Flexural Members: Beams, Slabs, and Structural ECC Applications
1. Learning objectives
- Explain why material-level tensile ductility must be demonstrated at member level (beam/slab) before structural claims.
- Read flexural load-deflection results of ECC/HPFRCC members and identify deflection-hardening vs softening.
- Understand composite action concepts: ECC link slabs, layered/combined ECC-concrete sections, and bridge deck applications.
- Connect member-level crack width control to durability of real structures.
2. Key concepts
- Deflection hardening in flexure (member level) vs strain hardening in tension (material level)
- Moment capacity and ductility of ECC beams; reinforcement synergy
- ECC link slab: jointless bridge deck connection, reflective cracking suppression
- Layered systems: ECC layer for cover/durability protection
- Shear behavior of ECC beams
- Crack width as a durability design parameter at structural scale
3. Minimal theory
ECC's multiple microcracking allows reinforced flexural members to maintain narrow crack widths under service load, improving transport-related durability. In link slabs, ECC accommodates rotation and displacement between girders without joints. The distinction between direct tensile strain capacity (material) and deflection capacity (member) is essential for correct interpretation.
4. Source-grounded evidence
- Book anchor: `../../00_sources/victor_li_book/` (Ch. 9 application chapters; use `figure_index/09 application_figures.md` to locate figures).
- Extension package: `../../03_papers/ecc_beam_extension/` (53 paper cards).
- Claim-evidence rows: `../../07_visualization/ecc_beam_extension_claim_evidence_matrix.csv` (214 rows).
5. Representative papers (from ecc_beam_extension)
- Flexural performance of green ECC / EGC beams.
- High-strength ECC and HPFRCC beam studies.
- ECC link slab and composite bridge deck field/structural tests.
Instructors should pull exact citations from `../../03_papers/ecc_beam_extension/_index.md`.
6. Figures/tables to show later
- Beam load-deflection curves comparing ECC vs concrete members.
- Link slab deformation schematic and crack pattern photos.
- Crack width evolution vs service load in beams.
7. Discussion questions
1. Why does a material with 3–5% tensile strain capacity not guarantee a "ductile" beam?
2. What failure modes still govern ECC beam design even with ductile ECC?
3. How does the ECC link slab reduce maintenance compared with conventional expansion joints?
4. Which crack width threshold is relevant for corrosion protection, and who measured it?
8. Assignment idea
Select two papers from `ecc_beam_extension`: one material-level study and one member-level study. Compare their reported capacities and explain why the numbers cannot be directly compared. Submit as a one-page memo with claim-evidence rows cited.
9. Linked Atlas nodes
- `../../02_concepts/crack_width_control.md` (Tier 1)
- `../../05_experiments/flexural_testing.md` (Tier 1)
- `../../04_material_systems/link_slab.md`
- `../../04_material_systems/composite_bridge_deck.md`
- `../../05_experiments/shear_behavior.md`
- `../../05_experiments/structural_component_testing.md`
10. Suggested reading path
1. This module.
2. `../../03_papers/ecc_beam_extension/_index.md`.
3. Three beam/link-slab paper cards chosen from the index.
4. Five claim-evidence rows from `ecc_beam_extension_claim_evidence_matrix.csv`.