Simulation of homogeneous and partially isotropic random fields

Four different approaches for the simulation of random fields, one of which is introduced herein, are examined. They are based on the spectral representation method, formulated to represent homogeneous and partially isotropic random fields, and generate simulations with random variability in both their amplitudes and phases. The four methods are compared in terms of the variability of the amplitudes and phases of the simulated processes. It is shown that, although all of them reproduce well the prescribed auto-spectral and cross-spectral density functions, some of them preserve spectral characteristics such as homogeneity and amplitude variability better than others. The four approaches are utilized in the simulation of spatially variable ground motions experiencing loss of coherence

Critical buckling strains in thick cold-formed circular hollow sections under cyclic loading

Contrary to the large dataset of test results exploring the monotonic bending response of steel tubes, the corresponding dataset of cyclic bending tests remains very small. Seven compact and semi-compact S355J2H cold-formed circular hollow sections with diameter to thickness (D/t) ratios between 20 to 60, representative of piles used in piers and wharves, were brought to failure in three-point cyclic bending tests. Digital Image Correlation was employed to estimate average cross-sectional curvatures, and hence the critical bending strains, during local buckling at the midspan plastic hinges. These estimates were compared against those from two simplified localised hinge models and differed by up to a factor of two. A parametric study was performed with a validated finite element model to ascertain the suitability of proposed design equations at predicting critical strains in piles with D/t from 20 to 60 under cyclic loading. Test and simulation data both show that critical buckling strains are lower under cyclic loading than under monotonic loading. This work can inform the future development of seismic design standards such as ASCE 61-14

Comparison of Fleet Size Determination Models for Horizontal Transportation of Shipping Containers Using Automated Straddle Carriers

Planning of horizontal transport is a significant problem with material impact on the development budget and productivity of a container terminal. This contribution uses Queuing Theory, Petri Networks and Discrete Event Simulation to address the fleet size determination problem for tactical planning. Considering the different information and modelling effort required for the three methods, it is recommended that Queuing Theory be applied in the preliminary planning stage as it is conservative, while Discrete Event Simulation which can yield significantly more cost-efficient results is applied for the detailed planning stage. Further development would be still required towards an easily applicable tool based on Petri Nets for practitioners to use in current planning problems, but the methodology itself can provide reasonable yet conservative results at a preliminary planning stage

Simulation Modelling of Ship-Berth Link With Priority Service

Simulation of the logistics activities related to the arrival, berthing, service and departure processes of ships in container ports can be carried out for different goals such as design of ship-berth link, increase productivity and efficiency of quay cranes, analysis and planning of operations at the ship-berth link, etc. These logistics activities are particularly complex and very costly since they require the combined use of expensive infrastructure capacities especially berths and quay cranes. Ship-berth link as a main port link is required to serve ships as quickly as possible. Thus, in order to successfully design and develop ship-berth link in a container port and utilise it as efficiently as possible, it is necessary to develop a simulation model that will support decision-making processes of terminal managers. The results, analysis and conclusions given in this paper are intended to provide guidance on achieving time efficiency and accuracy in the modelling of ship-berth link and calibration of ship-berth link simulation models for Pusan East Container Terminal (PECT). Maritime Economics & Logistics (2005) 7, 316–335. doi:10.1057/palgrave.mel.9100141