Bridging Your Innovations to Realities

Transcription

1 Tutorial 2 Prestressed Concrete Bridge Bridging Your Innovations to Realities 1

2 Contents 2 1. Project Information 2. Definition of materials 3. Definition of Sections 4. Definition of Time dependent Materials 5. Creating the geometry 6. Boundary Conditions 7. Loads 8. Moving Load 9. Construction Stage Analysis 10. Results

3 1. Project Information 3 Perspective view 63m 16m

4 2. Definition of materials 4 In midas Civil materials can be added at any point in time as well as through different commands. However the most commonly used is : Properties -> Material Properties -> Material (tab)

5 2. Definition of materials Here, by pressing ADD a new dialog box pops up. Fill this in as shown below: 5

6 2. Definition of materials 6 After pressing apply this material will appear in the list for materials and you can add in the next one for the steel tendons as shown below: Material ID Name Type 1 C50/60 Concrete 2 Y_1670S7(15.2mm) Steel

7 3. Definition of Sections 7 Now that the materials are defined, the sections will be defined in the next step. This can be done in the Section tab by pressing Add and selecting the PSC tab. Here fill in the dialog box as shown below:

8 3. Definition of Sections 8 Similarly for the shallow section:

9 3. Definition of Sections 9 For the pier section go to the DB/User tab, fill in the data as shown below and press OK: Works Tree 3

10 4. Definition of Time dependent Materials 10 Time dependent material effects can be defined from the Time Dependent Material tab: 1) First defining creep and shrinkage: 50,000 By clicking on show results, you can check the creep coefficient and shrinkage strain graphs as shown below:

11 4. Definition of Time dependent Materials 11

12 4. Definition of Time dependent Materials 12 The variation of compressive strength will be defined as shown below :

13 4. Definition of Time dependent Materials 13 Now, in order to connect these properties to our material, a Material link will be generated as shown below:

14 4. Definition of Time dependent Materials 14 Goto Analysis > Construction Stage to check on Initial Tangent Displacement for Erected Structures

15 5. Creating the geometry 15 First create a node, this you can do from: Node/Element ->Create Nodes Fill in the pop up dialog box as shown below: In order to create the deck, this node will be extruded into line elements. Using the select single tool, select the node by drawing a box around it.

16 5. Creating the geometry 16 Next in order to obtain the line elements, the extrude feature shall be used from Node/Element -> Extrude: To obtain an appropriate mesh for the 63m deck this will be broken down into 3m long elements. In order to obtain this, fill in the dialog box as shown below: By pressing apply the following can be seen Zoom fit can be done by pressing icon :

17 5. Creating the geometry 17 Now, to create the pier at mid point, select the middle element and divide this in two. You can select the middle element by ID from the Element Selection box. This can be done from : Node/Element -> Divide Then simply fill in the dialog box as shown below (it has these options by default so you only need to press apply) The Span has 21 elements and you can choose element number 11 to divide.

18 5. Creating the geometry 18 As a result this will change to: This node will be copied down by 6.5m (which is the depth of the diaphragm). First select the node using the select single option then go to: Node/Element -> Translate (within the node tab NOT elements)

19 5. Creating the geometry 19 And fill in the dialog box as shown below: Once the node is created in order to obtain the pier, this will be extruded by 16m using element lengths of 2 m.

20 5. Creating the geometry 20 Select the node, go to: Node/Element -> Extrude Elements and fill in the dialog box as shown below: Change section type to 3: Pier

21 5. Creating the geometry - Tapering of sections 21 In order to taper this bridge 2 tapered sections will be created. This can be done from Properties -> Section Properties -> Add -> Tapered Tab For the left side of the taper import the 'span' section for 'Size-i'

22 5. Creating the geometry - Tapering of sections 22 Scroll down and import 'diaphragm' for 'Size-j' then finally change the offset to Centre-Top by clicking on Change Offset... as shown below Similarly create taper right, however in this case 'Size-i' will be the Diaphragm section and 'Size-j' the Span section.

23 5. Creating the geometry - Tapering of sections 23 Once you have these two sections, turn on the element number and select elements 1 to 10 by putting this into the select elements window as shown below: For these selected elements just simply drag and drop Left taper from the works tree. This will taper your elements one by one.

24 5. Creating the geometry - Tapering of sections However to create a continuous tapering, select the elements 1 to 10, for which a tapered group will be created. Go to Properties -> Tapered Group 24 In the pop up dialog box just simply add in a name and press add as shown below: Once this is done the tapering will be finished

25 5. Creating the geometry - Tapering of sections 25 Now repeat the same procedure on the right hand side for elements 12 to 21 and naming the group Right taper. Once tapering is done on both sides this is what the bridge will look like: As we do not need the element numbers anymore, this can be deactivated

26 5. Creating the geometry - Groups 26 There are various groups in midas Civil these include: Structural, Boundary, Load and Tendon Groups To ease our work or for the purpose of construction stage analysis we need to create groups These groups can be found under the groups tab in the Tree menu. Right click on Structure Group and click on New...

27 5. Creating the geometry - Groups Add in Deck with specifying 1 to 4 suffixes: Similarly the Boundary and Load groups can be created so to obtain the following groups: 27 Then add in Pier as the last group without specifying any suffixes:

28 5. Creating the geometry - Groups Assigning elements to structure groups 28 Select elements 7to15 22, in other words the diaphragm and 4 segments on each side: For these elements simply drag and drop Deck 1, you will see these elements being assigned to this group :

29 5. Creating the geometry - Groups 29 Similarly the next two segments on each side will be added to Deck2 : The same procedure is repeated for the other four segments, they are added in 2 by 2 into Deck3 and Deck4.

30 5. Creating the geometry - Groups Finally the pier elements are added to the Pier structural group (to select these elements you can simply double click on the Pier section from the works tree and all the elements which have the Pier section assigned to them, will be selected) 30 Once the pier is added to the structure group, you have completed Structure Group: At this point you should have a model equivalent to: 1 - Groups Created

31 6. Boundary conditions 31 To provide stability for our structure and to represent the actual conditions in which this is, we need to provide boundary conditions. Supports For the definition of Side Support select the two end nodes of the deck. To make this selection easier, turn off the hidden view:

32 6. Boundary conditions 32 Select the two end nodes and go to: Boundary -> Define Supports and fill in the dialog box as shown Press apply and the following can be seen:

33 6. Boundary conditions 33 Similarly the Pier Support is defined. For this select the node at the bottom of the pier and fill in the boundary dialog box as shown below: Press apply and the following can be seen:

34 Links 6. Boundary conditions 34 To provide connectivity between the deck and the pier in the rigid zone a link needs to be created between the node at the top of the pier and mid point. For this go to Boundary -> Elastic Link, change the link type to Rigid Scroll down and click on '2 Nodes'. Now select the two nodes (top of pier and mid point of deck)

35 7. Loading 35 In midas Civil, loading works the following way: 1) Load cases are defined 2) Loads are assigned to these load cases Definition of load cases Go to Load -> Static Load Cases, here you can define all your load cases by defining their name, type and then pressing add:

36 7. Loading 36 In the same manner the following load cases are added in: Make sure all load types are Construction Stage Load At this point you should have a model equivalent to: 2 Boundaries and Load Cases

37 7. Loading 37 Self Weight Go to Load -> Self Weight and fill in the pop up dialog box: By pressing add, the self weight will appear in the window as shown below:

38 7. Loading 38 Surfacing For defining the surfacing load select the main deck and apply a Beam Element Load. For this go to: Load -> Element Beam Load as shown below: 1. Select all the elements for Deck 2. Load case/group name : Surfacing 3. Enter a value of -5 in the Global Z direction 4. Press apply

39 7. Loading 39 To clear the screen press initial view on the right side of the screen Form traveller and wet concrete load These two can be defined the same way by using nodal loads. Starting with the wet concrete loading, go to Load -> Nodal Loads

40 7. Loading 40 First select the node and then in the dialog box select the load case, load group name and fill in as shown below: By pressing 'apply' the Force and the Moment will be applied to the node. Using this procedure all wet concrete and form traveller loads can be applied. However these loads can be input into excel and applied to the model from there.

41 7. Loading 41 Here you can see the above loading after the dialog box was closed: The values for this can be displayed by right clicking on the load and press display: This can also be checked in a tabular format as well

42 7. Loading 42 Using this table, the loads, moments and groups can be defined for each node as shown in the Excel table below: First, delete the loading you have defined for node 7, and then by copying this table from Excel into the Nodal loads table the following can be seen:

43 7. Loading Looking in the works tree, the Form traveller loads and Wet concrete loads are all defined: 43 At this point you should have a model equivalent to: 3 - Loads - No Prestress Loads Added

44 7. Loading 44 Tendons and prestress When it comes to tendons, first the tendon property must be defined which can be done from: Here press Add in the pop up dialog box In the next dialog box, click on the 3 dots to define the tendon area and a small dialog box appears where you can specify the strand diameter and the number of strands:

45 7. Loading 45 Fill in the rest of the dialog box as shown below:

46 7. Loading 46 Creation of tendons To create the tendons go to: Load -> Temp/Prestress -> Tendon Profile The following dialog box appears, fill this in as shown. Also select the elements to which you want to assign the tendons or put this in the Assigned Elements field : By pressing OK, the tendon will be generated:

47 7. Loading 47 We will be creating 3 more tendons. Please create the tendons using the dialog box as shown: Make sure element 12to22 are assigned for tendon 3 and 4. Also, Make sure the Profile insertion point is changed to 22. Similarly tendon 4 will start from element 22 as well.

48 7. Loading 48

49 7. Loading 49 Once all four tendons are added in: Now all four will be copied down by 0.5m. For this, the copy option will be used within the tendon profile dialog box, first select all the tendon you want to copy (in this case all four of them) and then press Copy/Move. Here fill in the dialog box as shown right:

50 7. Loading 50 Once you press OK, all four tendons are copied down by 0.5m, the dialog box and the tendons appear as shown below:

51 7. Loading 51 Apply prestress: Go to Load -> Temp./Prestress -> Tendon prestress Change the units from the bottom right part of the screen. In this case it's beneficial changing into N and mm rather than using kn and m.

52 7. Loading Once the units are changed in the dialog box change the Load case and the load group names fill in the dialog box as shown below: The prestress added in will appear in the model and also will be added into the window above the Add button 52 At this point you should have a model equivalent to: 4 Loads Including Prestress Loads

53 8. Moving Load 53 Adding in Moving Loads in midas Civil is a 3 step procedure: 1) Define lanes 2) Add vehicles 3) Connect the lanes to the vehicles through moving load cases First specify the code to be used from Load -> Moving Loads-> Moving Load Code

54 8. Moving Load 54 Definition of lanes Go to: Load -> Moving Load -> Traffic Line Lanes -> Add Change the units back to m at the bottom right part of the screen. In midas Civil the definition of lanes happens with an eccentricity from a reference line

55 8. Moving Load 55 Following this, fill in the dialog box as shown: For the Selection by keep the option as 2 points, then click on the two ends of your bridge, this way the software will define the reference line from which your lane will be positioned at a distance defined in the eccentricity field.

56 8. Moving Load 56 Press Apply and you will see your lane being defined: When defining the next lane delete the information the software used to create the previous lane. For this simply click on No, and hit Delete

57 8. Moving Load 57 Similarly create lanes 2,3 and 4. The eccentricities for these are -1.5, 1.5 and 4.5m respectively. Once this is done, the lanes look as shown below:

58 8. Moving Load 58 Vehicle definition To define these go to Load -> Moving Load -> Vehicle -> Add Standard Here the adjustment factors can be changed for LM1.

59 8. Moving Load 59 By pressing apply the vehicle type can be changed, and LM3 can be defined: Looking at the works tree the following should be defined: Press ok and the second vehicle will be defined.

60 8. Moving Load 60 Moving Load cases Go to Load -> Moving Load -> Moving Load Case Here fill in the dialog box as shown below:

61 8. Moving Load 61 Add in another moving load case as shown below: By pressing OK The works tree will change as shown below: At this point you should have a model equivalent to: 5 Moving Loads

62 9. Construction Stage Analysis 62 As mentioned previously the groups will be used for the definition of the Construction Stages (CS) To start defining these go to: Load -> Construction stage -> Define C.S. -> Add In the dialog box that appears the duration will be defined as well as different Element, Boundary and Load groups will be activated. Fill in the dialog box as shown below. 28 days 100%

63 9. Construction Stage Analysis 63 With this the first construction stage is done. The following construction stages are described below in the table: Stage Duration Element Boundary Load CS2 10 Deck2 Activate:Wet Concrete2, Form Traveler2 Age 7 Deactivate: Wet Concrete1,Form Traveler1 CS3 10 Deck3 Activate:Wet Concrete3, Form Traveler3 Age 7 Deactivate: Wet Concrete2,Form Traveler2 CS4 10 Deck4 Activate:Wet Concrete4, Form Traveler4 Side Supports Age 7 Deactivate: Wet Concrete3,Form Traveler3 CS Activate: Surfacing Deactivate: Wet concrete4, Form Traveler4

64 9. Construction Stage Analysis 64 The construction stages can be check through the CS dropdown box in the modelling space: Once this is done, perform the analysis. When done the software will indicate the analysis was completed successfully in the message window: At this point you should have a model equivalent to: 6 Final Model

65 10. Results 65 All results can be checked in each construction stage for various load cases. Starting with the reactions, go to Results -> Reactions -> Reaction Forces/Moments Change to the CS which you would like to check and select the load case you want to check the results for. For these the values and the legend can be displayed : By pressing Apply the results can be checked

66 10. Results 66 Similarly Displacements can be checked from: Results -> Deformations -> Displacement Contour Bending Moments can be checked from: Results -> Forces -> Beam Diagrams Correction to be made

67 10. Results 67 Stress results can be checked from Results -> Stresses -> Beam Stresses (PSC)

68 10. Results 68 Tendon Stress Losses (Results -> Results Tables -> Tendon -> Tendon Loss) Here tendon stress losses can be checked in a tabular format: Correction to be made

69 10. Results 69 This can also be checked in a graphical format from the Tendon Loss Graph: Correction to be made

70 10. Results 70 Using the moving load tracer the software will generate the worst live load distribution for a particular position in the structure and a given effect. This can be checked only in the Post Construction stage. These moving load results can be checked using the Moving Load Tracer from : Results -> Moving Load -> Moving Load Tracer -> Beam Forces Moments

71 10. Results By clicking on Key Element the window turns green and you can simply click on the element of interest. By pressing Apply the influence lines and load distribution can be obtained 71