IS 1893:2022 Part 6 is the Indian Standard (BIS) for criteria for earthquake resistant design of structures - bridges. This code provides criteria for the earthquake-resistant design and analysis of bridges, viaducts, flyovers, and aqueducts, including the determination of seismic base shear, hydrodynamic forces on submerged piers, and ductile detailing requirements.
Establishes criteria for earthquake resistant design of bridges, covering seismic forces, analysis methods, and detailing requirements.
Quick Reference — IS 1893 Part 6:2022 Bridges
Importance factor, R-values, time-history triggers, vertical seismic, SSI and seat-width requirements for bridges.
| Reference | Value | Clause |
|---|
| Scope | Earthquake-resistant design of bridges (cable-stayed, suspension, arch, special) | Cl. 1 |
| Status | Replaces / supersedes IS 1893 Part 3:2014 for advanced bridges | Foreword |
| Cross-reference (regular bridges) | IRC 6 + IRC 112 + IRC 78 (with seismic clauses) | Cl. 1.2 |
| Importance factor I — strategic bridges | 1.5–1.75 | Cl. 6 (Table) |
| Importance factor I — important bridges | 1.2 | Cl. 6 (Table) |
| Importance factor I — normal bridges | 1.0 | Cl. 6 (Table) |
| Response reduction R — substructure types | 1.0 (elastomeric isolation) to 5.0 (ductile RC pier) | Cl. 7 (Table) |
| Damping — RC bridge superstructure | 5 % | Cl. 5.4 |
| Damping — cable-stayed (cables) | 1–2 % | Cl. 5.4 |
| Time history analysis — required for | Special / irregular / >150 m span / Zone IV–V critical | Cl. 8.2 |
| Vertical seismic component — when included | Long span / cantilever / Zone IV–V | Cl. 6.4 |
| Soil-structure interaction — required for | Soft soil / deep foundations / well foundations | Cl. 9 |
| Liquefaction screening — Zone III–V | Mandatory for sites with loose saturated cohesionless soils | Cl. 10 |
| Min seat width — superstructure (no isolators) | Per Cl. 11 / IRC 6 (function of L, span, zone) | Cl. 11.1 |
| Capacity-design ratio — pier/foundation | Foundation must remain elastic at pier overstrength | Cl. 12 |
⚠ 2022 revision; for routine highway bridges, IRC 6 (with seismic clauses) is normally invoked. Verify section/clause numbering against latest BIS print.
Overview
- Status
- Current
- Usage level
- Specialized
- Domain
- Structural Engineering — Bridges and Bridge Engineering
- Type
- Code of Practice
Also on InfraLens for IS 1893
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Response Reduction Factors (R) for bridges differ significantly from those used for buildings; ensure Part 6 specific values are applied.
! Hydrodynamic forces must be added to inertial seismic forces for bridge piers partially or fully submerged in water.
! Consider vertical seismic forces for bridges with long spans, those located in Zones IV and V, or bridges resting on prestressed concrete components.
Frequently referenced clauses
reinforced concreteprestressed concretesteelcomposite materials
International Equivalents
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International Comparison — Coming Soon
We're adding equivalent international standards for this code.
Key Values6
Quick Reference Values
Zone factor (Z) for Zone V0.36
Zone factor (Z) for Zone IV0.24
Zone factor (Z) for Zone III0.16
Zone factor (Z) for Zone II0.10
Importance factor (I) for critical bridges1.5
Importance factor (I) for normal bridges1.0
Key Formulas
Ah = (Z/2) * (I/R) * (Sa/g) — Design horizontal seismic coefficient
Vb = Ah * W — Design seismic base shear
Tables & Referenced Sections
Key Tables
Table 1 - Seismic Zones and Zone Factors (Z)
Table 2 - Importance Factor (I) for Bridges
Table 3 - Response Reduction Factor (R) for Bridges
Table 4 - Allowable Increase in Safe Bearing Capacity
Key Clauses
Clause 6 - Design Response Spectrum
Clause 7 - Design Seismic Forces
Clause 8 - Hydrodynamic Forces on Piers
Clause 9 - Seismic Analysis of Bridges
Clause 10 - Ductile Detailing Requirements
Frequently Asked Questions3
What is the importance factor for a major highway bridge?+
Critical bridges or major highway bridges typically use an Importance Factor (I) of 1.5.
How is the horizontal seismic coefficient calculated?+
It is calculated using the formula Ah = (Z/2)*(I/R)*(Sa/g).
Are vertical seismic forces mandatory for bridge design?+
Yes, especially for long-span bridges, continuous bridges, and structures located in high seismic zones (Zones IV and V).
QA/QC Inspection Templates
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QA/QC templates coming soon for this code.