The study deals with stability and dynamic problems in bar structures using a probabilistic approach. Structural design parameters are defined as deterministic values and also as random variables, which are not correlated. The criterion of structural failure is expressed by the condition of non-exceeding the admissible load multiplier and condition of non-exceeding the admissible vertical displacement. The Hasofer-Lind index was used as a reliability measure. The primary research tool is the FORM method. In order to verify the correctness of the calculations Monte Carlo and Importance Sampling methods were used. The sensitivity of the reliability index to the random variables was defined. The limit state function is not an explicit function of random variables. This dependence was determined using a numerical procedure, e.g. the finite element methods. The paper aims to present the communication between the STAND reliability analysis program and the KRATA and MES3D external FE programs.
The paper presents a spatial model of the satellite antenna with an arbitrary number of flexible arms. Such a system is an example of an open kinematic chain with a tree-like structure. The modification of the rigid finite element method is used to discretise flexible links. The equations of motion are derived from the Lagrange equations and the motion of the system is described using joint coordinates and homogenous transformations. Numerical simulations have been carried out to analyse how the method of extending the arms influences the dynamics of the system.
Several previous investigations on failure of a certain type lattice girders railway bridge (on so called BJD line) have not convincingly explained reasons nor have they described potential hazards. This paper attempts to provide an answer, employing static, dynamic, and fatigue analysis of the structure, focusing on previously not analyzed vibrations of elements constituting a lattice node. Detailed models of two types of such nodes – damaged and non- damaged were compared, inside carefully defined limits of applicability.
The paper presents a dynamic analysis of the damaged masonry building repaired with the Flexible Joint Method. Numerical analysis helped to determine the effect of the applied repairing method on natural frequencies as well as values of stresses and accelerations in the analyzed variants of numerical model. They confirmed efficiency of the proposed repair method.
The paper presents a model for dynamic analysis of belt transmission. A two dimensional discrete model was assumed of a belt consisting of rigid bodies joined by translational and torsion spring-damping elements. In the model, both a contact model and a dry friction model including creep were taken into consideration for belt-pulley interaction. A model with stiffness and damping between the contacting surfaces was used to describe the contact phenomenon, whereas a simplified model of friction was assumed. Motion of the transmission is triggered under the influence of torque loads applied on the pulleys. Equations of motion of separate elements of the belt and pulleys were solved numerically by using adaptive stepsize integration methods. Calculation results are presented of the reaction forces acting on the belt as well as contact and friction forces between the belt body and pulley in the sample of the belt transmission. These were obtained under the influence of the assumed drive and resistance torques.
The iron ore mine owned by the state concern of Luossavaara – Kiirunavaara AB-LKAB state concern has several mining skip shaft hoists for drawing iron ore. Despite using modern systems to secure the travel of these hoists in line with the Swedish regulations, units intended for the emergency breaking of vessels must be used in the so-called free travel paths in the tower and in the shaft sump. The paper discusses the main requirements that, in accordance with the Swedish regulations as regards the operational use of mining shaft hoists, must be met by devices of this type and a solution was proposed for a structure design of the braking unit for the mining shaft hoist installed in the B-1 shaft in the Kiruna mine. The frictional braking system in the form of moving bumping beams was decided to be used in the said hoist, developed in the Cable Transport Department in the University of Science and Technology in Krakow. The action of moving bumping beams consists in these beams, placed at the beginning of free travel paths, not only braking the rushing hoist vessels but also (with the integrated units for vessel capture) performing the function of grips. They secure the vessels against falling down into the shaft after the finished braking process. The advantage of such a solution is that the structural elements: the guiding shank of the tower, the head of the vessel and the bumping beams, transfer many times lower values of dynamic forces at the time of the strike of the vessel against the moving bumping beams when compared with dynamic forces arising at the time of the hit of the vessel against the fixed bumping beams. In the process of designing moving bumping beams, braking simulation is an important stage conducted with a computer program developed in KTL AGH. This program enables the modelling of load-bearing and balance ropes as flexible elements with elastic and suppressing properties. The results of these simulations, especially in the scope of the achieved braking deceleration of the vessels, the values of braking distances and forces in the load-bearing ropes are crucial in confirming the correctness of the assumed concept of the emergency braking system. The braking units in the form of moving bumping beams have been executed by the Polish company Coal-Bud Sp. z o.o. and are now being integrated in the tower and in the shaft sump of the B-1 shaft of the Kiruna mine in Sweden.
The dynamic analyses are of key importance in the cognitive process in terms of the correct operation of structures loaded with time alternating forces. The development of vehicle industry, which directly results in an increase in the speed of moving vehicles, forces the design of engineering structures that ensure their safe use. The authors of the paper verified the influence of speed and vehicle parameters such as mass, width of track of wheels and their number on the values of displacements and accelerations of selected bridge elements. The problem was treated as the case study, because the analyses were made for one bridge and the passage of three types of locomotives. The response of the structure depends on the technological solutions adopted in the bridge, its technical condition, as well as the quotient of the length of the object and vehicle. A new bridge structure was analyzed and dynamic tests were carried out for trainsets consisting of one and two locomotives. During the actual dynamic tests, the structure was loaded with a locomotive moving at a maximum speed of 160 km/h.