Applied Mechanics and Materials Vol. 147

Abstract: Like all other civil engineering structures, suspension bridge is subjected to long-term formidable environment, such as fatigue and corrosion. After its open to traffic, degradation and damage of its components appear in suspension bridges, which cause the reduction of bearing capacity and reliability of suspension bridges. Therefore, the service safety of suspension bridges is a topic of importance, particularly for its managers. This paper provides maintenance strategies for managing and maintaining the structural safety of suspension bridge in a life cycle framework in order to rationalize maintenance actions, economically.

Abstract: Due to its outstanding aerodynamic shape and light weight, the trapezoidal cross-section flat steel box girder with orthotropic decks and thin-walled longitudinal stiffeners of trapezoidal cross section are widely used in long-span suspension bridges in the world. However, because of the geometrical characteristics and the relative flexibility of their components, these structures may be quite susceptible to traffic loadings that fatigue cracks tend to appear in these structures. In this paper, Jiangyin Bridge is used as a case study to investigate the fatigue performance of the steel girders of suspension bridge Jiangyin Bridge is the second longest bridge in China, which has the main span of 1385m. The stress analysis of steel box girders is firstly carried out based on the analysis of fatigue life. Fatigue assessment method is proposed on the basis of in-situ measurement data combined with finite element analysis. A complete fatigue assessment is made in this paper. Key words: flat steel box girder; orthotropic decks; finite element analysis; fatigue assessment

Abstract: Two methods are proposed to study the temperature change influence on strands tensile force in anchor-span suspension bridge, and each force in side-span. The one is based on the relational expression between temperature change and strands force variation; and the other is based on calculation program. Then, take Zhujiang Huangpu Bridge for example. The result shows that: the results of two methods approximate to each other; when the splay saddles are fixed, temperature change generates larger influence of the tensions in anchor span, than the tensions in side-span. The temperature influence coefficient in anchor span reach to -6~-7 kN/°C,while in side-span are -1 kN/°C or so. When the temperature changes exceed ideal temperature range, the force difference between side-span and anchor span will go beyond its maximal friction, so when in construction, measures should be taken to avoid strands sliding. By comparison, when the splay saddles are free, the influence coefficient is much smaller.

Abstract: The charge weight, charge placement (in profile) and depth of charges are important factors in design of Explosive Compaction for saturated loose sand. Six laboratory tests have been conducted to investigate the potential of charge weight, charge placement (in profile) and depth of charge in blast densification, Concentrated Charge has adopted in two of them, the others are Decked or Tiered Charges. Variation of cone penetration tests and ground profile changes were measured. The results of laboratory tests prove the decked and tiered charges are more effective for ground treatment in explosive compaction, more specifically, the more uniform distribution of energy input, the more effective for ground treatment. However, the effective limits of these relationships have not been well defined in qualitative guidance.

Abstract: It is necessary to find a more economical soil improvement technique to densification the reclamation by bumping filling foundation. As a soil improvement technique, blasting-densification of sand is a viable and efficient method, which offers several advantages compared to other soil densification methods. Although Explosive Compaction (EC) has been used effectively for compaction loose, non-cohesive soils for more than 70 years, it has not attained widespread acceptance in China. In-situ trials of Explosive Compaction were carried out to determining appropriate and feasible of Explosive Compaction for improvement sand foundation.

Abstract: For programming and management of water resources, access to hydrometric data is necessary. Unfortunately, the quantity and quality of hydrometric data are not suitable in developing countries. These data can not show drought periods and wet periods correctly. Prediction of wet periods is an important problem for flood control while forecasting of drought periods is very vital for water supply in critical conditions. In this research, two hydrometric stations on the Karun River were considered (Ahvaz and Mola Sany hydrometric stations). The data of Ahvaz hydrometric stations are more exact than of their Mola Sany hydrometric stations. For generation of synthetic hydrometric data in Mola Sany hydrometric station, two methods were applied: 1- Generation of yearly hydrometric data by yearly Markov chain method and monthly hydrometric data by monthly Markov chain method in Mola Sany hydrometric station 2- Generation of yearly and monthly hydrometric data by multi spatial Markov chain method and generated yearly and monthly hydrometric data by yearly and monthly Markov chain method in Ahvaz hydrometric station By comparison results of two methods, it is observed that multi spatial Markov chain method can produce data of wet and drought periods better than yearly and monthly Markov chain method while the results of yearly and monthly Markov chain method and observed data have more fitness. Two methods can predict the length of time of wet and drought periods exactly too.

Abstract: For supplying of water demands in the downstream of dams, optimization of released water from reservoir of dam is necessary. Released water from reservoir is related to discharge of inflow to reservoir, volume of evaporation from reservoir and storage of reservoir. Water demands are includes of drinkable water and agricultural water demand. If released water from reservoir is less than water demands in a month, this month will be a defeat. After a defeat, reservoir must return to normal condition in order to supply of water demands in next months. For minimize the number of defeats and maximize return ability of reservoir to normal condition, a suitable method must be applied for optimization of volume of released water from reservoir. In this research, two optimum methods (SDP method and GA method) were applied for minimize the number of defeats and maximize return ability of reservoir to normal condition. For this purpose, reservoir of the Dez dam was considered in this research. The Dez dam locates in the south-west of Iran on the Dez River. At the end, it is observed that GA method can minimize the number of defeats and maximize return ability of reservoir to normal condition better than SDP method. But SDP method can minimize damage function better than GA method.

Abstract: In order to keep the river and harbor clear, the dredging activity need to be done continuously which has generated millions of cubic meters of dredged material (DM) every year in China. It is an economical and environment-friendly alternative of DM disposal to convert the dredged material to agricultural soil (CDMTAS) by adding admixture and/or dewatering. However, the corresponding evaluation criteria has not been reported so far to determine whether these treated DM are available for using as agricultural soils or not. 145 groups of data composed of weight and the shoes size of the adult was obtained by surveying in China, and a safety factor was given during the statistical analysis of the foot plantar pressure on the ground of adults, and 50 kPa is recommended for human agriculture activity loading on CDMTAS whose process could be regarded as undrained shear. Moreover, 16 kPa is recommended for the least undrained shear strength of CDMTAS that is required for bearing the human agriculture activity.

Abstract: Lacking of explicit limit state function (LSF) will result large quantities of computational efforts for a FEAM based structural reliability analysis. An improved response surface (RS) method is proposed to analyze the failure probability of foundation pit through combining uniform design (UD) and non-parametric regression (NPR). Deferent levels of design parameters are first delicately selected according to UD and then FEAM is used to analysis corresponding pit response parameters including maximum lateral displacement of wall, settlement of ground, safety factor of overall stability, safety factors of against overturning, heave and piping. The RS relationship is then established through NPR based on inputs and responses. At last, a direct Mont Carlo Simulation is carried out to obtain the probability density function of response parameters.

Abstract: Numerical simulations were carried out to investigate the current situation of underground water and its variations rule resulting from site grading at a proposed iron and steel base in Xichang. The comparison shows that the numerical simulations results of underground water level tally with measured results very well. On the basis of the simulation analysis result of current situation of the underground water, its variations rule after site grading was simulated and forecasted. The results show that after site grading, due to recharge, discharge and runoff conditions of underground water have be changed, the underground water level at the dig, fill section and the edge of the site would also be changed too. Specifically, the underground water level of dig section lowers than that before site grading while fill section’s higher than before.