The influence of structural imperfections on the LTB strength of I-beams

© 2020 World Scientific Publishing Company. Structural steel frames exhibit significantly geometric and material nonlinearities which can be captured using the second-order inelastic analysis, also known as advanced analysis. Current specifications of most modern steel design codes, e.g. American code AISC360, European code EC3, Chinese code GB50017 and Australian code AS4100 permit the use of advanced analysis methods for the direct design of steel structures to avoid tedious member capacity checks. In the past three decades, a huge number of advanced analysis and modeling methods have been developed to predict the behavior of steel and composite frames. This paper presents a comprehensive review of their developments, which focus on beam-column elements with close attention to the way to capture geometric and material nonlinearity effects. A brief outline of analysis methods and analysis tools for frames was presented in the initial part of the paper. This was followed by a discussion on the development of displacement-based, force-based and mixed beam elements with distributed plasticity and concentrated plasticity models. The modeling of frames subjected to fire and explosion was also discussed. Finally, a review of the beam-column models for composite structures including concrete-filled steel tubular (CFST) columns, composite beams and composite frames was presented.

Review of Nonlinear Analysis and Modeling of Steel and Composite Structures

Park, Y.H.; Oh, Y.-M.; Ahn, S.M.; Han, T.H.; Kim, Y.-T.; Suh, K.-D., and Won, D., 2019. Development of a new concrete armor unit for high waves. Journal of Coastal Research, 35(3), 719–728...

Development of a New Concrete Armor Unit for High Waves

The invention relates to an assembly type prestress reactive powder concrete wind power tower. The assembly type prestress reactive powder concrete wind power tower comprises a foundation and a plurality of sections of tower barrels, the foundation is made of concrete, and foundation rings are buried in the foundation in advance. The tower barrels are machined by reactive powder concrete, a plurality of preformed holes are formed inside each section of tower barrel in the prefabricating process, and prestressed reinforcements penetrate through the preformed holes; the upper ends of the prestressed reinforcements are anchored on the upper end faces of the tower barrels after the prestressed reinforcements are tensioned, and the lower ends of the prestressed reinforcements are connected with the foundation rings in an anchoring mode. Tension prestress is segmented on the scene, and construction is easy to conduct. The assembly type prestress reactive powder concrete wind power tower is reasonable in structure, convenient to transport and assemble and low in manufacturing cost and use and maintenance cost, stability of the tower after the tower is stressed can be effectively enhanced through the prestressed reinforcements arranged inside the tower, concrete on the surfaces of the tower barrels is prevented from cracking, and the service life of the tower is prolonged.

Assembly type prestress reactive powder concrete wind power tower

지구온난화와 같은 환경문제와 교토의정서에 따른 탄소배 출권의 문제 등에 따른 영향으로 태양광, 풍력, 조력 등과 같 은 신재생 에너지에 대한 개발을 위한 노력이 활발히 이루어 지고 있다. 그중에서도 풍력에너지의 발전효율이 높은 것으로 나타나 연구가 활발히 진행되고 있으며, 특히 최근에는 대용 량 터빈의 설치가 가능하고, 민원의 발생을 최소화할 수 있는 해상풍력에 대한 관심이 높아지고 있다. WWEA(World Wind Energy Association)의 발표에 의하면 2015년 현재 각국에 설치된 풍력발전 용량은 약 390GW이며, 2014년 새로 설치된 풍력발전기의 용량은 대략 50GW이다. 이러한 증가량은 전년인 2013년 같은 시기에 비해 40%의 성 장률을 보인 것이다. 풍력발전의 성장속도는 2009년을 시작 으로 해마다 오르고 있으며, 2013년 12.8%에 비해 2014년에 는 16%로 빠르게 증가하고 있다(WWEA, 2015). 해상풍력의 경우, 육상에서의 발전시설에 비해 바람의 품질 이 우수하고, 건설에 대한 지리적 제약조건과 풍력터빈의 운 송 및 설치에 대한 제약이 적은 편이다(Roland Berger, 2013). 유럽의 경우, 2015년 중반 새로운 해상풍력발전의 설치 용량 Abstract

Section Design of Internally Confined Hollow Reinforced Concrete Wind Power Tower

In recent years, there has been a growing demand for renewable energy that is free of power generation by products to address the global climate and resource limitation crises. Wind power generation is maximizing efficiency through constant research and development, and as the use of large capacity turbines increases, the scale of supporting structure also increases. The structural maintenance of hollow towers, the supporting structure of wind turbines, requires the installation of an opening through which workers can access the tower to check corrosion, cracks, and damage to the tower body. However, these access points can affect the buckling strength of the tower structures due to section loss. In this study, the effects of the opening on the structural stability and ultimate strength of a large diameter cylindrical shell, which could be used as a wind turbine supporting tower structure, were studied through elastic buckling and nonlinear analyses. Based on the analytical results, the effects of the thickness of a collar stiffener around the opening on the structure’s ultimate strength were investigated. The results were compared to the design criteria, and through regression analysis, an effective equation to determine the collar stiffener’s thickness for large diameter cylindrical shells was proposed based on an opening that satisfied the design strength criteria.

Structural Behavior of Large-Diameter Cylindrical Shell with Stiffened Opening

Recently, there is to increase interest in seismic performance of piers. Hollow section is applied to increasing the seismic performance of piers. However, hollow RC pier becomes the biaixial confining state because hollow part is not confined. The pier is developed brittle failure from inner face in hollow part. A tube is inserted in hollow part to become the weakness. This is ICH RC(Internally Confined Hollow RC) pier. This pier is enhanced stiffness, strength, and ductility by core concrete has triaxial confining stress. In this paper is researched about parameters effect the seismic performance. Parameters are hollow ratio, transverse reinforcement, longitudinal reinforcement, and concrete strength.

http://www.ndsl.kr/soc_img/society/kosacs/BHSSCI/2012/v3n2/BHSSCI_2012_v3n2_28.pdf

A Parametric Study on Seismic Performance of Internally Confined Hollow RC Columns

Recently, a great progress has been made in bridge construction technology through the development of high performance materials and new structural types. However, most of attention has been paid to the cast-in-place technologies and material cost saving. The cast-in-place method is always subject to some environmental damages in construction sites, which frequently causes conflicts with residents. To overcome the disadvantages, a lot of fabrication construction method was developed. Most fabrication construction methods developed up to now have been applied for superstructure of bridges. In contrast, such fabricable methods developed for substructures are extremely rare. A fabricated column using ICH CFT(Internally Confined Hollow CFT) column was developed in a series of previous researches. Included in the previous studies are design and construction methods for the precast segmental coping, the column-coping connection, the column-segment connection, column-foundation connection. In this paper, seismic performance of the fabricated ICH CFT columns was extensively investigated experimentally. Two test specimens were prepared depending on the connection methods of segments; one by mortar-grouting method and the other by reinforcement method using stiffeners.

Seismic Performance of Fabricated Internally Confined Hollow CFT Column

This paper presents an equation for the effective tangent moduli for steel axial members of hot-rolled I-shaped section subjected to various residual stress distributions. Because of the existence of residual stresses, the cross section yields gradually even when the member is subjected to uniform axial stresses. In the elasto-plastic stage, the structural response can be easily traced using rational tangent modulus of the member. In this study, the equations for rational tangent moduli for hot-rolled I-shaped steel members in the elasto-plastic stage were derived based on the general principle of force-equilibrium. For practical purpose, the equations for the tangent modulus were presented for conventional patterns of the residual stress distribution of hot-rolled I-shaped steel members. Through a series of material nonlinear analyses for steel axial members modeled by shell elements, the derived equations were numerically verified, and the presented equations were compared with the CRC tangent modulus equation, the most frequently used equation so far. The comparative study shows that the presented equations are extremely effective for accurately analyzing elasto-plastic behavior of the axially loaded members in a simple manner without using complex shell element models.

Tangent moduli of hot-rolled I-shaped axial members considering various residual stress distributions

Structural Behavior Analysis of DSCT Wind Power Tower for 5MW Turbines Considering Large Displacement Effect

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