AWARD WINNING SEISMIC ENGINEERS

Non-Ductile Concrete Retrofit Program

Non-Ductile Concrete Building Retrofit

The city of Los Angeles Department of Building and Safety has designed the Non-Ductile Concrete Retrofit Program aiming to help reduce injury or loss of life from the effects of an earthquake on non-ductile concrete properties and structures. The recent earthquakes all over the world have shown the weakness of such kind of structures and the devastating loss of lives because of them. In California, non-ductile concrete buildings that were constructed prior to the Los Angeles City Buildings Code provisions are at risk of collapse and pose notable life safety hazards.
The non-ductile concrete retrofit program provides a guide for property owners to meet the less standard in improving the performance of these kinds of structures.


Non-Ductile Concrete Buildings

Non-ductile concrete buildings are considered dangerous for two main reasons:

  • Most of them were built before 1977 (before seismic building codes were created)

  • The concrete used in their frames has become brittle over time and it is at risk of cracking and collapsing during any seismic activity.

The floors and roofs of most of these buildings have made of concrete that is only supported by the concrete walls. There is a big chance, in case any of the floor or walls crack, the structure can completely and quickly collapse. Unfortunately, non-ductile concrete buildings are built across the world and they are considered to be the most dangerous structures which lead to more fatalities during an earthquake, than any other.
When the city of Los Angeles presented its mandatory seismic retrofit program, most of the non-ductile concrete structures were involved. Over thousands of these types of buildings are located all around the city - those are the buildings that most likely can collapse on themselves in an earthquake event. Retrofit contractors are needed to make the target structures safer and more resistant to seismic activities.

Los Angeles seismic retrofit program has become quite advanced in its fourth year. The estimates have done recently, show that only 14% of the soft-story retrofits have been performed - but sadly, 0% of the non-ductile concrete retrofits have been started, although the retrofit deadline for these types of buildings is further out than the other soft-story buildings.

Earthquakes Damage Concrete Buildings

The city of Los Angeles is located on several fault lines one of the largest being the Santa Monica Fault Line. When a fault line ruptures it causes movements in the earth surrounding it. 

Depending on the severity of the quake the far this shakings and movements occur, and it is not a secret that earthquakes can cause large damage to city structures, and particularly earthquakes damage concrete buildings.

A fault that ruptures near, or under the building can cause a reduction of soil, which means there is less weight-bearing soil under the structure and it can even sink into the ground.
blocks sinking  into the ground in an earthquake event

Buildings that are placed near a mountain or a hill can be damaged in case an earthquake causes a landslide. In another case, if an ocean or a lake is nearby the buildings, an earthquake can cause larger waves to hit them and may lead to water damage and flooding.

LA Retrofit Program’s Purpose

In 2015, Los Angeles separated and created its own ordinances, designing two new ones around seismic building codes.

The great destruction caused by the Northridge earthquake in 1994 had a big impact on the creation of the program - the whole city blocks were destroyed and 60 people’s lives were lost. The LA retrofit program’s purpose was is to prevent the same again in the future.

San Fernando Valley is considered the center of an earthquake in CA. The valley can experience more than 100 mild to moderate quakes in a year. In older structures, not only massive but also mild earthquakes can cause real damage. Another purpose of the retrofit program is to develop the resilience of the city after any natural disaster.

Retrofit Program Timeframe

The retrofit program timeline between soft-story buildings and non-ductile concrete buildings is quite different. The City officials mailed-out reports complying with all of the property owners they deemed to be at risk to collapse or get damaged in seismic activity. If you have received any of these letters, you have three years from its date to file a full checklist along with supporting documents to the Los Angeles Department of Buildings and Safety.

  • Proof of the previous retrofit

  • Structural analysis and detailed plans showing full compliance

  • Plans to retrofit

  • Plans to demolish

Property owners have 10 years from the date of the notice to submit the point we mention above and then they have 25 years from the date of the notice to have the retrofit completed or to demolish their buildings.

Where To Begin A Retrofit?

The first thing you should do is hire a company that is specialized in seismic construction. Learn more about how long they have been in the industry or how many similar projects they have completed, also getting their insurance certification will help you get a clearer idea about who are they - most retrofit contractors supply you with any documentation that you ask for. But where to begin a retrofit after all?

The first step is to have your structure inspected to find out how much works need to be done to bring it up to the current codes. When the inspections are completed, your contractor will present a detailed work plan for you. The plans should include designs for the retrofit, an estimate of the cost, as well as options for you to choose from and a timeline for how long the retrofit works will take to complete.

Before The Construction Works

Before any construction begins, the retrofit designs have to be submitted to the city for approval and application for a work permit must be filed. In general, it takes about a month for both of these to be approved. If you are a landlord and you have landlords in your property, you will also need to fill out then submit a Tenant Habitability Plan and file it with the LA Housing and Community Investment Department.

If a Tenant Habitability (THP) is needed, you can not start any construction until two months after it is served to your tenants. Tenants will get 15 days from the day of service to appeal to anything in the plan they do not agree with. Sometime, tenants may have to be temporarily relocated before construction starts, depending on the scope of the retrofit works.