This paper uses structural optimization techniques to cost-effectively design seismic steel moment frames with enhanced resistance to progressive collapse, which is triggered by the sudden removal of critical columns. The potential for progressive collapse is assessed using the alternate path method with each of the three analysis procedures (i.e., linear static, nonlinear static, and nonlinear dynamic), as provided in the United States Department of Defense United Facilities Criteria (UFC) Design of Buildings to Resist Progressive Collapse. As a numerical example, member sizes of a two-dimensional, nine-story, threebay regular steel immediate moment frame are optimally determined such that the total steel weight is minimized while the design satisfies both AISC seismic provisions and UFC progressive collapse requirements. Optimization results for the example frame reveal that the traditional minimum weight seismic design, which does not explicitly consider progressive collapse, fails to meet the UFC alternate path criteria associated with any analysis procedure. Progressive collapse design optimization using the linear static procedure produces the most conservative and consequently heaviest design against progressive collapse. In contrast, the more accurate nonlinear static and dynamic procedures lead to more economical designs with UFC-acceptable resistance to progressive collapse, at the expenses of considerable modeling and computing efforts.
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Optimum design of steel frames using a multiple-deme GA with improved reproduction operators
Author: D. Safari, Mahmoud R. Maheri, A. Maheri | Size: 1.8 MB | Format:PDF | Quality:Unspecified | Publisher: Elsevier | Year: 2011 | pages: 12 | ISBN: --
In this paper, the performance of the genetic algorithm is improved by introducing some new crossover and mutation operators. The new operators are incorporated into a multiple-deme genetic algorithm in which population is divided into subpopulations and communication between different demes is established through migration of individuals, enhancing diversity and resulting in better solutions. This algorithm is applied to the minimum weight design of steel frames subjected to actual strength and ductility constraints of AISC–ASD specifications as well as other serviceability and constructability constraints. The efficiency of the proposed method is demonstrated through optimising two benchmark problems including a three-bay, three-storey steel frame and a five-bay, 22-storey special steel frame. Significant improvements in the optimum solutions are obtained with reduced number of finite element analyses, resulting in less computational effort.
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The microtremor spectral ratio proposed by Nakamura (A method for dynamic characteristics estimation of subsurface using microtremor on ground surface. QR of RTRI, 1989, 30(1), 25–33.) developed a new interest on the use of microtremor measurements for the estimation of site effects. The Lisbon region is an earthquake-prone area and several descriptions of destructive earthquakes are reported in the historical data, which suggest the existence of site effects in the town of Lisbon. Several seismic hazard studies were already performed, as well as some microzonation studies based on records from blasts. In order to characterize the seismic behaviour of alluvium layers existing in the town, two sets of microtremor measurements were performed. The data were processed according to the Nakamura technique and the results are presented here. These results were correlated with the thickness of the alluvium deposits and compared with the spectral ratios obtained using records from blasts, as well as with 1D theoretical models and with 2D theoretical simulations obtained by the use of the Aki-Larner technique. These comparisons seem to prove that the use of microtremor measurements could give a good contribution for the microzonation techniques, specially in urban zones, due to the simplicity and rapidity of their acquisition.
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At the convention you will have the opportunity to participate in the development of industry codes and standards; network with many of the world’s leading concrete professionals; and learn about the latest in concrete technology while fulfilling your continuing education requirements.
The links are for the handouts (mostly pdf version of some presentations) that can help introduce the readers to most recent research trends and pressing issues on concrete.
PS: The link to the original site and presentation links do expire after a while.
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Article/eBook Full Name: Constitutive Modeling of Geomaterials: Advances and New Applications
Author(s): Qiang Yang, Jian-Min Zhang, Hong Zheng, Yangping Yao
Edition: 1
Publish Date: 2013
ISBN: 364232813X
Published By: Springer
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EN 1097-1:2011 Tests for mechanical and physical properties of aggregates - Part 1: Determination of the resistance to wear (micro-Deval)
Size: 0.12 MB
Format: PDF
Quality: Scanner
Publisher: CEN
Year: 2011
Pages: 14
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This session gives a technical background on the modeling and analysis of masonry structures in DIANA.
A case study for nonlinear modelling of a masonry infilled reinforced concrete frame which was tested experimentally will be presented. This presentation includes:
Description of the specimen
Calibration and validation of the material parameters
Modelling of the infilled frame
Pushover analysis
Comparison of the numerical and experimental results
A classical case-study of a masonry wall with opening will be presented to demonstrate DIANA capabilities for modeling and predicting failure mechanisms of masonry structures.
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A comparison of geostatistical procedures for spatial analysis of precipitation in mountainous terrain
Author: Donald L Phillips; Jayne Dolph; Danny Marks | Size: 1.3 MB | Format:PDF | Quality:Unspecified | Publisher: Elsevier | Year: 1992 | pages: 22 | ISBN: --
Spatially distributed measurements or estimates of precipitation over a region are required for modelling of hydrologic processes and soil moisture for agricultural and natural resource management. Simple interpolation methods fail to consider the effects of topography on precipitation and may be in considerable error in mountainous regions. The performance of three geostatistical methods for making mean annual precipitation estimates on a regular grid of points in mountainous terrain was evaluated. The methods were: ( 1 ) kriging; (2) kriging elevation-detrended data; and (3) cokriging with elevation as an auxiliary variable. The study area was the Willamette River basin, a 2.9 million hectare region spanning the area between the Coast Range and the Cascade Range in western Oregon. Compared with kriging, detrended kriging and cokriging both exhibited better precision (as indicated by estimation coefficients of variation of 16 and 17% vs. 21%; and average absolute errors of 19 and 20 cm vs. 26 cm) and accuracy (as indicated by average errors of - 1.4 and -2.0 cm vs. -5.2 cm) in the estimation of mean annual precipitation. Contour diagrams for kriging and detrended kriging exhibited smooth zonation following general elevation trends, while cokriging showed a patchier pattern more closely corresponding to local topographic features. Detrended kriging and cokriging offer improved spatially distributed precipitation estimates in mountainous terrain on the scale of a few million hectares. Application of these methods for a larger region, the Columbia River drainage in the USA (57 million hectares), was unsuccessful due to the lack of a consistent precipitation-elevation relationship at this scale, Precipitation estimation incorporating the effects of topography at larger scales will require either piecewise estimation using the methods described here or development of a physically based orographic model.
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I'll be very thankful if someone of you is able to provide the standard "EN 1097-1:2011 Tests for mechanical and physical properties of aggregates. Determination of the resistance to wear (micro-Deval)".
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