Design overview
Block & load model
Governing checks
Analysis basis
Separate X-Z and Y-Z checks using the source's written equations. Adopted geometry is independent of the schematic. A passing result applies only to these checks; it is not a complete structural or geotechnical design.
Foundation dimensions, net concrete volume, and centroid arms are adopted engineering inputs. Arms are measured from the corresponding base edge; heights are measured above the foundation. The JICA example uses an irregular footprint with separate effective base lengths.
Plan coordinate worksheet
Plan properties only. Coordinates do not change adopted volume, effective base lengths, or moment arms.
Thermal combinations
Resultant magnitude = √(Rx² + Ry² + Rz²)Documented method, with visible limits
The attached Penstock Anchor Block 3D.pdf is the 21-page penstock section of the JICA Chone-Portoviejo study. This calculator follows Section 2.1's component equations and four thermal combinations, evaluated separately in two planes with both earthquake directions.
Open the official JICA source · Verification and discrepancy register
Acceptance criteria
- Eccentricity: e = |B/2 − ΣM/ΣV| < B/6.
- Sliding: Fs = Nλ/|ΣH| > 2.0, where N = −ΣV > 0.
- Bearing: qmax = N/A (1 + 6e/B) < qa, only for full compression contact.
The original app's additional overturning moment-ratio criterion is not specified by this reference and is not used. Strict comparisons follow the printed inequalities. Equality does not pass.
Source discrepancies
- Table 2.1.1 gives a positive downstream water-friction y component for block 2-3, while the written component equation is negative. This app uses the written equation.
- The source's scalar totals are not vector magnitudes. This app reports the Euclidean magnitude of each combined force, alongside its signed components.
- Small differences from printed values remain because calculations use full precision and an explicit g = 9.81 m/s². The source's displayed momentum force is consistent with g near 9.8. Presets use the rounded weight and centroid arms adopted in the stability sheets.
- The generic seismic example on printed page 2-8 uses different lengths from the two block cases. This app calculates seismic loads from each case's actual inputs.
Geometry and units
For the source presets, A = 23.221 m², Bx = 5.901 m, and By = 4.719 m are separate adopted quantities. A is not Bx × By. The drawing is a schematic of these adopted values, not a solid-volume calculation. The coordinate worksheet reports polygon centroids without reordering the boundary. It does not infer a three-dimensional solid from independent sections.
Forces use tonne-force (tf), with water unit weight 1 tf/m³ and g = 9.81 m/s² as the calculation convention. Shell weight uses the source's thin-wall expression πDtγs. Slopes are signed, positive descending, in the source's local axis convention. The horizontal bend is 0 to 179 degrees. Mirrored or arbitrarily rotated alignments need a separately verified transformation.
Applicability
This is a reproduction of a project-specific plane-check method, not a universal penstock design standard. It does not check simultaneous biaxial bearing, full horizontal resultant sliding, torsion, reinforcement, pipe shell stresses, anchor-ring capacity, groundwater uplift, soil cover, passive resistance, or load combinations beyond the stated method. Heads must already include the governing hydraulic condition. Arbitrary 3D bends require independent verification of the source's component assumptions.
When N ≤ 0, foundation contact fails. When e > B/6, the source's linear bearing equation is outside its domain, so bearing is marked unavailable and the case fails. No unreferenced partial-contact capacity is substituted.
Reproducibility
The engine uses full precision until display. Reports, tables, and CSV exports share the same result object. Regression tests cover the printed block 1-3 results, all 32 printed stability cases using their published loads, source inconsistencies, and invalid or limiting inputs. See the repository's verification record for tolerances and exclusions.