Applied Mechanics and Materials Vols. 94-96

Abstract: Global climate change, including climate deterioration and extreme weather events, has serious impacts on reliability of bridge superstructure. Global warming and increasing velocity of wind associate with the increase of CO2 level play a dominate role in reliability degradation. For the highway bridge in offshore environment, a main factor of reinforcing steel corrosion is the invasion of chloride ion, which can cause durable damage of the structures. Moreover, temperature rises will increase corrosion rates. In addition, changes in maximum wind speeds may increase expected wind loads on bridge structures. This paper develops a reliability analysis model to assess the reliability degradation of the highway bridge superstructure under (i) base case, (ii) temperature rising case, (iii) wind speed changing case, and (iv) combination of case (ii) and case (iii). The process is illustrated by studying the reliability of a offshore highway bridge using simplified models of the structure. It is demonstrated that the reliability degradation will be greatly accelerated taking account of climate change. The life expectancy of the structure will be 10 years and 70 years lower than base case if the target reliability is 4.5.

Abstract: The cantilever beam model of tall building structure which includes lateral wind load and vertical gravity coupling has been established in the paper. The form of finite difference has been concluded from equations of the model acted on static wind load. Amplified coefficients of bottom moment and top displacement are calculated and analyzed. The result shows that gravity second order effect of tall buildings will be enhanced when ratio of gravity rigidity or ratio of bending and shearing rigidity increase.

Abstract: Capillary absorption is essential to mass migration in cementitious materials. Based on previous studies, capillary rise involving gravity effects is of much greater interest in porous building materials because equilibrium is attained at the wetting front when gravitational force balance the capillary force. In this paper, two different solution forms, semi-analytical and numerical, are presented to account for the gravity effect for realistical prediction of water penetration process. The former is stable against small perturbation proved by Stepanyants [1]. The comparison of predicted results by the two methods confirms the reliability of the technique in estimating water transport.

Abstract: Walls of the LNG storage tank are mainly built by the prestressed concrete, but the material of prestressed concrete is complex nonlinear materials. The characterized of concrete is that it can bear very big pressure, but cannot bear the pull. The LNG storage tank is a typical pressure vessel; it has a great significance to research the stress distribution and the cracks of the wall of concrete. In this article, using the ADINA numerical simulation software to establish separate model of reinforced concrete, and research the cracks and the failure modes of the concrete in the normal using state and leakage state by using the stress contour of prestressed steel and ordinary steel and concrete crack map of external wall. Identify the most dangerous place of the storage tanks in several of state. It can provide theoretical basis for domestically independent design and construct LNG storage tank in the future, and then provide domestic reference for crack treatment of LNG storage tank.

Abstract: In the recent years, people begin to concern more about the development of new energy source, because of the global economic development and more stringent environmental requirements. The wind power is rapidly developed for its low price and it’s friendly to environment and the wind energy and building integration also becomes a very important mode to develop new energy sources. The wind driven generator and high-rise building structure were integrated, and ANSYS was used to complete the static analysis of the equivalent dead load action of high-rise building with wind driven generator under six different wind pressure. By comparing the results of the calculations, the feasibility of the wind energy and building integration was initially verified.

Abstract: This paper presents calibration of service temperature on the prediction of long-term performance of GFRP bar in reinforced concrete structures. Two approaches, based on monthly average temperature and yearly average temperature are proposed to simulate the real service condition on the RC structure for the study on long-term performance. A design example for the comparison of results by the two approaches is presented.

Abstract: This article surveys and studies the design, construction and verification codes related to durability of concrete bridges both home and abroad, contrastively analyzes their requirements on environmental effect, durability design, construction and testing indices, and finally brings up the durability index system suitable for Chinese concrete bridges which covers the four hierarchies of environment, material, components and structure, and also considers the three phases of design, construction and verification.

Abstract: The detection of localized defects such as cracks and corrosion in pipes using guided waves has been shown to be an effective nondestructive evaluation technique for structural health monitoring (SHM). Cross borehole tomography in seismology is introduced into the guided wave inspection of a pipe when the pipe is considered as an unwrapped plate. Guided waves propagating in pipe with a crack defect are simulated using the finite element model and the arrival times for the fastest modes are extracted and sent to the tomographic algorithm. The tomographic reconstruction is based on the simultaneous iterative reconstruction technique (SIRT). For some cylindrical shell geometries such as stacked storage tanks, access to the entire circumference of the structure could be impractical or even impossible, three different image fusion techniques are used to enhance the image equality reconstructed from the incomplete datasets. The results show that the defect is more pronounced after imaging fusion.

Abstract: The method of construction about the concrete-filled thin-walled square steel box short columns is studied in this paper. Composite steel is designed inside of the concrete-filled thin-walled square steel box short columns. The use of the transverse steel bars’ constraining effect on the concrete and bonding effect on the walls enhances the local stability and bearing capacity of the wall. According to the concrete strength C30/C35/C40 and the thickness of the steel 1.25mm/1.75mm/2.5mm,42 short column specimens are made and the size of all specimens is 200mm×200mm×690mm.The static bearing capacity test is done by the 500-ton electro-hydraulic serve testing machine. The whole curve is made .The composite steel and the thin-walled steel’s strain is tested. The results show that this method of construction has a certain effect on constrainting concrete and bonding effect on the walls, significantly improving their mechanical properties, increasing the carrying capacity and ductility, and it is easy to be accomplished.

Abstract: Because of lacking a rigid method of setting the initial nodal temperature on the joint face, the accuracy of temperature simulation would be affected in concrete dam. Based on finite element method (FEM) and principle of thermal conversation, we validate and extend a new method of setting the initial nodal temperature on the joint face in this paper. The result of temperature field simulation shows that this method has good accuracy in three-dimension temperature field simulation.