The spatial structure of sintered metal powders is described by many qualitative and quantitative micro-geometrical properties. The statistical approach based on univariate and multivariate distributions is very useful for consistent and objective description of such structures. It provides information appropriate for a whole population of sinters, not only particular specimen. Empirical distributions of quantitative properties obtained from the image analysis are very irregular and for this reason inconvenient for further numerical simulations. The smoothing of these distributions is required for data conditioning and preprocessing however, the use of simple regression techniques is limited due to the strict lower and upper bound of cumulative distribution function. Authors propose to use a multilayer perceptron as a non-parametric regression model because of its the well-known smoothing properties. The technical application of such model requires additionally providing of the confidence band or any equivalent measure of uncertainty. The highly non-linear structure of the neural network model makes not possible to use typical linear techniques to estimate variance. Additionally, the simple confidence band estimation leads to non-physical values of the cumulative distribution function: lower than 0 or greater than 1. Authors propose to avoid such difficulties by two methods. Firstly, the lower and upper bound limitation are satisfied by the logit transformation which projects the range into unlimited real range. Secondly, the variance of the neural network model is estimated by jackknife estimator. The article presents such approach with preliminary attempt to an automated data processing by ADCIS Aphelion image analysis software and STATSOFT Statistica data analysis software. The almost full automation of the process is required by materials science engineers due to the lack of the sufficient data processing knowledge and skills. Both software systems provide suitable embedded programming environments: C# for Aphelion and Visual Basic for Statistica. The proposed approach has been tested on the example of pore size distribution in sintered stainless steel AISI 434L.

关键词：神经网络逼近；准确估计；重叠

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Illinois, like many other large states, has several microclimates where temperature and rainfall can vary. These variations can affect the corrosion rates of sign and signal structures, light poles, and other highway structures. Each atmospheric zone, whether they are rural, semirural, suburban, industrial, or marine areas, may be subjected to salt fall or salt spray, which can affect metals or coatings after prolonged exposure. These highway structures are typically fabricated from weathering steel, galvanized steel, painted steel, or aluminum. Each of these metals and their coatings bear a fabrication cost and have distinct ranges of durability in different atmospheres. Rural and semi-rural atmospheres cause the least corrosion damage to metal and coated surfaces. Suburban environments generally have moderate effects, compared to industrial and saline areas, which have the most corrosive atmospheres. Weathering steels have greater durability in moderate and many industrial atmospheres compared to carbon steels, such as ASTM A36 or SAE 1020. The cost differences between ASTM A36 and ASTM A588 vs. the ASTM A710 Grade 50 steel described in this report are small. Based on data obtained from WorldSteelPrices.com, as of July 2013, the price of ASTM A36 was about $0.295 per lb compared to $0.340 per lb for ASTM A588. Because A710 has slightly higher nickel and copper contents than A588, its cost is estimated to be about $0.36 per lb, based on a metric tonne.

关键词：涂料；耐腐蚀；损害；钢铁

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Bridge foundations contribute significantly to the serviceability and efficiency of in-service transportation networks. Foundation failure may lead to catastrophic failure of the entire structure, which in turn results in system failure, loss of life, and detours. When the soil within ground surface layers fails to satisfy the bearing capacity requirements, deep foundations such as tubular-steel concrete-filled piles are commonly used in practice. A challenge that often exists with these systems is the uncertainty surrounding in-service capacity as well as condition, which is difficult to determine from the surface. As a consequence, transportation agencies such as the Wisconsin Department of Transportation use conservative approaches, such as neglecting the tubular-steel contribution or bounding the compressive strength of the core concrete, to design these systems. This approach, while effective for safety, can yield overly conservative and costly designs. The main purpose of this investigation was to evaluate the behavior of tubular-steel, concrete-filled, cast-in-place pilings, with a concentration on the compressive strength and composite behavior between concrete core and steel shell. In this regard, a series of experimental studies, including composite and noncomposite compression loading, core samples, push-through, and flexural testing together with a compatible finite element analysis, were conducted on a series of field-cast piles with different geometrical properties. The results indicated that the steel shell made a significant contribution to the axial loading capacity of the cast-in-place piles. Moreover, no evidence of bond loss was observed during the corresponding experimental studies.

关键词：管状钢铸；钢铁；打桩

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The structural reliability analysis is the widely accepted method for bridge safety assessment. Identification the subset of significant failure modes is the most important part of system reliability estimation. In this paper, a stage critical strength branch and bound algorithm is proposed for the failure mode identification of bridge systems. The innovative method is implemented in the combination with the finite element package ANSYS and the MATLAB procedure. The suggest method is applied to a concrete filled steel tubular (CFST) arch bridges. The results reveal various combinations of the failure modes in significantly reduced time and efforts in comparison to the previous permutation method. Additionally, the suggested method can be used for the verification of the system reliability with more specific predictions of the failure mode.

关键词：拱桥；故障模式；识别策略；交通负荷

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In recent decades, bridge fires have become a major concern in the U.S. Fire hazard in bridges can result in significant economic and public losses. New construction of bridges often use Weathering Steel (also known as Corten Steel), which has a corrosion-retarding effect since the steel forms a protective rust layer on its surface under the influence of the weather. To date, no information exists on the high temperature mechanical properties of weathering steel. The objective of this work is to develop a database of mechanical properties of A588 weathering steel that has been exposed to high temperatures. These properties include the residual (after heating and cooling) stress-strain, fracture toughness, and surface hardness. The parameters that are investigated include temperature (800 degrees F, 1000 degrees F, 1200 degrees F, and 1500 degrees F), cooling methods (in air (CIA), and in water (CIW), representing fire-fighting effects), and material. Experiments are also done in a steady-state elevated temperature condition. A comparison is made between A588 weathering steel, used widely for bridges, and another material whose chemical composition and mechanical properties allows it to be classified by ASTM as both an older weathering steel (A242), a steel commonly used in building construction (A992), and also a non-weathering steel used for bridges (A709 Grade 50).

关键词：桥梁（构）筑物；化学成分；腐蚀；钢铁

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The development length of reinforcements embedded into ultra-high performance concrete (UHPC) can be significantly shorter than the lengths normally associated with conventional concrete. Shortening the development length of prestressing strand can allow for a redesign of some structural systems, including spliced girder and continuous-for-live-load bridges. Ultra-high performance concrete (UHPC), when used in field-cast connections between prefabricated bridge elements, can create robust connections which emulate monolithic components. This study investigated the development length of 0.5 and 0.6 inch (12.7 and 15.2 mm) diameter untensioned prestressing strands embedded in steel fiber and PVA fiber reinforced UHPC. The volumetric fiber content was 2 percent. A novel tension test method allowed for replication of the tension-tension stress state that would occur when two strands are lap spliced within a connection between two linear elements. The results suggest that, for the steel fiber reinforced UHPC, the 0.5 inch (12.7 mm) diameter strands can be fully developed within 20 inches (0.51 m) and the 0.6 inch (15.2 mm) diameter strands can be fully developed in approximately 24 inches (0.61 m). The 0.5 inch (12.7 mm) diameter strands can be fully developed in the PVA fiber reinforced UHPC in approximately 36 inches (0.91 m).

关键词：高强度混凝土；钢绞线;桥梁；纤维增强混凝土

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Metal framing and glass is a broad category of exterior enclosure systems that includes storefront, window wall, and curtain wall systems. The metal framing components are primarily aluminum, but also include stainless steel, bronze, or other architectural quality metals. Infill supported by or within the framing includes transparent or opaque materials. Transparent infill materials include insulating, laminated, or monolithic glass; polycarbonates; and thermoplastics. Opaque infill materials include architectural metals such as aluminum, stainless steel, or bronze; natural stone; fiber reinforced panels; terra cotta; or louvers.

关键词：金属框架；不透明填充材料；钢铁

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Driven piles are subjected to high stresses during installation. It is, therefore, important not to exceed acceptable stresses along the pile shaft and at the toe to prevent damage. Dynamic monitoring has been used for decades to evaluate not only the installation stresses, but also check test piles for signs of structural damage. The Beta Method (?-Method) for evaluation of the location and extent of a potential damage was developed over thirty years ago and has proven effective as a QC and QA tool. As an aid in the process of pile rejection or acceptance, the ?-Method also offers a rating scale which translates the automatically determined ?-number into a helpful pile integrity assessment tool. The reliability of this algorithm has been proven by numerous extracted piles. However, one limitation of the ?-method concerned detection of damage near the pile toe where high toe resistance effects and/or stress wave reflections reduce the effectiveness of the traditional ?-Method. In the past, therefore, near-toe damage was determined by the testing engineer, not only by visual inspection of the dynamic monitoring data, but also by reviewing the pile toe compressive stresses throughout the monitored driving history and the strength and stiffness of the soil response from the pile toe. This approach has now been automated and subjected to tests on existing data. After a review of the existing methods of pile stress and damage calculations, the paper presents the new method, illustrating its effectiveness by examples from measurements on both concrete and steel piles.

关键词：打入桩；钢铁；动态监测

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Spiralnails are hollow steel pipes extruded and twisted to form a square helical shape. They are driven rather than drilled, and thus they do not require cement grout to develop a bond with the soil, and provide immediate internal stability improvement to a soil mass. Because effective and economical designs require an improved understanding of individual and group spiralnail behavior, a 6-m (20-ft) tall, top-down vertical excavation was constructed using spiralnails in a well-characterized, engineered fill. The spiralnail reinforcement design used existing soil nail design methods to achieve an acceptable factor of safety using nail lengths and spacing comparable to those common for a conventional grouted nail design. The objective of the project was to measure the performance of the spiralnail reinforced soil mass in order to evaluate the applicability of existing soil nail design methods to spiralnail design. The paper describes the design, construction, soil characterization and properties, instrumentation, and presents the measured load-displacement behavior of the spiralnails and observed deformation of the reinforced soil mass. A preliminary analysis of load-displacement data is presented, and calculated spiralnail equivalent bond stress values are provided. Based on the measured deformations and using an empirical correlation, the spiralnail-reinforced soil mass performance is compared to a grouted nail-reinforced soil mass.

关键词：钢管挤压；钢铁；荷载位移数据

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The world shipbuilding industry since the beginning of the last century with flux cored wire material.Since the flux cored wire material use welding materials has developed into a more efficient submerged arc welding consumables and gas shielded welding welding consumables and can be more easily combined with automated welding and robot welding.So far,flux cored material applications favored.Gas shielded arc welding consumables mainly divided solid wire and flux cored wire,flux cored wire applications has increased year by year because of its practicality and efficiency.Flux cored wire as the main welding consumables trends,especially in the thick carbon steel plate welded favored.In order to understand the nature of the thick-walled components weld cracking and produces original Due on a thick-wailed T-joints butt weld ultrasonic flaw found Two crack metallographic and SEM fracture analysis.

关键词：药芯焊丝材料；气体保护；焊接裂纹

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