Mechanical Modeling and General Analytical Solution for the Dynamic Buckling of Plane Structures Using a Beam-Column Element with Varying End Restraints

The stability of structures is an important aspect that the designer must pay particular attention to in order to ensure safety against collapse. This investigation is concerned with analytical and numerical analyses of the dynamic buckling of plane structures. A rigorous mechanical model is proposed, consisting of a beam-column element with nodal ends possessing two rotational springs of rigidities acting in parallel with the bending stiffness of the beam-column. The model is first analyzed with respect to the dynamic behavior by investigating the influence of the variation in the stiffness of the nodal springs on the fundamental frequency of the proposed mechanical model. Compression axial loading is applied to the beam-column in order to study the nonlinear dynamic behavior by introducing buckling. This novel approach is used to highlight the interaction between the fundamental frequency and the critical buckling load. Simple examples are treated using the approach and the results are compared with those obtained from a global analysis. The results revealed that it is possible to reproduce the stability analysis of a global structure by simply analyzing a target element, taking into account all elements adjacent to it with less than 1% error on the results.

Mathematical modelling of flow and sediment transport – the Tisa dam case study

High flow velocities downstream of the Tisa Dam at Novi Bečej (Serbia), produced by the large difference between water levels in the upstream and downstream reaches, cause bank erosion by the right bank immediately downstream of the emergency spillway, threatening stability of the dam itself. Due to complex interaction between the parameters of flow and sediment transport at the given location, an approach involving a spatial (3D) mathematical model of flow and sediment transport, aimed at solving such complex processes, is investigated in this paper. An optimum solution meeting all requirements for the stability of structures in question has been reached by the model, through comparison of the results generated by the existing conditions with the result provided by the measures proposed to fix the problems.

Subsurface Topographic Modeling Using Geospatial and Data Driven Algorithm

Infrastructures play an important role in urbanization and economic activities but are vulnerable. Due to unavailability of accurate subsurface infrastructure maps, ensuring the sustainability and resilience often are poorly recognized. In the current paper a 3D topographical predictive model using distributed geospatial data incorporated with evolutionary gene expression programming (GEP) was developed and applied on a concrete-face rockfill dam (CFRD) in Guilan province- northern to generate spatial variation of the subsurface bedrock topography. The compared proficiency of the GEP model with geostatistical ordinary kriging (OK) using different analytical indexes showed 82.53% accuracy performance and 9.61% improvement in precisely labeled data. The achievements imply that the retrieved GEP model efficiently can provide accurate enough prediction and consequently meliorate the visualization insights linking the natural and engineering concerns. Accordingly, the generated subsurface bedrock model dedicates great information on stability of structures and hydrogeological properties, thus adopting appropriate foundations.

Secondary Structure Prediction for RNA Sequences Including N6-methyladenosine

There is increasing interest in the roles played by covalently modified nucleotides in mRNAs and non-coding RNAs. New high-throughput sequencing technologies localize these modifications to exact nucleotide positions. There has been, however, and inability to account for these modifications in secondary structure prediction because of a lack of software tools for handling modifications and a lack of thermodynamic parameters for modifications. Here, we report that we solved these issues for N6-methyladenosine (m6A), for the first time allowing secondary structure prediction for a nucleotide alphabet of A, C, G, U, and m6A. We revised the RNAstructure software package to work with any user-defined alphabet of nucleotides. We also developed a set of nearest neighbor parameters for helices and loops containing m6A, using a set of 45 optical melting experiments. Interestingly, N6-methylation decreases the folding stability of structures with adenosines in the middle of a helix, has little effect on the folding stability of adenosines at the ends of helices, and stabilizes the folding stability for structures with unpaired adenosines stacked on the end of a helix. The parameters were tested against an additional two melting experiments, including a consensus sequence for methylation and an m6A dangling end. The utility of the new software was tested using predictions of the structure of a molecular switch in the MALAT1 lncRNA, for which a conformation change is triggered by methylation. Additionally, human transcriptome-wide calculations for the effect of N6-methylation on the probability of an adenosine being buried in a helix compare favorably with PARS structure mapping data. Now users of RNAstructure are able to develop hypothesis for structure-function relationships for RNAs with m6A, including conformational switching triggered by methylation.

Seismic Retrofitting of Structures Using Steel Bracing: An Overview

One of the major causes of the collapse of buildings are earthquakes. Reinforced concrete structures are vulnerable to seismic activities and can destruct the structures. The RC structures which are prone to seismic activities should be protected and need to be retrofitted to resist the seismic loads. Retrofitting is one of the best methods which can be used to strengthen the structures safe against seismic loads. Retrofitting techniques will increase the strength, stiffness, ductility and stability of structures as well as reduce the operation costs and environmental impacts. Various techniques of retrofitting can be adapted to improve the stability of the structure. One of the most effective method for retrofitting of structures is the use of steel bracings. Steel bracing can be effectively used for enhancing the earthquake resistance of seismically inadequate reinforced concrete frames. This paper reviews the effect of different steel bracing patterns used as retrofitting technique in the seismic performance of the structures.

Deep deformations of the upper stream of a low-pressure reservoir

The article presents the results of the analysis of the deep deformations of the Amu Darya riverbed in the upper reaches of the low-pressure reservoir. The analysis of the combined transverse profiles of the riverbed in different sections of the upper reaches of the Takhiatash reservoir showed that the coastal zones are most intensively silted up. At the same time, the core zone with the highest flow rates is very weakly declared. The height of the silting layer along the length of the upper stream increases in the direction of the dam. The silting area extends upstream for a length 2-3 times longer than the length of the soundings section, which is 17.5 km. To ensure the normal operation of the hydraulic system, it is recommended that conditions should be created for a normal and stable approach of the flow to the hydraulic system, which should be ensured by maneuvering the shield holes. To do this, it is necessary to create conditions for the erosion of the left-bank spillway by increasing the water flow through the extreme left-bank discharge holes. Flushing of the upper left-bank section of the river should continue until the optimal width of the leading channel is reached, which provides the main flow of the stream in front of the structure. It is proved that the formation and development of sediment deposits on the right bank between sections 8-10 leads to a change in the flow correction and creates conditions for the formation of shoals in front of the regulator of the Kizketken channel, which can complicate the operation of the water intake zone. Therefore, it is necessary to take measures to prevent the development of the right-bank channel, and the development of the channel should go from the main channel. As shown by monitoring operating mode Takhiatash waterworks, in the Takhiatash district waterworks intensive processes the channel formation, which has a strong influence on the operational mode of the dam, especially in the operation of the water intakes flushing of sediments, skip flood costs through the shields of the dam and the stability of structures.

A Novel Design for a Compliant Mechanism Based Variable Stiffness Grasper Through Structure Modulation

Robots utilize graspers for interacting with an environment. Conventional robot graspers are composed of rigid links and are dedicated to perform a particular task. However, such graspers have difficulty conforming to objects of varied shape and exerting varying grasping forces. Soft robotic graspers provide these features through different modalities. However, such modalities that vary the stiffness of soft robotic graspers face issues such as slow response time, requirement of external power packs for operation and low variation of stiffness. A variable stiffness compliant robotic grasper that is simple in design and operation would improve end effectors used in assistive robotics and prostheses where ability to vary stiffness would benefit in handling a wide array of objects. This research presents a novel method of achieving variable stiffness through structural transformations. Current designs utilizing structural transformations do not provide shape conformance while grasping objects. We propose a design for a soft robotic grasper utilizing the concept of stability of structures. This design is capable of adapting to the surface of an object being grasped and can rapidly vary its stiffness. The grasper behavior is modelled using Finite Element Analysis and validated experimentally. Our results demonstrate that structural transformation of flexible elements is a potential solution for achieving variable stiffness in a grasper.

DETERMINATION OF LOAD-BEARING STRUCTURE'S MAXIMUM LOAD ONTO FOUNDATION GROUND FOR THE CRNA RIJEKA SMALL POWER PLANT

The paper presents the determination of the maximum load of load-bearing structures with terrain contact according to EN 1997-1 (Geotechnical design) and EN 1998-5 (Foundations, supporting structures and geotechnical issues). Processed is a concrete example of SPP Crna rijeka which will be based in rock material, and which does not require “additional“ interventions for the stability of structures (water intake with sedimentation tank and engine room).

Multiple Twisted Chiral Nematic Structures in Cylindrical Confinement

In this article, we theoretically and numerically study the chirality and saddle-splay elastic constant ( K 24 ) -enabled stability of multiple twist-like nematic liquid crystal (LC) structures in cylindrical confinement. We focus on the so-called radially z-twisted (RZT) and radially twisted (RT) configurations, which simultaneously exhibit twists in different spatial directions. We express the free energies of the structures in terms of dimensionless wave vectors, which characterise the structures and play the roles of order parameters. The impact of different confinement anchoring conditions is explored. A simple Landau-type analysis provides an insight into how different model parameters influence the stability of structures. We determine conditions for which the structures are stable in chiral and also nonchiral LCs. In particular, we find that the RZT structure could exhibit macroscopic chirality inversion upon varying the relevant parameters. This phenomenon could be exploited for the measurement of K 24 .