No abstract

In vibration-based condition assessment exercises, it is necessary to discriminate the variation of structural properties due to environmental changes from those caused by structural damage. Some efforts have been made to correlate the structural vibration characteristics and the air temperature or temperatures at the structural surface. As the temperature of an entire structure is generally non-uniformly distributed, using the air temperature or surface temperatures alone may not sufficiently capture the relation between the structural responses and temperatures. The present paper aims to investigate the variation of the structural vibration characteristics versus the non-uniform temperature field of the structure. Thermodynamic models are employed to estimate the temperature at different components of the structure at different time.As the material mechanical properties are temperature dependent, the structure can be regarded as a composite structure consisting of elements with different Young's moduli.Consequently the natural frequencies of the structure can be calculated with the finite

Monitoring deformation of super-tall structures under different environmental conditions is an important and challenging issue in assessing the safety and serviceability of structures. This paper presents a new method for calculating structural deformation using real-time strain data, which can be easily measured at different sections. Assuming the structural deformation is of bending beam type, the deformation of the structure is associated with longitudinal strain. Virtual work theory is then used to calculate the horizontal displacement and tilt angle of the building on the basis of the strain data at different heights of the structure. The proposed method is applied to the 600 m tall Canton Tower (previously known as Guangzhou New TV Tower), on which a long-term structural health monitoring system including over 400 vibrating strain gauges has been installed at different heights. The displacements and tilts of the structure top under normal and typhoon conditions are calculated using real-time monitoring strain data. The calculated deformations show good agreement with the measurements by using global positioning system (GPS) and inclinometers. The temperatureinduced maximum daily movement is similar to the value of typhoon-induced motion. Moreover, the displacement mode of the super-tall structure is also calculated and shows the bending type. Error analysis demonstrates that the calculated displacements have higher accuracy than the GPS-measured counterparts, and that the calculated tilts have similar accuracy as those measured by an inclinometer.

Abstract:The substructuring technology possesses much merit when it is utilized in model updating or damage identification of large-scale structures. However, the conventional substructuring technologies require the complete eigensolutions of all substructures available to obtain the eigensolutions of the global structure, even if only a few eigensolutions of the global structure are needed. This paper proposes a modal truncation approximation in substructuring method, in which only the lowest eigensolutions of the substructures need to be calculated. Consequently, the computation efficiency is improved. The discarded higher eigensolutions are compensated by the residual flexibility. The division of substructures and the selection of master modes in each substructure are also studied. The proposed substructuring method is illustrated by a frame structure and a practical bridge. The two case studies verify that the proposed method can improve the original substructuring method significantly.

No abstract

Traditional model updating of large-scale structures is usually time-consuming because the global structural model needs to be repeatedly re-analyzed as a whole to match global measurements. This paper proposes a new substructural model updating method. The modal data measured on the global structure are disassembled to obtain the independent substructural dynamic flexibility matrices under force and displacement compatibility conditions. The method is extended to the case when the measurement is carried out at partial degrees-of-freedom of the structure. The extracted substructural flexibility matrices are then used as references for updating the corresponding substructural models. An orthogonal projector is employed on both the extracted substructural measurements and the substructural models to remove the rigid body modes of the free-free substructures. Compared with the traditional model updating at the global structure level, only the sub-models at the substructural level are re-analyzed in the proposed substructure-based model updating process, resulting in a rapid convergence of optimization.Moreover, only measurement on the local area corresponding to the concerned substructures is required, and those on other components can be avoided. The effectiveness and efficiency of the proposed substructuring method are verified through applications to a laboratory-tested frame structure and a large-scale 600 m tall Guangzhou New TV Tower. The present technique is referred to as the inverse substructuring model updating method as the measured global modal data are disassembled into the substructure level and then the updating is conducted on the substructures only. This differs from the substructuring model updating method previously This is the Pre-Published Version. 2 proposed by the authors, in which the model updating is still conducted in the global level and the numerical global modal data are assembled from those of substructures. That can be referred to as the forward substructuring model updating method.

No abstract

Background: Emerging evidence has noted the versatile functions of mesenchymal stem cell-derived exosomes (MSC-Exos) in cancer control. This work aims to probe to function of adipose MSC-Exos (adMSC-Exos) in drug-resistance of breast cancer (BC) cells to cisplatin (DDP) and the molecules involved. Methods: Parental and DDP-resistant BC cell lines MCF-7 and MDA-MB-231 were used. All cells were pre-treated with adMSC-Exos. Then, the viability and apoptosis of cells after DDP treatment were determined. Differentially expressed miRNAs after adMSC-exo treatment were screened out. Rescue experiments were conducted by pre-transfecting miR-1236 inhibitor into adMSCs, and the role of miR-1236 in DDP sensitivity was determined. Targeting mRNAs of miR-1236 were predicted by bioinformatics analysis. Altered SLC9A1 expression was administrated to evaluate its function in DDP resistance. Results: The adMSC-Exos notably increased the sensitivity of either parental or DDPresistant BC cells to DDP. SLC9A1 was notably highly expressed in DDP-resistant cells but inhibited following adMSC-exo administration. Importantly, miR-1236, which could directly bind to SLC9A1 and suppress its expression, was confirmed as an enriched miRNA in adMSC-Exos. Either inhibition of miR-1236 or upregulation of SLC9A1 blocked the pro-sensitize roles of adMSC-Exos. In addition, the Wnt/β-catenin pathway activity was suppressed by adMSC-Exos but recovered by SLC9A1. Conclusion: This study evidenced that adMSC-Exos carry miR-1236 to increase sensitivity of BC cells to DDP with the involvement of SLC9A1 downregulation and Wnt/β-catenin inactivation. This finding may offer novel insights into treatment for drug-resistant BC.