Sign Up

Sign Up to The Constructor to ask questions, answer questions, write articles, and connect with other people. VIP members get additional benefits.

Sign In

Login to The Constructor to ask questions, answer people’s questions, write articles & connect with other people. VIP members get additional benefits.

Free Signup or Login to continue Reading...

Forgot Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

Sorry, you do not have permission to ask a question, You must login to ask question. Become VIP Member

Free Signup or Login to continue Reading...

Do you need to remove the ads? Become VIP Member

Print, PDF & Email

Progressive collapse or disproportionate collapse of a building occurs when the failure of a single structural element leads to the failure of other components in a progressive manner. The failure starts with the primary structural element, accompanied by the failure of adjoining elements, finally resulting in structural collapse.

Progressive Collapse of Building Structures
Figure-1: Progressive Collapse of Building Structures

Progressive collapse is associated with the collapse of structures, caused due to accidents, actions of overload, failure of the material, design deficiencies, or natural phenomena. These triggering effects result in a collapse that is out of proportion. Hence it is also termed as disproportionate collapse.

This article explains the important causes of progressive collapse and some of the notable cases around the world.

Causes of Progressive Collapse

Progressive collapse of structures can occur to varying degrees and is dependent on several factors. Based on years of studies and investigations conducted, the two main notable causes of progressive collapse of structures are:

  1. Design or construction errors
  2. Extreme loading conditions

1. Progressive Collapse of Structures due to Design or Construction Errors

The structures are designed and constructed efficiently to withstand different loads without undergoing excessive deformation. A bad design originates when a designer fails to consider the loads that a building is expected to resist. Some of the design errors that result in progressive collapse are:

  1. Inaccurate design data
  2. Erroneous design drawings
  3. Invalid design assumptions

The construction errors that result in progressive collapse are:

  1. Poor construction methodologies
  2. Inadequate supervision of construction workers
  3. Deficient assembly
  4. Material deficiencies due to production errors
  5. Non-conformance to the required design specifications

2. Progressive Collapse of Structures due to Extreme Loading Conditions

A structure is expected to experience extreme loading conditions during its lifetime. This load is more than the normal design assumptions and could result in abnormal loading hazards like impact, blast, or deformation-related loads.

Impact loads are high-intensity loads acting for a short duration, which results in unusual structural response compared to the conventional dynamic loads like wind and seismic loads. Some of the examples of impact loads are aircraft impact, vehicular collision, etc. Blast loads like bomb detonation and gas explosion also result in similar consequences.

Check Here The Constructor VIP

Deformation-related loads include foundation subsidence and fire. Foundation subsidence is the phenomenon of downward displacement of supporting ground, whereas fire results in the softening of steel in structures, which results in progressive collapse.

The abnormal loading conditions on structures are not commonly observed and hence are not usually considered in the structural design due to economic issues and the inability to accurately predict the extreme scenarios.

Important Examples of Progressive Collapse of Structures

There have been numerous examples of progressive collapses in different countries. The severity of progressive collapse and the interest in studying the issue was initiated by the partial collapse of the Ronan Point apartment building in East London in 1968.

Progressive Collapse of Ronan Point Apartment East London

The Ronan Point was a 22-story building made out of precast concrete bearing walls. On 16th May 1968, an explosion due to a gas leak on the 18th floor of the building created an explosion that blew the exterior wall panel away from the building. This explosion triggered a partial collapse of the structure. The collapse resulted in the death of a few and caused injury to many.

Progressive Collapse of Ronan Point Apartment East London
Figure-2: Progressive Collapse of Ronan Point Apartment East London

It was later determined that the Ronan Point building was not designed for structural integrity. There was no redundancy assigned for load distribution to face any local failure within the building.

Progressive Collapse of the World Trade Centre Towers

The progressive collapse of the twin towers in the World Trade Center in New York is one of the most recognized cases around the world. Two planes crashed into the twin towers at a high speed on 11th September 2001. The crash caused severe damage to the principal structural elements of both the towers like the core structural walls, the perimeter columns, and the floors.

Progressive Collapse of the World Trade Centre Towers
Figure-3: Progressive Collapse of the World Trade Centre Towers

The building withstood the impact for some time even after the initial damage. This is due to its structural integrity and a sound load distribution system. But the quickly spreading fire across the towers reduced the effectiveness of major structural elements and resulted in the collapse of the towers.

FAQs

What is progressive collapse?

Progressive collapse or disproportionate collapse of a building occurs when the failure of a single structural element leads to the failure of other components in a progressive manner. The failure starts with the primary structural element, accompanied by the failure of adjoining elements, finally resulting in structural collapse.

What causes progressive collapse?

Progressive collapse occur either due to:
1. Design or construction errors
2. Extreme loading conditions

How do extreme load conditions result in the progressive collapse of structures?

The extreme load conditions that can trigger progressive collapse are impact loads, blast loads, and deformation-related loads. Examples of impact loads are aircraft impact, vehicular collision, etc. Gas explosion, bomb detonation are examples of blast loads on structures. Foundation subsidence and fire are examples of deformation-related loads.

Read More

Outrigger Structural System for High-Rise Building: All You Need to Know

A New Drone-based System to Assess Aging Infrastructure Projects

Materiality in Architecture: 7 Eco-Friendly Materials to Look Out For

Neenu Arjun

Related Posts