Abstract: A hysteretic model of conventional steel braces consisting of 18 parameters is proposed. This model is able to simulate the hysteretic behavior of conventional steel braces accurately. The collapse-prevention strengthening effect with steel braces for a typical reinforced concrete (RC) frame that was close to the epicenter and collapsed during the Great Wenchuan Earthquake is discussed via push-over analysis and collapse fragility analysis based on incremental dynamic analysis. The result could be referred to for the seismic collapse prevention design of RC frames.
Abstract: Self-consolidating concrete (SCC) has the potential to significantly reduce costs associated with concrete construction. SCC is a highly flowable, nonsegregating concrete that has a variety of advantages over conventional concrete (CC). However, SCC is not without its problems, which can include increased creep and shrinkage, as well as decreased bond and shear strength. The goal of this research project was to evaluate the creep, shrinkage, and shear behavior of a chemically-based SCC mix. One of the benefits of a chemically-based approach is the potential to eliminate the negative side effects of many SCC mixes. The investigation included development of the mix design, construction and testing of creep and shrinkage specimens, and construction and testing of full-scale beam specimens to evaluate the shear behavior. The results indicate that a chemically-based SCC performs as well or better than conventional portland-cement concrete.
Abstract: Green high performance alkali-slag concrete(ASC) was prepared by adding Na2SiO3 and NaOH complex activator in slag. Physical, mechanical and drying shrinkage performance of ASC were studied by workability, strength and drying shrinkage tests. The results show that slump of ASC exceeds 160mm, fluidity and workability is excellent. 28d compressive strength and flexural trength of ASC are 90MPa and 8.36MPa, 7d strength are 83.7MPa and 7.47MPa, which belongs to high–early strenth. drying shrinkage of ASC are ratherish bigger than portland concrete(PC) anytime, but correspond to PC at later period from 28d, anyhow ASC belonged to low deformation concrete but with ratherish bigger early deformation, therefore early keep should be reinforced. drying shrinkage of ASC increase with dosage of slag anytime, but don’t increase with ratio of activator solution to slag linearly. And a suited logarithm prediction model of ASC was established, which can predict the drying shrinkage of ASC.
Abstract: Abstract. The regular grain orientation of granular materials is a common phenomenon in nature. Based on the research of grain shape effect on mechanical property of granular materials, two kinds of idealized shape grain (kind of long rod and square) assemblies with different grain orientation were studied by simulated biaxial compression test using Discrete Element Method. The significant orientation which can be computed as the mean value of all grain orientation is introduced to represent the orientation regularity of granular materials. In order to study the anisotropy, the mobilized friction angle and volumetric strain of assemblies with different significant orientation were obtained under both vertical and horizontal loading. The results show that the regular orientation of grains influences the movement such as motion and rotation obviously; with the increasing of significant orientation, peak mobilized friction angle of long rod grain assembly gradually increases under horizontal loading, and decreasing under vertical loading.
Abstract: By studying alkaline-activated complex systems with coal gangue calcined at 750°C and slag, the results can show that under the action of soluble glass, when the weight fraction of calcined coal gangue was less than 30%, mechanical strength of composite systems may be more than 40 MPa. But when the weight fraction of calcined coal gangue is higher than 60%, the strength of complex systems was decreased faster than that of alkali-activated slag cementitious materials. X-ray diffraction (XRD) method and determination of chemically combined water content were used to study hydration course of alkali-activated cementitious materials. The results can show that the major hydration product was zeolite and the change of chemically combined water content was consistent with the results of strength development.
Abstract: Gap between steel tube and concrete core could be recognized as a type of initial concrete imperfection in concrete-filled steel tubular (CFST) members. This paper is an attempt to study the effect of gap on the behaviour of concrete-filled steel tubular (CFST) columns subjected to eccentric compression. A total 14 specimens were tested and the main parameters were the gap type (circumferential gap and spherical-cap) and gap ratio. The influence of gap on the failure mode and ultimate strength of CFST columns were experimentally examined.
Abstract: For I-girder with high strength steel, it is known that the flexural ductility is considerably decreased by increasing the yield strength of material. Thus, it is necessary to conduct a study for guaranteeing proper flexural ductility of I-girder with high-strength steel. In this study, the evaluation of flexural ductility of negative moment region of I-girder with high strength steel where yield stress of steel is 690Mpa is presented based on the results of finite element analysis and experiment. From the results, it is found that the flexural ductility of the I-girder is significantly reduced due to the increase of elastic deformation and the decrease of plastic deformation ability of the material when the yield strength increases. This study proposed equation predicted flexural ductility of high strength steel in negative moment region. It is also proposed the method to improve the flexural ductility by an unequal installation of cross beam and an optimal position of cross beam. Finally, the effects of the unequal installation of cross beam on the flexural ductility are discussed based on the finite element results and the experimental results.
Abstract: Isotropic pitch fluorides were prepared via the reaction of isotropic pitch with gas mixture containing F2 and N2 in a rotation nickel reactor. Isotropic pitch fluorides were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and elemental analysis. The results showed that the interlayer spacing of the resultant materials dramatically increase from 0.345 nm of the isotropic pitch to the range 0.643 nm to 0.798 nm. Further studies on the diversity of the functional groups indicated that the whole reaction process was composed of two steps, namely, diffusion of F2 inside the voids among isotropic pitch molecules on the surface of the particles and fluorination. The two processes interacted with each other and jointly determined the apparent speed of the reaction. The scanning electron microscopic micrographs showed that the larger bulk of isotropic pitch was gradually desquamated and became small particles, which can be attributed to the crack resulting from the volume expansion of the surface molecules of the isotropic pitch fluorides during the reaction. The final isotropic pitch fluorides were fine particles with diameters of less than 1 µm.
Abstract: By comparison of existing formula of super-long pile group efficiency, combine the geometric feature of super-long pile group with large length-diameter ratio, simplify the original formula, then a suitable method which calculate the super-long pile group efficiency in clay has been proposed. Taking use of test data to verify the formula and results show that: the pile group efficiency from the method accords with the test value very well.