• Title/Summary/Keyword: civil structures

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A Study on the Design Change of High-Risk Temporary Structures (재해 위험도가 높은 가설구조물의 설계변경에 관한 연구)

  • Oh, T.K.;Kim, Y.G.;Lee, M.G.;Paik, S.W.;Woo, I.S.;Song, C.G.
    • Journal of the Korean Society of Safety
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    • v.29 no.1
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    • pp.37-40
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    • 2014
  • Article 29(3) of Occupational Safety And Health Act, which states a contractor can request a design change to an employer of businesses under the risk condition of construction of temporary structure, was established. Accordingly, in this study, recent fatal accidents caused by temporary structures were analyzed, and the level of inclusion of temporary structures in the design document were examined, and high risk temporary structures were classified. In addition, the requirements of design change of temporary structures were presented, and the qualifications of expert to certify the design change were proposed.

Analysis and performance of offshore platforms in hurricanes

  • Kareem, Ahsan;Kijewski, Tracy;Smith, Charles E.
    • Wind and Structures
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    • v.2 no.1
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    • pp.1-23
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    • 1999
  • Wind effects are critical considerations in the design of topside structures, overall structural systems, or both, depending on the water depth and type of offshore platform. The reliable design of these facilities for oil fields in regions of hostile environment can only be assured through better understanding of the environmental load effects and enhanced response prediction capabilities. This paper summarizes the analysis and performance of offshore platforms under extreme wind loads, including the quantification of wind load effects with focus on wind field characteristics, steady and unsteady loads, gust loading factors, application of wind tunnel tests, and the provisions of the American Petroleum Institute Recommended Practice 2A - Working Stress Design (API RP 2A-WSD) for the construction of offshore structures under the action of wind. A survey of the performance of platforms and satellite structures is provided, and failure mechanisms concerning different damage scenarios during Hurricane Andrew are examined. Guidelines and provisions for improving analysis and design of structures are addressed.

Demand response modification factor for the investigation of inelastic response of base isolated structures

  • Cheraghi, Rashid Eddin;Izadifarda, Ramezan Ali
    • Earthquakes and Structures
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    • v.5 no.1
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    • pp.23-48
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    • 2013
  • In this study, the effect of flexibility of superstructures and nonlinear characteristics of LRB (Lead Rubber Bearing) isolator on inelastic response of base isolated structures is investigated. To demonstrate the intensity of damage in superstructures, demand response modification factor without the consideration of damping reduction factor, demand RI, is used and the N2 method is applied to compute this factor. To evaluate the influence of superstructure flexibility on inelastic response of base isolated structures, different steel intermediate moment resisting frames with different heights have been investigated. In lead rubber bearing, the rubber provides flexibility and the lead is the source of damping; variations of aforementioned characteristics are also investigated on inelastic response of superstructures. It is observed that an increase in height of superstructure leads to higher value of demand RI till 4-story frame but afterward this factor remains constant; in other words, an increase in height until 4-story frame causes more damage in the superstructure but after that superstructure's damage is equal to the 4-story frame's. The results demonstrate that the low value of second stiffness (rubber stiffness in LRBs) tends to show a significant decrease in demand RI. Increase in value of characteristic strength (yield strength of the lead in LRBs) leads to decrease in the demand RI.

Performance of bridge structures under heavy goods vehicle impact

  • Zhao, Wuchao;Qian, Jiang;Wang, Juan
    • Computers and Concrete
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    • v.22 no.6
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    • pp.515-525
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    • 2018
  • This paper presents a numerical study on the performance of reinforced concrete (RC) bridge structures subjected to heavy goods vehicle (HGV) collision. The objectives of this study are to investigate the dynamic response and failure modes of different types of bridges under impact loading as well as to give an insight into the simplified methods for modeling bridge structures. For this purpose, detailed finite-element models of HGV and bridges are established and verified against the full-scale collision experiment and a recent traffic accident. An intensive parametric study with the consideration of vehicle weight, vehicle velocity, structural type, simplified methods for modeling bridges is conducted; then the failure mode, impact force, deformation and internal force distribution of the validated bridge models are discussed. It is observed that the structural type has a significant effect on the force-transferring mechanism, failure mode and dynamic response of bridge structures, thus it should be considered in the anti-impact design of bridge structures. The impact force of HGV is mainly determined by the impact weight, impact velocity and contact interface, rather than the simplification of the superstructure. Furthermore, to reduce the modeling and computing cost, it is suggested to utilize the simplified bridge model considering the inertial effect of the superstructure to evaluate the structural impact behavior within a reasonable precision range.

Elastic stiffness of stud connection in composite structures

  • Qin, Xi;Yang, Guotao
    • Steel and Composite Structures
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    • v.39 no.4
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    • pp.419-433
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    • 2021
  • In composite structures, shear connectors are crucial components to resist the relative slip between the steel and concrete, and thereby to achieve the composite actions. In the service stage, composite structures are usually in elastic state, so the elastic stiffness of the shear connection is a quite important parameter in the structural analysis of composite structures. Nevertheless, the existing studies mainly focus on the load-slip relationship rather than the tangent stiffness at the initial elastic stage. Furthermore, when composite beams subjected to torque or local load, shear connections are affected by both tensile force and shear force. However, the stiffness of shear connections under combined effects appears not to have been discussed hitherto. This paper investigates the initial elastic stiffness of stud connections under combined effects of biaxial forces. The initial expression and the relevant parameters are obtained by establishing a simplified analytical model of the stud connection. Afterwards, parametric finite element analysis is performed to investigate the effects of the relevant factors, including the stud length, stud diameter, elastic modulus of concrete, elastic modulus of steel and volume ratio of reinforcement. The feasibility of the proposed modelling has been proved by comparing with sufficient experimental tests. Based on the analytical analysis and the extensive numerical simulations, design equations for predicting the initial elastic stiffness of stud connections are proposed. The comparison between the equations and the data of finite element models demonstrates that the equations are accurate enough to serve for engineering communities.

Assessment of seismic damage inspection and empirical vulnerability probability matrices for masonry structure

  • Li, Si-Qi;Chen, Yong-Sheng;Liu, Hong-Bo;Du, Ke;Chi, Bo
    • Earthquakes and Structures
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    • v.22 no.4
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    • pp.387-399
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    • 2022
  • To study the seismic damage of masonry structures and understand the characteristics of the multi-intensity region, according to the Dujiang weir urbanization of China Wenchuan earthquake, the deterioration of 3991 masonry structures was summarized and statistically analysed. First, the seismic damage of multistory masonry structures in this area was investigated. The primary seismic damage of components was as follows: Damage of walls, openings, joints of longitudinal and transverse walls, windows (lower) walls, and tie columns. Many masonry structures with seismic designs were basically intact. Second, according to the main factors of construction, seismic intensity code levels survey, and influence on the seismic capacity, a vulnerability matrix calculation model was proposed to establish a vulnerability prediction matrix, and a comparative analysis was made based on the empirical seismic damage investigation matrix. The vulnerability prediction matrix was established using the proposed vulnerability matrix calculation model. The fitting relationship between the vulnerability prediction matrix and the actual seismic damage investigation matrix was compared and analysed. The relationship curves of the mean damage index for macrointensity and ground motion parameters were drawn through calculation and analysis, respectively. The numerical analysis was performed based on actual ground motion observation records, and fitting models of PGA, PGV, and MSDI were proposed.

Seismic performance evaluation of steel moment resisting frames with mid-span rigid rocking cores

  • Ali Akbari;Ali Massumi;Mark Grigorian
    • Steel and Composite Structures
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    • v.46 no.5
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    • pp.621-635
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    • 2023
  • The combination of replaceable and repairable properties in structures has introduced new approach called "Low Damage Design Structures". These structural systems are designed in such a way that through self-centering, primary members and specific connections neither suffer damage nor experience permanent deformations after being exposed to severe earthquakes. The purpose of this study is the seismic assessment of steel moment resisting frames with the aid of rigid rocking cores. To this end, three steel moment resisting frames of 4-, 8-, and 12-story buildings with and without rocking cores were developed. The nonlinear static analysis and incremental dynamic analysis were performed by considering the effects of the vertical and horizontal components of 16 strong ground motions, including far-fault and near-fault arrays. The results reveal that rocking systems benefit from better seismic performance and energy dissipation compared to moment resisting frames and thus structures experience a lower level of damage under higher intensity measures. The analyses show that the interstory drift in structures equipped with stiff rocking cores is more uniform in static and dynamic analyses. A uniform interstory drift distribution leads to a uniform distribution of the bending moment and a reduction in the structure's total weight and future maintenance costs.

A new algorithm for design of support structures in additive manufacturing by using topology optimization

  • Haleh Sadat Kazemi;Seyed Mehdi Tavakkoli
    • Structural Engineering and Mechanics
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    • v.86 no.1
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    • pp.93-107
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    • 2023
  • In this paper, a density based topology optimization is proposed for generating of supports required in additive manufacturing to maintain the overhanging regions of main structures during layer by layer fabrication process. For this purpose, isogeometric analysis method is employed to model geometry and structural analysis of main and support structures. In order to model the problem two cases are investigated. In the first case, design domain of supports can easily be separated from the main structure by using distinct isogeometric patches. The second case happens when the main structure itself is optimized by using topology optimization and the supports should be designed in the voids of optimum layout. In this case, in order to avoid boundary identification and re-meshing process for separating design domain of supports from main structure, a parameterization technique is proposed to identify the design domain of supports. To achieve this, two density functions are defined over the entire domain to describe the main structure and supporting areas. On the other hand, since supports are under gravity loads while main structure and its stiffness is not completed during manufacturing process, in the proposed method, stiffness of the main structure is considered to be trivial and the gravity loads are also naturally applied to design support structures. By doing so, the results show reasonable supports are created to protect, continuously, overhanging surfaces of the main structure. Several examples are presented to demonstrate the efficiency of the proposed method and compare the results with literature.

In-Structure Response Spectra of Seismically Isolated Shear Buildings Considering Eccentricity Effect (면진된 전단 거동 구조물의 층응답스펙트럼에 대한 편심효과)

  • Lee, Seung Jae;Kim, Jung Han
    • Journal of the Earthquake Engineering Society of Korea
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    • v.28 no.1
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    • pp.1-10
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    • 2024
  • For important structures such as nuclear power plants, In-Structure Response Spectrum (ISRS) analysis is essential because it evaluates the safety of equipment and components installed in the structure. Because most structures are asymmetric, the response can be affected by eccentricity. In the case of seismically isolated structures, this effect can be greater due to the difference between the center of mass of the structure and the center of rigidity of the isolator layer. Therefore, eccentricity effects must be considered when designing or evaluating the ISRS of seismically isolated structures. This study investigated the change of the ISRS of an isolated structure by assuming accidental eccentricity. The variables that affect the ISRS of the isolated structure were analyzed to see what additional impact they had due to eccentricity. The ISRS of the seismically isolated structure with eccentricity was amplified more than when there was non-eccentricity, and it was boosted more significantly in specific period ranges depending on the isolator's initial stiffness and seismic intensity. Finally, whether the displacement requirement of isolators can be applied to the variation of the ISRS due to eccentricity in the design code was also examined.

Finding the optimum shape of the energy dissipator to minimize the impact force due to the dam break flow

  • Asrini Chrysanti;Sangyoung Son
    • Ocean Systems Engineering
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    • v.14 no.2
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    • pp.157-169
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    • 2024
  • The sudden release of water from a dam failure can trigger bores on a flat surface and exert substantial impact forces on structures. This flow poses a high-risk flood hazard to downstream urban areas, making it imperative to study its impact on structures and devise effective energy dissipators to mitigate its force. In this study, a combination of Genetic Algorithm optimization and numerical modeling is employed to identify the optimal energy dissipator. The analysis reveals that a round arc-shaped structure proves most effective, followed by a triangular shape. These shapes offer wide adaptability in terms of structure dimensions. Structures with higher elevation, especially those with round or triangular shapes, demonstrate superior energy dissipation capabilities. Conversely, square-shaped structures necessitate minimal height to minimize impact forces. The optimal width for dissipating energy is found to be 0.9 meters, allowing for effective wave run-up and propagation. Furthermore, the force exerted on structures increases with higher initial water levels, but diminishes with distance from the dam, highlighting the importance of placement in mitigating impact forces.