Key Engineering Materials Vols. 452-453

Abstract: The Wenchuan earthquake occurred on May 12, 2008 (Beijing Time) caused great economical loss and large amount of buildings were destroyed. Many of single-story reinforced concrete industrial buildings in Hanwang town located in the highly seismic region were damaged, and the damaging phenomenons are very typical. According to the damage survey and analysis of typical seismic damage for the single-story reinforced concrete industrial buildings located in Hanwang town, the damage distribution and failure characters of these buildings are summarized in this paper. The single-story reinforced concrete industrial buildings which were designed according to current seismic design code have better earthquake resistant behavior than those old single-story reinforced concrete industrial buildings and the damaging phenomenon show some new features. Finally, combining current seismic design code of our country and the earthquake damage lessons, some reasonable suggestions on the work of seismic strengthening and earthquake resistant design of the single-story reinforced concrete industrial buildings have been given.

Abstract: The creep experiments are performed under the various stresses at 595°C, 610°C, 640°C and 670°C for P92 steel which broadly used in USC plant pipeline. The specimens are taken from the extrados part of a new manufactured main steam elbow. A series of integrated creep curves are obtained, and the maximal test time last over 13000h. The relationship between the minimum creep rate and stress at different temperatures is explained by Norton formula. Both the 105 h creep rupture strength and stress of 1% creep strain in 105h of P92 steel at the four above temperatures are extrapolated with a list by using the Monkman-Grant formula, which are consistent with the reference experiment data at 600°C and 650°C. Meanwhile, damage during the creep process is discussed applying Norton creep damage formula and θ function method.

Abstract: The effects of humidity and ultraviolet radiation aging on fatigue properties of carbon/ bismaleimide composites and coating protection action were presented. Specimens with central hole are made of carbon/bismaleimide laminates. Compression-compression (C-C) fatigue tests under normal lab environment were operated respectively for four groups of specimen, (1) specimen under normal lab environment, (2) specimen under UV radiation aging with dryness, (3) specimen under UV radiation aging with moisture, and (4) specimen with coating under UV radiation aging with moisture. Variance analysis of experimental outcomes gave significances of the environment effects on C-C fatigue life of specimens. The results reveal that UV radiation have remarkable effects on the C-C fatigue life of the composite laminates under the same humidity, whereas combined action of UV radiation (300MJ/ m2) and humidity have no significant effects on the C-C fatigue life. Coating can provide effective protect the specimen from UV radiation aging.

Abstract: The analytical solution to the problem of the scattering of SH-wave by isosceles triangular hill near the subsurface cavity in right-angle plane is given by using the idea of match up. Firstly, wave function was constructed by using the methods of complex function, multi-polar coordinate transformation and superposition principle, which satisfied the stress free boundary conditions at the free surfaces for the right-angle plane possessing a circular cavity. Secondly, transform the wave field from the right-angle plane to the half space by using the method of mirror image in order to obtain the total wave filed, which satisfied the boundary conditions. Finally, based on the conditions of the displacement continuity and stress continuity at the “common border” and the stress free condition at the subsurface cavity edge, a series of infinite algebraic equations were given and solved by truncation. Meanwhile, some examples and results are given and discussed.

Abstract: Self-stressing concrete is sort of expansive concrete with high expansion energy which can induce prestresses with restriction in concrete, and steel fibers also enhance tensile strength of concrete. The combination of these two high performance concrete can be used to improve the cracking resistance of concrete significantly. However, like mechanical prestressed concrete, a stable long-term prestresses (self-stresses) level is a key to exploit the particular advantage of steel fiber reinforced self-stressing concrete. Self-stresses are created by restricting the expansion of self-stressing concrete with steel bars or/and steel fibers, therefore, in this paper a series of tests on long-term expansive deformation of concrete were carried out by means of measuring restrict expansive deformation of self-stressing concrete with restriction of steel fibers. The results of tests showed, based on the three-year recording, that the expansive deformation of steel fiber reinforced self-stressing concrete almost kept the same as that of 28-day without remarkable rebound which indicated that losses of self-stresses were not significant and can meet the design requirements on self-stresses level. In addition, it is proposed on the relationship between restrict expansive deformation and reinforcement ratio of steel rebars under different steel fiber volume fraction from 0-2%.

Abstract: The three-dimensional (3D) finite element model of shape memory alloy (SMA) joint system under a clamped-clamped support was established. Using the coupled thermal-mechanical transient state analysis, stress distributions of models under the different loads (internal pressure, temperature) were investigated. And the temperature field, thermal strain field, stress and creep of the joint system were obtained. The results show, 1) for the non-coat SMA joint system, the interface in middle region of the joint’s internal wall is the dangerous region. In this region, the joint’s adhesion failures easily occur and the crack easily initiate. The joint’s coat can improve the fatigue life of joint system. 2) There are higher levels of radial temperature gradient, temperature strain and temperature stress between the internal and external walls of the joint. The creep strain in the internal-external walls of the joint is the main reason for adhesion failure in middle interfaces between the joint and the pipe.

Abstract: This work presents a study of a fatigue test and a finite element analysis on an arch bridge stainless steel suspender with threaded connections. A suspender which had a diameter of 70mm was tested under axial tensile loads range from 430kN to 700kN. The suspender was sudden failure from the thread root of the first loaded tooth in the pin after 1546609 cycles. Then, a two-dimensional axisymmetric modeling ignoring the helix angle of the thread was established with finite element software ANSYS to perform a stress analysis of the threaded connection. The stress concentration factors (SCFs) at the root of the teeth of pin were investigated under the applied external loading. The conclusive results had been drawn from the analysis including the location and the value of maximum SCF in the pin. Finally, the location and the value of the maximum von Mises stress were given. The results showed that the location of the fracture surface was consistent with the location of the maximum von Mises stress.

Abstract: The most common deterioration cause of concrete structures over the world is chloride ions attacks. Thus, service life modeling of concrete is a crucial issue in civil engineering society. Many studies on the topic have been accomplished, however, it is not easy to review literatures about environmental analysis, in particular micro-climatic condition of concrete under chloride laden environment. Since the durability of concrete depends on the properties of the surface concrete, micro-climatic condition which influences on surface concrete realistically should be considered. This study is devoted to analysis the micro-climatic condition of concrete structures, based on the in-situ monitoring of weather in marine environment. The outcome will be combined with modules of material parameters such as chloride diffusivity, surface chloride content, and so on. It is expected that the result of this work should be available for the prediction of chloride profile of marine concrete at atmospheric zone or tidal zone.

Abstract: Based on the stress characteristics of freeze shinking shaft lining at construction and operation stages, it is set up that The anisotropic damage model including initial damage, which suit to make Damage and Fracture Mechanics analysis for the shaft lining. A 3 dimensional anisotropic damage program is compiled using FEPG software, which take the following factors into consideration: temperature, conduction conditions, concrete facture energy and its aggregate gradation. Take the liangbosi mine shaft lining for example, its damage evolutionary process under complicated stresses such as permanence field stress, the gravity and vertical additional stress changed with time is obtained. It is discussed that the facture’s position and its development process, and the mechanical mechanics of the shaft lining structure failure.

Abstract: In this research, the non-linear ultrasonic and acoustic emission techniques were used to evaluating damages induced in concrete under compression loading. Cubic concrete specimens were produced with three different w/c. The nonlinear ultrasonic evaluation was based upon measuring the change in fundamental amplitude with increasing damage and output power level. In acoustic emission testing technique 4 sensors were used to record the AE events under various loading and unloading cycles. An increase in AE hits was observed with increasing damage. Since concrete contains microcracks even under initial loading stages, none of the test specimens exhibited clear signs of the occurrence of Kaiser Effect. Normalized values of Felicity Ratio were plotted and compared with the nonlinear ultrasonic test data. A correlation between acoustic emission and nonlinear ultrasonic techniques in assessing damage growth in concrete was investigated.