add simple usage example

docs/make.jl

@@ -14,5 +14,6 @@ makedocs(modules=[JuliaFEM],
          sitename = "JuliaFEM",
          pages = [
                   "Introduction" => "index.md",
+                  "Examples" => "examples.md",
                   "API" => "api.md"
                  ])

docs/src/api.md

@@ -11,7 +11,17 @@ DocTestSetup = quote
 end
 ```
 
-```@autodocs
-Modules = [JuliaFEM]
+## Types
+
+```@docs
+JuliaFEM.Element
+JuliaFEM.Problem
+JuliaFEM.Elasticity
+```
+
+# Functions
+
+```@docs
+JuliaFEM.update!
 ```
 

docs/src/examples.md

@@ -0,0 +1,64 @@
+# Simple usage examples
+
+A simple example demonstrating the basic usage of package. Calculate a simple
+one element model. Add pressure load on top and support block symmetrically.
+
+```@example 1
+using JuliaFEM # hide
+X = Dict(
+    1 => [0.0, 0.0],
+    2 => [1.0, 0.0],
+    3 => [1.0, 1.0],
+    4 => [0.0, 1.0])
+```
+
+```@example 1
+element = Element(Quad4, [1, 2, 3, 4])
+update!(element, "geometry", X)
+update!(element, "youngs modulus", 288.0)
+update!(element, "poissons ratio", 1/3)
+```
+
+First define a field problem and add element to it
+```@example 1
+body = Problem(Elasticity, "test problem", 2)
+update!(body.properties,
+    "formulation" => "plane_stress",
+    "finite_strain" => "false",
+    "geometric_stiffness" => "false")
+body.elements = [element]
+```
+
+Then create element to carry on pressure
+```@example 1
+tr_el = Element(Seg2, [3, 4])
+update!(tr_el, "geometry", X)
+update!(tr_el, "displacement traction force 2", 288.0)
+traction = Problem(Elasticity, "pressure on top of block", 2)
+update!(traction.properties,
+    "formulation" => "plane_stress",
+    "finite_strain" => "false",
+    "geometric_stiffness" => "false")
+traction.elements = [tr_el]
+```
+
+Create boundary condition to support block at bottom and left
+```@example 1
+bc_el_1 = Element(Seg2, [1, 2])
+bc_el_2 = Element(Seg2, [4, 1])
+update!(bc_el_1, "displacement 2", 0.0)
+update!(bc_el_2, "displacement 1", 0.0)
+bc = Problem(Dirichlet, "add symmetry bc", 2, "displacement")
+bc.elements = [bc_el_1, bc_el_2]
+```
+
+Last thing is to create a solver, push problem to solver and solve:
+```@example 1
+solver = Solver(Linear, body, traction, bc)
+solver()
+```
+
+Displacement in node 3 is
+```@example 1
+solver("displacement", 0.0)[3]
+```