Earthquake-resistant design

In short

Earthquake-resistant design is the practice of proportioning and detailing a structure so that it survives ground shaking without collapse, using code-specified inertia forces instead of a measured load. In India the governing documents are IS 1893 (Part 1): 2016 for criteria and loads, IS 13920: 2016 for ductile detailing of RC members, IS 4326 / IS 13828 / IS 13827 for masonry and earthen construction, and Part 6 of the National Building Code 2016. The philosophy is not "no damage" but graded performance — no damage in minor shaking, no structural damage in moderate shaking, and no collapse in the strongest shaking expected at the site. It carries 5–10 marks in GATE Civil and is a standing topic in design interviews at L&T, Tata Projects, AECOM, Jacobs, Afcons and every structural consultancy, because almost 59% of India's land area is in Zones III to V.

Explained

Ground motion, hazard and the Indian zone map

• An earthquake releases strain energy at a focus; the point vertically above it on the surface is the epicentre. Body waves (P — longitudinal, fastest; S — transverse, more damaging) are followed by surface waves (Love, Rayleigh).
• Magnitude (Richter, moment magnitude Mw) measures energy released — one number per event; intensity (MSK/MMI scale, I–XII) measures observed shaking and damage — varies from place to place.
• Design inputs are PGA (peak ground acceleration, as a fraction of g), duration and frequency content. Soft soil amplifies long-period motion; this is why spectra differ by soil type.
• IS 1893 (Part 1): 2016 maps India into four zones — II (Z = 0.10), III (Z = 0.16), IV (Z = 0.24), V (Z = 0.36). Old Zone I was merged into II in the 2002 revision.
• Typical classification: Zone V — Kutch (Bhuj), the North-East, Andaman & Nicobar, parts of Uttarakhand, Himachal and J&K; Zone IV — Delhi, Patna, Dehradun, Jammu; Zone III — Mumbai, Chennai, Kolkata, Ahmedabad, Pune; Zone II — Bengaluru, Hyderabad, Nagpur.
• Z is the effective peak ground acceleration for the Maximum Considered Earthquake (MCE). The Design Basis Earthquake (DBE) is taken as half of it — hence the factor Z/2 in the base shear formula.
• Other parts of the code: Part 2 — liquid-retaining tanks; Part 3 — bridges and retaining walls; Part 4 — industrial structures and stack-like structures.

Design philosophy, seismic weight and load combinations

• Four virtues of an earthquake-resistant building: good configuration, adequate lateral strength, sufficient lateral stiffness and above all ductility (ability to deform inelastically without losing strength).
• Structures are deliberately designed for forces far smaller than elastic demand; the shortfall is absorbed by ductility and overstrength, accounted for by the response reduction factor R.
• Seismic weight W = full dead load + part of imposed load: 25% of imposed load if IL ≤ 3 kN/m², 50% if IL > 3 kN/m². Imposed load on the roof is not included. Live load on inclined/sloping surfaces is excluded; weight of water in tanks and permanent equipment is included.
• Importance factor I (Table 8): 1.5 for hospitals, schools, fire/police stations, power stations, monuments and other critical and lifeline structures; 1.2 for buildings with occupancy above 200 persons; 1.0 otherwise.
• Response reduction factor R (Table 9): unreinforced load-bearing masonry 1.5; masonry with horizontal RC bands 2.5; masonry with bands plus vertical bars at corners 3.0; ordinary RC moment frame (OMRF) 3.0; special RC moment frame (SMRF) 5.0; ordinary RC shear wall 3.0; ductile shear wall 4.0; ductile shear wall with SMRF (dual system) 5.0; steel frame with concentric braces 4.0, with eccentric braces 5.0. A high R is permitted only if the detailing of IS 13920 (or IS 800 plastic/ductile provisions) is actually provided.
• Vertical seismic coefficient Av = (2/3) × Ah — required for cantilevers, large spans, pre-stressed and horizontally projecting elements.
• Limit-state combinations (IS 1893 Cl 6.3.1.2, with EL = DBE effect): 1.2(DL + IL ± EL); 1.5(DL ± EL); 0.9 DL ± 1.5 EL (this last one governs uplift in footings and tension in columns and must never be dropped).
• Earthquake and wind are not combined; design for the worse of the two. Earthquake forces act along each principal direction separately; for buildings with irregular/non-parallel systems, 100% in one direction plus 30% in the orthogonal direction is used.

Methods of analysis

1. Equivalent static (seismic coefficient) method — permitted for regular buildings up to 15 m in Zones II and III, and generally for low-rise regular buildings; base shear Vb = Ah·W distributed over height in proportion to Wi·hi².
2. Linear dynamic analysis — mandatory for tall or irregular buildings (IS 1893: 2016 Cl 7.7 requires dynamic analysis for buildings taller than 15 m in Zones IV–V and for all irregular buildings):
   • Response spectrum method (modal analysis): 3D model, eigenvalue solution, modal mass and modal participation factors, enough modes to capture at least 90% of the total seismic mass, responses combined by SRSS (well-separated modes) or CQC (closely spaced modes).
   • Scaling rule: if the dynamic base shear is less than the base shear from the empirical-period static method, all response quantities are scaled up by the ratio. The dynamic result is never scaled down.
   • Time-history (response-history) analysis: direct integration with at least three (preferably seven) spectrum-compatible accelerograms — used for isolated, irregular, or very important structures.
3. Nonlinear static (pushover) analysis — monotonically increasing lateral load against a capacity curve; used for performance-based assessment and retrofit design (not a design method in IS 1893, but standard practice following ATC-40/FEMA 356).
4. Fundamental period Ta (Cl 7.6): bare RC moment frame Ta = 0.075 h^0.75; composite 0.080 h^0.75; steel moment frame 0.085 h^0.75; for all other buildings including RC frames with masonry infill Ta = 0.09 h/√d. Buildings with RC structural walls have a separate expression using the effective wall area. Infill stiffens a frame and shortens its period, which usually increases the design force.
5. Design spectrum (5% damping, Fig. 2 / Cl 6.4.2): Sa/g rises as 1 + 15T up to T = 0.10 s, stays at the plateau 2.50, then decays as 1.00/T (Type I rock/hard soil, from 0.40 s), 1.36/T (Type II medium soil, from 0.55 s) or 1.67/T (Type III soft soil, from 0.67 s), up to 4 s. Damping multipliers (Table 3) apply only in response spectrum/dynamic analysis — e.g. 1.40 for 2% and 0.80 for 10% damping.

Configuration, irregularities and drift control

• Simple, symmetric, compact plans with a continuous load path behave best. Every irregularity concentrates damage.
• Plan irregularities (Table 5): torsional irregularity (max storey drift at one end > 1.5 × min; ratios above 2.0 are not permitted in Zones III–V), re-entrant corners (projection > 15% of plan dimension), diaphragm discontinuity (cut-out > 50% of area), out-of-plane offsets of vertical elements, non-parallel lateral systems.
• Vertical irregularities (Table 6): soft storey (stiffness < 70% of the storey above, or < 80% of the average of three above), weak storey (strength < 80% of the storey above), mass irregularity (> 150% of adjacent storey), geometric irregularity (horizontal dimension > 125% of adjacent storey), in-plane discontinuity in vertical elements.
• Open ground storey (stilt parking) is the single most common cause of collapse of Indian RC buildings. IS 1893: 2016 treats it as a severe irregularity: the preferred remedy is to remove the irregularity by adding RC shear walls or braces in the ground storey, backed by dynamic analysis. (The 2002 code's blunt rule of designing ground-storey members for 2.5 times the computed shear was modified in the 2016 revision; check the current edition and amendments before applying either version.)
• Short-column effect: stiff short columns (e.g. at plinth beams, mezzanines, sloping sites) attract large shear and fail brittlely — detail them with closely spaced confinement over the full height.
• Floating/hanging column — a column resting on a beam, not continuous to the foundation. It breaks the load path, is a vertical discontinuity, and must be avoided or justified by explicit dynamic analysis.
• Storey drift limit (Cl 7.11.1): drift under the design lateral force, with partial load factor 1.0, ≤ 0.004 × storey height.
• Separation between adjacent buildings (Cl 7.11.3): gap ≥ R times the sum of the computed storey displacements, to prevent pounding; equal-height, equal-floor-level buildings may use half this.
• Torsion (Cl 7.8.2): design eccentricity edi = 1.5 esi + 0.05 bi or esi − 0.05 bi, whichever gives the worse effect in the element; the 0.05 bi term covers accidental eccentricity.
• Infill walls may be modelled as equivalent diagonal struts (Cl 7.9) with a width given by the code's empirical expression; unreinforced infill must then be checked for in-plane and out-of-plane demand.

Ductile detailing of RC — IS 13920: 2016

• Capacity design principle: choose where the structure will yield (beam ends), ensure those regions are ductile, and make everything else — columns, joints, shear — strong enough to never fail first. Hence "strong column – weak beam" and "flexure before shear".
• Applicability: all RC frames and walls resisting lateral load in Zones III, IV and V, and for important/irregular structures in Zone II. Concrete ≥ M20 (M25 for buildings above 15 m); steel must be Fe415 or lower grade, or Fe500/Fe550 of grade D (controlled elongation and yield ratio).
• Beams: width ≥ 200 mm; b/D ≥ 0.3; clear span/D ≥ 4. Longitudinal steel ratio ≥ 0.24√fck/fy and ≤ 0.025; at least two bars continuous top and bottom through the span; sagging capacity at a joint face ≥ 50% of hogging capacity. Hoops ≥ 8 mm dia (6 mm allowed for clear span ≤ 5 m), spaced ≤ min(d/4, 8 × smallest bar dia) but not less than 100 mm over a length 2d from each joint face, and ≤ d/2 elsewhere. Closed hoops with 135° hooks and 10 dia (≥ 75 mm) extensions — never 90° hooks, which open out.
• Columns: minimum dimension 300 mm (or 20 × largest beam bar dia passing through); shorter/longer side ratio ≥ 0.45; a member with factored axial stress > 0.08 fck is designed as a column. Special confining reinforcement over length lo = max(larger lateral dimension, clear span/6, 450 mm) at each end, through the joint, and over the full height of columns supporting discontinuous walls. Spacing ≤ min(min dimension/4, 6 × smallest longitudinal bar dia), 75–100 mm. Lap splices only in the middle half, with hoops at ≤ 150 mm, and ≤ 50% bars spliced at a section.
• Strong column – weak beam: at every joint, ΣMc ≥ 1.4 ΣMb (sum of column design moment capacities ≥ 1.4 × sum of beam capacities), checked in both directions and both senses of sway. Exempt only for the top storey and for frames whose lateral resistance comes from walls.
• Design shear from capacity, not from analysis: beam shear uses plastic hinge moments at both ends; column shear uses the capacities of the beams framing into it. Bending-shear contribution of concrete is ignored where axial force is small and shear reversal occurs.
• Beam-column joints: column confining hoops continued through the joint; joint shear checked; wide-beam and eccentric joints need special treatment; anchorage of beam bars into exterior joints with standard 90° bends inside the confined core.
• Shear walls: thickness ≥ 150 mm (≥ 200 mm for coupled walls in Zones IV and V); reinforcement ≥ 0.25% of gross area in each direction, spacing ≤ min(lw/5, 3t, 450 mm); two curtains mandatory if thickness > 200 mm or factored shear stress > 0.25√fck; boundary elements at the ends to carry the flexural couple, confined like columns; coupling beams diagonally reinforced when the span/depth ratio is small.

Masonry, foundations, soil effects and advanced systems

• Masonry (IS 4326, IS 13828 for low-strength masonry, IS 13827 for earthen houses): continuous horizontal RC bands at plinth, sill, lintel, roof/eaves and gable level; vertical reinforcement at corners, T-junctions and around openings; limits on opening size and position; through-stones or bond elements in stone masonry; light roof, well tied down. These, not strength, are what keep load-bearing masonry standing.
• Foundations: avoid mixed foundation types under one block; tie isolated footings with plinth beams/tie beams; check uplift under 0.9 DL ± 1.5 EL; raft or piles on poor soil.
• Liquefaction: saturated loose sand loses strength under cyclic shear (Bhuj 2001, Bihar 1934). IS 1893: 2016 Annex F gives the simplified SPT/CPT-based procedure comparing cyclic stress ratio with cyclic resistance ratio; mitigation by ground improvement (vibro-compaction, stone columns), deep foundations or dewatering. The code requires a liquefaction check for sites in Zones III–V with loose saturated sand and shallow water table.
• Site classification into Type I (rock/hard soil), II (medium, N = 10–30) and III (soft, N < 10) selects the spectrum; building on or spanning across an active fault is prohibited.
• Base isolation: lead-rubber, high-damping rubber or friction-pendulum bearings shift the period to 2–3 s, away from the dominant ground period, cutting superstructure acceleration at the cost of large bearing displacement. Best for stiff, low-to-medium-rise, important buildings on firm soil; poor on soft soil and for tall flexible frames.
• Supplemental damping: fluid viscous dampers, friction dampers, yielding/ADAS metallic dampers, visco-elastic dampers and tuned mass dampers (for wind and seismic comfort in tall buildings).
• Retrofitting: jacketing of columns (RC, steel or FRP), adding shear walls/bracing, infilling selected bays, FRP wrapping, base isolation of heritage structures, and strengthening of masonry by splints, bandages and ferrocement overlays — guided by IS 13935.
• Regulatory frame: NBC 2016 Part 6; the Disaster Management Act 2005 and NDMA guidelines; municipal bye-laws requiring structural design certification and, in many states, third-party proof-checking of high-rise designs.

Key points

• Z - zone factor = MCE effective PGA/g; 0.10, 0.16, 0.24, 0.36 for Zones II–V; the Z/2 in the formula converts MCE to DBE.
• I - importance factor, 1.0 / 1.2 / 1.5; raises the force on buildings whose failure is unacceptable.
• R - response reduction factor; credit for ductility and overstrength, earned only by providing IS 13920 detailing.
• Sa/g - spectral acceleration coefficient from the design spectrum; plateau value 2.50 for all three soil types at 5% damping.
• Seismic weight - full DL + 25% IL (IL ≤ 3 kN/m²) or 50% IL (IL > 3 kN/m²); no roof live load.
• Vertical distribution - lateral force at a floor ∝ Wi·hi², so the top floors attract the most force.
• Drift limit - 0.004 × storey height under design lateral force with load factor 1.0.
• Design eccentricity - edi = 1.5 esi + 0.05 bi or esi − 0.05 bi, whichever is worse.
• Soft/open ground storey - stiffness below 70% of the storey above; India's commonest collapse mechanism; cure it with walls or braces, not bigger columns alone.
• Strong column–weak beam - ΣMc ≥ 1.4 ΣMb at every joint; prevents a storey-sway (column-hinge) mechanism.
• Capacity design shear - members are designed for the shear that develops when plastic hinges reach capacity, not for analysis shear.
• Special confining reinforcement - closely spaced closed hoops with 135° hooks over lo at column ends; the difference between a ductile column and a brittle one.
• Short column and floating column - stiffness/load-path defects that attract or interrupt force; avoid or detail specially.
• Pounding - collision of adjacent buildings; prevented by a separation of R × sum of storey displacements.
• Liquefaction - strength loss in saturated loose sand; checked by the simplified method in Annex F of IS 1893: 2016.
• Base isolation and dampers - period shift and energy dissipation; reduce demand instead of adding strength.
• Ductility over strength - a strong brittle building fails worse than a slightly weaker ductile one; energy must be dissipated, not stored.
• Load combination 0.9 DL ± 1.5 EL - governs overturning, footing uplift and column tension.

Formulas and examples

Example 1 — Seismic weight, base shear and distribution (5-storey RC SMRF). Building 20 m × 15 m in plan, 5 storeys of 3.30 m (h = 16.5 m), Zone IV, medium soil, brick infill, residential (I = 1.0), SMRF with IS 13920 detailing (R = 5.0).

• *Typical floor seismic weight:* slab 150 mm = 3.75, finishes 1.00, partitions 1.00, beams 1.50, columns 0.75, external walls 1.25 → DL = 9.25 kN/m²; imposed 3.0 kN/m² → 25% = 0.75 kN/m². Total 10.0 kN/m² × 300 m² = 3000 kN.
• *Roof:* slab 3.75 + waterproofing/finish 2.00 + beams 1.50 + half-height columns 0.375 + parapet 0.375 = 8.0 kN/m² (roof live load excluded) × 300 = 2400 kN.
• W = 4 × 3000 + 2400 = 14 400 kN.
• Period (infilled frame, shaking along the 15 m direction so d = 15 m... take the critical 20 m direction, d = 20 m): Ta = 0.09 × 16.5 / √20 = 1.485/4.472 = 0.332 s → on the plateau for medium soil (0.10–0.55 s) → Sa/g = 2.50.
• Ah = (0.24/2) × 2.50 / (5/1.0) = 0.12 × 0.50 = 0.06.
• Vb = 0.06 × 14 400 = 864 kN.

Example 2 — Effect of zone and of detailing (same building, Sa/g = 2.50, I = 1.0).

Ductile detailing to IS 13920 lets the same Zone IV building be designed for 864 kN instead of 1440 kN — 40% less force, for the cost of better hoops.

Example 3 — Torsion and drift check (building of Example 1).

• Centre of mass is offset from centre of rigidity by esi = 1.2 m; plan dimension perpendicular to the force bi = 20 m.
• edi = 1.5 × 1.2 + 0.05 × 20 = 1.8 + 1.0 = 2.8 m (or 1.2 − 1.0 = 0.2 m; take the worse for each frame).
• Torsional moment at base = 864 × 2.8 = 2419 kN·m, shared by the frames in proportion to (stiffness × distance²).
• Drift limit per storey = 0.004 × 3300 = 13.2 mm. If analysis gives 12.0 mm at storey 2 — acceptable; if 15.0 mm at storey 1 — not acceptable, so increase column size or add shear walls (a drift failure at the first storey is also a soft-storey warning).

Example 4 — Strong column–weak beam and capacity shear. Interior joint; beams framing in have Mu = 180 kN·m (hogging) and 120 kN·m (sagging) for sway in one direction → ΣMb = 300 kN·m.

• Required ΣMc ≥ 1.4 × 300 = 420 kN·m. Columns above and below provide 240 + 240 = 480 kN·m ≥ 420 → safe.
• Column design shear, storey height 3.3 m: Vu = 1.4 × 300/3.3 = 127.3 kN — this, not the 60–70 kN from the elastic analysis, governs the hoops.
• Beam of clear span 6.0 m with factored gravity 30 kN/m, end capacities 200 (hogging) and 150 (sagging) kN·m: Vu = 30 × 6/2 + 1.4 × (200 + 150)/6 = 90 + 81.7 = 171.7 kN.

Example 5 — Special confining reinforcement. Column 400 × 600 mm, M25 concrete, hoops of Fe415, clear cover 40 mm to the hoop, s = 100 mm, single rectangular hoop so h = 300 mm (the limit).

• Ag = 400 × 600 = 240 000 mm²; core outside the hoop = (400 − 80) × (600 − 80) = 320 × 520 → Ak = 166 400 mm².
• Ag/Ak − 1 = 240 000/166 400 − 1 = 1.4423 − 1 = 0.4423.
• Ash = 0.18 × 100 × 300 × (25/415) × 0.4423 = 5400 × 0.06024 × 0.4423 = 143.9 mm²; minimum check 0.05 × 100 × 300 × 0.06024 = 90.4 mm² — so 144 mm² governs.
• A 12 mm hoop gives 113 mm² — not enough; use 14 mm (154 mm²) at 100 mm c/c, or add a cross tie so that h reduces to about 170 mm: Ash = 0.18 × 100 × 170 × 0.06024 × 0.4423 = 81.5 mm² → 12 mm legs (113 mm²) are then ample. Confinement length lo = max(600, 3300/6 = 550, 450) = 600 mm at each end.

Where it is used

• Building design consultancies and EPC contractors — L&T Construction, Tata Projects, Afcons, Shapoorji Pallonji, AECOM, Jacobs, WSP, Sterling Engineering: seismic analysis in ETABS/STAAD.Pro/SAP2000 and IS 13920 detailing for every multi-storey project in Zones III–V.
• Infrastructure — Delhi Metro and other metro viaducts and stations, Bandra–Worli Sea Link and the Mumbai Trans Harbour Link (IS 1893 Part 3 / IRC 6 seismic provisions, elastomeric bearings, seismic restrainers), dams and barrages, LNG tanks (IS 1893 Part 2).
• Industrial and power plants — NTPC, NPCIL, refineries: stack-like structures, pipe racks, equipment anchorage and qualification under IS 1893 Part 4; nuclear plants follow stricter AERB codes.
• Housing and public buildings — PMAY and state housing boards, school and hospital construction; masonry detailing to IS 4326 and the BMTPC/NDMA guidelines; post-Bhuj-2001 reconstruction in Gujarat is the benchmark Indian case study.
• Retrofitting and safety audits — seismic evaluation and strengthening of lifeline buildings (hospitals, control rooms), heritage structures and old RC frames with open ground storeys; a growing specialist market under NDMA and municipal mandates.
• Job roles — structural design engineer, seismic/forensic analyst, proof-checker and peer reviewer, geotechnical engineer (liquefaction and site response), government structural engineer approving building plans.

Interview questions

• Q: Why do we design for forces much smaller than the elastic earthquake demand? A: Because the structure is allowed to yield and dissipate energy; ductility and overstrength make up the difference, and this is formalised by the response reduction factor R.
• Q: What does the factor Z/2 in the base shear formula mean? A: Z is the MCE-level effective peak ground acceleration; halving it gives the Design Basis Earthquake, which is the level used for ordinary limit-state design.
• Q: Can I use R = 5 for an RC frame without IS 13920 detailing? A: No. R = 5 is allowed only for a special moment-resisting frame with full ductile detailing; without it the frame is ordinary and R = 3, so the design force rises by about 67%.
• Q: Why is an open ground storey so dangerous? A: The soft, weak ground storey takes almost the entire drift demand, hinges form at both ends of its columns, and the whole upper building topples as a rigid block — the dominant RC failure mode in Indian earthquakes.
• Q: State and explain the strong column–weak beam requirement. A: At each joint the sum of column moment capacities must be at least 1.4 times the sum of beam capacities, so that hinges form in beams and give a distributed, ductile beam-sway mechanism instead of a storey-sway collapse.
• Q: Why is live load on the roof excluded from seismic weight? A: Roof imposed load is transient and unlikely to be present during an earthquake, and it is not physically attached, so it does not contribute reliable inertia mass.
• Q: Why must hoop hooks be bent at 135°, not 90°? A: At large inelastic strains the concrete cover spalls; a 90° hook straightens and the hoop opens, losing confinement, whereas a 135° hook anchored into the core holds.
• Q: Which is better — a stiffer building or a more flexible one? A: Neither always; stiffer buildings attract larger forces but have lower drift and less non-structural damage, flexible buildings attract less force but suffer more drift and P-Δ effects. The choice depends on the site spectrum, height and serviceability needs.
• Q: How does base isolation work and when is it unsuitable? A: Bearings decouple the superstructure from the ground and lengthen the period to 2–3 s, away from the energetic short-period range; it is unsuitable on soft soil with long-period motion, for already flexible tall buildings, and where large base displacement cannot be accommodated.
• Q: What is the difference between magnitude and intensity? A: Magnitude is a single instrumental measure of energy released at the source; intensity (MSK scale) describes observed shaking and damage at a particular place and decreases with distance.
• Q: Why do we add accidental eccentricity of 0.05 b when the centres of mass and rigidity coincide? A: To cover unmodelled asymmetry in mass and stiffness, torsional ground motion and construction variation — a nominally symmetric building still twists.
• Q: How do you decide whether dynamic analysis is required? A: By the code triggers — height and zone (above 15 m in Zones IV–V), and any plan or vertical irregularity in Tables 5 and 6; irregular buildings always need modal analysis, with results scaled to the static base shear if lower.

Common mistakes

• Using the full Z instead of Z/2, or forgetting to divide by R/I, in the seismic coefficient.
• Distributing base shear in proportion to Wi·hi instead of Wi·hi², or including roof live load in seismic weight.
• Picking the wrong period formula — using 0.075 h^0.75 for an infilled frame, or taking d as the dimension perpendicular to the shaking instead of along it.
• Reading Sa/g off the wrong soil curve, or forgetting that the plateau ends at different periods (0.40 / 0.55 / 0.67 s) for hard / medium / soft soil.
• Claiming R = 5 in the analysis and then detailing to IS 456 only — the commonest real-project violation, and the first thing a proof-checker looks for.
• Designing members for the shear from the elastic analysis instead of the capacity-based shear, so the member fails in brittle shear before the intended flexural hinge.
• Omitting the 0.9 DL ± 1.5 EL combination and so missing footing uplift and column tension; and combining earthquake with wind instead of taking the worse of the two.

Related topics

Structural dynamics basics · Tall buildings, shear walls and lateral loads · Reinforced concrete design (IS 456) · Masonry structures · Steel structures design (IS 800) · Repair and rehabilitation of structures