Advanced Materials Research Vols. 368-373

Abstract: A wireless remote monitoring sensor network for durability of large concrete structures is designed and studied in the case that traditional parameters monitoring and durability evaluation methods are willing to promote to meet modern requirements. As traditional monitoring methods of concrete structure focus on the structural parameters while missed the research on durability of the structures, a Internet of Things (IOT) system of durability monitoring is designed to optimize and develop. By deploy sensor nodes for durability monitoring system based on ZigBee wireless network and GPRS remote data transmission, the durability sensor data collected can be send to the monitoring and evaluation computer information system based on data fusion to finish intelligent analysis, evaluation and early warning. In this way, the system conquered the problems that high maintenance cost, early deterioration of structural performance and shorten useful life, contributed to the structural safety of large-scale concrete works and take action to maintain normal operations in time. This meets the requirements of China's economic sustainable development, so it has important social significance and economic values.

Abstract: Bridges are the key components of civil infrastructure. Since decades ago, bridge strengthening and rehabilitation have become popular and their wider applications would be needed in the future. Although much research was carried in this field, some important problems including bearing capacity of reinforced beams didn’t form concordant views in this community. To research influence on bearing capacity of reinforced RC beams, we analyzed the loading process of RC reinforced beams from the beam-loaded-only stage to that of co-working of compound beams (including original beams and their strengthening layers), developed non-linear FEM program to simulate that loading progress, and finally validated the results with data from reference. This paper presents the theoretical analysis, and compares data yielded by program with those of experiment. We found that for adequate reinforcement beam the influence of secondary loading on the ultimate bearing capacity of reinforced beams is very limited. Our finding was confirmed by the experiment and FEM program.

Abstract: The total chloride concentrations of concrete with 0.51 of water to cementitous from three contents of Fly ash, GGBS, two kinds of corrosion solution for one dimensional diffusion at different diffusion depth and time were measured by chemical titration. The influence of Fly ash and GGBS content on total chloride concentration and the surface chloride concentration were analyzed. The expressions of the surface chloride concentration were discussed in terms of the experimental results related with content of Fly ash, GGBS and solution. The numerical analysis results indicated that the expression of the surface chloride concentration has a significant impact on the long-term service life of concrete in chloride environments.

Abstract: This paper studies on deducing the analytic formulae on Gauss coordinates displacement before or after the increase of major radius of ellipsoid expanded modals, which is based on the partial derivatives of geodetic coordinates in Gauss coordinates deducing from direct solution formulae of the Gauss projection coordinates in conjunction with differential coefficient formulae and variable of geodetic coordinates. On this theoretical foundation, analyzing the relationships between Gauss coordinates displacement and other mathematical parameter . The relationship of graphics between point displacement components of latitudinal coordinate dy and longitudes is similar to the straight lines. The relationship of graphics between point displacement components of longitudinal coordinate dx and latitudinal coordinate dy, and the geodetic height is similar to the straight lines.

Abstract: Engineering projects often face risks from technology, economy, nature, social and other aspects. Risk factors are of interdependence and interaction, so they are very difficult to be quantified. The paper describes a risk evaluation method for engineering projects based on fuzzy set theory which uses respective fuzzy numbers to evaluate the factors. The primary weights of factors and evaluation of alternatives are determined by applying fuzzy numbers. The results are consistent with the results calculated by conventional risk evaluation method. The research demonstrates that the method is objective and accurate, and is of an application value in the risk evaluation for engineering projects.

Abstract: Two aqueducts in 620m length were built 38 years ago. The flumes were U-shape and thin-wall structure in 10m span, which were simply supported on the reinforced concrete frames arranged in a row. After operated for 30 years, they were abandoned. Until 2009, with the increment of water supply of urban residents and landscapes of Zhengzhou city, they were considered to be reused. Therefore, the visual inspection on water-stops, seepage-proofing coating and concrete cracks of flume, the damages of supporting seats and reinforced concrete frames were conducted. The nondestructive testing for strength and carbonation of concrete, concrete cover and erosion of reinforcement were carried out. Based on the detected results, the serviceability and ultimate resistance of the aqueducts were evaluated in accordance with current Chinese design code. The measures were brought forward to strengthen their structures and repair their damages. The main results of these works are introduced in this paper, which can be used as reference for repairing the similar hydraulic concrete structures.

Abstract: In this paper, a practical application for a continues beam-type bridge, the Truckee river bridge, California, to test the validity of the improved DSC method in the identification of the bridge damage after severe loading such as that caused by an earthquake was discussed. Comparing the calculated stiffness from the improved DSC method with that from design data of the bridge based on the numerical simulation with different damage scenarios in consideration of measurement errors, the location and severity of the damage in the bridge can be accurately and reliably detected. The pushover and seismic damage assessment analysis shows that the improved DSC is valid and efficient for damage detection in highway bridges.

Abstract: To measure the depth of fire-damaged concrete by ultrasonic method, it was traditionally assumed that the concrete of the fire-damaged structural member could be simply classified into damaged layer and undamaged layer. Based on it, the damage depth can be calculated with a series of single-sided ultrasonic measured data. This method is simple and convenient but less accurate in the practical application. To improve the algorithm, hyperbola curves are adopted to simulate the varying of damage with depth in this paper. And parabolic curves are adopted to simulate the traces of ultrasonic wave in different measured distances. Therefore, the minimum propagation time can be obtained under different damage conditions. Through comparing the calculating results and measured data in different measured distances, the most likely damaged trend can be determined with least square method. At the end of this paper, examples are demonstrated to prove this algorithm feasible and more accurate than the traditional one.

Abstract: Steel stranded wire mesh and polymer mortar (SMPM) is a novel technique recently developed for structural strengthening. To investigate the feasibility of strengthening reinforced concrete (RC) bridge box-girders with SMPM, bending tests on three scaled RC box-girders were made, based on which formulas for predicting the bending and debonding capacities of the strengthened RC box-girders are proposed. First, the box section is represented by the T section using the effective width factor in the elastoplastic stage. Then, based on the equivalent height of compressive region, bending failure modes of the strengthened girders are classified, and equations regarding the ultimate bending capacity corresponding to each failure mode are established respectively. To account for the debonding failure observed in the tests, a shear-capacity-based model is proposed. Comparison was made between the analytical and existing test results.

Abstract: Distributed optical fiber temperature sensor (DTS) system is used in leakage detection and safety monitoring of dam by measuring temperature. Problems and solutions of using DTS system in dam are researched. Two typical engineering applications in the Three Gorges dam and Xin'anjiang hydropower station are studied. New methods are put forward and test results are listed in the end.