Applied Mechanics and Materials Vols. 94-96

Abstract: In this paper, the fire resistance performance of the unprotected two-layer and two-cross planar frame, which is composed of concrete filled steel tubular columns and steel beams, was analyzed under local fire by ANSYS. After analyzing the structure with the method of hot - structural coupling using standard heating curve ISO-834, some consequence were obtained such as the regularity of temperature field distribution of beams and columns and the fire endurance and critical temperature of the structure. It turned out that the bottom flange at the end of the beams appeared local buckling when the structure reached the limit state by fire, and the first plastic hinge appeared at the end of beams. Furthermore, because the horizontal displacement of column is small, the overall collapse of structure can be avoided effectively.

Abstract: Toona ciliata, fast-growing timber species, located in the tropical and subtropical region. In order to explore how to make better use of Toona ciliate, its chemical composition was investigated in this paper. The results show that: Cold water extractive was 1.02%. Hot water extractive was 3.39%. 1% sodium hydroxide extractive was 15.45%. Ethanol-benzene extractive was 1.53%. Content of cellulose was 48.35%. Content of acid-insoluble lignin was 24.92%. Content of holocellulose was 76.45%. Content of hemicellulose was 28.1%. pH value of wood was 6.33. Through comparing with other species, high content of cellulose and low content of extractive suggested that Toona ciliate was ideal material for pulping and board making.

Abstract: Open circular holes with a certain size in beam web at 1/6 span is a new method to improve the seismic behavior of steel moment frames. Based on the results of elasticity theory, analytical model of frame with opening web is proposed, and analysis and verification with nonlinear finite element method (FEM) are conducted. Results show that, beam with opening web at 1/6 span can significantly reduce the axial stress of beam flange near the beam-column connections. It is helpful to achieve the design criterion of strong connection and weak member, and also to simplify the connection construction. If the diameter of web opening is appropriate, beam plastic hinges can move inward to beam section at opening web, and has little effect on bearing capacity, stiffness, energy dissipation capacity and ductility of frames. The method of web openings and the size range are presented at the end of this paper.

Abstract: For the sake of safety of structures subjected to abnormal loadings, damper could be one of the effective devices to reduce the responses by the energy dispassion functions. Key points in the process of development and application of damper and aseismatic engineering are narrated. Due to the highly nonlinear behavior properties, most of the case studies aim on these kind of dynamic analysis only working on structures with elastic linearly behavior systems. In addition to the nonlinearly behavior of damper devices, structures behave into nonlinearly as well when subjected by abnormal excitation, for instance, severe earthquakes. Materials respond into nonlinearly beyond yielding or plastic hinges occurred somewhere in the controlled structures. Proper software package is used to calculate the responses of simple portal frames which are controlled with dampers allocated. Both of structures and damper devices are considered and behaved according to its nonlinearly properties. Responses beyond yielding of material are rationally analyzed and revealed in time history expressions.

Abstract: Early shrinkage cracking of high performance concrete is a current hotspot of research at home and abroad.In order to make full use of local lithium-slag resources in Xinjiang,We use lithium slag as admixture of concrete to research its early-age anti-cracking capability under low water binder ratio. Ring method test on the influence of the dosage of lithium slag on its early-age anti-crak capability of concrete under the conditions of the same surface area (950m2/kg) and water binder ratio(0.27).We have obtained the best dosages of lithium slag which can resist early-age craking of concrete by monitoring concrete strain and observating concrete cracks. Therefore, the 30%dosages of lithium slag is the best for early-age anti-crack capability of concrete.

Abstract: With the depth of coal mine increasing, it appeared a phenomenon of rapid floor heave in some roadways in a short time, which threaten greatly to the normal mine production and the lives safety of workers. The causes and control measures about rapid floor heave are analyzed in this paper. Which has a certain reference values for preventing and controlling rapid floor heave in deep mine.

Abstract: The long-span steel structure is usually used for the stadium, exhibition hall, airports, railway stations and other buildings, and these structures often have an intensive staff, stored supplies are relevant to people's livelihood and so on. If these buildings collapse under the fire, it may cause heavy casualties and property losses, so it’s necessary to make a further research on its fire resistance performance. In this paper, make a fire scenario simulation to the Qingdao North Station main station by using fire simulation software FDS, in order to be sure the increased temperature of components. Then calculate stress of components under the most unfavorable fire temperature with finite element software "Midas" to make sure those components which need a fire protection. Finally, according to the analysis results to determine fire protection scheme, reduce unnecessary waste or local protection can not reach the requirements. This method of fire protection in the paper can provide reference for similar projects.

Abstract: Reinforced concrete (RC) structures taking full advantages of concrete and reinforcing steel bars are widely applied in civil engineering. Concrete bridges are subjected to alternate loads as well as static loads, much importance should be attached to their fatigue. Reinforced concrete beams are the elementary members of concrete bridges. Fatigue failure mode and fatigue life prediction of normal or high-strength RC beams were the research focus at home. The fatigue behavior of low-strength RC beams was studied through four-point bending fatigue test in the paper. The test results indicated that all beams fractured for concrete shear failure, which made the fatigue life of low-strength concrete beams drop greatly compared to that of normal or high-strength concrete beams, because the fatigue failure of normal or high-strength concrete beams were caused by the fracture of one or more reinforcing steel bars; the mid-span deflection development of low-strength RC beams had three phases, and the middle phase occupied about 90% of whole fatigue life, also in the second phase the mid-span deflection developed linearly with the increasing of cycle numbers. This research work provides necessary basis for the fatigue life deterioration of low-strength RC beams.

Abstract: Response spectrum curve is the base of seismic design of structures, and mode-superposition response spectrum method is a practical design method of structures. Damping adjustment factors and shape parameters have been adjusted in the new Chinese code (2010) for damping rate is not equal to 0.05. Then, a new mode superposition response spectrum method combined with continuum method is introduced in this paper. Finally, the earthquake shear of a shear-wall structure’s bottom is calculated, and the results of the new method are compared with that of traditional method implemented in PM-SATWE software which is widely used in architectural design institute. The contrast results show that the new method is available and has a good accuracy.

Abstract: A nonlinear finite element model is developed to study the behavior of square concrete-filled steel tubular(CFST) column and reinforced concrete (RC) column with the same quantity of material and cross-section sizes under eccentric load using ANSYS software.The results indicate that the bearing capacity of CFST column is about 30% greater than RC column and the ductility of CFST column is much greater than RC column under the same conditions. Eccentricity and slenderness ratio have same effect on the bearing capacity of both, which are drop.