Seismic Retrofit for Safer Structures

Soft-Story Retrofit Companies
The United States has its share of seismic activity. In 2011 August, a 5.8 earthquake hit near Mineral, Virginia, damaging the Washington Monument. And California’s residents felt the effects of the back-to-back quakes which struck July 4th and 5th after even several years. The recent earthquake events made us focus on seismic retrofit for safer structures, so they can sustain the next major earthquake.
While it may seem that earthquakes are happening more frequently, they are actually a pretty common occurrence. What is uncommon is the strength of the quakes that have rocked the world in the last 10 years. In 2010 – 2011, Chile was hit with numerous quakes, ranging from mild to the 8.8 quakes that hit the coast near Concepcion.

Earthquake-Resistant Buildings

Creating earthquake-resistant buildings is not a new idea. No matter the circumstances, human beings are hard-wired to survive. Human’s desire to survive has helped them to achieve amazing advances in the fields of technology, medicine, as well as engineering, and other fields. Within the centuries, engineers have learned how to adapt building designs to create structures that will last for centuries.
Many ancient buildings, constructed in seismic zones, are standing today. One of the best examples is the Hagia Sophia church. Built-in Istanbul in 537 A.D., about 20 years after its completion the area was hit with an earthquake. The huge dome on the church collapsed. Engineers assessed the damage and adapted a new design to make the next dome more quake-resistant. The new dome was smaller and they reinforced the church from the outside.

A number of scientists and engineers agree that with today’s technology it is possible to build an earthquake-proof structure. However, the costs of doing so would amazingly high. Instead of this, most experts have chosen to focus on the next best thing, which is earthquake-resistant buildings. These retrofitted structures are created and designed to limit and avoid loss of human lives and complete collapse during an earthquake.

Earthquake-Proof Structures Against Seismic Activities

One of the first and the most important steps in constructing a new building is determining the potential for seismic activity in the area and design earthquake-proof structures against seismic activities. The United States’ Geological Survey has a handy tool for doing this, which is the National Seismic Hazard Map. This collection of maps can provide valuable information Los Angeles soft story retrofit companies and their contractors. They determine the possibility of seismic activity in an area within the next 50 years.

Geologists use historical data to form an educated guess about the motion of the Earth’s crust and the possible magnitude of an earthquake. This formula looks at all the information not just from the main location, but also from areas around it. Then, they create a colored map that shows the areas around the country that are most likely to be earthquake-prone. It will come as no surprise to Los Angeles residents that the coast of California is considered a high hazard area.

With the help of these geological maps, cities can create building codes that establish guidelines for earthquake-resistant structures. Like the ordinances passed in Los Angeles that created the Soft-Story Retrofit Program. The LA soft-story retrofit contractors and engineers must design and build, all structures such as apartment complexes, bridges, and office buildings to meet these strict seismic codes.

Component Of Earthquake-Proof Design

The shape of the buildings is considered to be the first component of an earthquake-proof design. There are several types of building structure designs:

  • T-shaped structures

  • L-shaped Structures

  • Vertical designs

  • Horizontal designs and others

In high hazard areas, asymmetrical designs, such as T-shaped or L-shaped structures should be avoided. Although they can visually be pleasing, anyway they are more vulnerable to collapsing or twisting due to the forces of an earthquake. The best design is a symmetrical one, this helps to distribute the forces evenly throughout the building.

But even symmetrical buildings can be vulnerable to the lateral forces created by a major earthquake. 

Horizontal And Vertical Structural Systems

The forces of both horizontal and vertical structural systems need to be considered when designing a building to withstand lateral forces. One way to do this is with “diaphragms”. These building components strengthen the floors of a building along with its roof. The roof diaphragm usually includes diagonal trusses for additional support.

The vertical structural system is designed to transfer the forces of an earthquake to the ground. Some components used by many engineers include columns, beams, and bracing. Many buildings include walls that have braced frames, these trusses help them to resist the side-to-side motion created during a quake.

Shear Walls

Along with the braced frames, many buildings have a shear wall that is used to make the building sturdier. Shear walls are usually found near elevators and stairwells.
Shear walls do, however, limit the flexibility of the building design. To overcome this downfall, some designers opt for moment-resisting frames. In these structures, the columns and beams are allowed to bend, but the joints or connectors between them are rigid. As a result, the whole frame moves in response to a lateral force and yet provides an edifice that’s less obstructed internally than shear-wall structures. This gives the designer more flexibility in placing architectural elements, such as exterior walls, partitions, and ceilings, as well as building contents, such as furniture and loose equipment.
The drawback with shear walls is they hinder a building’s flexibility. Many engineers will add moment-resisting frames which allow the columns and beams to bend but keep the connectors rigid. This allows the whole frame to move with the force of an earthquake while still providing support to the building. These moment-frames have the added benefit of allowing designers to add more visually appealing elements to the structure.

About Army Of Builders

Army of Builders is one of many Los Angeles soft-story retrofit companies. Yet, unlike many of the others throughout the area, we offer our customers a no-stress and no-hassle approach to your soft-story retrofit. Army of Builders’ professional staff will guide you every step of the way and create a cost-effective solution for your retrofitting needs. If you have more questions about earthquake-resistant designs - contact us.