Wednesday, 31 May 2017

Comparison of the effect of the different frame corner zone types

In ConSteel 11, an improved Frame Corner Wizard tool was introduced to be able to take into account the behavior of the different joint configurations in the structural analysis.


Four different frame corners can be used for the following beam-to-column moment joint typologies with. 7. DOF displacement is transferred accordingly.
Default frame corner
-
The value of 7. DOF is transferred but independently of the joint topology
Complete and indirect frame corner for BOX stiffened joints
The value of 7. DOF is equal on beam and column but the direction of 7. DOF is inverse on beam and column
Complete and direct frame corner for DIAGONAL stiffened joints
The value and direction of 7. DOF are equal on column and beam
Rigid against warping frame corner for BOX and additional diagonal stiffened joints
No 7. DOF transmission

To compare and evaluate the behavior of the different frame corners, two parallel simple portal frame models were built up from members and shells as well.


On the following figures the first eigenshape of the two parallel models can be seen. Behaviors are roughly the same.

Box stiffened joint
Shell model Member model

Diagonal stiffened joint
Shell model Member model


Comparison of the first eigenvalues shows that the results from the reference shell model and member model with different joint configuration are very close to each other.


Diagonal joint Box joint Box+diagonal stiffener joint
Shell model
6,10 5,96 6,48
Member model
with frame corner
wizard
6,40 6,00 6,76

Thursday, 11 May 2017

Practical notes about ConSteel's Tekla change management tool

In this post, practical notes are collected about the change management tool, which may come in handy when using it.

In general, the Change Management tool allows project team members to visually verify the modifications, deletions and new elements between the ConSteel and Tekla Structure models in ConSteel at any time.


Compatibility:

The tool is compatible with the following Tekla versions:
  • 19/19.1
  • 20/20.1
  • 21/21.1
  • 2016/2016i

Managing the changes:

It is important to know, that during the update process, ConSteel model is handled as the "strong" model. This means that after changes of the models, ONLY Tekla will be modified with the changes of the actual ConSteel model. 
Changes of the both Tekla and ConSteel models are represented with flags in the STATUS columns of the update dialogue. Each row represents a bar member, which is involved with some kind of change since the last update. There are 4 types of flags:
  • UNCHANGED - No change occured in Tekla or ConSteel model
  • CHANGED - Change in the Tekla and/or ConSteel model has occurred
  • DELETED - Bar member is deleted from Tekla and/or ConSteel model
According to these changes in the two models (Tekla & ConSteel), there can be 3 ways of the update process:
  1. Clear case, same modifications occurred on a member both in Tekla and ConSteel models. 
  2. Update case, when no further decisions are required from the user to perform the update. Covering the case when creating a new member in ConSteel, or modifying a member in consteel (which is unchanged in Tekla)
  3. Merge case, when decision is required from the user in the Conversion status column, which model status should be applied on the Tekla model (Tekla status or ConSteel status)
It is also important to know, that the Tekla model update dialogue will only appear in the Merge case.
If all of the changes can be handled with Clear case, and Update case, the update process is performed automatically, without bringing up the Update dialogue.

Additionally, it is good to know that in the table of the Update dialogue:

  • Members affected with Merge case are shown in the table and on the left side's Changes in Tekla part
  • Members affected with Update case are only represented on the left side's Changes in Tekla part
  • Clear case is not represented in the update dialogue at all

The following table shows the applied cases depending on the flags:

To see what kind of changes affecting the Tekla model, and how many members will be created, deleted or modified, the Changes of Tekla part of the update dialogue  can be checked.

  • On the top left corner, at the chart summarises the changed members compared with all  elements of the model.
  • Below the Changes in Tekla header change affected members are summarised in a numerical form


Filters:

With a double click on the header of each column, filters can be added to narrow down shown data of table. Applied filters will be represented on the bottom left side of the update dialogue.
These filters can be deleted easily if the "x" is clicked at the side of each filter 

Friday, 5 May 2017

Determination of shear field stiffness and application in ConSteel 11

Shear fields are used in daily practice in Germany for the design of structures by considering the stabilization effect of trapezoidal decking connected to bar elements. Such stabilization effect can be taken into account only when software with special bar elements with 7 degrees of freedom are used. In ConSteel 11 the possibility to consider shear fields at finite element level has been implemented.


Additionally several producer and standard specific methods to calculate the stiffness of a shear field have been included.



In this post we would like to provide general information about the included methods to calculate the stiffness of a given shear field.
At the end through a sample building the different calculation methodes will be introduced.

Determination of shear stiffness in case of panels produced by Hoesch [1]

The recommended method uses the following formula (DIN 18807, Schardt/Strehl method):

(1)

S: stiffness of the shear field [kN]
K1: parameter specific to the selected panel [m/kN]
K2: parameter specific to the selected panel [m2/kN]
L: length of the shear field parallel to the direction of the panel ribs [m]
a: applicable effective width [m]

Figure 1. shows the sketch of a general building showing the dimensions used in the previous formula. The method assumes that panels on all 4 edges along the boundary of the considered shear field are fixed to supporting structures with adequate spacing.

The values K1 and K2 have been specified by the producer for each panel type in function of its thickness. These values can be found on the website of the producer or in official application certificates.
Important to note, that such certificates have a certain validity of application, therefore it is always recommended to double check the validity of the values considered by ConSteel.

The S value determined with formula (1) is valid if the trapezoidal sheet is fixed at each rib to the supporting structure. The S value shall be multiplied with 0.2 in case of fixations in every second rib only.

Determination of shear stiffness in case of panels produced by Fischer [2]

The recommended method uses the following formula (improved Schardt/Strehl method) (2). The formula contains 3 additional parameters (K1*, K2* and eL) in comparison with the classical method, to consider the effect of the fixations of the panels.

 (2)

S: stiffness of the shear field [kN]
K1: parameter specific to the selected panel [10-4*m/kN]
K2: parameter specific to the selected panel [10-4*m2/kN]
K1*: parameter specific to the selected panel [10-4*1/kN]
K2*: parameter specific to the selected panel [10-4*m2/kN]
eL: distance between fixations lengthwise [m]
L: length of the shear field parallel to the direction of the panel ribs [m]
a: applicable effective width [m]

The method assumes that panels on all 4 edges along the boundary of the considered shear field are fixed to supporting structures with adequate spacing.

The S value determined with formula (2) is valid if the trapezoidal sheet is fixed at each rib to the supporting structure. The S value shall be multiplied with 0.2 in case of fixations in every second rib only.

Determination of shear stiffness in case of panels produced by Arcelor [3]

The recommended method uses the following formula (3) (Bryan/Davies method):

(3)

S: stiffness of the shear field [kN]
K1’: parameter specific to the selected panel [m/kN]
K2’: parameter specific to the selected panel [m2/kN]
K1*: parameter specific to the selected panel [1/kN]
K2*: parameter specific to the selected panel [m2/kN]
Ls: length of the shear field parallel to the direction of the panel ribs [m]
α1, α2, α3: additional parameters depending on the number of panel spans defined in tables
α4: additional parameter depending on the number of panel splices lengthwise
a: applicable effective width [m]

The method assumes that panels on all 4 edges along the boundary of the considered shear field are fixed to supporting structures with adequate spacing.

The S value determined with formula (3) is valid if the trapezoidal sheet is fixed at each rib to the supporting structure. The S value shall be multiplied with 0.2 in case of fixations in every second rib only.

Determination of shear stiffness according to Eurocode 3 [4]

The recommended method uses the following formula (4):

(4)

S: stiffness of the shear field [kN]
t: thickness of the panel [mm]
hw: depth of the panel [mm]
a: applicable effective width [m]
broof: length of the shear field parallel to the direction of the panel ribs (width of the roof) [mm]

The method doesn’t require that panels are fixed on all 4 edges along the boundary of the considered shear field are fixed to supporting structures. As a minimum fixation to directly stabilized structures (2 sides) with adequate spacing is required.

The S value determined with formula (4) is valid if the trapezoidal sheet is fixed at each rib to the supporting structure. The S value shall be multiplied with 0.2 in case of fixations in every second rib only.

Examples to determine shear field stiffness values

Parameters:

L=25 m (length of the shear field parallel to the direction of the panel ribs)
n=5 (number of frames)
a=5 m (bay spacing)
B=12 m (span)


The sample building is shown on Figure 2. In this building there are no purlins use, a deep corrugated trapezoidal decking is placed above the rafters. The complete roof of the building has been assumed to work as a shear field. In order to ensure this, the panels are fixed to the rafters and also to longitudinal beams located at the eaves. The panels are assumed to be connected over the ridge to form a continuous diaphragm with appropriate connecting elements (red lines). The panels are fixed at each rib to the supporting structure. It is important to note, that in such case the complete roof decking will have global stabilization role and therefore future changes such as additional openings can only be made in accordance with approval of a structural engineer.





Hoesch panel (Schardt/Strehl method)

Applied panel:
  • Hoesch T 135.1
  • 0.75 mm thick positive orientation, normal fixation

Extract of the table for the determination of additional parameters:

Values of parameters specific to the chosen panel from approval document:
  • K1=0,274 [m/kN]
  • K2=54,836 [m2/kN]
Stiffness value of the shear field applicable to an intermediate frame (fixation in every rib) (5):

 (5)

Reduced value when fixed at every second rib only (6):

 (6)

Stiffness value of the shear field applicable to an endwall frame (fixation in every rib) (7):

 (7)


Fisher panel (improved Schardt/Strehl method)

Applied panel:
  • Fischer 135/310
  • 0.75 mm thick positive orientation, normal fixation

Extract of the table for the determination of additional parameters:


Values of parameters specific to the chosen panel from above table:
K1=0,274 [10-4*m/kN]
K2= 55,589 [10-4*m2/kN]
K1*=3,763 [10-4*1/kN]
K2*=2,170 [10-4*m2/kN]


Stiffness value of the shear field applicable to an intermediate frame (fixation in every rib) (8):

 (8)

Reduced value when fixed at every second rib only (9):

 (9)

Stiffness value of the shear field applicable to an endwall frame (fixation in every rib) (10):

 (10)

Arcelor panel (Bryan/Davies method)

Applied panel:
  • Arcelor 135/310
  • 0.75 mm thick positive orientation, normal fixation



Values of parameters specific to the chosen panel from above table:
K1’= 0,277 [m/kN]
K2’= 48,560 [m2/kN]
K1*= 3,76 [1/kN]
K2*= 2,17 [m2/kN]

Extract of the table for the determination of additional parameters in case of continuous panel with 5 bays and 6 supports (rafters):
α1=0,6
α2=0,55
α3=0,71
The individual panels are 9.0 meters long, therefore 3 panels are applied longitudinally with overlap. This means that there are 2 panel splices along the length:
n’b: 2
α4=1,3+0,3*2=1,9 (11)

Stiffness value of the shear field applicable to an intermediate frame (fixation in every rib) (12):

 (12)

Reduced value when fixed at every second rib only (13):
 (13)

Stiffness value of the shear field applicable to an endwall frame (fixation in every rib) (14):

 (14)

Generic panel (Eurocode 3 method)

Applied panel:
  • Pruszinsky T-35 0.7
  • 0.70 mm thick, positive orientation, normal fixation

Stiffness value of the shear field applicable to an intermediate frame (fixation in every rib):


Stiffness value of the shear field applicable to an endwall frame (fixation in every rib):

 

Sources:
[1] Hoesch trapezprofil - Querschnitts und Bemessungswerte EN 1993-1-3 EC3, Produktionsstandardt Deutschland (http://www.hoeschbau.com/uploads/tx_downloads/436D_1114_Produktion-Deutschland.pdf)
[2] FisherTrapez, Typenprüfung Querschnitts und Bemessungswerte nach DIN EN 1993-1-3 (http://www.fischerprofil.de/dbfiles/FischerTRAPEZ-Q-B-02-2015%20i.pdf2015%20i.pdf)
[4] EN 1993-1- 3 10.1b