Prediction of long-term creep deflection of seismic isolation bearings

Isolation structures use high damping rubber bearings (HDRBs), lead rubber bearings (LRBs), and natural rubber bearings (NRBs) in order to significantly reduce the seismic forces transmitted from a substructure to a superstructure. The laminated rubber bearing is the most important structural member of a seismic isolation system. We present an analysis of a 1000 hr ongoing creep test conducted at 7.5 and 8.37 MPa in our laboratory. The long term behavior of bridge bearings (e.g., laminated rubber bearings) is determined through compression creep tests subjected to actual environmental conditions. These tests indicate that the maximum creep deformation is about 0.3 to 1.92 % of the total rubber thickness

Exercise training-induced PPARβ increases PGC-1α protein stability and improves insulin-induced glucose uptake in rodent muscles

This study aimed to investigate the long-term effects of training intervention and resting on protein expression and stability of peroxisome proliferator-activated receptor β/δ (PPARβ), peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC1α), glucose transporter type 4 (GLUT4), and mitochondrial proteins, and determine whether glucose homeostasis can be regulated through stable expression of these proteins after training. Rats swam daily for 3, 6, 9, 14, or 28 days, and then allowed to rest for 5 days post-training. Protein and mRNA levels were measured in the skeletal muscles of these rats. PPARβ was overexpressed and knocked down in myotubes in the skeletal muscle to investigate the effects of swimming training on various signaling cascades of PGC-1α transcription, insulin signaling, and glucose uptake. Exercise training (Ext) upregulated PPARβ, PGC-1α, GLUT4, and mitochondrial enzymes, including NADH-ubiquinone oxidoreductase (NUO), cytochrome c oxidase subunit I (COX1), citrate synthase (CS), and cytochrome c (Cyto C) in a time-dependent manner and promoted the protein stability of PPARβ, PGC-1α, GLUT4, NUO, CS, and Cyto C, such that they were significantly upregulated 5 days after training cessation. PPARβ overexpression increased the PGC-1α protein levels post-translation and improved insulin-induced signaling responsiveness and glucose uptake. The present results indicate that Ext promotes the protein stability of key mitochondria enzymes GLUT4, PGC-1α, and PPARβ even after Ext cessation

How Learner-Centered Teaching is associated with Teacher Self-Efficacy and Job Satisfaction: Analysis of Data from 31 Countries

The expansion of learner-centered teaching has been the focus of education policy makers and teachers throughout the world. While most of the attention has been given to how learner-centered teaching influences student outcomes, it is important to consider how teachers are associated with learner-centered teaching. Using data from the OECD TALIS database, this study analyzes how the use of learner-centered teaching is associated with teacher self-efficacy and job satisfaction. Controlling for a wide range of teacher and classroom characteristics, as well as country and school fixed effects, we find that learner-centered teaching has a significant and positive association with both teacher self-efficacy and job satisfaction

Mechanical behavior of seismic isolation bearings in earthquake-induced ultimate limit state

High-damping rubber bearings, lead rubber bearings, and natural rubber bearings are often used to improve the seismic capacity of seismic isolation bearings. We present the results of an extensive series of experimental tests to identify the mechanical characteristics of these three types of seismic isolation bearings. Cyclic horizontal displacement tests, varying the test parameters of shear displacement amplitude axial load, and loading frequency tests were performed on each type of bearing. Bearing shear stiffness and damping properties were investigated in terms of the different test parameters. The ultimate tests consisted of monotonic shear loading to failure under axial loads, and tension failure tests of the bearings with bolted connections. Comparisons are made between experimental results and available analytical relationships for material and bearing properties

A study on the characteristics of bridge bearings behavior by finite element analysis and model test

The increased vibration level of the railway bridge could make significant noise and, also, cause structural damages such as fatigue cracks. Related to these subjects, a spherical elastomeric bridge bearing, which is layered by hemispherical rubber and steel plates, was investigated in terms of its vibration performance. Several different shape factors could be considered by changing the curvature of hemispherical surface and size in rubber and steel plate thicknesses in the manufacturing stage. The performance of the spherical elastomeric bearing for the reduction in vibration was compared with that of the conventional bearing by performing vibration experiments on a scale-downed model. The rubber material characteristics and spherical shape are found to be important parameters in reducing the bridge vibration