Quick-Start Guide

HSS Connex Online provides engineers with a simple way to check connection calculations for HSS connections.

The program interface is split into six main sections. The use and functionality of each section is described below.

Design Type and Units
Selection of Planar Connection Type
Input Parameters
Output / Saving Results

Design Type and Units

LRFD / ASD / No Safety Factor

Select the type of design: "LRFD" (Load and Resistance Factor Design) or "ASD" (Allowable Stress Design). This choice determines the material available stress and the whether the design strength (φPn) or the allowable strength (Pn/Ω) is used as specified by AISC 360. If "No Safety Factor" is selected, then the strength of the connection is simply equal to Pn (with no strength adjustment).

Note: The program assumes that the applied loads that the user supplies for each member are already factored as desired by the user, and that these loads represent the full combination of all the factored loads on the member. If different load combinations need to be checked, separate analyses must be conducted for each load combination.

Imperial / Metric

Select the desired units for input/output. This also affects the names of the HSS sections that will be listed in the section drop-downs.

Selection of Planar Connection Type

HSS Connex Online permits the design of Planar HSS connections only. Multi-planar connections are not permitted.

Plate-to-HSS / HSS-to-HSS

Select the type of connection. Plate-to-HSS follows AISC 360 Chapter K section K1 (concentrated forces on HSS). HSS-to-HSS follows sections K2 and K3 (for truss connections and moment connections, respectively).

Round / Rectangular HSS

Each planar connection must consist of entirely either round or rectangular/square HSS members. Mixing HSS types is not permitted. Square HSS members are considered to be a subset of the rectangular members.

Connection Type (Plate-to-HSS Connections Only)

Four different connection types are available for Plate-to-HSS connections: Transverse Surface, Longitudinal Surface, Longitudinal Through, and Cap Plate. For details of the different connection types, refer to AISC 360 Chapter K.

In transverse surface connections, the plate is oriented such that the plate is out-of-plane with respect to the longitudinal axis of the HSS chord member.

In longitudinal surface connections, the plate is oriented such that the plate is in the same plane as the longitudinal axis of the HSS chord member.

A longitudinal through connection is similar to a longitudinal surface connection except that the plate is continuous through the HSS chord member and is welded to both faces. As per AISC 360, longitudinal through connections are not permitted for round HSS chord members.

A cap plate connection consists of a plate welded to the end face of an HSS that is, in turn, welded to a longitudinal plate for transmission of axial force through the HSS chord.

Connection Geometry

The connection geometry options are displayed diagrammatically on the selection buttons. This selection determines how many branch members are present in an HSS-to-HSS connection and where they are located.

For Plate-to-HSS Connections: Three options are available in the order of (1) T, (2) Y and (3) X (Cross). Cap plate connections do not require the selection of any connection geometry.
(1) The T-connection is single-sided and the angle of the plate is enforced to be 90 degrees.
(2) The Y-connection is similar to the T-connections except that any plate angle between 30 and 90 degrees is permitted.
(3) The X-connection (Cross-connection) is a two sided connection. For X-connections, the plate is assumed to be identical on both sides of the connection. X-connections are not permitted for longitudinal through connections.

For HSS-to-HSS Connections: Five options are available in the order of (1) Y, (2) double Y, (3) X (Cross), (4) double X, and (5) K. In each button diagram, the label for each branch is shown (i.e. it is shown which branch is branch A, which is branch B, etc.).
(1) The Y-connection has one branch.
(2) The double Y-connection has two branches, one the mirror image of the other on the opposite side of the HSS chord member.
(3) The X (Cross) connection also has two branches, although one is on the opposite side of the connection such that they appear to be continuous.
(4) The double X-connection has four branches, one in each quadrant of the connection.
(5) The K-connection has two branches on the same side of the chord member. These branches may have a gap between them or they may overlap.
Note 1: Although no T-connection is specified, T-connections may be analyzed using a Y-connection with a branch angle of 90 degrees.
Note 2: The connection geometry does not define which AISC 360 Chapter K connection checks are performed for that connection (i.e. T,Y,X or K). Each connection is analyzed based on both the geometry and the applied loading. For example, a section with K-type geometry may be analyzed using both K and Y connection checks. For more information, consult AISC Design Guide 24.

Input Parameters

Each member in the connection (including the plates) has its own set of input parameters. This allows the specification of different material types, section geometries and loads for each member. In addition, for K geometry connections, an additional set of inputs is required to specify the gap/overlap/eccentricity of the connection. The different input forms for each member may be activated by clicking the appropriate page tab under the "Input Parameters" heading.

Whenever the input parameters for the analysis are changed, the program automatically re-analyzes the connection and provides new output results (unless there are input errors). There is no button required to initiate the analysis.

Chord / Branch Inputs

Inputs are nearly identical for the chord and the branches. Branches are labelled as A, B, C, or D. The location of each branch in the connection is shown on the connection geometry selection buttons.

Material Input: Select a material type from the drop-down box. For rectangular HSS the materials A500 Gr.B, A500 Gr.C, and the new A1085 are available. For round HSS, A53 Gr.B pipe is also available. Selection of a material type automatically populates the yield stress and tensile strength input boxes. These values may be modified after the material type is selected.
Note: The selected material type affects which HSS sections are available in the Section Input dropdown box from the HSS section database. It is possible to input a custom material type (by selecting "Custom" from the drop-down), but doing so will make it impossible to select an existing HSS section from the database (custom section geometry must be specified). To use HSS section geometry from the database with a custom material strength, select an existing material type and then change the values in the yield stress and/or tensile strength input boxes.

Section Input: Select an HSS or pipe section from the drop-down box. This selection automatically populates the section geometry input boxes and disables input for those boxes. Alternatively a custom HSS section may be used by selecting "Custom" from the Section drop-down box. Custom sections require input of the section height, width and thickness for rectangular HSS sections or the diameter and thickness for round HSS sections. The remainder of the section properties (area, section modulus and plastic modulus) are then automatically calculated. For rectangular HSS, custom section properties are calculated assuming a corner outer radius of 2t.
Note: The section database for A1085 HSS members is not yet available. Therefore, the A500 sections are used with a modified thickness of tA1085 = tA500/0.93 to account for the lower thickness tolerance in the A1085 specification. Note that not all section sizes may be practically available for A1085.

Section Orientation (Vertical/Horizontal): The vertical/horizontal selection buttons specify the strong axis direction of the chord and branches. The default orientation is vertical, which means that in-plane bending would be resisted by the strong axis of the section. If the orientation is specified as horizontal, then in-plane bending would be resisted by the weak axis of the section. The orientation of the section may also be confirmed by checking the section schematic below the input parameters section.

Geometry (Branches Only): Specify the angle between the chord and the branch longitudinal axis (in degrees).

Factored Loads: All input loads and moments must be appropriately factored prior to input. The program does not factor any loads or moments. If different load combinations need to be checked, separate analyses must be conducted for each load combination. Note also that some load types are not permitted for some connection types (see AISC 360 Chapter K). The sign conventions for the input loads, moments and shears are shown beside the title "Factored Loads" and are summarized below.
Axial loads (including chord point load): Positive numbers represent tension on the chord/branch/plate, negative numbers represent compression.
Moments: Positive numbers represent a clockwise moment on the chord/branch/plate, negative numbers represent a counter-clockwise moment.
Shear loads (plates only): Positive numbers represent a shear to the right, negative numbers represent a shear to the left.
Note: A point load may be provided on the chord to provide equilibrium for the connection. The equilibrium of the forces on the connection determines whether it is analyzed as a Y, X, or K-connection, or some combination thereof.

Plate Inputs

The plate inputs are similar to those for the chord and branches. The only differences are that different material types are available and there is no database of plate sections.

Material Input: Select a material type from the drop-down box. A36 and A572-50 materials are available. Custom material properties may be input by selecting "Custom" from the material drop-down and specifying values in the yield stress and/or tensile strength input boxes.

Section Input: Specify a width (for transverse connections) or a bearing length (for longitudinal connections) and a plate thickness.
Note: Bearing length is the width of the plate projected onto the surface of the HSS chord (= plate width / sinθ).

Geometry: Specify the angle between the chord and the plate longitudinal axis (in degrees).

Factored Loads: See Chord / Branch Inputs -> Factored Loads.

Gap/Overlap Inputs

The gap/overlap/eccentricity for a K-connection may be input in terms of either the gap, the overlap, or the eccentricity. Since the three parameters are not independant, specifying any one of the three will cause the other two to be automatically calculated. Gap is the spacing between the toes of the two branches at the surface of the chord member and is specified in length units (mm or in.). Overlap is the percentage of the overlapping member that is no longer directly in contact with the chord member (as a percentage of the projected length of the overlapping branch onto the chord). Eccentricity is the distance between the longitudinal centroidal axis of the chord and the intersection between the longitudinal centroidal axes of the two branches. Positive eccentricity is in the direction away from the branches.
Note: For overlapped connections, Branch A must always be the "overlapped" branch and branch B must always be the "overlapping" branch.

Error Messages

Any input errors will be identified in red text below the main input parameters. These include both invalid input values and applicability errors.


The schematic window shows a scale rendering of the current connection. The chord is shown in blue and the branches and plates are shown in red. The cross-section of the chord member is shown on the right side and the cross-sections of the branches are shown adjacent to the branches. The longitudinal centroidal axis of each member is shown as a dashed line. All loads and moments on the members are also shown.

The schematic is a live drawing and may therefore not be saved as an image to the local hard drive. However, an image of the schematic may be saved using the "Create HTML Report" button below the main results window.

Member sizes and geometries may be found in the main results output.


Result Summary

Immediately below the "Results" heading, a summary of the main analysis results is shown. The first line in this summary shows whether or not the connection can adequately resist the loads and moments on each branch/plate and the chord (if loads are specified). The next section of the summary provides a breakdown of the capacities of each branch and the analysis check types that were performed for that branch (Y, X, or K-connection checks). If multiple analysis check types were necessary for a given branch (based on the equilibrium of the forces in the branches and chord), this breakdown shows what percentage of the load that was analyzed as a Y, X, or K-connection. In addition, interaction values are provided for the axial load and axial/moment interaction for each branch/plate. An overall interaction value is also provided which shows the worst interaction value out of those for each branch (representing the overall interaction for the connection).

Main Results Window

The analysis results are updated every time an input parameter changes. These results are summarized in the main results window in plain text format. Each section of the output is described briefly below.

Title and Disclaimer: This section includes the title and version of the software that was used for the analysis, the date and time of the analysis, the design code that was used and a disclaimer.

Load and Resistance Summary: This section provides the same information as the result summary discussed above and additionally includes equilibrium data. Warnings are provided here if the X-direction forces, Y-direction forces, or moments appear to be unbalanced. If the Y-direction forces are unbalanced, the program assumes that the unbalanced load is taken by shear in the chord member.

Input Summary: This section includes all material and section properties, geometry and the applied loads on each member. It also includes checks on the limits of applicability for each branch as defined in AISC 360 Chapter K and calculated general functions for the calculations in each applicable table from Chapter K.

Output Summary: For each branch and each applicable connection check type (Y, X or K), this section provides the results from every applicable limit state check. Then, for each, it identifies the governing axial force capacity based on the worst-case limit state.

Output / Saving Options

HSS Connex does not support direct saving of the output file due to HTML limitations; however, the program provides two easy ways to save the output: HTML Report and Copy/Paste.

HTML Report

Below the Main Results Window, there is a button that is labelled "Create HTML Report". This creates a formatted report in a new HTML window with a copy of the connection schematic at the top and a listing of the complete results text below. This report may be saved by printing the page as a pdf or it may be printed directly onto paper for a hardcopy record.

The connection schematic may be saved as an image file separately by right-clicking the image and selecting "Save image as..." or equivalent.


The complete results text may easily be copied using the "Select All Data" button which is located below the main results window. This button selects the entire contents of the main results window. To copy the text, type Ctrl+C on Windows or Command+C on Macintosh. This operation copies the text to the operating system's clipboard. The text may now be pasted into a text editor or word processor using Ctrl+V on Windows or Command+V on Macintosh.