Why Do Buildings Fail in Earthquakes? Lessons Every Engineer Must Know

Understanding seismic failures, structural mistakes, and the engineering lessons from the 2001 Bhuj Earthquake.

Introduction

It was Republic Day. Families were having a relaxed time in their homes when the ground suddenly began to tear apart beneath them. The ground didn’t just shake, it exploded.

James, A. (n.d.). 2001 Gujarat Earthquake: When India Faced One of its Worst Disasters 25 Years Ago [PHOTOS]. IBTimes India.

In a matter of just 90 seconds, a Mw 7.7 earthquake turned Bhuj into a graveyard, becoming one of India’s deadliest seismic disasters. More than 20,000 dead, 166,000 injured and 600,000 left homeless. Eighty percent of the city’s buildings simply disappeared.

A 20-year-old building and a newly built apartment complex folded like a deck of cards. Across the city, a government school, supposed to be “earthquake resistant”, crumbled into dust. Yet nearby, an old stone temple barely lost a single carved pillar.

Why do some structures survive earthquakes while others collapse completely?

For over 5,000 years, we’ve built structures, yet earthquakes expose the weakest flaws in structural design. Here’s the truth: Buildings rarely collapse because the quake was “too strong.” They collapse because we have left behind the fundamentals of engineering, seismic design, and structural safety.

Let’s walk through the wreckage of Bhuj. Here are five reasons buildings fail and the lessons every engineer must understand to create earthquake-resistant structures.

1. The Pancake Collapse – Soft Storey Failure

Soft storey collapse during Bhuj earthquake (N Sivakumar, et al., 2013)

Across Bhuj, several multi-storey apartments had open ground floors used for parking or shops. The upper floors were enclosed with rigid concrete, while the ground floor relied only on slender columns and glass façades.

When the shaking started, the soft ground floor swayed wildly while the upper floors resisted. The stress concentrated entirely at the base level. Within seconds, columns snapped like dry sticks and the building collapsed vertically floor upon floor.

2. The Building That Fought Itself – Torsional Irregularity

Mansi Complex, Ahmedabad after structural collapse during the Bhuj earthquake.

A well-known example from the Bhuj earthquake was the failure of irregularly shaped structures, such as the Mansi Tower in Ahmedabad, a striking L-shaped building. The owners added a private swimming pool on the roof. This shifted the centre of mass far from the centre of rigidity. During the quake, the heavy side pulled one way, while the lighter wing lagged behind. Thus, the entire building twisted its columns off their foundations.

3. The Short Column Effect – The Overlooked Failure Mechanism

Schools and offices with beautiful windows and squat concrete columns between them faced earthquake failures.

When seismic forces struck, those short, stiff columns couldn’t flex. They attracted huge shear forces and fractured horizontally, resulting in loss of structural support.

4. The Weak Joint Betrayal – Beam-Column Joints

Post-earthquake, investigators found that in many collapsed buildings, the beam-column joints had no confining stirrups. The steel rebars were smooth mild steel, not the required deformed bars for seismic resistance. The hooks were too short. When the quake hit, the rebars pulled out like nails from soft wood, and the beam-column joints disintegrated under seismic loading.

5. The Soil Liquefaction Lie- Foundation Failure Beneath the Surface

Bhattacharya, Subhamoy & Sarkar, Rajib & Huang, Yu. (2012). Seismic Design of Piles in Liquefiable Soils.

Another example was the Port & Customs Office Tower at Kandla. A sturdy building with deep foundations, but it stood on ground with water-saturated sandy soil. The shaking turned that sand into behaving more like liquid than solid ground, losing its strength and stiffness. The building didn’t collapse; it simply tilted sideways as the foundation lost all bearing capacity.

The 3 Rules Every Engineer Must Never Forget

• Ductility saves lives brittle = death, flexible = survival.
• Symmetry is safety – if the plan is irregular, put in a seismic joint.
• The ground lies – never assume the soil is “good enough.”

The Ugly Truth – Bhuj Exposed

• Builders used flat strips of mild steel instead of deformed high-yield bars.
• Concrete used was with insufficient cement content
• Beam-column joints lacked stirrups.
• Inadequate on-site inspection during construction.

Resilience vs. Life Safety – The New Frontier of Earthquake Engineering

Most building codes (IBC, Eurocode 8) are designed for Life Safety; that means the building may suffer structural damage or even partial collapse, but should remain standing long enough for occupants to escape alive.

After Bhuj and the 2023 Turkey-Syria earthquake, engineers saw “code-compliant” buildings experience catastrophic structural failure, including pancake collapse, because the code allowed too much flexibility.

We now need Immediate Occupancy buildings that shake and still work as hospitals the next day. That’s the frontier.

Let’s Argue (Professionally) in the Comments

We’ve given you the failures and the lessons. We want to hear from the trenches.

1. The Cost Reality: We know how to build a perfect seismic fortress. But with inflation and budget cuts, how do you convince a client to pay for ductile detailing when “nobody has felt a big one in 50 years”?
2. The Existing Stock: Millions of URM (unreinforced masonry) buildings still stand in seismically active cities. Retrofitting costs as much as rebuilding. Is it ethical to design “perfect” new buildings while leaving behind the deadly old ones?
3. AI vs. Intuition: AI can optimize structural layouts. But can it feel torsion? Are we losing the intuitive engineer who spots failure just by looking at a floor plan?

Stay safe, Design smart, Build stronger, and respect Earthquake!

Drop your best seismic war story below.