Applied Mechanics and Materials Vols. 94-96

Abstract: Reinforced concrete structures are prone to damage during their service lifetime caused by factors such as the effect of overload, ground motions, and other actions. Undetected damage may lead to structural failures. Early detection of damage and timely repairs can prevent catastrophic failure and ensure regular service of structures. As a result, a so-called delimitation wavelet-transform search method, based on the characteristic of multi-resolution of wavelet transform, is presented in this paper for on-line damage identification of reinforced concrete structures. One possible advantage of this method is that the damage temporal and spatial location can be detected rapidly and efficiently. Further research is carried out with numerical simulation of a structure test model to study the storied damage detection and localization of reinforced concrete frame structures under seismic actions. The analyzing result is compared with that observed in a simulated earthquake vibration stand test. Good agreement is obtained and it verifies the effectiveness and validity of the method proposed in this paper.

Abstract: The study is about submarine pipeline. Considering the impact of different axial force, The reduced velocity is introduced as the pipeline vibration effect of vortex trail releasing. The vibration parameters of the span pipeline are analyzed and vibration control formula is built. The natural span length of the submarine pipeline is calculated according to the DNV-OS-F101 rule. The natural frequency of the span pipeline and the allowable span length are solved. The case study of submarine pipeline in Chengdao oil field is made and the variation law of natural frequency of span pipeline is got. The stream reduced velocity decreases as the axial force increase. The theory analysis of the vortex induced vibration can provide the scientific basis for the safety design of offshore submarine pipeline.

Abstract: This paper focus on the application study of HPC, and both of HPC and normal concrete (NC) were adopted for comparison in the Yu-Cheng Bridge Durability tests were carried out on HPC and NC respectively, based on the comparative analysis of the results obtained from these tests, durability evaluation of HPC is made. The results are useful for the evaluation of durability of HPC.

Abstract: The deep drill string is subjected to many kinds of loading under the condition of vibration and precession, such as tension, compression, bending and torsion, while the temperature and press are very high. Under this circumstance, the shallow drill string is more likely to failure. Based on the force analysis of the drill string, the drilling process of the deep drill string is simulated using finite element software. The stress distribution and displacement of the drill string is obtained under the interaction of drilling pressure, torque and temperature. At the same time, the effect of transverse vibration, longitudinal vibration and torsional vibration, on the stress and displacement of the drill string, is compared. The change law of the natural frequency of transverse vibration varying with the length of drill string, rotational speed and the hole size is discussed. Connected with concrete examples, the reliability and sensitivity of some influencing factors such as external diameter, wall thickness, the minimum yield strength, temperature, elastic modulus, Poisson’s ratio, axial loading and torque is obtained. The main factors that influence the reliability of the drill string are the yield strength and torque. The reliability of the drill string increases as the increase of yield strength, and decreases as the increase of the torque.

Abstract: Reinforced concrete (RC) structures are widely used in civil engineering for their merits. A good-quality concrete provides a highly alkaline environment that forms a passive film on reinforcement surface, preventing steel bars from corroding. Due to chloride attack or concrete carbonization, corrosion of embedded reinforcement in concrete members is common for RC structures. Much importance should be attached to the fatigue of corroded concrete bridges because they bear not only static loads but also alternate loads. Followed along with the aging of bridge structures, the increase of traffic volumes, the augment of vehicle loads as well as the deterioration of service environment, many corroded concrete bridges are urgently needed security appraisal and residual fatigue life forecast. Fatigue of corroded RC beams is a key problem for the existing corrosion-damaged concrete bridges. But the interrelated research was little. Based on the most new study information, the production on fatigue of corroded concrete beams was listed and analyzed, and the problems on fatigue of corroded concrete beams were indicated.

Abstract: Local thinning of submarine pipeline always exists due to the complexity and dynamic of marine environment loads. However, the location and extent of thinning areas are random. Mechanical research on the randomness of local thinning of submarine pipelines is significant for pipeline’s stress analysis and failure evaluation. In this paper, finite element model of locally thinned submarine pipeline is established and based on the Monte-Carlo method, the effect of input random variables on the submarine pipeline’s reliability is analyzed. Probability distribution ranges of equivalent stresses are got and further, relationship equation between confidence level and stress limit has been obtained. The result more accurately reveals the relationships of locally thinned pipeline and its elastic modulus with equivalent stress, which can provide foundation for safety analysis of locally thinned submarine pipeline with internal pressure.

Abstract: In this paper, high-performance concrete (HPC) incorporated organic fibers, i.e., polyvinyl alcohol fiber (PVA fiber), polypropylene fiber (PP fiber), cellulose fiber (UF fiber), polyethylene fiber (PETF) was produced. The properties measured included strength, crack resistance performance and water permeation of the concrete. The effect of organic fibers on the shrinkage and water permeation properties was investigated. Test results indicated that the organic fibers of different types could reduce the size and amount of crack source; organic fibers provided better enhancement for shrinkage resistance and impermeability of HPC; the improvement of the shrinkage resistance and the impermeability of the concrete resulted from the use of organic fiber, which was dependent on the types, total volume fraction and of fibers, proportions of organic fiber.

Abstract: The life of the hydraulic pump is affected by many factors. According to the statistical information of failure of the main hydraulic pump of an aircraft, we apply the reliability engineering theory to calculate and analyze its service life. As known in calculation, the service life of hydraulic pump conforms to Weibull distribution, and there is no the useful life period. The basic reasons resulting in the decline in the service life of the pump are the higher work pressure, the poor work condition and serious hydraulic system pollution. Furthermore, several measures for use and maintenance are given.

Abstract: A triangular web profile (T_RIWP) steel section is a built-up section made up of two flanges connected to a web plate of triangular profile. This paper describes the study on the bending performance in major (I_x) and minor (I_y) axes of Triangular Web Profile (T_RIWP) compared to flat web (FW) steel sections. A number of finite element models were developed using finite element software LUSAS version 14.3. Thin shell element which is a family of shell element in 3D dimension was chosen to represent the element type of the model. Two sizes of FW as control specimens and two sizes of T_RIWP steel section which is 200×100×6×3 mm and 180×75×5×2 mm were used. Each of steel section was modeled using several spans such as 3m, 4m and 4.8m. The finite element results show that the deflections in major axes for TRIWP more than FW steel section. It was noted that, the value of I_x for the T_RIWP is 0.754 to 1.523 times the Ix of FW steel section. On the other hand, the deflections in minor axes for T_RIWP lower than FW steel section. The value of I_y for the T_RIWP is 1.818 to 1.686 times the I_y of FW steel section. It can be concluded that the T_RIWP is stiffer compared to FW steel section in minor axes and T_RIWP has a higher resistance to bending in minor axes than FW steel section.

Abstract: Based on the test and numerical analysis, the paper studied the constructional reinforcement of blast furnace foundation under the influence of concrete hydration and top temperature. The results indicate that constructional reinforcement should be thinner and have a small spacing. Stress concentration always appears around the corner and constraints of blast furnace foundation, where should be strengthened with constructional reinforcements. In order to prevent cracks caused by internal tensile stress during concrete hardening, it is necessary to place temperature reinforcement inside the foundation. Temperature effect should be considered at the circular area on top of blast furnace foundation and should be strengthened with constructional reinforcements.