New enhancements in composite design
Following significant extensions of SCIA Engineer EuroCode 4 functionalities in version 18.0, version 18.1 offers even more to engineers who design buildings with composite floors:
- strength and serviceability verifications, as wells as AutoDesign for beams with multiple web openings (according to SCI P355);
- economic solutions through the possibility to reduce composite action below the limitations of Eurocode 4 (according to SCI P405);
- more accurate natural frequency calculation and additional check options for better prediction of floor vibration issues.
Large web openings
Large web openings are common in composite beams: especially in multi-storey office buildings, where services often need to be incorporated within the structural depth. SCIA Engineer v18.0 set the first step towards supporting web openings in composite beams: with checks for a single web opening along the beam.
The new version 18.1 of SCIA Engineer goes a few steps further, not only with checks for multiple openings of various shapes, but with the full integration of the opening within the beam definition. As a result, all openings are:
- visualised on the structure,
- taken into account on the level of FEM calculation,
- verified on the level of both strength and serviceability considerations.
Strength calculations are performed according to the SCI Publication P355 "Design of composite beams with large web openings." The design methods provided there make it possible to design in SCIA Engineer beams with circular, rectangular, and elongated (oval) openings, as well as the combination of these. Size and eccentricity may also vary between adjacent openings.
The newly provided verifications cover not only failure at the weakened section at the opening, but also failures at the web posts between openings. All opening checks are also included in the automatic design.
At the openings, checks are executed for compression, bending and shear of the T-sections (formed by the steel section flanges and the remainder of web), as wells as for vierendeel bending and shear buckling of the web. At the level of web posts, checks are executed for longitudinal shear and bending, as well as web post buckling and shear.
Practical geometric limitations according the SCI P355 are also checked. Any issues found on the beams are reported not only in the calculation output, but also via the Error Warning Note reporting system, i.e., directly on the beams inside the 3D scene.
Quite flexible reporting capabilities have been added as well. The user can print a detailed report with the formulas of the calculation for all openings; the same report can be obtained only for the critical opening and critical web post along the beam. The same is valid for the Standard output: the user can choose whether all openings and web posts should be reported, or just the critical ones.
Support for SCI P405
EuroCode 4 limitations on the minimal degree of shear connection can be rather stringent. The SCI publication P405 summarises the findings of more recent research on the topic, also taking into account more modern sheeting geometries.
In short, it is acceptable to design composite beam will lower composite action, if certain conditions are fulfilled. The publication gives adapted formulas for the derivation of minimal shear connection and when these formulas can be applied.
It is now possible to apply these rules in SCIA Engineer when designing composite beams: for all beams on the structure or on selected beams only. Additional spacing requirements mentioned in the publication are also taken into account.
Enhanced natural frequency check
A significant improvement in the vibration check for composite beams is that now frequencies are calculated assuming full composite action for all load cases acting on the beam (as clarified in SCI P354: Design of floors for vibration). As a result, the calculated frequency is much closer to the real free vibration response of the floor.
The user can now also control the vibration check via additional options:
- the minimal frequency limit of 4Hz can be overwritten;
- the user can specify whether the dynamic modulus of elasticity of concrete should be used or not;
the percentage of live load to be considered in the frequency derivation can be overwritten;
- the user can disable the vibration check for certain members in the structure or altogether.
Version 18.1 of SCIA Engineer brings important extensions for composite floor design.
The handling of multiple web openings on a beam (foreseen for the purpose of accommodating various installations) makes it possible to achieve an economic and time-efficient design when land costs and the available minimum headroom are a limitation.
For long-span beams, less tight limitations for shear connection make it possible to design with fewer studs, which often translates lower production and overall costs.
A more accurately calculated natural frequency indicates to the designer what next steps are needed in order to address serviceability considerations.