A Novel Incremental Iterative Force Recovery Method for Second-Order Beam-Column Elements in Plastic Hinge Analysis of Steel Frames

This paper is concerned with an incremental iterative force recovery method in the second-order plastic hinge analysis of steel frames mainly modelled by a single element per member. Second-order beam-column elements are preferred in the direct analysis of steel frames due to their high accuracy and efficiency. However, formulations of these elements are complicated, and therefore they may have a problem of getting element force recovery in inelastic analysis. To overcome this difficulty, a novel incremental iterative force recovery method for second-order beam-column elements is proposed to perform plastic hinge analysis. The proposed method is derived more strictly and has good performance. Also, the section assemblage approach and the refined plastic hinge method are adopted in this study to consider the gradual degradation of section stiffness in the plastic hinge analysis. To verify the accuracy, efficiency and robustness of the proposed method, several benchmark examples are analyzed by the proposed method and compared with solutions reported by early researchers.

Analysis Of The Effect Of Bending Strength On Scaffolding System With Direct Analysis Method

Steel scaffolding is a very important component in formwork work to support further work. The purpose of this analysis is to review the maximum compressive strength that occurs in 3-story scaffolding before buckling occurs using the direct analysis method (DAM). The design of steel structures, which are generally slender, requires stability analysis. The result is influenced by imperfections (non-linear geometry) and inelastic conditions (non-linear material). In this final project, we use second-order inelastic analysis based on direct analysis method. The 3-level scaffolding model was analyzed using beam elements in the SAP2000 program with 6 variations of notional loads applied to the weak axis direction of the scaffolding pipe.The lowest compressive strength on 3-story scaffolding before buckling occurs is 18.24 kN with horizontal notional loads to the right on the first level scaffolding, left on the second level scaffolding and to the right on the 3rd level scaffolding. The results of the analysis show that the maximum compressive strength obtained results in a large displacement drastically in the iteration step. By using the analysis on the DAM method, the results obtained are more effective.

Application of Inelastic Method and Its Comparison with Elastic Method for the Assessment of In-Box LOCA Event on EU DEMO HCPB Breeding Blanket Cap Region

The Helium Cooled Pebble Bed (HCPB) breeding blanket, being developed by the Karlsruhe Institute of Technology (KIT) and its partners is one of the two driver blanket candidates to be selected for the European demonstration fusion power plant (EU DEMO). The in-box Loss of Coolant Accident (LOCA) is a postulated initiating event of the breeding blanket (BB) that must be accounted within the design basis. In this paper, the BB cap region is analyzed for its ability to withstand an in-box LOCA event. Initially, an assessment is performed using conventional elastic design codes for nuclear pressure vessels. However, it is thought that the elastic rules are not ‘equipped’ to assess the material damage modes which are essentially inelastic. Therefore, a non-linear inelastic analysis is further performed to better understand the damage in the material. Two predominant inelastic failure modes are thought to be relevant and addressed: exhaustion of ductility and plastic flow localization. While the design of HCPB BB has been predominantly based on the elastic design-by-analysis studies, results from the present study show that the elastic rules may be overly conservative for the given material and loading and could lead to inefficient designs. To our knowledge, this study is the first attempt to investigate the structural integrity of the European DEMO blankets under in-box LOCA conditions using the inelastic methods.

Rao algorithm-based method for optimisation of steel frames using nonlinear inelastic analysis

Metaheuristic optimisation algorithms have been increasingly used because of their superior ability to find globally optimal solutions. Theoretically, these algorithms are very powerful and can be applied in all types of optimisation problems. However, in reality, their performance depends on the characteristics of each optimisation problem class. In addition, the complexity of an algorithm is an important factor affecting its application in specific design problems. In this paper, the Rao optimisation algorithm, one of the newest metaheuristic algorithms, is presented for the optimisation algorithm of steel frame structures. The advantage of the Rao algorithm is that it is quite simple with few parameters, so engineers can easily apply it in daily design tasks. A nonlinear inelastic analysis is used to consider the nonlinear behaviors of the steel structure. A two-story space steel frame is studied. The results show that Rao-1 is more stable and converged more quickly but easily trapped in local solutions than Rao-2 and Rao-4. Rao-4 is more efficient in global search but its stability is less than other algorithms. Keywords:nonlinear inelastic analysis, optimisation, Rao algorithm, steel frame.

A Viscoplastic Model for Alloy 617 for Use With the ASME Section III, Division 5 Design by Inelastic Analysis Rules

The rules for the design of high temperature reactor components in Section III, Division 5, Subsection HB, Subpart B (HBB) of the ASME Boiler and Pressure Vessel Code contain two options for evaluating the deformation-controlled design limits on strain accumulation and creep-fatigue: design by elastic analysis and design by inelastic analysis. Of these options design by inelastic analysis tends to be less overconservative and produce more efficient designs. However, the HBB currently does not provide approved material models for use with the inelastic analysis rules, limiting their widespread use. A nonmandatory appendix has been developed to provide general guidance on appropriate material models and provide reference material models suitable for use with the design by inelastic analysis approach. This paper describes a viscoplastic model for Alloy 617 suitable for use with the HBB rules proposed for incorporation into the new appendix. The model represents the high temperature creep, creep-fatigue, and tensile response of Alloy 617 and accurately accounts for rate sensitivity across a wide range of temperatures. The focus in developing the model was on capturing key features of material deformation required for accurately executing the HBB rules and on developing a relatively simple model form that can be implemented in commercial finite element analysis software. The paper validates the model against an extensive experimental database collected as part of the Alloy 617 Code qualification effort as well as against specialized experimental tests examining the effect of elastic follow up on stress relaxation and creep deformation in the material.

Performance comparison of metaheuristic algorithms for optimisation of steel framesusing nonlinear inelastic analysis

Ngày nay, thiết kế tối ưu công trình sử dụng thuật toán metaheuristic được sử dụng một cách thường xuyên hơn nhờ hiệu quả vượt trội của các thuật toán tối ưu này trong việc giải quyết các bài toán có độ phức tạp cao. Nhờ những ưu điểm đó, có khá nhiều thuật toán tối ưu đã và đang được đề xuất. Tuy nhiên, tùy thuộc vào đặc điểm của từng dạng bài toán tối ưu khác nhau mà hiệu quả của thuật toán sẽ khác nhau. Trong bài báo này, bài toán tối ưu của khung thép sử dụng phân tích phi tuyến đã được xem xét. Bốn thuật toán tối ưu sử dụng phổ biến gần đây cho dạng bài toán này được xem xét so sánh bao gồm: bản nâng cấp thuật toán tiến hóa vi phân (EpDE), bản nâng cấp thuật toán tối ưu va chạm giữa các vật chất (ECBO), kỹ thuật tìm kiếm hài hòa (HS) và thuật toán Rao. Một khung thép phẳng 5 tầng được tối ưu với hàm mục tiêu là tổng khối lượng và điều kiện ràng buộc cả về khả năng chịu tải và về chuyển vị lệch tầng. Kết quả tính toán cho thấy, thuật toán EpDE không chỉ tìm kiếm được kết quả tối ưu tốt nhất mà tốc độ tối ưu cũng tốt nhất trong bốn thuật toán.