Applied Mechanics and Materials Vols. 71-78

Abstract: A new matrix on the covariance of covariance is formed from the auto/cross-correlation function of acceleration responses of a structure under white noise ambient excitation. The components of the covariance matrix are proved to be function of the modal parameters (modal frequency, mode shape and modal damping) of the structure. The number of vibration modes associated with components of the matrix is only limited by the sampling frequency. Compared to the general methods for extracting modal parameters, the formulated covariance matrix contains more information on the vibration modes of the structure. An in-service suspension bridge is analyzed. Only the output acceleration responses are used to compute the covariance of covariance (CoC) matrix and the Pattern Assurance Criterion (PAC) values. From the CoCs variation and the changing trend of the PAC curve, the healthy condition of the bridge is assessed. The method is independent of analytical model and huge amount of data can be analyzed. It is especially suitable for long-term on-line health monitoring of a structure.

Abstract: The present paper probes the planning concept of buildings for special education, explores humanized design ideas of special education under specific settings; proposes the layout should be centralized, the function should be multiplied, the landscape should be diversified. The feasibility and implementation effect is also analyzed in line with the design practice.

Abstract: Seismic frequency-magnitude relationship has been investigated in China, based on the earthquake data in the range of M3.0 to M7.0 during the years 1986-2008, to study the potential of variations of b-values with the depth. According to the results, there is a systematic decrease in b value with increasing depth of earthquakes. At the shallow depth conditions, with more heterogeneous material properties and lower lithosphere stress prevail, rupture initiation is more likely to stop before accumulating into large earthquakes, producing relatively smaller earthquakes and consequently higher b-values. On the contrary, the larger earthquakes are more likely to happen at a greater depth.

Abstract: In this paper, the applicability of the source localisation method in Acoustic Emission (AE) technique to determine the crack locations in masonry is investigated. A series of pencil-break tests are performed on a two-span masonry arch bridge. Because of the layered structures, the assumption of homogeneous material and uniform velocity field in the classical method for concrete is not suitable in the masonry structures. The velocity is not uniform but shows a downdraught with the increasing distance due to the layered material structure. Based on this property, a modified AE source localization method is proposed. The modified factor in the model greatly reduces the effect of the inhomogeneity. The testing results from the pencil breaks and the central pier settlement tests highlight the effective of the modified method.

Abstract: The tunnel excavation is often existed in civil engineering, in which the minimum roof thickness of tunnel is an important index in tunnel construction and design. Some work have been done on this field, by analytical analysis method and numerical simulation method based on linear criterion. In order to add some conclusions to the roof thickness prediction by nonlinear criterions, in the present paper, the calculation model for excavation of tunnel is built by numerical method, the nonlinear criterion is applied to describe the failure situation of the surrounding rock mass; then, according to the reduction method for thickness of roof, the thickness of the roof after excavation in tunnel is analyzed with the nonlinear criterion, to give some guidance for the real practice.

Abstract: This paper analyzes the factors which impact the orientation of urban such as geographical location, natural resources, international political situation, and identify the status of the city in the national strategic pattern. Finally, manage and analyze these factors on GIS platform, present a rise dynamic orientation mode of Altay city.

Abstract: Phase-change thermal storage insulation mortar was prepared by using low melting point paraffin as phase change material (PCM), added with appropriate cementing materials, additives and water in this paper. The construction performance, mechanics and thermal properties of the insulation mortar were tested. The results showed that the compatibility between the microencapsulated paraffin (MCP) and inorganic cementing materials was improved by using the silane coupling agent and binder to modify the surface of the MCP, that the cracking of the mortar was solved by introducing the fibers to improve the toughness in the low melting MCP insulation mortar, that the primary physical properties of phase change mortar accord with the standard of the similar mortar, and that it has a favorable phase-change thermal storage ability and an increasingly wide utilization.

Abstract: Surface coal mining and underground coal mining over a hundred years had caused a series of geological hazards in Fushun city. Basing on classification and characterize of geological hazards, with regarding to tectonic history, a control theory of geological structure is proposed to study and prevent the geological hazards in mining cities. According to the location of intersection of main faults F_1A and F₁, the geological structure of Fushun mining area is divided into three types, some advises of prevention to geological hazards are suggested for each type in the coalfield.

Abstract: Since reform and opening-up, the process of urbanization of the country has been obviously accelerated in China. But the past urbanization policy has seriously hindered the original styles of cities, especially the traditional residential Houses in these cities. According to the field research on the the traditional residential Houses of Kaifeng City, this paper discusses the protection strategy for LeGuan Street, and gives some advices of development on turisms, educations, so as to realize the sustainable development of the street.

Abstract: The water mist is an economical and environmental agent for gas explosion suppression. It can be applied in the commonly gas concentration zones and the gas accumulation zones which is difficult to reduce the concentration of methane gas. By numerical analysis, this paper studies the effect of the direction and the number of the nozzles, and the distance form the nozzles to the wall at X direction in upper corner in coal mine. For gas explosion suppression in upper corner, it can use one nozzle which direction is same as the wind and the distance is 2m.