All about Seismic Isolation

All about Seismic Isolation

 

Definition

 

Seismic isolation (commonly referred to as base isolation) is a construction method for protecting buildings, in which the building and ground are separated by an isolation system to limit the transmission of vibrations through the building. It reduces the earthquake force and changes it to a slow vibration, so not only the building, but also everything inside is protected.

In recent years base isolation has become an increasingly applied structural design technique for buildings and bridges in highly seismic areas. Many types of structures have been built using this approach, and many others are in the design phase or under construction.

 

Seismic Isolation System

 

Seismic Isolation System is a collection of structural elements that should substantially decouple a structure from the horizontal components of ground shaking thus protecting the building’s integrity. Isolation System consists of  Isolation Units with or without  Isolation Components.

Isolation Units are the basic elements of an Isolation System which are intended to provide the decoupling effect.
Isolation Components are the connections between Isolation Units and their parts having no decoupling effect of their own.

Accelerated aging tests demonstrate that base isolators for foundations could be used without problems for up to 80 years.
As a practical example, in Australia, rubber bearings installed on a bridge over 100 years ago are still in service without any problems.

Displacement of the isolation system

 

Although it depends on the earthquake and type of isolation system used, an isolator for a building will move about 20 to 30 cm in each direction in a major earthquake.
Around buildings with isolation systems, there is a 40 to 50 cm clearance for movement.

Fig 1. Peripheral clearance of building

Isolation systems are designed so that the building will move back to its original position.

Fig 2. Deformation

Seismic isolation protection against vertical quake motion

In current isolation systems, vertical motion is not considered, because it is horizontal vibrations that cause objects to fall.
For example, if you apply a vertical vibration to an object at rest on a board, it is hardly disrupted. But if you jolt the board horizontally, the object will fall.

Earthquake vibration of buildings in the horizontal direction is considerably reduced by a seismic isolation system.
Therefore, the isolation system prevents equipment from falling even in a vertical quake. The same is true of buildings.

Fire precautions taken for the isolation system

Isolation systems require little fire resistance because they are usually installed under lowest floor of a building, where inflammable materials and ignition sources are not normally found.

However, if multilayer rubber bearings are installed in the middle floor where a possibly of fire exists, some fire resistant protection is required.

Maintenance required after Isolation system installation

Isolation systems with high durability do not require replacement. To maintain reliability and safety, periodic inspection of the building and the isolators is recommended.

After it is struck by an earthquake with a seismic intensity greater thn 5, basic inspection is required.

Position of the seismic isolation system

In addition to underground systems, other places such as the ground floor and liddle floor can also be suitable, as shown in the figure below. The position of the isolators depends on the function and design of the buildings.

Islotation syystem can be applied to the whole site to create a local disaster prevention area.

 

Fig 3. Position of the seismic isolation

Cost of the seismic isolation system

There are various other expenses other than the isolators.

However, there are also benefits such as reduction in thhe required size of the structural members. The percentage of the cost for seismic isolation reduces for taller buildings.

Generally, the additional cost for an isolation system installed in a building with over ten strories is 2 to 3% of the total construction cost.

In addition, considering that seismic isolation improves safety during an earthquake and saves repair costs after an earthquake, the lifecycle cost of a building can be reduced.

 

 

 

What is base isolation for a structure?

What is base isolation for a structure?

 

Introduction

An earthquake has been a major threat to human kind and the world, in the unrecorded and recorded human history. It causes an active shakingdue to volcanic eruption, which causes the failure of weak and badly designed structures, leading to the innumerousfatalities.

Base isolation technique is commonly adopted as safety precaution in earthquake prone areas all over the world. It has been used in New Zealand, as well as in India, Japan, Italy and the USA.

In order to reduce the effects and damages caused by an earthquake, base isolation is implemented in the foundation section of the structure.

This system is designed to take the weight of the building and let the foundations move sideways during the earthquake. It provides flexibility at the supports of a structure in the horizontal plane. Seismic isolation can increase the performance expectation of structure in life and also minimizes damage.

Base isolation is the best method adopted for earthquake resistant building. It is the method of providing a support to the foundation for the buildings in seismic zones as it enables the reduction in earthquake induced forces by increasing the period of vibration of the structure.

It effectively protects the structure against extreme earthquake without sacrificing performance during the move frequent, moderate seismic events. With the conventional method of building earthquake structure, the structure may survive of the earthquake. It may not remain operational after any major seismic event!

This technique of base isolation not only prevents the earthquake from any serious damages but also maintains functionality. Building remains operational after earthquake…

How do base isolators work?

It is a technique to prevent building during an earthquake. A fixed-base building (builtdirectly on the ground) will move with an earthquake’s motion and can sustain extensive damage as a result. Base isolators work in a similar way like car suspension. It is not suitable for all types of structures and is designed for hard soil, not soft.

Types of Isolator

  • Lead-Rubber Bearin
  • Laminated steel-rubber isolators
  • Multi layer stones
  • Filled rubber bearings
  • Active base isolation

Other Types

Apart from bearing and sliding type, there are some other types of isolators, which are also used in building but rarely. Springs, rollers, sleeved piles are some examples of such isolators.

 

 

What caused the Taiwan bridge collapse?

What caused the Taiwan bridge collapse?

 

Several fishing boat workers were among at least a dozen people injured when the bridge,  fell into a waterway in a fishing village.

A 2016 report on bridges in Yilan county had found problems with the expansion joints on the Nanfang’ao bridge, which was completed in 1998 and collapsed Tuesday morning, the official Central News Agency reported. The joints are designed to absorb changes in temperature.

The bridge – although only 20 years old – had previously undergone remediation work after a 2016 report found that the expansion joints were “obviously warped, damaged and sagging”.

CNA cited the report as saying that motorists could sense a difference of levels on either side of the joints, possibly as a result of warping or other problems.

Independent bridge consultant Simon Bourne said that the Nanfang’ao bridge collapse raises questions around the robustness of maintenance regimes in the aftermath of problems that triggered the recent closure of Hammersmith Bridge in London and the fatal collapse of the Polcevera viaduct in Genoa, Italy which claimed the lives of 43 in August 2018.

The company responsible for managing the bridge, Taiwan International Ports Corporation Ltd., earlier said it cleaned the joints and fixed other problems such as rusted steel reinforcements and guardrails in 2017 and 2018.

Experts are also looking into the condition of the bridge’s steel cables, including the possibility of dangerous levels of corrosion.

The 140-meter (460-foot) -long, 18-meter (nearly 60 feet) -high bridge collapsed into a bay on Taiwan’s lightly populated east coast, about 60 kilometers (40 miles) southeast of Taipei. A typhoon swept by the island earlier, but the weather was sunny when the bridge collapsed, and it wasn’t clear if the storm was a factor.

Civil Engineering Salaries around the world

Civil Engineering Salaries around the world

 

 

 

If you’re looking forward to a career that gives you the opportunity to build bridges, design tunnels and maintain and construct other infrastructure projects, then a career in civil engineering is an ideal career path to pursue.

The job of a civil engineer involves checking the site to make sure it is appropriate. There are many branches under this filed and each of them deals with different tasks, some of the branches are as follows:

Civil Engineering Fields:

  • Construction Engineering
  • Geo-technical Engineering
  • Environmental Engineering
  • Transportation Engineering
  • Structural Engineering
  • Coastal Engineering
  • Earthquake Engineering
  • Water Resource Engineering
  • Surveying
  • Municipal Engineering
  • Tunnel Engineering & more…

That’s because civil engineering jobs are all over the world. But it’s a good idea to know how much money civil engineers around the world earn on average to get a sense of what you can expect when negotiating a civil engineering salary. Here are some important factors to consider:

What Affects Your Civil Engineering Salary?

Several elements may impact your civil engineering salary including the location of your company, your level of education, your level of expertise and the amount of experience you have.

Salary based on experience

 

Salary Based On Level Of Education

For instance, civil engineers in the United States make an average annual salary of $65,189, according to PayScale. However, PayScale reports that civil engineers in Australia make an average of $73,051 AUD—about $50,798 USD—per year. Even the city, county, state or province where civil engineering jobs are may impact pay. For example, ZipRecruiter reports that civil engineers in Ontario, Canada make an average of $62,498 USD per year while civil engineers in Quebec bring in an annual salary of $77,011 USD.

Your experience may also impact how much you make as a civil engineer. For example, senior civil engineers in the United States make an average of $119,600, according to Glassdoor. But PayScale reports that senior civil engineers in Toronto, Canada, make an average of $100,964 CAD or about $76,697 USD. So, it’s worth considering the trajectory of your career path as a civil engineer.

The type of civil engineering role you hold also impacts how much you make. Some of the top three jobs for the highest civil engineering salary include engineering project managers, engineering managers, and senior civil engineers, making as much as $196,000 per year in the United States. Your industry may impact your pay, too. For instance, data from the May 2018 report from the U.S. Bureau of Labor Statistics reports civil engineers made the most working for the federal government excluding postal service jobs, bringing in a median annual salary $95,380.

You may also notice that different sources provide various ranges of salaries for civil engineering jobs. For instance, data from PayScale highlights that civil engineers in the United Arab Emirates (UAE) make an average annual salary of 74,604 AED or $20,311 USD. On the other hand, data from the Economic Research Institute (ERI) reports that civil engineers in the UAE make an average of 269,209 AED per year or $73,294 USD. This amount can also look different on a monthly basis. For instance, ZipRecruiter reports the U.S.-based civil engineers bring in an average of $6,418 per month. So, it’s a good idea to consult different sources to get an idea of how much to expect from your engineering salary.

What Do Salaries for Civil Engineering Jobs Look Like Around the World?

If you want a sense of what to expect from a civil engineering salary in a country you’re considering working in, it’s worth comparing salaries for civil engineering jobs around the world. Here are some common annual salaries for civil engineers worldwide, according to ERI:

The demand for civil engineers is bound to increase as the population increases. This is because of an increase in demand for infrastructures such as housing, highways, water supplies and sewerage. However, Civil engineering, like most fields, depends on the economy with the demand being high when the economy is doing well.

 

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