Advanced Materials Research Vols. 163-167

Abstract: In order to learn about the dynamic characteristics of the oil storage tank, detect and identify the damaged oil storage tank, based on the basic principle of the experimental modal analysis, the modal test was maken on the vertical dome roof steel oil storage tank model with the hammer method of multi-point input and output on single point, and the identification ability of the modal parameter was studied when the oil storage tank model is damaged. At the same time, we carried out the model's simulation calculation with FEA, considering the effects of the structural physical parameters and the foundation parameters of the oil storage tank. The calculated results of modal test are in accordance with test values, the analysis results provides certain basis for the damage identification and health monitoring work of the oil storage tank structure.

Abstract: The aim of this work is to develop a procedure to follow the evolution of fracture in RC Beams strengthened with CFRP sheets by means of Acoustic Emission signal analysis. In particular the main goal of this experimental work wants to be the definition of a characteristic signal parameter able to represent the evolution of the fracture dimension in the RC Beams during load test. To this end, laboratory tests were carried out at the Non-Destructive Testing Laboratory of the Politecnico di Torino.

Abstract: In this paper, a new approach for damage detection using a chaotic signal as an input excitation and steady state attractor-based measures as diagnostic parameters is investigated by means of numerical simulations. The method utilizes the deterministic, extreme sensitive properties of the chaotic signal to give rise to a low-dimensional response for feature extraction. This approach is applied to two numerical examples, the 4 DOF spring-mass-damper and a cantilevered beam system, where the damage is produced by varying the structural damping and stiffness, respectively. Lyapunov dimension is calculated as a “feature” for detecting the damage. Results show that this approach is feasible to detecting structural damage.

Abstract: This article takes the Xiamen Sea reef engineering as an example to research the structure response of underwater blasting vibration on 4-story masonry-concrete building. The blasting seismic wave has been field monitored and the data has been analyzed with some means such as wavelet analysis. As a result, the characteristic laws of different floors’ structure responses under the effect of blasting vibration load have been acquired. With the floor increasing, the particles vibration velocity amplification coefficient of the forth top roof relative to the ground is approximately 1.36 to 2.086. The duration period and the main vibrationa are reduced respectively by 14%-28% and by 38%-56%; each floor’s vibration energy mostly concentrates in 0-25Hz’s band. The first floor’s energy mainly concentrates on 0-60ms, mainly distributing in 1st and 2nd frequency band, with the maximum appearing in the 1st band. And the vibration signal energy peak amplification coefficient relative to the ground is approximately 1.783 to 3.866.

Abstract: Acoustic emission (AE) is a powerful nondestructive test that can be used to characterize cracking, growth of cracks, and the degree of damage. This technique is clearly distinguished from other nondestructive techniques as it is a nondestructive test that estimates the degree of damage to concrete. In this study, the AE signals emitted during failure, according to the strength of recycled aggregate concrete specimens was examined, in order to characterize them using existing research results and evaluation theories. In addition, it is demonstrated that AE can be utilized to identify crack source and the mechanism of crack growth, which were monitored using a software program developed from the theory of the location of the source of a microcrack.

Abstract: Structural health monitoring (SHM) is an emerging field in civil engineering, offering the potential for continuous and periodic assessment of the safety and integrity of civil infrastructure. In this paper, a distributed computing strategy for modal identification of structure is proposed, which is suitable for the problem of solving large volume of data set in structural health monitoring. Numerical example of distribute computing the modal properties of truss illustrates the distributed out-put only modal identification algorithm based on NExT / ERA techniques and EFDD. This strategy can also be applied to other complicated structure to determine modal parameters.

Abstract: In order to improve efficiency and reliability for damage detection, based on the characteristics of truss structures, the elemental modal strain can be derived from the nodal modal displacements by means of the finite element method on spatial truss elements connected by pin at elemental two nodes. Therefore it is presented as a new dynamic detective indicator using changes between an intact structure and a corresponding destructive structure in the elemental lower modal strain, and then a new method of damage localization named as change in elemental modal strain is set up for truss structures. A numerical example for a planar truss structure is provided to verify the practicability of the method only by one lower mode. The results show that this method is effective to locate not only single damage but also multiple ones, both light damages and severe ones. Furthermore, the results indicate that the proposed method based on modal strain of truss elements can accurately detect damage locations of truss structures with the noisy modal data.

Abstract: Wavelet transform of strain signal can be used in the damage relative damage extent identification. The proposed method is validated by trial on a simply supported steel beam. And meanwhile the relative damage extent can be identified by drawing the curve of the maximum modulus of the wavelet coefficient and damage extent.

Abstract: High performance fiber-reinforced cement composites (HPFRCCs) show multiple cracks and a limited damage tolerance capability due to the debonding of the fibers of the cement matrix. For practical applications, it is necessary to investigate the fractural behavior of HPFRCCs to understand the mechanism of the microbehavior of a cement matrix containing reinforcing fibers. We have investigated the acoustic emission (AE) signals in HPFRCCs under monotonic and cyclic uniaxial compressive loads. Four types of specimen were tested. The experimental parameters studied were: the type of fiber (polyethylene or polyvinyl alcohol), the hybrid type (with steel cord), and the loading pattern. The data shows that the progress of the damage in HPFRCCs in the compressive mode is characteristic of the type of hybrid fiber and its volume fraction. From the AE data, the second and third compressive load cycles resulted in a successive decrease in the amplitude compared to the first compressive load cycle. In addition, an AE Kaiser effect was observed in HPFRCCs specimens up to 80% of their ultimate strength. These observations suggest that the AE Kaiser effect has potential for use as a new tool to monitor the loading history of HPFRCCs.

Abstract: As a typical composite structural type, concrete-Filled Steel Tubes (CFSTs) have been widely employed in civil engineering structures, especially in super high-rise buildings because of their enhanced load-carrying capacity and ductility. The uniformity and quality of the on-site cast concrete within the tube and the interface bonding performance between the steel tube and the concrete have received extensive attention. In this paper, Piezoelectric ceramic materials, such as Lead Zirconate Titanate (PZT) and a kind of functional smart aggregate (SA) based on PZT together are employed to evaluate the concrete quality and the bonding performance of CFST columns of a super high-rise building with a design height over 400 meters and with large cross-section CFST columns. Based on the wavelet packet analysis on the measurements of the PZT sensors, results show that no obvious damage and defect is detected and the concrete qualify and the interface of large cross-section CFST columns of this super high-rise building are in good condition. The proposed monitoring technology has great potential to be applied to practical engineering.