Scenario Planner for Construction
Overview
Model different project scenarios to understand their impacts on cost, schedule, and resources. Compare alternatives, optimize decisions, and prepare for contingencies.
Business Case
Construction decisions require understanding trade-offs:
- Design Alternatives: Which option is most cost-effective?
- Schedule Compression: What's the cost of accelerating?
- Resource Options: In-house vs. subcontractor?
- Risk Scenarios: What if materials increase 20%?
Technical Implementation
from dataclasses import dataclass, field
from typing import List, Dict, Any, Optional, Callable
from datetime import datetime, timedelta
import pandas as pd
import numpy as np
from copy import deepcopy
@dataclass
class ScenarioParameter:
name: str
base_value: float
unit: str
min_value: Optional[float] = None
max_value: Optional[float] = None
description: str = ""
@dataclass
class Scenario:
id: str
name: str
description: str
parameters: Dict[str, float]
created_at: datetime = field(default_factory=datetime.now)
@dataclass
class ScenarioResult:
scenario_id: str
scenario_name: str
total_cost: float
total_duration: int # days
resource_requirements: Dict[str, float]
risk_score: float
key_metrics: Dict[str, float]
warnings: List[str]
comparison_to_base: Dict[str, float]
@dataclass
class SensitivityResult:
parameter: str
values_tested: List[float]
cost_impacts: List[float]
duration_impacts: List[float]
sensitivity_score: float
class ConstructionScenarioPlanner:
"""Scenario planning and what-if analysis for construction."""
def __init__(self, base_project: Dict):
self.base_project = base_project
self.parameters: Dict[str, ScenarioParameter] = {}
self.scenarios: Dict[str, Scenario] = {}
self.results: Dict[str, ScenarioResult] = {}
self.cost_model: Optional[Callable] = None
self.duration_model: Optional[Callable] = None
self._setup_default_parameters()
def _setup_default_parameters(self):
"""Setup common construction scenario parameters."""
default_params = [
ScenarioParameter("labor_rate", 75, "$/hr", 50, 150, "Average labor rate"),
ScenarioParameter("material_escalation", 0, "%", -10, 30, "Material cost change"),
ScenarioParameter("productivity_factor", 1.0, "x", 0.5, 1.5, "Labor productivity multiplier"),
ScenarioParameter("overtime_percentage", 0, "%", 0, 50, "Overtime work percentage"),
ScenarioParameter("crew_size", 10, "workers", 5, 50, "Average crew size"),
ScenarioParameter("work_days_per_week", 5, "days", 5, 7, "Working days per week"),
ScenarioParameter("contingency_percentage", 10, "%", 5, 25, "Cost contingency"),
ScenarioParameter("weather_delay_days", 0, "days", 0, 60, "Expected weather delays"),
ScenarioParameter("permit_delay_days", 0, "days", 0, 90, "Expected permit delays"),
ScenarioParameter("subcontractor_markup", 15, "%", 10, 30, "Subcontractor markup"),
]
for param in default_params:
self.parameters[param.name] = param
def add_parameter(self, param: ScenarioParameter):
"""Add custom parameter."""
self.parameters[param.name] = param
def set_cost_model(self, model: Callable):
"""Set custom cost calculation model."""
self.cost_model = model
def set_duration_model(self, model: Callable):
"""Set custom duration calculation model."""
self.duration_model = model
def create_scenario(self, name: str, description: str,
parameter_changes: Dict[str, float]) -> Scenario:
"""Create a new scenario with parameter modifications."""
# Start with base values
params = {p.name: p.base_value for p in self.parameters.values()}
# Apply changes
for param_name, value in parameter_changes.items():
if param_name in params:
params[param_name] = value
else:
raise ValueError(f"Unknown parameter: {param_name}")
scenario = Scenario(
id=f"SCN-{len(self.scenarios) + 1:03d}",
name=name,
description=description,
parameters=params
)
self.scenarios[scenario.id] = scenario
return scenario
def calculate_cost(self, params: Dict[str, float]) -> float:
"""Calculate total project cost based on parameters."""
if self.cost_model:
return self.cost_model(self.base_project, params)
# Default cost model
base_cost = self.base_project.get('base_cost', 1000000)
# Labor adjustments
labor_factor = params['labor_rate'] / 75 # Normalized to base rate
productivity_impact = 1 / params['productivity_factor']
overtime_premium = 1 + (params['overtime_percentage'] / 100 * 0.5)
labor_cost = base_cost * 0.4 * labor_factor * productivity_impact * overtime_premium
# Material adjustments
material_cost = base_cost * 0.35 * (1 + params['material_escalation'] / 100)
# Equipment and other
equipment_cost = base_cost * 0.15
# Subcontractor
sub_cost = base_cost * 0.1 * (1 + params['subcontractor_markup'] / 100)
subtotal = labor_cost + material_cost + equipment_cost + sub_cost
# Contingency
total = subtotal * (1 + params['contingency_percentage'] / 100)
return total
def calculate_duration(self, params: Dict[str, float]) -> int:
"""Calculate project duration based on parameters."""
if self.duration_model:
return self.duration_model(self.base_project, params)
# Default duration model
base_duration = self.base_project.get('base_duration', 365)
# Crew size impact
crew_factor = 10 / params['crew_size'] # Inverse relationship
# Productivity impact
productivity_factor = 1 / params['productivity_factor']
# Work days impact
workday_factor = 5 / params['work_days_per_week']
# Overtime compression
overtime_compression = 1 - (params['overtime_percentage'] / 100 * 0.3)
calculated_duration = base_duration * crew_factor * productivity_factor * workday_factor * overtime_compression
# Add delays
delays = params['weather_delay_days'] + params['permit_delay_days']
return int(calculated_duration + delays)
def evaluate_scenario(self, scenario: Scenario) -> ScenarioResult:
"""Evaluate a scenario and calculate results."""
params = scenario.parameters
total_cost = self.calculate_cost(params)
total_duration = self.calculate_duration(params)
# Calculate resource requirements
resources = {
'labor_hours': total_duration * params['crew_size'] * 8 * (params['work_days_per_week'] / 5),
'peak_workers': params['crew_size'] * (1 + params['overtime_percentage'] / 100 * 0.5),
'overtime_hours': total_duration * params['crew_size'] * 8 * params['overtime_percentage'] / 100,
}
# Calculate risk score (0-100)
risk_factors = [
params['overtime_percentage'] / 50 * 20, # High overtime = higher risk
(1 - params['productivity_factor']) * 20 if params['productivity_factor'] < 1 else 0,
params['material_escalation'] / 30 * 15 if params['material_escalation'] > 0 else 0,
(25 - params['contingency_percentage']) / 20 * 15, # Low contingency = higher risk
]
risk_score = min(sum(risk_factors), 100)
# Key metrics
cost_per_day = total_cost / total_duration
cost_per_sf = total_cost / self.base_project.get('gross_area', 50000)
key_metrics = {
'cost_per_day': cost_per_day,
'cost_per_sf': cost_per_sf,
'labor_productivity': resources['labor_hours'] / total_duration,
}
# Warnings
warnings = []
if params['overtime_percentage'] > 30:
warnings.append("High overtime may cause burnout and quality issues")
if params['contingency_percentage'] < 8:
warnings.append("Low contingency increases risk of budget overrun")
if params['productivity_factor'] < 0.8:
warnings.append("Low productivity factor may not be sustainable")
# Compare to base scenario
base_params = {p.name: p.base_value for p in self.parameters.values()}
base_cost = self.calculate_cost(base_params)
base_duration = self.calculate_duration(base_params)
comparison = {
'cost_change_pct': ((total_cost - base_cost) / base_cost) * 100,
'cost_change_abs': total_cost - base_cost,
'duration_change_pct': ((total_duration - base_duration) / base_duration) * 100,
'duration_change_days': total_duration - base_duration,
}
result = ScenarioResult(
scenario_id=scenario.id,
scenario_name=scenario.name,
total_cost=total_cost,
total_duration=total_duration,
resource_requirements=resources,
risk_score=risk_score,
key_metrics=key_metrics,
warnings=warnings,
comparison_to_base=comparison
)
self.results[scenario.id] = result
return result
def run_sensitivity_analysis(self, parameter: str,
values: List[float] = None,
steps: int = 10) -> SensitivityResult:
"""Run sensitivity analysis on a single parameter."""
if parameter not in self.parameters:
raise ValueError(f"Unknown parameter: {parameter}")
param = self.parameters[parameter]
if values is None:
min_val = param.min_value or param.base_value * 0.5
max_val = param.max_value or param.base_value * 1.5
values = np.linspace(min_val, max_val, steps).tolist()
base_params = {p.name: p.base_value for p in self.parameters.values()}
base_cost = self.calculate_cost(base_params)
base_duration = self.calculate_duration(base_params)
cost_impacts = []
duration_impacts = []
for val in values:
test_params = base_params.copy()
test_params[parameter] = val
cost = self.calculate_cost(test_params)
duration = self.calculate_duration(test_params)
cost_impacts.append(((cost - base_cost) / base_cost) * 100)
duration_impacts.append(((duration - base_duration) / base_duration) * 100)
# Calculate sensitivity score (range of impact)
cost_range = max(cost_impacts) - min(cost_impacts)
duration_range = max(duration_impacts) - min(duration_impacts)
sensitivity_score = (cost_range + duration_range) / 2
return SensitivityResult(
parameter=parameter,
values_tested=values,
cost_impacts=cost_impacts,
duration_impacts=duration_impacts,
sensitivity_score=sensitivity_score
)
def compare_scenarios(self, scenario_ids: List[str] = None) -> pd.DataFrame:
"""Compare multiple scenarios side by side."""
if scenario_ids is None:
scenario_ids = list(self.scenarios.keys())
data = []
for sid in scenario_ids:
if sid not in self.results:
scenario = self.scenarios[sid]
self.evaluate_scenario(scenario)
result = self.results[sid]
data.append({
'Scenario': result.scenario_name,
'Total Cost': f"${result.total_cost:,.0f}",
'Duration (days)': result.total_duration,
'Cost Change': f"{result.comparison_to_base['cost_change_pct']:+.1f}%",
'Duration Change': f"{result.comparison_to_base['duration_change_days']:+.0f} days",
'Risk Score': f"{result.risk_score:.0f}/100",
'Cost/SF': f"${result.key_metrics['cost_per_sf']:.2f}",
})
return pd.DataFrame(data)
def find_optimal_scenario(self, objective: str = 'cost',
constraints: Dict[str, tuple] = None) -> Scenario:
"""Find optimal scenario given objective and constraints."""
valid_results = []
for sid, result in self.results.items():
# Check constraints
if constraints:
meets_constraints = True
if 'max_cost' in constraints and result.total_cost > constraints['max_cost']:
meets_constraints = False
if 'max_duration' in constraints and result.total_duration > constraints['max_duration']:
meets_constraints = False
if 'max_risk' in constraints and result.risk_score > constraints['max_risk']:
meets_constraints = False
if not meets_constraints:
continue
valid_results.append((sid, result))
if not valid_results:
return None
# Sort by objective
if objective == 'cost':
valid_results.sort(key=lambda x: x[1].total_cost)
elif objective == 'duration':
valid_results.sort(key=lambda x: x[1].total_duration)
elif objective == 'risk':
valid_results.sort(key=lambda x: x[1].risk_score)
elif objective == 'balanced':
# Normalize and combine metrics
valid_results.sort(key=lambda x: (
x[1].total_cost / 1000000 +
x[1].total_duration / 365 +
x[1].risk_score / 100
))
return self.scenarios[valid_results[0][0]]
def generate_report(self) -> str:
"""Generate scenario comparison report."""
lines = ["# Scenario Analysis Report", ""]
lines.append(f"**Project:** {self.base_project.get('name', 'Project')}")
lines.append(f"**Generated:** {datetime.now().strftime('%Y-%m-%d %H:%M')}")
lines.append(f"**Scenarios Analyzed:** {len(self.scenarios)}")
lines.append("")
# Comparison table
lines.append("## Scenario Comparison")
comparison = self.compare_scenarios()
lines.append(comparison.to_markdown(index=False))
lines.append("")
# Best scenarios
lines.append("## Optimal Scenarios")
best_cost = self.find_optimal_scenario('cost')
if best_cost:
lines.append(f"- **Lowest Cost:** {best_cost.name}")
best_duration = self.find_optimal_scenario('duration')
if best_duration:
lines.append(f"- **Shortest Duration:** {best_duration.name}")
best_balanced = self.find_optimal_scenario('balanced')
if best_balanced:
lines.append(f"- **Best Balanced:** {best_balanced.name}")
lines.append("")
# Detailed results
lines.append("## Detailed Results")
for sid, result in self.results.items():
lines.append(f"\n### {result.scenario_name}")
lines.append(f"- **Cost:** ${result.total_cost:,.0f} ({result.comparison_to_base['cost_change_pct']:+.1f}%)")
lines.append(f"- **Duration:** {result.total_duration} days ({result.comparison_to_base['duration_change_days']:+.0f})")
lines.append(f"- **Risk Score:** {result.risk_score:.0f}/100")
if result.warnings:
lines.append("- **Warnings:**")
for w in result.warnings:
lines.append(f" - ⚠️ {w}")
return "\n".join(lines)Quick Start
# Define base project
base_project = {
'name': 'Office Building',
'base_cost': 5000000,
'base_duration': 365,
'gross_area': 50000
}
# Initialize planner
planner = ConstructionScenarioPlanner(base_project)
# Create scenarios
baseline = planner.create_scenario(
"Baseline",
"Standard approach with default parameters",
{}
)
accelerated = planner.create_scenario(
"Accelerated Schedule",
"Faster completion with overtime and larger crew",
{
'overtime_percentage': 25,
'crew_size': 15,
'work_days_per_week': 6
}
)
cost_optimized = planner.create_scenario(
"Cost Optimized",
"Lower cost with reduced contingency and smaller crew",
{
'contingency_percentage': 7,
'crew_size': 8,
'subcontractor_markup': 12
}
)
# Evaluate all scenarios
for scenario in planner.scenarios.values():
result = planner.evaluate_scenario(scenario)
print(f"{result.scenario_name}: ${result.total_cost:,.0f}, {result.total_duration} days")
# Compare scenarios
comparison = planner.compare_scenarios()
print(comparison)
# Run sensitivity analysis
sensitivity = planner.run_sensitivity_analysis('material_escalation')
print(f"Material escalation sensitivity: {sensitivity.sensitivity_score:.1f}")
# Generate report
report = planner.generate_report()
print(report)Dependencies
pip install pandas numpy