When Levy type rigid bracing dome is impacted by unexpected load, its structure may collapse continuously, resulting in property loss and casualties, therefore, it is necessary to analyze its progressive collapse performance. According to characteristics of rigid bracing dome, the threshold coefficients of members and its calculation formula were given, and the discriminant criteria and types of progressive collapse were proposed. Damage coefficient based on response difference was proposed, and importance coefficient of members was given. Member importance of levy type rigid bracing dome were analyzed and sorted based on importance coefficient of members. Based on the discriminant criteria of progressive collapse and the results of importance analysis of members, the method and process of progressive collapse analysis were proposed. Progressive collapse performance of structure was analyzed. The influence of both rise span ratio and initial prestress on the progressive collapse performance was discussed. The method of progressive collapse resistance against rigid bracing dome was proposed. The research showed that the progressive collapse types of levy type rigid bracing dome could be divided into non collapse, local collapse and overall collapse. The outer ring bar obtains the largest importance coefficient, followed by the inner ring bar. The smaller rise span ratio is or the larger the initial prestress, the smaller importance of the member will be. When the outer ring member, inner ring member or node is damaged, the structure will collapse continuously, while other members will not collapse. Strengthening the joints and ring members can improve resistance of structure against progressive collapse..
In order to study the interlaminar mechanical behavior of regenerated composite pipes with thin-walled lining, tangential and normal tensile failure tests are carried out on the composite pipes with corroded defects and thin-walled stainless steel lining. Based on the test results, a finite element analysis model is established for the repaired pipes with corroded defects. The test results of test specimen under the effect of tangential force show that with the increase of pipe steel corrosion extent with corrosion defects, bonding layer and the base pipe steel strip gradually decreases, the ultimate strength of the interface between the layers increase gradually, and with the increase of the corrosion loss rates, the interface cohesive force has a slight increase. But with the increase of proportion of binding material failure, this increased trend gradually flatten out. The tangential failure of interlayer interface is mainly due to the failure of cohesive force of binder. The test results under normal force show that the failure modes of each specimen are basically the same, and the failure is mainly the failure of cohesive force of the bonding layer. A bilinear constitutive model of tangential stress and relative displacement at interlayer interface of composite pipes is established by difference method. The relation between normal stress and relative displacement at interlayer interface can also be simplified to bilinear constitutive relation. The finite element analysis model is used to analyze the specimen, and the analysis results are in good agreement with the test results. The bilinear interfacial cohesive force model can accurately simulate the interlaminar mechanical properties of thin-walled composite pipes in the finite element model analysis. The research content and results can provide a theoretical basis for the trenchless continuous lining repair technology of buried pipeline..
Progressive cavity pumps (PCP), which uses the ordinary nitrile rubber, are widely used in heavy oil production, and it is prone to failure of the core-burning perforation of the stator bushing. The expensive hydrogenated nitrile rubber is resistant to high temperatures but does not have precise use depth and cross-sectional parameters. In order to solve above problems, first of all, the rubber hyperplastic constitutive model of ordinary nitrile rubber and hydrogenated nitrile rubber is fitted based on the thermal aging and tensile tests. And then, a new finite element model is established based on the one-way decoupling method to decompose the delayed heat generation phenomenon. Finally, the influences of working well depth, interference, and wall thickness on the lagging heat generation are studied, and the orthogonal table of the three factors is listed. The research results show that ordinary nitrile rubber is better than hydrogenated nitrile in working temperature below 70 ℃ (corresponding to the working depth of 1 667 m), but it will suffer serious aging in the deep working temperature or the high temperature environment, which is the main reason for core burn and perforation failure in current applications. Hydrogenated nitrile rubber begins to age at a working temperature of 150 ℃ (corresponding to the working depth of 4 333 m), which is more stable than ordinary nitrile in mechanical properties, so it is reliable. Due to liquid column pressure and rubber aging, the maximum stress between the bushing and the rotor is decreases first and then increases with the increase of working depth. With the increase of the interference, the sealing performance of the PCP improves, and the maximum temperature of the sleeve section increases exponentially. For every 2 mm increase in the thickness of the rubber bushing, the true displacement of the inner wall increases by 0.059～0.067 mm on average, corresponding to the growth rate of 19%～28%. It is concluded that the working depth of 1 667 m is the boundary between the two types of rubber PCP. The interference is the minimum value of 0.5 mm, and the maximum wall thickness is 12 mm under the condition of no leakage. The research results provide theoretical support for reasonably matching the parameters of the stator rubber bushing, which optimizing the stator rubber material, and improving the working performance of the PCP throughout the life cycle..
Submerged dam is a commonly used structure to control the reaches of a braided river, and it is generally located at the entrance of the inlet. The flows in these areas are often complex. It may cause downstream scouring after the completion of the submerged dam and the consequent uneven subsidence. Riprap reinforcement is an important measure of maintaining the function of the submerged dam. The conventional riprap reinforcement project is used in the bank protection. The traditional stone-throwing distance formulas are generally applied to shallow water and related to the water surface velocity, water depth, and the weight of the stones. There is not much study on the riprap reinforcement project in deep water area, and the research on the stone scattering is much less. In this paper, the authors make the first attempt to conduct-field tests for investigating the throwing distance and the enlargement coefficient, and for optimizing the comprehensive scattering coefficient. These field tests were performed at the entrance of the left branch of Hechang-bar, which is located at the lower reach of the Yangtze River, China. Based on the vertical distribution of velocity, the formula of the fall velocity of stone in deep water area, the formula of the throwing distance and the formula of the comprehensive discrete coefficient are derived. These formulas are verified by field data. The research extends the traditional throwing distance formula to the deep water area, and discusses the dispersion degree of throwing stones. The results can provide reference for submerged dam reinforcement works or other similar construction projects..