Storage Pillar Installation - Structural Substantiation

INTRODUCTION

Static-strength substantiation of two Storage Pillar installations on the port side of a DHC-8-100. The work combines load-case definition, FEMAP / SIMCENTER NASTRAN modeling, independent reaction validation, sheet-metal stress assessment, and fastener / attachment checks.

AircraftDHC-8-100Interior structural installation

ConfigurationTwo storage pillarsPort side · X417 and X437

AnalysisFEMAP · NASTRAN SOL 101Static stress substantiation

Governing resultMS = +0.06MS20426AD4 rivet shear

Technical figure from the Storage Pillar structural substantiation. — Storage Pillars locations at the PORT side of a DHC-8-100 aircraft.

DESIGN ASSESSMENT

GENERAL LAYOUT & LOAD PATH

Both installations use the same structural design. The aft pillar was selected for detailed FEM substantiation because it sees the higher vertical ultimate demand; the forward pillar is covered by comparison. Loads from the shelves enter the pillar through their attachment hardware, distribute through the sheet/extrusion structure, and react at the upper and lower aircraft interfaces.

AFT

Governing-model decision

Analyze the unique governing configuration rather than duplicate two equivalent models. The aft pillar controls the detailed assessment because the geometry is common and its vertical ultimate load is higher.

MATERIALS, JOINTS & MASS MODEL

The primary structure uses 2024-T3 ALCLAD sheet and 6061-T6511 extrusions, with Gillfab 4030 shelf panels. Source allowables were taken from the applicable MMPDS material entries and hardware data. The FEM preserves both structural and non-structural inertia rather than explicitly modeling every accessory.

PRIMARY SHEET2024-T3 ALCLAD

Ultimate tension 62 ksi; compression-yield allowable 37 ksi used for governing sheet checks.

EXTRUSIONS6061-T6511

Ultimate tension 38 ksi; compression-yield allowable 34 ksi used for governing extrusion checks.

MASS BASIS75.699 lb_m

Structure, removed/non-structural content, shelves and payload are retained at representative centers of gravity.

Key source joint allowables retained for the governing checks.

Hardware	Source allowable used	Check type
MS20426AD4 rivet	363 lb_f	Shear
MS20470AD4 rivet	389 lb_f	Shear
AN525-10R joint	1,496 lb_f	Source-used governing joint value
Upper attachment stud	341 lb_f	Shear
Lower attachment stud	2,000 lb_f	Shear
NAS1834-3-500 insert	1,166 / 645 lb_f	Shear / tension

Mass idealization. The source model carries 17.935 lb_m of modeled structure, 27.642 lb_m of removed/non-structural content, and the three shelf masses/payload representations, for a listed total of 75.699 lb_m. Non-structural content is represented through NSM/equivalent mass so inertial demand is preserved without unnecessary geometric detail.

STATIC STRESS ANALYSIS

LOAD CASES

The structural envelope combines governing flight loads with FAR 25.561 emergency-landing accelerations. Flight cases are converted to ultimate values as required by the source analysis; emergency values are already ultimate.

Governing ultimate load cases applied to the FEM.

Load Case Number	Load Factor Direction	Ultimate Load Value ( $N_u$ )[g]	Governing basis
1	Up	6.24	Flight
2	Down	7.995	Flight
3	Outboard	3.0	Emergency landing
4	Inboard	3.0	Emergency landing
5	Forward	9.0	Emergency landing
-	Aft	1.5	Covered conservatively by Forward case

FINITE ELEMENT ANALYSIS (FEA)

GLOBAL IDEALIZATION

2D midsurface plates

Sheet and extrusion-wall behavior is captured with membrane, bending and shear response without unnecessary solid-element cost.

FEATURE CONTROL

Retain structural detail

Fillets and structural fastener holes remain where local gradients matter; non-critical holes and accessory geometry are suppressed.

JOINT IDEALIZATION

CBUSH / spider connectors

Fastener-hole spiders use 1×10⁷ lb_f/in stiffness to transfer joint loads and permit direct connector-reaction recovery.

MASS IDEALIZATION

Shelf loads at actual CoG

Mass elements place shelf inertia and overturning effects at the correct centers of gravity and transfer them into the attachment patterns.

GEOMETRY & PROPERTIES

The CAD geometry was simplified in FEMAP and midsurfaces extracted for the primary sheet structure. Non-structural accessories were removed from the mesh but their combined mass was retained. The Storage Pillar Panel-to-Back Panel interface was simplified with translational RBE2 coupling where the omitted rivet pattern was not required for the global load-path assessment.

LOADS & BOUNDARY CONDITIONS

BOUNDARY CONDITIONSUpper attachments

Tx and Ty restrained.

Forward lower attachment

Tx and Ty restrained.

Aft lower attachment

Tx, Ty and Tz restrained.

Engineering rationale

The restraint set follows the directional capability of the attachment system while avoiding unnecessary fixity. This preserves the intended reaction path and reduces artificial stiffening.

MESH & SOLVER

MESH441,491 2D elements

97.32% QUAD4 and only 0.46% TRI3. Local refinement is concentrated at holes, fillets and attachment regions; pads/washers stabilize hole-region load introduction.

SOLVERSESTATIC · SOL 101

Linear static analysis in SIMCENTER NASTRAN. WTMASS is enabled for the lb_m–in–s unit system so force and stress output is interpreted consistently as lb_f and psi.

FEA RESULTS & VALIDATION

INDEPENDENT REACTION CHECK

Before using the detailed stress and connector results, attachment reactions were cross-checked against an independent 3D rigid-body equilibrium model for the 9 g forward and 3 g inboard cases. The close agreement provides a global load-path sanity check independent of the FEM.

Reaction force comparison from the FE model and from the 3D Rigid Body Analysis.

Node	Location	FWD		INBOARD
		Rx		Ry
		FE	3D-RBA	FE	3D-RBA
3548	LOWER - AFT	205.84	196.85	-63.88	-65.37
3761	LOWER - FWD	178.95	196.85	-64.38	-65.92
7880	UPPER - AFT	144.57	143.8	-47.63	-47.71
8007	UPPER - FWD	142.69	143.8	-48.13	-48.11

SHEET / EXTRUSION STRESS ASSESSMENT

Principal stresses were reviewed on both plate faces for every load case. The raw FEM contains highly localized peaks beside retained holes and rigid-body connections; the source assessment identifies these as connection/geometric singularity-type effects and evaluates the surrounding structural stress field for the strength check. The localized peaks remain documented rather than being hidden.

Governing stress-field values used for material margins after the source peak-stress treatment.

Material	Governing tensile stress	Tension allowable	Governing compression stress	Compression allowable	Minimum MS
2024-T3 ALCLAD	40.520 ksi	62 ksi	33.035 ksi	37 ksi	+0.12
6061-T6511	31.653 ksi	38 ksi	30.904 ksi	34 ksi	+0.10

{M.S}_{AL2024 - T3\ - T} = \frac{62}{40.52\ \ } - 1 = 0.53

{M.S}_{AL2024 - T3 - C} = \frac{37}{33.035\ } - 1 = 0.12

\boxed{{M.S}_{AL2024 - T3} = 0.12\ }

→PASS

{M.S}_{AL6061 - T6511\ - T} = \frac{38}{31.653\ \ } - 1 = 0.2

{M.S}_{AL6061 - T6511\ - C} = \frac{34}{30.904\ } - 1 = 0.1

\boxed{{M.S}_{AL6061 - T6511\ } = 0.1\ }

→ PASS

FASTENER & ATTACHMENT RESULTS

Connector reactions were resolved into the applicable shear/tension components and compared with the source joint/fastener allowables using the report’s 1.15 fitting-factor convention where applied. Rather than repeating every connector table, the governing demand for each hardware family is retained below.

Governing connector / attachment results from the source analysis.

Check	Governing demand	Source allowable / basis	Result
MS20426AD4 rivet	297.41 lb_f shear · 9 g forward	363 lb_f · 1.15 factor	MS = +0.06
MS20470AD4 rivet	201.71 lb_f shear · 3 g outboard	389 lb_f · 1.15 factor	MS = +0.68
AN525-10R joint	269.30 lb_f shear · 7.995 g down	1,496 lb_f source-used value · 1.15 factor	MS ≫ 1
Upper attachment stud	146.60 lb_f shear	341 lb_f · 1.15 factor	MS = +1.02
Lower attachment stud	230.79 lb_f shear	2,000 lb_f · 1.15 factor	MS ≫ 1
Shelf AN525-10R16 / inserts	182.17 lb_f shear; 83.62 lb_f tension · 9 g forward	1,166 / 645 lb_f minimum insert shear/tension values cited by source	PASS by observation

Representative governing rivet calculation:

{M.S}_{MS20426AD4\ } = \frac{363\ }{297.41 \times 1.15} - 1

\boxed{{M.S}_{MS20426AD4\ } = 0.06\ \ \ }

→ PASS

Attachment-stud checks:

{M.S}_{LowerStud\ } = \frac{2000}{230.79 \times 1.15} - 1

{M.S}_{UpperStud\ } = \frac{341}{146.60 \times 1.15} - 1

\boxed{{M.S}_{LowerStud\ } \gg 1\ \ \ }

→ PASS

\boxed{{M.S}_{UpperStud\ } = 1.02\ \ \ }

→ PASS

SUBSTANTIATION OUTCOME

GOVERNING CHECKMS20426AD4MS = +0.06

2024-T3PASSMinimum MS = +0.12

6061-T6511PASSMinimum MS = +0.10

ATTACHMENTSPASSUpper-stud MS = +1.02

REFERENCES

Structural Materials & Allowables

MMPDS-15 - Metallic Materials Properties Development and Standardization
AMS-QQ-A-250/5 - Aluminum Alloy Alclad 2024 Sheet and Plate
AMS-QQ-A-200/8 - Aluminum Alloy 6061 Extruded Bars, Rods, Shapes and Tubes

Regulatory Load Basis

Federal Aviation Regulations - 14 CFR Part 25

Fasteners & Attachment Hardware

MS20426 / MS20470 solid-rivet technical data
AN525 washer-head screw technical data
NAS1834 insert technical data
FE200744 lower-attachment stud technical data
Upper-attachment stud allowable data used in the source report

Composite Material Data

Gillfab 4030-500003FC2T material data