Guidelines for creating 3d modelling of UG station using STAAD Pro software

Guidelines for Creating 3D Model of Under Ground Metro Station

Using STAAD Pro Software R. Prabu, P. R. Ranjil, prabuproficient@gmail.com 2/12/2014

CHECKLIST / LESSON LEARNT For generating 3D model of Underground station-Curved in Plan 1) Maximize the usage of Rectangular plates as possible. If the model is to be done in curve, then try to use Quadrilateral / Triangle plates.

2) Renumber Nodes / Plates / Beam element, such away to have separate list of Nodes / Element for Base Slab / Concourse Slab / Roof Slab / D-Wall.

For example:a) Base slab – 1 to 10000 b) Concourse slab – 10001 to 20000 c) Roof slab – 20001 to 30000 d) D-Wall – 30001 to 40000 Which will help to reduce the number of input lines in STAAD input editor and this will reduce the time for STAAD to regenerate the model every time.

3) Use parametric model to create plate mesh, instead of using “Generate Plate Mesh” command in STAAD. This will help to reduce the time taken to create meshing of plate.

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4) While using parametric modelling, it will automatically detect the Element / Nodes inside the boundary selected (during parametric modelling) and creates plate meshing by considering all element & nodes inside the boundary area automatically.

5) While using parametric modelling, keep in mind to select Option (A) “Only use selected boundary nodes, boundary edges not divided”, in advance meshing option shown in parametric modelling dialog box. So that it will help in avoiding improper connectivity of plates as shown below.

6) To change the Z-Axis of the plate element use “Command  Geometric Constant  Plate Reference Point” to change the Z-Direction of the plate element.

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7) Application of Lateral load over D-Wall a) Try to model the D-Wall with plate having same depth. This will help in applying lateral pressure over the DWall easily. b) Group each level of D-wall plates in separate group (DW1, DW2, DW3,‌‌.) so that trapezoidal load for applying lateral pressure can be easily applied for each group of plates. This will help in reducing the number of STAAD editor input lines, which will be created in case of using Hydrostatic command in STAAD.

8) For applying train live load equivalent pressure over plate, a) While doing parametric model, draw the element which shows the boundary region for applying train live load.

So that the plate where the train live load need to be applied will be segregated. By which the respective train live load can be easily applied.

9) In similar way as mentioned in point no. 8, draw member element showing the opening to be provided in slab level, so that the plates can be easily trimmed from the base model.

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10) For application of UPE wall load & platform loading, create a member running along the UPE wall in the model and by using the method specified in point no. 8, and assume a dummy property to the element and apply the UDL of UPE wall & Platform over the beam element.

11) Giving vertical spring stiffness @ base slab – For irregular plates: a) For a curved model, if we use parametric modelling tool, in which plates created at Base Slab / Concourse Slab / Roof Slab will be of irregular shapes & different sizes. b) But giving same vertical spring stiffness for all the node at the base level will give a wrong simulation, comparing to the actual soil stiffness. c) For which we can use Plate Mat command in STAAD. But in STAAD there is constrain of using both Multilinear spring & Tension/Compression spring simultaneously. d) To overcome this, please take a copy of the model and delete all the Element / Plates except plate in the base slab portion and apply Plate Mat foundation and check the “Print Influence Area” command in the Plate Mat dialog box (As shown below).

e) Analyse the model for a dummy load case and from the output file of STAAD, extract the influence area of each node at the base slab level to Microsoft Excel. f) Multiply the influence area of the respective node with the base slab vertical spring stiffness attained from the existing soil data. g) Apply this newly calculated Multi-linear spring stiffness at each joint to the base model.

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12) While following point no. 10, keep in mind to erase the “base slab vertical spring value” at the joints where the Pile / Barrette vertical spring already exist. So that duplication of support command can be avoided.

13) While using point no. 10, keep in mind while extracting the influence area from STAAD output, because in some cases the influence area of a single joint will split in to two lines and this area needs to be combined and used to get the correct result. This might result in “Multi-linear spring is not converging”-Warning.

14) Use STAAD select series 4 version (or) later to avoid “No joint are Multi-linear curve” error in STAAD.

15) Create separate group for application of horizontal springs at each level. For example Roof level / Concourse Level / Base Level / D-Wall Embedded Length.

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16) Create separate group for Column drops / Middle strips / End Strips (By selecting property assumed to section) in slab level, to change it graphical appearance, so that different colours can be given for each entity and this will be useful to check whether correct thickness is given to each entity.

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