Study guide
5.2 Strength and Service Load Combinations
PE Civil: Structural Exam
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1 Exam Identity and Reference Workflow
2026 PE Civil: Structural Identity, Format, and Scoring Electronic Handbook, Design Standards, Units, and Version Control
2 Chapter 2: Gravity and Construction Loads
2.1 Dead Loads and Self-Weight 2.2 Live Loads, Reduction, and Load Placement 2.3 Construction-Stage Loads
3 Environmental Loads
Wind Loads and Pressure Paths Seismic Loads and Lateral Force Distribution Snow, Rain, and Ice Loads
4 Moving, Impact, and Lateral Soil Loads
Vehicular, Crane, and Other Moving Loads Impact and Dynamic Allowances Earth Pressure and Surcharge Loads
5 Chapter 5: Load Paths and Combinations
5.1 Tributary Areas and Complete Vertical/Lateral Load Paths 5.2 Strength and Service Load Combinations
6 Reactions, Diagrams, and Basic Axial Effects
Free-Body Diagrams, Reactions, Shear, and Moment Qualitative Diagrams, Influence Lines, and Critical Placement Axial Tension, Compression, and Deformation
7 Chapter 7: Axial Systems and Shear Effects
7.1 Trusses, Braces, and Column Axial Force 7.2 Shear Stress, Shear Flow, and Built-Up Sections 7.3 One-Way, Two-Way, Punching, and Interface Shear Effects
8 Flexure
Section Properties and Elastic Flexural Stress Beam and Slab Flexural Load Effects Biaxial and Unsymmetrical Flexure
9 Combined Stress and Deflection
Combined Axial and Flexural Stress Principal Stress, Mohr's Circle, and Combined Shear Elastic Deflection Methods
10 Chapter 10: Serviceability, Torsion, and Stability
10.1 Serviceability: Deflection, Drift, Vibration, and Ponding 10.2 Torsion and Warping Effects 10.3 Buckling, Effective Length, and Second-Order Stability
11 Fatigue, Robustness, Thermal, and Bearing Effects
Fatigue and Progressive-Collapse Concepts Thermal Deformation and Bearing/Contact Stress
12 Inspections, Submittals, and Adjacent Facilities
Special Inspections and Verification Duties Shop Drawings, Submittals, RFIs, and Delegated Design Construction Effects on Adjacent Facilities
13 Chapter 13: Temporary Works and Safety
13.1 Formwork, Falsework, Scaffolding, Shoring/Reshoring, Bracing, and Anchorage 13.2 Construction, Roadside, and Work-Zone Safety
14 Soils and Core Concrete Properties
Soil Phase Relationships and Classification Soil Strength, Permeability, and Compressibility Fresh and Hardened Concrete Properties
15 Chapter 15: Prestressed Concrete and Steel Properties
15.1 Reinforced, Precast, Pretensioned, and Post-Tensioned Concrete Materials 15.2 Structural and Cold-Formed Steel Properties 15.3 Steel Toughness, Weldability, Corrosion, and Temperature Effects
16 Timber, Masonry, and Material Conformance
Timber Properties and ASD Design Values Masonry, CMU, Mortar, Grout, and Brick Veneer Properties Concrete and Masonry Test Methods Steel, Timber, and Other Material Specification Conformance
17 Horizontal Members I
Steel Beams and Girders Reinforced Concrete Beams and Slabs Timber and Masonry Horizontal Members
18 Chapter 18: Diaphragms and Vertical Members
18.1 Diaphragms, Collectors, Struts, and Composite Slabs 18.2 Steel Columns and Beam-Columns 18.3 Concrete Columns and Bearing Walls
19 Shear Walls, Trusses, and Frames
Shear Walls and Vertical Lateral Members Trusses and Braced Systems Moment Frames and Stability Systems
20 Composite/Bridge Systems and Bolted Connections
Composite Construction and Structural System Selection Bridge Systems and Load Distribution Bolted Steel Connections
21 Chapter 21: Welded, Embedded, and Anchored Connections
21.1 Welded Steel Connections 21.2 Bearing, Embedded, and Precast Connections 21.3 Anchors, Post-Installed Anchors, and Wood/Masonry Connections
22 Shallow Foundations
Isolated, Spread, and Strip Footings Combined and Strap Footings Mat Foundations and Foundation Slabs
23 Deep Foundations
Driven Piles: Axial Capacity and Settlement Drilled Shafts, Piers, and Caissons Pile Groups, Caps, and Lateral Deep-Foundation Response
24 Chapter 24: Retaining Structures
24.1 Lateral Earth/Water Pressure and Drainage 24.2 Sliding, Overturning, Bearing, and Global Stability 24.3 Concrete Cantilever, Gravity, and Basement Walls 24.4 Sheet-Pile, Anchored, and Mechanically Stabilized Earth Walls
5.2 Strength and Service Load Combinations
Key Takeaways Explain This Topic AI
Nominal loads are classified before combination; a load factor changes design demand but does not change a live load into dead load or wind into seismic load.
Building strength/LRFD demand must be compared with strength resistance, while ASD demand must be compared with allowable resistance from the same material-design route.
Serviceability combinations evaluate behavior such as deflection and drift and are not automatically identical to either a strength combination or every ASD capacity check.
AASHTO LRFD bridge limit states form a separate combination family from ASCE 7-16/IBC 2018 building combinations.
An envelope evaluates required concurrency, signs, directions, and load patterns; it does not simply add the largest value of every possible load.
For the 2026 exam, wood design uses the NDS 2018 ASD route only.
Last updated: July 2026
Load combinations model which actions can occur together and how uncertainty is treated. They are not interchangeable lists of coefficients. For a July 2026 PE Civil: Structural problem, use the April 2024 specification and its listed editions: ASCE 7-16 with IBC 2018 for building load combinations, AASHTO LRFD 8th edition with the listed errata for bridges, ACI 318-14 for concrete resistance, the AISC Steel Construction Manual 15th edition for steel, and NDS 2018/SDPWS 2015 using ASD only for wood. Do not import the April 2027 editions.
Classify Nominal Loads Before Combining
Record each nominal action with its symbol and sign: permanent dead load D ; floor live load L ; roof live load Lr ; snow S ; rain R ; wind W ; earthquake effect E ; and other actions such as fluid, earth pressure, or temperature when applicable. The governing source defines the symbol and exceptions. Keep vertical and lateral effects separate until the chosen combination directs concurrency.
A sound workflow is:
Identify whether the structure is a building or bridge and open that code family's combination provisions.
List nominal load cases, including opposite wind or seismic directions, patterned live load, and stabilizing versus destabilizing dead load.
Select the required design route: strength/LRFD, ASD, or a stated serviceability check.
Generate every applicable combination from the exact exam reference; do not reconstruct factors from memory.
Analyze each case with its signs and placement, then envelope the requested response.
Compare demand with resistance or a service limit using compatible methods.
Label the governing combination and route in the answer.
Three Building Workflows That Must Stay Distinct
Strength or LRFD. ASCE 7-16 strength combinations use factored loads; familiar cases include 1.4D and 1.2D + 1.6L + 0.5(Lr or S or R) , subject to the complete provisions and exceptions. Material resistance is also reduced or otherwise formatted for strength. Concrete commonly checks U ≤ φR_n under ACI 318-14. Steel LRFD checks R_u ≤ φR_n under AISC 15th. A factored demand cannot be compared with a raw nominal resistance unless the governing equation explicitly formats it that way.
Allowable stress design. The ASCE 7-16/IBC 2018 ASD combinations use a different factor set and concurrency logic. Wind and earthquake coefficients in this family visibly differ from their strength counterparts, and stabilizing dead load can be reduced for uplift or overturning cases. AISC ASD checks R_a ≤ R_n/Ω . For this NCEES specification, NDS wood design is ASD only , so use the building ASD combinations and NDS adjusted allowable capacities; do not invent a wood LRFD solution because another material permits LRFD.
Serviceability. Deflection, drift, vibration, crack control, or settlement may use nominal-load combinations and stiffness assumptions specified by the applicable standard or problem. “Service” describes performance under use, not a universal coefficient list. A service deflection demand is compared with a deflection limit, not with φR_n ; an ASD strength check is not automatically the project's serviceability check merely because its loads are less amplified than a strength case.
IBC 2018 and ASCE 7-16 building provisions are coordinated, but follow the route and exceptions that the problem identifies. Do not splice one line from each as if they were independent factor menus.
Worked Compatibility Example
A steel column has nominal axial effects P_D = 35 kips and P_L = 22 kips . The problem directs evaluation of the building strength case 1.2D + 1.6L and the ASD case D + L . It gives nominal compressive resistance P_n = 120 kips , LRFD factor φ = 0.90 , and ASD factor Ω = 1.67 .
- LRFD route
- P_u = 1.2(35) + 1.6(22) = 77.2 kips
- φP_n = 0.90(120) = 108 kips
77.2/108 = 0.715 , so the stated LRFD check passes.
- ASD route
- P_a = 35 + 22 = 57.0 kips
- P_n/Ω = 120/1.67 = 71.9 kips
57.0/71.9 = 0.793 , so the stated ASD check also passes.
These are two complete, valid comparisons. Comparing P_u with P_n/Ω mixes LRFD demand with ASD resistance; comparing P_a with φP_n mixes ASD demand with LRFD resistance. Neither mixed ratio has design meaning, even if its numerical result looks favorable. The example factors are given so the lesson is compatibility, not memorization; actual problems require all applicable combinations, stability provisions, and resistance adjustments.
Concurrency, Direction, and Envelopes
Environmental loads are transient and directional. A combination specifies when companion live, roof, snow, or rain effects appear and at what factors. It may require both signs of wind or seismic response. Reduced dead load can govern uplift because gravity is stabilizing, while larger dead load may govern downward force. Patterned live load can govern a continuous-member moment even when full live load governs total reaction. Generate cases first, then take the maximum positive, maximum negative, or largest absolute response requested. Do not add maxima from different mutually exclusive cases.
Bridges Are a Separate Code Family
AASHTO LRFD organizes bridge actions into named limit states such as Strength, Service, Extreme Event, and Fatigue, with its own load factors, modifiers, multiple-presence rules, and dynamic allowances. Select the AASHTO limit state and resistance provisions together. An ASCE 7 building wind factor or AISC building combination does not replace an AASHTO bridge combination, even when the member material is steel or concrete. Material mechanics may look familiar, but the demand and resistance framework remains the one prescribed for the bridge.
Before selecting an answer, label it building strength , building ASD , serviceability , or AASHTO LRFD ; confirm that demand, resistance, code family, and units all match.