Stefan Kaczmarczyk

In high-rise buildings earthquake ground motions induce bending deformation of the host structure. Large dynamic displacements at the top of the building can be observed which in turn lead to the excitation of the cables/ropes within lift installations. In this paper, the stochastic dynamics of a cable with a spring-damper and a mass system deployed in a tall cantilever structure under earthquake excitation is considered. The non-linear system is developed to describe lateral displacements of a vertical cable with a concentrated mass attached at its lower end. The system is moving slowly in the vertical direction. The horizontal displacements of the main mass are constrained by a spring-viscous damping element. The earthquake ground motions are modelled as a filtered Gaussian white noise stochastic process. The equivalent linearization technique is then used to replace the original non-linear system with a linear one with the coefficients determined by utilising the minimization of the mean-square error between both systems. Mean values, variances and covariances of particular random state variables have been obtained by using the numerical calculation. The received results were compared with the deterministic response of the system to the harmonic process and were verified against results obtained by Monte Carlo simulation.

Fatigue lifetime of offshore pipelines with semi-elliptical circumferential surface cracks is often underestimated. An accurate prediction of the pipeline structural integrity is nevertheless important in order to prevent unnecessary and expensive downtime, failures leading to leakage or spillage of pipeline contents to the surrounding environment, and ultimately improve the reliability of the pipeline. The estimation of crack growth in pipelines under varying loads is highly dependent on the calculation of crack driving parameters, such as the stress intensity factor and the crack tip opening displacement (CTOD) using the 3D J-integral or its equivalent. This paper presents a numerical study to predict the fatigue lifetime of cracks in pipes, determining the J-integral that includes first and second derivatives of the displacement field for pipes containing a range of circumferential surface cracks. A pipe segment is structurally loaded and stress intensity factors (SIF) evaluated using the finite element method (FEM). Based on the results, a number-of-cycles to failure curve shows a longer lifetime than previously predicted by about 5% for a pipe with semi-elliptical external surface cracks. In addition, they indicate that the external short cracks are more dangerous than the internal long surface crack hereby requiring earlier assessment.

The non-linear stochastic dynamic behaviour of a high-rise vertical transportation system modelled as a concentrated mass and a cable with finite bending stiffness is considered. The slow time scale is defined and lateral cable displacements coupled with transverse motions are expanded in terms...

At present, there are benchmarking parameters to assess the energy performance of lifts, e.g. one in Germany adopted by VDI (4707-1/2), one internationally published by ISO (BS EN ISO 25745-2:2015), and the other in Hong Kong adopted by The Hong Kong Special Administrative Region (HKSAR) Government. These parameters are mainly checking and governing the energy consumed by a lift drive without considering real time passenger demands and traffic conditions, the one in Hong Kong pinpointing a fully loaded up-journey under rated speed while the two in Europe pinpointing a round trip, bottom floor to top floor and return with an empty car, though including energy consumed by lighting, displays, ventilation etc. A holistic normalization method (So et al 2005, Lam et al 2006) was developed more than ten years ago by the first author of this article, which can simultaneously assess both drive efficiency and traffic control performance, termed which is the name of the parameter measured in unit, J/kgm, and is now adopted by the HKSAR Government as a good practice in the Technical Guidelines of the Energy Code, but not yet enforced in the mandatory code. In Europe, the energy unit of Wh has been used but here, the unit of Joule (J), i.e. Ws, is adopted to discriminate the difference between the two concepts. In this article, such parameter is evaluated under different drives and lift traffic control scenarios by using computer simulations, with the aim of arriving at a reasonable figure for benchmarking an energy efficient lift system with both an efficient drive as well as an efficient supervisory traffic control. This parameter could also compare the performance of different types of intelligent car dispatcher.

A computational study has been conducted to investigate the transient aerodynamic forces experienced by two vehicles overtaking each other. Ahmed body model has been used to represent the vehicles. The transient effects during the overtaking scenario have been determined by using a Computational Fluid Dynamics (CFD) model. This has been achieved by developing an open source computational code. The aerodynamic effects have been investigated by emulating this event in a virtual wind tunnel. One of the generic vehicles was set to be stationary, while the other was allowed to be moving at constant speed. The Delayed Detached Eddy simulation (DDES) turbulence approach has been applied in this study based on the finite volume analysis (FVA). The computational results such as fluid forces and moments acting on the vehicle structures have been compared against published experimental results. Encouraging correlations between those results are observed. In the present work, the fluid-structure interaction (FSI) phenomenon has also been studied by developing a flexible body dynamic model. The modal and dynamic responses are determined from FEM analysis by the application of fluid transient loads obtained from the CFD model. This investigation is important to address the issue of stability and performance of the vehicle system. This work provides a significant understanding into the complex aerodynamics of an overtaking process and gives the foundation for further analysis in the area of fluid-structure interactions for more complex geometries and scenarios.

Tall building structures are susceptible to large sway motions when subjected to earthquake excitations. They are particularly affected by long period earthquake ground motions. These low frequency seismic waves resonate with the fundamental mode of the building structure which in turn causes resonance interactions with long slender continua deployed in modular non-structural installations, such as lifts. Damage due to large resonance motions of suspension/compensating ropes and cables during earthquake are one of the most common modes of failure in high-rise lift installations. In this paper an analytical model to predict the dynamic responses of a suspension rope system installed in a tall host structure under seismic conditions is presented. The model is then used to predict the dynamic performance of the system under earthquake excitations. The predictions can then be used to develop suitable mitigating strategies and protective measures to minimize the earthquake damage.