Bolted joints of rolled and welded steel I sections

INDEX

• Implemented design codes for bolted joints
• Types of implemented bolted connections
• Design options
• Prestressed and non-prestressed bolted connections
• Bolted connection design
• General properties
• Non-deformable bar ends
• Rotational stiffnesses at element ends
• Design criteria for prestressed bolted connections
• Joint consultation
• Bolted joints report
• Bolted joints drawings
• Other CYPECAD modules
• Other Metal 3D modules
• Related programs

Implemented design codes for bolted joints

The implemented codes for the analysis and design of bolted connections in CYPECAD, Metal 3D and Integrated 3D structures of CYPECAD are:

• CTE DB SE-A (Spain)
• Eurocode 3 EN 1993-1-8:2005 (General document)
• Eurocode 3 EN 1993-1-8:2005 (General document adapted to Portugal)
• Eurocode 3 NF EN 1993-1-8/NA:2007-07 (France – National application document)

Additionally, the bolt series codes which may be used are:

• Prestressed bolts
• ISO 7411
• ISO 7412
• EN 14399-3, HR System
• EN 14399-4, HV System
• Non-prestressed bolts
• ISO 4014
• ISO 4017

Types of implemented bolted connections

Column to beam bolted moment connection using front plate	Column to beam bolted moment connection using front plate with a simply connected orthogonal beam using lateral plate	Column to beam bolted moment connection using front plate with two simply connected orthogonal beams using lateral plates
Column to beam bolted moment connection with haunch using front plate	Column to beam bolted moment connection with haunch using front plate and simply connected orthogonal beam using lateral plate	Column to beam bolted moment connection with haunch using front plate and two simply connected orthogonal beams using lateral plates
Column to beam bolted moment connection using front plate (continuous column)	Column to beam bolted moment connection using front plate with a simply connected orthogonal beam using lateral plate (continuous column)	Column to beam bolted moment connection using front plate with two simply connected orthogonal beams using lateral plates (continuous column)
Column to beam bolted moment connection with haunch using front plate (continuous column)	Column to beam bolted moment connection with haunch using front plate and simply connected orthogonal beam using lateral plate (continuous column)	Column to beam bolted moment connection with haunch using front plate and two simply connected orthogonal beams using lateral plates (continuous column)
Column to two beam bolted moment connection using front plates	Column to two beam bolted moment connection with haunch using front plates and simply connected orthogonal beam using lateral plate	Column to two beam bolted moment connection with haunch using front plates and two simply connected orthogonal beams using lateral plates
Column to two beam bolted moment connection with haunches using front plates	Column to two beam bolted moment connection with haunches using front plates and simply connected orthogonal beam using lateral plate	Column to two beam bolted moment connection with haunches using front plates and two simply connected orthogonal beams using lateral plates
Column to two beam bolted moment connection using front plates (continuous column)	Column to two beam bolted moment connection using front plates and simply connected orthogonal beam using lateral plate (continuous column)	Column to two beam bolted moment connection using front plates and two simply connected orthogonal beams using lateral plates (continuous column)
Column to two beam bolted moment connection with haunches using front plates (continuous column)	Column to two beam bolted moment connection with haunches using front plates and simply connected orthogonal beam using lateral plate (continuous column)	Column to two beam bolted moment connection with haunches using front plates and two simply connected orthogonal beams using lateral plates (continuous column)
Column to beam bolted simple connection using lateral plate	Column to beam bolted simple connection using lateral plate and with a simply connected orthogonal beam using lateral plate	Column to beam bolted simple connection using lateral plate (continuous column)
Column to beam bolted simple connection using lateral plate and simply connected orthogonal beam using lateral plate (continuous column)	Beam to column web bolted simple connection using lateral plate	Beam to column web bolted simple connection using lateral plate (continuous column)
Continuous beam supported by column using simple lateral plate connection (beam web perpendicular to column web)	Column to two beam bolted simple connection using lateral plates	Column to two beam bolted simple connection using lateral plates (continuous column)
Bolted ridge connection using front plates	Bolted ridge connection with haunches using front plates	Beam to beam bolted simple connection using lateral plate
Beam to two beam bolted simple connection using lateral plates	Bolted splice connection of continuous equal sections with front plates

 

Design options

The design options for welded and bolted connections may be configured in the Options menu (Joints > Options). The dialogue box contains three tabs:

• Non-prestressed bolts
  Contains the design options for non-prestressed bolts (Bolt series code, Bolt steel class and Available diameters). Options selected here will only affect bolted connection design.
• Prestressed bolts
  Contains the design options for prestressed bolts (Bolt series code, Bolt steel class, Available diameters and Friction surface class). Contrary to what occurs with non-prestressed (ordinary) bolts, the bolt codes are exclusive (code recommendation). Additionally, the type of friction surface must be indicated to check the bolt for slipping. Within this dialogue, the program also defines the properties of the selected surface in accordance with the article of the selected code. Options selected here will only affect bolted connection design.
• Stiffeners
  Contains two option groups which configure the layout of the stiffeners:
• Stiffeners at haunch ends
  Contains two options which when activated force the program to always provide stiffeners, one in column to beam connections and the other in ridge connections. Affects welded connections designed with the Joints I module and bolted connections designed with the Joints II module.
• Stiffeners for beams fixed to the column web
  Activates the trimming of stiffeners for beams fixed to column webs. It only affects welded connections designed with the Joints III module (the other modules do not contemplate connections consisting of beams fixed to column webs).
  
  This option does not imply changes in the structural check but only takes into account aspects related to the aesthetics and with the number of trimming operations undertaken in the fabrication process. Upon activating the trimming option, it will be carried out if the following conditions are met:
• The smallest side of the trim has to be greater than 10mm.
• The angle formed between the inclined side of the trim and the plane perpendicular to the web has to be greater than 15 degrees.

Prestressed and non-prestressed bolted connections

CYPECAD, Metal 3D and Integrated 3 D structures of CYPECAD allow bolted connections to be designed using prestressed or non-prestressed bolts. This option is located in the Analysis menu (Analysis > Analyse) or in the joints design dialogue box (Joints > Analyse).

When the structure is analysed taking into account seismic effects, the program either recommends or imposes the use of prestressed bolts depending on the selected seismic code.  If the code states the use of prestressed bolts is obligatory, the program selects this option and does not allow for it to be deactivated. If the seismic code does not state it is compulsory to use prestressed bolts, the program reminds the user it is advisable to use these as is recommended by Eurocode 8.

When bolted connections are used, the program also indicates the friction surface class to be used in case that selected by the user in the design options is not adequate.

If the warnings are not taken into account by the user, it is possible for the prestressed bolted connection to not be designed by the program. In this case, when the user consults the joints after the analysis, the program indicates as errors the reasons why the design has not been carried out.

Bolted connection design

General properties

If during the analysis process of the structure, nodes are detected whose connection has been resolved in the program, they will be designed and detail drawings, 3D views, code check reports and take-off of these designs will be provided.

The program designs the dimensions of the plates and stiffeners, an optimum bolt arrangement and throat thicknesses of the welds required for the correct stress transmission in the connection.

The program designs the bolted connections using a front plate or a lateral plate:

• Moment connections using front plate. This type of solution is used by the program for fixed connections between beams and columns, for element splices and ridge beam connections.
• Simple connections using lateral plates. This type of solution is used by the program for pinned connections between beams and column webs or flanges.
• Simple connections using front plates. This type of solution is used by the program for beams supported at column ends forming a pinned connection.

Non-deformable bar ends

When welded or bolted connections are designed, or when the structure is analysed together with the joints, the program carries out, at each node of the job, the spatial layout of the bars and its fixity conditions in such a way that, for steel bars, the dimensions of the nodes are established and generates the rigid ends in which the portions of the bars are considered to not deform due to them being contained within the node.

Rotational stiffnesses at element ends

The program allows for fixity coefficients xy and xz or rotational stiffnesses to be assigned to bar ends (bars or set of aligned bars forming one element). Defining the rotational stiffness allows for the joints to be modelled and whereby their stiffness to rotate is fundamental to bear into account, as is in the case of bolted connections.

For each bolted connection that is designed, the program also analyses (for all the combinations of forces acting at the node) the rotational stiffness of each element fixed to the joint and selects a value for each element which will be proposed to the user for a re-analysis of the structure. The proposed stiffness will be the smallest amongst those calculated for each element, which corresponds to the one with the greatest positive or negative moment.

After the analysis and for elements fixed to the bolted connections, if the user has not defined the rotational stiffness or if the introduced value differs in more than 20% from that proposed by the program, a warning is emitted. This is also displayed as a warning in the report at the end of the analysis or in the option Show error messages in the Analysis menu.

Using the Rotational stiffnesses option in the Joints menu, the user can manage and substitute the values that were introduced instead of those proposed by the program (at the ends of elements with moment bolted connections provided by the program). This option activates a dialogue box with two possibilities:

• Check the assigned rotational stiffness values
  Displays the element ends whose rotational stiffnesses are adjusted to those proposed by the program in green; whilst those with a stiffness differing in more than 20% to that proposed by the program are shown in red.
  
  By placing the cursor over one of these element ends, the program displays a tag with the messages associated to that end and highlights in blue all the element ends of the structure that form part of the same type of connection and have the same rotational stiffness assigned to them.
  
  By selecting the end of the desired element, a dialogue box is displayed containing information on the type of fixity assigned to the end of the element and the rotational stiffness value proposed by the program, as well as the behaviour graph of the connection expressed by a moment-rotation curve.
  
  In this dialogue box, the original values can be maintained or modified. If they are modified, all the elements of the same type will be affected (those highlighted in blue when an end was selected). This dialogue box also contains a help button ( icon) in which the criteria followed by the program to obtain the rotational stiffness proposed by the user is thoroughly explained.
• Assign the proposed rotational stiffness value to all the elements
  Automatically assigns the rotational stiffness values proposed by the program to all the following element ends (only at elements ends fixed to bolted connections)
• Those whose introduced rotational stiffness differs in more than 20% to that proposed.
• Those for which the user has not indicated any rotational stiffness.

The program then allows to consult the element ends in the same way as is done using the Check the assigned rotational stiffness values option.



After assigning the rotational stiffnesses proposed by the program to the desired element ends, the structure must be reanalysed so the new force distribution due to the change in the rotational stiffnesses can be taken into account. The program emits a warning of this situation. 

Design criteria for prestressed bolted connections

The shear check in the transverse section of the bolts is substituted for an Ultimate Limit State (U.L.S.) slip check in the case of prestressed bolted connections and the tension and slip interaction is analysed.

When the user activates seismic action for the analysis of the structure, the fixed prestressed bolted connections are designed for Failure Mode 1, i.e., failure will occur due to plastic failure of the front plate of the connection and not due to bolt failure. Therefore, when the seismic action is taken into account, bolts are designed using greater diameters to guarantee enough rotation capacity.

Joint consultation

Following the analysis, the joints that have been designed by the program can be consulted.

Metal 3D and CYPECAD place different coloured circles at the nodes to indicate whether or not all the connections of the node have been designed, if there are only a few that have been designed or if the node does not contain any designed connections.

If the cursor is brought close to a node in which there are connections that have been designed, an information window will appear indicating the types of connections designed for that node. By clicking on the node a dialogue box with three tabs is displayed containing the following information:

• The construction details of the resolved connections
• A report of the checks and take-off of the resolved connections
• Real 3D views of the connections. It is possible to visualise a 3D view of each connection designed by the program with an isometric or conical perspective. The elements making up the joint (columns, beams, stiffeners, welds, bolts and plates) are drawn in different colours. Prestressed bolts and non-prestressed bolts are also represented in two colours to differentiate between them. The user may also freely rotate and amplify the 3D view. These characteristics greatly help the user to understand the assembly of the joint. The 3D view of the joints can be visualised by selecting the 3D view tab that appears in the bottom part of the window that is activated upon consulting the joint.

If the cursor is brought close to a node in which there are no designed connections, but belongs to one of the connections recognised by the program, a window appears informing of the causes that have prevented that joint from being designed.

Bolted joints report

Metal 3D and CYPECAD generate a joints report with the following data:

• Welded connection specifications
• Code
• Materials
• Construction layout
• Checks
• Bolted connection specifications
• Code
• Materials
• Construction layout (includes conditions and possible fastening methods of prestressed bolts)
• Checks
• References and symbols
• Baseplate checks
• Relationship of reported joints
• Calculations
• Construction detail of each type of joint
• Description of the components of each type of joint
• Check results of each type of connection
• Weld, plate and bolt take-off for each connection type
• Complete take-off of welds, plates and bolts of the designed joints

Bolted joints drawings

The construction details of the joints designed by the program can form part of the drawings of the structure. The Joints drawings include the following elements:

• Construction detail of the joint
• Schedule with specifications of the welds in steel structures
• Code
• Materials
• Construction layout
• Fastening procedure of prestressed bolts
• Checks
• Reference and symbols table
• Complete take-off of welds, plates and bolts of the designed joints

Other CYPECAD modules

• Concrete columns
• Concrete beams
• Steel columns
• Steel beams
• Joist floor slabs (generic concrete joists)
• In-situ, prefabricated and steel joist floors (Joist floor module required)
• Waffle slabs
• Flat slabs
• Composite slabs
• Hollow core slabs
• Shear walls
• Reinforced concrete walls
• Stairs
• Mat foundations and foundation beams
• Concrete block walls
• Pile caps (includes strap and tie beams)(*)
• Pad foundations (isolated and combined) (includes strap and tie beams)(*)
• Baseplates(*)
• Automatic job introduction
• Aluminium sections
• Timber sections
• Joints I. Welded. Warehouses with rolled and welded steel I sections
• Joints II. Bolted. Warehouses with rolled and welded steel I sections
• Joints III. Welded – Building frames with rolled and welded steel I sections
• Export to Tekla
• Export to TecnoMETAL
• Export to in CIS/2 format

(*) Common modules: Pile caps, Pad foundations and base plates are operative for both CYPECAD and METAL 3D.

Other Metal 3D modules

• Footings

Includes the analysis and design of reinforced or mass concrete footings. These can be square, rectangular, eccentric, corner or edge centred. This a common module for Metal 3D and CYPECAD.

• Pile Caps

Analyses and designs pile caps for multiple piles. A wide range of types are available. They may hold 1, 2, 3 and 4 piles; linear and rectangular pile caps for any number of piles; pentagonal pile caps for 5 and 6 piles, and hexagonal for 6 and 7 piles. Includes the analysis and design of strap and tie beams. It is a common module for Metal 3D and CYPECAD.

• Baseplates

Designs baseplates for any steel column arrangement (simple and composed sections). This a common module for Metal 3D and CYPECAD.

• Timber sections

Analyses and designs rectangular (constant or variable) and circular section bars. They may be composed of sawn wood (conifer and poplar species), sawn wood (frondescent species), homogenous glue laminated wood and combined glue laminated wood. It also carries out a fire resistance check.

• Joints I. Warehouses with rolled and welded steel I sections

Analyses and designs welded connections of I sections according to CTE. DB SE-A code and Eurocode 3 of various types.

• Joints II. Bolted. Warehouses with rolled and welded steel I sections

Designed to carry out an automatic analysis and design of I section bolted connections using prestressed or ordinary bolts (non-prestressed) displayed in the Types of implemented bolted connections.

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