RM-Set (PIERDIM) > Info/Modification

Definition of the parameters of an RM Set of the type "PIERDIM". RM Sets of this type are used to define the requirements for extended ultimate load checks (actions UltLc, UltSup) for piers.

Several design codes require for piers taking into account additional eccentricities of the compressive normal force, covering the effects of unintentional shape deviations and/or p-delta effects. The additional eccentricity is in principle a function of the slenderness, i.e. of the relevant buckling length and the cross-section dimensions. The actual parameters to be defined are slightly different for the different design codes. For some codes it is also possible to define a reduction factor PHI, which is used in the calculation of the normal force capacity Nx.

Data definition concept

The required parameters are entered line by line for the considered elements. The bending directions are treated separately, i.e. two lines have to be entered for the same element series, when additional eccentricities in both directions shall be considered. This allows also defining different buckling lengths for the different directions.

Setting

Description

Design code

Selection of the design code to be applied.

Setting	Description
General	Use a general set of variables as specified in Variables > Eccentricities. The default name of the variable is etot. A template set of variables with this name may be imported from the default database, group OeN_Austria. This set of variables can be used for codes, where the additional eccentricity is a function of the buckling length, an imperfection factor and a lower limit condition defined by the "Factor for min. ecc." (FACT_YZ in Tcl).
DIN FB 102	Use the set of variables as defined in the default database in the dataset for DIN_Germany (DIN_etot).
Eurocode	Use the set of variables as defined in the default database in the dataset for Eurocode (EC2_etot).
Chinese Highway Code	Use the set of variables as defined in the default database in the dataset for Highway Code JTG D62 (JTG_etot and JTG_phi).
Russian Standard SNiP	Use the set of variables as defined in the default database in the dataset for Russian Standard (SP_etot and SP_phi).

Variables

Setting

Description

Eccentricity

Name of the Variable, defining the total eccentricity of the normal force to be used in the ultimate limit checks (formula for calculating this eccentricity in accordance with the design code). I.e. the considered (secondary) bending moment is taken as the product of the design normal force and this eccentricity rather than the respective design moment, with considering the sign of the design moment. The user may define this variable in accordance with his needs as a function of internal or other user defined variables, or take over the respective variable and set of sub-variables from the default database.

Reduction factor

Name of the Variable, defining the stability factor φ for reduction of the normal force capacity of concentrically compressed piers (relevant only for some codes like Chinese code JTG D62 or Russian code). In the ultimate limit check the stability factor is calculated in accordance with table 5.3.1. for determining the normal force capacity.

Note: The selective menu allows to select one of the above mentioned codes. The respective variable names are then automatically entered in the input fields for Eccentricity and Reduction factor.

Dataset parameters

Element series for which data is defined. Note that Step is currently disabled, only closed series with step 1 can be defined.

From, To, Step

Element series for which data is defined. Note that Step is currently disabled, only closed series with step 1 can be defined.

Direction

Switch, defining for which buckling direction the current definition will be effective. Note that not bending around this axis is meant, but buckling in this axis direction.

Note: Local x direction is only relevant for codes where a stability factor is used for calculating the compression force capacity.

Buckling length

Characteristic buckling length relevant for the elements of the defined series for calculating the slenderness parameters governing the additional eccentricity or stability factor.

Relevant depth of the cross-section in the respective buckling direction.

Default: total depth as stored in the database (Y1+Y2 or Z1+Z2 respectively),(internal variable CS_YZ).

Effective depth of the cross-section in the respective buckling direction.

Default: 0.85*H

Note: H and H0 are usually generated automatically from cross-section parameters in the database. For cases where you want to use deviating values, you may enter these values directly here.

Imperfection

Factor (nominal skew in Radians) in accordance with the code for calculating the additional eccentricity to be considered in the design procedure.

Default: no imperfection

Factor for min. ecc. (FACT_YZ)

Some design codes require additionally a minimum eccentricity to be considered. In ON B4700 this is 1/10 of the cross-section depth (formula 13: e_tot = e₀ + e_a +e₂ > h/10). The factor defined here relates to this requirement, i.e. if using the factor 1.0, then FACT_YZ*h/10 will be used as lower limit of the total eccentricity.

Default: 1.0

Note: In case of using user defined formulas the factor may be used in arbitrary manner for special additional conditions (name of the variable is FACT_YZ in the formulas for calculating the total eccentricity.

Creep factor

Effective creep ratio for calculating the relevant curvature used in the Eurocode formulas (EN 1992-1-1, eq. 5.37, 5.34).

Default: 2.0