Advanced Materials Research Vols. 163-167

Abstract: Studying the vertical density profile (VDP) forming progress of fiberboard helps understand and improve the hot-pressing technology. The presented work aims to investigate the effects of coreline temperature and thickness curve on VDP by changing hot-pressing curve and moisture content of mat. In doing so, it was hoped to study the VDP forming progress and manufacture “Steep-Flat” VDP and “Flat” VDP fiberboard. The results indicated that Closure phase of traditional hot-pressing curve failed to alter shape of mat thickness curve which control the shape of VDP. The mat manufactured by traditional hot-pressing curve was “Steep” VDP and could not manufacture “Steep-Flat” VDP and “Flat” VDP; Closure phase of “high-low-high” hot-pressing curve could be separated into rapid compression stage, thickness expansion stage, and second compression stage. The density of surface layer formed at rapid compression stage and decided by first high-pressure. The density gradient between surface layer and core layer formed at thickness expansion stage and decided by expansion time. The density of surface layer formed at rapid compression stage and decided by second high-pressure. The “Steep-Flat” VDP and the “Flat” VDP could manufactured by modulated moisture content of mat, first high-pressure, expansion time, second high-pressure.

Abstract: A structural damage identification technique based on cross correlation function analysis of vibration measurements is proposed. An 8-storey steel shear building model has been chosen as the case verification. Structural acceleration responses from neighbouring test points are used to establish damage identification parameters. Experimental analysis shows that the method can achieve quite precise results.

Abstract: The interaction system which includes pi1e-supported tall buildings with multistoried basements and the adjacent medium of soil subject to the impact of earthquake is formulated in terms of the spline subdomain method,semi-analytical infinite element method and the bend-shear model of beam element,respectively.Taking advantage of the instantaneous optimal control algorithm, structure-basements-piles-soil interaction effect on the semi-active control is considered. It is shown that the results of structural control have obvious difference between the interaction system and the fixed-end system.The response of the former may be less about 10 percent than the latter in the paper.The dissipative capability of the structure self may be ignored largely if the interaction isn’t considered.When designing the system of the semi-active control, especially for some tall buildings,soil-structure interaction should be taken into consideration.

Abstract: Finite element analysis, based on various construction and service stages, of a genetic bridge was carried out to find the potential reasons causing longitudinal reflection cracking on top of bridge deck as well as the cures for solving this problem. Meanwhile, the effect of applied transverse posttensioning magnitude and tendon location as well as bearing pads’ supporting restraint was modeled in the FEA to investigate their effect on the distribution of transverse posttensioning force along the joints between adjacent box-girders. Results show that (1) transverse posttensioning and diaphragms reduce efficiently the tensile stress on top of deck; but this efficiency slows down significantly in bridge corner area, where exists still relatively higher tensile stress than other locations; (2) In some cases of loading combination, most locations on top of deck along the joints exist transverse tensile stresses, but the magnitude is less than 0.7Mpa, which could not cause the cracking if the decking concrete cover and keyway grout are properly selected and cast to the designated specifications; (3)Two patterns of transverse posttensioning output almost same result in the clamping stress along the joints for this proposed particular bridge model; (4)The vertical spacing between two tendon locations (upper and low level) should be farther spaced than the currently specified 1/3 girder depth so that less tensile stress or compressive stress is expected on top of deck; (5) The restrain from bearing pads modeled in this FEA has little effect on the stress distribution along joints between box girders.

Abstract: The indexes to determine the swelling potential of swelling rocks are still not unified. A series of testing results of swelling rocks of Zhangjiakou showed that: the dry saturated water absorption and the specific area of swelling rock are all correlated linearly with the content of smectite and the correlation coefficient can be reached to 87% and 96% respectively; however, content of the montmorillonite and free expansive ratio is in nonlinear correlation, which indicated that the free expansive ratio, the dry saturated water absorption and specific area can all reflect the characters of mineral components in swelling rocks. However, the liquid limit and the plasticity index were all in linear correlation with the montmorillonite content, but value of them were lower than practical ones, so they can not be suitable indexes to determine the expansibility of swelling rocks. The larger the free swelling ratio was, the larger the expensive ratio under no load was, but they have no good correlations which indicated that the properties of swelling rocks was complex, as a result it is defective tightness to determine the swelling potential only by mineral components. The swelling force and the expansive ratio under no load were also in linear correlation, which meant they can all characterize the swelling characters of swelling rocks. The lager the dry saturated water absorption was, the poorer the durability was, but the dry saturated water absorption can not reflect the disintegrative totally. Through comprehensive analysis, we took the dry saturated water absorption, coefficient of disintegrative and swelling force as the indexes to determine the swelling potential of swelling rocks.

Abstract: Cao river aqueduct is the mark building at main channel of the middle line of the South-to-North Water Diversion Project, of which the 30m span is the largest aqueduct in Asia for its span, and its structure is relatively complicated, which is the large-scale aqueduct that has been designed and constructed for the first time in China with great technical difficulties in structure form. For it will directly affect the safe operation of aqueduct that whether the actual stressing state, deformation conditions, prestress effect and etc. meet the design requirements, the impounding test of trial span was carried out before formal operation. As it can be seen from the test results analysis, aqueduct structure is under a good elastic working condition with about 1.00mm maximum deflection at mid-span and meets the design and specification requirements, which means the structure of aqueduct is reasonably designed, and structure operation is safe and reliable. In the meantime, the stress characteristics and deformation law of aqueduct structure has been mastered more overall and deeply according to the research on the impounding test, which provides important reference for later operation and management.

Abstract: Setting up of an objective function, update parameters and use of robust optimization algorithm are three crucial steps in FE model updating. In order to calculate the gradient of the objective function, analytic optimization algorithm is not easy to be achieved, while the direct optimization algorithm may achieve the objective function optimization simply by comparing the size of the objective function to move the iteration point. In this paper, the eigenvalues and mode shapes are used as the optimization objective function, the direct optimization algorithm is adopted, an updated finite element model is achieved, and a numerical example is given.

Abstract: With the accelerating process of urbanization, various kinds of unconventional concrete structure increases day by day. These kinds of unconventional specification concrete structure are characterized as large area, large span space, and great weight. Its scaffolding as the template support is different from the ordinary scaffolding outside. Their setup performs as large span space, high height, complex structure, high risk and sudden accident and so on. According to the Monitoring work achievement of the Memorial Hall for the Battle of crossing Yangtze River, this article systematically summarized this kind of high formwork bracket monitoring technology and the experiences from the aspects of monitoring project, system composition, instrument arrangement, instrument shaping, embedment technology and so forth.

Abstract: A new method of semi-active control on cable-MR system based on fuzzy logical theory in this article is presented. In the method, the voltage to drive MR damper is determined by fuzzy controller, which avoids the difficulty of calculating the voltage from the strong nonlinear MR model. In order to testify the effectiveness of the proposed method, the simulation analysis to a typical cable is made and its results are compared to the passive control (passive-on, passive-off) of MR and active control (LQR). The conclusion is that the operation of fuzzy control method is simple and practical. Its effect is better than the passive methods, but is a little worse than LQR.

Abstract: Long span hyperbolic-paraboloid composite torsional shell is a new type structure. In order to find out actual deformation of the roof during construction, monitoring is carried out based on deformation monitoring scheme that was put forward in this paper, and deformation parameters and characteristic of the roof are obtained. It is proved that the measured deformation values are basically consistent with the simulation calculations, and the results show that the scheme is correct and feasible, meanwhile, all of monitoring results are helpful for future analog calculation, design and construction optimization of similar project.