Load enhancements in SCIA Engineer 14
Load combinations according to IBC 2012 (ASCE 7-10)
SCIA Engineer now automatically generates load combinations according to the recent International Building Code (IBC 2012) and the"Minimum Design Loads for Buildings and Other Structures" code (ASCE 7-10). These most recent versions of the standards contain modified rules (equations) for the combination of loads - both the components in the equations and the combination coefficients have been modified; also additional equations have been added to replace some of the obsolete old ones.
- The automatic combination of loads in version 14 of SCIA Engineer takes into account all updates in IBC 2012 for both LRFD and ASD combinations -- the considered load types, the modified combination coefficients, the new equations.
- The f1 and f2 coefficients in IBC 2012, for live and snow loads respectively, are also taken into account appropriately - options are added in the Combinations menu to let the user choose the correct type of load and function of the floor/roof configuration;
- Temperature loads are considered by two additional combination rules (equations), as recommended in the Commentary of ASCE 7-10;
- The (dis)advantageous action of the H load type (load due to lateral earth pressure, ground water pressure, or pressure of bulk materials) is taken into account by creating combinations with both increased and reduced coefficients for the load type H (1.6 and 0.9 and 1.0 and 0.6 for LRFD and ASD respectively);
- Load combinations according to the previous version of the norms (IBC 2006 and ASCE 7-05) may also be generated via the same menu;
- An automatic filtering of the generated combinations ensures that no duplicates remain among the envelope combinations. This feature is implemented for both the new and old version of the standards.
3D Wind Loading according to ASCE 7-10
SCIA Engineer v14 now supports 3D wind load application per ASCE/SEI 7-10.
The release of the new specification for Minimum Design Loads for Buildings and Other Structures (ASCE/SEI 7-10) includes major changes to the determination and application of wind loading on structures. These changes are focused around the change in the calculation of the velocity pressure (qz) which is applied to the structure. More specifically, these changes include:
- The addition of building Risk Categories (I, II, III & IV) and removal of Importance Factor, I.
- The implementation of wind speed maps (varying based on building Risk Category) which are set for strength level design
- Modification of the strength design wind load factor from 1.6 to 1.0.
- Allowance for use of gust factor, G = 0.85 for all structures
Currently, SCIA Engineer v14 supports the Direction Procedure (ASCE/SEI 7-10, Chapter 27) for wind load application. This method is analogous to the All Heights Method found in ASCE/SEI 7-05 (which is already supported in SCIA Engineer). Further implementation of the Envelope Procedure (similar to the Low Rise Method found in ASCE/SEI 7-05) is ongoing and will include the changes to load cases and wind zones found in Chapter 28 of ASCE/SEI 7-10.
Seismic combinations and the 30% rule
The 30% rule in seismic design presumes that seismic actions perpendicular to the main earthquake direction that is currently considered should be taken into account with reduced intensity of the resulting load effects, namely 30% of the values originally calculated. In previous versions of the software, the user needed to create three load combinations and manually implement the 30% rule by assigning 0.3 and 1.0 (active) coefficients where needed.
- In version 14 of SCIA Engineer, the 30% rule is automatically taken into account when generating seismic combinations;
- A generated combination according to the norm contains the 30% rule - after exploding to envelope combinations the user may review to generated coefficients;
- When a project created in older version of the software is opened, a message is sent to the user that the rule has been applied and manually created combinations may be deleted;
- Accidental eccentricity load cases are now generated automatically as slave load cases to a master that contains the corresponding seismic action per X/Y/Z direction;
- When it comes to the 30% rule, it is applied to the accidental eccentricity load cases with an identical coefficient (0.30 or 1.00) as for the master load case.
Model factor "Pond load"
The derivation of water accumulation loads is an iterative procedure, during which the structural deformations caused by permanent loads and loads from water ponding are taken into account at each iteration. The load functions are then generated automatically on all loaded beams.
- Since version 14 for SCIA Engineer, it is possible to reduce the stiffness of the structure during this iterative process;
- Such stiffness reduction is recommended in the NEN 6702 norm, where a Young's modulus reduction of 1/1.3 is recommended;
- The reduction coefficient can be set by the user (the value of 1.3 is fixed in the NEN 6702 norm).