EQUIframe – frequently asked questions
How does EquiFrame calculate support reactions in a frame?
EquiFrame calculates frame support reactions using the static equilibrium equations (∑Fx=0, ∑Fy=0, ∑M=0) for the entire system, and in more complex frames it adds extra equations by dividing the structure into parts and writing equilibrium for each of them separately. This allows it to determine reactions even when the system cannot be fully solved using only one set of global equilibrium equations.
- Global equilibrium: it starts with the general equations ∑Fx=0, ∑Fy=0, ∑M=0, including all loads (forces, moments, distributed loads).
- Supports and unknowns: identification of restraints (fixed, roller, fixed-end support, and other combinations of degrees of freedom) and assignment of the corresponding reactions.
- Complex systems: the frame is divided into individual “bodies” / members, and equilibrium equations are written for each member separately.
- Connections between members: introduction of unknown forces in hinges (and other kinematic restraints), together with action-reaction conditions between adjacent parts.
- Step-by-step solution: once the equations are assembled, the program eliminates unknowns (substitution / system of equations) until the final support reaction values are obtained.
The result is given directly as support reactions, and at the same time it can be easily verified through the overall force and moment balance of the structure.
Does EquiFrame analyze internal forces in frame elements?
Yes. EquiFrame analyzes internal forces in frame elements by determining the distributions of axial force, shear force, and bending moment based on the internal force equations. The results can be read at any section and on diagrams.
- Internal force equations: for each element, it formulates the relationships for N(x), V(x), M(x) from section equilibrium conditions.
- Load inclusion: concentrated forces, moments, and distributed loads (constant and linearly varying) are included directly in the distributions.
- Piecewise functions: it builds functions over the appropriate intervals between joints and load change points (including jumps caused by concentrated forces/moments).
- Value at any point: you can check the values at a selected location x and at characteristic points (joints, supports, load application points).
- Visualization of results: in the end, you receive clear N–V–M diagrams for each element.
This makes it easy to quickly see which frame elements are the most highly loaded and how they transfer loads through bending and axial tension/compression.
How does EquiFrame analyze static determinacy and geometric stability?
EquiFrame analyzes static determinacy and geometric stability based on classical mechanics conditions, separately for single-body and multi-body systems. Geometric stability is additionally checked using rules based on the theorems of 2 and 3 rigid bodies.
- Necessary condition (statics): it counts the unknowns (reactions + forces in connections) and compares them with the number of available equilibrium equations (∑Fx, ∑Fy, ∑M) per body.
- Single-body systems: determinacy is assessed based on the relation “number of unknowns = number of equations” for one rigid body.
- Multi-body systems: the frame is divided into bodies, and equilibrium equations are considered for each body separately, together with unknowns in hinges/connections.
- Geometric stability: the program checks the stability of the system based on rules for body connections, verifying whether the system forms a mechanism.
- Theorems of 2 and 3 bodies: verification of typical configurations (two / three members) to determine whether the restraints and connections ensure geometric stability.
- Diagnostic result: indication of whether the system is determinate/indeterminate and whether it is geometrically stable before reaction and force calculations begin.
This helps immediately detect cases of a “mechanism” or incorrectly defined supports before the user moves on to the actual calculations.