Advanced Materials Research Vols. 250-253

Abstract: In the present work, the Cosserat micro-polar continuum theory is introduced into the FEM numerical model, which is used to simulate the strain localization phenomena under static and dynamic loading conditions. The numerical studies on progressive failure phenomena, which occur in a panel, characterized by strain localization due to strain softening and its development, are numerically modelled by two types of Cosserat continuum finite elements, i.e. u8ω8 and u8ω4 elements. It is indicated that both two Cosserat continuum finite elements possess better performance in simulation of strain localization. Because of the presence of an internal length scale in Cosserat continuum model a perfect convergence is found upon mesh refinement. A finite, constant width of the localization zone is computed under static as well as under transient loading conditions.

Abstract: A new method taking the second derivative of low-level axial vibration modal shape as damage index is presented on the basis of theoretical derivation axial vibration differential equation and analytical solution of three kinds of support form. The index is very sensitive to damage location and damage degree. In addition, the effect of point number is analyzed and results showed that with a few points can still calibration damage well.

Abstract: In order to investigate the different mechanical behavior of column-bracing system between fixed-ended and pin-ended column base, a large number of column-bracing systems with fixed-ended and pin-ended column base were studied using the ANSYS program, in which random combination of the initial imperfections between columns and braces was well considered by the Monte Carlo method. Based on the above comparative study, probability density function of the bracing force was found through probability statistics and the design bracing force is obtained. The results show that the ultimate load-carrying capacity and the bracing forces of the mid-height horizontal braces of column-bracing systems with pin-ended column base are higher than that of column-bracing systems with fixed-ended column base, and the higher ultimate load-carrying capacity of the former more significantly increases the bracing forces of the mid-height horizontal braces; that the bracing forces of the mid-height horizontal braces in compression or in tension have also randomness because of the randomness of the initial imperfection of both columns and braces.

Abstract: In this paper, the experimental method is adopted to study the mechanical performance of corroded high-strength steel bars. HRB400 and HRB500 with different diameters are corroded by electrifying accelerated corrosion in the laboratory, followed the tension test on these corroded bars with different corroded degree. The studying of the corrosion condition and mechanical performance of corroded high-strength steel bars lay the basic foundation for the analysis and research on their selection and relevant structural resilience which provide the reference basis for engineering practice.

Abstract: Foundation piles of the offshore oil platforms in Bohai Bay are usually longer than 100m with a diameter larger than 2m. Thus, thoughtful drivability analysis has to be performed in the design stage because of the high cost and time limitation. It has been shown that to judge if the soil column inside the pile is fully plugged, which will make the pile behave as close-ended, will strongly influence the accuracy of drivability analysis. Engineering practice repeatedly indicates that the currently widely used methods for soil plug judgment often give incorrect results, leading the designers to make a wrong decision. It has been found that this problem is caused by the ignorance of the bearing capacity provided by the soil surrounding the pile. Based on the Terzaghi’s bearing capacity calculation method for deep foundation, a new approach for judging soil plug status is put forward, in which the surcharge effect has been considered and the dynamic effect coefficient is included. This approach has been applied to some practical engineering projects successfully, which may give more reasonable results than the currently used method.

Abstract: In order to study the bending capacity of steel and concrete composite girder with concrete filled tubular flange (SCCGCFTF), a formula for the ultimate bending capacity of normal section was proposed based on perfected elastic-plastic model for steel and restricted concrete model for inner high performance self-compacted concrete. Analysis result shows that the mechanical behavior under static load can be divided into two phases in accordance with confining effects. Confining effects strength of the concrete-filled steel tube flange was relation to the restriction effect coefficient ξ. The ratios of the calculated value to the experimental ultimate bending capacity were between 0.93 and 0.97. Therefore, the theoretical formula is relatively safe to calculate the ultimate bending capacity.

Abstract: In order to promote the applications of steel and concrete composite girder with concrete-filled tubular up-flange (SCCGCFTF) in practical bridge engineering, some actual issues for SCCGCFTF bridge structures have been discussed. The finite element static and dynamic analysis models of SCCGCFTF and conventional composite I-shape girder (CCIG) bridge structures were established. Then the stiffness, stress and dynamic characteristics of these composite girder bridges were studied and compared. Based on the numerical analysis results, the mechanical characters of SCCGCFTF bridges are obtained, and some design rules for SCCGCFTF bridges are also proposed. The analysis results show that SCCGCFTF bridges have high practical engineering application value.

Abstract: A full scale model of orthotropic deck panel was designed and fabricated referring to the common steel box girder bridges used in China. Experiment was conducted to test the behavior and fatigue performance of the orthotropic steel bridge deck under the actual truck wheel load. The loading test was conducted on the platform specially prepared. Measurement of the over-all structure and the fatigue sensitive details was made to evaluate the performance of the panel. For each gauge position, the results are presented as the form of influence lines.

Abstract: When earthquake occurs, it is in near-fault that the most serious damage happens and velocity pulse appears. Velocity pulse could have huge potential to destroy the structure in near-fault. The set of records at Bajiao Station is one of the three famous near-field sets of strong ground motion records whose PGAs are the largest in all the sets of records obtained from the mainshock of the Great Wenchuan Earthquake. Our research is to identify the pulse-like characteristics from the set of records at Bajiao Station. It is found that velocity pulses in the records are “hidden pulses”.

Abstract: We study the characteristics of ground motion fields and peak ground motion attenuation relations during the 2008 Ms 8.0 great Wenchuan earthquake by using 198 sets of three-component acceleration time history recordings. To provide a comparable result to other earthquakes, we first rotated the east-west (EW) and north-south (NS) orientated ground motion to fault strike normal (FN) and fault strike parallel (FP) directions. Through comparison of the near-field peak acceleration fields and peak acceleration attenuation relations, there obviously exists a rupture directivity effect in the peak ground accelerations. The amplitude in the rupture propagation direction is higher than that of the opposite direction. And the closer the station to the fault plane, the smaller the difference of ground motion amplitude between the two opposite directions.