How to Select Between W and WWF Steel Girders Using Cost and Efficiency Metrics For Road Bridges

How to Select Between W and WWF Steel Girders Using Cost and Efficiency Metrics For Road Bridges

 

Selecting the optimal steel girder type is one of the most important decisions in short‑ and medium‑span bridge (SMSB) design for road bridges. In spans between 12 m and 40 m, engineers typically choose between:

• Rolled Wide-Flange (W) sections
• Welded Wide-Flange (WWF) plate girders

 

Both girder types are included in the Manual of Standard Short-Span Steel Bridges prepared by the Ontario Ministry of Transportation. The manual provides span ranges, girder sizes, weights, and performance data that allow engineers to evaluate each option using cost, span-to-depth efficiency, and span-to-weight efficiency.

 

This article explains how to make that choice using engineering metrics that directly affect project cost, fabrication feasibility, and structural performance.

 

1. Understanding the Two Girder Types

Rolled W Sections

These are hot‑rolled shapes produced in steel mills.

Advantages

• Lower fabrication cost
• Shorter procurement time
• Excellent quality control
• Ideal for spans up to ~24 m

Limitations

• Limited available depths
• Less flexibility in flange/web proportions
• May not meet stiffness requirements for longer spans

 

Welded WWF Sections

These are fabricated plate girders assembled from web and flange plates.

Advantages

• Customizable depth and flange sizes
• Higher span-to-depth efficiency
• Better control of stiffness for longer spans
• Ideal for spans > 24 m

Limitations

• Higher fabrication cost
• Longer lead time
• More welding → higher fatigue considerations

 

2. Efficiency Metrics for Girder Selection

Two key metrics determine girder efficiency:

 

2.1 Span-to-Depth Ratio

This ratio indicates how shallow a girder can be for a given span.

• Higher ratio → more efficient girder
• Lower ratio → deeper girder → more steel → higher cost

 

2.2 Span-to-Weight Ratio

This ratio indicates how much span is achieved per unit girder weight.

• Higher ratio → lighter girder → lower cost
• Lower ratio → heavier girder → higher cost

 

3. Span-to-Depth Ratios: W vs WWF

Using the girder depths from the MTO manual:

 

Rolled W Sections (12–24 m spans)

Typical span/depth ratios: 20–24

Examples:

• W610 at 12 m → ratio ≈ 19.7
• W760 at 16–18 m → ratio ≈ 21–23.7
• W1000 at 24 m → ratio ≈ 24

Interpretation: Rolled sections are efficient for short spans but reach depth limits around 24 m.

 

Welded WWF Sections (18–40 m spans)

Typical span/depth ratios: 23–26

Examples:

• WWF700 at 18 m → ratio ≈ 25.7
• WWF900 at 22 m → ratio ≈ 24.4
• WWF1600 at 40 m → ratio ≈ 25

Interpretation: WWF girders outperform rolled sections in span-to-depth efficiency, especially beyond 20–24 m.

 

4. Span-to-Weight Ratios: W vs WWF

Using girder weights from the manual:

 

Rolled W Sections

Span/weight ratios: 0.11–0.13

Examples:

• W610×91 at 12 m → 0.132
• W760×147 at 16 m → 0.109
• W920×201 at 22 m → 0.109

Interpretation: Rolled sections are weight-efficient for short spans but lose efficiency as spans increase.

 

Welded WWF Sections

Span/weight ratios: 0.09–0.13

Examples:

• WWF700×152 at 18 m → 0.118
• WWF900×169 at 22 m → 0.130
• WWF1600×431 at 40 m → 0.092

Interpretation: WWF girders are most weight-efficient in mid-range spans (18–22 m). Efficiency decreases for very long spans due to heavier webs and flanges.

 

5. Cost Comparison: W vs WWF

5.1 Rolled W Sections

• Lowest fabrication cost
• No welding required
• Lower inspection cost
• Limited depth availability → may require more girders or thicker deck for longer spans

5.2 Welded WWF Sections

• Higher fabrication cost (cutting, welding, assembly)
• Higher inspection cost (NDT, fatigue checks)
• Customizable geometry → may reduce total steel tonnage
• Often more economical for spans > 24 m despite higher fabrication cost

 

6. Practical Selection Guidelines

Use Rolled W Sections When:

• Span ≤ 20–24 m
• Rolled depth meets stiffness requirements
• Project requires rapid fabrication
• Budget is tight and rolled shapes are available
• Fatigue demands are moderate

Use Welded WWF Sections When:

• Span ≥ 24 m
• Rolled shapes are unavailable or insufficient
• High stiffness is required (e.g., high truck volume)
• Skew > 25° (WWF allows better control of flange/web proportions)
• Fatigue-sensitive details require optimized geometry

 

7. Decision Matrix (Engineer-Friendly Summary)

Criterion	Rolled W Section	Welded WWF Section
Span Range	12–24 m	18–40 m
Span-to-Depth Efficiency	Moderate (20–24)	High (23–26)
Span-to-Weight Efficiency	High for short spans	High for mid spans
Fabrication Cost	Low	High
Lead Time	Short	Longer
Fatigue Performance	Better (fewer welds)	Requires careful detailing
Customization	None	High
Best Use Case	Short spans, low cost	Medium spans, optimized stiffness

 

8. Final Engineering Recommendation

For spans up to ~20 m:

Choose Rolled W Sections — they are cheaper, lighter, and efficient.

 

For spans between 20–24 m:

Evaluate both options. WWF may offer better stiffness; W may offer lower cost.

 

For spans beyond 24 m:

Choose Welded WWF Sections — they provide superior span-to-depth efficiency and allow custom optimization.

 

Span-to-Depth and Span-to-Weight Ratios for Steel Girders in Short-Span Bridges

The Span-to-Depth and Span-to-Weight Ratios for Steel Girders in Short-Medium Span Bridges (SMSB) for Road Bridges

Short medium span steel bridges (12–40 m) rely heavily on efficient girder selection. Two of the most important performance metrics for steel girders are:

• Span-to-depth ratio
• Span-to-weight ratio

 

These ratios directly influence structural efficiency, fabrication cost, transportation feasibility, and long-term performance. The MTO Manual of Standard Short-Span Steel Bridges provides a rich dataset of girder sizes, weights, and span ranges that allow engineers to derive practical ratios for design optimization.

This article distills those insights into a clear engineering reference.

 

1. Span Range for Standard Steel Girders

From the manual:

“Spans ranging from 12 to 40 metres in length, tabulated in 2 metre increments.”

This span range covers the majority of municipal and provincial steel bridges in Ontario and aligns with typical North American practice.

 

2. Span-to-Depth Ratio for Steel Girders

The span-to-depth ratio is a key indicator of structural efficiency. A higher ratio means a shallower girder for the same span, which reduces steel tonnage and improves aesthetics.

Using the girder depths provided in the manual’s tables (W and WWF sections), we derive the following:

 

2.1 Rolled W‑Sections (No Cover Plates)

These are standard rolled shapes with depths from 610 mm to 1000 mm.

Span (m)	Girder	Depth (mm)	Span/Depth Ratio
12	W610×91	610	19.7
14	W690×125	690	20.3
16	W760×147	760	21.0
18	W760×147	760	23.7
20	W840×176	840	23.8
22	W920×201	920	23.9
24	W1000×222	1000	24.0

 

Observations

• W‑sections typically achieve span/depth ratios between 20 and 24.
• Ratios increase with span because deeper rolled sections become available.
• Rolled sections are efficient for spans up to ~24 m.

 

2.2 Welded WWF Sections (No Cover Plates)

These fabricated girders allow greater flexibility and higher efficiency.

Span (m)	Girder	Depth (mm)	Span/Depth Ratio
18	WWF700×152	700	25.7
22	WWF900×169	900	24.4
26	WWF1100×234	1100	23.6
30	WWF1200×302	1200	25.0
34	WWF1400×358	1400	24.3
40	WWF1600×431	1600	25.0

 

Observations

• WWF girders achieve span/depth ratios between 23 and 26.
• Welded sections outperform rolled sections in efficiency.
• Ideal for spans >24 m where rolled sections are no longer economical.

 

3. Span-to-Weight Ratio for Steel Girders

Span-to-weight ratio indicates how much span is achieved per unit girder weight. Higher ratios mean more efficient use of steel. Using the girder weights from the manual (e.g., W610×91 → 91 kg/m), we compute:

 

3.1 Rolled W‑Sections

Span (m)	Girder	Weight (kg/m)	Span/Weight
12	W610×91	91	0.132
14	W690×125	125	0.112
16	W760×147	147	0.109
18	W760×147	147	0.122
20	W840×176	176	0.114
22	W920×201	201	0.109
24	W1000×222	222	0.108

 

Observations

• Span/weight ratios for W‑sections cluster around 0.11–0.13.
• Efficiency decreases slightly as girder weight increases.
• Rolled sections are most efficient for shorter spans (12–18 m).

 

3.2 Welded WWF Sections

Span (m)	Girder	Weight (kg/m)	Span/Weight
18	WWF700×152	152	0.118
22	WWF900×169	169	0.130
26	WWF1100×234	234	0.111
30	WWF1200×302	302	0.099
34	WWF1400×358	358	0.095
40	WWF1600×431	431	0.092

 

Observations

• Span/weight ratios for WWF sections range 0.09–0.13.
• Welded sections are most efficient at mid-range spans (18–22 m).
• Efficiency decreases for very long spans due to heavier plate girders.

 

4. Engineering Interpretation

Rolled W‑Sections

• Best for short spans (12–20 m).
• Provide higher span-to-weight efficiency in the lower span range.
• Limited by available rolled depths.

Welded WWF Sections

• Best for medium spans (20–40 m).
• Provide higher span-to-depth efficiency due to customizable depth.
• Slightly lower span-to-weight efficiency at long spans due to heavier webs/flanges.

 

5. Practical Design Guidelines

Span-to-Depth Ratio Targets

• W‑sections: aim for 20–24
• WWF sections: aim for 23–26

Span-to-Weight Ratio Targets

• W‑sections: aim for 0.11–0.13
• WWF sections: aim for 0.10–0.13

General Rule

• Use rolled sections when available and economical.
• Use WWF sections when spans exceed rolled depth limits or when optimizing stiffness.

 

Conclusion

Span-to-depth and span-to-weight ratios are powerful tools for optimizing steel girder selection in short- and medium-span bridges. The MTO manual provides a clear dataset showing that:

• Rolled W‑sections excel in spans up to ~20 m.
• Welded WWF sections dominate spans from 20–40 m.
• Efficient designs typically fall within span/depth ratios of 20–26 and span/weight ratios of 0.10–0.13.

 

This article gives engineers a practical reference for selecting steel girders based on structural efficiency and material economy.

     #Short #Medium #Span #Bridge #SMSB

Canadian Civil Engineering Resources

Canadian Civil Engineering Resources – Junior Engineer Edition (2026)

A comprehensive national reference for emerging civil engineering professionals in Canada

Download:  Canadian Civil Engineering Resources – Junior Engineer Edition (2026).pdf

Canadian Civil Engineering Resources – Junior Engineer Edition (2026) is a professionally curated guide designed to support junior and early‑career civil engineers across Canada. Prepared by Mahmoud Sayed‑Ahmed, Ph.D., P.Eng., the document consolidates the essential codes, standards, associations, academic pathways, licensing requirements, and career development strategies that shape engineering practice in Canada.

 

What the Guide Covers

1. Codes, Standards & Technical References A detailed overview of Canada’s core engineering frameworks, including the National Building Code (NBC 2020), Canadian Highway Bridge Design Code (CHBDC S6‑19), major CSA standards, and provincial building code supplements such as the OBC, ABC, and BCBC. The guide also highlights ISO standards commonly used in Canadian engineering practice.

 

2. Construction & Industry Associations Profiles of key national and regional organizations such as the Canadian Construction Association (CCA), CSCE, ACEC, UDI, and Infrastructure Canada, emphasizing their value for networking, professional development, and industry insight.

 

3. Leading Consulting Engineering Firms A curated list of Canada’s top consulting firms—including WSP, Stantec, AECOM, Hatch, Jacobs, and others—along with their specialties and notable projects. Practical advice is provided for junior engineers seeking roles in consulting.

 

4. Major General Contractors in Canada An overview of Canada’s largest construction companies such as PCL, EllisDon, Graham, Aecon, and Ledcor, including revenue ranges, sectors, and guidance for engineers pursuing field or project engineering roles.

 

5. Licensing Bodies & Professional Engineering Pathways A province‑by‑province breakdown of engineering regulators (APEGA, PEO, EGBC, OIQ, etc.) and a clear explanation of the P.Eng. pathway, including EIT/MIT registration, competency requirements, NPPE/PPE exams, and experience documentation.

 

6. Academic Pathways & Graduate Programs A national overview of top civil engineering universities, graduate degree types (M.Eng., M.A.Sc., Ph.D.), funding opportunities (NSERC, Vanier, AGES), and major civil engineering specializations.

 

7. Credential Assessment for Internationally Trained Engineers Guidance on WES, IQAS, CES, CICIC, provincial academic assessments, language requirements, and strategic tips for internationally trained engineers navigating Canadian licensure.

 

8. Health, Safety & Professional Certifications A comprehensive list of essential safety and professional certifications—including CSTS‑09, WHMIS, First Aid/CPR, Ground Disturbance Level II, Fall Protection, NCSO, PMP, and Gold Seal Certification—with descriptions, costs, and issuing bodies.

 

9. Practical Career Roadmap for Junior Engineers A four‑phase roadmap guiding engineers from graduation to P.Eng. licensure and beyond. It covers early career setup, competency development, NPPE preparation, mentorship, specialization, leadership development, and long‑term professional growth.

Appendices Quick‑reference tables for websites, regulators, universities, certifications, and a glossary of key engineering terms.

 

Download:  Canadian Civil Engineering Resources – Junior Engineer Edition (2026).pdf

Table of Content

Section 1 — Codes, Standards & Technical References

1.1 National Building Code of Canada (NBC) 2020

1.2 Canadian Highway Bridge Design Code (CHBDC) CAN/CSA-S6-19

1.3 Canadian Standards Association (CSA) – Key Standards

1.4 National Fire Code & National Plumbing Code

1.5 Provincial Supplements – OBC, ABC, BCBC

1.6 Standards Council of Canada (SCC)

1.7 ISO Standards Relevant to Civil Engineering in Canada

Section 2 — Construction & Industry Associations

2.1–2.9 Canadian and Regional Industry Associations

Section 3 — Leading Consulting Engineering Firms in Canada

Consulting Firms Reference Table

Section 4 — Top General Contractors & Construction Companies

General Contractors Reference Table

Section 5 — Licensing Bodies & Professional Engineering Associations

5.1 Engineers Canada

5.2 APEGA (Alberta)

5.3 PEO (Ontario)

5.4 EGBC (British Columbia)

5.5 OIQ (Québec)

5.6 Other Provincial Regulators

5.7 The P.Eng. Designation – EIT Pathway

Section 6 — Academic Pathways & Graduate Programs

6.1 Top Canadian Universities for Civil Engineering

6.2 Graduate Program Types

6.3 Funding Options

6.4 Key Specializations

Section 7 — Credential Assessment for Internationally Trained Engineers

7.1–7.8 Assessment Bodies, Language Requirements & Tips

Section 8 — Health, Safety & Professional Certifications

Safety Certifications Reference Table

Section 9 — Practical Roadmap for Junior Civil Engineers in Canada

Four-Phase Career Roadmap

Appendix A — Useful Websites Quick Reference

Appendix B — Glossary of Key Terms