Bridge Structural Engineering in Ontario:
Erection Plans, Demolition & Cofferdam

Bridge Structural Engineering in Ontario

Ontario has an extensive network of bridges maintained by the Ministry of Transportation of Ontario (MTO), municipal governments, and private owners. From the major highway overpasses of the 400-series highways to smaller municipal bridges over creeks and culverts in rural counties, bridge engineering in Ontario requires compliance with a layered framework of provincial codes, regulations, and standards.

Key characteristics of Ontario bridge engineering:

• Canadian Highway Bridge Design Code (CHBDC, CSA S6) — the primary design standard for highway bridges in Ontario, adopted by reference through MTO design guidelines
• OHSA Ontario Regulation 213/91 — the construction safety regulation that mandates P.Eng.-sealed falsework and erection plans for bridge construction
• Ontario Structure Inspection Manual (OSIM) — MTO's standardized methodology for bridge inspections, used for all MTA-owned bridges
• Municipal bridge standards — cities like Toronto (City of Toronto Design Criteria for Bridges and Structures) and Ottawa have their own overlay requirements above the CHBDC baseline
• Environmental regulations — the Fisheries Act, Ontario Water Resources Act, and MECP Permit to Take Water govern any bridge work in or adjacent to watercourses

OHSA Requirements for Bridge Construction

Ontario's Occupational Health and Safety Act (OHSA) and its Construction Regulation (Ontario Regulation 213/91) impose specific requirements on bridge construction projects that engineers and contractors must understand.

P.Eng. Requirements Under O.Reg 213/91

• Section 2(1) — any structure that could endanger workers must have a P.Eng.-sealed design or inspection before, during, or after construction as directed by the Ministry of Labour
• Section 87 — falsework requiring project-specific engineered support must be designed by a P.Eng. and built according to the engineer's drawings
• Section 99 — all shoring and bracing must be designed by a P.Eng. when dimensions or loads exceed the prescriptive limits
• Section 373 — structural steel erection must follow an engineered erection plan; the erection plan must be on site and available to all workers engaged in the erection

Under O.Reg 213/91, the constructor (general contractor) is ultimately responsible for ensuring that required P.Eng. plans are obtained and followed. However, subcontractors also have responsibilities to ensure their crews follow the plans and to identify unsafe conditions to the constructor.

Bridge Erection Plans & Falsework in Ontario

A bridge erection plan (or structural stability plan) defines the construction sequence and temporary support requirements for each stage of bridge construction. In Ontario, this is governed by both OHSA O.Reg 213/91 and the CHBDC construction requirements.

What Ontario Bridge Erection Plans Must Address

• Stage-by-stage stability analysis — every construction phase must be checked for structural stability, from the first girder lift to the placement of the last section of deck
• Falsework design — temporary shoring towers, horizontal waling beams, crossbracing, and base plates must be designed for all imposed loads including concrete pour pressures, construction live loads, wind, and thermal effects
• Girder bracing — steel girders are unstable until the deck is placed; intermediate and permanent lateral bracing must be designed for the construction stage
• Crane positioning and outrigger loads — lifting sequences and crane pad loads must be analyzed relative to abutment and substructure capacity
• Precast girder placement — for prestressed concrete girder bridges, the sequence and temporary bearing conditions for each girder must be analyzed

Common Ontario Bridge Construction Types

• Steel plate girder superstructure with cast-in-place concrete deck (most common on Ontario municipal bridges)
• Precast prestressed concrete CPCI/CPCA girders with composite concrete deck (common for 2-lane rural bridges)
• Integral abutment bridges (growing in use for smaller span bridges, requiring careful thermal analysis)
• Box culverts and three-sided culvert bridges (used on lower-flow watercourses)

Bridge Demolition in Ontario

Bridge demolition in Ontario requires a demolition permit from the applicable authority (MTO Design and Contract Standards for provincial bridges, a municipal infrastructure permit for municipal bridges, or the applicable municipal or OBC permit for private bridges). OHSA requirements for temporary works and shoring plans fully apply during demolition.

Demolition Engineering Scope

• Sequential demolition plan — P.Eng.-sealed plan showing the demolition sequence and the stability of the structure at each step
• Temporary shoring — elements that can't be self-supporting during partial demolition require temporary shoring per O.Reg 213/91
• Traffic protection — work over active roadways requires Ministry of Transportation Traffic Management Guidelines compliance, engineered catch platforms or protection frames
• Marine demolition — MECP, Fisheries Act, and DFO permits govern work in or adjacent to watercourses; demolished elements must not enter the water course
• PCB and lead assessments — older Ontario bridges (pre-1980 steel) may have lead-based paint; Ontario Regulation 347 governs waste classification and disposal; OHSA O.Reg 840 governs worker protection from lead exposure

Cofferdam Design for Ontario Bridge Projects

Cofferdams are temporary watertight structures used to dewater a work area in or adjacent to a watercourse to allow substructure construction in a relatively dry environment. In Ontario, cofferdams are common for:

• New bridge pier or abutment construction in rivers and creeks
• Rehabilitation of existing concrete substructure elements (pier strengthening, scour repair, footing extensions)
• Culvert replacement and stream crossing construction

Cofferdam Engineering in Ontario

The P.Eng. designing the cofferdam must address:

• Hydrostatic head: depth of water and flood event return period during construction
• Sheet pile design: pile section, embedment depth, and water and earth pressure loads per the CFEM (Canadian Foundation Engineering Manual)
• Internal bracing: wales, struts, and corner connections per CSA S16 steel design or relevant standards
• Dewatering: groundwater inflow rates and sump pump capacity
• Flooding analysis: probability of construction flooding event and risk mitigation measures
• Fish and aquatic habitat protection: DFO (Fisheries and Oceans Canada) authorization and timing windows for work in fish-bearing watercourses

Ontario Environmental Permits for Cofferdam Work

Bridge Structural Assessment in Ontario

Ontario bridges are inspected under the Ontario Structure Inspection Manual (OSIM) — a standardized protocol obligating municipal and provincial bridge owners to conduct routine inspections every 2 years for bridges and every year for culverts and retaining walls. However, OSIM routine inspections are condition assessments, not structural engineering assessments.

A structural engineering assessment is required when:

• A bridge is being considered for increased loading (heavier vehicles, public transit)
• An OSIM inspection identifies "poor" or "very poor" element conditions requiring engineering follow-up
• A bridge has been struck by an overheight vehicle or experienced an unusual event (flood scour, collision, fire)
• A bridge is approaching or has exceeded its design service life (typically 75 years for CHBDC)
• A municipality is developing a Bridge Asset Management Plan and needs load ratings for all structures

Load ratings in Ontario follow CHBDC CSA S6 Clause 14 (Evaluation of Existing Bridges) using the Load and Resistance Factor Rating (LRFR) method. The rated capacity is expressed in terms of CL-W trucks (CSA S6 CHBDC design truck load).

Ontario Bridge Design Codes & Standards

Governing Agencies for Bridge Work in Ontario

Frequently Asked Questions