaluation is of great importance in predicting the dynamic response of systems. To get the accurate damping ratios of a system, many identification methods have been proposed and developed. But only few of them achieved accurate results for in-situ buildings due to the fact that the responses are significantly influenced by noise. This paper proposes a new method to accurately identify the damping ratios of in-situ buildings. The method is based on ambient excitation technique which requires no artificial excitation applied to SSI system and to measure output-only. The damping ratio identification is then performed by combining the improved random decrement method and Ibrahim time domain method. To demonstrate the validity of the proposed approach, a case study is performed and the results are compared with the conventional peak-peaking method results. The results show the proposed method can effectively identify the modal parameter of either frequencies or damping ratios of in-situ buildings subjected to ambient excitation.

Abstract: Wenchuan Earthquake has caused substantial damage to reinforced concrete columns, in order to improve their lateral stiffness, wing walls are added to repair and strengthen the columns. Based on engineering practice, the mechanical calculations of normal section bearing capacity on damaged reinforced concrete columns strengthened by wing walls have been conducted, and based on the N-M curves of various special-shaped columns, the influence laws of different azimuths and different axial compression ratios on bearing capacity of normal section have been analyzed, therefore mechanical properties of special-shaped sections have been obtained, which provides reference information for engineering technology.

Abstract: This paper describes the strain mode damage detection theory and a three-dimensional reinforced concrete beams finite element model was built by finite element software. The different degree injury models tests were compared. Experiment’s results show that the first four natural frequencies of different degree injury models are small differences while the corresponding strain modes have a significant changed in damage location. The structure of the strain mode changes are still evident when structural damage occurred in the strain mode node.