Civil and Environmental Engineering Faculty Publication SeriesCopyright (c) 2016 University of Massachusetts - Amherst All rights reserved.
http://scholarworks.umass.edu/cee_faculty_pubs
Recent documents in Civil and Environmental Engineering Faculty Publication Seriesen-usTue, 08 Nov 2016 19:11:38 PST3600Loss-of-stability induced progressive collapse modes in 3D steel moment frames
http://scholarworks.umass.edu/cee_faculty_pubs/812
http://scholarworks.umass.edu/cee_faculty_pubs/812Wed, 05 Oct 2016 14:11:13 PDT
This paper deals with the progressive collapse analysis of a tall steel frame following the removal of a corner column according to the alternate load path approach. Several analysis techniques are considered (eigenvalue, material nonlinearities, material and geometric nonlinearities), as well as 2D and 3D modelling of the structural system. It is determined that the collapse mechanism is a loss-of-stability-induced one that can be identified by combining a 3D structural model with an analysis involving both material and geometric nonlinearities. The progressive collapse analysis reveals that after the initial removal of a corner column, its two adjacent columns fail from elastic flexural-torsional buckling at a load lower than the design load. The failure of these two columns is immediately followed by the failure of the next two adjacent columns from elastic flexural–torsional buckling. After the failure of these five columns, the entire structure collapseswithout the occurrence of any significant plastification. The main contribution is the identification of buckling-induced collapse mechanisms in steel frames involving sequential buckling of multiple columns. This is a type of failure mechanism that has not received appropriate attention because it practically never occurs in properly designed structures without the accidental loss of a column.
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Gerasimidis, Simos et al.Steel moment frames column loss analysis: The influence of time step size
http://scholarworks.umass.edu/cee_faculty_pubs/811
http://scholarworks.umass.edu/cee_faculty_pubs/811Wed, 05 Oct 2016 14:11:10 PDT
This paper applies two well-known structural dynamics computational algorithms to the problem ofdisproportionate collapse of steel moment frames applying the alternate load path method. Any problem of structural dynamics strongly depends on the accuracy and the reliability of the analysis method since the parameters involved in the selection of the appropriate algorithm are affected by the nature of the problem. Disproportionate collapse is herein simulated via a time history analysis used to ‘‘turn off’’ the effectiveness of an element to the structure. For this kind of problem the time step size of the computational algorithm is of major importance for the accuracy of the method and thus, remains a variable throughout the present analyses. Two plane steel moment frames are used for the numerical examples, while all the analyses are performed independently. Firstly the β-Newmark method is applied and secondly the linear Hilbert–Hughes–Taylor a-method is applied and the respective results are compared and discussed in the last part of the paper.
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Gerasimidis, Simos et al.Evaluation of wind load integration in disproportionate collapse analysis of steel moment frames for column loss
http://scholarworks.umass.edu/cee_faculty_pubs/810
http://scholarworks.umass.edu/cee_faculty_pubs/810Wed, 05 Oct 2016 14:11:08 PDT
The design of steel structures, in most cases, depends majorly on the level of wind loads which are prescribed by codes and regulations and are used in the structural analysis due to the fact that steel structures being light and ductile systems are strongly affected from a slight difference in the values of wind loading. During the last decades, disproportionate collapse analysis has become of major interest mainly due to the increasing number of failures occurring in that pattern. Commonly accepted guidelines and methods of analysis have been produced, the most dominating of which being the Department of Defense Facilities criteria or DoD. In the DoD, as well as in other criteria, the event of a column loss is suggested as modeling scenario which has to be sustained by a structural system in order to be robust. However, all the guidelines so far have disconnected the column loss analysis from wind loads and have only performed it for gravity loading. This paper presents the dynamic time history disproportionate collapse analysis of steel frames, including various levels of wind loading. Interesting aspects are discussed through the parametric analysis of five different numerical examples of moment resisting frames.
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Gerasimidis, Simos et al.Disproportionate Collapse Analysis of Cable-stayed Steel Roofs for Cable Loss
http://scholarworks.umass.edu/cee_faculty_pubs/809
http://scholarworks.umass.edu/cee_faculty_pubs/809Wed, 05 Oct 2016 14:11:06 PDT
Disproportionate collapse has been identified lately as a real cause of failure for structural engineering projects. Rare and unexpected, the phenomenon of disproportionate collapse usually results to many fatalities and thus, its analysis and mitigation is deemed necessary. This work describes the analysis of a cable-stayed steel roof under the scenario of a cable loss. The eventof a cable loss is assumed to be brittle, while relevant recent recommendations suggest the application of a scaled equivalent static force at the points of the anchorage of the cable but in the opposite direction of the original cable force. In this paper, three different conditions have been considered in order to study the effect of the cable loss into the overall structural responseof a typical cable-stayed roof; the level of the equivalent nodal load in the opposite direction of the original cable force varies. The steel structure of the roof, in its complexity, closer to responding as a cable-stayed bridge rather than a steel roof provides a useful template for conclusions; several topics regarding disproportionate collapse and cable losses are discussed.
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Gerasimidis, Simos et al.A computational model for full or partial damage of single or multiple adjacent columns in disproportionate collapse analysis via linear programming
http://scholarworks.umass.edu/cee_faculty_pubs/808
http://scholarworks.umass.edu/cee_faculty_pubs/808Wed, 05 Oct 2016 14:11:03 PDT
The evaluation of the sensitivity or insensitivity of structures to local damage has been a major research field during the last decades, mainly provoked due to the series of aging structures and infrastructures. Many researchers have described this property as redundancy, others as the resistance to disproportionate collapse or robustness and still others as the ability of structural systems to display alternate load paths in case of a local damage. In any case, the problem for the evaluation of this property is increasingly alarming since many systems experience similar collapses (American Society of Civil Engineers (2009). Proceedings of Structures Congress on the first international symposium on disproportionate collapse. ASCE, Austin, TX). This paper presents the numerical assessment of disproportionate collapse analysis introducing the concept of partial damage of structural elements. Global robustness measures are proposed also for the case of multiple partial losses of adjacent elements. The measures are computed on the basis of a mathematical optimization problem using collapse load analysis of steel frames with pre-existing damage. Results comparing the cases of partial losses with the full column lossesare presented and discussed.
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Gerasimidis, Simos et al.A mathematical programming computational model for disproportionate collapse analysis of steel building frames
http://scholarworks.umass.edu/cee_faculty_pubs/807
http://scholarworks.umass.edu/cee_faculty_pubs/807Wed, 05 Oct 2016 14:11:01 PDT
Disproportionate collapse analysis aims to assure that frames, a commonstructural system of buildings, can survive unforeseen local events and a central modelingtool of such abnormal deterioration is the concept of column loss. This paperformulates an appropriate computational model on the basis of mathematical optimization,using the collapse load analysis problem of steel frames with pre-existingdamage. A respective collapse load robustness measure is proposed. The model hasthe ability to consider both full and partial column/node removals. It renders to be alinear programming model, if the US steel design regulations are used. A practicalexample is presented and several aspects are discussed.
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Gerasimidis, Simos et al.When Nanoparticles Meet Biofilms — Interactions Guiding the Environmental Fate and Accumulation of Nanoparticles
http://scholarworks.umass.edu/cee_faculty_pubs/806
http://scholarworks.umass.edu/cee_faculty_pubs/806Fri, 08 Jul 2016 11:40:01 PDT
Bacteria are essential components of all natural and many engineered systems. The most active fractions of bacteria are now recognized to occur as biofilms, where cells are attached and surrounded by a secreted matrix of “sticky” extracellular polymeric substances. Recent investigations have established that significant accumulation of nanoparticles (NPs) occurs in aquatic biofilms. These studies point to the emerging roles of biofilms for influencing partitioning and possibly transformations of NPs in both natural and engineered systems. While attached biofilms are efficient “sponges” for NPs, efforts to elucidate the fundamental mechanisms guiding interactions between NPs and biofilms have just begun. In this mini review, special attention is focused on NP–biofilm interactions within the aquatic environment. We highlight key physical, chemical, and biological processes that affect interactions and accumulation of NPs by bacterial biofilms. We posit that these biofilm processes present the likely possibility for unique biological and chemical transformations of NPs. Ultimately, the environmental fate of NPs is influenced by biofilms, and therefore requires a more in-depth understanding of their fundamental properties.
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Ikuma, Kaoru et al.Measurements of the branching fraction and time-dependent CP asymmetries of B-0 -> J/psi pi(0) decays
http://scholarworks.umass.edu/cee_faculty_pubs/99
http://scholarworks.umass.edu/cee_faculty_pubs/99Fri, 21 Jan 2011 06:57:33 PSTAubert, B et al.Study of the D*(sJ)(2317)(+) and D-sJ(2460)(+) mesons in inclusive cc(-) production near root s=10.6 GeV
http://scholarworks.umass.edu/cee_faculty_pubs/98
http://scholarworks.umass.edu/cee_faculty_pubs/98Fri, 21 Jan 2011 06:50:53 PSTAubert, B et al.Search for the decay B-0 ->(KSKSKL0)-K-0-K-0
http://scholarworks.umass.edu/cee_faculty_pubs/97
http://scholarworks.umass.edu/cee_faculty_pubs/97Fri, 21 Jan 2011 06:44:37 PSTAubert, B et al.