AStrutTie Design Step (5) – Analysis Results and Structural Design Report

Analysis Results and Structural Design ReportBy clicking Design Review after the structural analysis of the truss model, the information on the cross-sectional forces of struts and ties, required and provided reinforcements, minimum reinforcements, and strength verifications of struts and nodal zones is displayed in Truss Design Review window, as shown below.
The strength conditions of concrete struts can be verified visually by executing Max. Strut/Tie Width and Req. Strut/Tie Width functions in View Options Window. In the figures shown below, the (grey-colored) maximum widths of tension and compression elements are shown in the left, and the maximum and (yellow-colored) required widths of the elements are shown in the right.
The structural design report can be previewed by double clicking Report article or clicking Preview while the right button of mouse is clicked. The items that must be previewed or printed can be selected, as shown below.
The structural design report is saved (or printed) as a RTF or an Excel file by double clicking Save as RTF file or Save as Excel file in Report Tab. The report is also saved by clicking Print while the right button of mouse is clicked. Note that the report can be saved as an Excel file only if the Microsoft Excel program is installed in the computer.

AStrutTie Design Step (4) – Modeling and Analysis of Truss Model

Modeling and Analysis of Truss ModelAfter the finite element analyses for the stress trajectories and evolutionary structural optimization, Truss Model need to be selected. The boundary elements of truss model are generated based on the outer boundary of concrete member by clicking DESIGN-Create Truss From Boundary (Dialog). In the dialog, the distance between the boundary of concrete member and the boundary elements of truss model is set.
The boundary elements of truss model can be edited depending on designers’ decision. To make the editing easier, the functions Guide Line and Grid are provided. The orthogonal guide lines are available by clicking F8 key. An example to generate the boundary elements of truss model by clicking Dynamic Guide Line is shown below.
Based on the guidelines and by using Add Elements, additional elements of truss model are generated as shown below.
The unnecessary elements of truss model are deleted by using Del Key or Delete functions after selecting the elements.
The external loads assigned in the Beginning Mode are converted to the loads acting on the generated truss model by clicking ASSIGN-Boundary Load To Truss Load. The loads on truss model can be input again by designers’ decision.
After selecting the nodes on which restraints must be imposed, the boundary conditions are setup by clicking ASSIGN-Restraints. The structural analysis on the truss model is conducted by clicking ANALYSIS-Run Analysis. After the analysis, the results including element forces are shown on the truss model.
The compressive principal stress flows or the optimization results obtained earlier can be overlapped on the truss model by activating VIEW-View Options, as shown below.

AStrutTie Design Step (3) – Structural Analysis for ESO & Stress Flow

Structural Analysis for ESO & Stress FlowThe window transforms to the Modeling Mode for numerical structural analysis after imposing loads on a concrete member. The Modeling Mode consists of ESO, Stress Flow, and Truss. The finite element model of a concrete member for ESO and Stress Flow analyses is constructed by using a mesh generator. The mesh size is setup by clicking DEFINE-Project Information.Followings are the figures that illustrate the finite element modeling of a concrete member. After clicking Beginning Mode and selecting Modeling Mode-Stress Flow, DEFINE-Project Information (Dialog) needs to be activated to alter the mesh size. The loads inserted by clicking Static Load are switched to nodal forces automatically.
If the mesh size is changed, the boundary conditions must be updated. For this, the View Options Window must be activated and Node must be On, as shown below.
After selecting the nodes on which restraints must be imposed, the boundary conditions are setup by clicking ASSIGN-Restraints.
An example is shown below.
And then, by clicking ANALYSIS-Run Analysis the finite element linear elastic analysis is conducted for checking the compressive principal stress trajectories. The left figure shown below is an example showing the stress trajectories. In the same way, by clicking ESO (instead of Stress Flow) and completing the necessary modifications and inputs in DEFINE-Project Information (Dialog) and ASSIGN-Restraints, the finite element analyses are conducted for checking the approximate load paths by the evolutionary structural optimization technique. The right figure shown below is an example showing the results of the optimization.
More results of the optimization are shown below.

AStrutTie Design Step (2) – Application of Load

Application of LoadTwo methods for applying loads are provided in the program.Node Static LoadsExternal loads are assigned by clicking ASSIGN-Static Load. After selecting nodes and elements, the following figure appears.
After clicking Static Load, the Node Static Loads (Dialog) appears by clicking the right button of mouse. And then, loads are assigned by clicking Add button.
2. Element Static LoadsAfter selecting nodes and elements, the following figure appears.
After clicking Static Load, the Element Static Loads (Dialog) appears by clicking the right button of mouse when the color of node changes from green to red. And then, loads are assigned by clicking Add button.
And then, the direction of load and load type must be selected. Three load types (point load, uniform load, and trapezoidal load) are available. An example for inputting trapezoidal load is shown below.
By repeating the inputting, multiple trapezoidal loads can be input as follows.
The material properties can be altered in Area Properties shown below.

AStrutTie Design Step (1) – Modeling of Structure

1.1 Design Steps Using Strut-Tie ModelIn the Beginning Mode, the design conditions of concrete member including the geometrical shape, load and boundary conditions, material properties, and load combinations are fixed. The design conditions are used in the Modeling Mode and design steps of strut-tie model method that require the finite element analysis of unreinforced plane concrete and truss structures.1.2 Modeling of Member GeometryThe geometrical shape of concrete member is constructed in the Beginning Mode. The geometrical shape is constructed by 1) direct drawing, 2) importing a .dxf file, 3) using a Template. For direct drawing, the functions Add Nodes and Add Elements are used. The boundary lines and truss model of the concrete member are generated by importing a .dxf file. The geometrical shape, evolutionary structural optimization, stress flow, and truss model can be generated automatically by using a Template.Importation of .dxf fileThe geometrical shape of concrete member and truss model generated as .dxf files by using drawing tools including Autocad can be imported by clicking FILE-Import. In generating a .dxf file, all drawings must be constructed as lines, and the boundary of concrete member and truss model must be named as ‘Out’ and ‘Truss’ respectively.
By importing a .dxf file, the boundary of concrete member and truss model are constructed automatically as follows.
2. Use of TemplateThe geometrical shape of concrete member and truss model are generated by clicking FILE-New From Template and selecting one of the provided templates shown below. The basic information on the geometrical shape including thickness, width, and height must be input.
3. Direct DrawingAn example for constructing the boundary of concrete member is illustrated. The boundary can be constructed by using the functions Add Nodes or Add Elements. By clicking DESIGN-Add Elements, the coordinates of end points of lines are input in Edit Coordination (Dialog) as follows.1.1 , 1.1 enter1.9 , 1.1 enter1.9 , 1.5 enter1.9 , 1.9 enter0 , 1.9 enter0 , 0 enter0.4 , 0 enter0.8 , 0 enter0.8 , 0.8 enter1.1 ,  1.1 enter
Once the boundary is constructed, the boundary must be recognized as the boundary of plane concrete member by clicking DESIGN-Create Outer Boundary.
By clicking DESIGN-Create Area, the area surrounded by the outer boundary is set to designate the information of plane concrete member including member thickness, compressive strength of concrete, and yield strength of reinforcing bars.