Reinforced concrete bridges are iconic parts of modern infrastructure. They are designed for a minimum service life of 100 years. However, environmental factors and/or inappropriate use might cause overload and accelerate the deterioration of bridges. In extreme cases, bridges could collapse when necessary maintenance lacks. Thus, the permanent monitoring for structure health assessment has been proposed, which is the aim of structural health monitoring (SHM). Studies in laboratories have shown that ultrasonic (US) coda wave interferometry (CWI) using diffuse waves has high sensitivity and reliability to detect subtle changes in concrete structures. The creation of micro-cracks might be recognized at an early stage. Moreover, large-volume structures can be monitored with a relatively small number of US transducers. However, it is still a challenge to implement the CWI method in real SHM practical applications in an outdoor environment because of the complex external factors, such as various noise sources that interfere with the recorded signals. In this paper, monitoring data from a 36-m long bridge girder in Gliwice, Poland, instrumented with embedded US transducers, thermistors, and vibrating wire strain gauges, is presented. Noise estimation and reduction methods are discussed, and the influence of traffic, as well as temperature variation, are studied. As a result, the relative velocity variation of US waves following the temperature change with a very high precision of $$10^{-4} \%$$ 10 - 4 % is shown, and a good bridge health condition is inferred. The influence of lightweight real traffic is negligible. The study verified the feasibility of the implementation of the CWI method on real bridge structures.
A 3D coupled model considering electromagnetic field, flow field, heat transfer, and particle transport is developed to predict the effect of stirrer position on the magnetic field distribution, fluid flow streamlines, temperature distribution, and inclusion removal in 180 mm × 220 mm billet continuous casting process, and the effect of stirrer position on the mold‐level fluctuation and slag entrapment behavior is also studied based on the homogeneous model. The casting temperature of molten steel is 1750 K, and the casting speed of billet is 0.9 m min−1. The results indicate that as the stirrer center position is lowered, the maximum value of the magnetic induction intensity has almost no change, whereas the maximum value of the tangential electromagnetic force initially decreases followed by an increase. With the downward movement of stirrer center position, the decrease rate of central molten steel velocity slows down, and the range of the upper circulation flow zone increases. A lower stirrer center position increases the cooling of the billet and inclusion removal. When the stirrer center position is moved from 515 to 815 mm, the wave height of steel/slag interface decreases from 11.6 to 3.4 mm, and slag entrapment behavior gradually weakens.
Design tools exploit design hierarchy for speed, efficiency and reuse. Conventional OPC solutions, however, do not fully exploit such structures and hence are not very efficient. Since a cell may be instantiated thousands of times in a design, this implies that redundant OPC operations are usually applied, at the cell instance level, repeatedly to the same master cell within the context of the design. Some cell-based OPC studies have been performed in an attempt to alleviate such inefficiency. For example, Gupta, Heng and Lavin 1 have shown that a simple cell-based (book-based) OPC approach has negligible OPC imperfectness around cell boundaries but has an average P/D speed-up, where P is the number of master placement cells and D is the number of master cells.This article presents an alternative approach to the above mentioned works. Here, we illustrate that it is not only possible to apply OPC on a per-cell basis, but also to "stitch" already corrected cells along their interacting areas together to form a proximity corrected final layout. Because of the stitching steps, our approach can handle more practical and complicated hierarchical layouts than those described in Gupta et al. and achieve OPC quality equivalent to that obtained using conventional OPC methods. In addition, since our approach performs the majority of OPC work at the cell level, we can maintain the runtime savings comparable to that demonstrated by Gupta et al. This technique of localized OPC reconfiguration can be extended to handle applications such as manufacturing ECO handling and design re-spins.
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