ILLINOIS PROFESSIONAL ENGINEER (PE) EXAM PRACTICE QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A | INSTANT DOWNLOAD PDF
Core Domains
1. Structural Engineering (Loads, Analysis, Design)
2. Geotechnical Engineering (Soil Mechanics, Foundations, Retaining Structures)
3. Transportation Engineering (Highway Design, Traffic Flow, Pavement)
4. Water Resources and Environmental Engineering (Hydrology, Hydraulics, Water Quality)
5. Construction Engineering and Project Management
6. Engineering Economics and Risk Analysis
7. Professional Practice, Ethics, and Illinois Specific Regulations
8. Mechanical and Electrical Systems for Civil/Infrastructure Projects
9. Site Development and Stormwater Management
10. Materials Science (Concrete, Steel, Asphalt, Composites)
Introduction
,This comprehensive practice examination is designed to prepare candidates for the Illinois Professional Engineer
(PE) Exam. It assesses foundational engineering theory, applied professional knowledge, regulatory compliance,
ethics, and real-world decision-making. Questions are structured as multiple-choice and scenario-based items,
mirroring the complexity and depth of the actual exam. Emphasis is placed on practical application, engineering
judgment, and adherence to Illinois-specific codes and standards. Each question includes a verified correct answer
and a detailed rationale to reinforce learning. This resource supports systematic review and builds confidence for
exam success.
SECTION ONE: QUESTIONS 1–100
Question 1
A continuous steel beam is subjected to a uniformly distributed live load. According to AISC 360, which limit
state typically controls the design for flexure in a compact, laterally braced section?
A. Yielding of the tension flange
B. Lateral-torsional buckling
C. Local flange buckling
D. Shear yielding of the web
,🟢A
🔴 RATIONALE: For a compact, laterally braced section, the plastic moment can be reached. Yielding of the
tension flange (or compression flange yielding in a compact section) is the controlling limit state. Lateral-
torsional buckling (B) does not occur due to bracing; local buckling (C) is prevented by compactness; shear
yielding (D) is a different limit state addressed separately.
Question 2
A soil sample has a total unit weight of 120 lb/ft³ and a water content of 15%. The specific gravity of solids is
2.65. What is the dry unit weight?
A. 98.6 lb/ft³
B. 104.3 lb/ft³
C. 110.2 lb/ft³
D. 115.8 lb/ft³
🟢B
🔴 RATIONALE: Dry unit weight γ_d = γ / (1 + w) = 120 / (1 + 0.15) = 104.35 lb/ft³. This is a fundamental phase
relationship.
, Question 3
Under the Illinois Professional Engineering Practice Act, which activity is strictly prohibited for a licensed
Professional Engineer?
A. Sealing structural drawings prepared by a subordinate engineer under direct supervision
B. Offering expert testimony in a court case on a project they did not design
C. Practicing engineering in a discipline outside their direct experience without a co-signing PE
D. Delegating field inspections to an unlicensed graduate engineer supervised daily
🟢C
🔴 RATIONALE: Illinois law requires PEs to practice only in areas of their competence. Practicing in an unrelated
discipline without a qualified co-signer violates ethics and statute. Options A and D are permissible with proper
supervision; B is allowed if based on professional analysis.
Question 4
A stormwater detention basin with a volume of 5 acre-feet drains through a 12-inch diameter circular orifice.
Assuming free discharge, what is the approximate discharge at a head of 4 feet above the orifice center? (Cd =
0.60)
ANSWERS) PLUS RATIONALES 2026 Q&A | INSTANT DOWNLOAD PDF
Core Domains
1. Structural Engineering (Loads, Analysis, Design)
2. Geotechnical Engineering (Soil Mechanics, Foundations, Retaining Structures)
3. Transportation Engineering (Highway Design, Traffic Flow, Pavement)
4. Water Resources and Environmental Engineering (Hydrology, Hydraulics, Water Quality)
5. Construction Engineering and Project Management
6. Engineering Economics and Risk Analysis
7. Professional Practice, Ethics, and Illinois Specific Regulations
8. Mechanical and Electrical Systems for Civil/Infrastructure Projects
9. Site Development and Stormwater Management
10. Materials Science (Concrete, Steel, Asphalt, Composites)
Introduction
,This comprehensive practice examination is designed to prepare candidates for the Illinois Professional Engineer
(PE) Exam. It assesses foundational engineering theory, applied professional knowledge, regulatory compliance,
ethics, and real-world decision-making. Questions are structured as multiple-choice and scenario-based items,
mirroring the complexity and depth of the actual exam. Emphasis is placed on practical application, engineering
judgment, and adherence to Illinois-specific codes and standards. Each question includes a verified correct answer
and a detailed rationale to reinforce learning. This resource supports systematic review and builds confidence for
exam success.
SECTION ONE: QUESTIONS 1–100
Question 1
A continuous steel beam is subjected to a uniformly distributed live load. According to AISC 360, which limit
state typically controls the design for flexure in a compact, laterally braced section?
A. Yielding of the tension flange
B. Lateral-torsional buckling
C. Local flange buckling
D. Shear yielding of the web
,🟢A
🔴 RATIONALE: For a compact, laterally braced section, the plastic moment can be reached. Yielding of the
tension flange (or compression flange yielding in a compact section) is the controlling limit state. Lateral-
torsional buckling (B) does not occur due to bracing; local buckling (C) is prevented by compactness; shear
yielding (D) is a different limit state addressed separately.
Question 2
A soil sample has a total unit weight of 120 lb/ft³ and a water content of 15%. The specific gravity of solids is
2.65. What is the dry unit weight?
A. 98.6 lb/ft³
B. 104.3 lb/ft³
C. 110.2 lb/ft³
D. 115.8 lb/ft³
🟢B
🔴 RATIONALE: Dry unit weight γ_d = γ / (1 + w) = 120 / (1 + 0.15) = 104.35 lb/ft³. This is a fundamental phase
relationship.
, Question 3
Under the Illinois Professional Engineering Practice Act, which activity is strictly prohibited for a licensed
Professional Engineer?
A. Sealing structural drawings prepared by a subordinate engineer under direct supervision
B. Offering expert testimony in a court case on a project they did not design
C. Practicing engineering in a discipline outside their direct experience without a co-signing PE
D. Delegating field inspections to an unlicensed graduate engineer supervised daily
🟢C
🔴 RATIONALE: Illinois law requires PEs to practice only in areas of their competence. Practicing in an unrelated
discipline without a qualified co-signer violates ethics and statute. Options A and D are permissible with proper
supervision; B is allowed if based on professional analysis.
Question 4
A stormwater detention basin with a volume of 5 acre-feet drains through a 12-inch diameter circular orifice.
Assuming free discharge, what is the approximate discharge at a head of 4 feet above the orifice center? (Cd =
0.60)
