Bearings, Expansion Joints and Bridge Appurtenances

Introduction

Bearings, expansion joints and appurtenances are often treated as secondary components because they do not form the principal load-carrying girder or arch. In service, however, they frequently control bridge reliability, riding quality, waterproofing, accessibility and maintenance cost. A structurally adequate superstructure can deteriorate rapidly if movements are restrained, joints leak, drainage is inadequate, barriers are poorly anchored or the approach transition is discontinuous.

This chapter presents a design framework for selecting and checking bearings, movement joints, drainage systems, parapets and barriers, approach slabs, utilities and deck surfacing. Numerical values are illustrative; final design must comply with the governing bridge code, project loading standard, fire requirements and road authority specifications. The designer must distinguish serviceability movements from ultimate actions and must provide a clear load path for every component.

Learning objectives

After studying this chapter, the reader should be able to:

1. Explain bearing types, movement mechanisms and load-transfer requirements.

2. Calculate design movements and carry out preliminary bearing checks.

3. Determine expansion-joint movement capacity and assess joint durability.

4. Design drainage, barriers, approach slabs, utilities and deck surfacing as an integrated system.

5. Apply accessibility, inspection, replacement and maintainability criteria.

6. Critically evaluate common failure modes and develop a coordinated detailing strategy.

1. Design actions and movement compatibility

A bridge support detail must accommodate the design movement envelope rather than a single nominal temperature movement. Relevant actions include:

• uniform temperature change of the superstructure;
• temperature gradients through the deck depth;
• shrinkage and creep of concrete;
• prestress shortening;
• elastic shortening and girder deflection;
• traffic-induced rotation and translation;
• braking, traction, wind and seismic actions;
• settlement or rotation of supports; and
• construction tolerances and bearing installation offsets.

For a prismatic member subjected to a uniform temperature change, the free thermal movement is

ΔL = α L ΔT,

where α is the coefficient of thermal expansion (per °C), L is the relevant expansion length, and ΔT is the design temperature change. The expression applies to free, unrestrained movement; restraint generates force instead of, or in addition to, movement. For a bridge with a fixed point, the expansion length is measured from that point to the expansion joint. Where movement is shared between joints, the structural analysis must establish the movement at each joint.

A practical movement envelope may be expressed as

M_d = γ_m (|M_T| + |M_sh| + |M_cr| + |M_p| + |M_s|) + M_tol,

where the M terms represent thermal, shrinkage, creep, prestress and settlement components, γ_m is the prescribed movement factor or project allowance, and M_tol is the construction-tolerance allowance. This is a design bookkeeping expression, not a substitute for the governing code combination rules. Correlated actions should not be added blindly; the code load combinations and simultaneous-action rules govern.

Worked movement example

A 100 m steel bridge segment expands from a reference temperature by 40°C. Taking α = 10 × 10⁻⁶/°C,

ΔL = (10 × 10⁻⁶)(100)(40) = 0.040 m = 40 mm.

If an additional 8 mm movement allowance is required for shrinkage and installation tolerance, the preliminary joint movement capacity in the relevant direction is at least 48 mm before applying the code-required reserve or movement classification. The joint must also accommodate rotations, vertical displacement, debris exposure and the specified traffic action; therefore a 48 mm translational value alone does not complete the selection.

2. Bearings: function, types and load paths

A bearing transfers vertical reaction and selected horizontal actions while permitting specified translations and rotations. The designer should first prepare a restraint table identifying, at each support, the permitted and restrained degrees of freedom. A typical arrangement has one fixed bearing to establish longitudinal and transverse reference, guided bearings to control transverse movement while permitting longitudinal movement, and free bearings where both horizontal movements are released. Redundant restraint can attract unintended thermal and seismic forces.

Principal bearing types are:

• Elastomeric bearings: laminated rubber and steel sheets accommodate rotation by shear deformation of elastomer layers. They are compact and economical for moderate reactions and movements.
• Pot bearings: an elastomeric disc confined in a pot provides high vertical capacity, while separate sliding and guide elements provide movement and restraint.
• Spherical bearings: a curved sliding surface transfers high reactions and permits rotation; they are appropriate for large loads and rotations.
• Rocker and roller bearings: historically important, but vulnerable to maintenance, alignment and derailment problems unless carefully detailed.
• Sliding bearings: stainless steel against polytetrafluoroethylene (PTFE) or a qualified low-friction material permits translation. They require reliable confinement, cleanliness and inspection access.

Every bearing system requires a continuous load path: deck or girder, sole plate, bearing, masonry or distribution plate, pier or abutment, and foundation. Local concrete compression, splitting, bursting, edge distance, anchor forces and grout performance are as important as the nominal bearing capacity.

2.1 Elastomeric bearing mechanics

An elastomeric bearing is commonly made of alternating elastomer and steel laminates. The steel laminates restrain lateral bulging of the elastomer under compression. Shape factor is defined, for a single internal elastomer layer, as

S = A_loaded / A_free,

where A_loaded is the plan area carrying compression and A_free is the force-free area of the layer available for bulging (normally the perimeter area of the elastomer layer, excluding bonded restraint surfaces). For a rectangular layer of dimensions a and b and thickness t, a commonly used idealization is

S = ab / [2t(a+b)],

provided the layer geometry and code definition are consistent. This is a geometric parameter, not a material strength. Increasing S generally increases vertical compression stiffness and reduces bulging, but may increase sensitivity to imperfections and local stress concentrations.

Bearing checks normally include:

1. Compressive stress: σ_c = V_d/A, where V_d is the design vertical reaction and A is the effective loaded area. The calculated stress must lie within the code limits for the elastomer grade, temperature and load combination.

2. Shear strain from translation: γ_t = Δ_h/t_r, where Δ_h is horizontal displacement and t_r is total elastomer thickness. It must be combined with rotation-induced and other prescribed shear strains according to the code.

3. Rotation: edge effects caused by girder rotation must be checked. A simplified rotation strain estimate is not universally valid; use the bearing standard's rotation model.

4. Stability: the bearing must resist roll-over, excessive bulging and loss of contact. Width-to-height geometry, total elastomer thickness and compressive stress are relevant.

5. Steel laminate thickness and anchorage: laminates resist internal tension and distribute compression; external plates and anchors transfer horizontal and uplift actions where applicable.

6. Serviceability and durability: ozone, ultraviolet exposure, temperature, chemical attack, fatigue, contamination and replacement access must be considered.

Worked preliminary elastomeric check

Suppose a laminated bearing carries a service reaction of 1,200 kN over a 300 mm × 400 mm plan area. The mean compression is

A = 0.300 × 0.400 = 0.120 m²,

σ_c = 1,200/0.120 = 10,000 kN/m² = 10 MPa.

If the total elastomer thickness is 60 mm and the calculated longitudinal movement is 18 mm, the translation shear strain is

γ_t = 18/60 = 0.30.

These values are only preliminary checks. Acceptance requires comparison with the applicable bearing code, including simultaneous rotation, temperature, vertical load range, shear limits, stability and reinforcement details. It would be unsafe to declare the bearing adequate from these two calculations alone.

2.2 Sliding and guided bearings

Sliding bearings should be selected using the design reaction, movement, rotation, friction coefficient, wear life and environmental exposure. Friction produces a horizontal action approximately equal to

H_f = μ V,

for a sliding interface under a simplified constant-friction model, where μ is the relevant design friction coefficient and V is the normal reaction. Actual μ depends on pressure, temperature, speed, lubrication, surface condition and material pair; code values or certified test data must be used. The force must be included in pier, diaphragm, anchor and bearing-plate design. PTFE systems also require adequate contact pressure and prevention of extrusion.

Bearings should be replaceable without uncontrolled jacking of the bridge. Provide jacking points, verified lifting reactions, access, safe working space, removable obstacles and a replacement sequence. Bearing inspection should be possible without entering unsafe confined spaces.

3. Expansion joints

An expansion joint closes the roadway gap while accommodating relative movement. Common systems include compression seals, strip seals, modular joints, finger joints and buried or jointless transitions. Selection depends on movement range, traffic speed, skew, rotation, drainage, noise, maintenance access and expected debris accumulation.

3.1 Joint sizing

The joint movement capacity must exceed the maximum relative movement in every relevant direction. A conceptual design requirement is

C_req ≥ M_max − M_min + T_res,

where M_max and M_min are the extreme relative positions over the design temperature and deformation envelope, and T_res is the prescribed reserve for tolerance, installation and uncertainty. If the joint is installed at a temperature different from the reference temperature, its initial opening must be calculated explicitly. A joint specified only by nominal gap width is inadequate.

For the worked bridge above, the thermal range is 40 mm. Adding 8 mm of specified nonthermal movement gives 48 mm peak-to-peak preliminary demand. If the manufacturer requires 10% reserve, a nominal capacity not less than 52.8 mm would be needed, subject to rounding upward to the next certified joint size. This does not authorize using 52.8 mm as a final selection: rotation, skew amplification, vertical movement, braking, fatigue and the code's movement classification must be checked.

Skewed bridges require special attention. The movement normal to the joint is not necessarily equal to the longitudinal deck movement, and differential transverse movement can distort seals. Joint anchorage must be designed for traffic impact, fatigue, local concrete breakout and reinforcement congestion. The joint interface must be waterproof, with a positive drainage path that does not discharge onto bearings or substructure faces.

3.2 Joint failure and detailing

Typical failures include seal tearing, anchor loosening, concrete spalling, blocked drainage, noisy impact, leakage and loss of skid resistance. Good detailing provides a replaceable seal, robust edge beams, adequate confinement, smooth approach geometry, corrosion-resistant fixings, access for cleaning and a documented inspection interval. Where movement and durability permit, joint minimization or integral construction can remove a major leakage source, but it transfers movement and restraint demands to the abutment and approach system.

4. Bridge drainage and waterproofing

Water is a primary deterioration agent. Deck drainage should prevent standing water, hydroplaning, chloride transport and discharge over bearings, expansion joints, traffic lanes, pedestrians or environmentally sensitive areas.

The drainage design must identify the contributing catchment, longitudinal and crossfall gradients, inlet spacing, hydraulic capacity, blockage allowance, outlet routing and maintenance access. A preliminary peak flow can be estimated by the Rational Method,

Q = C i A,

where Q is peak runoff, C is runoff coefficient, i is design rainfall intensity consistent with the catchment time of concentration, and A is catchment area. Units must be consistent; for example, if i is in m/s and A in m², Q is in m³/s. The method is suitable for small, reasonably homogeneous urban catchments and does not replace the bridge authority's hydraulic criteria.

For a 150 m² deck catchment, C = 0.90 and i = 80 mm/h = 0.00002222 m/s,

Q = 0.90(0.00002222)(150) = 0.00300 m³/s,

or approximately 3.0 L/s. Inlet and pipe capacity must exceed the design flow with blockage and surcharge considerations. Longitudinal drainage should not rely on an assumed perfectly smooth surface; construction tolerances and settlement must be allowed for.

Deck waterproofing should be compatible with concrete moisture, surfacing materials, temperature, joint details and repair procedures. Drains need grates safe for bicycles and pedestrians, corrosion-resistant components, cleanouts and outlets that can be inspected. Scuppers discharging onto bearings are unacceptable. Downpipes should be secured against vibration and should not create an impact hazard or uncontrolled erosion at the foundation.

5. Parapets, barriers and pedestrian protection

A parapet or traffic barrier is a safety-critical restraint system, not merely an edge finish. Its design comprises the vehicle-redirection system, posts or anchorage, deck edge, reinforcement, transitions and terminals. The required performance level, containment, deflection, working width, vehicle class and test or code acceptance must be established before proportioning.

Barrier actions arise from prescribed collision loads, rail impact, concentrated handrail loads, wind, crowd loading where relevant and accidental actions. A simplified local design check may represent a barrier post or rail as a beam subject to a design lateral force P at lever arm h:

M = P h.

This is only a statics illustration; the governing barrier standard may require dynamic test qualification, load distribution, anchorage design and capacity design. The deck edge must resist flexure, shear, punching, splitting and longitudinal load transfer. Reinforcement should be developed beyond the assumed failure region, and discontinuities at joints must not create unprotected gaps.

Vehicle barriers and pedestrian parapets have different functional requirements. A pedestrian railing may satisfy height and opening limits but be incapable of containing a vehicle. A combined system must preserve a continuous pedestrian handrail, prevent climbing or trapping hazards where required, and maintain the tested performance of the traffic barrier. Transitions to roadway barriers and end terminals are particularly important because abrupt stiffness changes can increase collision severity.

6. Accessibility and pedestrian continuity

Accessibility is a geometric and operational design requirement. It must be coordinated with the applicable accessibility legislation and road authority standard. As practical checks, the designer should document:

• clear accessible width, measured between obstructions and not merely between nominal rails;
• longitudinal gradient and crossfall, with maximum values taken from the governing accessibility standard;
• a firm, stable, slip-resistant and continuous surface;
• level or appropriately detailed transitions at joints and approach slabs;
• edge protection where a wheel could leave the path;
• handrails, kerbs and detectable warnings where required;
• openings small enough to prevent wheel or cane entrapment;
• maximum vertical lips at covers and joints;
• turning, passing and resting spaces for the intended route; and
• lighting, sight distance and protection from splash.

As an illustrative—not universal—criterion, a project may specify a 1.5 m clear pedestrian path, crossfall no greater than 2%, and a maximum longitudinal gradient of 5% for a route intended to be independently accessible. A 1:12 ramp (8.33%) may be permitted in some standards only for limited rises and with level landings; it should not be treated as a universal bridge criterion. The controlling jurisdiction must be stated on drawings. If a joint crosses an accessible path, its cover must be flush, securely fixed and oriented so that the opening does not trap mobility-device wheels. A design review should use an actual wheelchair and visually impaired-user route assessment rather than relying solely on nominal dimensions.

7. Approach slabs and transition zones

Approach slabs reduce the abrupt change from embankment to abutment and distribute wheel loads across a potentially settling zone. They do not eliminate settlement; they provide a controlled transition and can be connected to the abutment, supported independently, or detailed as a flexible transition according to the ground and drainage strategy.

Design inputs include expected differential settlement, slab span and support conditions, traffic loading, soil reaction, backfill quality, abutment movement, drainage and construction sequence. A conservative preliminary model may treat a simply supported one-metre-wide strip under uniform factored load w as

M = wL²/8,

where L is the effective span. This formula applies only to a simply supported strip under uniform load; continuous, elastic-foundation and soil-structure models require different analysis. The final design should consider wheel-load dispersion, punching or local bending, crack control, reinforcement anchorage and fatigue where relevant.

Worked approach-slab application

Consider a 6 m long approach slab, designed initially as a simply supported strip of unit width, with factored uniform load w = 35 kN/m. The idealized moment is

M = 35(6²)/8 = 157.5 kN·m per metre width.

If the effective depth is 300 mm and a simplified lever arm z = 0.9d = 270 mm is used, the required tensile steel from the flexural equilibrium approximation is

A_s = M/(f_yd z).

For f_yd = 435 N/mm², M = 157.5 × 10⁶ N·mm and z = 270 mm,

A_s = 157.5 × 10⁶/(435 × 270) = 1,342 mm²/m.

This is a preliminary flexural quantity only. Minimum reinforcement, crack control, top reinforcement, transverse distribution, anchorage, shear, fatigue, bearing pressure and the actual soil-support model may govern. The example demonstrates why an approach slab should not be proportioned solely by nominal thickness.

Drainage behind the abutment is essential. Filter-compatible backfill, geocomposites, outlets and protection against erosion reduce hydrostatic pressure and loss of support. Construction tolerances and staged embankment settlement should be included in the transition strategy.

8. Utilities, deck surfacing and interfaces

Utilities may include water, gas, electricity, telecommunications and drainage services. The preferred arrangement is usually outside the primary structural waterproofing zone and accessible without cutting prestressing tendons or major reinforcement. Utility supports must accommodate thermal movement, vibration, seismic displacement, fire separation and differential movement at joints. Pipes crossing a joint require flexible couplings or a deliberately designed movement loop. Utility attachments must not obstruct bearing replacement, drains, inspection paths or emergency access.

A utility coordination drawing should show ownership, isolation points, support reactions, clearances, fire and electrical separation, corrosion protection and the consequence of leakage. Embedding an unverified service in a girder or deck is poor practice because later replacement may require destructive work.

Deck surfacing must provide skid resistance, waterproof protection, ride quality and compatibility with joint and drain levels. The designer should control surface regularity, texture, crossfall, bond, permeability, rutting, thermal cracking and repairability. The surfacing thickness is a permanent load and should be included in dead-load reactions and bearing design. At an expansion joint, the surfacing termination must not bridge the movement gap or create a step. Materials should be selected for the expected climate, de-icing salts, ultraviolet exposure and maintenance regime.

9. Integrated inspection and maintenance strategy

The detail should be designed around its future inspection tasks. Provide visual access to bearing edges, anchor plates, joint seals, drain outlets and barrier anchors. Record bearing type, orientation, installation temperature, preset, level tolerances, material certificates and jacking points. Establish inspection triggers after abnormal events such as flooding, collision, earthquake or unusual noise.

Common symptoms and likely causes include:

• leaking joints: failed seal, blocked drain or inadequate waterproofing;
• displaced elastomer: excessive shear, rotation, installation error or instability;
• deck-edge cracking: inadequate anchorage, impact or restraint;
• approach bump: settlement, poor compaction or failed transition detail; and
• ponding: insufficient gradient, construction tolerance or blocked inlet.

Repairability is a design criterion. A cheap component that requires lane closure, heavy lifting and destructive access may have a higher life-cycle cost than a more durable replaceable system. Life-cycle evaluation should include initial cost, inspection, traffic management, replacement frequency, environmental consequences and user risk.

10. Illustrative integrated case study

Background. An illustrative two-span urban bridge has a fixed bearing over the central pier, guided bearings at one abutment and an expansion joint at the opposite abutment. A shared cycle-and-pedestrian path crosses the deck. The bridge is exposed to de-icing salt and intense short-duration rainfall.

Problem. Inspection found joint leakage, corrosion at a drain outlet, a 20 mm step at the approach, and a narrow path partly obstructed by utility brackets. The original drawings did not record bearing installation temperature or replacement jacking points.

Analysis. The design team reconstructed the restraint system and calculated 40 mm thermal movement over the expansion length, plus 8 mm nonthermal allowance. The joint was therefore assessed for at least 48 mm preliminary peak-to-peak movement, with additional code reserve and rotation checks. Drainage calculations gave a 3.0 L/s design flow for the representative catchment; the existing blocked outlet had insufficient maintenance access. A barrier inspection showed that the transition to the roadway barrier was not performance-compatible. The path provided only 1.25 m clear width and a 3% crossfall, conflicting with the adopted accessibility brief.

Approach and solution. The joint was replaced with a certified movement system whose capacity included the calculated movement, skew and rotation. A flexible waterproof drainage trough was connected to accessible downpipes discharging away from the bearings. The approach slab and compacted, drained backfill were reconstructed, with a level transition and controlled settlement monitoring. Utility brackets were relocated outside the clear path, the path was widened to 1.5 m, crossfall reduced to 2%, and joint covers were made flush. Barrier transitions and deck-edge reinforcement were redesigned to the required containment standard. Jacking points, bearing identification plates and an inspection schedule were added.

Outcome. The intervention removed direct water discharge onto the substructure, restored accessible continuity and provided a documented replacement method. The principal lesson is that the joint, drain, bearing, approach slab, barrier and path cannot be repaired independently: movement and water management must be coordinated at the system level.

11. Limitations, regulation and contemporary practice

Prescriptive dimensions cannot replace project-specific analysis. Climate change may increase rainfall intensity, thermal range and deterioration rates; updated climate data and robustness allowances may therefore be required. Digital inspection using unmanned aerial systems, photogrammetry, sensors and machine-learning image classification can assist prioritization, but automated defect recognition requires validated data and human engineering review. Digital twins are useful only when component identity, inspection history and movement measurements are maintained.

Regulatory compliance includes structural design codes, traffic barrier acceptance requirements, accessibility law, occupational safety rules, environmental discharge permits and utility-owner requirements. Ethical practice requires transparent assumptions, traceable calculations, competent review and refusal to conceal defects or substitute unverified products. Proprietary systems should be specified by performance and certification, not by unsupported brand preference.

Best-practice design sequence

1. Establish the governing codes, design life, environment and accessibility brief.

2. Map all translational and rotational degrees of freedom.

3. Calculate movement envelopes and installation presets.

4. Select bearings and joints as a compatible restraint system.

5. Check local load transfer, anchorage and replaceability.

6. Design waterproofing and drainage before finalizing edge details.

7. Design barriers, transitions and pedestrian protection as tested systems.

8. Analyze approach slabs with realistic settlement and support assumptions.

9. Coordinate utilities, surfacing, inspection access and construction sequence.

10. Complete a maintainability, accessibility and life-cycle review.

Chapter Summary

Bearings transfer bridge reactions while releasing specified movements and rotations; their design requires a complete restraint table, local load-transfer checks, stability, durability and replacement planning. Thermal movement is only one component of the movement envelope. Expansion joints must be selected for peak-to-peak movement, rotation, skew, vertical action, waterproofing and fatigue, not merely nominal gap width. Drainage and waterproofing protect bearings, concrete and users, while barriers require performance-compatible containment, anchorage and transitions. Approach slabs manage, but do not eliminate, settlement and must be designed with realistic support assumptions. Utilities and deck surfacing must accommodate movement and remain maintainable. Accessibility requires measurable width, gradient, crossfall, flush joints, edge protection and continuous safe routing. The reliable bridge is therefore an integrated system designed for movement, water, safety, inspection and replacement throughout its life.

Key Terms

Bearing: Component transferring bridge reactions while permitting specified movement or rotation.

Fixed bearing: Bearing that restrains defined translations and establishes a reference point.

Guided bearing: Bearing that permits movement in one direction while restraining another.

Elastomeric bearing: Laminated rubber-and-steel bearing accommodating movement through elastomer shear.

Shape factor: Ratio of loaded plan area to force-free bulging area of an elastomer layer.

Sliding bearing: Bearing using a low-friction interface to permit translation.

Expansion joint: Device closing a structural gap while accommodating relative movement.

Movement envelope: Range of relative displacement and rotation requiring accommodation.

Preset: Intentional installation adjustment allowing for the position at a specified temperature or stage.

Waterproofing: Layer or system preventing water penetration into the deck and structural elements.

Scupper: Deck drainage opening or outlet.

Barrier: Vehicle-restraint system designed to redirect or contain an impacting vehicle.

Parapet: Edge railing or barrier protecting vehicles or pedestrians.

Approach slab: Slab forming a transition between roadway embankment and bridge abutment.

Crossfall: Transverse slope of a deck or path for drainage.

Clear width: Usable path width excluding rails, signs, utilities and other obstructions.

Life-cycle cost: Total cost of construction, operation, maintenance, replacement and disposal.

Jacking point: Designed location for safely lifting a bridge during bearing replacement.

Shape factor: Geometric ratio governing elastomer-layer bulging behavior under compression.

Review Questions

Short Answer Questions

1. What functions does a bridge bearing perform?

2. Why must expansion-joint capacity include rotation and skew effects?

3. Define elastomeric-bearing shape factor.

4. State two consequences of discharging deck water onto bearings.

5. Why are approach slabs not a complete solution to embankment settlement?

Long Answer Questions

1. Explain the selection and design checks for an elastomeric bearing system.

2. Discuss the movement, durability and maintainability requirements of expansion joints.

3. Develop an integrated bridge drainage and waterproofing strategy.

4. Explain the design relationship between vehicle barriers, pedestrian parapets and deck-edge reinforcement.

5. Discuss how accessibility, utilities and surfacing should influence bridge-edge detailing.

Analytical / Application Questions

1. A 120 m expansion length has α = 11 × 10⁻⁶/°C and a design temperature range of 55°C. Calculate free thermal movement and identify additional information needed before selecting a joint.

2. A bearing carries 1,500 kN over a 350 mm × 450 mm area, with 75 mm total elastomer thickness and 15 mm translation. Calculate mean compression and translation shear strain, then explain why these do not constitute a complete bearing check.

3. A 200 m² deck catchment has C = 0.85 and rainfall intensity 90 mm/h. Calculate Rational-Method peak flow in L/s and propose design checks for the inlet and outlet system.

Multiple Choice Questions with Answers

Question 1

A 100 m bridge has α = 10 × 10⁻⁶/°C and undergoes a uniform 40°C temperature increase. What is its free thermal movement?

A. 4 mm

B. 20 mm

C. ายน 4 m

D. 40 mm

Correct Answer: D. 40 mm

Question 2

For an elastomeric bearing layer, shape factor most appropriately relates:

A. Loaded plan area to force-free bulging area

B. Steel thickness to total bearing thickness

C. Horizontal load to vertical load

D. Rotation to temperature change

Correct Answer: A. Loaded plan area to force-free bulging area

Question 3

A 300 mm × 400 mm bearing carries 1,200 kN. Its mean compressive stress is:

A. 1 MPa

B. 10 MPa

C. 100 MPa

D. 0.10 MPa

Correct Answer: B. 10 MPa

Question 4

An elastomeric bearing has 60 mm total elastomer thickness and undergoes 18 mm translation. The translation shear strain is:

A. 0.03

B. 0.18

C. 0.30

D. 3.33

Correct Answer: C. 0.30

Question 5

For a sliding bearing under a simplified constant-friction model, friction force is approximately:

A. V/μ

B. μV

C. μ/V

D. V + μ

Correct Answer: B. μV

Question 6

A 150 m² deck catchment has C = 0.90 and rainfall intensity 80 mm/h. The Rational-Method flow is approximately:

A. 0.30 L/s

B. 3.0 L/s

C. 30 L/s

D. 300 L/s

Correct Answer: B. 3.0 L/s

Question 7

Which statement best describes a traffic barrier design?

A. It is only a decorative edge railing

B. It can be designed without considering the deck edge

C. It requires performance-compatible containment, anchorage and transitions

D. Its height alone determines its adequacy

Correct Answer: C. It requires performance-compatible containment, anchorage and transitions

Question 8

Which accessibility feature is most directly intended to prevent mobility-device wheels catching at a deck joint?

A. A flush, securely fixed joint cover

B. A higher kerb at the joint

C. A roughened vertical lip

D. An unprotected drainage slot

Correct Answer: A. A flush, securely fixed joint cover

Question 9

For a simply supported one-metre-wide strip under uniform load w, the idealized bending moment used in the chapter is:

A. wL/2

B. wL²/2

C. wL²/8

D. w/L²

Correct Answer: C. wL²/8

Question 10

Which provision most directly supports future bearing replacement?

A. Eliminating all inspection records

B. Providing designed jacking points and verified lifting reactions

C. Embedding utilities through the bearing

D. Discharging drainage onto the bearing

Correct Answer: B. Providing designed jacking points and verified lifting reactions