Advanced Materials Research Vols. 168-170

Abstract: Based on the study of the unclear mechanical behavior and failure mechanism of masonry components in high axial compression after Wenchuan Earthquake, the thesis analysis the failure mechanism of masonry in compression in microscopic hierarchy process level with the damage mechanics and probability and statistics method. Aimed at making up the shortage of that it is difficult for the previous constitution relationship model to identify the difference between the stress decrease of the material when loading during strain softening stage and the stress decrease of the material when unloading during the elastic stage, the thesis studies the constitution relationship model for masonry in strain space and describes the strain hardening and softening phenomena during the force process of the components with a uniform loading and unloading standard, and avoids the uncertain description on the strain softening stage. Approved by the experiments, the model can show the characters of the compressive masonry experiment, and give a reasonable explanation for the deformation principle of masonry in compression at the micro-level, also fit the experiment results well.

Abstract: Recently, detection of structural damage based on the system identification has received great attention. In this paper, a technique is proposed for the identification of nonlinear structural parameters under unmeasured excitation. The identification algorithm is based on the extended Kalman filter for the extended state vectors including nonlinear parameters and the recursive least squares estimation for the unknown inputs. Two different models are used to simulate nonlinear structures: One is a 4-storey Duffing-type nonlinear elastic shear-frame structure, the other is a 4-storey Bouc-Wen hysteretic shear-frame structure.Two numerical examples are carried out on the two kinds of models. The simulation results demonstrate that the proposed approach is capable of identifying the nonlinear structural parameters and unknown inputs with good accuracy.

Abstract: Many experimental researches have been conducted on explosive spalling performance of concrete of high-strength / high performance concrete (HSC/HPC). This paper summarizes two main explosive spalling mechanisms (Vapor pressure build-up mechanism and Thermal stress mechanism) of concrete at elevated temperature, and also presents the measures to resistant the explosive spalling, i.e. by incorporating fibers (polypropylene fiber(PPF), steel fiber(SF) and hybrid fiber of the first two). Finally, the further studies of both the mechanism and the measures are proposed. Also, the preliminary study of ultra high-strength concrete (UHSC) on fire-resistance are mentioned.

Abstract: The performance of materials made from Portland cement is usually evaluated by tensile strength under compression loads, elastic modulus and porosity. Modulus of elasticity is usually determined from compression tests, and the results show large dispersions. With the advances in data acquisition and signal processing, the infrared thermography and forced resonant frequency have been increasingly used in the study of materials. However, these studies are devoted almost entirely to metals. In this paper it is evaluates the use of the method of forced longitudinal resonance frequency and infrared thermography as a tool for characterization of the buildings cementitious materials. The results show that thermography and forced resonant frequency are Able to detect changes in concrete macrostructure as well as the nature of its constituents.

Abstract: Mix proportion design methods of different asphalt mixtures used in China and other countries were taken comparative analysis. Volume indexes were proposed for gradation design of mineral aggregate and road performance parameters for function analysis in structure layers were used to determine optimum asphalt content in accordance with the service requirements and current construction situation of heavy load asphalt pavement in China, and other performance indexes were taken as verification parameters for mix proportion design of asphalt mixture. Consequently, asphalt mixture with optimized design methods can reflect the actual service condition of heavy load asphalt pavement and correspond with the design and construction of heavy load asphalt pavement in China.

Abstract: Steel bars used in high-rising building were developed by the addition of V and Nb in medium carbon steels. In this study, two steel bars with different diameters (16 mm and 36 mm) were analyzed via optical and transmission electron microscopy (OM and TEM)., the microstructures of the steels studuied consist of ferrite and pearlite the same as those of the conventional steel bars, but they possess higher yield strengths (over 685 MPa) in combination of considerable elongations (above 10%). The results of transmission electron microscopy reveals that the copious nano-sized (about 20 nm) carbides were interphase-precipitated in ferrite and that the inter-lamellar spacings of pearlite were extra fine, about with a scale of 100 nm. It has been estimated that the small carbides and fine pearlite provide yield strengths, approximately 300 MPa and 800 MPa, respectively. In addition, the volume fraction of ferrite was up to 40%, which offered sufficient soft phase to experience external stress. The results of tensile tests for the steels studied demonstrat that the amount of strain can be up to 1.4% as a yield stress is reached, and the apparent yield point and plateau are present in the stress-strain curves.

Abstract: The chemical compositions of Artocarpus heterophyllus Lam wood were investigated and content of trace elements in wood were determined. The result showed that the chemical compositions of Artocarpus heterophyllus Lam wood are as following: ashes 15.5 g•kg^-1, cold water extraction 35.2 g•kg^-1, hot water extraction 55.1 g•kg^-1, 1%NaOH extraction 157.7 g•kg^-1, benzene-alcohol extraction 79.2 g•kg^-1, sodium nitrate-alcohol cellulose 467.6 g•kg^-1, holo-cellulose 709.8 g•kg^-1, pentosan 212.6 g•kg^-1,Acid-soluble lignin 44.9 g•kg^-1, Acid insoluble lignin 237.4 g•kg^-1, Organic solvent soluble lignin 248.3g•kg^-1, Phenolic hydroxyl content of organic solvent soluble lignin 0.25 mmol•g^-1; the content of 12 trace elements in Artocarpus heterophyllus Lam wood are: Fe 959μg.g^-1, Mn 9.37μg.g^-1, Cu 5.60μg.g^-1, Zn 17.1μg.g^-1, Ca 2.26 mg.g ^-1, Mg 433μg.g^-1, Na 28.1μg.g^-1, K 1.05 mg.g^-1, Al 46.2 μg.g^-1, Pb 0.603 μg.g^-1, Cd and Ni were not detected.

Abstract: Failures in concrete elements and structures often result from simultaneous effect of heat and moisture in concrete or form environment. Numerical simulation is an efficient way for investigating concrete deformation and the thermal and moisture parameters are the essential inputting data in simulation. Obviously, the numerical deformation of concrete will change with the varying thermal or moisture parameters which result from the materials and mix ratio used in preparing the concrete. The influences of hygro-thermal physical parameters on the deformation of concrete were investigated numerically using a specially developed software, which is named Coupling Temperature and Moisture Simulation System for concrete (CTMSoft) in this paper. The results of numerical experiment imply that evaluating the influence regularity of only a single parameter on the concrete deformation is unscientific and the coupling effect should be considered in the fact that there is not a definite relationship between concrete deformation and a single parameter.

Abstract: To revitalize a historical building, the Taipei Camphor Factory, a major renovation is being coordinated by National Taiwan Museum. As part of the project, a seismic assessment was conducted to ensure the structural safety of the building. A three-dimensional finite-element analysis was carried out based on material data collected from the field, and it was found out that both the as-is building and the current retrofit plan would not provide adequate seismic capacity. To resolve this problem, an shear walls scheme was configured and seemed to yield a much better performance.

Abstract: Adobe (khesht) is the most common traditional material which is used in Persian structures because of compatibility with environment, being economic, ease and rapidity of use. In different eras of Persian history using adobe had been common. Its archaism refers to sixth millennium B.C. Attendance to these kinds of structures is important for two reasons. First, most residential structures and old regions of cities are made by adobe. Second reason is the cultural and antiquarian aspect of monuments. This article introduces features of adobe as a traditional material. Besides, process of building adobe structure and its reaction to earthquake.