Loads

Load Cases and Combination Types

The load case manager is used to view and manage all load cases and load combinations in the project. Under the Service Cases tab, new service cases can be created and existing service cases can be modified or delete. Under the Load Combinations tab, the load combinations from several different building codes can be added or custom Factored combinations can be created.

Case Type	Description
Service Case	A container for holding physical loads grouped by load source. These load cases are not used directly for the design checks.
Building Code Combination	Automatic load combinations are generated based on defined building code equations. While building code combinations cannot be modified, the combinations from various codes can be included or excluded from the analysis. Also, any automatic load combination can be converted to a custom Factored Combination.
Factored Combination	Custom combinations of service cases with load factors that can be used for design checks.

Service Cases & Load Sources

Loads on a structure can come from a variety of sources such as the self-weight of the structure (Dead Load), external loads applied to the structure (Live Load, Snow Load, Wind Load, etc.), loads from inertia forces due to dynamic motion (Seismic Loads), and loads that are self-straining (Thermal Loads, Creep Loads, etc.). A variety of load sources are available in VAConnect (see the table below) which are based on the ASCE 7 and IBC design specifications. Service loads are the actual imparted loads on the structure to be used in the Load Combinations for the design checks. VAConnect automatically generates the service cases in the table below based on the various load sources. While load sources cannot be modified in VAConnect, custom Service Load Cases can be manually added in the Service Cases tab of the Load Case Manager. For example, a "Creep" Service Load Case could be added based on the Self Straining Load Source. All loads are added at the service load level in VAConnect.

Load Source	Service Load Case	Explanation
Dead	D	The self-weight of the structure and permanent fixtures on or in the structure.
Dead (Ice)	Di	The weight of ice on the structure.
Live	L	Loads due to moveable equipment or occupancy. Caution: Live loads are reduced by 50% in some IBC load combinations, use Lpa source for loads > 100 psf.
Live (Public Assembly)	Lpa(>100psf)	Garage loads, Public Assembly areas, or loads greater than 100psf. They have also been called "Exception" loads, because they appear in a separate clause in some building codes.
Roof Live	Lr	Roof live loads.
Rain	R	Rain load on an undeflected roof (excludes contributions from ponding).
Snow	S	Snow loads.
Seismic Loads (directional)	E+X, E-X, E+Y,E-Y, E+Z, E-Z	Earthquake or Seismic loads. E+X is for seismic loads in the positive global X-direction, E-X is in for the negative global X-direction, and similarly for the Y-direction and Z-direction.
Earth Pressure	H	Load due to lateral earth pressure, ground water pressure, or pressure of bulk materials
Fluids	F	Fluid load such as water in a storage tank.
Flood	Fa	Loads that result from water exceeding the local ground elevation. Flood load come from hydrostatic and hydrodynamic pressures such as water flowing over a bridge or waves passing through a building.
Self Straining	T	Loads from thermal expansion, creep, support settlement, etc.
Wind loads (directional)	W+X, W-X, W+Y, W-Y, W+Z, W-Z	Wind pressure loads. W+X is for wind loads in the positive global X-direction, W-X is for wind loads in the negative global X-direction and similarly for the Y-direction and Z-direction. Skewed wind load directions are also available (W+X+Y, W+X-Y, W-X+Y, etc.).
Wind on Ice	Wi+X, Wi-X, Wi+Y, Wi-Y, Wi+Z, Wi-Z,	Wind on Ice. The presence of ice can increase the surface-area of members and therefore the wind forces.
Other loads	Other	User-defined source available for special loads that need to be factored independently of other sources. These loads are not used in Building Code Combinations but can be used in Custom Factored Combinations.

Building Code Combinations

Building code combinations from a variety of building codes are built-in to VAConnect. The codes that are selected in the Load Case Manager are automatically maintained as loads are added or removed to the service cases. The building code combinations implemented in VAConnect do not necessarily represent all possible load combinations or variations present in a particular building code (for example, in the implementation of ASCE 7-10 load combinations, the major equations are implemented, but exceptions clauses of section 2.4 dealing with H, F, Fa are not implemented directly).

When one of the building code combinations is selected, VAConnect will use the current service load cases and generate the necessary combinations prescribed for that code. Note that any custom equation or factored combinations that are created manually will remain unaffected. When VAConnect generates building code combinations, it will generate combinations including the effects of wind and seismic in various directions, including (+/-X, +/-Y, +/-Z). Only load cases that actually contain loads are included in the combinations. The Load Case Manager displays the 'effective' combination of the equation which may be different than the equation in the building code.

Custom Load Combinations

Use the Create Factored Combination button located in the Load Case Manager to create any custom combination needed. Custom factored load combinations can be imported from the clipboard using the Import From Clipboard button in the Load Combinations tab in the Load Case Manager. Text must be tab delimited and copied to the clipboard in the following format:

{ComboName} {Factor} {ServiceCaseName} {Factor} {ServiceCaseName2} …

For example:

ComboName 1.2 D 1.6 L 0.5 Lr

MyCombo 0.9 D 1.3 W

Patterned Load Cases

Service cases may be given a pattern ID number allowing for various loading patterns to be modeled (such as loads on the odd/even spans). Each patterned service load case is combined independently in building code load combinations from other patterned load cases. For example, when dead load is applied and odd-span live loads are in a "Pattern 1" service case and even-span live loads are in a "Pattern 2" service case, the building code combination will generate the following combinations:

1.2D + 1.6L(1) (#1)
1.2D + 1.6L(2) (#2)

Any loads in an non-patterned load case (i.e. the dead loads for the example case above) are included in all of the load combinations. All of the built-in service cases have a default load patterns of 0 that cannot be changed. Therefore, new service cases must be created to define load patterns.

Load Sets

It is common for the same connection to be used at multiple locations throughout a structure and experience numerous loading conditions. The Load Sets feature in VAConnect allows a single connection to be designed with multiple sets of loads. For example, consider a structure with two W16x36 beams that use identical shear tab connections. The beams carry service level loads that produce the service level shear forces in the connection shown in the table below.

Service Load Case	Load Set 1 = Beam 1 Shear Force (kips)	Load Set 2 = Beam 2 Shear Force (kips)
Dead (D)	10	9
Live (L)	20	24
Snow (S)	20	16

It is not immediately apparent which set of loads (the shear on Beam 1 or Beam 2) will control the design of the connection. Based on ASCE 7, one of the following load combinations will control the design of the connection. The table below shows the six load combinations (three from each load set) that are used to design the connection. In VAConnect, the connection is designed for all six load combinations and can therefore be used for both beams.

1) 1.4D

2) 1.2D + 1.6L + 0.5S

3) 1.2D + 0.5L + 1.6S

Load Set	Load Combination	Connection Design Loads (kips)
Beam 1	1.4D	14.0
Beam 1	1.2D + 1.6L + 0.5S	54.0
Beam 1	1.2D + 0.5L + 1.6S	54.0
Beam 2	1.4D	12.6
Beam 2	1.2D + 1.6L + 0.5S	57.2
Beam 2	1.2D + 0.5L + 1.6S	48.8