Advanced Materials Research Vols. 671-674

Abstract: A new type of composite structure, precast concrete tube column is proposed, and its axial compression performance and the seismic performance of beam-column joint are studied. Nine groups of precast concrete tube column models and three groups of common solid column contrast models with the same outer diameters (600,800,1000mm) were established by software ABAQUS, and a beam-column joint model for horizontal low cyclic loading was established combining with practical project. The results show that the ultimate bearing capacity of precast concrete tube column is higher than that of the common solid column with the same outer diameter by 5% to 20%, and it increases slightly as the thickness of tube increases. Displacement - load hysteresis curve of the beam-column joint is relatively full under cyclic load, and the slope of skeleton curve decreases slowly, which provides an important basis for engineering applications.

Abstract: Concrete filled steel tubular (CFST) structure is a new type of structure. Assuming that concrete filled steel stub frame-shear wall is continuous elastic structure with infinite degree of freedom, free vibration equation is built. Furthermore, the effects of semi-rigid connection on natural periods and frequencies are studied. The formula to calculate the coefficient of natural periods is deduced. ANSYS is employed to determine the modal analysis. The results obtained from finite element analysis are consistent well with those obtained from formula. The results show that semi-rigid connections tend to increase the natural period. However, the effect on higher modes is negligible. The seismic design suggestions of the semi-rigid concrete filled steel stub frame-shear wall are proposed. The proposed methods may supply references for the engineers.

Abstract: The dynamic behavior of semi-rigid concrete filled steel tube frames is different from that of their rigid counterparts. ANSYS was employed to model ten-story concrete filled steel tube frames with three different connection types（ rigid, semi-rigid and flexible）. Natural period, inter-story drifts and total drifts of the frames subjected to design response spectra excitation were analyzed. Time-history analyses when the frames subjected to two different earthquakes were studied. It seems that connection flexibility noticeably increases the natural periods of the lower modes, however, its effect on higher modes is negligible. The use of rigid frames may not be the best option in seismic region. The seismic design suggestions of the frames were proposed.

Abstract: Traditionally, spiral case structure is classified as non-member bar reinforced concrete structure. It is improper to calculate reinforcement area according to the area of tensile stress figure, which often causes a lot of waste of reinforcement; it is particularly true for the spiral case structure with steel liner. In combination with the practice of a spiral case of the hydropower station, the different schemes are proposed by 3-D nonlinear FEM software ABAQUS to study the feasibility of thinning steel liner in this paper. It is indicated that magnitude of steel liner and the hoop reinforcement stress is of no obviously increasement, damaged region of concrete is of no significant variation and the cracking range of peripheral concrete is of the requirements when the rate of steel liner thinning is tiny. When the thinning rate is 10%, there is a significant increase in crack width, but it still can meet the requirements of the specification. Although the magnitude of the stresses is not beyond the strength requirement, the maximum cracking width of concrete is over the designed standards when the rate is up to 30%. In this case, the crack width is controlled by collocating the more reinforcement in local positions. It is concluded that steel liner thinning is reasonable and feasible; what’s more, the magnitude of thinning is very large when the more reinforcement are collocated without prejudice to construction. It can provide references for optimization of the steel liner for the similar projects.

Abstract: The axial symmetric model has been widely used in the research and design of spiral case structure in hydraulic power station due to its convenience, however, instead of a continuous entity, the fixed guide vanes are discretely distributed around the vertical axis of the unit, and there are some different opinions on the simulation techniques for the fixed guide vane in the existing research. Commonly used processing methods for fixed guide vanes in the spiral case axial symmetry model are summarized and two new simulation techniques on the basis of existing research are proposed. Static analyses for a practical spiral case with cushion layer are conducted using 4 axial symmetry models and a 3-D FEM model. The influences of simulation techniques for fixed guide vanes on the stress and their distribution of steel liner, concrete and fixed guide vanes are investigated. The rationality and applicability of each simulation technique for fixed guide vanes are discussed.

Abstract: In the context of ultimate bearing capacity of steel lined reinforced concrete penstock (SLRCP) containing flaws, the use of the elastic modulus reduction method (EMRM) in conjunction with curve beam based internal force calculation is presented. The corrosion models for steel bar and lining are introduced from the literature. The SLRCP is considered bearing load together with lining and reinforced concrete, and its internal force is determined based on a simplified curve beam model. The element bearing ratio of SLRCP is given through the internal force and sectional strength, and is employed by the EMRM. The change of ultimate bearing capacity of some typical SLRCP within their operating life is then evaluated.

Abstract: According to the actual structure of submarine flexible pipe, considering the combined effect of internal pressure and transverse load by wave-current flow that is based on 50 year return period wave statistics data of Cheng Dao sea area, ANSYS finite element model of flexible pipe is established. The influence of internal pressure and suspension length on the axial stress of steel wire reinforcement layer and the Mises stress of rubber layer was analyzed. Comparatively, suspension is the main cause for the failure of steel submarine pipeline, but could hardly lead to the failure of submarine flexible pipe, which shows that flexible pipe is stronger applicable for submarine pipeline.

Abstract: The slewing bearing of the full-revolving super large lifting equipment bears all loads above the rotating platform. Due to the effect of bending moment, the load conditions of the slewing bearing structure is complex and large, which leads to the non-uniform of stress and uneven deformation and final seriously affects the work performance of lifting equipment. The numerical example in this paper considers three kinds of sliding-friction models between slewing bearing structure and orbit. By numerical analysis results, we adjusted the structure arrangement and stiffness distribution. Finally the non-uniform of stress of the slewing bearing structure has been improved and tended to be uniform. Thus the paper presents a new approach for the design of the slewing bearing in super large lifting equipment.

Abstract: A series of aero-elastic experiments were conducted to identify the aero-elastic parameters of 2-D square prisms under the interference effects of the tandem arranged upstream prism wake. The wake induced across-wind vibration of springs supported downstream prism was measured close to the lock-in wind speed in smooth flow. To identify the aero-elastic parameters, such as Y1,  and Y2, the trace-to-resonance method was adopted with the decay-to-resonance rules. It is well contributed to build up the predicting model of the aerodynamic loadings with the measured results of the vibration of prism under the wake interference effects with these parameters. With the aero-elastic parameters we collected in the various experiments cases, an empirical predicting model with the neural network predicting technique were constructed in this study. It is found that more clear trend of aero-elastic responses will be arose from this empirical model.

Abstract: A full-scale, three-storey, light timber frame of a residential house was tested in-situ to investigate the effect of structural damage, temperature and relative humidity changes on its natural frequency. As expected, test results provide the evidence of the significant influence that temperature and relative humidity changes have on the natural frequency of the test structure. Regression analysis of the test results revealed that the natural frequency change of the structure is generally in a linear relationship with the variation of both relative humidity and temperature. Furthermore, variation of natural frequency induced by relative humidity and temperature may be much stronger than that induced by damage of structural members. It is concluded and recommended that the effect of temperature and relative humidity change should be considered when the natural frequency is used as an indicator for damage identification of timber constructions.