feat(rebar): rebar strength per 규격 prefix as inputs on ③ (D SD300, H SD400, S SD500)

fyH and fyS become a grade per prefix (D · H · S), chosen from SD300 · SD400 · SD500. The defaults are the P1 values, so
the P1 results do not change. Each bar takes its grade from its 규격 (fyOf). The 철근표 has a 강도 column. Older files
that stored fyH / fyS are read into the grade map. Only fck is still an assumed value (I02). Approved 2026-10-23.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

index.html

@@ -178,8 +178,9 @@
           <section class="common" aria-labelledby="common-title">
             <p id="common-title" class="lbl">공통 설정</p>
             <label class="mat">fck (MPa) <input id="mat-fck" type="number" step="any" /></label>
-            <label class="mat">fy H · SD400 (MPa) <input id="mat-fyh" type="number" step="any" /></label>
-            <label class="mat">fy S · SD500 (MPa) <input id="mat-fys" type="number" step="any" /></label>
+            <label class="mat">D 규격 강도 <select id="mat-grade-d"><option value="300" selected>SD300</option><option value="400">SD400</option><option value="500">SD500</option></select></label>
+            <label class="mat">H 규격 강도 <select id="mat-grade-h"><option value="300">SD300</option><option value="400" selected>SD400</option><option value="500">SD500</option></select></label>
+            <label class="mat">S 규격 강도 <select id="mat-grade-s"><option value="300">SD300</option><option value="400">SD400</option><option value="500" selected>SD500</option></select></label>
             <p id="mat-note" class="muted small"></p>
           </section>
         </aside>

src/core/rebar/column.ts

@@ -1,4 +1,4 @@
-import { DEFAULT_MATERIAL, developmentLength, hookLength, Material, NOMINAL_DIAMETER, spliceLength } from './common';
+import { DEFAULT_MATERIAL, developmentLength, fyOf, hookLength, Material, NOMINAL_DIAMETER, spliceLength } from './common';
 import { layers } from './footing';
 
 /**
@@ -95,7 +95,7 @@ export function columnRebar(x: ColumnInput = COLUMN_P1, m: Material = DEFAULT_MA
   const r1 = x.D / 2 - x.c;
   const r2 = r1 - dS32;
   const zTop1 = x.Hc + x.hcop - x.eP1;
-  const lD2 = developmentLength(dS32, m.fyS, m.fck);
+  const lD2 = developmentLength(dS32, fyOf(m, 'S32'), m.fck);
   const zTop2 = x.Hc + lD2;
   // Bottom of P1 and P2: 확대기초 하면 2단 (B7) 위 + (d_B7 + d_P1)/2 (기둥철근.md §3.2, the same for both).
   const zBot = -x.Hf + layers(x.Hf).B7 + (NOMINAL_DIAMETER.S19 + dS32) / 2;
@@ -137,7 +137,7 @@ export function columnRebar(x: ColumnInput = COLUMN_P1, m: Material = DEFAULT_MA
   const p6Length = p6Straight + 2 * Math.round(p6Hook); // 135 mm per hook, as in the document
 
   // P3 lap: Q-C6 is open; recommended = 1.3·l_d of H19 with the material inputs.
-  const lapP3 = spliceLength(dH19, m.fyH, m.fck);
+  const lapP3 = spliceLength(dH19, fyOf(m, 'H19'), m.fck);
   const p3Length = 2 * Math.PI * tieRadius + lapP3;
   const p5Length = 2 * Math.PI * tieRadius;
 

src/core/rebar/common.ts

@@ -1,18 +1,42 @@
 /**
  * ③ 철근배근 공통 규칙 (spec §6.2 · plan C1). Lengths in mm, stresses in MPa.
- * fck and fy are inputs. The defaults below are assumed values and must be shown as such (I02).
+ * fck and the rebar grade per 규격 prefix are inputs. fck's default is an assumed value (I02); the grades' defaults are confirmed.
  */
-/** Material inputs of ③ 공통 설정 (spec §6.2). fck and fy are inputs; the defaults are assumed values (I02). */
+/** Rebar strength choices on ③ (SD300 · SD400 · SD500, MPa). */
+export const GRADE_CHOICES = [300, 400, 500] as const;
+
+/** Bar family by 규격 prefix: D · H · S. */
+export type GradeKey = 'D' | 'H' | 'S';
+
+/** Material inputs of ③ 공통 설정 (spec §6.2). fck and the grade per prefix are inputs. */
 export interface Material {
   /** 콘크리트 강도 fck (MPa). */
   fck: number;
-  /** H = SD400 항복강도 (MPa). */
-  fyH: number;
-  /** S = SD500 항복강도 (MPa). */
-  fyS: number;
+  /** 규격 접두어별 철근 강도 (MPa): D = SD300, H = SD400, S = SD500 (입력). */
+  grade: Record<GradeKey, number>;
 }
 
-export const DEFAULT_MATERIAL: Material = { fck: 27, fyH: 400, fyS: 500 };
+export const DEFAULT_MATERIAL: Material = { fck: 27, grade: { D: 300, H: 400, S: 500 } };
+
+/** Yield strength (MPa) of a bar from its 규격, e.g. H19 → the H grade. */
+export function fyOf(m: Material, size: string): number {
+  return m.grade[size.charAt(0) as GradeKey];
+}
+
+/**
+ * Reads a material from the current shape, or from an older file that stored fyH / fyS.
+ * A value outside GRADE_CHOICES falls back to the default for that prefix.
+ */
+export function materialFrom(raw: unknown): Material {
+  const r = (raw ?? {}) as { fck?: unknown; grade?: Partial<Record<GradeKey, unknown>>; fyH?: unknown; fyS?: unknown };
+  const pick = (v: unknown, fallback: number) => ((GRADE_CHOICES as readonly number[]).includes(v as number) ? (v as number) : fallback);
+  const grade = {
+    D: pick(r.grade?.D, DEFAULT_MATERIAL.grade.D),
+    H: pick(r.grade?.H ?? r.fyH, DEFAULT_MATERIAL.grade.H),
+    S: pick(r.grade?.S ?? r.fyS, DEFAULT_MATERIAL.grade.S),
+  };
+  return { fck: typeof r.fck === 'number' ? r.fck : DEFAULT_MATERIAL.fck, grade };
+}
 
 /** Members that can take their own fck on ② (부재 카드). Other members always use the 공통 fck. */
 export type FckMember = 'column' | 'coping' | 'footing';
@@ -27,9 +51,9 @@ export function materialFor(common: Material, byMember: FckByMember, member: Fck
   return { ...common, fck: byMember[member] ?? common.fck };
 }
 
-/** True while the values are the assumed defaults (정보 I02 on the rebar screen). */
+/** True while fck is the assumed default (정보 I02 on the rebar screen). The grades are confirmed inputs (decision 2026-10-23). */
 export function isAssumedMaterial(m: Material): boolean {
-  return m.fck === DEFAULT_MATERIAL.fck && m.fyH === DEFAULT_MATERIAL.fyH && m.fyS === DEFAULT_MATERIAL.fyS;
+  return m.fck === DEFAULT_MATERIAL.fck;
 }
 
 export const MATERIAL_DEFAULTS = {

src/core/rebar/coping-main.ts

@@ -1,4 +1,4 @@
-import { DEFAULT_MATERIAL, hookLength, Material, NOMINAL_DIAMETER, spliceLength } from './common';
+import { DEFAULT_MATERIAL, fyOf, hookLength, Material, NOMINAL_DIAMETER, spliceLength } from './common';
 
 /**
  * C1–C8 상·하면 주철근 (plan C3 continued). Source: RAG/코핑철근.md §5, 2026-10-22 최종 정리.
@@ -73,7 +73,7 @@ export function topBarLength(L: number, k: number): number {
  */
 export function bottomPiece(m: Material = DEFAULT_MATERIAL): { path: number; ls: number; piece: number } {
   const path = 2 * MAIN.slopeEach + MAIN.level;
-  const ls = spliceLength(NOMINAL_DIAMETER.H29, m.fyH, m.fck);
+  const ls = spliceLength(NOMINAL_DIAMETER.H29, fyOf(m, 'H29'), m.fck);
   const lh = hookLength('main90', NOMINAL_DIAMETER.H29);
   return { path, ls, piece: path / 2 + ls / 2 + lh };
 }

src/core/rebar/coping.ts

@@ -2,7 +2,7 @@
  * 코핑 철근 (plan C3). Source: RAG/코핑철근.md, 2026-10-22 최종 정리 (spec §6.4 is older and is not used here).
  * Positions are along the coping length from its start, in mm.
  */
-import { DEFAULT_MATERIAL, developmentLength, hookLength, Material, NOMINAL_DIAMETER } from './common';
+import { DEFAULT_MATERIAL, developmentLength, fyOf, hookLength, Material, NOMINAL_DIAMETER } from './common';
 export const COPING_REBAR = {
   /** 피복 (최외측 철근 중심까지). */
   cover: 100,
@@ -144,7 +144,7 @@ export const C14_INSET = COPING_REBAR.cover + (NOMINAL_DIAMETER.H25 + NOMINAL_DI
 
 /** Development length l_d of H19 (882 for fy 400, fck 27), rounded to mm as the document does (§7.2). */
 export function stepDevLength(m: Material = DEFAULT_MATERIAL): number {
-  return Math.round(developmentLength(NOMINAL_DIAMETER.H19, m.fyH, m.fck));
+  return Math.round(developmentLength(NOMINAL_DIAMETER.H19, fyOf(m, 'H19'), m.fck));
 }
 
 export interface C14Bar {

src/core/rebar/summary.ts

@@ -4,7 +4,7 @@ import { bottomPiece, topBarLength, widthLayout } from './coping-main';
 import { shearBars, shearBarsMulti, copingSideBars, SIDE_HOOK_LEG, c14Bars, c14Length, stairBars, stepDevLength, undersideAt, shearULength, capLength, PIECES_PER_POSITION } from './coping';
 import { columnRebar, COLUMN_P1 } from './column';
 import { bottomBars, crossBars, sideBars, assemblyBars, shearB9 } from './footing';
-import { DEFAULT_MATERIAL, FckByMember, isAssumedMaterial, Material, materialFor, splitPieces } from './common';
+import { DEFAULT_MATERIAL, FckByMember, fyOf, isAssumedMaterial, Material, materialFor, splitPieces } from './common';
 
 /** 근거 badge (spec §6.1): where the value comes from. */
 export type Basis = 'input' | 'default' | 'calc' | 'assumed';
@@ -126,7 +126,7 @@ export function rebarSummary(
   // The I02 note stays while the common values are the assumed ones, unless every fck-bearing member has its own fck.
   const ownFck = (['column', 'coping', 'footing'] as const).every((k) => byMember[k] !== undefined);
   if (isAssumedMaterial(common) && !ownFck) {
-    warnings.push({ code: 'I02', message: `fck ${common.fck} MPa · fy ${common.fyH} / ${common.fyS} MPa는 가정값입니다. 정착·이음 길이에 반영됩니다. 공통 설정에서 확인하세요.`, target: 'common' });
+    warnings.push({ code: 'I02', message: `fck ${common.fck} MPa는 가정값입니다. 정착·이음 길이에 반영됩니다. 공통 설정에서 확인하세요.`, target: 'common' });
   }
   const L = model.copingL * 1000;
   const B = model.copingB * 1000;
@@ -228,7 +228,7 @@ export function rebarSummary(
       }
     }
     for (const b of agg.values()) {
-      const split = splitPieces(b.length, 25.4, mFooting.fyS, mFooting.fck, STANDARD_BAR);
+      const split = splitPieces(b.length, 25.4, fyOf(mFooting, b.size), mFooting.fck, STANDARD_BAR);
       if (split && b.length > STANDARD_BAR && b.name !== 'B9') {
         rows.push({ member: 'footing', name: b.name, size: b.size, count: b.count, length: split.pieceLength, note: `${b.note}, 2조각 이음 (추천안, 겹침 ${Math.round(split.lap)})` });
         warnings.push({ code: 'RB-F08', message: `${b.name} 길이 ${Math.round(b.length)} mm > 정척 ${STANDARD_BAR} mm: 2조각 이음을 추천안으로 적용 (Q-B6).`, target: 'footing', bar: b.name });

src/main.ts

@@ -13,7 +13,7 @@ import { pileGeometry } from './core/geometry';
 import { rebarSummary, type RebarRow } from './core/rebar/summary';
 import { shearSegments } from './core/rebar/coping';
 import { buildRebar3D, type RebarColorMode, type RebarScene } from './view/rebar3d';
-import { DEFAULT_MATERIAL, FCK_MEMBERS, isAssumedMaterial, type FckByMember, type FckMember, type Material } from './core/rebar/common';
+import { DEFAULT_MATERIAL, FCK_MEMBERS, fyOf, GRADE_CHOICES, isAssumedMaterial, materialFrom, type FckByMember, type FckMember, type GradeKey, type Material } from './core/rebar/common';
 import { allVisibleChecked, setVisibleChecked, type TypeFilter } from './core/selection';
 import { choose, defaultSummary, isSelectable, SHAPE_GROUPS, UNDEFINED_REASON, type MemberId } from './core/shape-options';
 import { parseProject, SCHEMA_VERSION, serializeProject, type ProjectFile, type ProjectInfo } from './core/project';
@@ -838,7 +838,7 @@ function renderRebar(): void {
   const table = el('table', undefined, 'grid-table rebar-table');
   const head = el('thead');
   const hr = el('tr');
-  for (const h of ['구분', '번호', '규격', '간격', '실간격', '위치', '방향', '형상', '길이 (mm)', '개수', '근거', '비고']) hr.appendChild(el('th', h));
+  for (const h of ['구분', '번호', '규격', '강도', '간격', '실간격', '위치', '방향', '형상', '길이 (mm)', '개수', '근거', '비고']) hr.appendChild(el('th', h));
   head.appendChild(hr);
   table.appendChild(head);
   const body = el('tbody');
@@ -855,6 +855,7 @@ function renderRebar(): void {
       el('td', ROLE[r.name] ?? '—'),
       nameCell,
       el('td', r.size),
+      el('td', /^[DHS]\d/.test(r.size) ? `SD${fyOf(state.material, r.size)}` : '—'),
       el('td', r.spacing),
       el('td', r.actual),
       el('td', r.position),
@@ -952,9 +953,10 @@ function renderMaterial(): void {
   const m = state.material;
   const assumed = isAssumedMaterial(m);
   $<HTMLInputElement>('mat-fck').value = String(m.fck);
-  $<HTMLInputElement>('mat-fyh').value = String(m.fyH);
-  $<HTMLInputElement>('mat-fys').value = String(m.fyS);
-  $('mat-note').textContent = assumed ? '가정값 (I02): 입력을 바꾸면 정착·이음 길이가 달라집니다.' : '입력값을 사용합니다.';
+  for (const k of ['d', 'h', 's'] as const) {
+    $<HTMLSelectElement>(`mat-grade-${k}`).value = String(m.grade[k.toUpperCase() as GradeKey]);
+  }
+  $('mat-note').textContent = assumed ? 'fck 가정값 (I02): 입력을 바꾸면 정착·이음 길이가 달라집니다.' : '입력값을 사용합니다.';
 }
 
 /** Sets or clears one member's fck. An empty value clears it, so the member uses the 공통 fck again. */
@@ -1001,14 +1003,15 @@ function renderMemberFck(box: HTMLDivElement, member: FckMember): void {
   box.appendChild(row);
 }
 
-function setMaterial(key: keyof Material, raw: string): void {
+function setMaterial(key: 'fck' | GradeKey, raw: string): void {
   const value = Number(raw);
-  if (!Number.isFinite(value) || value <= 0) {
-    setStatus('공통 설정 값은 0보다 큰 숫자여야 합니다.');
+  const valid = key === 'fck' ? Number.isFinite(value) && value > 0 : (GRADE_CHOICES as readonly number[]).includes(value);
+  if (!valid) {
+    setStatus(key === 'fck' ? '공통 설정 fck는 0보다 큰 숫자여야 합니다.' : '철근 강도는 SD300 · SD400 · SD500 중 하나여야 합니다.');
     renderMaterial();
     return;
   }
-  state.material = { ...state.material, [key]: value };
+  state.material = key === 'fck' ? { ...state.material, fck: value } : { ...state.material, grade: { ...state.material.grade, [key]: value } };
   // The 3D bars depend on the material too (their lengths), so the scene is rebuilt with it.
   setupScene();
   renderAll();
@@ -1180,7 +1183,7 @@ function openProjectText(text: string, saved: boolean): void {
   state.project = { ...parsed.project };
   state.source = parsed.source;
   state.history = parsed.history;
-  state.material = parsed.common ? { ...parsed.common } : { ...DEFAULT_MATERIAL };
+  state.material = materialFrom(parsed.common);
   state.fckByMember = { ...parsed.fckByMember };
   state.piers = parsed.piers.map((p) => ({
     ...buildEntry(p.input, false),
@@ -1414,8 +1417,9 @@ $<HTMLButtonElement>('nav-shape').addEventListener('click', () => setStage('shap
 $<HTMLButtonElement>('nav-plan').addEventListener('click', () => setStage('plan'));
 $<HTMLButtonElement>('nav-rebar').addEventListener('click', () => setStage('rebar'));
 $<HTMLInputElement>('mat-fck').addEventListener('change', (ev) => setMaterial('fck', (ev.target as HTMLInputElement).value));
-$<HTMLInputElement>('mat-fyh').addEventListener('change', (ev) => setMaterial('fyH', (ev.target as HTMLInputElement).value));
-$<HTMLInputElement>('mat-fys').addEventListener('change', (ev) => setMaterial('fyS', (ev.target as HTMLInputElement).value));
+for (const k of ['D', 'H', 'S'] as const) {
+  $<HTMLSelectElement>(`mat-grade-${k.toLowerCase()}`).addEventListener('change', (ev) => setMaterial(k, (ev.target as HTMLSelectElement).value));
+}
 $<HTMLButtonElement>('member-regen').addEventListener('click', () => {
   const pier = activePier();
   if (pier) regenerateOne(pier.input.name);

tests/project.test.ts

@@ -68,8 +68,8 @@ describe('project file round trip (spec §8, plan B3)', () => {
 describe('③ 공통 설정 in the project file', () => {
   it('fck and fy are kept through save and open; older files get the defaults through the app', () => {
     const p = sampleProject();
-    const withCommon = { ...p, common: { fck: 35, fyH: 400, fyS: 500 } };
-    expect(parseProject(serializeProject(withCommon)).common).toEqual({ fck: 35, fyH: 400, fyS: 500 });
+    const withCommon = { ...p, common: { fck: 35, grade: { D: 300, H: 400, S: 500 } } };
+    expect(parseProject(serializeProject(withCommon)).common).toEqual({ fck: 35, grade: { D: 300, H: 400, S: 500 } });
     expect(parseProject(serializeProject(p)).common).toBeUndefined();
   });
 });

tests/rebar-grade.test.ts

@@ -0,0 +1,36 @@
+import { describe, expect, it } from 'vitest';
+import { buildPier } from '../src/core/geometry';
+import { DEFAULT_MATERIAL, fyOf, isAssumedMaterial, materialFrom } from '../src/core/rebar/common';
+import { rebarSummary } from '../src/core/rebar/summary';
+import { loadP1 } from './helpers';
+
+describe('③ 철근 강도: 규격 접두어별 입력 (승인 2026-10-23)', () => {
+  it('defaults: D = SD300, H = SD400, S = SD500, the same as the P1 values', () => {
+    expect(DEFAULT_MATERIAL.grade).toEqual({ D: 300, H: 400, S: 500 });
+    expect(fyOf(DEFAULT_MATERIAL, 'H19')).toBe(400);
+    expect(fyOf(DEFAULT_MATERIAL, 'S32')).toBe(500);
+    expect(fyOf(DEFAULT_MATERIAL, 'D22')).toBe(300);
+  });
+
+  it('only fck is assumed now; the grades are confirmed inputs', () => {
+    expect(isAssumedMaterial(DEFAULT_MATERIAL)).toBe(true);
+    expect(isAssumedMaterial({ ...DEFAULT_MATERIAL, fck: 35 })).toBe(false);
+    expect(isAssumedMaterial({ ...DEFAULT_MATERIAL, grade: { D: 300, H: 400, S: 400 } })).toBe(true);
+  });
+
+  it('an older file that stored fyH / fyS is read into the grade map', () => {
+    expect(materialFrom({ fck: 35, fyH: 400, fyS: 400 })).toEqual({ fck: 35, grade: { D: 300, H: 400, S: 400 } });
+  });
+
+  it('a value outside SD300 · SD400 · SD500 falls back to the default for its prefix', () => {
+    expect(materialFrom({ fck: 27, grade: { S: 600 } }).grade.S).toBe(500);
+    expect(materialFrom(undefined)).toEqual(DEFAULT_MATERIAL);
+  });
+
+  it('the P1 values do not change with the defaults (S = SD500 gives the same C7 length)', () => {
+    const model = buildPier(loadP1());
+    const base = rebarSummary(model).rows.find((r) => r.name === 'C7')!.length;
+    const same = rebarSummary(model, materialFrom({ fck: 27, grade: { D: 300, H: 400, S: 500 } })).rows.find((r) => r.name === 'C7')!.length;
+    expect(same).toBe(base);
+  });
+});

tests/rebar-material.test.ts

@@ -27,7 +27,7 @@ describe('③ 공통 설정: fck · fy 입력 (spec §6.2)', () => {
   });
 
   it('a non-default material drops the I02 warning', () => {
-    const codes = rebarSummary(model, { ...DEFAULT_MATERIAL, fyS: 600 }).warnings.map((w) => w.code);
+    const codes = rebarSummary(model, { ...DEFAULT_MATERIAL, fck: 35 }).warnings.map((w) => w.code);
     expect(codes).not.toContain('I02');
   });
 });

tests/rebar-member-fck.test.ts

@@ -23,7 +23,7 @@ describe('② 부재별 fck (spec §6.2 · ②)', () => {
     const common = { ...DEFAULT_MATERIAL, fck: 30 };
     expect(materialFor(common, { coping: 35 }, 'coping').fck).toBe(35);
     expect(materialFor(common, { coping: 35 }, 'column').fck).toBe(30);
-    expect(materialFor(common, { coping: 35 }, 'coping').fyS).toBe(common.fyS);
+    expect(materialFor(common, { coping: 35 }, 'coping').grade).toEqual(common.grade);
   });
 
   it('a coping fck changes only the coping rows (C15 stair legs use the H19 development length)', () => {