A multi-factor diffusion model of chloride in concrete was formulated, in which the hypothesis of Fick’s Law were corrected through parameter definition. The values of the parameters in the model were given for practical applications according to pilot calculation and analysis of mass data. By using this diffusion model, three calculation methods of concrete structure service life were further deduced, it includes definite value method, probability performance based method and time-dependent reliability based method. The service life prediction for the approach bridge of Huang-pu Bridge was carried on by using various prediction approaches mentioned above. The results showed that: time-dependent reliability based method can consider randomness of chloride diffusion coefficient and the depth of concrete covering layer, and the stochastic characteristic of environment variable can be easily taken into account too. By adjusting the target reliability, the prediction results are consistent with those of the other two methods.

During the service process of a P.C. bridge, the mechanical properties of materials (including concrete and steel) will deteriorate, and eventually result in the decrease of ultimate bearing capacity. Considering it’s structural behavior, degenerate solid elements were used to set up a three-dimensional model. By taking prestressed reinforcement as a part of structure, the equivalent nodal load was provided to calculate the effect of tensioning bars. The T.L. method was adopted to consider the geometric nonlinear effect. The Ohtani & Chen model was used to simulate the concrete material nonlinear behavior, and for prestressed steel strand and common reinforced, linear hardening and ideal elastoplastic model were adopted respectively. A P.C. continuous rigid frame bridge was employed for the case study, on the basis of material performance deterioration, the ultimate bearing capacity analysis of P.C. bridge structure was carried out. The results show that material deterioration has great impact on ultimate load capacity of structure: the load factor on limit state dropped rapidly from 13.9085 at t=0a to 7.8265 at t=100a, the corresponding safe index decreased from 2.265 to 1.581, and brittle characteristics was aggravated at the same time.

The slurry pump is one of the most important pieces of equipment in mineral transportation and separation systems, and it has complex two-phase flow characteristics and wear mechanisms. By employing numerical and experimental methods, the solid–liquid two-phase flow characteristics and wear patterns were investigated in this study. A two-way coupling discrete phase model (DPM) method was used to predict the flow pattern and the wear location and shows good agreement with the experimental observations. The pump performance characteristics of numerical results under pure water conditions were consistent with the experimental results. The effects of particle parameters and operating conditions on the internal flow field and wear were compared and discussed. The results show that the wear degree increased with the increase in volume flow rate and solid volume fraction. With the increase in particle size, the wear range at the impeller inlet became significantly smaller, but the wear degree became obviously larger. This study provides a basis for reducing the wear and improving the hydraulic performance of slurry pumps.

The deficiency of bond capacity of traditional cement mortar was exposed as the new wall materials were used widely. The polyvinyl-butyral(PVB) and methyl cellulose(MC) were chosen as chemical additives to amend the property of normal mortar, the orthogonal tests of 96 pieces of shear specimens were carried out, and the orthogonal analysis of test results was performed. The results indicated that the sort of wall material was the most important factor in bond capacity of mortar, the mixed quantity of polymer and mortar strength follows, and there was a remarkable increase in mortar bond strength when the mixed quantity of PVB and MC was 20%~30% and 0.05%~0.1% respectively.

A grey relative degree assessment model for durability of concrete structure, based on the combinatorial weight, in which expert experience & information entropy are taken into account, is established after analyzing problems in existing durability assessment theory. Both the influence of subjective factors and the significance of objective factors are considered in this model, and to avoid assessment deviation for emphasizing one side or another. The model, which is testified by practical engineering example, provides a new approach to make durability assessment more scientifically and exactly.