Plate girder is an economical choice for long spans construction. I-section steel plate girder typically has a deep web to maximize its shear capacity and flange separation, yet thin web to minimize the self-weight. Due to its large height-to-thickness (h/tw) ratio, transverse stiffeners may be required to stiffen the slender web.
The calculation of complex structures by means of finite element analysis software is generally performed on the entire model. However, the construction of such structures is a process carried out in multiple stages where the final state of the building is achieved by combining the separate structural parts. To avoid errors in the calculation of overall models, the influence of the construction process must be considered. In RFEM 6, this is possible using the Construction Stages Analysis (CSA) add-on.
The determined values for the influence ordinates are displayed as decimal numbers with up to six decimal places by default. This is usually sufficient for the influence lines of internal forces.
Until now, the prestress load type had always been an initial prestress in Dlubal Software programs. The defined load magnitude was applied and, depending on the stiffness of the surrounding system, prestress remained more or less as an axial force in the cable.
RF-MOVE Surfaces facilitates the generation of load cases from different positions of moving loads. Based on the load positions of the moving load, the program generates separate load cases for RFEM 5. Optionally, an enveloping result combination of all load positions is created.
In addition to the basic combination rules of EN 1990, there are other combination conditions for actions on road bridges specified in EN 1991‑2 that must be taken into account. RFEM and RSTAB provide automatic combinatorics that can be activated in the General Data when selecting the standard EN 1990 + EN 1991‑2. The partial safety factors and combination coefficients depending on the action category are preset when selecting the respective National Annex.
Daily tasks in reinforced concrete design also include designing compression elements subjected to biaxial bending. The following article describes the different methods according to Chapter 5.8.9, EN 1992-1-1, which can be used to design compression elements with biaxial load eccentricities by means of the nominal curvature method according to 5.8.8.
With RF-FOUNDATION Pro, it is possible to determine the settlements of single foundations and resulting spring stiffnesses of the nodal supports. These spring stiffnesses can be exported into the RFEM model and used for further analyses.
Influence lines are less important nowadays due to fast computer systems. However, it might be an advantage to use influence lines in the phase of preliminary design, as well as in the actual creation of the structural designs. With the RF-INFLUENCE add-on module, influence lines and influence surfaces can be generated and evaluated easily due to a fixed internal force. This technical article describes, with a simple example, the basics of determining and evaluating influence lines.
Design loads specified in the AASHTO Bridge Design Specification are available in the RF-MOVE Surfaces moving load library. Design Truck (HS-20), Tandem, Type 3, and Overload are available options.
The current state of the development of finite element analysis software and computer technology allows for the calculation of more complex structure. More and more frequently, FE calculations are performed on the entire model. In this context, certain practical construction problems may appear. One of these problems is the consideration of a construction process in the model.
If you select the combinatorics according to EN 1990 + EN 1991‑2 and define a load case in action category gr1a, gr2, or gr5, you have to additionally define in the program which load model should be taken as a basis for the load case. This information is crucial for defining combination rules for automatic combinations according EN 1990 + EN 1991-2. In the gr1a category, you can select TS (LM1), UDL (LM1), or pedestrian and cycle track, for example. TS (LM1) is preset by default. In the gr2 category, you can select breaking and acceleration forces or centrifugal forces as a specification.
For the reduction of loads generated in RF‑MOVE Surfaces, you can consider the influence surfaces of a selected point. The influence surfaces are determined by RF-INFLUENCE. This procedure is useful in cases where only unfavorably acting loads should be considered. Depending on the unfavorable action, you should select the positive or negative direction.
Moving loads can be generated easily with RF‑MOVE Surfaces. A library is available with load models as defined in Eurocode 1, Part 2. The input of step size, offsets at start and end, and the distance to a reference line make it possible for the user to generate user‑defined load models and influence the number of load cases generated. RF‑MOVE Surfaces generates load cases and, optionally, a result combination as an envelope of all results.