Applied Mechanics and Materials Vols. 578-579

Abstract: When large building being renovation, the new fire control design problem has being came out. A comprehensive transformation of architectural analysis and performance-based fire safety design is very important. In this paper, performance-based fire safety design in the transformation of engineering for the issue, analyze and explain the design of specific operating plans and evacuation design should be pay attention to.

Abstract: A loading device was developed in this paper basing on corrosion experiments of conventional metal and cable through collecting previous research about cable stress corrosion. This newly developed device makes loading possible under low frequency alternating stress and environmental corrosion coupling. Through the different condition for the steel strands corrosion experiments show that the speed of steel strand corrosion in alternating stress load is faster than non-stress and static-stress in the same conditions. The co-influence of corrosion and stress to the ductility of strand, the influence of alternating load peak and frequency to corrosion velocity were respectively analyzed. Three groups of verification experiment results show that the plastic deformation effects caused by the tension are much larger than the corrosion. Corrosion velocity of the specimens that reached threshold value under tensile stress is 1.47 times faster than the other three peak load specimens. And the ductility is not sensitive to low frequency, the ductility of the specimen is associated with tension and corrosion.

Abstract: The present study concerns a development of cement-free concrete using ground granulated blast-furnace slag (GGBS) with alkali-activators such as KOH, NaOH, and Ca (OH)₂. To find out the development among three different activators, the concentration of hydroxyl ion was kept 0.5%, 1.0%, 1.5%, 2.0% and 3.0% by weight of binder irrespective of cations. The setting time was measured by penetration resistance immediately after casting of mortar. The development of compressive strength was measured at 7, 14, 28, and 91 days. The pore structure of cement-free mortar was examined by the mercury intrusion porosimetry (MIP) and rapid chloride penetration test (RCPT). Simultaneously, grew sample was used to microscopically observe at the XRD. For strength of cement-free mortar, mixed with KOH or NaOH was as high as OPC at 3.0 % by weight of binder. However, the compressive strength of cement-free concrete mixed with 3.0 % Ca (OH)₂ by weight of binder had just half strength of OPC mortar. Cement-free concrete activated with NaOH and Ca (OH)₂ had higher total pore volume, however, it had lower ionic penetrability due to the pore type which mostly consist of gel pores. For pore structure of cement-free mortar mixed with KOH, the total volume had similarity to that of OPC mortar, however, it had lower penetrability. Therefore, it may have higher resistance to chloride transport than that of OPC mortar.

Abstract: Three-dimensional reconstruction and quantitative calculation were performed by X-ray computerized tomography to propagate cracks in paste, mortar, and concrete specimens. Cracking could be observed, and the number and width of cracks increased with increasing strain and load. In mortar and concrete specimens, the number and width of cracks remained unchanged with increasing strain and load; however, a sudden increase in the number and width of cracks nearly destroyed the specimens. Cracks developed along the interface of the aggregate and the mortar in the mortar specimen. In the concrete specimen, cracks continued to grow through the coarse aggregate when cracking occurred along the stress direction. However, cracks developed along the interface of the aggregate and the coarse aggregate when cracking was independent of the stress direction.

Abstract: Monte Carlo Simulation and Response Surface Method are two very powerful reliability analysis methods. Normally, in the reliability analysis of complex structures, the limit state function often can not be expressed in a closed-form. Usually, the codes for probabilistic analysis need to be combined with finite element models. ANSYS Probabilistic Design System (PDS) has provided a package to conduct probabilistic analysis automatically. This paper is going to compare the performance of these methods through an easy engineering problem in ANSYS. The results are going to be derived to show the feature of applying the corresponding reliability methods.

Abstract: Corrosion of steel is the most important cause of failure of reinforced concrete structures. Corrosion inhibitors are one of the prevention methods used to avoid steel corrosion in the presence of chlorides. In this study, the effectiveness of the amino alcohol-based corrosion inhibitor has been evaluated by long-term steel corrosion monitoring in reinforced concrete. Also its influence on selected concrete properties is studied including compressive strength and chloride diffusion test. The inhibitor was added to the concrete mixture. The results show that the corrosion inhibitor is effective in delay corrosion initiation compared to the control samples. The addition of inhibitors not only improves the compressive strength of the concrete but also reduces the penetration rate of chlorides into concrete.

Abstract: In the recent past an increasing number of failure events have been observed for offshore structures due to exceptional environmental loading conditions such as large waves. The occurrence of these failure events indicates a possible improvement in the traditional modeling of environmental characteristics, which are the basis for the load models for structural analysis and design. In this paper, the seasonal and directional effects in the modeling of the significant wave height for structural reliability analysis are studied. The peak over threshold (POT) method is selected to model the extremes in the non-stationary point process for the wave heights. The time-varying parameters are taken into account with a cyclic changing pattern to reflect the seasonal behavior. Both the extreme values and the storm occurrence rate are investigated in the different seasons. The results are utilized for the load characterization of offshore structures to investigate their sensitivity to the changing seasonal effects in reliability analyses. An example of selected structure is discussed.

Abstract: The paper discusses general theoretical and practical aspects of the emerging probabilistic and non-probabilistic approaches for uncertainty treatment in finite element analysis. Based on rough set theory, a new methodology for structural reliability computation is presented. The uncertain parameters of structures are expressed by rough variables. The structure reliability index is computed by rough function and metric. It is valid, and efficient in physics and geometry. Examples of practical application are given.

Abstract: Because of fuzziness, uncertainty of structure and researchers practical experience, it is more practical to express the relative importance of indexes with interval number. Firstly, according to researchers indeterminate judgment matrix, the upper and lower bound matrixes are formed; secondly, the similarity and the differences of the upper and lower bound matrixes of the relative importance matrix from different experts is studied by using the similarity theory of vector; lastly, certainty factor of researchers according to the upper and lower bound matrixes can be calculated, and the average value is regarded as the researchers certainty factor. The certainty factors of researchers upper and lower bound matrixes are consider together, the researchers experience is fully considered and the error from indeterminate judgment matrix to indeterminate judgment matrix is avoided. The result affords basis to calculate the weight coefficient, the research result comparing with the other method showed that the computation accuracy in this paper was very high.

Abstract: The mechanical properties of concrete and aggregate components only, with the ratio, the intensity level, reinforcement situation, but also on the specimen geometry and other factors are closely related. This paper describes the use of mathematical methods to establish a theoretical model of the mechanical properties of concrete, and then be verified by testing or engineering practice, the results reflect the true mechanical properties of the actual structure of concrete, numerical results reveal the physical mechanism of concrete material damage, particularly the existence of internal material impact on the mechanical properties of concrete and size effect of meso defects.