In recent decades, orthotropic steel decks (OSDs) have been routinely incorporated into long-span bridges. The most widely used method to reduce stress concentration, improve fatigue performance, and control crack propagation is to cut out the diaphragms (or subfloor beams) into which the OSDs frame. However, the capital cost of cutout fabrication in the United States is high and may not be economically feasible. Study is required of cost-effective modified design details without cutouts as well as comparisons with their corresponding flexural and fatigue performance against current design details that use cutouts. Alternative design details (e.g., deck ribs welded directly to the transverse diaphragms using full-penetration welds) with thicker deck plates, but without cutouts, were investigated for potential improvements in fatigue resistance and capital cost. A parametric study was conducted with calibrated finite element models of a portion of the Bronx-Whitestone Bridge in New York City to study the effects of cutouts, deck plate thickness, and other important parameters on fatigue performance. Various traffic load combinations and truck types were considered with the use of an elaborate weigh-in-motion database. Results detail the equivalent stress ranges at critical locations in the OSDs that were calculated to quantitatively estimate fatigue lives for two OSD models: one with cutouts and one without. On the basis of these comparisons, recommendations related to overall structural performance were made to ensure a safe and rational design for various OSD options in long-span bridges.

关键词：正交异性钢桥；钢铁；桥面

查看摘要 索取原文[10页]

The discovery in the 1980's of local brittle zones (LBZ's) in and near the heat-affected zone (HAZ) of the fabrication welds in certain offshore platform steels caused great concern among the engineers and welding specialists of the period and led directly to the preparation and adoption of API RP2Z in May 1987 of Recommended Practice for Preproduction Qualification for Steel Plates for Offshore Structures. This recommended practice describes a procedure by which steel producers could prequalify their product in advance of purchase and delivery and thereby reduce the risk of steel plate being delivered to the jobsite which would exhibit weldability problems from the standpoint of low HAZ toughness or HAZ cracking problems when using typical and conventional welding procedures, i.e., the need for extensive fracture toughness testing by the fabricator on each weld procedure was eliminated in favor of a more sophisticated one-time test program in the laboratory of the producer. This recommended practice covers two areas: (1) testing weld HAZ for toughness using CTOD tests and (2) delayed cracking tests using the controlled thermal severity test (CTS) and Y-groove test. This RP was developed for use with API steel specifications 2H, 2Y, and 2W. Most of the effort has been toward the quantification of API 2Y and 2W steels in thicker sections s4" (100 mm). This program has been scientifically successful albeit with a significant penalty of time and cost to the steel producer. There has been sufficient standardization that various purchasers have and will accept the same qualification performed previously for another job. This, of course, is exactly what API standards are intended to accomplish. API RP2Z was revised in 1992 and is currently being reviewed for a second revision intended to reduce some of the conservatism built into the original document by our lack of full understanding of the embrittling mechanisms in the HAZ of welded structural steels but now strongly supported by a substantial data base of good material. The paper discusses some of the proposed changes and contains data on the currently achievable fracture toughness levels.

关键词：海洋平台；钢铁；断裂韧性

查看摘要 索取原文[8页]

The paper is focused on key points and lessons learned from LRFD calibration of simple limit state functions for the internal stability of metallic reinforced soil walls. The example used in the paper is the ultimate pullout limit state for ribbed steel strip reinforced mechanical stabilized earth (MSE) walls and a single load due to soil self-weight plus a permanent surcharge load. The paper demonstrates how load and resistance measurements from instrumented walls and physical pullout tests can be used to generate bias values. Bias statistics are then used to: a) improve the accuracy of underlying deterministic models used to compute nominal load and resistance values; b) remove hidden dependencies; c) select load factors; and, d) calculate resistance factors to meet an acceptable probability of failure. While the paper is focused on the pullout limit state example, the model fitting approach and LRFD calibration methodology is applicable to a wide range of other soil-structure limit state design problems in geotechnical engineering.

关键词：极限状态；阻力系数；钢铁

查看摘要 索取原文[17页]

Gas carburizing is a widely used heat treatment process in which carbon is transferred into steel. The hardening reliability involves an active control of mass transfer during the process and this is why understanding diffusion in solids is so essential to model the process. The currently used models are often based on the simplest, one-dimensional form of the diffusion equation in which diffusivity depends on composition. The objective of this work is to develop a model of carbon diffusion in multicomponent alloy subjected to pulse carburizing. The model is based on the Darken method (bi-velocity method) in which the diffusion velocity depends on the diffusion potential gradient and is independent of the choice of the reference frame while the drift velocity is common for the carbon and steel components. Our model allows predicting the kinetics of carbon transfer at various treatment conditions and is applied to the pulse carburizing process at constant temperature. The process is carried out by repeating consecutively a carburization stage, when the carburizing gas is supplied into a carburizing chamber, and a diffusion stage at vacuum conditions, when the carburizing gas is exhausted and only the diffusion of carbon takes place. The numerical calculations are made for varying carburization and diffusion periods and are confirmed by the experimental results. On the basis of the series of computer experiments some findings that are important in designing the carburizing technology are formulated.

关键词：脉冲渗碳；扩散；双速度法

查看摘要 索取原文[8页]

The flutter stability of the steel truss suspension bridge is hard to reach the requirement of the wind resisting stability when lacks the torsional stiffness.This paper discusses the influence of aerodynamic measure combination,such as central stabilizer,air director enclosed anti-collision bar and so on,towards the flutter stability of steel truss through the wind tunnel experiment of the bridge of Liu Jia gorge.The result shows:the effect of using both the upper and lower stabilized plate is better than separated used it.when sectionalized dispose upper stabilized plate,the flutter critical wind speed of attack angle will decrease rapidly.Outlaying the horizontal guide plate is better than internally installed; The flutter stability of different attack angle tend to be balanced by widening the horizontal guide plate.The anti-collision bar can be functionalized as the central stabilizer by heightening and enclosing,and effectively increase the critical wind speed of different attack angles of the high truss suspension bridge.

关键词：悬索桥；风洞试验；抗风措施；钢铁

查看摘要 索取原文[4页]

A data base of 84 pile load tests was developed for steel pipe piles, driven in clay (small amounts of sand near the surface for a few tests), where there was sufficient data to estimate effective overburden pressures with reasonable accuracy, where soil strengths were well defined, and where a load-settlement curve was available for the load test. Measured pile capacities were compared with values predicted using five methods that have been, are being, or potentially may be used in engineering practice. The two lambda methods had the least scatter but tended to overpredict capacities by about 20%. The current API method had slightly more scatter but overpredicted capacities by only about 13% on the average. The two alpha methods had the largest scatter and the greatest differences between measured and predicted capacities.

关键词：荷载试验；钢铁；负载沉降曲线

查看摘要 索取原文[19页]

In August 2010, Midwest Roadside Safety Facility (MwRSF) developed and crash tested a low-cost, energy-absorbing bridge rail for the Manual for Assessing Safety Hardware (MASH) TL-3 applications. This low-cost bridge rail was designed to be compatible with the Midwest Guardrail System (MGS) such that an approach transition would not be required between the two barriers. It was desired that the system minimize bridge deck and rail costs. As part of this project, several concepts for an energy-absorbing bridge post were developed and tested. These concepts included strong-post systems designed with plastic hinges and weak-post systems designed to bend near the attachment to the bridge deck. The final post concept incorporated S3 OE 5.7 steel sections designed to yield at their bases. These posts were located on 6 ft-3 inches on center. A W-beam section was used as the rail element and was attached to the posts with a bolt designed to break during and impact event. Two full-scale crash tests were performed according to the TL-2 impact conditions provided in MASH. The new bridge rail system successfully met all the safety performance criteria for MASH TL-2. The Texas Type T631 Bridge Rail was developed as a low-cost, energy absorbing bridge rail system for TL-2 applications. Many of the features used for the system tested at Midwest Roadside Safety Facility for TL-3 were incorporated into the design developed for this project for MASH TL-2 application. The TxDOT Type T631 Bridge Rail designed and developed for this project was evaluated under MASH TL-2.

关键词：大桥护栏；碰撞测试；钢铁

查看摘要 索取原文[102页]

Based on node test and finite element analysis results of four different structural form enhanced nodes,failure modes,hysteretic behavior,bearing capacity,ductility and energy dissipation capacity of nodes are analyzed comprehensively and comparatively for more in-depth exploration about the seismic performance of symmetric enhanced nodes.The results showed that all the symmetric enhanced nodes have full hysteretic curve and energy dissipation capacity.On the whole,The flange-plate reinforced node exhibit better seismic performance.

关键词：钢框架；加强节点；循环加载试验；有限元分析

查看摘要 索取原文[5页]

Using a 1984 benchmark experiment, MCNP6 replicated the neutron flux and neutron protection factor (NPF) measurements of an iron box, which simulated a basic military vehicle, resulting in less than 5% difference from the published results. Additionally, the neutron flux spectrum of a 239 PuBe source was characterized using a Bonner Sphere Spectrometer (BSS) and the solution unfolded using the Maximum Entropy Deconvolution (MAXED) program, producing a X2/df of 0.97. Utilizing a steel box provided by the DTRA, measurements of neutron flux from a D-D neutron accelerator were recorded via BSS inside and outside of the box. Both flux spectra were unfolded through MAXED using MCNP6 computations as a priori, which resulted in X2/df values of 0.86 and 0.91, respectively. NPF assessments of the steel box were then conducted using experimental and MCNP6 flux spectra for the box, as well as H*(10) scaling, with final results differing by less than 1%. MAXED software was leveraged for all flux spectrum unfolding, incorporating updated BSS response functions generated within this research from MCNP6. This experiment and its conclusions strongly support the verification and validation of MCNP6 for modeling NPF assessments of military vehicles.

关键词：中子通量；中子保护因子；中子能谱；钢铁

查看摘要 索取原文[104页]

The Universal Breakaway Steel Post (UBSP) was developed and evaluated to replace the existing Controlled Release Terminal (CRT) wood posts which were used in the original bullnose guardrail system. Previously, three full-scale crash tests were performed on the thrie beam bullnose barrier with UBSPs, and the UBSP was determined to be a suitable alternative for the CRT posts. However, the UBSP was modified prior to the completion of the full-scale tests, and dynamic component testing was not conducted to compare the post behaviors. Therefore, a series of nine component tests were conducted in soil to compare the weak- and strong-axis properties between the UBSPs and CRT posts. As part of the component testing, one of the weak-axis tests involving the UBSP was conducted with a reused lower section of the post; since, the original development of the UBSP recommended reuse as long as the lower section was undamaged and displaced less than 12 in. (13 mm). From the testing series, it was determined that the performance of the UBSP indicated a strong potential for these posts to be utilized in other applications. However, UBSP should first be evaluated through engineering analysis and full-scale crash testing before implementation.

关键词：碰撞测试；动态测试；护栏岗位；钢铁

查看摘要 索取原文[109页]