Experimental Campaign Design

MACRO-SCALE GOAL

To empirically validate the global structural behavior of the EPSB-RC system against absolute Solid RC and Bare Latticed baselines. This phase quantifies global kinematic instabilities, $P-\Delta$ amplifications, and macro-scale ductility ($\mu_\Delta$).

TARGET MECHANISMS

• Axial $P-\Delta$ & Slenderness: Validating the Shear-Modified Slenderness ($\bar{\lambda}_{mod}$) and isolating the Grid Penalty Factor ($\phi_{grid}$).
• FSDT Flexure Validation: Proving the "plane sections remain plane" hypothesis under OOP loading.
• 3D Seismic Vulnerability: Testing L-shaped and T-shaped flanged walls to quantify torsional warping and spatial shear lag.

ENGINEERING CONTEXT

To empirically confirm the theoretical bifurcation between material-dominated failure (squat, crushing) and stability-dominated failure (slender, buckling). Eccentric tests validate the Shear-Modified Magnification Factor for $P-\Delta$ effects.

SETUP SUMMARY

• Boundary: Pinned-Pinned kinematic condition ($k=1.0$).
• Slenderness: Squat ($\lambda=10, H=1500\text{mm}$) and Slender ($\lambda=20, H=3000\text{mm}$).
• Eccentricity: $e=0$, $e=25\text{mm}$ (kern), $e=50\text{mm}$ (flexural tension).

EXPECTED OUTPUTS

Ultimate capacity ($N_u$), exact buckling curvature profiles, and validation of passive lateral confinement by EPS against bare lattice crippling.

ENGINEERING CONTEXT

To evaluate transverse wind and seismic inertia resistance. Because of the "inverse-sandwich" voided topology, significant shear compliance necessitates validation of First-Order Shear Deformation Theory (FSDT) over classical Euler-Bernoulli theory.

SETUP SUMMARY

• Protocol A (4-Point Bending): Induces a pure moment zone to isolate flexural cracking and tension stiffening.
• Protocol B (Pneumatic Airbag): Simulates true uniformly distributed wind pressure over a massive $3750 \times 3000\text{ mm}$ flanged wall, preventing artificial point-load punching shear.

EXPECTED OUTPUTS

Verification of "plane sections remain plane" via strain gradients, interface separation tracking, and ultimate flexural capacity ($M_{Rd}$).

ENGINEERING CONTEXT

To evaluate seismic resilience, ductility ($\mu_\Delta$), and Specific Energy Absorption ($SEA$). Tests explicitly contrast Squat walls ("Shear-Softening" penalty) against Slender walls (flexural yielding).

3D FLANGED WALL TOPOLOGIES

• L-Shaped & T-Shaped Walls: Asymmetric shear centers induce severe 3D torsional warping and spatial shear lag during load reversals.
• Protocol: FEMA 461 / ACI 374.1 with moment-free axial pre-compression via hydraulically coupled jacks.

3D DIGITAL IMAGE CORRELATION (DIC)

Mandatory for 3D dynamic testing and complex shear fields. Eliminates "cosine errors" inherent to physical LVDTs as target points move out-of-plane (warping).

• "Virtual LVDTs": Tracks exact pixel displacements. Used to decompose total drift into flexure, diagonal shear, and sliding shear using Hiraishi (1984) equations.
• Immunity to Spalling: Physical X-LVDTs on bare concrete are destroyed during explosive web crippling. DIC safely maps plastic strain concentrations at the "Bottle-Neck" nodes.
• The EPS Blindspot: If EPS covers the wall, DIC only sees the foam. It cannot track internal RC core damage.

MACRO-ELEMENT LVDT NETWORK

Strictly required to measure the "Interface Integrity Constraint" and validate the FSDT assumptions.

• Through-Thickness Anchoring: To monitor the RC core while EPS is attached, horizontal LVDTs must be drilled through the EPS into the concrete. Otherwise, they only measure superficial foam crushing.
• Plane Sections Hypothesis: Cross-sectional strain profiling requires physical LVDTs on the external EPS, inner RC core, and back EPS to prove "plane sections remain plane."
• Base Rigid-Body Slip: Absolute-reference LVDTs at the foundation mathematically filter parasitic test-frame compliance from the actuator stroke.