Applied Mechanics and Materials Vols. 501-504

Abstract: In this study, a scheme integrated with deterministic stochastic subspace system identification and the method of damage localization vector (DLV) is proposed for damage detection of structures based on seismic response data. A series of shaking table tests has been conducted in National Center for Research on Earthquake Engineering (NCREE), Taiwan. Damage condition is simulated by reducing the cross-sectional area of some of the columns at the bottom ends. Both single and multiple damage conditions at various locations have been considered. Full or partial observation conditions have been taken into account in the system identification analysis. It has been shown that local damages (stories) can be identified from global responses of the structure to earthquakes if sufficiently observed.

Abstract: Using field experiments, the vibration effects of historic tower induced by planed railway line are estimated. The vibrations include the construction vibration and the traffic-induced vibration. The results show that the blasting construction leads to the significant increase in vertical velocity and acceleration. There is no difference between the background vibration of field and foundation of tower. Different types of the sites soil around the tower cause little change. Each measurement time showed an upward trend of vibration level with the increase of frequency. The closer the tower is to the vibration source, the larger the structural vibrations would be. The dominant frequency range for highway-induced vibration is 10-20Hz. For train-induced vibration, the dominant frequency range is more than 40Hz. Surface waves will result in amplification phenomenon of vibration velocity of ancient structures within a certain range.

Abstract: At the Faculty of Civil Engineering VSB TU Ostrava testing device was constructed so that the phenomena of soil foundation interaction could be experimentally investigated and compared with numerical models. Results of experimental loading test are compared with soil foundation interaction analysis based on finite element method (FEM). The stress strain analysis of elastic halfspace by means of Gauss numerical integration and Jacobean of transformation is presented here. The arbitrary shape and general course of the loaded area in nodal points is allowed by use of 4-and 8-node isoparametric elements, numerical integration and Jacobean transformation. The objective of this paper is also improving and developing the soil-structure interaction analysis based on the experimental results and FEM.

Abstract: The combining Part Of new-old concrete is a weak link. The cohesive strength of the combining layer is generally lower than the strength of the concrete poured completely. It will greatly affect the reliability of structure, when the combining layer is bad. It is a effective method to Inspect combining surface conditions by ultrasonic method. But related specification for defect judgment method of ultrasonic method, which is not fit to detect the defect area is larger in detect area, the overall quality of members is poor, make the discreteness of data less, those causes low judgment value, and the defects to leakage. In addition, the less data is not easy to found out the outliers. We adopted ultrasonic angle measurement method for concrete jointing surface of 50 pillars testing analysis, Method to determine the critical value of defect of abnormal value, and studied critical value determination method of defects outliers, propose a method of defects determination base on the common probability method. As detection is shown, first, with this method detect the joint surface of the concrete columns, contrasted core drilling results, prove the method is effective and feasible. Second, For new pouring concrete quality is poorer near surface, defect points too much, contrasted core drilling results, prove the method is effective and feasible. In addition, using this method for detecting data less, contrasted core drilling results, prove the method is effective and feasible.

Abstract: It is imperative to develop effective techniques to monitor the condition of steel corrosion in reinforced concrete (RC) for ensuring structural serviceability and durability. In the past decade, some physical based techniques have been proposed as alternative tools for monitoring corrosion. These physical based monitoring techniques can conduct accurate condition assessment of steel corrosion through direct measurements on embedded steels. In this paper, some primary physical based monitoring techniques for condition assessment of steel corrosion in reinforced concrete in the recent years are presented and the challenges and future trends in the development of physical based monitoring techniques for condition assessment of corrosion in reinforced concrete are also put forward.

Abstract: Bridge Structural Health Monitoring System mainly monitors vibration and cable force of bridge. Fiber optical sensor is chosen to measure vibration and cable force, and their computing method is also given. Besides, wavelet de-noising and Multi-harmonic extraction technology is used to process data. In order to collect, analyze, display and store data, the system use LabVIEW and SQL Serve platform with multi-thread and multi-protocol technology. System regards the one Wuhan Yangtze River Bridge as real-time monitoring objects, and all the indicators have reached the design requirements.

Abstract: According to optimized fitting analysis for measured data in static load test of 22 different types of single piles, a new modified exponential model was proposed by authors in this paper. In comparison between the hyperbolic model and the integrated exponential curve model, the correlativity coefficients R of the modified exponential model were over 0.996. The fitting effect of the model of proposed in this paper is better than that of other models above-mentioned. The deviations between fitting and measured data in static load test for single pile was small, especially, in the tail pasts of fitting curves, the mean deviations of 2 test pile given in the paper are 1.61% and 1.99% respectively. The modified exponential model can be better described Q-S curves of single piles. It can be used to better evaluate the ultimate bearing capacity of single piles.

Abstract: In this paper, a research is carried on to identify damage of reticulated shell structures based on the combination of modal curvature method and wavelets transform method. Take a scaled model of the reticulated shell structure as an example to analyze, the cross section of one member supposed to have a slight damage of stiffness reduction. In order to locate the damage, modal curvatures of the structure are taken as damage indexes to perform continuous wavelet transform. Results of the numerical analysis indicate that the difference of wavelet transform coefficients of modal curvature can be used to locate damage roughly, while the wavelet transform coefficients of modal curvature difference can be used to locate damage more precisely with easier and more reliable data processing. So it is clear that the damage identification based on modal curvature and wavelet transform is quite effective.

Abstract: Focusing on the Zhengzhou East Railway Station, which is the larges railway staton in China at present and has the characteristics of bridge-station combined structure, the fine finite element model was established by considering the influence of second dead loads. The rational crowd loading models were also determined based on the testing results. The vibration responses of waiting room floor and business floor caused by crowd loading are calculated. The vibration comfort was evaluated by the code of ATC (1999). The calculation and analysis results showed that: (1) the vibration of waiting floor and business floor under crowd get up loading is small, which can satisfy the comfort demand; (2) the vibration of waiting floor and business floor under crowd walk loading is bigger because the frequency of crowd walk loading (2Hz) is closer to the structure first natural frequency, which can satisfy the comfort demand basically and only some individual parts can not satisfy the comfort demand; (3) the vibration caused by crowd loading can not neglected for the large-span flexible structures.

Abstract: This paper presents the result from a study of Galvanostatic Pulse Technique for determining the corrosion rate of steel in reinforced concrete. The investigation to the condition factors and instrument parameter that significantly influence the testing result of the current pulse technique in on-site measurements is made in this paper. Firstly standard specimens which have different thickness of concrete cover and NaCl adding content were prepared, and instruments (CorroMap TM) for field measurement of corrosion rate of steel in reinforced concrete are selected for testing. From the study we can conclude that Icorr increased with the decreasing of the thickness of the concrete cover and the adding content of NaCl to the concrete when casting with non-linear rule, and an anodic pulse of 50 μA with pulse duration of 10 seconds is appropriate for testing both passive and active area of rebar.