Applied Mechanics and Materials Vols. 204-208

Abstract: The fuzzy control technology is a kind of intelligent control method, and it has strong robustness. The fuzzy control strategy is used to choose the control currents of MR dampers in this paper. In order to illustrate how to design the fuzzy controller, three kinds of the fuzzy controller having different membership functions and fuzzy rules are designed. A five-floor MR structure using the designed different fuzzy controllers is simulated. Analysis results show that for the MR structure, it is not best that MR dampers provide the maximum forces to the structure, so the displacement and acceleration responses of the structure must be weighed at the same time to make MR dampers provide reasonable forces when the membership functions and fuzzy rules are designed.

Abstract: This paper carries out a series of experimental study on 6 column specimens, analyses and compares with the different parameters on the axial loading tests of RC columns and RC columns strengthened with steel tube. The experimental results show that the RC columns strengthened with steel tube take full advantage of loading properties of both materials, thus greatly improve the bearing capacity of specimens. With the same wall thickness steel tube, the improving degree of bearing capacity of long columns is bigger than the short columns, and the reinforcement effect is more obvious. The experimental results can offer reference for scientific research and engineering staff, and promote this reinforcement method to be widely used in engineering practice.

Abstract: The method of damage alarming based on wavelet packet analysis which applied on steel-frame structure is researched. Firstly, the method of damage identification based on wavelet packet analysis is introduced. Secondly, in view of the dependability of the method on the excitation, virtual impulse response function is brought in to enhance robustness of the method to the excitation. Lastly, through the steel-frame structure experimentation of damage alarming, the two damage modes of the structure are identified by the method based on wavelet packet energy spectrum. The experimentation results show that the effect of damage alarming to the steel-frame structure is completely obvious by wavelet packet analysis. Accordingly, this method has much application value for engineering.

Abstract: The stiffness of reinforced concrete simple beams strengthened with carbon fiber sheets is studied in this paper. The calculation formulas of it are discussed, for steel yielding and not yielding. The stiffness increases with the number of carbon fiber layer or reinforcement ratio increases.

Abstract: Two economic models, i.e. auto-regressive and moving average model (ARMA) and generalized auto-regressive conditional heteroscedasticity model (GARCH), are adopted to assess the conditions of structures and to detect structural nonlinear damage based on time series analysis in this study. To improve the reliability of the method for nonlinear damage detection, a new damage sensitive feature (DSF) for the ARMA-GARCH model is defined as a ratio of the standard deviation of the variance time series of ARMA-GARCH model residual errors in test condition to ones in reference condition. Compared to the traditional DSF defined as the ratio between the deviations of ARMA-GARCH model residual error in two conditions, the successful outcomes of the new DSF can give obvious explanation for the current states of structures and can detect the nonlinear damage exactly, which enhance the worth of structural health monitoring as well as condition-based maintenance in practical applications. This method is finally verified by a series of experimental data of three-story building structure made in Los Alamos National Laboratory USA.

Abstract: The coal ash wall board filled with core powder is a new kind of light and hollow board that can be produced in factories. It uses cement with high strength, coal ash and auxiliary chemicals as its raw material, after pouring concrete and reinforcing bars into its cavity, it will get ability to bear loads. In this paper, aiming at the material characteristic of coal ash, according to the structure of wall filled with core powder, create a simplified calculation model. According to its deformation characteristics and the formula of the frame - shear wall, we can get the equivalent strength of the wall to simplify the calculation to apply to engineering project.

Abstract: To protect Chinese ancient wooden buildings, by simulation means a decayed wooden beam of an ancient building in the Forbidden City was taken as example to study its bearing performances after strengthened by steel bands and bolts.The ancient wooden beam was found to decay on its forepart.The decayed part of beam was considered to be replaced by new wooden part,which connected with old part of beam by bolts and steel bands.Finite element model of the strengthened beam was built considering swivel type of boundary conditions.By contact analysis of ANSYS program, distortion value,compression,tension as well as contact stresses of the strengthened beam under vertical loads were obtained, feasible strengthening suggestions were proposed.Results show that inner forces and distortion value of the strengthened beam are within permission scopes,thus the strengthening method is feasible.

Abstract: On the basis of the theory that natural frequency changes and curvature mode shapes can be employed to determine the locations and degrees of damage of structures, a BP neural network technique with an improved input structure was developed. The two networks were used for diagnosis of structural damage, and structural damages were predicted using gray theory. The results showed that the gray theory to predict the structural damage neural network was applicable to irregular objects such injury problem diagnosis.

Abstract: Steel beam-to-column connections are very important for steel moment-frame structures. Beam-to-column connections have a great influence not only on the seismic performance but also on construction costs and construction durations. These days in Korea, most of the connection details are comprised of the column-tree type beam-to-column connections due to the Japanese influence. But this type of connection is inefficient when it comes to transportation and requires numerous components. The Bolted Flange Plate(BFP) and the Double Split Tee(DST) type weak-axis connections on the other hand are simple in construction and the load transfer is more direct. So, in order to research their respective seismic performance, this paper prepared two specimens and conducted a full-scale test. The study obtained the story drift ratio curves and the total plastic rotation curves of the specimens. Through the analysis of the curves this paper aims to conclude that the two connections meet the requirements pertaining to the Special Moment Frame, which prescribes that the story drift ratio should reach 4%. This paper demonstrates that the BFP and DST type connections display good plastic behaviors.

Abstract: Moment resisting frames are most frequently used in seismic design systems for steel buildings. Following the Northridge and Kobe earthquakes there have been many studies examining the strong axis steel moment connections. In particular, these efforts have been supported by the government in the US. In Korea on the other hand, researches on the seismic behaviours of weak-axis moment connections are difficult to fine even though these connection details have been frequently used as seismic details of local MRF. As a result, the objective of this research is to provide information on the seismic behaviours of welded free flange type(FF) and welded flange plate type(WFP) weak-axis steel moment connections that were quoted by the FEMA. For this purpose, an experimental program was designed and performed with 2 types of weak-axis steel moment connections. From the test results, both FF and WFP type connections revealed to have more than 3% story drift capacity, which satisfy the required performance for OMF systems.