Applied Mechanics and Materials Vols. 105-107

Abstract: Based on one prestressed frame beam in an actual project, both the indirect measuring test and the finite element numerical simulation about the reinforcement prestress are made. The test and simulation results show that the effect prestress obtained from indirect measure methods can reflect the prestress history relatively well. Meanwhile, the indirect measure method has the advantages of low cost and easy operation, which can be exploited and developed in general projects so as to get the stress history of the prestressed reinforcement in time and reduce potential security threat.

Abstract: The relation of tensile strength ＆ temperature stress and concrete fissure was researched firstly , then it showed the causes of late cracks on concrete by theoretical calculation, the result provided a simple theoretical calculation method to avoid concrete fissure. The construction methods to control the fissure was proposed: early strengthening cooling, managing maximum temperature of concrete through lately heat preservation, and overtime to preserving concrete moisture for controlling the late strain on mass concrete. This research has a great significance for controlling the fissure.

Abstract: Based on the relationship between the displacement and the corresponding strain in protective layer concrete during their corrosive expanding, the strain in protective layer arrives the critical strain have been think as the cracking condition, then a certainty critical corrosive ratio model has been constructed in this paper. Considering the probability distribution and the statistical characteristics of concrete protective layer thickness c, reinforced bar diameter d_st and the effectively volume expansion coefficient neff, the Monte-Carlo method have been used to simulate the critical corrosive ratio ρ_cr, its probability distribution has been shown in good agreement with Weibull distribution and lognormal distribution in results. Through the constant current polarization accelerated corrosion test, the critical corrosive model has been validated. With comparison of critical corrosive ratio which be obtained with the test and the model simulation results respectively, where a good agreement have been shown.

Abstract: A workshop’s roof is designed to use steel tube trusses with the span of 24m. There are three kinds of variable cross-section splice joints of the roof truss bottom chord. Nine splice joint specimens, three for each kind, were tested to obtain their tension capacity and failure modes. A special test setup is designed to introduce the tension load to the splice joint specimen. The paper detailed introduced the test setup and method, discussed the failure load and failure mode of the joints. Experimental research indicated that the bottom chord splice joint with variable cross-section of the roof is safe, reliable, having high bearing capacity. The research also validated the correctness of the design and calculation, and provided the basis for the application of such joints in the engineering practice.

Abstract: Serious damage and collapse of steel towers were easily induced by the ice disaster, the wind disaster and so on. After the disaster, to ensure the overhead transmission line working safely, it is necessary to strengthen the structure of the damaged tower perpetually, but there are few strengthening methods for the tower assembled by angle-shaped members at present. If an identical angle-shaped member is connected on the side of the existing angle-shaped member through bolts, the mechanical performance of the damaged tower can be improved effectively. In this paper several methods for strengthening the angle-shaped tower is proposed, and the mechanical behavior of the strengthened member of the tower is discussed experimentally, and some design suggestions for strengthening the towers are given.

Abstract: Event-based emergency handling is a high-efficiency decision process of the choice of emergency information resources, the acquisition of emergency knowledge, and the optimizing arrangement of emergency information resources through the logical relationships between emergencies and related emergency information resources. With the development of emergency rescue theory and computer science and technology, the realization of emergency management informatization and intellectualization is of far reaching importance, on the basis of the establishment of event-oriented handling logical relationships, the construction of emergency management platform, the unified management of emergency information resources and the on-line emergency handling. Centered on emergencies, this paper discusses the respective corresponding relationships of emergency and emergency information resources, emergency knowledge, emergency response plans, paradigm cases, relative laws and a series of decision actions on emergency handling, risk assessment and risk analysis etc. It also illustrates the functions and meanings of the correspondence configuration.

Abstract: The reliability analysis for differential expansion of steam turbine is discussed extensively. The ultimate state equation of differential expansion of steam turbine is proposed according to stress-strength interference theory. Based on the premise that the probability distribution of random parameters has been known, the differential expansion of steam turbine is analyzed by saddlepoint approximation method. The probability density function and cumulative distribution function of the ultimate state equation are accurately and quickly obtained by the way of saddlepoint approximation and, as a result, the saddlepoint approximation method is proved accurate with high computing speed in comparison with the Monte-Carlo method. Therefore, the application of the saddlepoint approximation method is accurate and efficient.

Abstract: In the past two decades, there are many modal-based indices have been proposed for structural damage identification. In the present study, a modal of a 38-story building was tested on a shaking table to subject to four levels of earthquake, and the acceleration responses at nine floors of the structure are measured and used to construct five damage indices respectively. The experiment makes it possible to verify the applicability of vibration-based identification methods in identifying structure damage without use of structural finite element model. Damage in the structure after experiencing different attacks is evaluated via five modal-based damage indices respectively .By comparing the solution of above indices, it is concluded that the five modal-based indices didn’t have consistency in the identifying and localizing the seismic damage.

Abstract: Prestress strands are the key parts of the prestressed structure, and the stress of the prestressed strands is one of the important indicators to assess prestress component security. Unfortunately, up to date, there are no qualified techniques to handle this issue due to that it is too hard for sensors to survive the harsh construction environments and the time-dependent service life of prestressed structures. In this paper, a novel smart steel strand based on the technique of GFRP-FBG rebar was introduced, and its sensing principle has also been given in details. The novel smart steel strand has been tested by serious experiments to research its mechanical and sensing properties. The monitoring results show that the mechanical properties of the smart strands are similar to ordinary strands, and its sensing properties include that distinguish-ability is less than 0.466% F•S, hysteresis less than 2.15% F•S, repeatability less than 1.32% F•S, linearity less than 0.86% F•S, and overall accuracy less than 2.67% F•S. Such kind of GFRP-FBG smart steel strand can be used for both structural and functional materials and applied in practical prestressed structure.

Abstract: Bridge deck pavement material requires sufficient compressive strength, flexural strength, and bending toughness. The bridge structures inevitably bear the impact of the external adverse environment, so pavement layer material should also have impermeability, freeze-thaw resistance and corrosion resistance. This text studies complex concrete of steel fiber and polypropylene steel-wire-like fiber, and compares different dosage and type of fiber on mechanical performance of concrete. The results show that complex fiber concrete has better mechanical performance and durability, and is an ideal choice as bridge deck pavement material.