g2 = f2 Application range:
PROF 1 HEB 300 PROF 2 HEB
3.42. BEAM − Beam Elements
ÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄ
BEAM
Item Description Dimension Default
NO NA NE NR NCS AHIN EHIN DIV NBD NP NCSE Element number
Number of start beam node Number of end beam node Direction data of Y−axis
(parameter omitted by plane systems) Cross section number
Input of hinge at start node Input of hinge at end node
Partitioning of beam into DIV (<50) equal segments with the same cross sec tion number
Number of segment definition Geometry or foundation number Cross section number at beam end
− − − LIT/ degrees − −/LIT −/LIT − − − − ! ! ! 0 1 * * 1 − − NCS A beam element is defined through two nodes and a sectional description (NCS/NCSE). The records SUPP, BSEC and ADEF/BDIV can be used to de scribe any desired variation of cross section. In this case it is to be ensured no rotation of the main axis is allowed along the beam axis.
A uniform partitioning can be defined by DIV in case of prismatic beams. If a negative DIV is input, the segments acquire the attribute PRIN NO (see
ADEF). With haunched beams definition of sections are necessary for every beam section.
The input of a beam record with a negative element number causes the dele tion of a previously defined element. If a cross section number is additionally
3−109
Version 10.20input, the cross section is simply changed instead. A subsequent definition of haunches is no more possible in such case.
By AHIN and EHIN one can either enter the number of a hinge combination that has already been defined with HING or enter directly up to two of the following hinge support conditions (without spaces in between):
N VY VZ MT MY MZ MB (Default: no hinges)
A pile element whose attributes with the profile or the GLN NP are defined is made by input of NP > 0. If NP is −1 a referenced beam element is generated. The axis of the beam is then the connection of the origin of the sectional coordinate system!
Beam coordinate system
Each beam or pile has a local system of coordinates x, y, z (refer to section 2.2). The longitudinal axis of the beam NA−NE defines the positive x−direction. The following cases can be distinguished regarding the orientation of the other two axes:
1. Plane frame
The structure lies in the global XY−plane. The local y−axis of the beam is par allel to the global Z−axis but in the opposite direction. The local z−axis is per pendicular to the axis of the beam and to the right of the direction of the beam.
2. Gridwork
The structure lies in the global XY−plane. The local z−axis is parallel to the global Z−axis. The local y−axis is perpendicular to the axis of the beam and to the right of the direction of the beam.
3. Space frame
In a three−dimensional system the orientation of the local y−axis must be de fined by the user. The parameter NR is available for this purpose. The local z−axis is perpendicular to the local x− and y−axes. Its direction is determined by the three−finger right hand rule.
The following possibilities exist: 3.1. NR=0 (Default)
The local y−axis is parallel to the global XY−plane and perpendicular to the axis of the beam, thus to the right of the direction of the beam. This is inde pendant of the gravity direction always clockwise with respect to the global Z−axis.
3−111
Version 10.20Standard orientation
In case the axis of the beam is parallel to the global Z−axis, then the local z− axis is parallel to the global y−axis.
Special cases of orientation 3.2. NR negative (<0)
A negative value for NR is interpreted as an angle in degrees, by which the coordinate system resulting from NR = 0 (refer to 3.1) must be rotated about the axis of the beam. (A negative value is an angle rotating to the left, a posi tive value is a direction node!)
Rotation of cross section 3.3. NR positive (>0)
A positive value for NR is interpreted as a reference node. The local y−axis lies in a plane defined by the nodes NA−NE−NR. Therefore, NR can not lie on the straight line NA−NE.
Direction node
If a non−integer number is input for NR, its decimal part, multiplied by 1000, is interpreted as additional negative rotation of the beam coordinate system
3−113
Version 10.20about the beam axis in degrees. Thus, 5.090 rotates the z−axis in the plane defined by node 5.
3.4. NR as a literal
If one of the literals XX, YY, ZZ, NEGX, NEGY or NEGZ is input for NR the local y−axis will be placed on a plane defined by the axis of the beam and the coordinate axis corresponding to that literal.
Haunches and sections
Beams can have segments and variable cross sections. Not all of the programs though can take into consideration all the effects resulting from that. One must occasionally settle with an average value (e.g. rotation of the principal axes or shear center).
Haunches can be defined in simple cases by a special input format for NCS. Namely, if a decimal number is entered for NCS (e.g. 1.02), the two decimal digits define the cross section at the end of the beam element (1.2 describes cross sections 1 and 20!). The parameter NCSE must be used in case of three digit cross section numbers.
The user generally has a whole range of input options. Combinations are al lowed, but duplicate section definitions are usually ignored.
1. Input of DIV
The beam is partitioned into an integer number of parts. Each sec tion acquires the cross section number of its predecessor. Beams with haunches therefore can not be partitioned this way.
2. ADEF and BDIV can define a pattern of segment lengths and cross section numbers, which can be suited upon several beams through a scaling of the individual segment lengths or the sum of them. Cross section jumps can be solely defined by means of this method.
3. Input of SUPP
The use of SUPP generates the sections that are usually necessary for a check (edge of support and critical section for shear).
4. Input of BSEC
It can be used for explicit section definitions.
The output or the proportioning of internal section forces is usually possible only for cross sections specified by a segment definition or a partitioning. For nonlinear analysis it is necessary to define a large number of sections.
All sections can include additional information for controlling the processing of the sections during the proportioning and the static analysis. Two para meters are provided for this purpose:
STYP Typ des Schnitts
ABSC Normaler Schnitt
ANSC Anschnitt eines biegesteifen Anschlusses
AGEL Anschnitt eines Auflagers mit gelenkigem Anschluß (Mauerwerk)
AIND Anschnitt eines indirekten Auflagers
SCHU Für die Schubbemessung maßgebender Schnitt STYP Type of section
SECT Regular section
FACE Section at the face of a clamped connection HFAC Section at the face of a support with articulated
connection (masonry)
IFAC Section at the face of an indirect support SHEA Critical section for shear proportioning
and
PRIN Ausgabekategorie des Schnittes
JA Schnitt wird immer ausgegeben
NEIN Schnitt wird nur gedruckt, wenn eine entsprechende
ECHO−Option gesetzt ist. PRIN Output category of the section
YES Section data will be output always
NO Section data will be output only when a corresponding
ECHO−option is set. RICH Richtung von STYP
HAUP Hauptrichtung (Vz,My) QUER Querrichtung (Vy,Mz) VOLL Beide Richtungen
3−115
Version 10.20DIRE Direction of STYP
MAIN Principal direction (Vz,My) TRAN Transverse direction (Vy,Mz) BOTH Both directions
ORT Lokalisierung des Schnitts
ANFA zum Stabanfang gehörend ENDE zum Stabende gehörend LOC Localization of the section
BEG belongs to beginning of beam END belongs to end of beam
An assignment of the section to the beginning or the end of the beam is necess ary for support sections, when these lie on the wrong side with respect to the midpoint of the beam. This is, for example, a case when a beam should be subdivided into more elements. The ’beginning’ then of the third beam el ement could lie short of the beams end.
See also: BDIV, BEAM, BSEC