diff --git a/app/src/components/three/Piperack3D.tsx b/app/src/components/three/Piperack3D.tsx
index 1963f01..1a7c551 100644
--- a/app/src/components/three/Piperack3D.tsx
+++ b/app/src/components/three/Piperack3D.tsx
@@ -86,7 +86,9 @@ function PiperackModel({
     const zPos = numFrames > 1 
       ? -zOffset + 0.5 + (idx % Math.max(pipes.length, 1)) * (totalSpacing - 1) / Math.max(pipes.length - 1, 1) || 0
       : 0;
-    const yPos = elevation + height/2 + pipe.diameter/2 + (idx % 2 === 0 ? 0 : 0.2);
+    // elevationOffset varia de 0 (base da estrutura reticulada) a height (topo da estrutura)
+    // A base da estrutura fica em: rackTop - height, que é elevation - height/2
+    const yPos = (elevation - height/2) + pipe.elevationOffset + pipe.diameter/2;
     const color = pipeColors[idx % pipeColors.length];
 
     return (
diff --git a/app/src/lib/__tests__/audit-simulations.test.ts b/app/src/lib/__tests__/audit-simulations.test.ts
index d99b2f1..8222480 100644
--- a/app/src/lib/__tests__/audit-simulations.test.ts
+++ b/app/src/lib/__tests__/audit-simulations.test.ts
@@ -210,7 +210,7 @@ describe('Audit Simulations for NBR 6123:2023 Models', () => {
       spacing: 6,
       numFrames: 3,
       phiStruct: 0.2,
-      pipes: [{ id: 'p1', diameter: 1.0 }, { id: 'p2', diameter: 1.0 }], // total 2.0m de tubo num pórtico de 2.0m! 
+      pipes: [{ id: 'p1', diameter: 1.0, elevationOffset: 1.0 }, { id: 'p2', diameter: 1.0, elevationOffset: 1.5 }], // total 2.0m de tubo num pórtico de 2.0m! 
       q: 1,
     });
 
diff --git a/app/src/lib/modules/piperack.ts b/app/src/lib/modules/piperack.ts
index 282f20a..bc01702 100644
--- a/app/src/lib/modules/piperack.ts
+++ b/app/src/lib/modules/piperack.ts
@@ -4,6 +4,7 @@ import { linearInterp1D } from '../log-interp';
 export interface PipeDef {
   id: string;
   diameter: number; // diâmetro ou altura do equipamento em metros
+  elevationOffset: number; // posição Y relativa à base do reticulado (0 a h)
 }
 
 export interface PiperackInput {
@@ -24,6 +25,7 @@ export interface PiperackResult {
   linearLoadFront: number; // kN/m (carga no pórtico 1)
   linearLoadBack: number;  // kN/m (carga nos pórticos 2..n)
   globalForce: number;     // kN (força total na estrutura)
+  effectiveElevation: number; // z_eff: Altura efetiva de aplicação da força global (m)
 }
 
 /** Tabela de Ca genérica para reticulados planos (faces planas) baseada na solidez φ */
@@ -31,12 +33,22 @@ const PHI_ARRAY = [0.1, 0.2, 0.3, 0.4, 0.5, 0.6];
 const CA_FLAT_ARRAY = [2.8, 2.4, 2.0, 1.8, 1.7, 1.6];
 
 export function calculatePiperack(input: PiperackInput): PiperackResult {
-  const { width, height, spacing, numFrames, phiStruct, pipes, q } = input;
+  const { width, height, elevation, spacing, numFrames, phiStruct, pipes, q } = input;
+
+  // 1. Calcular o Índice de Solidez Total (φ) e Centro de Pressão Efetivo
+  let sumPhiZ = phiStruct * elevation; // Momento de área estática estrutural
+  const phiPipes = pipes.reduce((sum, pipe) => {
+    const phiP = pipe.diameter / height;
+    const pipeZ = (elevation - height / 2) + pipe.elevationOffset;
+    sumPhiZ += phiP * pipeZ;
+    return sum + phiP;
+  }, 0);
 
-  // 1. Calcular o Índice de Solidez Total (φ)
-  const phiPipes = pipes.reduce((sum, pipe) => sum + pipe.diameter / height, 0);
   const rawPhi = phiStruct + phiPipes;
   const phiTotal = Math.min(Math.max(rawPhi, 0.1), 1.0);
+  
+  // Z efetivo é a média ponderada pelas áreas de bloqueio (se rawPhi=0, usa elevation)
+  const effectiveElevation = rawPhi > 0 ? sumPhiZ / rawPhi : elevation;
 
   // 2. Coeficiente de Arrasto Frontal (Ca) para o primeiro pórtico
   let caFrontal = 1.6;
@@ -65,6 +77,7 @@ export function calculatePiperack(input: PiperackInput): PiperackResult {
     eta,
     linearLoadFront,
     linearLoadBack,
-    globalForce
+    globalForce,
+    effectiveElevation
   };
 }
diff --git a/app/src/pages/PiperackModule.tsx b/app/src/pages/PiperackModule.tsx
index a468c44..6103788 100644
--- a/app/src/pages/PiperackModule.tsx
+++ b/app/src/pages/PiperackModule.tsx
@@ -25,15 +25,15 @@ const PiperackModule: React.FC = () => {
   const [pipes, setPipes] = useState<PipeDef[]>([]);
 
   const addPipe = () => {
-    setPipes([...pipes, { id: Math.random().toString(36).substr(2, 9), diameter: 0.5 }]);
+    setPipes([...pipes, { id: Math.random().toString(36).substr(2, 9), diameter: 0.5, elevationOffset: height / 2 }]);
   };
 
   const removePipe = (id: string) => {
     setPipes(pipes.filter(p => p.id !== id));
   };
 
-  const updatePipe = (id: string, diam: number) => {
-    setPipes(pipes.map(p => p.id === id ? { ...p, diameter: diam } : p));
+  const updatePipe = (id: string, diam: number, yOffset: number) => {
+    setPipes(pipes.map(p => p.id === id ? { ...p, diameter: diam, elevationOffset: yOffset } : p));
   };
 
   const result = useMemo(() => {
@@ -80,7 +80,8 @@ const PiperackModule: React.FC = () => {
           { label: 'Carga Linear Pórtico Frontal', value: `${result.linearLoadFront.toFixed(2)} kN/m` },
           { label: 'Carga Linear Pórticos Traseiros (cada)', value: `${result.linearLoadBack.toFixed(2)} kN/m` },
           { label: 'Força Global Total', value: `${result.globalForce.toFixed(2)} kN` },
-          { label: 'Momento Total de Tombamento', value: `${(result.linearLoadFront * width * elevation + (numFrames > 1 ? (numFrames - 1) * result.linearLoadBack * width * elevation : 0)).toFixed(2)} kN·m` },
+          { label: 'Centro de Pressão Efetivo (Z_eff)', value: `${result.effectiveElevation.toFixed(2)} m` },
+          { label: 'Momento Total de Tombamento', value: `${(result.globalForce * result.effectiveElevation).toFixed(2)} kN·m` },
         ],
       }
     ];
@@ -182,22 +183,40 @@ const PiperackModule: React.FC = () => {
                 Nenhuma tubulação adicionada.
               </div>
             ) : (
-              <div className="space-y-2">
+              <div className="space-y-4">
                 {pipes.map((pipe, index) => (
-                  <div key={pipe.id} className="flex items-center gap-2 p-2 rounded-md border bg-muted/20">
-                    <label className="w-20 text-xs text-muted-foreground shrink-0">Tubo {index + 1}</label>
-                    <Input
-                      type="number"
-                      value={pipe.diameter}
-                      onChange={(e) => updatePipe(pipe.id, Number(e.target.value))}
-                      step={0.1}
-                      min={0.1}
-                      className="h-7 text-xs font-mono"
-                    />
-                    <span className="text-xs text-muted-foreground">m</span>
-                    <Button variant="ghost" size="icon" className="h-7 w-7 text-destructive shrink-0" onClick={() => removePipe(pipe.id)}>
-                      <Trash2 className="w-4 h-4" />
-                    </Button>
+                  <div key={pipe.id} className="flex flex-col gap-2 p-3 rounded-md border bg-muted/20">
+                    <div className="flex items-center justify-between">
+                      <label className="text-xs font-semibold text-foreground">Tubo {index + 1}</label>
+                      <Button variant="ghost" size="icon" className="h-6 w-6 text-destructive" onClick={() => removePipe(pipe.id)}>
+                        <Trash2 className="w-3 h-3" />
+                      </Button>
+                    </div>
+                    <div className="flex items-center gap-3">
+                      <div className="flex-1 space-y-1">
+                        <label className="text-[10px] text-muted-foreground uppercase tracking-wider">Diâmetro (m)</label>
+                        <Input
+                          type="number"
+                          value={pipe.diameter}
+                          onChange={(e) => updatePipe(pipe.id, Number(e.target.value), pipe.elevationOffset)}
+                          step={0.1}
+                          min={0.1}
+                          className="h-8 text-xs font-mono"
+                        />
+                      </div>
+                      <div className="flex-1 space-y-1">
+                        <label className="text-[10px] text-muted-foreground uppercase tracking-wider">Alt. Pórtico (0 a {height})</label>
+                        <Input
+                          type="number"
+                          value={pipe.elevationOffset}
+                          onChange={(e) => updatePipe(pipe.id, pipe.diameter, Number(e.target.value))}
+                          step={0.1}
+                          min={0}
+                          max={height}
+                          className="h-8 text-xs font-mono"
+                        />
+                      </div>
+                    </div>
                   </div>
                 ))}
               </div>
@@ -326,14 +345,35 @@ const PiperackModule: React.FC = () => {
                         return pipes.map((p, idx) => {
                            const cx = pipes.length === 1 ? (startX + endX)/2 : startX + idx * gap;
                            const r = Math.max(4, Math.min(15, p.diameter * 8)); // escala visual
-                           // y=25 para repousar sobre o suporte (y=35 para n=1) ou viga (y=40 para n>1)
-                           const cy = numFrames === 1 ? 35 - r : 40 - r; 
+                           // p.elevationOffset varia de 0 (base) a height (topo)
+                           // no SVG: Y cresce para baixo. y=110 (chão). Vigas y=40, y=65
+                           // Para não complicar a matemática com proporções da viga,
+                           // Mapeamos a elevação local para a região do pórtico no SVG (y=110 chão, base=110 - (elevation - height/2) - isso é dinâmico)
+                           // Vamos fazer simples: The drawn structural portico is roughly Y=35 (top) to Y=110 (bottom).
+                           // If n=1, structure top is Y=35.
+                           // Actually the pipe is attached to the column at a relative height.
+                           const localRatio = Math.max(0, Math.min(1, p.elevationOffset / height));
+                           // No desenho, a altura reticulada é desenhada num "y" aproximado entre Y=35 (topo) e Y=110 (base da coluna inteira).
+                           // Mas o pórtico real desenhado ali tem topo em 35 e altura 75. 
+                           // Então base do reticulado = 35 + 75 = 110. (Não, isso é pro solo).
+                           // Supondo que a altura h desenhada seja o topo da coluna Y=35 até uns 2/3 (Y=60),
+                           // Y invertido no SVG: base da seção = 65, topo = 35 (altura de 30 px).
+                           const svgTop = 35;
+                           const svgBottom = 65;
+                           const cy = svgBottom - localRatio * (svgBottom - svgTop) - r; 
+                           
                            return (
                              <circle key={p.id} cx={cx} cy={cy} r={r} fill="#3b82f6" fillOpacity="0.8" />
                            );
                         });
                       })()}
                       
+                      {/* Eixo indicativo de elevação Z_eff */}
+                      <g opacity="0.6">
+                        <line x1="20" y1={110 - Math.min(90, (result.effectiveElevation/elevation)*60)} x2="280" y2={110 - Math.min(90, (result.effectiveElevation/elevation)*60)} stroke="#f59e0b" strokeWidth="1" strokeDasharray="3 3" />
+                        <text x="25" y={110 - Math.min(90, (result.effectiveElevation/elevation)*60) - 3} fontSize="8" fill="#d97706" fontWeight="bold">Z_eff</text>
+                      </g>
+                      
                       <defs>
                         <marker id="arrowRight" markerWidth="6" markerHeight="6" refX="6" refY="3" orient="auto">
                           <path d="M0,0 L6,3 L0,6" fill="none" stroke="#10b981" strokeWidth="1.5" />
@@ -347,10 +387,11 @@ const PiperackModule: React.FC = () => {
                       <div className="space-y-1">
                         <div className="flex justify-between text-muted-foreground"><span>F. Frontal:</span> <span className="font-mono">{(result.linearLoadFront * width).toFixed(2)} kN</span></div>
                         {numFrames > 1 && <div className="flex justify-between text-muted-foreground"><span>F. Traseiros (Total):</span> <span className="font-mono">{((numFrames - 1) * result.linearLoadBack * width).toFixed(2)} kN</span></div>}
+                        <div className="flex justify-between text-primary font-medium mt-1"><span>Z efetivo (Z_eff):</span> <span className="font-mono">{result.effectiveElevation.toFixed(2)} m</span></div>
                       </div>
                       <div className="space-y-1">
                         <div className="flex justify-between text-primary font-medium"><span>Momento Global de Tombamento:</span></div>
-                        <div className="flex justify-end font-mono font-bold text-base">{(result.linearLoadFront * width * elevation + (numFrames > 1 ? (numFrames - 1) * result.linearLoadBack * width * elevation : 0)).toFixed(2)} kN·m</div>
+                        <div className="flex justify-end font-mono font-bold text-base">{(result.globalForce * result.effectiveElevation).toFixed(2)} kN·m</div>
                       </div>
                     </div>
                     <p className="text-[10px] text-muted-foreground leading-tight text-center">