Elements

Some beam element formulations, such as those  employed in SeismoStruct for the elastic and inelastic frame elements, feature the disadvantage that, if the nodal displacement is zero, one then gets also nil strains, stresses, and internal forces (e.g. if one models a fully-clamped beam with a single element, and applies a distributed load (in SeismoStruct this is done my defining additional mass), the end moments will come out as zero, which is clearly wrong). To overcome this limitation, it is common for Finite Element programs to use so-called stress-recovery algorithms, which allow one to retrieve the correct internal forces of an element subjected to distributed loading even if its nodes do not displace. It is noted, however, that (i) such algorithms do not cater for the retrieval of the correct values of strains and stresses, given that these are characterised by a nonlinear history response, and (ii) will slow down considerably the analyses of large models. Users are therefore advised to disable this option in those cases where obtaining the exact values of internal forces is not of primary importance.

Note: Stress-recovery is only of use when distributed loads are defined through the definition of material specific weight or of sectional/element additional mass (but not through the introduction of dmass elements).

Carry out Performance Criteria Checks at the End Integration Sections
By activating this option users may select to carry out the defined Performance Criteria checks only at the end integration sections of the inelastic force-based element type (infrmFB), which are the locations on the member where checks are typically carried out. In this way, only the useful results are exported, without wasting time in processing the whole output for all the integration sections, and without confusing the user with redundant output.

Do not consider the axial force contribution in the shear capacity of beams
By activating this option the ability to carry out shear capacity checks ignoring the actual axial force applied on the beam member is provided. This feature is particularly important to the shear capacity checks of beams, when the interaction between fibre modelled RC beams and the rigid diaphragm adopted to simulate the concrete slab (a very common configuration in RC buildings) may cause the development of unintended fictitious axial forces in them.

Compute Masonry Shear Strength for Analysis
With this setting users may choose whether to calculate the masonry shear strength (i) only at the initial step or (ii) at all the steps until yielding in shear, i.e. even after reaching of the peak member capacity. The default option is the second, to update the shear strength until yield is reached, which is the best combination of accuracy and stability, since updating the shear strength in the descending branch of the capacity curve may lead to some convergence difficulties without significantly improving the accuracy of the solution.

Use elastic fibres in Masonry elements to increase numerical stability
Increased numerical stability is provided through the addition of very small elastic fibres in masonry elements. These elements allow for better convergence during the analysis without significantly affecting the element's overall response. By default this option is active.

Note: As discussed in here, FB formulations can take due account of loads acting along the member, thus avoiding the need for distributed loads to be transformed into equivalent point forces/moments at the end nodes of the element, and for then lengthy stress-recovery to be carried out.