AN OPTIMIZATION MODEL FOR PRELIMINARY STABILITY AND CONFIGURATION ANALYSES OF SEMI-SUBMERSIBLES

In the modern era of design governed by economics and efficiency, the preliminary design of a semi-submersible is critically important because in an evolutionary design environment new designs evolve from the basic preliminary designs and the basic dimensions and configurations affect almost all the parameters related to the economics and efficiency (e.g. hydrodynamic response, stability, deck load and structural steel weight of the structure, etc.). The present paper is focused on exploring an optimum design method that aims not only at optimum motion characteristics but also optimum stability, manufacturing and operational efficiency. Our proposed method determines the most preferable optimum principal dimensions of a semi-submersible that satisfies the desired requirements for motion performance and stability at the preliminary stage of design. Our proposed design approach interlinks the mathematical design model with the global optimization techniques and this paper presents the preliminary design approach, the mathematical model of optimization. Finally, a real world design example of a semi-submersible is presented to show the applicability and efficiency of the proposed design optimization model at the preliminary stage of design.

Synthesis of Carbon Fiber Composites and Different Methods to Improve its Mechanical Properties: A Comprehensive Review

Efficient and innovative products can be made using high strength and lighter weight (almost half the steel weight) in modern-day automobile industries. One such material is Carbon Fiber, and it is used as its composites made with the help of epoxy resins. Carbon Fibers applications are increasing in use, in both the aerospace and automobile industries. The corrosion resistance and damping properties of the material can be put to better use in constructions that are heavily strained. The paper aims to review the manufacturing of Carbon fiber composites and their mechanical properties (tensile & flexural strength), which ultimately deals with their applications in the automobile industry. Also, it deals with a review of a few methods or substances used to improve the mechanical properties of carbon fiber composites.

Structural design and experimental tests on a model of tensegrity greenhouse prototype

The aim of this paper is the analysis, proposal and application of a structural tensegrity configuration for greenhouses supporting structures suitable for lightweight covering, based on principles of design coherence, material savings and building durability. By means of the FEM software, Sofistik®, a tensegral greenhouse prototype was modelled and designed in accordance with EN 13031-1:2019. In order to calibrate the results of the FEM analysis, experimental load tests and displacement measurements made with a tensegrity reduced scale model on a tensegrity reduced scale model, created at the Department laboratory of the University of Bari, were compared with the results of the calculation analysis. The displacements of the prototype selected nodes were detected by Target tracking Technology in two load configurations and a control transducer was positioned on the central structural node. The comparison among the displacements of the detected nodes with those resulting from the FEM software calculations, for two different load configurations, show average percentage errors of 7.1% and 12.55%. The results of the T test for the different load configuration point out that the two series of values experimentally detected and calculated by the software are not significantly different. Finally, results in terms of the structural steel weight and maximum stress of the tensegral structure were compared with those of commercial structures, both with vaulted roof and duopitched roof, of single span greenhouses having the same covered ground area of the greenhouse prototype. The proposed tensegrity greenhouse prototype showed a 9.6% and 35.2% reduction of the structural steel weight compared to the vaulted roof and to the duo-pitched roof greenhouse respectively.

Effect of Multispecies Microbial Consortia on Microbially Influenced Corrosion of Carbon Steel

Microbially influenced corrosion (MIC) is responsible for significant damage to major marine infrastructure worldwide. While the microbes responsible for MIC typically exist in the environment in a synergistic combination of different species, the vast majority of laboratory-based MIC experiments are performed with single microbial pure cultures. In this work, marine grade steel was exposed to a single sulfate reducing bacterium (SRB, Desulfovibrio desulfuricans) and various combinations of bacteria (both pure cultures and mixed communities), and the steel corrosion studied. Differences in the microbial biofilm composition and succession, steel weight loss and pitting attack were observed for the various test configurations studied. The sulfate reduction phenotype was successfully shown in half-strength marine broth for both single and mixed communities. The highest corrosion according to steel weight loss and pitting, was recorded in the tests with D. desulfuricans alone when incubated in a nominally aerobic environment. The multispecies microbial consortia yielded lower general corrosion rates compared to D. desulfuricans or for the uninoculated control.

Comparative study on seismic design and check of piers by Chinese and European Codes

<p>The function of bridges would be significantly influenced by the damage of piers during the earthquake, which would affect the rescue and reconstruction after the earthquake. Therefore, it is of great significance to carry out the comparative study on the seismic design and check of piers by the Chinese and European codes. The results show that the seismic design concepts of piers in the Chinese and European codes are the same. The behaviour factor and the seismic importance factor are used to reduce the seismic action in the European code and the Chinese code, respectively. For the check of shear capacity, the contributions of stirrups and concrete are separately considered in the European code, while they are simultaneously considered in the Chinese code. The steel weight of the pier designing by using Chinese codes is lower than that using European codes. The requirement on the minimum transverse reinforcement ratio in the European code is higher than that in the Chinese code.</p>

Current trends in the development of dry cargo carriers for coastal, mixed and inland navigation

Object and purpose of research. This paper discusses characteristics and technical condition of dry cargo ships of limited sea, mixed and inland navigation in order to describe a methodology that allows predicting the composition of the fleet in the medium term. Materials and methods. This study relied on the database of Marine Engineering Bureau (MEB), register books of classification societies, as well as on initial drawings for baseline designs of ships under consideration. The work followed common methods of ship theory and ship design, as well as of naval structural mechanics, analysis and statistics. Main results. A prediction is given for fleet composition and structure until the year 2030, including the ships built after the year 2000, including the newbuilding orders for years 2020–2022. Conclusion. Today, there are about 1,052 dry cargo vessels in operation, 79 % of which are "old", and 21 % were built after the year 2000. Dry-cargo vessels of Volgodonmax class are still the most popular. Due to shallow water depth, these ships cannot be made bigger, so the only way to increase their cargo capacity is to increase their block coefficient and reduce lightship displacement. The first challenge is fully solved by "super-ample" lines currently adopted by MEB for mixed-navigation vessels like RSD59, RSD62, RSD79. As for the reduction of lightship displacement, i.e. steel weight, all the attempts to improve MEB solutions on ships of other designs have so far led to the opposite result, i.e. greater metal consumption and accordingly lower cargo capacity. Thus, it has been practically established that the only way to reduce lightship weight is to apply lighter materials.

Efficiency and Effectiveness Comparative Analysis of Wide Flange Beams and Cellular Beams in A Case Project United Tractor

United Tractors Company will build a sports center building consist of 3 floors using steel structures. Nowadays, limited land is one of the building development problems. The construction of multi-stored buildings is a solution to the limited land problem. The writer has analyzed beam design with a Wide Flange and Cellular system. Focused on the beam element with construction material in the form of steel with steel quality BJ-37, Fy 240 MPa, Fu 370 MPa. The strength and efficiency of the use of steel tonnage were also analyzed. E-Tabs software 2016 used to steel beam structure analysis. In this beam design planning refers to the steel structure planning following SNI 1729: 2015, SNI 1727: 2013, AISC 2010, ASCE 7-10, and also AISC Design Guide 31. The results of manual verification show that the cross-section of WF 400x200x8x13 and CB 250x125x5x8 with a span length of 6 meters is declared to be strong and safe because fill the strong requirements needs to be smaller than the strength of the plan. The efficiency of the use of Cellular Beam was compared to Wide Flange, the longer of Cellular Beam will increase steel tonnage reductions. The percentage reduction in steel weight will continue to increase when the length of steel usage also increases. This concludes that the use of steel length with steel weight reduction will move linearly. Where in this project with a steel beam length of 1439.27m reduction of steel tonnage was at 19.5%.

Material quantity estimation modelling of bridge sub- substructure using regression analysis

In construction field, a time completion and an adherence to budget are two factors that mainly influence the successful of the projects. The adherence to the budget can be achieved when the estimated budget is closed to the actual cost. For the owners, cost estimation is necessary as a guidance in determining the amount of investment. Therefore, it is very important to know the estimation of the project cost by using the limited data before the detailed plans and specifications of the project are identified. However, in the case of bridge substructure preliminary cost estimation, there is a lack information about material quantity estimation models due to the difficulties of soil characteristic and hydrological conditions. Hence, this research aims to develop the estimation of material quantity models of the abutment and caisson of bridge, with the Presetressed Concrete I-Girder (PCI Girder) superstructure located in Sleman district, Yogyakarta province, Indonesia. The database used for developing model was obtained by conducting sub-structure structural analysis of 15 abutments and 45 caissons. The bridges have a various span length, abutment height, and caisson depth. Material quantity estimation models were analysed by the multiple regression analysis methods. The span length and the abutment height are determined as independent variables to predict the concrete volume, the reinforcing steel weight, the caisson concrete volume, the cyclops concrete volume and the caisson reinforcing steel weight. This research proposed 11 equation models to estimate the concrete volume and reinforcing steel weight of abutment and caisson.