Structural Design of Signposts and Billboards - Structville (2024)

As the name implies, signposts are post bearing structures that offer information or guidance to people. They are a prominent feature of our highways, streets, city centers, villages, and areas of public gathering. Signposts are usually placed strategically away from obstruction as they are intended to show information like route direction, warnings, route assurance, traffic signs, commercial advertisem*nts, etc.

Structural Design of Signposts and Billboards - Structville (2)

EN 12899-1:2007 requires that signposts made of steel structures should conform with EN 1993-1-1:2005 (Eurocode 3). One of the major concerns in the design of billboards and signposts is the risk of failure under wind load, which has serious economic and safety consequences. A failed highway sign structure can cause injury to pedestrians, damage vehicles, and obstruct traffic. As a result, such structures that are exposed to the public must satisfy all needed safety considerations. Additional risks of vehicles colliding with sign structures should also be checked, with passive protection provided for such structures.

Actions on Sign Structures

Wind action on signposts and billboards can be evaluated according to EN 1991-1-4:2005 (Eurocode 1 Part 4). ASCE 7-10 code of practice can also be used for the evaluation of wind load on sign structures. The National Annex to BS EN 12899-1:2007 recommends suitable wind loads for the majority of signs in the UK. Whilst is it more conservative than performing a full analysis, it is simpler and quicker.

Other forces that may need to be taken into account when designing sign structures are point loads and dynamic snow load (not applicable in Nigeria). The UK National Annex recommends that signs should be able to withstand a force of 0.5 kN applied at any point. This represents the load that might be exerted by, for example, a glancing blow from a vehicle mirror, a falling branch or malicious interference with the sign. This point load is the critical factor only for very small signs, but for signs mounted on a single support, it causes torsional forces that need to be considered.

For large billboards, live loads and the weight of services should be accounted for the in the design.

Design example
Provide adequate sections for a sign structure with the configuration shown below. The sign post is located in an area that is 76 m above sea level with a wind speed of 35 m/s.

Structural Design of Signposts and Billboards - Structville (3)

Mounting height above ground hm = 2.0 m
Width of sign face l = 3.0 m
Height of sign face b = 2.0 m
Total height H = hm + b = 4.0 m
Height to centroid of sign area z = hm + b/2 = 3.0 m
Depth of post buried above foundation hb = 200 mm

Basic wind velocity
Let the basic wind velocity from wind map = vb,map = 35 m/s
The altitude of site above sea level A = 76 m
Altitude factor calt = 1 + 0.001A = 1 + (0.001 × 76) = 1.076
vb,0 = vb,map ⋅ calt = 35 × 1.076 = 37.66 m/s

Assess Terrain Orography
Site is not very exposed site on cliff/escarpment or in a site subject to local wind funnelling. Therefore co = 1.0

Determine Design Life Requirement

Structural Design of Signposts and Billboards - Structville (4)

p = design annual probability of exceedence
p = 1/design life = 1/25 = 0.04 (for signs design life is 25 years)
K = Shape parameter = 0.2
n = exponent = 0.5

Basic Wind Velocity
vb = cdir ⋅ cseason ⋅ vb,0
cdir = directional factor = 1.0
cseason = season factor = 1.0
vb = 1.0 × 1.0 × 37.66 = 37.66 m/s

10 minute mean wind velocity having probability P for an annual exceedence is determined by:

vb,25 years = vb ⋅ cprob
vb,25 years = 37.66 × 0.96 = 36.15 m/s

Mean Wind
The mean wind velocity Vm(z) at a height z above the terrain depends on the terrain roughness and orography, and on the basic wind velocity, Vb, and should be determined using the expression below;

Vm(z) = cr(z). co(z).Vb

cr(z) is the roughness factor (defined below)
co(z) is the orography factor often taken as 1.0

cr(z)= kr. In (z/z0) for zmin ≤ z ≤ zmax
cr(z)= cr.(zmin) for z ≤ zmin

Z0 is the roughness length
kr is the terrain factor depending on the roughness length Z0 calculated using;

kr = 0.19 (Z0/Z0,II)0.07

Z0,II = 0.05m (terrain category II)
Zmin is the minimum height = 2 m
z = 3 m
Zmax is to be taken as 200 m
Kr = 0.19 (0.05/0.05)0.07 = 0.19
cr(3)= kr.In (z/z0) = 0.19 × In(3/0.05) = 0.78

Vm(3.0) = cr(z). co(z).Vb = 0.78 × 1.0 × 36.15 = 28.197 m/s

Wind turbulence
The turbulence intensity Iv(z) at height z is defined as the standard deviation of the turbulence divided by the mean wind velocity. The recommended rules for the determination of Iv(z) are given in the expressions below;

Iv(z) = σv/Vm = kl/(c0(z).In (z/z0)) for zmin ≤ z ≤ zmax
Iv(z) = Iv.(zmin) for z ≤ zmin

kl is the turbulence factor of which the value is provided in the National Annex but the recommended value is 1.0
Co is the orography factor described above
Z0 is the roughness length described above.

For the structure that we are considering, the wind turbulence factor at 3 m above the ground level;

Iv(60) = σv/Vm = k1/[c0(z).In(z/z0)] = 1/[1 × In(3/0.05)] = 0.244

Peak Velocity Pressure
The peak velocity pressure qp(z) at height z is given by the expression below;

qp(z) = [1 + 7.Iv(z)] 1/2.ρ.Vm2(z) = ce(z).qb

ρ is the air density, which depends on the altitude, temperature, and barometric pressure to be expected in the region during wind storms (recommended value is 1.25kg/m3)

ce(z) is the exposure factor given by;
ce(z) = qp(z)/qb
qb is the basic velocity pressure given by; qb = 0.5.ρ.Vb2

qp(60m) = [1 + 7(0.244)] × 0.5 × 1.25 × 28.1972 = 1345.66 N/m2

Therefore, qp(3m) = 1.345 kN/m2

Determination of force coefficient (Table NA 2 BS EN 12899)
λ = effective slenderness ratio of sign or aspect ratio
λ = l/b = 3.0 / 2.0 = 1.5
Therefore cf = 1.30

Calculation of the total wind force (Clause 5.3 of EN 1991-1-4)
Fw = cscd ⋅ cf ⋅ qp(ze) ⋅ Aref (Aref = area of sign)
cscd = 1.0 (for sign posts)

Fw = 1.0 × 1.30 × 1.345 × 3.0 × 2.0 = 10.5 kN

Partial Factor for Action γF (Table 6 EN 12899-1:2007 (E))
ULS (bending and shear) γF = 1.5
SLS (deflection) γF = 1.0
γf3 = 1.0

Design Wind Force on the sign
Fw,d = Fw ⋅ γF ⋅ γf3
Fw,d (ULS) = 10.5 × 1.5 × 1.0 = 15.75 kN
Fw,d (SLS) = 10.5 × 1.0 × 1.0 = 10.5 kN

Ultimate Action Effects
Ultimate design bending moment per post, MEd
MEd = Wind force × lever arm to foundation / number of posts
MEd = Fw,d (ULS) ⋅ (z + hb) / n
MEd = 15.75 × (3.00 + 0.2) / 2 = 25.2 kNm

Ultimate design shear per post
VEd = Wind force / number of posts
VEd = Fw,d (ULS) /2 = 15.75 / 2 = 7.9 kN

The 0.5 kN point load on the sign is not critical, since it is less than the wind action and there are no torsional effects with 2 posts.

Try circular hollow section CHS 139.7 x 8 (S355)

A = 33.1 cm2; Wpl = 139 cm3; Ix = 720 cm4

Section classification
ε = √235/fy = √(235/355) = 0.81
Tubular sections (Table 5.2, sheet 3 of EN 1993-1-1:2005):
d/t = 139.7/8 = 17.46
Limit for Class 1 section = 50ε2 = 40.7
40.7 > 17.46; section is Class 1

Member resistance at ULS
According to Table 7 of EN 12899-1:2007 (E), the material factor of safety for steel is γm = 1.05
Moment Capacity MRd = fy⋅Wplm = [(355 x 103 x 139 x 10-6)/√3)]/1.05= 46.99 kNm
MEd/MRd = 25.2/46.99 = 0.536 < 1.0 Okay

Shear capacity VRd = Av(fy/√3)/γm
Av = 2A/π = (2 x 33.1)/π = 21.027 cm2
VRd = 21.027 × 10-4 × [(355 x 103)/√3)]/1.05 = 430.96 kN
VEd/VRd = 7.9/430.96 = 0.018 < 1.0 Okay

Calculation of Temporary deflection
The wind velocity for calculating the temporary deflection (SLS) criterion is 75% of the reference wind velocity, as it is based upon a 1 year mean return period. The 0.96 factor below reverses the cprob conversion from 50 to 25 year return period used above (Clause 5.4.1, note 1 EN 12899-1).

Fwd(1 year) = Fwd (SLS) x 0.752/0.962 = 10.5 x 0.752/0.962 = 6.41 kN

Uniformly distributed load along sign face = Fw,d (1 year) / b
Fw,d (1 year) / b = 6.41/2.0 = 3.2 kN/m
where b = height of the sign face

Maximum deflection at top of sign (bending), δ

Structural Design of Signposts and Billboards - Structville (5)

E = 210000 N/mm2
I = 720 cm4
n = number of posts = 2
Other parameters are as defined above

δ = [3.2/(24 x 210000 x 720 x 104 x 2)] x [3(4000 + 200)4 – 4(2000 + 200)3 x (4000 + 200) + (2000 + 200)4] = 34.3 mm

Deflection per linear metre = δ’ = δ/(H + hb) = 34.3/(4 + 0.2)= 8.16 mm/m
Maximum temporary deflection taken as class TDB4 = 25 mm/m
8.16 mm/m < 25 mm/m. Therefore deflection is okay.

The Institution of Highway Engineers (2010): SIGN STRUCTURES GUIDE Support design for permanent UK traffic signs to BS EN 12899-1:2007 and structural Eurocodes

Structural Design of Signposts and Billboards - Structville (2024)


What is the structural design of a billboard? ›

Billboards are classified into four structural categories which are wood, steel frame, multi-mast steel, and monopole, based on the structural materials used and the underlying support system.

What are the two main structural design requirements that have to be considered during the structural design process? ›

What are the requirements of structural design?
  • Stability to prevent sliding, overturning, or buckling of the structure, or parts of it, under the action of environmental and live loads.
  • Strength to safely resist the stresses induced by loads in the various structural members.
May 27, 2021

What makes a good structural design? ›

Choosing the suitable materials, whether steel, concrete, timber, composite materials, or a combination, is key to structural design. Factors such as strength, durability, cost, and environmental impact are key considerations since each material has unique properties and advantages.

What 3 factors do you need to consider when designing a billboard? ›

Memorable, easy to understand, clear and easy to read are all factors in a good billboard ad.

What is billboard design? ›

Billboard design is a unique channel that can reach thousands of drivers a day, or just an important few. Your billboard can point future customers to your venue or leave them with a memorable piece of information.

What are the 5 stages of structural design? ›

There are mainly 5 essential steps to be followed for the design of any structure. (1) modelling, (2) load analysis, (3) structural analysis, (4) structural design and (5) detailing.

What are three things you need to consider when designing and building a structure? ›

Designing a building involves careful consideration of functionality, sustainability, aesthetics, and compliance with building codes and regulations.

What is the summary of structural design? ›

Structural design is the methodical investigation of the stability, strength and rigidity of structures. The basic objective in structural analysis and design is to produce a structure capable of resisting all applied loads without failure during its intended life.

What are the strongest structural designs? ›

The arc (think: circle) is the strongest structural shape, and in nature, the sphere is the strongest 3-d shape. The reason being is that stress is distributed equally along the arc instead of concentrating at any one point. Storage silos, storage tanks, diving helmets, space helmets, gas tanks, bubbles, planets, etc.

What is structural design examples? ›

Suspension Bridge: An example of Structural Design in civil engineering where the deck of the bridge is hung below suspension cables, requiring advanced mathematical equations to ensure safety and stability.

What is the element of structural design? ›

Structural Elements Design Manual is a manual on the practical design of structural elements that comprise a building structure, namely, timber, concrete, masonry, and steel. Practical guidance on the design of structural elements is provided in accordance with the appropriate British Standard or Code of Practice.

What is structural analysis for beginners? ›

Structural analysis is the process of using mathematical and mechanical principles to determine the magnitude of internal forces that develop in a structure in response to external loading.

What are the basic knowledge of structural engineer? ›

Structural engineering is based on the application of math and physics principles to solve complex problems involving forces, materials, and geometry. You need to have a strong foundation in calculus, linear algebra, differential equations, mechanics, dynamics, and fluid mechanics.

What is structural framing plan? ›

A structural framing plan, such as a wall, roof, deck or porch framing plan is a type of plan, usually required by planning authorities for approvals, that shows the configuration of the major structural elements usually made of materials such as timber or aluminium, their sizes and how they come together to hold the ...

What is the standard billboard format? ›

The standard bulletin billboard measures 14 feet high and 48 feet wide, and they are often seen near fast-food restaurants and highway ads that reach up to 1o ft × 40 ft and 10½ ft × 36 ft.

What is billboard format? ›

The typical size of this billboard format is: 6.096m x 3.048m or 240” x 120”. The 48-sheet-sized advertising billboards are the most popular and, of course, classic. The most common type of 48-sheets are standard printed which are typically found on the side of busy roads, shopping areas and train stations.

What are the dimensions of a billboard design? ›

Bulletins come in three standard sizes, according to the Outdoor Advertising Association of America: 14 feet high and 48 feet wide. 10 feet high and 40 feet wide. 10½ feet high and 36 feet wide.

What is the format for a billboard ad? ›

Billboard Ads have a height of 250 px and width of 970 px for an aspect ratio of 3.88:1 on desktop devices. Online advertisem*nts support JPG, PNG, and GIF formats with maximum file sizes of 150 KB. The major purpose of the Billboard Ad (970 x 250) is to push down content.

Top Articles
Latest Posts
Article information

Author: Arielle Torp

Last Updated:

Views: 5666

Rating: 4 / 5 (61 voted)

Reviews: 84% of readers found this page helpful

Author information

Name: Arielle Torp

Birthday: 1997-09-20

Address: 87313 Erdman Vista, North Dustinborough, WA 37563

Phone: +97216742823598

Job: Central Technology Officer

Hobby: Taekwondo, Macrame, Foreign language learning, Kite flying, Cooking, Skiing, Computer programming

Introduction: My name is Arielle Torp, I am a comfortable, kind, zealous, lovely, jolly, colorful, adventurous person who loves writing and wants to share my knowledge and understanding with you.