Wind Loads

Structural Design · FE Reference Handbook section

Structural Design

5 formulas

10 exam-style examples

~55 min

All Structural Design lectures

Learning objectives

What you must be able to do before leaving this section.

This chapter section covers Wind Loads within Structural Design. Read it the way you would read a textbook chapter: the theory first so the relations mean something, then every equation with its use and its trap, then 10 fully worked examples with the arithmetic shown line by line, and finally a self-check you should be able to answer without notes.

Explain, in your own words, what wind loads describes physically and when it applies.
State every one of the 5 relations the handbook lists here and name each symbol with its unit.
Select the correct relation from the wording of an exam stem within 20 seconds.
Carry a complete solution from givens to a "most nearly" answer with the correct unit.
Recognise the distractors generated by the unit trap: f'c and Fy in ksi with areas in in² give kips.

Lecture

Why this section exists. Wind Loads is the part of Structural Design that lets you connect a reinforced concrete or steel member being checked to a number you can defend. Before any equation is useful you must be able to picture the physical situation it describes; the schematic below is that picture.

How the theory is built. The handbook prints results, not derivations. Each relation in this section comes from one governing principle applied to the idealised system: state the principle, impose the stated assumptions, and the printed equation follows. Knowing which assumption each relation rests on is what lets you reject a wrong answer choice in seconds.

How it is examined. Items from this page are written as a factored demand compared against φ times a nominal capacity. Roughly two thirds are direct substitution, one third require one intermediate quantity from a neighbouring relation, and a small number are conceptual — testing whether you know the assumption, not the arithmetic.

The habit that earns the points. Unit discipline. f'c and Fy in ksi with areas in in² give kips. Every relation below is dimensionally consistent only when that rule is honoured, and the distractor set is deliberately built from candidates who ignored it. Write the unit next to every number you substitute, every time.

How to study this page. Read the theory, then cover the formula cards and try to reproduce each relation from its description. Then work the examples with the solution hidden, revealing one line at a time. Finish with the self-check questions; if you cannot answer one, return to the matching formula card.

Bolted connection at the bottom chord of a steel truss bridge. — Photo 1. Where this shows up in practice: wind loads.
HAER / Library of Congress, public domain

Structural Design — Wind Loads: reference schematic for orienting the symbols used in this section.

Theory, developed

Read this before the equations — it is what makes them memorable.

The physical situation

Every item from this section describes a reinforced concrete or steel member being checked. Sketch it before you compute — a labelled sketch with the givens on it converts a wordy stem into a solvable problem and exposes the quantity the examiner left out on purpose.

The governing principle

The 5 relations on this page are consequences of one principle applied to that idealised system. Identify which quantity is conserved, balanced, or defined, and the correct equation follows without memorisation.

Assumptions and limits of validity

Each printed relation carries silent assumptions — linearity, steady state, uniformity, small deformation, or standard conditions, depending on the subject. Conceptual exam items are written by violating exactly one of these, so read the sentence above the equation as carefully as the equation itself.

Solution procedure you should automate

1) Read the last sentence of the stem to identify the requested quantity. 2) Locate the relation on this page whose left-hand side is that quantity. 3) Tabulate the givens with units and mark the missing symbol. 4) If a symbol is missing, find the one relation that produces it. 5) Rearrange symbolically, substitute once, evaluate, and round only at the end.

Notation used in this section

qz	Quantity produced by "qz = 0.00256 Kz Kz t Kd V 2 (lb/ft2)" — read its definition and unit from the handbook line directly above the equation.
Kd	Quantity produced by "Kd = wind directionality factor = 0.85 for most structures" — read its definition and unit from the handbook line directly above the equation.
Kz	Quantity produced by "Kz = velocity pressure exposure coefficient" — read its definition and unit from the handbook line directly above the equation.
Kzt	Quantity produced by "Kzt = topographic factor = 1.0 for flat ground" — read its definition and unit from the handbook line directly above the equation.
V	Quantity produced by "V = basic wind speed (mph)" — read its definition and unit from the handbook line directly above the equation.

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

Velocity pressure at height z
where
Velocity Pressure Exposure Coefficient, Kz
Exposure
Height above Ground (ft) B C D
Suburban Open Terrain Open Water
0–15 0.57 0.85 1.03
20 0.62 0.90 1.08
25 0.66 0.94 1.12

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1

Velocity pressure and windward wall pressure — Wind Loads

A building in a region with V = 115 mph has Kz = 0.79, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 115 mph
Kz = 0.79
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 11 5^{2} = 13, 225$
Substituting
$q z = 0.00256 (0.79) (1.0) (0.85) (13, 225)$
Evaluate
$q z = 22.73 p s f$
Wall pressure
$p = q z GC p = 22.73 (0.85) (0.8) = 15.46 p s f$

Answer: qz ≈ 22.7 psf, windward p ≈ 15.5 psf

Why the other options are there

0.20 psf (V not squared)
22.7 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 2

Velocity pressure and windward wall pressure — Wind Loads (2)

A building in a region with V = 115 mph has Kz = 0.82, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 115 mph
Kz = 0.82
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 11 5^{2} = 13, 225$
Substituting
$q z = 0.00256 (0.82) (1.0) (0.85) (13, 225)$
Evaluate
$q z = 23.60 p s f$
Wall pressure
$p = q z GC p = 23.60 (0.85) (0.8) = 16.05 p s f$

Answer: qz ≈ 23.6 psf, windward p ≈ 16.0 psf

Why the other options are there

0.21 psf (V not squared)
23.6 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 3

Velocity pressure and windward wall pressure — Wind Loads (3)

A building in a region with V = 115 mph has Kz = 0.90, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 115 mph
Kz = 0.90
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 11 5^{2} = 13, 225$
Substituting
$q z = 0.00256 (0.90) (1.0) (0.85) (13, 225)$
Evaluate
$q z = 25.90 p s f$
Wall pressure
$p = q z GC p = 25.90 (0.85) (0.8) = 17.61 p s f$

Answer: qz ≈ 25.9 psf, windward p ≈ 17.6 psf

Why the other options are there

0.23 psf (V not squared)
25.9 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 4

Velocity pressure and windward wall pressure — Wind Loads (4)

A building in a region with V = 130 mph has Kz = 1.03, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 130 mph
Kz = 1.03
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 13 0^{2} = 16, 900$
Substituting
$q z = 0.00256 (1.03) (1.0) (0.85) (16, 900)$
Evaluate
$q z = 37.88 p s f$
Wall pressure
$p = q z GC p = 37.88 (0.85) (0.8) = 25.76 p s f$

Answer: qz ≈ 37.9 psf, windward p ≈ 25.8 psf

Why the other options are there

0.29 psf (V not squared)
37.9 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 5

Velocity pressure and windward wall pressure — Wind Loads (5)

A building in a region with V = 90 mph has Kz = 0.89, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 90 mph
Kz = 0.89
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 9 0^{2} = 8, 100$
Substituting
$q z = 0.00256 (0.89) (1.0) (0.85) (8, 100)$
Evaluate
$q z = 15.69 p s f$
Wall pressure
$p = q z GC p = 15.69 (0.85) (0.8) = 10.67 p s f$

Answer: qz ≈ 15.7 psf, windward p ≈ 10.7 psf

Why the other options are there

0.17 psf (V not squared)
15.7 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 6

Velocity pressure and windward wall pressure — Wind Loads (6)

A building in a region with V = 115 mph has Kz = 0.72, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 115 mph
Kz = 0.72
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 11 5^{2} = 13, 225$
Substituting
$q z = 0.00256 (0.72) (1.0) (0.85) (13, 225)$
Evaluate
$q z = 20.72 p s f$
Wall pressure
$p = q z GC p = 20.72 (0.85) (0.8) = 14.09 p s f$

Answer: qz ≈ 20.7 psf, windward p ≈ 14.1 psf

Why the other options are there

0.18 psf (V not squared)
20.7 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 7

Velocity pressure and windward wall pressure — Wind Loads (7)

A building in a region with V = 130 mph has Kz = 0.74, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 130 mph
Kz = 0.74
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 13 0^{2} = 16, 900$
Substituting
$q z = 0.00256 (0.74) (1.0) (0.85) (16, 900)$
Evaluate
$q z = 27.21 p s f$
Wall pressure
$p = q z GC p = 27.21 (0.85) (0.8) = 18.50 p s f$

Answer: qz ≈ 27.2 psf, windward p ≈ 18.5 psf

Why the other options are there

0.21 psf (V not squared)
27.2 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 8

Velocity pressure and windward wall pressure — Wind Loads (8)

A building in a region with V = 90 mph has Kz = 0.84, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 90 mph
Kz = 0.84
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 9 0^{2} = 8, 100$
Substituting
$q z = 0.00256 (0.84) (1.0) (0.85) (8, 100)$
Evaluate
$q z = 14.81 p s f$
Wall pressure
$p = q z GC p = 14.81 (0.85) (0.8) = 10.07 p s f$

Answer: qz ≈ 14.8 psf, windward p ≈ 10.1 psf

Why the other options are there

0.16 psf (V not squared)
14.8 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 9

Velocity pressure and windward wall pressure — Wind Loads (9)

A building in a region with V = 115 mph has Kz = 0.73, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 115 mph
Kz = 0.73
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 11 5^{2} = 13, 225$
Substituting
$q z = 0.00256 (0.73) (1.0) (0.85) (13, 225)$
Evaluate
$q z = 21.01 p s f$
Wall pressure
$p = q z GC p = 21.01 (0.85) (0.8) = 14.29 p s f$

Answer: qz ≈ 21.0 psf, windward p ≈ 14.3 psf

Why the other options are there

0.18 psf (V not squared)
21.0 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Example 10

Velocity pressure and windward wall pressure — Wind Loads (10)

A building in a region with V = 90 mph has Kz = 1.00, Kzt = 1.0 and Kd = 0.85. Find the velocity pressure and the windward wall design pressure using G = 0.85 and Cp = 0.8.

Given

V = 90 mph
Kz = 1.00
Kzt = 1.0
Kd = 0.85
G = 0.85
Cp = 0.8

Find

qz and windward pressure p

Start with the thinking

Velocity pressure varies with the SQUARE of the wind speed.
0.00256 already converts mph² to psf — do not convert V to ft/s.

Step-by-step solution

Velocity pressure
$q z = 0.00256 K z K z t K d V^{2}$
Speed squared
$V^{2} = 9 0^{2} = 8, 100$
Substituting
$q z = 0.00256 (1.00) (1.0) (0.85) (8, 100)$
Evaluate
$q z = 17.63 p s f$
Wall pressure
$p = q z GC p = 17.63 (0.85) (0.8) = 11.99 p s f$

Answer: qz ≈ 17.6 psf, windward p ≈ 12.0 psf

Why the other options are there

0.20 psf (V not squared)
17.6 psf reported as the wall pressure (G and Cp omitted)

Reference: FE Reference Handbook — Structural Design → Wind Loads

Self-check

Answer these without notes before moving on.

Without looking, state the relation on this page whose left-hand side is the quantity most often requested, and name every symbol in it.
Which assumption, if violated, makes the main relation of this section invalid?
Given a reinforced concrete or steel member being checked, what is the first quantity you would compute, and why that one first?
Which unit conversion in this subject most often produces a wrong answer choice, and what is its numerical factor?
Rework Example 1 above from the givens alone, without reading the solution lines.

Chapter summary

Wind Loads contains 5 relations; you must be able to find this page in under 15 seconds.
Exam style: a factored demand compared against φ times a nominal capacity.
Unit rule: f'c and Fy in ksi with areas in in² give kips.
Work the 10 examples until the solution path, not the answer, is automatic.

Common traps in this section

f'c and Fy in ksi with areas in in² give kips
Answering the intermediate quantity instead of the quantity requested.
Rounding intermediate values before the final step.
Using a relation from an adjacent handbook section that shares a symbol.
Skipping the sketch — most lost points on this page start with a misread geometry.

Wind Loads

Learning objectives

Lecture

Theory, developed

Notation used in this section

Handbook notes for this section

Core formulas for this FE topic

qz=0.00256KzKztKdV2(lb/ft2​)

Kd=winddirectionalityfactor=0.85formoststructures

Kz=velocitypressureexposurecoefficient

Kzt=topographicfactor=1.0forflatground

V=basicwindspeed(mph)

Worked exam-style examples

Self-check

Chapter summary

Common traps in this section