Environmental Load Factors for Offshore Structures

1999 ◽  
Vol 121 (4) ◽  
pp. 261-267
Author(s):  
H. P. Hong ◽  
M. A. Nessim ◽  
I. J. Jordaan
Keyword(s):  
Model Uncertainty ◽  
Offshore Structures ◽  
Specific Model ◽  
Load Factor ◽  
Environmental Load ◽  
Load Effect ◽  
Environmental Loads ◽  
Load Factors ◽  
Environmental Process ◽  
The Impact

An analysis of the impact of model uncertainties on the design factors for environmental loads on offshore structures was carried out. Considering uncertainties in environmental processes, the load effect models and the member resistance, an approach was developed that gives explicit consideration to model uncertainty in codified design. For frequent environmental load effects, a two-factor approach was developed that defines the overall load factor as the product of two components: a basic factor accounting for uncertainty in the environmental process and a separate factor accounting for model uncertainty. The overall load factor is to be applied to the specified load, which is defined as the load corresponding to the environmental process value associated with a specified return period. This load can be calculated from the environmental process without considering model uncertainty. The model uncertainty factor was defined as a linear function of the mean and the standard deviation of the model uncertainty parameter. It can be estimated based on a specific model and reliability analysis. This two-factor approach has two advantages: (a) it allows for reductions in the load factor if conservative or more accurate models are used; and (b) it eliminates the need for the designer to consider model uncertainty in estimating the specified load. The approach was used to develop a set of load factors for environmental loads on offshore structures. These factors were calibrated to produce reliability levels consistent with those implied by the load factors in CSA-S471.

The Impact of Multi-Body Operations on DP Capability

2015 ◽  
Author(s):  
Yann Giorgiutti ◽  
Flávia C. Rezende ◽  
Julien Boulland ◽  
Rodrigo Araujo
Keyword(s):  
Wind Wave ◽  
Environmental Load ◽  
Design Phase ◽  
Environmental Loads ◽  
Industry Standards ◽  
The World ◽  
Wave Trains ◽  
Multi Body ◽  
The Impact ◽  
Offshore Activities

As offshore activities are growing, the marine operations are becoming more complex involving the presence of few or several vessels in proximity to each other which increases the risk associated to those operations. Shuttle tankers, PSVs, floatels are often equipped with DP systems for maintaining position. The capability of these systems is defined during design phase by the DP manufacturer based on the assumption of standalone operation and considering environmental load cases prescribed in Industry standards (ex. wind, wave and current all aligned). During a realistic operational condition, however, the presence of other unities may significantly alter the loads acting on the DP vessel which will affect somehow its station keeping capacity. Furthermore, in some areas of the world, the misalignment between the environmental loads and the presence of several wave trains from different directions (ex. off-shore Brazil) shall be considered in the sake of safety of the operation. In order to provide the clients means to simulate these complex operations (including moored vessels), a DP module has been integrated to Bureau Veritas multi-body mooring software, ARIANE. In this paper, the case of a DP floatel vessel operating close to a turret moored FPSO in Brazilian waters is analyzed and the differences in the DP capacity under realistic conditions with respect to the original DP capability are presented and discussed.

scholarly journals Environmental Load Evaluation of Nipigon River Bridge

2021 ◽  
Author(s):  
Stefan Hrnjak
Keyword(s):  
Climate Change ◽  
Load Factor ◽  
Environmental Load ◽  
Climate Trends ◽  
Environmental Loads ◽  
Fea Model ◽  
Load Combination ◽  
Temperature Load ◽  
If Current ◽  
Load Evaluation

If current climate trends continue, climate change will be inevitable and designing infrastructure which can withstand changing environmental loads will be a concern. Furthermore, current infrastructure will be affected and may require retrofitting or rehabilitation in order to meet safety and code requirements. The scope of this report is to determine the effect of increased environmental load factor coefficients on Nipigon River Bridge. An FEA model was created and the results from the model show that the bridge is sensitive to changes in environmental loads, particularly those of wind and temperature. An increase of 10% in wind and temperature load coefficients was enough to change the governing load combination and surpass the estimated moment capacities.

Hoisting Dynamics Analysis of Suspended Access Equipment

2010 ◽  
Vol 163-167 ◽  
pp. 708-712
Author(s):  
Xi Jian Zheng ◽  
Zhen Lu ◽  
Zheng Yi Xie ◽  
Yan Hong
Keyword(s):  
Impact Load ◽  
Load Factor ◽  
Acceleration Response ◽  
Response Curves ◽  
Load Effect ◽  
Structure Dynamics ◽  
Mechanics Model ◽  
Dynamics Response ◽  
The Impact ◽  
Dynamic Load Factor

Suspended access equipment (SAE) is widely used and the impact load effect on the structure of SAE while hoisting from the ground is to be researched. In the paper, three methods were taken to analyze hoisting dynamics response of SAE, including energy equation method, mechanics model calculation and finite element method (FEM), and it turns out that FEM is the perfect one. By using FEM, structure dynamics response curve and dynamic load factor were obtained. The effect factors of structure dynamics response were also analyzed. Measures were given finally to improve the effect of hoisting impact load by analyzing displacement and acceleration response curves of SAE.

Estimating Iceberg-Wave Companion Loads Using Probabilistic Methods

2015 ◽  
Author(s):  
Mark Fuglem ◽  
Paul Stuckey ◽  
Somchat Suwan
Keyword(s):  
Hydrodynamic Pressure ◽  
Offshore Structures ◽  
Probabilistic Methods ◽  
Wave Loads ◽  
Wave Loading ◽  
Wave Load ◽  
Sea State ◽  
Load Factors ◽  
Induced Velocity ◽  
The Impact

Many challenges arise when designing offshore structures for iceberg loads in arctic and subarctic regions. To help the designer, the ISO 19906:2010 standard provides guidance for the calculation of design ice loads using both deterministic and probabilistic approaches. In determining design loads for different environmental factors, both principal and companion actions must be taken into account; an example is iceberg actions and companion wave actions. ISO 19906 allows the designer to calculate the companion wave action as a specified fraction (combination factor) of the extreme level (EL) design wave load. Alternatively, the designer can calculate appropriate companion wave loads explicitly. A methodology has been developed at C-CORE in which representative iceberg actions are determined using a software package, the Iceberg Load Software (ILS). This is a probabilistic tool which uses Monte Carlo simulation to obtain a distribution of global impact forces based on the expected range of iceberg and environmental conditions that a structure would likely encounter. The software provides a reasonably accurate representation of the iceberg loading situation, following the provisions of ISO 19906:2010, without introducing unnecessary conservatism in the design load. In the software, the influence of waves on the iceberg actions are considered, but companion wave loads must be calculated and added externally to the software, The software accounts for the probability of different sea state conditions and the influence of the sea state on the probability and severity of iceberg impact, given the correlations between the sea state, iceberg management effectiveness and iceberg drift and wave-induced velocity. The additional hydrodynamic pressure due to the wave during the period of the impact; is not considered. This wave loading will be complicated by the influence that the presence the iceberg and structure have on the local sea state. In this paper, brief descriptions are provided of background studies on companion wave loading and the application of companion load factors in ISO 19906. The companion load factors allow the designer to apply the design wave load, which is calculated for situations with no iceberg present, to the case of iceberg impacts. In this study, a methodology is presented for determining companion wave loads based on the distribution of sea states expected during an iceberg impact. These sea states are significantly less severe than that associated with the design wave load as iceberg impacts are rare events. The companion wave loads are determined without accounting for the influence of the iceberg; this is thought to be quite conservative. An example application of the methodology is presented for a hypothetical platform located on the Grand Banks, off the east coast of Newfoundland. Iceberg actions, wave actions and combined iceberg-wave actions are estimated using the described methodology. Comparisons are provided for the resulting companion loads and those based on ISO 19906:2010 companion load factors applied to the extreme level wave load.

Recalibration of partial load factors in the Canadian offshore structures standard CAN/CSA-S471

2004 ◽  
Vol 31 (4) ◽  
pp. 684-694
Author(s):  
M A Maes ◽  
S Abdelatif ◽  
R Frederking
Keyword(s):  
Offshore Structures ◽  
Process Models ◽  
Pulse Load ◽  
Load Effect ◽  
Load Models ◽  
Code Calibration ◽  
Load Factors ◽  
Partial Load ◽  
Environmental Events ◽  
Load Types

The present paper describes a recalibration of the loading side of all the design check equations in the Canadian offshore structures standard CAN/CSA-S471, General requirements, design criteria, the environment, and loads (offshore structures). The recalibration was prompted by concerns about changing or improved load–load effect models and new load types and by Canada's intention to harmonize its offshore standards with the new International Organization for Standardization (ISO) offshore codes in the near future. Calibration is performed over wide ranges of combinations consistent with the normal application scope of CAN/CSA-S471. Updated load models are based on a more refined zonation of operational loads into loads of short duration and slowly varying live loads. Frequent environmental load processes and operational loads are modeled using Ferry-Borges–Castanheta pulse load models and infrequent environmental events and are based on point process models. The calibration is performed using a nonlinear optimization of an upwardly restrained safety objective function to result in optimal load factors, companion and combination factors, and optimal specified exceedance probabilities for infrequent load processes.Key words: load combinations, code calibration, pulse load models, safety factors, reliability levels.

scholarly journals Environmental Load Evaluation of Nipigon River Bridge

2021 ◽  
Author(s):  
Stefan Hrnjak
Keyword(s):  
Climate Change ◽  
Load Factor ◽  
Environmental Load ◽  
Climate Trends ◽  
Environmental Loads ◽  
Fea Model ◽  
Load Combination ◽  
Temperature Load ◽  
If Current ◽  
Load Evaluation

If current climate trends continue, climate change will be inevitable and designing infrastructure which can withstand changing environmental loads will be a concern. Furthermore, current infrastructure will be affected and may require retrofitting or rehabilitation in order to meet safety and code requirements. The scope of this report is to determine the effect of increased environmental load factor coefficients on Nipigon River Bridge. An FEA model was created and the results from the model show that the bridge is sensitive to changes in environmental loads, particularly those of wind and temperature. An increase of 10% in wind and temperature load coefficients was enough to change the governing load combination and surpass the estimated moment capacities.

Life Cycle Assessment Estimation for Eco-Management of Co-Generation Systems

2000 ◽  
Vol 123 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Seizo Kato ◽  
Naoki Maruyama ◽  
Yasuki Nikai ◽  
Hidekazu Takai ◽  
Anugerah Widiyanto
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Co2 Emission ◽  
Fossil Fuel ◽  
Optimization Theory ◽  
Environmental Load ◽  
Activity System ◽  
Environmental Loads ◽  
Whole Process ◽  
Load Factors

A LCA (life cycle assessment) scheme for any industrial activity system is introduced to estimate the quantitative load on the environment with the aid of the NETS (numerical environment total standard) method proposed by the authors as a numerical measure. Two kinds of environmental loads respecting fossil fuel depletion as input resources to the system and global warming due to CO2 emission as output are taken into account in the present eco-criterion, in which the total eco-load (EcL) value is calculated from the summation of respective environmental load factors on the whole process in a life cycle of the system. This NETS method is applied to eco-management co-generation systems, in which a computer-aided output navigator proceeds the LCA estimation with ICON and Q&A communication. An operation scheme most friendly to the environment with a minimum EcL value, i.e., an eco-operation scheme, is derived from the optimization theory.

scholarly journals Calibration of the Live Load Factor for Highway Bridges with Different Requirements of Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Lang Liu ◽  
Qingyang Ren ◽  
Xu Wang
Keyword(s):  
Structural Reliability ◽  
Highway Bridges ◽  
Calibration Method ◽  
Mean Value ◽  
Load Factor ◽  
Live Load ◽  
Load Effect ◽  
Load Factors ◽  
Short Period ◽  
Traffic Volumes

Highway bridge load rating has been moving toward structural reliability since the issuance of AASHTO LRFR specifications; however, the recommended load factors were carried out by a few reliable truck data. The objective of this study is to calibrate the live load factor in AASHTO LRFR Rating Specification by using huge amount of WIM data collected in California for more than ten years between 2001 and 2013. Since traffic volumes, vehicular overloads, and traffic components are highly related to the load effect induced, a set of calibration equations is proposed here, in which the nominal standard load effect models are used and different requirements of loading are taken into account. By the analytical model of platoons of trucks and the extrapolation of the gathered WIM data over a short period of time to remote future over a longer time period, the expected maximum live load effects over the rating period of 5 years are also obtained. Then, the live load factor is calibrated as the product of the codified value multiplied by the ratio between the nominal standard load effect and the expected mean value. The results show that the products of the two ratios present rather constant, implying the proposed method and load configurations selected are effective. In the end, the live load factors of 1.0 and 0.7 along with load configurations are recommended for a simple span length less than 300 ft. The recommended calibration method and live load factors will eliminate the unnecessary overconservatism in rating specifications.

Impact of spanwise non-uniform discrete gusts on civil aircraft loads

2019 ◽  
Vol 123 (1259) ◽  
pp. 93-120 ◽  
Author(s):  
M. Lone ◽  
G. Dussart
Keyword(s):  
Aircraft Design ◽  
Past Research ◽  
Maximum Load ◽  
Lower Envelope ◽  
Load Factor ◽  
Test Case ◽  
Research Experience ◽  
Aspect Ratios ◽  
Load Factors ◽  
The Impact

ABSTRACTThe drive for increasing flight efficiency is resulting in wing designs that are of higher aspect ratios, lower in weight, increased wingspans and, consequently, require greater attention in the disciplines of aeroelastics and loads. This trend in aircraft design, along with past research experience with flexible aircraft, motivate a review of assumptions in gust models; especially, that of the gust maintaining a uniform spanwise profile. In this paper, the authors investigate the use of spanwise varying 1−cos gust models for loads prediction using a non-linear aeroelastic model of a conventional large transport aircraft. The comparison between a test case using conventional uni-dimensional approach and another, using multidimensional gusts, illustrates the impact of stepping away from traditional discrete tuned gust processes and adding a spanwise varying gust component. A methodology for processing and analysing the loads data arising due to the added dimension is also developed and both envelope and correlated loads are considered. Gust characteristics and resulting load factor are, respectively, considered for comparison between the two models, as both metrics define realistic gust encounters. In this case, it has been shown that spanwise variation of gust profiles leads to lower envelope loads if viewed in terms of conventional gust gradients. However, higher envelope loads are found if the maximum load factors are matched.

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