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Evaluating the technical conditions and performance for historic bridges is essential to ensure their structural safety and determine their need for strengthening. This study investigates the first railway steel bridge built in China in 1894, which is listed as a national preservation unit and industrial heritage site. The bridge was not only exposed to years of weather change but also suffered a geological disaster in 1976. In addition, the surroundings have changed, including the construction of new railway lines and scenic areas. Thus, it is imperative to evaluate its technical conditions and performance, particularly its material properties. To this end, evaluation procedures were formulated. First, the material composition, properties, and grades of steel were determined by microstructural analysis: the grade of nonmetallic inclusions in steel was determined by metallographic analysis; the corrosion rate of steel was obtained by electrochemical analysis; and the crystal type, size, element product of the corrosion layer, as well as the fracture type of the steel, were analyzed by phase composition and elemental analysis. Next, the static performance indices of the steel were obtained by mechanical property tests: the hardness value of the steel was obtained from hardness test; the yield and tensile strengths of the steel were obtained from tensile tests; and the fatigue properties of the steel were analyzed through fatigue tests. The S-N curve of the steel was determined by fitting the tested data. This study provides a reference for the evaluation of the technical conditions and performance of historic bridges. [ABSTRACT FROM AUTHOR]

A graph is an abstract model that represents relations among entities, for example, the interactions between characters in a novel. A background story endows entities and relations with real-world meanings and describes the semantics and context of the abstract model, for example, the actual story that the novel presents. Considering practical experience and prior research, human viewers who are familiar with the background story of a graph and those who do not know the background story may perceive the same graph differently. However, no previous research has adequately addressed this problem. This research article thus presents an evaluation that investigated the effects of background stories on graph perception. Three hypotheses that focused on the role of visual focus areas, graph structure identification, and mental model formation on graph perception were formulated and guided three controlled experiments that evaluated the hypotheses using real-world graphs with background stories. An analysis of the resulting experimental data, which compared the performance of participants who read and did not read the background stories, obtained a set of instructive findings. First, having knowledge about a graph's background story influences participants’ focus areas during interactive graph explorations. Second, such knowledge significantly affects one's ability to identify community structures but not high degree and bridge structures. Third, this knowledge influences graph recognition under blurred visual conditions. These findings can bring new considerations to the design of storytelling visualizations and interactive graph explorations. [ABSTRACT FROM AUTHOR]

This article presents analysis of deterioration indicators for a comparative quantification of the operational structural performances of bridge inventories. The analysis considers the various kinds of material in the entire database of the US National Bridge Inventory. The multi-criteria approach integrates the indicators of deterioration, considering diagnostic condition and life cycle to determine the equivalent operational structural performances. This study also uses reconstruction data to determine an additional deterioration indicator for performance. The proportional effort for reconstruction reflects the practical need to counter deterioration and preserve a required level of structural performance, under all circumstances. The presented addition of reconstruction performance provides a more comprehensive assessment of bridge performance. The results reveal the continuous efforts to maintain a relatively balanced performance adequacy at the national level within the prevailing funding constraints. Reconstruction performances are generally higher than deterioration trends (rate and pattern) performances, revealing that the constrained reconstruction efforts have difficulty to keep pace with the actual deterioration. [ABSTRACT FROM AUTHOR]

Taking the optimal sensor placement problem in bridge structural health monitoring as the study object and relying on the engineering example of a simply supported steel truss bridge, the improved optimal sensor placement method based on sensitivity‐effective independence method was proposed. Using the sensitivity coefficient reflecting structural damage, the proposed method could modify the effective independence method reflecting the maximum linear independence. The proposed method further optimizes the sensor placement method. A method for selecting the number of models based on modal closeness was proposed and makes the selection of the number of modes more objective. The example analysis shows that evaluations using this method are effective for multiple evaluation criteria. The method ensures observability of the mode vector and identifiability of structural damage. It is an effective optimal sensor placement algorithm for the bridge structure. [ABSTRACT FROM AUTHOR]

What is the current state-of-the-art for image restoration and enhancement applied to degraded images acquired under less than ideal circumstances? Can the application of such algorithms as a pre-processing step improve image interpretability for manual analysis or automatic visual recognition to classify scene content? While there have been important advances in the area of computational photography to restore or enhance the visual quality of an image, the capabilities of such techniques have not always translated in a useful way to visual recognition tasks. Consequently, there is a pressing need for the development of algorithms that are designed for the joint problem of improving visual appearance and recognition, which will be an enabling factor for the deployment of visual recognition tools in many real-world scenarios. To address this, we introduce the UG $^2$ 2 dataset as a large-scale benchmark composed of video imagery captured under challenging conditions, and two enhancement tasks designed to test algorithmic impact on visual quality and automatic object recognition. Furthermore, we propose a set of metrics to evaluate the joint improvement of such tasks as well as individual algorithmic advances, including a novel psychophysics-based evaluation regime for human assessment and a realistic set of quantitative measures for object recognition performance. We introduce six new algorithms for image restoration or enhancement, which were created as part of the IARPA sponsored UG $^2$ 2 Challenge workshop held at CVPR 2018. Under the proposed evaluation regime, we present an in-depth analysis of these algorithms and a host of deep learning-based and classic baseline approaches. From the observed results, it is evident that we are in the early days of building a bridge between computational photography and visual recognition, leaving many opportunities for innovation in this area. [ABSTRACT FROM AUTHOR]

• The effectiveness of various strengthening techniques for timber bridges is discussed. • Suitable strengthening methods are identified in terms of girder deflections, reliability, efficiency, and live load distribution. • Parametric investigations are conducted to elucidate the implications of variable geometric configurations and live load intensities. This paper presents the behavior of a timber bridge strengthened with lag bolts, carbon fiber reinforced polymer (CFRP) sheets, and hollow structural sections (HSS). The 83-old bridge is composed of three spans, supported by 14 Douglas Fir girders, and is tested employing truck loadings of 120 kN and 267 kN. Three-dimensional finite element models are formulated to study the flexural response of the bridge with and without the retrofit options. The magnitude of the truck load dominates the degree of dispersion in girder deflections and alters the shape of probability density functions, which are associated with behavioral uncertainty. The effectiveness of strengthening is apparent in terms of reducing the exceedance probability of deflection limits and increasing reliability indices above the design threshold of β = 3.5, stipulated in bridge specifications. Among the three methods, the stiffening efficiency of the HSS option is higher at the system level; however, the use of CFRP is most efficient at the member level. Live load distribution factors are examined and implementable recommendations are provided for practice. Parametric investigations clarify the efficacy of variable HSS sizes and the ramifications of a permit truck weighing 445 kN. [ABSTRACT FROM AUTHOR]

• Short-period SHM system is used to assess the bridge safety. • Proposed PARIMA approach used for analyzing the reliability of bridge girders. • PARIMA is significant in detecting structures behaviors. Evaluation and modeling of structures behavior over their service life are crucial parameters for construction safety. This research investigates the use of output-only structural health monitoring (SHM) to evaluate the reliability and safety of highway steel plate girders of WonHyo bridge. Displacement, strain and acceleration measurements were used to assess the bridge behavior under the designed static, semi-static and dynamic truck loads effects. A novel integration method with combined probability, Autoregressive and Integrated Moving Average (ARIMA) identification model was developed to design PARIMA approach, which is introduced and used for analyzing the semi-static and dynamic reliability of the bridge girders. The PARIMA experimentally evaluated structure's reliability and damage based on the output only SHM system. The results showed the effectiveness of PARIMA for detecting structures damages and analyzing structure's reliability in semi-static and dynamic domains. The evaluation of WonHyo bridges showed its performances in time and frequency domains are safe, and the bridge reliability is high. [ABSTRACT FROM AUTHOR]