Chapter Steel Connection Design - Ahmed Mansourahm531.com/Prokon and EQ course/Prokon Manual/Chap-05.pdf · Chapter Steel Connection Design The steel connection design modules can

Steel Connection Design 5-1

Chapter

Steel Connection Design

The steel connection design modules can be used for design of common welded and bolted steel connection.

Steel Connection Design 5-2

Quick Reference

Steel Connection Design using PROKON 5-3 Base Plate Design 5-5 Moment Connection Design 5-15 Hollow Section Connection Design 5-24 Shear Connection Design 5-Error! Bookmark not defined. Simple Connection Design 5-43

Steel Connection Design using PROKON 5-3

Steel Connection Design using PROKON

The PROKON suite includes several design modules for typical steel connections.

Shear connections Bolt groups and weld groups can be designed for eccentric in-plane shear.

Moment connections The following types of moment transmitting connections can be designed:

• Stiffened and unstiffened column base plates.

• Bolted and welded beam-column connections with or without haunches.

• Bolted or welded apex connections with or without haunches.

Axial force connections Welded hollow section connections can be designed for typical trusses, included triangulated space trusses.

Simple connections Simple beam to column connections that do not transmit moments:

• Web angle cleat connections.

• Flexible end plate connections.

• Fin plate connections.

Steel Connection Design using PROKON 5-4

Base Plate Design 5-5

Base Plate Design

The Base Plate Design module designs column base plates subjected to axial force and bi-axial moment. Both stiffened or unstiffened base plates can be designed. Base plates can bear on concrete or grout or can be supported on studs. Detailed drawings can be generated for editing and printing using the PROKON Drawing and Detailing System, Padds.


Theory and application

A brief discussion of the application of the theory is given below.

Design scope and assumptions The program can analyse column base plates that carry axial force and bi-axial moment. The following assumptions are made:

• The effective applied column force and moment is applied to the base plate as a point load in the flanges and a uniform distributed load in the webs of the approximated section.

• The application of the axial force as uniform distributed load in the webs serves as a mechanism to model the stiffening effect of the webs on the base plate.

• The case of bi-axial bending is simplified by transforming the moments to an effective design moment about one axis. Given the interaction between the base plate and the concrete bearing surface, the clauses of the concrete design codes for bi-axially bent concrete columns are deemed reasonable for this purpose.

• The base plate is analysed as a beam on an elastic support. The resulting concrete bearing stresses or stud forces are applied to the base plate during its analysis.

• Unstiffened base plates are analysed using elastic theory. A rectangular perimeter that encloses the column cross-section is considered and the bending stress in the base plate evaluated on each of its four sides. The required base plate thickness is calculated by limiting the bending stress on each of the lines that extend from edge to edge and passing over a side of the rectangle.

• Stiffened base plates are analysed using yield line theory. Since this is an upper bound method, allowable stresses are reduced by 20%.

• The interaction between the base plate and supporting concrete or grout layer is taken in accordance with the relevant code. When using BS 5950 - 1990, the parabolic stress-strain relationship given in BS 8110 - 1997 is used. Similarly, the parabolic relationship given by SABS 0100 - 1992 is used when designing the base plate using SABS 0162 - 1993 and CSA A23.3 – M89 for CSA S16.1 - 1989. In the case of allowable stress design to SAB 0162 - 1984, a linear stress-strain relationship is assumed.


Design codes The program designs axially loaded steel members according to the following design codes:

• BS 5950 - 1990.

• CSA S16.1 - M89.

• SABS 0162 - 1984 (allowable stress design).

• SABS 0162 - 1993 (limit state design).

Symbols Where possible, the same symbols are used as in the design codes:

General design parameters

a1 : Distance from the left edge of the base plate to the centre line of the bolts (mm).

a2 : Distance from the right edge of the base plate to the centre line of the bolts (mm).

a3 : Distance from the bottom edge of base plate, as shown on the screen, to the centre line of the bolts (mm).

a4 : Distance from the top edge of base plate, as shown on the screen, to the centre line of the bolts (mm)

bg : Bolt grade, e.g. 4.8.

B : Width of the column flange (mm).

D : Overall depth of the column (mm).

fcu : Cube strength of bedding concrete or grout (MPa).

L : Length of the base plate (mm).

L1 : Distance from the left edge of the base plate to the column flange (mm).

Studs : Enter ’Y’ if the bolts are used as studs, i.e. the base plate transmits all tension and compressions forces to the bolts. Enter ’N’ to transmit compression forces to the bedding concrete or grout.

W : Width of the base plate (mm).

W1 : Distance from the top edge of the base plate, as shown on the screen, to the corner of the column flange (mm).


Stresses, forces and related entities

C : Design compression force in the connection (kN).

T : Design tensile force in the connection (kN).

BS 5950-1990:

Pu : Ultimate design axial force in the column (kN). A positive value is taken as a downward force and negative value as an uplift force.

Mux : Ultimate design column moment applied about the X-axis (kNm).

Mux : Ultimate design column moment applied about the Y-axis (kNm).

Ys : Yield strength of steel (MPa).

Us : Ultimate strength of weld (MPa).

SABS 0162 - 1984:

P : Working design axial force in the column (kN). A positive value is taken as a downward force and negative value as an uplift force.

Mx : Working design column moment about the X-axis (kNm).

My : Working design column moment about the Y-axis (kNm).

fy : Yield strength of steel (MPa).

fw : Strength of weld (MPa).

CSA S16.1 - M89 and SABS 0162 - 1993:

Pu : Ultimate design axial force in the column (kN). A positive value is taken as a downward force and negative value as an uplift force.

Mux : Ultimate design column moment applied about the X-axis (kNm).

Mux : Ultimate design column moment applied about the Y-axis (kNm).

fy : Yield strength of steel (MPa).

fuw : Ultimate strength of weld (MPa).


Input

Define the beam and column connection geometry by entering the relevant information in the input table.

Column dimensions To read a column section from the section database, select the section type and choose a profile. For non-standard sections such as plate girders, you can enter the relevant dimensions.

Tip: To move the column to the centre of the base plate, use the Centralise Column function.

Forces acting on the connection Enter the forces transmitted from the column to the base plate using the sign conventions given in the list of symbols. The entered forces are multiplied by the entered load factors to obtain the design forces.


Special configurations You can model some special configurations:

• The bolts can be moved inside the column flanges by sufficiently increasing the values of a1 and a2.

• Use a negative column load to model an uplift force.

• The input table allows you to change the bolts to studs, i.e. transfer the column loads in the bolts rather than support the plate on the bedding concrete.


Design

The base plate connection is designed twice, with and without plate stiffeners.

Calculation of design forces acting on the connection The entered column moments are converted to an effective moment about one axis. The moment and axial force is then applied to the base plate via the column flanges. For a design moment about the X-axis, a point load is applied at each of the two column flanges. If the design moment works about the Y-axis, a trapezium-shaped distributed force is applied over the width of the flanges.

Analysis of the base plate In the case of the base plate bearing on concrete or grout, the plate is analysed as a beam on elastic foundation. The resulting bearing stresses are then used to calculate the moment in the base plate and the base plate thickness. This approach is slightly conservative due to stiffening effect of the column web being neglected.


The unstiffened base plate thickness is calculated using normal elastic theory. For a stiffened base plate, however, the required plate thickness is determined using yield line theory. If tensile forces are dominant, the number of bolts used also influences the plate thickness.

Analysis of the bolts In the case of the base plate bearing on the concrete or grout, the bolts are designed to resist tensile forces only. For the case where the bolts are used as studs, the bolts are designed to resist the full compressions and tension forces. It is then assumed that there is no bearing stress on the concrete or grout.


Calcsheets

The base plate connection design output can be grouped on a calcsheet for printing or sending to Calcpad. Various settings can be made with regards to the inclusion of design results and pictures.

Tip: You can embed the Data File in the calcsheet for easy recalling from Calcpad.

Recalling a data file If you enable the Data File option before sending a calcsheet to Calcpad, you can later recall it by double-clicking the relevant object in Calcpad. A data file embedded in Calcpad is saved as part of a project and therefore does not need to be saved in the connection design module as well.


Drawing

Detailed drawings can be generated for designed connections. Drawings can be edited and printed using Padds.

Generating a drawing Based on your initial input and the design results, initial values are chosen for the dimensions. Change the values to suite your special requirements.

Required information:

• Drawing file name: Name of the Padds drawing file.

• Drawing scale to use.

• Connection properties:

• Plate thickness.

• Stiffener size.

• Weld sizes.

• Bolt and hole sizes and quantities.

Press Generate to create a Padds drawing with the entered settings.

Moment Connection Design 5-15

Moment Connection Design

The moment connection design modules are suitable for the design of the following connections:

• Beam-column connection, BeamCol: Beam connected to the flange of a column.

• Apex connection, Apex: Symmetrical beam apex with end plates.

The connections incorporate beams and columns made of I and H-sections.



The following text gives a brief background of the application of the design codes.

Design scope The moment connection design modules can analyse connections that transmit shear, moment and axial force. Only forces in the plane of the connection are considered, i.e. vertical shear, axial compression or tension and in-plane moment. The connections may be bolted or welded.

The following assumptions are made:

• The centre lines of the connecting beams or beam and column are in the same plane.

• All bolt holes are normal clearance holes.

• Bolts have threads in their shear plane.

• Connections are deep enough for each section’s flanges to resist the prevailing compressive and tensile forces.

• Compressive forces in the flanges and stiffeners are transmitted through the welds and not through bearing.

The following additional assumptions apply to BeamCol:

• Any axial force in the column is ignored.

• Longitudinal and transverse welds in the web plates are full size butt welds.

Codes of practice The following codes are supported:

• AISC - 1993 LRFD.

• BS5950 - 1990.

• CSA S16.1 - M89.

• Eurocode 3 - 1992.

• SABS0162 - 1984 (allowable stress design).

• SABS0162 - 1993 (limit state design).

Units of measurement Both Metric and Imperial units of measurement are supported.


Sign conventions The loads are defined as the forces transmitted by the right-hand side beam onto the connection:

• A positive axial force is taken as a compression force.

• A positive moment corresponds to a tensile force in the top flange of the beam.

• Downward shear is taken as positive.

Tip: Positive loads on the connection correspond to the directions of forces in a typical single bay portal frame subjected to dead and live load.

List of symbols Where possible the same symbols are used as in the design codes. The meanings of the symbols are clear from their use in the design output.

Analysis of bolted moments connections When moments are transferred by bolted connections the bolts are loaded in tension (and shear). The programs allow you to use an elastic or plastic method of analysis for determining the bolt forces:

• With an elastic analysis, the bolt furthest from the compression flange will have the largest tensile force. Forces load will reduce linearly in bolts closer to the compression flange.

• In the case of a plastic analysis, all the bolts have the same force.

Prying action

In moment connection, prying action can be prevalent. The prying forces and method of failure depend on the layout of the design, the thickness of the plate or flange in question and the strength of the bolts.

A yield line analysis method is used to calculate three resistance values for each relevant portion of the connection:

• Plate yielding at the web and the bolts.

• Plate yielding at the web and bolt failure.

• Bolt failure only.

The smallest of the three resistance values is taken to be the ultimate resistance.


Input

The moment connection design modules use a similar procedure for data entry:

• Members: Set the connection type and properties of the beams or beam and column.

• Setting: Select the connection type and main design parameters.

• Loads: Enter the loads applied to the connection.

Members Define the type of connection and the design parameters:

• Define the connection type by selecting an end plate configuration, e.g. no end plate, end plate flush at the top and bottom of the beam or extending at the tope and/or bottom.

• Beam and column designations.

• Inclination of the beam.

• Haunch depth and length. If either value is zero, no haunch is used.

Settings

Use Settings to set the bolt, weld and member material properties:

• Select between elastic and plastic analysis of bolts in tension. The analysis mode determines the distribution of the bolt forces. See page 5-17 for detail.

• Enter a bolt type, grade and diameter. For high strength friction grip bolts, additional information needs to be supplied with regards to the analysis method.

• Enter the strength properties of the beam, column and connection members.

• Specify the weld strength.

Note: If you need to modify the available bolt grades or bolt sizes, edit the General Preferences from the Settings menu in Calcpad.


Loads Enter any number of load cases. For each load case:

• Use a maximum of six characters to enter a descriptive load case name or load case number, e.g. ’Dead’, ’DL + LL’ or ’1’.

• Specify the axial force, shear force and moment that the right-hand side beam exerts on the connection.

• The SLS factor is divided into the entered ULS loads to obtain service loads.

Note: All entered loads should be ULS loads. The corresponding SLS loads are obtained by dividing the entered ULS loads by the SLS factor. The SLS factor should thus be set equal to the relevant ULS load factor divided by the SLS load factor.


Design

The design table lists all variable dimensions and parameters of the connection. A value for any property in the table can be calculated using the Optimise function. You can also selectively fix values for any individual properties to suite your preferences:

• Select values for all properties that should have specific values. To obtain a specific bolt layout, for example, enter preferred values for the bolt offsets.

• Set the values of all other properties to "Optimise".

• Click Optimise to calculate values for the latter.

Tip: For a table summarising the design results, go to the Calcsheet page.


After optimisation, you should evaluate each of the values calculated by the program. You are then free to refine the results by selectively entering more appropriate values. After adjusting some values, you may wish to optimise some of the other values again.

Note: Several valid design solutions are possible for any particular connection. The optimised results calculated by the programs should be regarded as one such solution.


Calcsheet

Open the Calcsheet page to view the detailed design calculation. The information on the can be printed or sending to Calcpad. Various settings can be made to include input data, tabular design summaries and the complete design calculations.


Recalling a data file The Data File can be included when sending a calcsheet to Calcpad. You can later recall the data file by double-clicking the relevant object in Calcpad. A data file embedded in Calcpad is saved as part of a project and therefore does not need to be saved in the connection design module as well.


Drawing

Detailed drawings can be generated for designed connections. Drawings can be edited and printed using Padds.

Printing or saving a drawing A drawing is displayed using the dimensions of the final design. To save or print the drawing to disk, use the buttons next to picture. Drawings can be saved a variety of formats, including Padds and DXF formats.

Hollow Section Connection Design 5-24

Hollow Section Connection Design

The Hollow Section Connection Design module does a complete design of welded structural hollow section connections. The connecting members may transmit axial force and can be circular, square or rectangular hollow sections. I-sections and H-sections can also be used for the main chord.



The program designs structural hollow section connections that transmit axial forces. Various connection layouts can be designed. These include K, T, N, X, and Y joints and combinations thereof.

Design codes The program designs according to recommendations given in Annex K of Eurocode 3 - 1992.

Symbols Where possible, the same symbols and sign conventions are used as in the design codes:

Section dimensions

bi : Width of a section (mm or inches).

hi : Height of a section (mm or inches).

hw : Web height of an I-section or H-section (mm or inches).

i : Section number. The main chord is identified by i = 0 and the left, right and centre chords by i = 1 to 3 respectively.

ro : Radius between the web and flange of an I-section or H-section (mm or inches).

ti : Thickness of a section, i.e. wall thickness of a hollow section or flange thickness of an I-section or H-section (mm or inches).

tw : Web thickness of an I-section or H-section (mm or inches).

Joint geometry

g : The clear gap between bracing as measured member on the chord surface (mm or inches). A negative value denotes an overlap.

Symmetry : Enter ’Y’ to make an X-joint symmetric, i.e. mirrored about the main chord. If you enter ’N’, bracing members continue along their axes to the other side of the main chord.

X-joint : Enter ’Y’ to put bracing elements on both sides of the main chord, i.e. an X-joint. This option can only be used in combination with K, N and T joints where a circular hollow section is used as the main chord. Enter ’N’ for bracing members on one side of the main chord only.


φ : Out-of-plane separation angle between two sets of bracing members (°). The angle must lie between 60° and 90°. This option is useful when modelling joints in triangulated trusses. If this option is used, all setting relating to X-joints are ignored. Leave this field blank if you do not want to use this option. The option can only be enabled when a circular hollow section is used as main chord.

θ1 : Angle between the main chord and the left bracing member (°). The angle must be between 30° and 90°.

θ2 : Angle between the main chord and the right bracing member (°). The angle must be between 30° and 90°.

θ3 : Angle between the main chord and the centre bracing member (°). The angle must be between 30° and 150°. The angle must also by greater than θ1 and smaller than (180° - θ3).

Forces and stresses

Es : Modules of elasticity of steel (GPa or Mpsi).

fy : Yield strength of main chord or bracing members (MPa or ksi).

N0 : Ultimate axial force in the main chord (kN or kip). A positive value denotes a compression force.

N1 : Ultimate axial force in the left bracing member (kN or kip). A positive value denotes a compression force.

N2 : Ultimate axial force in the right bracing member (kN or kip). A positive value denotes a compression force.

N3 : Ultimate axial force in the centre bracing member (kN or kip). A positive value denotes a tensile force.

Units of measurement Both Metric and Imperial units of measurement are supported. When changing from one system of units to another, the program automatically converts all input data.


Input

The definition of the connection requires you to enter geometrical and loading data.

Chord and bracing sections Click Section Database to read a chord or bracing section from the section database. The main chord can be an I-section, H-section or a circular, square or rectangular hollow section. You can use circular, square or rectangular hollow sections as bracing members.

The following general guidelines apply when defining bracing members:

• You should define at least one bracing member.

• A single bracing member should be entered as either the left or right bracing member.

• The centre bracing member can be defined only after defining both the left and right bracing members.

• X-joints can be defined only if the main chord is a circular hollow section.

• X-joints can be made symmetric by enabling the relevant option in the table.

• A separation angle for a 3D joint can only be used if the main chord is a circular hollow section.

Tip: Use the 3D rendering option to view and rotate the connection in 3D.


Forces acting on the connection Enter the forces in each member using the sign conventions displayed in the picture. With the exception of the right bracing member, positive forces work in compression towards the centre of the connection.


Design

The design checks are performed as prescribed in the code, including the following:

• Geometrical evaluation of the connection to ensure compliance with the design codes.

• Checking the main chord for plastification.

• Checking punching shear of the main chord.

• Design of welds.


Calcsheet

The connection design output is given on a calcsheet. You can choose to print the information immediately or rather send it to Calcpad.

Tip: The Data File embedded in the calcsheet can be used for easy recalling of the design from Calcpad.

Recalling a data file The Data File is automatically included when sending a calcsheet to Calcpad. You can later recall the data file by double-clicking the relevant object in Calcpad. A data file embedded in Calcpad is saved as part of a project and therefore does not need to be saved in the connection design module as well.

Shear Connection Design 5-31

Shear Connection Design

The shear connection design modules are suitable for the design of the following connections:

• Bolt Group Design, Boltgr: Eccentrically loaded bolt groups.

• Weld Group Design, Weldgr: Eccentrically loaded weld groups.



When a bolt group or weld group is loaded in its plane and the load does not work through the centroid of the group, additional shear forces are caused in the bolts or welds. The shear connection design modules calculate the maximum resistance of bolt and weld groups.

The modules also determine the smallest bolt or weld size that can be used to resist an in-plane force with arbitrary orientation. In the case of bolt groups, both the cases of single and double shear can be considered.

The groups are analysed using either linear or non-linear strength relationships.

Design codes The programs support the following design codes:

• BS 5950 - 1990.

• CSA S16.1 - M89.


• SABS 0162 - 1984 (allowable stress design).

• SABS 0162 - 1993 (limit state design).

Symbols Where possible, the same symbols are used as in the design codes:

Bolt group geometry

d : Bolt Size.

a1 : Horizontal bolt spacing

a2 : Vertical bolt spacing

nr : Number of rows of bolts in the group.

nc : Number of columns.

Material properties

fu : Ultimate strength of steel or weld.

fy : Yield strength of steel.


Applied loads

F : Force.

x : Force horizontal eccentricity

y : Force vertical eccentricity

β : Force angle

Units of measurement Both Metric and Imperial units of measurement are supported. In addition, you can also choose between units within the selected system, e.g. between mm and cm.

Analysis principles The program designs bolt groups and fillet weld groups subjected to eccentric shear using either linear or non-linear strength relationships.

Linear analysis

Eccentrically loaded fastener groups are usually analysed by considering the group areas as an elastic cross-section subjected to direct shear and torsion. Assuming elastic behaviour, the group’s centre of rotation is taken as the group’s centroid. The deformation of each fastener is then assumed proportional to its distance from the assumed centre of rotation.

The elastic method has been popular because of its simplicity and has been found conservative. Salmon and Johnson1 quotes the ratio between actual strength and service loads to be in the range of 2.5 to 3.0.

Non-linear analysis

The non-linear method, also called plastic analysis or instantaneous centre of rotation method, assumes that the eccentric load causes a rotation as well as a translation effect on the fastener group. The translation and rotation is reduced to a pure rotation about a point defined as the instantaneous centre of rotation.

Similar to the linear method, the deformation of each fastener is taken proportional to its distance from the instantaneous centre of rotation. The load in each fastener is however

1 C. G. Salmon and J. E. Johnson, "Steel Structures, Design and Behaviour", Third Edition (1990), Harper Collins Publishers.


determined using the non-linear strength expression proposed by Fisher2 and used by Crawford and Kulak3:

( ) 55.0101 ∆−−= eRR ulti

The relationship assumes a bearing-type connection and ignores slip. The coefficients 10 and 0.55 were experimentally determined. For the given experimental setup, the maximum deformation, ∆, at failure was about 0.34 inches (8.6 mm).

Salmon and Johnson1 conclude that the plastic analysis method is the most rational approach to obtain the strength of eccentric shear connections.

Application of the non-linear strength relationship

For the purpose of its application in the connection design modules, the strength relationship has been normalised and rewritten:

( ) 55.04.31018.1 ∆−−= eRnorm

The capacity of a fastener group is governed by the yield of the fastener furthest from the instantaneous centre of rotation.

Taking the deformation at that point as unity, the normalised deformations for the other fasteners are determined using linear variance. The force of each fastener is calculated using the strength relationship.

Non-linear analysis of weld groups

Although the load-deformations characteristics of fillet welds depend on the direction of loading, current design codes generally use a lower bound approach based on the longitudinal strength, irrespective the actual loading direction. An expression developed by Lesik and

2 J. W. Fisher, "Behaviour of Fasteners and Plates with Holes", Journal of the Structural Division, ASCE, 91, STD6 (December 1965). 3 S. F. Crawford and G. L. Kulak, "Eccentrically Loaded Bolted Connections", Journal of the Structural Division, ASCE, 97, ST3 (March 1971).


Kennedy4 can be used to determine the ultimate strength of fillet welds loaded in any direction.

Assuming that the resistance for compression and tension-induced shear is the same, the resistance of a weld element for the calculated angle of loading is given by:

( )( )0.1sin5.0 5.1 += θθ uRR

where

Ru = Ultimate strength of a fillet weld loaded with longitudinal shear

Rθ = Resistance of a fillet weld when the loading angle equals θ.

The relationship was determined empirically and implies the resistance in a weld element will vary between 1.0⋅Ru for longitudinal shear and 1.5⋅Ru for transverse shear.

Application of non-linear method

The program divides the weld group into a discrete number of finite weld elements. When performing a non-linear analysis, the instantaneous centre of rotation is determined through iteration. The following criteria are used:

• The Lesik and Kenedy equation is used to determine the resistance of each weld element for the relevant load direction.

• The deformation in an element is taken to vary linearly with the distance from the instantaneous centre of rotation. At ultimate limit state, the element furthest from the centre of rotation is assumed to experience the maximum deformation.

• The ultimate resistance of each element for longitudinal shear is determined using the non-linear strength relationship explained above.

4 D. F. Lesik and D. J. L. Kennedy, "Ultimate Strength of Eccentrically Loaded Fillet Welded Connections", Structural Engineering Report 159, Department of Civil Engineering, University of Alberta


Input

The definition of bolt groups and weld groups follow the same basic pattern. However, the geometry of weld groups is entered using a slightly more complex method of polygon definition.

Defining bolt groups A bolt group analysis requires the following input:

• Analysis method.

• Number of shear planes, i.e. single or double shear.

• Number of rows and columns of bolts.

• Horizontal and vertical spacing of the bolts.

• Applied force, its orientation and offsets.

Defining weld groups A weld group definition has the following components:

• Analysis method.

• Material strengths.

• In-plane force, angle and offsets.

• Weld geometry.

The weld group input table

A weld group’s geometry is defined by entering one or more shapes in the input table. A shape may comprise straight lines and arcs or may be a circle. When more than one shape is entered, the shapes will accumulate and form one weld group.

To be able to enter a weld, you should understand the use of the input table:

• The Code column is used for categorise the data that follows in the next columns:

’+’ : The start of a new weld. An absolute reference coordinate must be entered in the X/Radius and Y/Angle columns.

Blank : Indicates a line drawn with relative coordinates.

’L’ : Indicates a line drawn using polar coordinates.


’A’ : An arc that continues from the last line or arc. The arc radius and angle are entered in the X/Radius and Y/Angle columns respectively. The angle is measured anti-clockwise from the previous line or arc end point.

’B’ : Sets the bearing, or starting angle, for the next entity, likely an arc.

’C’ : A circle with the radius entered in the X/Radius column.

Note: If the Code column is left blank, relative coordinates are used.

• The X/Radius and Y/Angle columns are used for entering coordinates, radii and angles:

X : Absolute or relative X-coordinate. Values are taken positive to the right and negative to the left.

Radius : Radius of a circle or an arc.

Y : Absolute or relative Y coordinate. Values are taken positive upward and negative downward.

Angle : Angle that an arc is extending through.

Note: If the X/Radius or Y/Angle column is left blank, a zero value is used.


Weld group definition

The definition of each portion of a weld group has three basic components:

• A reference coordinate which gives the starting point of a weld or the centre of a circle. In the Code column, enter a ’+’ to indicate the start of a new weld.

• One or more entries defining the weld's coordinates of lines and arcs or a circle’s radius.:

• Enter the absolute values of the reference coordinate in the X/Radius and Y/Angle columns.

• If the Code column is left blank, the coordinate is taken relative from the last point entered.

• Set the Code to '+' if you want to enter an absolute coordinate.

• The coordinate values are entered in the X/Radius and Y/Angle columns. A negative X or Y coordinate must be preceded by a minus sign. The plus sign before a positive X or Y coordinate is optional.

• A circular arc is defined by setting the Code to 'A' and entering the radius in the X/Radius column. The arc is then taken to extend from the end point of the last line or arc, starting at the angle that the previous line or arc ended and extending through the angle specified in the Y/Angle column. To set the bearing, or starting angle, of an arc use a 'B' in the Code column followed by the angle in the Y/Angle column.

• Define a circle by setting the centre point using the Code '+' described above. On the next line enter the Code to 'C' and the radius in the X/Radius column.

• The weld size.

Weld generation

Click the 'standard' shapes for quick generation of welds. Enter the required dimensions and orientation angle. Press Add to input to append the shape to the bottom of the table. The default values of X, Y and ß are set to the ending values of the last weld segment.


Design

Shear distribution in bolt groups and weld groups are calculated in similar ways:

Calculation of design shear forces in bolt groups A simple procedure is followed during linear analysis:

• The applied force causes an equal force in each of the bolts parallel to the force.

• The rotational shear force in each bolt is taken proportional to the distance to the centroid.

Non-linear analysis requires an iterative procedure:

• An arbitrary rotational centre is chosen.

• The strain of each bolt is proportional to its distance from the centre.

• The force on each bolt is calculated assuming the non-linear strength model explained form page 5-33.


• Equilibrium of external and internal forces is considered and the rotational centre adjusted.

• This procedure is repeated until convergence is achieved.

Calculation of design shear stresses in weld groups Assuming linear variation, rotational shear stresses in a weld group is calculated as follows:

• The centroid of the weld group is calculated.

• The rotational shear force in each segment of a weld is taken proportional to its distance from the centroid.

Non-linear analysis requires an iterative procedure:

• An arbitrary rotational centre is chosen.

• The strain in each segment of the weld is taken proportional to its distance from the centre of rotation.

• The force on each segment is calculated assuming the non-linear strength relationship explained from page 5-33.

• External and internal forces are compared and the centre of rotation adjusted to improve equilibrium.

• This procedure is repeated until convergence is achieved.


Calcsheet

The connection design output can be grouped on a calcsheet for printing or sending to Calcpad. Various settings can be made to include input data, tabular design summaries etc.


Recalling a data file The Data File is automatically included when sending a calcsheet to Calcpad. You can later recall the data file by double-clicking the relevant object in Calcpad. A data file embedded in Calcpad is saved as part of a project and therefore does not need to be saved in the connection design module as well.


Simple Connection Design 5-43

Simple Connection Design

The simple connection design modules are suitable for the design of the following connections:

• Double Angle Cleat Connection Design, Cleat: Web cleat connections.

• End Plate Connection Design, Endplate: Flexible end plate connections.

• Fin Plate Connection Design, Finplate: Fin plate connections.



The following text gives a brief background of the application of the design codes.

Design scope The simple connection design modules can analyse connections that transmit end shear and axial force only. A designed connection has negligible resistance to rotation and is thus incapable of transmitting significant moments at ultimate limit state.

The following assumptions are made:

• The centre lines of the beam and column are in the same plane.

• The connection transmits end shear only.

• Bolts have normal clearance holes.

• All bolts have threads in their shear planes.

Codes of practice The following codes are supported:

• AISC - 1993 LRFD.

• BS5950 - 1990.

• CSA S16.1 - M89.


• SABS0162 - 1984 (allowable stress design).

• SABS0162 - 1993 (limit state design).

Units of measurement Both Metric and Imperial units of measurement are supported.

Sign conventions All applied shear forces are entered as loads in the beam’s local axes:

• A positive axial force is taken as a compression force.

• A downward shear force is taken as positive.


List of symbols Where possible the same symbols are used as in the design codes. The meaning of the symbols should be clear from their use in the design output.

Analysis of bolts in shear Bolt groups in shear can be analysed using a linear or non-linear strength relationship. Refer to page 5-33 for a detailed explanation of the analysis methods.


Input

The simple connection design modules use a similar procedure for data entry:

• Settings: Select the connection type and main design parameters.

• Members: Specify the properties for the beam and column.

• Connection: Define the layout of the fasteners.

• Loads: Enter the loads applied to the connection.

Members Define the connection orientation and profile to use for each member:

• Select a connection type by clicking the Member orientation buttons.

• The column and the beam can be set to I or H-sections.

• The definition of the connecting member depends on the type of connection:

• Double angle cleat connection: Select an angle section and enter the cleat length.

• Fin plate and end plate connections: Enter a plate height, width and thickness.

• Define the relative element positions by entering the spacing between the column and beam and the vertical position of the cleat or connecting plate.

Tip: Click the Auto size and Auto spacing buttons for quick input of workable dimensions.

Design parameters Select the connection shear analysis method and define the fastener and member material properties:

• Select between linear and non-linear analysis of bolts in shear. For a detailed explanation of the analysis methods, refer to page 5-33.

• Enter a bolt type, grade and diameter. For high strength friction grip bolts, additio-nal information needs to be


supplied with regards to the analysis method.

• Enter the strength properties of the beam, column and connection members.

Connections The layout of the bolts on the connecting member is defined by entering their number and spacing.

In the case of angle cleats, the connections to the beam and column are defined indepen-dently.

Tip: Click the Auto size and Auto spacing buttons to quickly input a workable bolt layout.

View connection To verify that you have defined the connection geometry as you intended, you can view it from several angles:

• Dimensioned elevations are an easy way to check bolt spacings and the spacing between the members.

• Use the 3D view to verify the overall layout and check that bolts are far enough from webs and flanges. You can rotate a 3D view and use the View point and View plane controls as described in Chapter 2.


Loads Enter any number of load cases. For each load case:

• Use a maximum of six characters to enter a descriptive load case name or load case number, e.g. ’Dead’, ’DL + LL’ or ’1’.

• Specify the end shear forces by entering the axial force and shear force in the beam.

• When designing high strength friction grip bolts at serviceability limit state, also enter the relevant service loads.


Calcsheet

Open the Calcsheet page to design the connection. The design output is grouped on a calcsheet for printing or sending to Calcpad. Various settings can be made to include input data, tabular design summaries and the complete design calculations.

To view the individual bolt forces, open the Bolt forces page.


Recalling a data file The Data File can be included when sending a calcsheet to Calcpad. You can later recall the data file by double-clicking the relevant object in Calcpad. A data file embedded in Calcpad is saved as part of a project and therefore does not need to be saved in the connection design module as well.


Documents

Chapter Steel Connection Design - Ahmed Mansourahm531.com/Prokon and EQ course/Prokon Manual/Chap-05.pdf · Chapter Steel Connection Design The steel connection design modules can