No abstract

The excessive proliferation, endothelial migration, and phenotype transformation of vascular smooth muscle cells (VSMC) lead to increased extracellular matrix secretion, which induces vascular intimal hyperplasia, which is an important restenosis mechanism after vascular injury. In our study, we verified the cytotoxicity of SiO2 nanoparticles to VSMC. To explore the role of endothelial repairs and molecular mechanisms after vascular injuries, we sequenced the transcriptome of injured vessels in the carotid artery of mice. The results showed the differentially expressed genes in normal vascular tissues, and that vascular tissues were mainly enriched with NF-κB signaling pathways, chemokine signaling pathways and other biological functions, by the leukocyte activation and adhesion of the KEGG pathway in the immune response, and by DNA binding, DNA transcription regulatory region binding, and other molecular functions. Core proteins included PRKCB, STAT4, CCL5, and BCL-2. To verify the roles of these core proteins, RT-qPCR andWestern blot techniques were used to detect their transcription and translation levels, and HE staining was used to detect morphological changes in blood vessels. To further clarify the role of core proteins in VSMC, PRKCB over expression plasmids were constructed, and the RT-qPCR and Western blot techniques were again used to detect the expression of core proteins. The results showed that the levels of transcription and translation, and of PRKCB and STAT4 phosphorylation, increased significantly after vascular injury, and then noticeably decreased three days later- and that CCL5 and Bcl-2 expression trends were consistent with this. HE staining showed that when the vascular endothelium was damaged, smooth muscle cells proliferated significantly, and that the intima thickened three days after vascular injury. After over expression of PRKCB, the expression and activation of STAT4, CCL5, and Bcl-2 significantly increased, α-SMA and Vimentin were down-regulated, OPN was up-regulated, and VSMC activity was enhanced. From these results, it could be concluded that PRKCB is activated by vascular injury, and that over-activation of PRKCB promotes activation of STAT4 and the expression of CCL5 and BCL-2—which in turn leads to enhanced VSMC activity and transformation of its contraction phenotype to the secretion phenotype. We were also able to establish that the cytotoxicity of SiO2 nanoparticles to VSMC was positively correlated with dose and time.

To investigate the seismic performance of prefabricated piers with a grouting sleeve connection, two scaled model specimens of symmetrical prefabricated piers with different reinforcement anchorage lengths, and two cast-in-place (CIP) comparison symmetrical specimens, were designed and manufactured. The fabricated specimens were connected by a grouting sleeve, which was in the column of the pier. The height of the pier column of the test piece was 1.425 m, the diameter of the pier column was 0.25 m, and the size of the bearing platform was 0.85 m × 0.85 m × 0.5 m. Shake table tests were performed on the specimens to evaluate crack development, dynamic characteristics, acceleration response and relative displacement of the pier tops, as well as strain in the plastic hinge area. The results revealed the dominant failure mode of the test piers was bending failure, while the cracks were generally horizontal through-cracks. The failure location of the prefabricated specimens with the grouting sleeve was concentrated within one diameter of the pier in the upper sleeve region. Compared with the CIP specimens, the plastic hinge exhibited an obvious upward movement. Under a maximum test loading condition, the peak acceleration at the pier top of the fabricated pier was 11.0% smaller than that of the CIP specimen, the peak relative displacement was 34.2% smaller than that of the CIP specimen, and the peak tensile strain of the pier body was 46.8% smaller. The seismic performance of the prefabricated pier connected via the grouting sleeves was barely affected by changing the anchoring length of the reinforcements in the grouting sleeves. An ABAQUS finite element model was established for the specimens, with good agreement between the model and experimental results. When the seismic load was 0.65 g, the difference between the peak acceleration of the pier top in the X direction and the Y direction of the numerical simulation and the experimental data was less than 15%.

To study the seismic performance of prefabricated single-segment steel jacket piers connected by grouting sleeves, two scaled symmetrical pier models with different anchorage lengths of the longitudinal reinforcement in the grouting sleeves and a comparative symmetrical cast-in-place (CIP) model were designed. OpenSees finite element models were established and shaking table tests were carried out on the three scaled pier models. The seismic response of each pier was compared and analyzed. Results showed the stiffness of the two prefabricated piers was greater than that of the CIP pier, and other seismic responses were less than those of the CIP piers, The dynamic responses of the two prefabricated bridge models were similar and changing the anchorage length of the reinforcement in the grouting sleeve had little effect on the seismic performance of the prefabricated pier. The simulation results were in good agreement with the experimental results. In the parameter analysis, the counterweight of the pier top had the greatest influence on the seismic performance of the prefabricated pier. The anchorage length of the longitudinal reinforcement in the grouting sleeve could be 6–14 times the diameter of the longitudinal reinforcement. Moreover, the seismic performance was found to be optimal when the thickness of the steel jacket was 5–7 mm.

PurposePrefabricated pier technology has the advantages of quick construction time, relatively little traffic interference and relatively small environmental impact. However, its applicability under earthquake conditions is not yet fully understood. The seismic performance and influence parameters of a prefabricated concrete pier connected by embedded grouting sleeve (GS) in a pile cap are investigated in this study.Design/methodology/approachTwo prefabricated pier scale model specimens with different reinforcement anchorage lengths and two comparative cast-in-place (CIP) pier model specimens are designed and manufactured for a seismic simulation shaking table. With the continuous increase of input ground motion strength, the changes in basic dynamic characteristics, damage development, acceleration and displacement variation laws, and pier bottom strain responses are compared among the specimen. The finite element software ABAQUS is used to simulate the test pier.FindingsThe crack location of the two prefabricated pier specimens is almost the same as that of the CIP pier specimens; CIP pier specimens show more penetrated cracks than prefabricated pier specimens, as well as an earlier crack penetration time. The acceleration, displacement and strain response of the CIP pier specimens are more affected by earthquake activity than those of the prefabricated pier specimens. The acceleration, displacement and strain responses of the two prefabricated piers are nearly identical. The finite element results are in close agreement with the acceleration and displacement response data collected from the test, which verifies the feasibility of the finite element model established in ABAQUS.Originality/valueA GS connection method is adopted for the prefabricated pier, and on the premise of meeting the minimum reinforcement anchorage length required by the code, this study explores the influences of different reinforcement anchorage lengths on the seismic performance of prefabricated piers in high-intensity areas. A shaking table loading test is used to simulate the real changes of the structure under the earthquake. This work may provide a valuable reference for the design and seismic performance analysis of prefabricated pier, particularly in terms of seismic stability.