Seismic performance and most unfavorable and favorable Load distributions of steel storage rack: an optimization approach

In the current rack seismic design, the load distribution is generally considered to be placed uniformly on the rack, but the reality usually differ. In this paper, the objective is to identify the most unfavorable and favorable load distribution of the braced and unbraced racks under seismic loading through a stochastic optimization - Genetic Algorithm (GA). The GA optimization is performed with an established computational models of racks and the pushover analysis is integrated to evaluate seismic performance of the racks. It is analyzed that the distribution of load has a great influence on the seismic performance of steel racks. During the optimization, including the optimized solutions, there are other loading distributions that will make the racks fail with the seismic requirements. Statistical summary of these load pattern results create a cloud map. The cloud map from the optimization results show that the most unfavorable load distribution is in a ‘凸’ shape of the 3D space of the racks and the safe load distribution holds a ‘凹’ shape for braced racks. Meanwhile, unbracing racks have the characteristics of an unfavorable load distribution of a ‘卩’ shape. The gravity center of the loading has an apparent impact on the braced rack’s seismic performance such as the number of load carried by the columns in the back pulling zone, the total horizontal seismic force, and the distribution of local at the dangerous position. On the other hand, no obvious impact of the gravity.We are grateful to Natural Science Foundation of Jiangsu Province for their financial support(No: BK20191268) to this paper

Onset of Tethered Chain Overcrowding

We proposed an approach to precisely control the density of tethered chains on solid substrates using PEO-b-PS and PLLA-b-PS. As the crystallization temperature T-x increased, the PEO or PLLA lamellar crystal thickness d(L) increased as well as the reduced tethering density (σ) over tilde of the PS chains. The onset of tethered PS chains overcrowding in solution occurs at (σ) over tilde*similar to3.7-3.8 as evidenced by an abrupt change in the slope between (d(L))(-1) and T-x. This results from the extra surface free energy created by the tethered chain that starts to affect the growth barrier of the crystalline blocks

Onset of tethered chain overcrowding

Physical Review Letters, 93(2): pp. 028301-1 -- 028301-4. Retrieved September 19, 2006 from http://www.materials.drexel.edu/SRG/chrisli.html. DOI: http://dx.doi.org/10.1103/PhysRevLett.93.028301We proposed an approach to precisely control the density of tethered chains on solid substrates using PEO-b-PS and PLLA-b-PS. As the crystallization temperature T-x increased, the PEO or PLLA lamellar crystal thickness d(L) increased as well as the reduced tethering density (σ) over tilde of the PS chains. The onset of tethered PS chains overcrowding in solution occurs at (σ) over tilde*similar to3.7-3.8 as evidenced by an abrupt change in the slope between (d(L))(-1) and T-x. This results from the extra surface free energy created by the tethered chain that starts to affect the growth barrier of the crystalline blocks

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Free-Form Shape Optimization of Advanced High-Strength Steel Members

The high yielding strength of advanced high-strength steel (AHSS) provides great opportunities for cold-formed steel (CFS) members with much higher load-carrying capability. However, if manufactured into the traditional cross-section shapes, such as C and Z, the material advantage cannot be fully exploited due to the cross-section instabilities. The purpose of this study was to establish a shape optimization method for cold-formed sections with AHSS and explore the potentially material efficiency that AHSS could provide to these sections in terms of their axial strength. In this study, the insights provided from the elastic buckling analysis and nonlinear finite element (FE) simulations of a set of traditional CFS sections were employed to determine the appropriate section size and length for optimization. Then, the optimization method was established using the particle swarm optimization (PSO) algorithm with the integration of computational analysis through CUFSM and the design approach (i.e., the direct strength method, DSM). The objective function is the maximum axial strength of the CFS sections manufactured with AHSS using the same amount of material (i.e., the same cross-section area). Finally, the optimal sections were simulated and verified by FE analysis, and the characteristics of the optimal cross-sections were analyzed. Overall, the optimization method in this paper achieved good optimization results with greatly improved axial strength capacity from the optimal sections

Free-Form Shape Optimization of Advanced High-Strength Steel Members

The high yielding strength of advanced high-strength steel (AHSS) provides great opportunities for cold-formed steel (CFS) members with much higher load-carrying capability. However, if manufactured into the traditional cross-section shapes, such as C and Z, the material advantage cannot be fully exploited due to the cross-section instabilities. The purpose of this study was to establish a shape optimization method for cold-formed sections with AHSS and explore the potentially material efficiency that AHSS could provide to these sections in terms of their axial strength. In this study, the insights provided from the elastic buckling analysis and nonlinear finite element (FE) simulations of a set of traditional CFS sections were employed to determine the appropriate section size and length for optimization. Then, the optimization method was established using the particle swarm optimization (PSO) algorithm with the integration of computational analysis through CUFSM and the design approach (i.e., the direct strength method, DSM). The objective function is the maximum axial strength of the CFS sections manufactured with AHSS using the same amount of material (i.e., the same cross-section area). Finally, the optimal sections were simulated and verified by FE analysis, and the characteristics of the optimal cross-sections were analyzed. Overall, the optimization method in this paper achieved good optimization results with greatly improved axial strength capacity from the optimal sections

Paleowind Directions over the Tarim Block during the Mesoproterozoic, Northwestern China

The Tarim Block is an ancient plate with a basement of ancient continental crust, which has been separated from the Rodinia supercontinent since the Neoproterozoic. During the Neoproterozoic, which lasted nearly 500 Myr, this block experienced significant evolutionary processes, such as proliferation, radioactive decay of elements, and gradual cooling and solidification. The investigation of Neoproterozoic paleogeography may shed light on the evolution of these geological events. In order to realize this potential, this study aimed to infer paleowind directions over the Tarim Block during each epoch of the Cryogenian–Ediacaran and to constrain the paleogeographic location of the Tarim Block. To this end, outcrop magnetic fabric data were employed to analyze the anisotropy of magnetic susceptibility within the Tarim Block. The anisotropy of magnetic susceptibility measurements yielded mean paleowind directions of 308° ± 69°, 277° ± 78°, and 256° ± 76° from the present north for the Early, Middle, and Late Cryogenian, respectively; the corresponding values for the Early and Late Ediacaran were 237° ± 77° and 254° ± 73° from the present north, respectively. Considering the rotation relationship of the Tarim Block from the Neoproterozoic to the present, the paleowind directions during the Early, Middle, and Late Cryogenian were ~55°, ~35°, and ~35° from the paleo-north, respectively. The paleowind directions during the Early and Late Ediacaran were ~35° and ~60° from paleo-north, respectively. By referring to the correspondence between the paleowind directions over the Tarim Block and trade winds in the Northern Hemisphere, this study provides evidence for the location of the Tarim Block during the Cryogenian–Ediacaran. The main contributions of this study can be summarized as follows: (1) paleowind patterns are established through the analysis of the anisotropy of magnetic susceptibility; (2) the paleogeographic location of the Tarim Block during the Cryogenian–Ediacaran is constrained; and (3) a reference for further study of the paleogeography of the Tarim Block during the Cryogenian–Ediacaran is provided

Seismic performance and most unfavorable and favorable Load distributions of steel storage rack: an optimization approach

In the current rack seismic design, the load distribution is generally considered to be placed uniformly on the rack, but the reality usually differ. In this paper, the objective is to identify the most unfavorable and favorable load distribution of the braced and unbraced racks under seismic loading through a stochastic optimization - Genetic Algorithm (GA). The GA optimization is performed with an established computational models of racks and the pushover analysis is integrated to evaluate seismic performance of the racks. It is analyzed that the distribution of load has a great influence on the seismic performance of steel racks. During the optimization, including the optimized solutions, there are other loading distributions that will make the racks fail with the seismic requirements. Statistical summary of these load pattern results create a cloud map. The cloud map from the optimization results show that the most unfavorable load distribution is in a ‘凸’ shape of the 3D space of the racks and the safe load distribution holds a ‘凹’ shape for braced racks. Meanwhile, unbracing racks have the characteristics of an unfavorable load distribution of a ‘卩’ shape. The gravity center of the loading has an apparent impact on the braced rack’s seismic performance such as the number of load carried by the columns in the back pulling zone, the total horizontal seismic force, and the distribution of local at the dangerous position. On the other hand, no obvious impact of the gravity.We are grateful to Natural Science Foundation of Jiangsu Province for their financial support(No: BK20191268) to this paper

Load Distribution Optimization of Steel Storage Rack Based on Genetic Algorithm

The distribution of load has high uncertainty, which is the main cause of a rack structure’s instabilities. The objective of this study was to identify the most unfavorable and favorable load distributions on steel storage racks with and without bracings under seismic loading through a stochastic optimization—a genetic algorithm (GA). This paper begins with optimizing the most unfavorable and favorable load distributions on the steel storage racks with and without bracings using GA. Based on the optimization results, the failure position and seismic performance influencing factors, such as the load distributions on the racks and at hazardous positions, are then identified. In addition, it is demonstrated that the maximum stress ratio of the uprights under the most unfavorable load distribution is higher than that under the full-load normal design, and it is not the case that the higher the center of gravity the more dangerous the steel storage rack is, demonstrating that the load distribution pattern has a significant impact on the structural safety of steel storage racks. The statistics of the distributions of the load generated during the optimization of the GA and the contours of the probability distributions of the load are generated. Combining the probability distribution contours and the GA’s optimization findings, the “convex” distribution hazard model and the “concave” distribution safety model for a steel storage rack with bracings are identified. In addition, the features of the distribution hazard model and the load distribution safety model are also identified for steel storage racks without bracings