Durability design of prestressed concrete structures

Based on the durability characteristics of prestressed concrete structures,the durability limit states of carbonation and chloride ion attack are defined, respectively.Durability predicting models on the basis of reliability mathematics and stochastic processes areconstructed, and the pure theoretical formulae of failure probability of prestressed concretestructures are analyzed. In addition, a simple durability design method for carbonation ofstructures is put forward. According to the analysis, the durability of prestressed concretestructures is superior to that of traditional structures. The research also indicates that theconcrete cover prescribed in the current code (GB 50010-2002) is not adequate. The rational coverthickness should notbe less than 35 or 45 mm according to carbonation or chloride ion attack,respectively.

Probabilistic Assessment of Pitting Corrosion Effect on Flexural Strength of Partial Prestressed Concrete Structures in a Chloride Environment

Like reinforced concrete （RC） structure, Prestressed concrete （PC） structures cannot escape from corrosion related problems, especially when they are subjected to very aggressive environment, such as chloride environment. The corrosion of PC and RC structures can take place if the concrete quality is not adequate, the concrete cover is less than that specified in the design, poor detailing during design and construction. For RC structures, corrosion in the reinforcing steel generally leads to serviceability problems （staining, cracking and spalling of concrete）. By contrast, for PC structures, corrosion of prestressing strands may initiate structural collapse due to higher stress levels in the steel and smaller diameter of the prestressing steel. Research on corrosion effect on concrete structure has mainly considered the effect of corrosion have on reinforced and full prestressed concrete structure. In this study, a structural framework will be developed to predict the flexural strength of partial prestressed concrete structures in a chloride environment. The corrosion model previously developed for reinforced and prestressed concrete structures will be combined to predict the effect of corrosion has on partial prestressed concrete structures. Note that in partial prestressed concrete structures, both non prestressing steel （passive） and prestressing （active） reinforcement are utilized to carry the load. The framework developed will be combined with probability analysis to take into account the variability of parameters influencing the corrosion process. This approach allows more accurate prediction of service life of partial prestressed concrete structures in a chloride environment.

Design and research of gymnasium structure in Zhejiang University

This paper deals with the issues involved during the design of a complex gymnasium located at the new campus of Zhejiang University. The complexity comes from the gymnasium’s being of three parts: long-span membrane structure, prestressed concrete structure and extraordinarily long tubular steel structure without seams. The paper first presents considera- tions of the prestress design, followed by analyses of the stress states due to temperature changes and concrete shrinkage. Buckling and postbuckling analyses were performed to determine the load-carrying capacity of the perfect and imperfect tubular steel structure of the inclined arch system, while dynamic relaxation method and general nonlinear finite element analysis were used to carry out shape-finding and stress analyses of the membrane structure respectively. Finally, collated monitoring date was applied to control the construction quality and verify the design parameters. Some useful conclusions are available at the end of the paper.

A transient fiuid–structure interaction analysis strategy and validation of a pressurized reactor with regard to loss-ofcoolant accidents

A loss-of-coolant accident(LOCA)is one of the basic design considerations for nuclear reactor safety analysis.A LOCA induces propagation of a depressurization wave in the coolant,exerting hydrodynamic forces on structures viafiuid–structure interaction(FSI).The analysis of hydrodynamic forces on the core structures during a LOCA process is indispensable.We describe the implementation of a numerical strategy for prestressed structures.It consists of an initialization and a restarted transient analysis process,all implemented via the ANSYS Workbench by system coupling of ANSYS and Fluent.Our strategy is validated by making extensive comparisons of the pressures,displacements,and strains on various locations between the simulation and reported measurements.The approach is appealing for dynamic analysis of other prestressed structures,owing to the good popularity and acknowledgement of ANSYS and Fluent in both academia and industry.

Seismic Performances of Large-Span Prestressed Concrete Frame Structure by Shaking Table Tests

The seismic performances of the large-span prestressed concrete frame structure of bunker bay of thermal power plant under different intensity level was investigated by shaking table tests.A 1/8 microconcrete nonfull weight scaled model was designed according to the prototype structure and the conditions of laboratory.Three kinds of scaled ground motion accelerations were employed as seismic excitations.White noise was input in the structure through each seismic wave applied.The experimental results indicate that the structure is safe to endure seven degree intensity as required in Chinese codes.The natural vibration frequency of the structure is decreasing with the increasing of the seismic intensity,the natural vibration frequency of the structure decreases by about 24.5%,and the structural stiffness reduces by nearly 44% in seven degree intensity of seldom occurred earthquake.The damage at the top of column in the first floor is the most serious,the weak part of the structure is at the first floor,and the strong beam/weak column phenomenon appeared obviously,so this kind of large-span prestressed concrete frame should not be used in a high intensity district.