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Moving loads

sens.16

Highlights

Influence lines are generated based on selected mobile load paths on the structure.
It is possible to define a system of mobile point and line loads.
The programme will automatically search for the critical positions of the load system on the structure, by analysing the calculated influence lines.
The envelope of the most unfavourable effects in the structure is also calculated automatically.
Generation and repositioning of complex groups of moving loads on slabs.
Arbitrarily shaped trajectories (tracks) may have straight or curved parts.
Automatic generation of load cases for each load position.
Tracking the critical positions for load groups on defined tracks.
Envelope results provide extreme internal forces, extreme stresses and deformations.

 

This module allows simulation of moving loads along a specified path on 1D as well as 2D members. It has two parts - train loads which is used for generation of quasi-moving loads on slabs and mobile load for definition of moving load along the specified path.

Train loads

The module Train loads allows you to generate quasi-moving loads on slabs:

  • Passing of predefined groups of forces (representing a train) along a track is simulated by a series of load cases. Each load case corresponds to one position of the load on the track;
  • The number of considered positions depends on a user-defined step size;
  • The critical position of the load groups can be determined as the results are presented in the form of envelope functions on the 3D model;
  • The loaded slabs may be flat or curved.

Mobile loads (incl advanced & train loads) Mobile loads (incl advanced & train loads) Mobile loads (incl advanced & train loads) Mobile loads (incl advanced & train loads)

Force groups

  • Groups of forces may consist of concentrated and/or uniformly distributed loads, surface and free loads;
  • By default, defined force groups move along the tracks as a "rigid body";
  • Turning points may be defined within long force groups, in order to represent a long vehicle with “joints”;
  • Groups of forces can be shared among projects;
  • A set of predefined force groups according to EN 1991 standard is provided;

Mobile loads (incl advanced & train loads) Mobile loads (incl advanced & train loads)

Mobile loads

The module for allows simulation of loads moving along a specified path on frames as well as surfaces.

Load systems

  • Each system is a combination of a distributed load of indefinite length and point loads that move together along a predefined path on the structure;
  • There is no limit to the number and variety of load systems that can be defined;
  • A library of predefined load systems according to various standards is provided.

Mobile loads (incl advanced and train loads) Mobile loads (incl advanced and train loads) Mobile loads (incl advanced and train loads)

Advanced load systems

An advanced load system contains multiple groups of mobile loads. Each group is a combination of line and point loads that move together along a predefined path on the structure:

  • In a moving load group, a distributed line load of finite length may be combined with a line load of indefinite length, and concentrated loads at relative locations.
  • Distributed loads may overlap or not with the concentrated loads; if these should not overlap, the line load can be broken into several parts.
  • In the advanced load system, a single, or two, or more identical and independent load groups may act together on the traffic lane;
  • When two identical load groups form a system, a minimum and maximum distances can be defined between the load groups - i.e. although the load move independently, some restrictions on the placement can be defined
  • When more than two identical load groups form a system, these are placed a fixed distance apart;
  • An ambient distributed load of indefinite length or between the groups may be added;
  • There is no limit to the number and variety of load systems that can be defined;
  • A library of predefined load systems according to various standards is provided.

Traffic lanes

  • You manually define the track along which the mobile loads will move;
  • Tracks can be updated and do not need to be redefined after changes in the model geometry - changed node coordinates, cross-sections, etc.;
  • Along the selected tracks, the extreme design components (such as maximum and minimum bending moments, reactions and deformations) are determined per load system.

Analysis (envelope derivation)

Mobile loads (incl advanced and train loads) SCIA Engineer determines the effect of moving load systems through influence line analysis:

  • Influence lines or surfaces for internal forces and deformations are generated per section on the existing traffic lanes;
  • An automatic searching routine determines the critical position of the load systems.

Some automated decisions are made in function of the sign of influence line ordinates:

  • Reduction coefficients may be applied on concentrated loads that fall in favourable regions of the influence line function;
  • Uniformly distributed loads only act in unfavourable regions of the influence line function;
  • Concentrated loads can be set to only act in unfavourable regions of the influence line function;
  • You may specify whether it is allowed to place the load partially outside the structure, if this would result in higher internal forces or deformations;
  • Loads can be set to appear only on a restricted interval of the traffic lane.

Based on the influence line analysis, envelopes (minimum and maximum functions) for internal forces, reactions and deformations are generated.

  • Envelopes are automatically calculated per mobile load system;
  • For this, you may ignore regions with favourable values in the influence lines (with opposite sign);
  • An additional multiplication factor can be applied according to the VOSB code (NEN code) for internal forces and reactions.

Note: The standard stipulates that this factor is not to be applied on deformations. Therefore, it is possible to obtain larger deformations from a load case linked to envelope internal forces compared to load cases linked to envelope deformations.

Load case generation

Actual or fictitious load cases may be generated based on envelopes.

  • Actual load cases contain the load systems converted to standard loads on the structure, and placed on the critical positions as determined in the influence-line-based analysis;
  • A series of fictitious load cases with the maximum and minimum functions of the components of internal forces and displacements may be generated; these load cases contain no actual loads - rather just the effect of such loads - moment diagrams, deformations, etc.
  • These load cases can be combined with other types of loads in standard combinations and thus be used in section and stability checks.

Note: Fictitious load cases are valid only for the component for which they were derived. Thus, a load case derived for minimum bending moments My will contain valid and meaningful results only for My diagrams, and not for other internal force or deformation components.

The module calculates the interference of several groups of mobile loads on frames.

  • user-defined single or grouped mobile loads consisting of point or/and distributed loads can be simulated;
  • built-in load groups according to different national codes are provided.

The module also calculates the interference of several groups of mobile loads on frames and surfaces.

Applications

Advanced load systems are suitable for the modelling of complex loads on structures such as:

  • traffic on road- and rail-bridges, viaducts, etc.;
  • moving loads on crane tracks;
  • crowd movement on pedestrian bridges and floor slabs.

Included in Edition: 
Professional
Expert
Ultimate
Mobile loads (incl advanced and train loads)
Mobile loads (incl advanced and train loads)
Mobile loads (incl advanced and train loads)
Mobile loads (incl advanced and train loads)