BIM Clash Detection

Business Case

Problem Statement

Coordination issues cause significant rework:

• MEP vs structural conflicts discovered on site
• Late design changes increase costs
• Manual clash review is time-consuming
• No standardized clash categorization

Solution

Automated clash detection and analysis system that identifies conflicts between building systems and provides prioritized resolution recommendations.

Business Value

• Cost savings - Detect issues before construction
• Time reduction - Automated clash identification
• Better coordination - Systematic conflict resolution
• Quality improvement - Fewer field issues

Technical Implementation

import pandas as pd
from datetime import datetime
from typing import Dict, Any, List, Optional, Tuple
from dataclasses import dataclass, field
from enum import Enum
import math


class ClashType(Enum):
    """Types of clashes."""
    HARD = "hard"           # Physical intersection
    SOFT = "soft"           # Clearance violation
    WORKFLOW = "workflow"   # Sequencing conflict
    DUPLICATE = "duplicate" # Duplicated elements


class ClashStatus(Enum):
    """Clash resolution status."""
    NEW = "new"
    ACTIVE = "active"
    RESOLVED = "resolved"
    APPROVED = "approved"
    IGNORED = "ignored"


class ClashSeverity(Enum):
    """Clash severity level."""
    CRITICAL = "critical"
    MAJOR = "major"
    MINOR = "minor"
    INFO = "info"


class Discipline(Enum):
    """BIM disciplines."""
    ARCHITECTURAL = "architectural"
    STRUCTURAL = "structural"
    MECHANICAL = "mechanical"
    ELECTRICAL = "electrical"
    PLUMBING = "plumbing"
    FIRE_PROTECTION = "fire_protection"
    CIVIL = "civil"


@dataclass
class BoundingBox:
    """3D bounding box."""
    min_x: float
    min_y: float
    min_z: float
    max_x: float
    max_y: float
    max_z: float

    def intersects(self, other: 'BoundingBox') -> bool:
        """Check if boxes intersect."""
        return (self.min_x <= other.max_x and self.max_x >= other.min_x and
                self.min_y <= other.max_y and self.max_y >= other.min_y and
                self.min_z <= other.max_z and self.max_z >= other.min_z)

    def volume(self) -> float:
        """Calculate bounding box volume."""
        return ((self.max_x - self.min_x) *
                (self.max_y - self.min_y) *
                (self.max_z - self.min_z))

    def center(self) -> Tuple[float, float, float]:
        """Get center point."""
        return (
            (self.min_x + self.max_x) / 2,
            (self.min_y + self.max_y) / 2,
            (self.min_z + self.max_z) / 2
        )


@dataclass
class BIMElement:
    """BIM element representation."""
    element_id: str
    name: str
    discipline: Discipline
    category: str  # e.g., "Duct", "Beam", "Pipe"
    level: str
    bounding_box: BoundingBox
    properties: Dict[str, Any] = field(default_factory=dict)

    def distance_to(self, other: 'BIMElement') -> float:
        """Calculate distance between element centers."""
        c1 = self.bounding_box.center()
        c2 = other.bounding_box.center()
        return math.sqrt(
            (c2[0] - c1[0])**2 +
            (c2[1] - c1[1])**2 +
            (c2[2] - c1[2])**2
        )


@dataclass
class Clash:
    """Clash between two elements."""
    clash_id: str
    element_a: BIMElement
    element_b: BIMElement
    clash_type: ClashType
    severity: ClashSeverity
    status: ClashStatus
    distance: float  # Penetration depth (negative) or clearance gap
    location: Tuple[float, float, float]
    detected_at: datetime
    resolved_at: Optional[datetime] = None
    assigned_to: Optional[str] = None
    notes: str = ""

    def to_dict(self) -> Dict[str, Any]:
        return {
            'clash_id': self.clash_id,
            'element_a_id': self.element_a.element_id,
            'element_a_name': self.element_a.name,
            'element_a_discipline': self.element_a.discipline.value,
            'element_b_id': self.element_b.element_id,
            'element_b_name': self.element_b.name,
            'element_b_discipline': self.element_b.discipline.value,
            'clash_type': self.clash_type.value,
            'severity': self.severity.value,
            'status': self.status.value,
            'distance': round(self.distance, 3),
            'location_x': self.location[0],
            'location_y': self.location[1],
            'location_z': self.location[2],
            'level': self.element_a.level,
            'detected_at': self.detected_at.isoformat(),
            'assigned_to': self.assigned_to,
            'notes': self.notes
        }


@dataclass
class ClashTest:
    """Clash test configuration."""
    name: str
    discipline_a: Discipline
    discipline_b: Discipline
    clash_type: ClashType
    tolerance: float = 0.0  # Clearance tolerance in meters
    enabled: bool = True


class BIMClashDetector:
    """Detect and manage BIM clashes."""

    def __init__(self):
        self.elements: List[BIMElement] = []
        self.clashes: List[Clash] = []
        self.clash_tests: List[ClashTest] = []
        self._clash_counter = 0

    def load_elements(self, elements_df: pd.DataFrame) -> int:
        """Load BIM elements from DataFrame."""
        loaded = 0
        for _, row in elements_df.iterrows():
            element = BIMElement(
                element_id=str(row.get('element_id', '')),
                name=str(row.get('name', '')),
                discipline=Discipline(row.get('discipline', 'architectural')),
                category=str(row.get('category', '')),
                level=str(row.get('level', '')),
                bounding_box=BoundingBox(
                    min_x=float(row.get('min_x', 0)),
                    min_y=float(row.get('min_y', 0)),
                    min_z=float(row.get('min_z', 0)),
                    max_x=float(row.get('max_x', 0)),
                    max_y=float(row.get('max_y', 0)),
                    max_z=float(row.get('max_z', 0))
                )
            )
            self.elements.append(element)
            loaded += 1
        return loaded

    def add_clash_test(self, test: ClashTest):
        """Add clash test configuration."""
        self.clash_tests.append(test)

    def setup_standard_tests(self):
        """Setup standard MEP coordination tests."""
        standard_tests = [
            ClashTest("MEP vs Structure", Discipline.MECHANICAL, Discipline.STRUCTURAL, ClashType.HARD),
            ClashTest("Electrical vs Structure", Discipline.ELECTRICAL, Discipline.STRUCTURAL, ClashType.HARD),
            ClashTest("Plumbing vs Structure", Discipline.PLUMBING, Discipline.STRUCTURAL, ClashType.HARD),
            ClashTest("MEP vs MEP", Discipline.MECHANICAL, Discipline.ELECTRICAL, ClashType.HARD),
            ClashTest("Duct Clearance", Discipline.MECHANICAL, Discipline.MECHANICAL, ClashType.SOFT, tolerance=0.05),
            ClashTest("Fire Protection", Discipline.FIRE_PROTECTION, Discipline.STRUCTURAL, ClashType.HARD),
        ]
        for test in standard_tests:
            self.add_clash_test(test)

    def run_clash_detection(self) -> List[Clash]:
        """Run all clash tests."""
        new_clashes = []

        for test in self.clash_tests:
            if not test.enabled:
                continue

            # Filter elements by discipline
            elements_a = [e for e in self.elements if e.discipline == test.discipline_a]
            elements_b = [e for e in self.elements if e.discipline == test.discipline_b]

            # Check all pairs
            for elem_a in elements_a:
                for elem_b in elements_b:
                    if elem_a.element_id == elem_b.element_id:
                        continue

                    clash = self._check_clash(elem_a, elem_b, test)
                    if clash:
                        new_clashes.append(clash)

        self.clashes.extend(new_clashes)
        return new_clashes

    def _check_clash(self, elem_a: BIMElement, elem_b: BIMElement,
                     test: ClashTest) -> Optional[Clash]:
        """Check if two elements clash."""

        # Expand bounding box by tolerance for soft clashes
        box_a = elem_a.bounding_box
        box_b = elem_b.bounding_box

        if test.clash_type == ClashType.SOFT:
            # Add clearance tolerance
            expanded_a = BoundingBox(
                box_a.min_x - test.tolerance, box_a.min_y - test.tolerance, box_a.min_z - test.tolerance,
                box_a.max_x + test.tolerance, box_a.max_y + test.tolerance, box_a.max_z + test.tolerance
            )
            intersects = expanded_a.intersects(box_b)
        else:
            intersects = box_a.intersects(box_b)

        if not intersects:
            return None

        # Calculate clash point and severity
        self._clash_counter += 1
        clash_id = f"CLH-{self._clash_counter:05d}"

        # Clash location (center of intersection)
        location = (
            (max(box_a.min_x, box_b.min_x) + min(box_a.max_x, box_b.max_x)) / 2,
            (max(box_a.min_y, box_b.min_y) + min(box_a.max_y, box_b.max_y)) / 2,
            (max(box_a.min_z, box_b.min_z) + min(box_a.max_z, box_b.max_z)) / 2
        )

        # Calculate penetration depth
        distance = elem_a.distance_to(elem_b)

        # Determine severity
        if test.clash_type == ClashType.HARD:
            severity = ClashSeverity.CRITICAL if distance < 0.1 else ClashSeverity.MAJOR
        else:
            severity = ClashSeverity.MINOR if distance > test.tolerance else ClashSeverity.MAJOR

        return Clash(
            clash_id=clash_id,
            element_a=elem_a,
            element_b=elem_b,
            clash_type=test.clash_type,
            severity=severity,
            status=ClashStatus.NEW,
            distance=distance,
            location=location,
            detected_at=datetime.now()
        )

    def get_summary(self) -> Dict[str, Any]:
        """Get clash detection summary."""
        by_severity = {}
        by_discipline = {}
        by_status = {}

        for clash in self.clashes:
            # By severity
            sev = clash.severity.value
            by_severity[sev] = by_severity.get(sev, 0) + 1

            # By discipline pair
            pair = f"{clash.element_a.discipline.value} vs {clash.element_b.discipline.value}"
            by_discipline[pair] = by_discipline.get(pair, 0) + 1

            # By status
            stat = clash.status.value
            by_status[stat] = by_status.get(stat, 0) + 1

        return {
            'total_clashes': len(self.clashes),
            'by_severity': by_severity,
            'by_discipline': by_discipline,
            'by_status': by_status,
            'elements_checked': len(self.elements),
            'tests_run': len([t for t in self.clash_tests if t.enabled])
        }

    def export_to_dataframe(self) -> pd.DataFrame:
        """Export clashes to DataFrame."""
        return pd.DataFrame([c.to_dict() for c in self.clashes])

    def resolve_clash(self, clash_id: str, resolution_note: str):
        """Mark clash as resolved."""
        for clash in self.clashes:
            if clash.clash_id == clash_id:
                clash.status = ClashStatus.RESOLVED
                clash.resolved_at = datetime.now()
                clash.notes = resolution_note
                break

    def assign_clash(self, clash_id: str, assignee: str):
        """Assign clash to team member."""
        for clash in self.clashes:
            if clash.clash_id == clash_id:
                clash.assigned_to = assignee
                clash.status = ClashStatus.ACTIVE
                break

Quick Start

# Initialize detector
detector = BIMClashDetector()

# Setup standard MEP tests
detector.setup_standard_tests()

# Load elements from DataFrame
elements_df = pd.read_excel("bim_elements.xlsx")
detector.load_elements(elements_df)

# Run detection
clashes = detector.run_clash_detection()
print(f"Found {len(clashes)} clashes")

# Get summary
summary = detector.get_summary()
print(f"Critical: {summary['by_severity'].get('critical', 0)}")

Common Use Cases

1. MEP Coordination

# Focus on MEP vs Structure
mep_clashes = [c for c in detector.clashes
               if c.element_a.discipline in [Discipline.MECHANICAL, Discipline.ELECTRICAL]]

2. Export for Review

df = detector.export_to_dataframe()
df.to_excel("clash_report.xlsx", index=False)

3. Assign to Teams

for clash in detector.clashes:
    if clash.element_a.discipline == Discipline.MECHANICAL:
        detector.assign_clash(clash.clash_id, "MEP Team")

Resources

• DDC Book: Chapter 2.4 - BIM Coordination
• Reference: ISO 19650 BIM Standards