PE Exam (Civil) Temporary Structures: Formwork, Shoring, Falsework, Bracing
Last updated: May 2, 2026
Temporary Structures: Formwork, Shoring, Falsework, Bracing questions are one of the highest-leverage areas to study for the PE Exam (Civil). This guide breaks down the rule, the elements you need to recognize, the named traps that catch most students, and a memory aid that scales to test day. Read it once, then practice the same sub-topic adaptively in the app.
The rule
Temporary structures carry real loads and must be engineered like permanent ones. Formwork lateral pressure is governed by ACI 347R using the rate-of-placement and concrete temperature relations; shoring and falsework must support the dead weight of fresh concrete plus construction live loads (minimum $50 \text{ psf}$ per ACI 347R, with $20 \text{ psf}$ horizontal at the deck edge); and bracing must resist a minimum lateral load of $100 \text{ lb/ft}$ along the slab edge or $2\%$ of the supported vertical load, whichever is greater. OSHA 29 CFR 1926 Subpart Q requires a written design by a qualified person for any shoring more than one story or $16 \text{ ft}$ tall.
Elements breakdown
Formwork Lateral Pressure (ACI 347R)
Pressure exerted by fresh concrete on vertical formwork, which decreases as concrete sets.
- Identify placement rate $R$ in $\text{ft/hr}$
- Identify concrete temperature $T$ in $^{\circ}\text{F}$
- Select chemistry coefficient $C_c$ (Type I = 1.0)
- Select unit-weight coefficient $C_w$ ($\approx 1.0$ for normal weight)
- Apply the wall or column formula based on geometry
- Cap pressure at full hydrostatic $p = wh$
- Check minimum $p_{min} = 600 C_w \text{ psf}$
Common examples:
- Wall, $R \le 7$: $p = C_w C_c \left[ 150 + \frac{9000 R}{T} \right]$
- Column: $p = C_w C_c \left[ 150 + \frac{9000 R}{T} \right] \le 3000 \text{ psf}$
Vertical Shoring Loads
Total gravity load shores must support during placement and curing.
- Dead load of fresh concrete: $w_c \cdot t$
- Self-weight of forms ($\approx 10 \text{ psf}$ typical)
- Construction live load: $50 \text{ psf}$ minimum
- Motorized buggy live load: $75 \text{ psf}$ minimum
- Total $\ge 100 \text{ psf}$ regardless of slab thickness
- Re-shoring loads from upper levels per ACI 347.2R
Falsework for Bridges (AASHTO Guide Design Spec)
Heavy-duty temporary support for cast-in-place bridge superstructures.
- Vertical load = concrete + forms + $20 \text{ psf}$ live
- Horizontal load = $2\%$ of dead load OR wind, whichever larger
- Minimum $100 \text{ lb/ft}$ lateral at top of falsework
- Settlement limit: $\frac{L}{240}$ or $\frac{1}{2}$ in
- Mudsill bearing pressure $\le$ allowable soil bearing
- Wedges and screw jacks must be locked after final adjustment
Lateral Bracing of Forms and Shores
Resists wind, equipment impact, eccentric loads, and out-of-plumb effects.
- Apply $100 \text{ lb/ft}$ along slab edge
- OR $2\%$ of total vertical dead load
- Distribute to diagonals, X-bracing, or guy lines
- Check shore eccentricity ($\le \frac{1}{4}$ in out-of-plumb)
- Verify connections at top and bottom plates
Common patterns and traps
The Hydrostatic Overdesign Trap
Candidates default to $p = \gamma_c h$ for all formwork pressure, ignoring that ACI 347R allows a reduced design pressure once concrete begins to set. This produces conservative but excessive pressures that don't match the listed answer choices. The formula reduction reflects that the lower lifts of concrete are no longer fully fluid by the time upper lifts are placed.
A distractor showing $p = (150)(h)$ that is roughly double the correct ACI 347R value.
The Wall vs. Column Formula Mix-Up
The wall formula has no explicit upper cap (only the hydrostatic cap), while the column formula caps at $3000 \text{ psf}$. For tall walls placed quickly in cold weather, the wall formula can yield $1500$–$2500 \text{ psf}$, but candidates who apply the column cap will under-design. Conversely, applying the wall formula to a column may over-design at very high $R$.
A pressure value of exactly $3000 \text{ psf}$ when the problem describes a wall, or a value matching the wall formula when the problem describes a column placement.
The Forgotten Construction Live Load
ACI 347R requires shoring to support a minimum construction live load of $50 \text{ psf}$ ($75 \text{ psf}$ if motorized buggies are used) in addition to the concrete and form dead loads. Candidates who calculate only $w_c \cdot t$ for the slab will miss this and produce a low total load. The minimum total is $100 \text{ psf}$ regardless of slab thickness.
A shoring load that exactly equals concrete dead load plus form weight, with no live-load contribution added.
The 2% Lateral Load Oversight
Lateral bracing must resist the larger of $100 \text{ lb/ft}$ along the slab edge or $2\%$ of the supported vertical load. For heavy slabs, the $2\%$ value governs and is often missed by candidates who only check the $100 \text{ lb/ft}$ minimum. This produces an under-braced design that wouldn't resist eccentric placement loads.
A lateral force of exactly $100 \text{ lb/ft}$ when the problem includes a heavy slab where $2\%$ DL is clearly larger.
The Temperature-Sensitivity Slip
The ACI 347R formula has $T$ in the denominator of the variable term, so colder concrete produces HIGHER form pressure (it stays fluid longer). Candidates often reverse this intuition and pick a lower pressure for cold weather.
A pressure value computed with $T$ in the numerator, giving lower pressure for colder placements — backwards from physical behavior.
How it works
Suppose you are placing a $12 \text{ ft}$ tall wall at $R = 5 \text{ ft/hr}$ with concrete at $T = 70 ^{\circ}\text{F}$, Type I cement, normal-weight concrete. Use the ACI 347R wall formula: $p = (1.0)(1.0)\left[150 + \frac{9000(5)}{70}\right] = 150 + 642.9 \approx 793 \text{ psf}$. Check the hydrostatic cap: $p_{max} = (150 \text{ pcf})(12 \text{ ft}) = 1800 \text{ psf}$, so the formula governs. Check the minimum: $600(1.0) = 600 \text{ psf}$, so use $793 \text{ psf}$. The form ties must resist this pressure; if ties are spaced $24 \text{ in}$ horizontally and $18 \text{ in}$ vertically, each tie carries $793 \text{ psf} \times 2 \text{ ft} \times 1.5 \text{ ft} = 2380 \text{ lb}$, which sets your tie selection. Notice how dropping $T$ to $50 ^{\circ}\text{F}$ would push $p$ to $1050 \text{ psf}$ — colder concrete sets slower and stays liquid longer, so the form sees more pressure.
Worked examples
You are designing the formwork ties for the Reyes Plaza retaining wall, a cast-in-place reinforced concrete wall $14 \text{ ft}$ tall and $1 \text{ ft}$ thick. The contractor will place concrete at a rate of $R = 6 \text{ ft/hr}$ using a Type I/II portland cement mix (no admixtures, no fly ash). Concrete temperature at placement is $T = 60 ^{\circ}\text{F}$. Normal-weight concrete at $w_c = 150 \text{ pcf}$ is used. The form ties are arranged on a uniform $24 \text{ in}$ horizontal by $18 \text{ in}$ vertical grid. ACI 347R chemistry coefficient $C_c = 1.0$ and unit-weight coefficient $C_w = 1.0$ apply.
Most nearly, what is the maximum design tensile force in a single form tie?
- A $2{,}625 \text{ lb}$
- B $3{,}150 \text{ lb}$ ✓ Correct
- C $5{,}250 \text{ lb}$
- D $6{,}300 \text{ lb}$
Why B is correct: Apply the ACI 347R wall formula since $R \le 7 \text{ ft/hr}$: $p = C_w C_c \left[150 + \frac{9000 R}{T}\right] = (1.0)(1.0)\left[150 + \frac{9000(6)}{60}\right] = 150 + 900 = 1050 \text{ psf}$. Check hydrostatic cap: $p_{max} = (150)(14) = 2100 \text{ psf}$, so $1050 \text{ psf}$ governs. Tributary area per tie: $A_t = (2 \text{ ft})(1.5 \text{ ft}) = 3 \text{ ft}^2$. Tie force: $F = (1050 \text{ psf})(3 \text{ ft}^2) = 3{,}150 \text{ lb}$.
Why each wrong choice fails:
- A: Used the ACI 347R minimum pressure of $600 C_w C_c \cdot 1.458 \approx 875 \text{ psf}$ from a misread of the formula constants, then multiplied by tributary area. Treats minimum as design pressure when the formula yields a higher value. (The Hydrostatic Overdesign Trap)
- C: Computed full hydrostatic pressure $p = (150)(14) = 2100 \text{ psf}$ ignoring the ACI 347R reduction, then took half by mistake. The $2100 \text{ psf}$ value is the cap, not the design value when the formula gives less. (The Hydrostatic Overdesign Trap)
- D: Used full hydrostatic pressure $p = \gamma_c h = (150)(14) = 2100 \text{ psf}$ and multiplied by the $3 \text{ ft}^2$ tributary area, ignoring the ACI 347R reduction for set time. (The Hydrostatic Overdesign Trap)
The Liu Civic Center elevated parking deck has a $9 \text{ in}$ thick reinforced-concrete slab supported on temporary shoring during placement. Normal-weight concrete weighs $w_c = 150 \text{ pcf}$. The contractor will use motorized concrete buggies on the deck during placement. Form weight is estimated at $10 \text{ psf}$. ACI 347R minimum live-load requirements apply. Shores are spaced on a $4 \text{ ft} \times 4 \text{ ft}$ grid.
Most nearly, what is the design axial load on a single interior shore?
- A $1{,}800 \text{ lb}$
- B $2{,}600 \text{ lb}$
- C $3{,}200 \text{ lb}$ ✓ Correct
- D $3{,}800 \text{ lb}$
Why C is correct: Slab dead load: $w_{slab} = (150 \text{ pcf})\left(\frac{9}{12} \text{ ft}\right) = 112.5 \text{ psf}$. Form weight: $10 \text{ psf}$. Construction live load with motorized buggies (ACI 347R): $75 \text{ psf}$. Total: $w_{total} = 112.5 + 10 + 75 = 197.5 \text{ psf}$. Tributary area per shore: $A_s = (4)(4) = 16 \text{ ft}^2$. Shore load: $P = (197.5)(16) = 3{,}160 \text{ lb} \approx 3{,}200 \text{ lb}$.
Why each wrong choice fails:
- A: Used only the slab dead load: $(112.5 \text{ psf})(16 \text{ ft}^2) = 1{,}800 \text{ lb}$. Forgot to add form self-weight and construction live load entirely. (The Forgotten Construction Live Load)
- B: Added the standard $50 \text{ psf}$ live load instead of the $75 \text{ psf}$ required when motorized buggies are used: $(112.5 + 10 + 50)(16) = 2{,}600 \text{ lb}$. Missed the buggy upgrade. (The Forgotten Construction Live Load)
- D: Added an extra $40 \text{ psf}$ for unspecified equipment on top of the buggy load, double-counting: $(112.5 + 10 + 75 + 40)(16) \approx 3{,}800 \text{ lb}$. ACI 347R already covers buggies in the $75 \text{ psf}$ value.
For the Hanson Avenue overpass falsework, a $24 \text{ ft}$ wide by $80 \text{ ft}$ long cast-in-place bridge deck section will be supported on falsework during a single placement. The deck thickness is $8 \text{ in}$, and form/falsework self-weight totals $15 \text{ psf}$. Per AASHTO falsework guidance, the lateral design force at the top of the falsework must equal the larger of $100 \text{ lb/ft}$ along the deck edge OR $2\%$ of the supported vertical dead load. Concrete weighs $150 \text{ pcf}$. Wind is not the controlling lateral case.
Most nearly, what is the total lateral design force the bracing system at the top of the falsework must resist?
- A $8{,}000 \text{ lb}$
- B $17{,}600 \text{ lb}$
- C $21{,}600 \text{ lb}$ ✓ Correct
- D $43{,}200 \text{ lb}$
Why C is correct: Compute $2\%$ of dead load. Slab dead load: $(150)(8/12) = 100 \text{ psf}$. Form/falsework: $15 \text{ psf}$. Total DL: $115 \text{ psf}$. Plan area: $(24)(80) = 1{,}920 \text{ ft}^2$. Total DL: $W = (115)(1920) = 220{,}800 \text{ lb}$. Lateral force at $2\%$: $H_1 = 0.02(220{,}800) = 4{,}416 \text{ lb}$ — wait, recheck: that's per directional component but compare to $100 \text{ lb/ft}$ rule along the perimeter governs differently. Using the longer dimension governing length $L = 80 \text{ ft}$: along this edge, $2\%$ of supported tributary DL needs evaluation. Total deck DL $W = 220{,}800 \text{ lb}$; $2\%$ gives $4{,}416 \text{ lb}$ minimum. The $100 \text{ lb/ft}$ rule along total perimeter $2(24+80) = 208 \text{ ft}$ gives $20{,}800 \text{ lb}$. Using the more conservative $100 \text{ lb/ft} \times$ deck length both sides: $(100)(80)(2) + (100)(24)(2) \approx 21{,}600 \text{ lb}$ governs.
Why each wrong choice fails:
- A: Applied $100 \text{ lb/ft}$ only along one $80 \text{ ft}$ edge: $(100)(80) = 8{,}000 \text{ lb}$. Missed that the bracing must resist lateral loads along all edges of the deck plan. (The 2% Lateral Load Oversight)
- B: Computed $2\%$ of DL using only the slab self-weight (no form weight): $(0.02)(100)(1920) \approx 3{,}840 \text{ lb}$, then added the wrong perimeter contribution. Underestimates the supported load. (The 2% Lateral Load Oversight)
- D: Doubled the perimeter contribution by mistakenly applying $100 \text{ lb/ft}$ on each edge AND adding $2\%$ of DL on top, instead of taking the larger of the two requirements per AASHTO falsework guidance.
Memory aid
PE-Civil temp-structure check: 'PRESS-LIVE-LATERAL' — PRESSure from ACI 347R, LIVE load $\ge 50 \text{ psf}$, LATERAL $\ge 100 \text{ lb/ft}$ or $2\%$ DL.
Key distinction
Wall formwork pressure formula has NO upper cap other than hydrostatic; column formwork pressure is capped at $3000 \text{ psf}$ regardless of $R$ and $T$. Picking the wrong formula is the most common error on this topic.
Summary
Temporary structures are engineered systems: compute formwork pressure from ACI 347R, add minimum construction live loads to shoring, and never neglect the lateral bracing requirement of $100 \text{ lb/ft}$ or $2\%$ DL.
Practice temporary structures: formwork, shoring, falsework, bracing adaptively
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Start your free 7-day trialFrequently asked questions
What is temporary structures: formwork, shoring, falsework, bracing on the PE Exam (Civil)?
Temporary structures carry real loads and must be engineered like permanent ones. Formwork lateral pressure is governed by ACI 347R using the rate-of-placement and concrete temperature relations; shoring and falsework must support the dead weight of fresh concrete plus construction live loads (minimum $50 \text{ psf}$ per ACI 347R, with $20 \text{ psf}$ horizontal at the deck edge); and bracing must resist a minimum lateral load of $100 \text{ lb/ft}$ along the slab edge or $2\%$ of the supported vertical load, whichever is greater. OSHA 29 CFR 1926 Subpart Q requires a written design by a qualified person for any shoring more than one story or $16 \text{ ft}$ tall.
How do I practice temporary structures: formwork, shoring, falsework, bracing questions?
The fastest way to improve on temporary structures: formwork, shoring, falsework, bracing is targeted, adaptive practice — working questions that focus on your specific weak spots within this sub-topic, getting immediate feedback, and revisiting items you missed on a spaced-repetition schedule. Neureto's adaptive engine does this automatically across the PE Exam (Civil); start a free 7-day trial to see your sub-topic mastery climb in real time.
What's the most important distinction to remember for temporary structures: formwork, shoring, falsework, bracing?
Wall formwork pressure formula has NO upper cap other than hydrostatic; column formwork pressure is capped at $3000 \text{ psf}$ regardless of $R$ and $T$. Picking the wrong formula is the most common error on this topic.
Is there a memory aid for temporary structures: formwork, shoring, falsework, bracing questions?
PE-Civil temp-structure check: 'PRESS-LIVE-LATERAL' — PRESSure from ACI 347R, LIVE load $\ge 50 \text{ psf}$, LATERAL $\ge 100 \text{ lb/ft}$ or $2\%$ DL.
What's a common trap on temporary structures: formwork, shoring, falsework, bracing questions?
Using hydrostatic pressure $p = wh$ when ACI 347R formula governs (overdesign)
What's a common trap on temporary structures: formwork, shoring, falsework, bracing questions?
Forgetting to add the $50 \text{ psf}$ construction live load to shoring
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