2.3 Construction-Stage Loads

A structure is not built in its final configuration. During construction, concrete is wet, steel may be unbraced, connections may be incomplete, precast units rely on temporary braces, and a lower floor may carry shores from work above. These temporary states can govern even when the completed building has ample capacity.

For the July 2026 PE Civil: Structural exam, stay within the April 2024 Civil: Structural specification and its listed editions: ASCE 7-16, ACI 318-14, the AISC Steel Construction Manual 15th edition, and the specified July 2020 Title 29 CFR excerpts. Use the current PE Civil Reference Handbook for mechanics. Do not substitute the April 2027 standards or PE Structural/SE construction content.

A Stage Is a Separate Structural Model

At each stage, ask four questions:

• What exists? List installed members, connections, diaphragms, braces, shores, and foundations.
• What carries load now? Composite action, continuity, curing strength, and permanent bracing may not yet exist.
• What loads are present now? Include material being placed, workers, equipment, stored bundles, temporary systems, and applicable environmental effects.
• What changes next? Shore removal, concrete placement, brace release, a pick, or connection completion can transfer load suddenly.

The final analysis model often assumes conditions created only after construction: a cured composite slab braces a steel beam; a complete diaphragm distributes lateral load; a welded or bolted connection has full capacity; a wall has top and bottom restraint. Using those assumptions early can hide an unstable stage.

Construction-Load Inventory

The applicable standard, project documents, engineered means and methods, and problem statement control numerical values and combinations. OSHA provisions set safety requirements within their scope; they are not a substitute for calculating member force, stability, or temporary-support capacity.

Stage-by-Stage Decision Workflow

1. Define the stage and transition. State what has been installed and what operation occurs.
2. Draw the temporary load path. Trace load to ground, including forms, shores, reshores, erection braces, and incomplete connections.
3. Inventory simultaneous loads. Separate uniform, patch, point, dynamic, and environmental actions.
4. Use stage-appropriate properties. Check actual concrete strength at the time, noncomposite steel properties, temporary unbraced lengths, and connection completion.
5. Apply the controlling construction combination. Do not borrow a final-state combination without confirming applicability.
6. Check strength, serviceability, and stability. Local bearing, deflection, overturning, sliding, buckling, and global stability can govern.
7. Check load transfer at the next step. Removing a shore or brace is itself a structural event.
8. Document assumptions and hold points. A sequence-dependent design fails if the field sequence silently changes.

Worked Example: Fresh Slab on Form Joists

Form joists at 2.0 ft spacing span 10 ft between supports. They carry a 6 in fresh concrete slab with unit weight 150 pcf, formwork weighing 8 psf, and a specified construction live load of 50 psf. Find the service line load, simple-span reaction at each end, and maximum moment for one joist.

1. Fresh concrete load

q_c = (6/12 ft)(150 pcf) = 75 psf

2. Total construction area load

q_total = 75 + 8 + 50 = 133 psf

3. Convert with joist spacing

w = (133 psf)(2.0 ft) = 266 plf = 0.266 klf

4. Reactions

R = wL/2 = (0.266 klf)(10 ft)/2 = 1.33 kips at each end.

5. Maximum simple-span moment

M_max = wL^2/8 = (0.266)(10^2)/8 = 3.33 kip-ft

These are service demands for the stated uniform construction case. A buggy wheel, hose reaction, or stockpile may require a separate concentrated or patch-load analysis. The 75 psf concrete weight must not be added again as permanent slab dead load in the same stage calculation; it is the same physical concrete, classified here by its condition and load path during placement. Later, after curing and shore removal, that slab becomes part of the permanent dead load carried by the completed system.

Three Sequence Traps

Noncomposite steel: A final composite beam may resist load with the cured slab, but during placement the bare steel section can carry wet concrete, deck, workers, and equipment. Its stiffness, strength, lateral bracing, and unbraced length must match that stage.

Shoring and reshoring: Shores can transmit new slab loads into floors below. Removing or relocating them redistributes load among slabs of different ages and strengths. Checking only the newest slab misses the multi-level load path.

Precast or wall erection: A panel that is stable after roof and diaphragm connections are complete may overturn before those connections exist. Temporary braces, anchors, foundations, and release sequence must form a stable system at every step.

Exam-Day Review

For any construction scenario, write the stage next to the sketch. Circle missing permanent elements, draw temporary supports to ground, and label loads by type. Then ask whether self-weight has been counted once, whether localized storage or equipment must be checked separately, whether material properties reflect the actual age/configuration, and whether the next removal or release changes the force path. This discipline prevents the classic error of analyzing a temporary structure as though construction were already finished.