{
  "schema": "girder-lesson-dimensions/1",
  "object_id": "girder-line2-variable-depth",
  "evidence_type": "teaching_assumption",
  "length_unit": "m",
  "force_unit": "N",
  "stress_unit": "Pa",
  "canonical_axes": {"x":"桥梁纵向", "y":"横向", "z":"向上"},
  "three_mapping": "(x,y,z) -> (x - 20,z,-y)",
  "spans_m": [20,20],
  "support_stations_m": [0,20,40],
  "cross_section": "solid_rectangle",
  "width_m": 4,
  "height_span_m": 1.2,
  "height_pier_default_m": 2.4,
  "height_pier_range_m": [1.2,3.2],
  "haunch_each_side_m": 8,
  "height_function": "u=max(0,1-abs(x-20)/8); h=1.2+(hPier-1.2)*u^2",
  "area_function": "4*h",
  "inertia_function": "4*h^3/12",
  "deck_top_elevation_m": 0,
  "pier_base_elevation_m": -5.8,
  "E_Pa": 30000000000,
  "base_load_N_per_m": 100000,
  "unit_weight_N_per_m3": 25000,
  "self_weight_default": false,
  "person_height_m": 1.7,
  "car_dimensions_m": [4.6,1.8,1.5],
  "context_asset_load": "不计入；仅为比例参照",
  "nominal_geometry_scale": 1,
  "deformation_display_scale": 150,
  "analysis_type": "linear_elastic_uncracked_Euler_Bernoulli_force_method",
  "not_solid_finite_element": true,
  "local_stress_display_rule": "只在等高段，距支点大于1.5h且距加高范围之外大于h时显示；课堂保守展示规则，非规范D区定义",
  "advanced_modes": {"curve":"shape_and_mechanism_only", "skew":"shape_and_mechanism_only", "width":"shape_and_mechanism_only"}
}