The run sum chart is an effective two-sided chart that can be used to monitor for process changes. It is known that it is more sensible than the Shewhart chart with runs rules and its performance improves as the number of regions increases. However, as the number of regions increses the resulting chart has more parameters to be defined and its design becomes more involved. In this article, we introduce a one-parameter run sum chart. This chart accumulates scores equal to the subgroup means and signals when the cummulative sum exceeds a limit value. A fast initial response feature is proposed and its run length distribution function is found by a set of recursive relations. We compare this chart with other charts suggested in the literature and find it competitive with the CUSUM, the FIR CUSUM, and the combined Shewhart FIR CUSUM schemes.
<p>The use of prestressed concrete (PSC) box girder bridges built by segmentally balanced cast-in-place cantilevers has spread massively due to noticeable advantages over traditional. However, excessive deflections have been observed in 10-years old constructed bridges worldwide which have been designed based on old international code standards that underestimated rheological effects. To guarantee 100-year design life of bridges, it is necessary to have a periodic monitoring system that validates in-service performance. In Colombia there is a necessity to study in-service performance of this type of bridges after its construction, which is the main solution for structures with spans ranging from 80 m to 200 m, therefore this study seeks to propose a procedure to estimate the long-time behavior of box girder bridges in Colombia considering construction data scarcity. Therefore, altimetry data measured from a newly constructed bridge is collected, and the rheological effects of the structure are predicted using models previously developed and validated. Finally, a comparative analysis is carried out and guidelines are provided to propose a practical monitoring framework that guarantees adequate in-service bridge performance.</p>
En este artículo se expone un procedimiento para calcular el coeficiente de determinación $ R^2_{i} $, del modelo de regresión lineal múltiple $\, Y=X\beta+e$ ajustado después de eliminar el $i$-ésimo registro. El procedimiento permite observar el comportamiento del coeficiente de determinación, cuando el registro eliminado es influyente para la suma de cuadrados residual $SCE$ según la estadística $Q_{i}$. Se incluye la sintaxis para realizar los cálculos en R.
<p>Bridges in the road infrastructure represent a critical and strategic asset, due to their functionality, is vital for the economic and social development of the countries. Currently, approximately 50% of construction industry expenditures in most developed countries are associated with repairs, maintenance, and rehabilitation of existing structures, and are expected to increase in the future. In this sense, it is necessary to monitor the behaviour of bridges and obtain indicators that represent the evolution of the state of service over time.</p><p>Therefore, degradation models play a crucial role in determining asset performance that will define cost-effective and efficient planned maintenance solutions to ensure continuous and correct operation. Of these models, Markov chains stand out for being stochastic models that consider the uncertainty of complex phenomena and are the most used for structures in general due to their practicality, easy implementation, and compatibility. In this context, this research develops degradation models of a database of 414 prestressed concrete bridges continuously monitored from 2000 to 2016 in the state of Indiana, USA. Degradation models were developed from a rating system of the state of the deck, the superstructure, and the substructure. Finally, the database is identified and divided from cluster analysis, into classes that share similar deterioration trends to obtain a more accurate prediction that can facilitate the decision processes of bridge management systems.</p>
The balanced cast-in-place cantilever erection method has become a popular construction bridge technique. The main advantages include an industrialized erection technique that prevents the use of intermediate supports and rapid construction. However, the long-term response of this bridge typology is not well understood as long-term deflections due to time-dependent phenomena (such as creep and shrinkage) are significantly simplified in bridge design codes. Existing prediction models commonly used in design tend to underestimate long-term deflections, and as a result, field measurements conducted in newly constructed bridges still report excessive long-term deflections. This paper shows the long-term deflection analysis of a long-span concrete bridge located in Colombia and opened to traffic in 2014. This study is conducted using field data collected within a one-year time interval and modelling results. Further comparisons using field data collected from bridges with similar structural configurations, but opened to traffic in the 90s and 2000s, show that the bridge's current situation is categorized as a major concern.
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