STRIAN 2.1 is a free online structural calculator for students and teachers. It can analyze both statically determinate and indeterminate structures. The program builds on the 2014 software STRIAN by Miroslav Stibor and Petr Frantík, and uses the Matrix Stiffness Method from MaFoDeM, another free structural analysis solver.
STRIAN 2.1 features several improvements over its predecessor, STRIAN:
Currently, there are no known bugs. Chrome web browser is recommended. STRIAN is tested on MS Windows (Chrome, Edge), Android (Chrome) and macOS (Safari, Chrome).
You can evaluate beams, frames and trusses for the internal forces. If your model is successfully solved, the following diagrams can be drawn:
Bars and beams begin and terminate at nodes, which are automatically generated. Hinges and supports can only be placed within these nodes. When bars intersect, they do not interact.
You can also press ESC to finish.
Supports and hinges must be positioned at nodes. Additional support types can be accessed and applied from the Node Table.
There’s a Hinges button in the toolbar. To place a hinge, select this tool, click Start, and keep clicking on the beam until the hinge appears at the desired end. For trusses, select all bars, click Apply (on all selected beams).
To use STRIAN as a truss solver, you must place hinges on the bars. You're solving for normal forces in a truss; thus, there will be no bending moments or shear forces on the members.
Inclined roller support is not implemented. However, a workaround can be achieved by using an auxiliary stiff bar connected via a hinge.
Loads are generated by pointing to the beam. If they're not placed precisely where you intended, you can click on the load to adjust its position. Alternatively, you can open the Load Table to modify the loads. For continuous loads spanning multiple sections, you'll need to repeat the load for each span.
The distributed load is specified per meter of the beam (not per the length as projected into the coordinate system). Example: if the beam is projected onto the horizontal axis as 1 meter long, but its actual length is 1.41421 meters, the total force would be 1.41421 kN.
See 'Load Table' description for details on temperature loads.
For most users, this function may not be needed. To create and switch among load cases, use the drop-down box next to the last tab.
For simple beams, defining cross-sections is unnecessary. Such structures can be solved without material or section properties, but deflection results depend on them. Assigned sections appear in the graphical view in parentheses next to the beam ID. For frames, assign appropriate sections to beams and columns for accurate results. Stiffness differences can significantly affect results.
In structural analysis, shear is typically ignored when assessing reactions or deflections, so Ash (shear area) is optional. Its value depends on the section type (solid, I-beam, hollow, etc.). Consult other sources if unsure.
Thermal and section parameters h and αT – safe to leave empty. Required only if analyzing temperature effects (rarely used).
After modifying a section, when you save, you will be prompted to specify whether you intend to create a new section or simply modify the current one.
Your structure can be described using nodes, beams, loads, sections, and settlements. Each category is displayed in its respective table, and you can edit parameters directly from these tables. You cannot add a new row directly from within a table.
Nodes are generated automatically when creating new beams. Incorrect coordinates can be corrected within this section. The first column displays the Node ID, which is also marked graphically next to the nodes. The last column indicates the support type at the node (if any).
The first column shows the Beam ID, also displayed near the midpoint of each beam. The second column lists the cross-section ID, shown in parentheses after the Beam ID. The next fields specify the start and end nodes, and the smaller fields indicate 'H'inge placement.
The tables display both the Node ID and the Beam ID, with the Node ID being crucial as it indicates the starting point of the beam. The distances where the loads are applied are measured on the beam from its starting point.
ΔT0: relative temperature change of the whole beam — positive expands, negative shrinks — may produce axial force.
ΔT1 = Ttop – Tbottom. Temperature difference between top and bottom fibers — may cause bending. Positive – top is warmer than bottom, negative – vice versa. Bottom = dashed line along each beam.
Thermal parameters must be set in 'Sections' for calculations to work.
Advanced feature: define multiple load cases on the same structure (e.g., 1: self-weight, 2: snow, 3: wind). Switching cases lets you work with separate load sets and view their individual results.
Sections that have been created will be listed in this table, and they can be edited here. The first column is Section ID, which can be used to assign a section directly to beam(s) from the Beam Table.
Some problems may involve support settlement due to factors like soil erosion or consolidation. Settlement can only be defined at the supports.
Table of settlements displays all nodes that have supports. If settlement is assigned to a node, it will be displayed here.
Your projects are saved on a server and cannot be stored on your local computer. When you use STRIAN for the first time, the program receives a unique User ID from the server, which acts as your dedicated folder on the server. If you run STRIAN on another device (or even on the same device with a different account or browser), another folder will be created on the server. To share files across your devices, use the same User ID from one device on all of them.
Only the structure is saved; results and settings are not included in the file.
The solver runs in your browser and doesn't rely on the internet. Initially, only reactions are displayed, but you can enable diagrams (SFD, BMD, NFD and Deflected shape) from the Settings dialog. If you require more detailed diagrams, create additional nodes within the specific area of interest.
This feature allows you to inspect the matrices assembled to solve the model. You can open them using the icon located to the right of the Beam Table. The units used are meters, radians, and newtons in the metric system; inches, radians, and pounds-force (lbf) in the imperial system, as shown in the diagram below.
You control what and how is displayed. In some cases, graphical representations may cause entities to overlap.
STRIAN operates internally in SI units, and coordinates are ultimately rounded to 1/100 of a millimeter precision. When switching to imperial units, you can input measurements in feet and inches, such as 2' 3", which is equivalent to 2.25 inches.