Load Combinations

Directly enter the following basic items necessary to define load combinations in the Load Combination List.

No : Numbers are sequentially and automatically assigned in the order of the load combination entries.

Name : Enter the load combination name.

Note 
In the case of a construction stage analysis for a bridge structure, the loads applied in the construction stage analysis are integrated into the construction stage loads in the analysis. The analysis results are separately stored as the cases below. We can then obtain the analysis results for the load cases and their combinations for each construction stage. Separate load combinations must be specified for the Post CS using the following load cases and/or general load cases. We cannot however verify the auto-generated load cases below.

Dead Load (CS): Dead load including Self Weight included in construction stages

Erection Load (CS): Erection load defined by Load Cases to be Distinguished from Dead Load for CS Output of Construction Stage Analysis Control

Tendon Primary (CS): Analysis results due to prestressing forces in tendons

Tendon Secondary (CS): Indeterminate forces resulting from indeterminate condition of the structure

Creep Primary (CS): Results the (imaginary) loads causing creep strain

Creep Secondary (CS): Real member forces resulting from creep strain due to indeterminate structure

Shrinkage Primary (CS): Results for the (imaginary) loads causing shrinkage strain

Shrinkage Secondary (CS): Real member forces resulting from shrinkage strain due to indeterminate structure

Summation (CS): Summation of the results of all the cases above

Note 
The results for creep and shrinkage are separated to check the results individually.

Active : Specify Active if the corresponding load combination is applied in design.

Inactive : The corresponding load combination is not applied in the post-processing mode.

Active : The corresponding load combination is applied in the post-processing mode. (General tab)

Strength/Stress : The corresponding load combination is applied in the post-processing mode (Concrete Design tab) except for the serviceability check (crack and fatigue checks).

Serviceability : The corresponding load combination is applied in the post-processing mode (Concrete Design tab) except for the auto-design and strength check of beam members.

Type : Assign the combination types for analysis results.

Add : Linear combination of analysis results
L1 + L2 + ... + M1 + M2 + ... + S1 + S2 + ...+ (R1 + R2 + ...) + T + LCB1 + LCB2 + ... + ENV1 + ENV2 + ...

Envelope : Maximum, minimum and maximum of absolute values for individual analysis results

CBmax : Max (L1, L2, ..., M1, M2, ..., S1, S2, ...,R1, R2, ..., T, LCB1, LCB2, ..., ENV1, ENV2, ...)

CBmin : Min (L1, L2, ..., M1, M2, ..., S1, S2, ...,R1, R2, ..., T, LCB1, LCB2, ..., ENV1, ENV2, ...)

CBall : Max (|L1|, |L2|, ..., |M1|, |M2|, ..., |S1|, |S2|, ..., |R1|, |R2|, ..., |T|, |LCB1|, |LCB2|, ..., |ENV1|, |ENV2|, ...)

Note 
The CBall condition produces the maximum of absolute values; the results are produced in non-directional positive (+) values.

ABS : Linear combination of the absolute values of analysis results

|L1| + |L2| + ... + |M1| + |M2| + ... + |S1| + |S2| + ...+ (|R1| + |R2| + ...) + |T| + |LCB1| + |LCB2| + ... + |ENV1| + |ENV2| + ...

SRSS : Linear combination of the SRSS (Square Root of Sum of the Squares) of response spectrum analysis results and other analysis results

[L12 + L22 + ... + M12 + M22 + ... + S12 + S22 +...+(R12 + R22 +...) + T2 + LCB12 + LCB22 + ... + ENV12 + ENV22 + ...]½

where,

L : static analysis results for a unit load case × scale factor
M : static analysis results for a moving load case × scale factor
S : static analysis results for a settlement load case × scale factor
R : dynamic analysis results for a Response Spectrum case × scale factor
T : dynamic analysis results for a Time History Analysis case × scale factor
LCB : Analysis results for a predefined load combination × scale factor
ENV : Analysis results for a predefined envelop conditions × scale factor

Note 1 
Among the methods of load combinations, Envelope, ABS and SRSS can be applied in General only.

Note 2 
We can combine 150 load cases or load combinations in a load combination.

Note 3 
For the method of calculating principal stresses, effective stresses and maximum shear stresses for each load combination type, refer to the explanations at the bottom of the page.

Description : Short descriptions for the load combinations
Enter the unit load cases and the corresponding scale factors included in the relevant load combination as many times as desired.

Load Case : Select the unit load cases from the load case list or the load combinations defined earlier.

Factor : Enter the load (scale) factors corresponding to the selected unit load cases or load combinations.

Click the Auto Generation Button at the bottom of the load combinations dialog box. Select the following items in the displayed load combination auto-generation dialog box. If the OK Button is clicked, the load combinations are automatically entered as per the design code based on the user-defined unit load cases.

Note 
When accidental torsional moments are considered in Response Spectrum Analysis, load combinations are generated including the accidental torsional moments (Rx (ES), Ry (ES)).

Add : Add the generated load combinations to the previously defined load combinations

Replace : Replace the previously defined load combinations with the generated load combinations

Add Envelope : Envelope of load combinations is auto-generated. This is applicable in the General tab only.

Code Selection

Concrete : Design code for PSC

Design Code : Select the design code to be used for the auto-generation of load combinations (Refer to Note for design load combinations for different codes)

National Annex : Select the national annex when Eurocode is selected in design code. Recommended, Italy, Sweden, and Singapore National Annexes are available.

Scale Up Factor : Enter the seismic load scale factor where the seismic load is considered by the response spectrum analysis

Manipulation of Construction Stage Load Case : Select a method of auto-generating load combinations when Construction Stage Analysis has been performed.

Note 
This function becomes activated only when the construction stage analysis data has been created in the model.

ST Only : This option generates load combinations using only (general) static load cases (DL (ST), LL (ST)).

CS Only : This option generates load combinations using only construction stage load cases (DL (CS), LL (CS)).

ST+CS : This option generates load combinations using both (general) static load cases and construction stage load cases together.

Note 
When we use such general load types as DL and LL in Static Load Case in a construction stage analysis, the program internally creates both static load case (ST) and construction stage load case (CS). There are a number of possibilities for load combinations using such ST and CS cases.
If we wish to reflect the results of the construction stage analysis into design, we need to select the CS Only option. If we select the ST+CS option, the load cases used in the construction stage analysis are accounted for twice in the form of both static load case type and construction stage load case type. If we select the ST Only option, only the static analysis results are included in the design load combinations in which case the construction stage analysis results will be excluded from the design load combinations.
When we use the construction stage load (CS) type in a construction stage analysis, only the CS type is created after the analysis. In such a case, we need to select the CS Only option. By the same token, we cannot select the ST Only or ST+CS option because ST type loads do not exist.
When we distinguish the ST type and CS type loads in the preparation of data for a construction stage analysis, we need to select the ST+CS option to account for all the loads input in the model.

Consider Orthogonal Effect : When seismic forces are applied in two orthogonal directions, the combination effect is considered.

Set Load Cases for Orthogonal Effect : Set 2 load cases, which will be considered for Orthogonal Effect.

100% vs. 30% : 100% of seismic load in one direction and 30% of seismic load in the orthogonal direction are summed in absolute values.

SRSS (Square Root of Sum of Square) : 100% of seismic loads in both directions are combined in SRSS.

Note 1 
While generating the load combinations, the Orthogonal Effect can be applied only to the Load Cases that are specified in "Orthogonal Load Group".

Note 2 
In case where there are three seismic load cases, say EX, EY and EZ, Orthogonal Effect can be applied to EX-EY, EY-EZ and EZ-EX simultaneously, in V720. This feature was disabled in the older version. (This is also applicable to the Response Spectrum Load Case)

Define Factors for Variable Actions : Define Psi factors for Live Load, Snow Load, Wind Load, and Temperature load. This becomes activated only when Eurocode 2:04 or Eurocode 3:05 is selected.

Note 
When a building is designed as multi-use building, different Psi factor for imposed loads by category can be considered. For this, the user can specify two static load cases for imposed loads (ex. Load Case 1 for residential area, Load Case 2 for shopping area) and enter the corresponding partial factor as shown below.

Partial Factors for Actions : Define partial factor for permanent actions, Gamma G, and partial factor for variable action, Gamma Q. This becomes activated only when Eurocode 2:04 or Eurocode 3:05 is selected.

Note 1 
If serviceability load combinations are generated using Auto Generation, the generated load combinations are automatically categorized according to the load combination type in Design > General Design Parameters > Serviceability Load Combination Type. However, in case when the load combinations are generated manually, the user must manually classify the load combinations into one of three categories, i.e., Quasi-permanent, Frequent & Characteristic.

Note 2 
For the load factors to be applied to serviceability load combinations, refer to Table A1.1 & A1.4 of prEN 1990:2001.

Note 3 
For the procedures to be followed to check serviceability as per Eurocode 2 and Eurocode 3, refer to [Procedure for Serviceability Check as per Eurocode 2] in Design > Concrete Code Check > Beam Checking and [ Procedure for Serviceability Check as per Eurocode 3 ] in Design > Steel Code Check, respectively.