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Hao S.,ACII INC.
IOP Conference Series: Materials Science and Engineering | Year: 2014

August 1st of 2007, 6:05PM, the interstate highway I35W Bridge in the City Minneapolis, Minnesota, collapsed suddenly. The 8 traffic-lane, 1000-foot-long deck of the 1907-foot-long bridge fell into Mississippi River within seconds, resulted in 13 fatalities and 145 injuries. This paper is based on a report of a preliminary analysis of this disaster [27], which was submitted to the related administrative agencies at the September of 2007. By comparing the results in that report with the materials' evidences of National Safety Transportation Safety Board (NTSB) official investigation[1,2] and recent in-depth analyses [28,29], it seems that the issues addressed in this earlier analysis may still have certain significance for the safety assessment of those similarly-structured steel bridges today. A bridge's service life is 75 years or longer. According to a NTSB's document [37], there are more than hundreds this kind of bridges still on service [4]. © 2010 IOP Publishing Ltd.


Hu B.,China Communications Construction Company Ltd. | Zhang G.J.,China Communications Construction Company Ltd. | Feng L.P.,China Communications Construction Company Ltd. | Hao S.,ACII INC.
Bridge Maintenance, Safety, Management and Life Extension - Proceedings of the 7th International Conference of Bridge Maintenance, Safety and Management, IABMAS 2014 | Year: 2014

This article introduces a procedure on developing for the fatigue residual life evaluation and associated health monitoring design of the orthotropic steel deck part ofJianghai Navigation Bridge(JNB) of Hongkong-Zhuhai-Macao Bridge (HZMB). This bridge is a 6-span cable stayed structure with two main spans of258m-long each and a continuous steel box girder that stretches over about one kilometer, among the 30 kilometer-long HZMB system. Due to the common fatigue issuesthat have presented in many orthotropic steel bridge decks in services, the structural behavior and its effects on fatigue damage evolution have been investigated, although the bridge is stillat its very beginning stage of design. The analytical results will be used for assistingfuture structural health monitoring program once the bridge is erected. © 2014 Taylor & Francis Group.


Hao S.,ACII INC.
Bridge Structures | Year: 2011

This article discusses issues of structural design revealed by the collapse of I35W Bridge on August 1st, 2007. The article is based on analysis of the original bridge design drawings, a series of detailed finite elements computations, and material evidence disclosed by National Safety Transportation Safety Board (NTSB) official investigation. These issues include (i) redundancy considerations for multi-span bridge; (ii) reason for under-designed bridge elements; (iii) effects of lateral force on gusset plates' load capacity in a steel-truss structure; (iv) criterion of gusset plate's stability and thin-plate theory-based model for load-rating. This analysis concludes that the lessons learned from the I35W Bridge collapse may have certain significance for the safety assessments of similar steel bridges. According to recent surveys, there are scores of this kind of aged bridges that are still in service [38, 41]. © 2011 - IOS Press and the authors. All rights reserved.


A three-dimensional phase field model of anisotropic polycrystalline solids has been developed. In this model the system's free energy is derived in a generalized form based on Ginzburg-Landau's (GL) theory [1], which is a function of lattice's parameters and electron density. A grain boundary in this model is viewed as a discontinuity of periodic atoms array, represented by the Read-Shockley dislocation representation [3]. The Peierls-Nabbaro's dislocation potential [84] has been built into the model to characterize grain boundary's adhesion. Therefore, the model establishes the links between lattice's structure, sub-atomic quantum physics, and the evolutions of grains and grain-boundaries, leading to a meso-scopic constitutive law that governs grains' nucleation, growth, and distortion in a polycrystalline system. This also provides a means to pursue analytical solutions of an alloy's micro-structure's evolution and establishes a framework for corresponding numerical analysis. © 2011 Elsevier B.V. All rights reserved.


Hao S.,ACII INC. | Hao S.,Northwestern University | Lin H.,Dana Canada Corporation | Binomiemi R.R.,Dana Canada Corporation | And 2 more authors.
Computational Materials Science | Year: 2010

It is well-known that atomic-electronic structures determine materials' macro-scale physical properties; however, broad varieties in microstructures and heterogeneities from different scales may significantly amplify or dilute the mechanical behavior of an alloy presented at quantum scale. Hence, breakthrough of computational alloy's design lies in the capabilities to quantitatively and completely integrate key-mechanisms from different scales at each processing step, so as to obtain a unified procedure for establishing quantitative relationships between composition, process, structure, properties, and performance. For this purpose, a multi-scale hierarchical model of intergranular fracture has been developed for polycrystalline systems. As an application example, a carburized steel, which is used for gears and other components in heavy power transmission system, has been analyzed for exploring the ways to improve fracture toughness. As experimental study indicates that the low toughness is often caused by intergranular cracking, this analysis reveals that such a crack initiation can be triggered by the stress concentration at the junctions of grain boundaries when grain boundary adhesion is weak. Therefore, an improved toughness can be achieved by reducing impurities' grain boundary segregation while increasing grains' ductility. © 2010 Elsevier B.V. All rights reserved.

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