Code Checks of Prestressed Structures in SCIA ESA PT

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1 Code Checks of Prestressed Structures in SCIA ESA PT

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3 Table Of Contents Prestressed concrete... 5 Checks of prestressed concrete... 5 Crack control... 5 Performing crack control... 6 Checking of limit strain... 6 Detailed checking of limit strain... 7 Performing the checking of limit strain Checking to interaction diagram Detailed checking to interaction diagram Performing the checking to interaction diagram Allowable stress in concrete Detailed check of allowable stress in concrete Performing the check of allowable stress in concrete Check of prestressing reinforcement Performing the check of prestressing reinforcement Allowable principal stresses Performing the check of allowable principal stresses Detailed check of allowable principal stresses iii

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5 Prestressed concrete Checks of prestressed concrete This Scia Engineer module is intended for experienced users with good technical knowledge of the calculation of prestressed concrete structures including their time-dependant effects. The user may want to perform checks of strength, deflections and stability according the EN code for a prestressed concrete structure, because the design has to fulfil the regulations set by the European Union. Both initial and resultant state of the stresses, strains, etc. can be reviewed. The initial state is the state of the crosssection wherein all permanent loads including prestressing are applied. The resultant state is the state of the crosssection wherein all loads (permanent and variable including prestressing) are applied. The operating stress in the prestressed tendons/strands is the stress including the losses due to creep, shrinkage and relaxation. Moreover, the losses due to elastic deformation are also taken into account. The moment capacity of a whole beam can be calculated for the resultant vector moment of My and Mz. Also the capacity of a single section can be checked using the interaction diagrams of N, My and Mz. The allowable stresses are checked according to article The influence of the environmental classes, amount of soft steel reinforcement and the location of the prestressing reinforcement can be verified for individual construction stage. Limitations The checks of prestressed structures can be performed in a frame XZ, frame XYZ, grid XY, plate XY and general XYZ. The checks of prestressed structures can be used for composite (concrete/concrete) cross-sections only. The checks of prestressed structures can be used for beam members only. It is not possible to check lightweight concrete members. It is not possible to check plain and lightly reinforced concrete members. The anchorage length is not automatically calculated. It is not possible to check deep beams. It is not possible to use checks of prestressed structures after a physically non-linear (deflections/internal forces) calculation. It is not possible to check the fire resistance of the structure. Prerequisites IMPORTANT: The project with prestressed concrete 1D elements must be calculated with respect to construction stages (preferably TDA). Crack control Handling with the function is analogous to Checking of limit strain. The values offered for display are naturally different. Limitations The calculation of crack width is performed ONLY for the axial force and bending moment My. In addition, the moment My must be in the plane of symmetry of the cross-section. If either of the two conditions is not met, the program issues a corresponding warning. Two moment load The calculation of crack width assumes that the load which the cross-section is subjected to is acting in the XZ-plane (in the local coordinate system) of the beam. The load is assumed to be composed of one bending moment about the local Y-axis of the beam. The analysed section, however, is subjected to two bending moments. Non-symmetrical result plane The calculation of crack width assumes that the load which the cross-section is subjected to is acting in the XZ-plane (in the local coordinate system) of the beam. The resultant strain-plane is inclined from the XZ-plane of the bending moment, probably due to asymmetry in reinforcement, due to an opening, etc. Values w As max. distance Crack width Required reinforcement area with respect to crack formation Max. distance of reinforcement bars 5

6 Concrete Code Check max. diameter Sigma p 0 Max. diameter of reinforcement bars Decompression stress Note: This calculation can be used only for SLS combinations. For the procedure read Performing crack control. Performing crack control The procedure to perform the crack control 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Crack control (single click on the function is sufficient to invoke the function). 3. Select the required type of load. 4. Select the required load case, combination or class. 5. Select beams to be checked. 6. Select the required quantity and if required, make other adjustments in the property window. 7. Click Action button [Refresh] to see the selected design values. 8. Repeat steps 3 to 7 as many times as required. Note: This calculation can be used only for SLS combinations. Note: This function does not offer Single check action button. Checking of limit strain Parameters Name Selection Type of load Load case/combination/class Filter Print explanation Shows the name of the function. All The result diagrams are displayed on all the active members in the structure. Standard The result diagrams are displayed on all the currently selected members. Selected This option allows the user to display diagrams on selected members. It is similar to the previous option but offers something more. See below the table. Named selection This option allows the user to select one of the previously created, named and saved selections. This item selects the type of load for which the results are to be displayed: load cases, combinations, result classes. If any of the option is marked with an asterisk, the results for that option are not available. Depending on the option selected in the previous item, this combo box offers the available load cases/combinations/classes. This option enables the user to filter the members on which the results will be displayed. If ON, the output in the Preview window (invoked by 6

7 Theoretical background Values Extreme Drawing setup action button [Preview]) shows the explanation of possible errors and warnings encountered during the calculation. This combo offers the available result quantities. This item control the display of numerical values attached to the result diagram. Read chapter Results > Adjusting the style of result diagrams in the Reference Guide. Section Read chapter Results > Selected sections > Displaying the results in selected sections in the Reference Guide. Selection: Selected With this option, you may select required members on which the results are to be displayed and review the results. Then you may clear the selection. The result diagrams, however, remain displayed. Now you may make a new selection and invoke the refresh of the screen. The program will ask you what to do. The available options are: Use current selection The result diagrams displayed during the last refresh are deleted. New result diagrams are displayed on the currently selected members only. Add current selection to previous selection The result diagrams displayed during the last refresh remain displayed. New result diagrams are shown on the currently selected members. Use previous selection The current selection is ignored. The result diagrams displayed during the previous refresh remain displayed. Subtract current selection from previous selection If there is a result diagram currently displayed on one of the currently selected members, this diagram is hidden. The result diagrams that are shown on members that are not in the current selection remain displayed. Values check value eps cc eps sc eps st eps tt Vzu T u Vrdi the assessment by means of relative value concrete strain reinforcement steel strain compression reinforcement steel strain tension tendon strain tension shear resistance torsional resistance design shear resistance at the interface Action buttons Refresh Calculation info Concrete setup Single check Preview Refreshes the screen. Show a brief information about the calculation of the result quantities. Open the Setup dialogue. Calls the Detailed checking of limit strain. Shows result table(s) in the Preview window. For the procedure read Performing the checking of limit strain. Detailed checking of limit strain Parts of the dialogue Step / position The user may select the section of the beam that should be calculated. 7

8 Concrete Code Check Calculation Side view of the beam Set of graphical windows Information window Numerical output This group shows internal forces in the selected section, enables the user to change the settings and calculate the results. The designed beam is shown. Mouse cursor may be used to select the required section for assessment. Pop-up menu may be used to control the view adjustment. The set of graphical windows presents all the important information related to the design. Pop-up menu may be used to control the view adjustment. Any comments accompanying the calculation are listed in this window. Change of setup This button opens a dialogue where you can specify what the content of the output document is to be. Output This button produces the output either to the Document or to the Preview window. Step / position Step Position Move cursor left Move cursor right Move to previous segment Move to next segment automatic recalculation-redraw Section This value defines the step by which the section is moved if Move cursor left or Move cursor right is clicked. This value specifies the x-coordinate of the section that is assessed. Selects a section that is located one step from to the left from the current section. Analogous to the previous item. This button is meaningful only for "members" consisting of several parts, e.g. continuous beam where each span is modelled by a separate beam. It moves the cursor to the previous segment (part). Analogous to the previous one. If ON, all the calculations and display regenerations are done automatically once the user changes any value in the dialogue. If OFF, the use must invoke the calculation manually through button [Calculation]. Selected section The assessment is carried out for the selected section of the beam. Extreme section The program automatically finds the extreme section for the selected quantity and performs the check of this critical section. Calculation Code setup Extreme Internal forces Calculation Filtered dialogue for adjustment of design parameters is opened on the screen. Selects the quantity for which the check is performed. Or if Extreme section is adjusted in the previous group, this selects the quantity for which the extreme is found. Lists internal forces in the selected section. Performs the calculation. 8

9 Theoretical background Set of graphical windows Name of the window Cross-section Loads Strain *) Stress *) Strain 3D *) Contents The shape, dimensions and description of the assessed cross-section. The external loads acting in the selected section. Distribution of the strain over the cross-section. It is graphically shown which part of the cross-section is subjected to tension and which to compression. Analogous to strain. Stress 3D *) Analogous to Strain 3D. Force 3D *) Stress-strain diagram 3D drawing of the strain distribution over the section. The forces acting in the individual reinforcement bars and in the concrete. Stress-strain diagram. The user may click the required point on the crosssection image and the corresponding stress-strain diagram is shown. *) Initial and resultant state For the quantities marked with an asterisk, the user may select whether the (i) initial state, or (ii) resultant state, or (iii) both should be displayed. This selection can be made in the Picture properties dialogue that can be opened through the pop-up menu of the graphical window. Values Initial Resultant Initial and resultant The initial state is the state of the cross-section wherein all permanent loads including prestressing are applied. The resultant state is the state of the cross wherein all loads (permanent and variable including prestressing) are applied. Both the previous option are shown together in one picture. 9

10 Concrete Code Check Material All Concrete Reinforcement steel Strands Steel The diagram is displayed for all the material in the cross-section. The diagram is displayed only for the concrete part of the cross-section. The diagram is displayed only for the reinforcement steel. The diagram is displayed only for strands. The diagram is displayed only for (soft) steel. Procedure to select the state to be displayed 1. Select the graphical window (tab) you want to review. 2. Place the mouse cursor inside of the graphical window. 3. Click the right-mouse button, the pop-up menu is opened on the screen. 4. Select function Picture properties and click it. 5. Make required settings in the dialogue. 6. EITHER: Confirm with [Apply] to see the changes and NOT to close the dialogue. OR: Confirm with [OK] to see the changes and close the dialogue. The following table demonstrates the individual windows through a sample picture they may contain. Cross-section Loads 10

11 Theoretical background Strain Stress 11

12 Concrete Code Check Strain 3D Stress 3D 12

13 Theoretical background Force 3D Stress-strain diagram Performing the checking of limit strain The procedure to perform the check 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Check response (single click on the function is sufficient to invoke the function). 13

14 Concrete Code Check 3. Select the required type of load. 4. Select the required load case, combination or class. 5. Select beams to be checked. 6. Select the required quantity and if required, make other adjustments in the property window. 7. Click Action button [Refresh] to see the selected design values. 8. Repeat steps 3 to 7 as many times as required. The procedure to perform the detailed check 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Check response (single click on the function is sufficient to invoke the function). 3. Click Action button [Single check] to invoke the dialogue for the detailed check. 4. Select the member to be checked. 5. The Single check dialogue is opened on the screen. Checking to interaction diagram Handling with the function is analogous to Checking of limit strain. Values Check value Nu Myu Mzu Vzu T u Vrdi The result of the check. The value of 1 means that the capacity is fully utilised. The limit axial force the cross-section can transfer. The limit bending moment My the cross-section can transfer. The limit bending moment Mz the cross-section can transfer. The limit shear force. The torsional resistance. Design shear resistance at the interface. For the procedure read Performing the checking to interaction diagram. Detailed checking to interaction diagram This is analogous to Detailed checking of limit strain. The graphical windows are different. Set of graphical windows Cross-section Loads Vertical section Horizontal section Interaction diagram Shows the cross-section, its dimensions and defined reinforcement. Shows internal forces in the selected section. Shows the vertical section of the 3D interaction diagram. Shows the horizontal section of the 3D interaction diagram. Shows the 3D interaction diagram. 14

15 Theoretical background Performing the checking to interaction diagram The procedure to perform the check 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Check capacity (single click on the function is sufficient to invoke the function). 3. Select the required type of load. 4. Select the required load case, combination or class. 5. Select beams to be checked. 6. Select the required quantity and if required, make other adjustments in the property window. 7. Click Action button [Refresh] to see the selected design values. 8. Repeat steps 3 to 7 as many times as required. The procedure to perform the detailed check 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Check capacity (single click on the function is sufficient to invoke the function). 3. Click Action button [Single check] to invoke the dialogue for the detailed check. 4. Select the member to be checked. 5. The Single check dialogue is opened on the screen. Allowable stress in concrete Handling with the function is analogous to Checking of limit strain. The values offered for display are naturally different. Values Check value sigma cc,max sigma cc,ch sigma cc,qp f ct,eff sigma c,aa sigma cq,min sigma clt,min sigma cq,max sigma clt,max sigma c,inc The result of the check. The value of 1 means that the capacity is fully utilised. Allowable stress of concrete prior and after anchoring/transfer of prestressing. Allowable stress of concrete in compression under SLS characteristic combination. Allowable stress of concrete in compression under SLS quasipermanent combination. Allowable stress of concrete in tension under SLS combinations. Stress of concrete after anchoring/transfer of prestressing. Minimum concrete stress after application of self-weight, all permanent, and variable loads. Minimum concrete stress caused by long-term loads. Maximum concrete stress after application of self-weight, all permanent, and variable loads. Maximum concrete stress caused by long-term loads. Stress increment in concrete caused by selected load case. For the procedure read Performing the check of allowable stress in concrete. 15

16 Concrete Code Check Detailed check of allowable stress in concrete This is analogous to Detailed checking of limit strain. Performing the check of allowable stress in concrete The procedure to perform the check 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Allowable stress in concrete (single click on the function is sufficient to invoke the function). 3. Select the required type of load. 4. Select the required load case, combination or class. 5. Select beams to be checked. 6. Select the required quantity and if required, make other adjustments in the property window. 7. Click Action button [Refresh] to see the selected design values. 8. Repeat steps 3 to 7 as many times as required. The procedure to perform the detailed check 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Allowable stress in concrete (single click on the function is sufficient to invoke the function). 3. Click Action button [Single check] to invoke the dialogue for the detailed check. 4. Select the member to be checked. 5. The Single check dialogue is opened on the screen. Check of prestressing reinforcement Handling with the function is analogous to Checking of limit strain. The values offered for display are naturally different. Values Check value sigma p,pa sigma p,aa sigma p,ltl sigma pq,min sigma pq,max sigma pq,max sigma pq,min sigma p,inc sigma p,un sigma p,max The result of the check. The value of 1 means that the capacity is fully utilised. Stress of prestressing reinforcement prior anchoring (during tensioning). Stress of prestressing reinforcement after anchoring/transfer of prestressing. Stress of prestressing reinforcement after long-term losses (LTL). Minimum stress of prestressing reinforcement after application of self-weight, all permanent, and variable loads. Maximum stress of prestressing reinforcement after application of self-weight, all permanent, and variable loads. Stress range in prestressing reinforcement. Stress increment in prestressing reinforcement caused by selected load case. Maximum unbalanced stress the difference of stresses calculated from the strain determined in structural analysis once as elastic stress (Hooke s law), and second as stress nonlinear stress-strain relationship. Allowable stress of prestressing reinforcement prior anchoring (during tensioning). sigma pm0 Allowable stress of prestressing reinforcement after anchoring/transfer of prestressing. sigma pm Allowable stress of prestressing reinforcement caused by SLS combinations. For the procedure read Performing the check of prestressing reinforcement. 16

17 Theoretical background Performing the check of prestressing reinforcement The procedure to perform the check 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Check of prestressing reinforcement (single click on the function is sufficient to invoke the function). 3. Select the required type of load. 4. Select the required load case, combination or class. 5. Select beams to be checked. 6. Select the required quantity and if required, make other adjustments in the property window. 7. Click Action button [Refresh] to see the selected design values. 8. Repeat steps 3 to 7 as many times as required. Allowable principal stresses Handling with the function is analogous to Checking of limit strain. The values offered for display are naturally different. Values Sigma 1 Sigma 2 max Sigma 3 max Sigma x max Sigma y max Sigma z max Tau xy max Tau xz max self-explanatory (see also Detailed check of allowable principal stresses) self-explanatory (see also Detailed check of allowable principal stresses) self-explanatory (see also Detailed check of allowable principal stresses) self-explanatory (see also Detailed check of allowable principal stresses) self-explanatory (see also Detailed check of allowable principal stresses) self-explanatory (see also Detailed check of allowable principal stresses) self-explanatory (see also Detailed check of allowable principal stresses) self-explanatory (see also Detailed check of allowable principal stresses) For the procedure read Performing the check of allowable principal stresses. Performing the check of allowable principal stresses The procedure to perform the check 1. Open service Concrete. 2. Select function 1D member > Member check > Check of prestressed concrete > Allowable principal stress (single click on the function is sufficient to invoke the function). 3. Select the required type of load. 4. Select the required load case, combination or class. 5. Select beams to be checked. 6. Select the required quantity and if required, make other adjustments in the property window. 7. Click Action button [Refresh] to see the selected design values. 8. Repeat steps 3 to 7 as many times as required. 17

18 Concrete Code Check The procedure to perform the detailed check 9. Open service Concrete. 10. Select function 1D member > Member check > Check of prestressed concrete > Allowable stress in concrete (single click on the function is sufficient to invoke the function). 11. Click Action button [Single check] to invoke the dialogue for the detailed check. 12. Select the member to be checked. 13. The Single check dialogue is opened on the screen. Detailed check of allowable principal stresses Parts of the dialogue Step / position Calculation Side view of the beam Set of graphical windows Information window Numerical output The user may select the section of the beam that should be calculated. This group shows internal forces in the selected section, enables the user to change the settings and calculate the results. The designed beam is shown. Mouse cursor may be used to select the required section for assessment. Pop-up menu may be used to control the view adjustment. The set of graphical windows presents all the important information related to the design. Pop-up menu may be used to control the view adjustment. Any comments accompanying the calculation are listed in this window. Change of setup This button opens a dialogue where you can specify what the content of the output document is to be. Output This button produces the output either to the Document or to the Preview window. Step / position Step Position Move cursor left Move cursor right Move to previous segment Move to next segment automatic recalculation-redraw Section This value defines the step by which the section is moved if Move cursor left or Move cursor right is clicked. This value specifies the x-coordinate of the section that is assessed. Selects a section that is located one step from to the left from the current section. Analogous to the previous item. This button is meaningful only for "members" consisting of several parts, e.g. continuous beam where each span is modelled by a separate beam. It moves the cursor to the previous segment (part). Analogous to the previous one. If ON, all the calculations and display regenerations are done automatically once the user changes any value in the dialogue. If OFF, the use must invoke the calculation manually through button [Calculation]. Selected section The assessment is carried out for the selected section of the beam. 18

19 Theoretical background Extreme section The program automatically finds the extreme section for the selected quantity and performs the check of this critical section. Calculation Code setup Extreme Internal forces Calculation Filtered dialogue for adjustment of design parameters is opened on the screen. Selects the quantity for which the check is performed. Or if Extreme section is adjusted in the previous group, this selects the quantity for which the extreme is found. Lists internal forces in the selected section. Performs the calculation. Set of graphical windows Name of the window Cross-section Loads Sigma x Sigma y Sigma z Contents The shape, dimensions and description of the assessed cross-section. The external loads acting in the selected section. Axial stress in longitudinal direction. Axial stress in the y-direction. Axial stress in the z-direction. Tau xys Shear stress in the x-direction perpendicular to the y- direction due to the shear force in that direction. Tau xzs Shear stress in the x-direction perpendicular to the z- direction due to the shear force in that direction. Tau xyt Shear stress in the y-direction perpendicular to the x- direction due to the torsion. Tau xzt Shear stress in the z-direction perpendicular to the x- direction due to the torsion. Tau xy Shear stress in the y-direction perpendicular to the x- direction (Tau xys + Tau xyt). Tau xz Shear stress in the z-direction perpendicular to the x- direction (Tau xzs + Tau xzt). Sigma 1 Principal stress in direction 1 Sigma 2 Principal stress in direction 2 Sigma 3 Principal stress in direction 3 Procedure to adjust display properties Select the graphical window (tab) you want to review. Place the mouse cursor inside of the graphical window. Click the right-mouse button, the pop-up menu is opened on the screen. Select function Picture properties and click it. Make required settings in the dialogue. EITHER: Confirm with [Apply] to see the changes and NOT to close the dialogue. OR: Confirm with [OK] to see the changes and close the dialogue. 19