May 16, 2020

Skanska USA Announces Management Changes, Names Richard Cavallaro President and CEO

Skanska USA
Richard Cavallaro
Michael Cobelli
Admin
2 min
Michael Cobelli (left) and Richard Cavallaro
Skanska AB has named Richard Cavallaro its Executive Vice President and President and Chief Executive officer of Skanska USA, overseeing the companys US...

Skanska AB has named Richard Cavallaro its Executive Vice President and President and Chief Executive officer of Skanska USA, overseeing the company’s US construction operations, which had combined revenue in 2013 of nearly $7 billion.

Cavallaro, who also will be a member of Skanska AB’s Senior Executive Team (SET), succeeds Michael McNally who is retiring from the same role as planned at the end of the year.

Michael Cobelli will step into Cavallaro’s role as President and Chief Executive Officer of the Skanska USA Civil business unit.

Both Cavallaro and Cobelli are Skanska veterans. The former has been with the company since 1996 and has led the civil business unit for the past five years doubling its revenue and tripling its profit. 

Under his leadership, USA Civil expanded its geographic footprint, shifted from a regional player to a national competitor, became a significant force in the power and industrial space and consistently achieved the company’s best safety record. 

McNally said of his successor: “Rich has a deep understanding of our clients’ needs; a track record of strategic leadership; depth of knowledge; and a straight-forward communications approach.  Adding all of that to his ability to consistently drive results makes me certain that he will continue to strengthen our US operations.” 

As President and CEO of Skanska USA, Cavallaro will be responsible for Skanska’s US construction operations including USA Building, which specialises in building construction, and USA Civil, which is focused on civil infrastructure.  He will be one of nine members of Skanska AB’s Senior Executive Team responsible for global operations.

McNally’s retirement comes after 35 years in construction and six years as Skanska’s US leader. During his tenure, McNally transformed the business into a powerful brand which grew to become the second largest domestic building contractor and the third largest domestic heavy civil contractor. 

Cavallaro said: “It is an honour to lead our tremendous team of employees and this great company. I’m committed to building on Mike’s legacy of One Skanska and working together to innovate and deliver for our clients.   

“Mike has been a great partner and mentor. Because of his relentless focus on our values and advocacy for safety and sustainability, we are known not just as a successful company but a company that cares about its people and our communities.”

USA Civil Chief Operating Officer Michael Cobelli moves into the role of President and Chief Executive Officer of USA Civil. Cobelli has been with Skanska for his entire 30-year career, with a strong focus on project execution. He has personally been involved in constructing some of the most complex and high-profile heavy civil construction projects in the US.

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Jun 17, 2021

Why engineers must always consider human-induced vibration

Vibrations
Engineering
design
Structuralintegrity
Dominic Ellis
3 min
Human-induced vibration can lead to a number of effects upon the structure and its users

Human induced vibration, or more accurately vibrations caused by human footfall, often conjures images of Millennium Bridge-style swaying or collapsing buildings.

But in reality, the ‘damage’ caused by human-induced vibrations is less likely to ruin a structure and more likely to cause discomfort in people. Though not as dramatic as a structural failure, any good engineer wants to make sure the people using their structures, be it bridges or buildings or anything in between, can do so safely and comfortably. This is why human-induced vibration must be considered within the design process.

Resonance v Impulse

There are two ways that human-induced vibrations affect structures: resonant, and impulse or transient response. Put simply, resonance occurs when Object A vibrates at the same natural frequency as Object B.

Object B resonates and begins to vibrate too. Think singing to break a wine glass! Although the person singing isn’t touching the glass, the vibrations of their voice are resonating with the glass’s natural frequency, causing this vibration to get stronger and stronger and eventually, break the glass. In the case of a structure, resonance occurs when the pedestrian’s feet land in time with the vibration.

On the other hand, impulse or transient vibration responses can be a problem on structures where its natural frequencies are too high for resonance to occur, such as where the structure is light or stiff. Here the discomfort is caused by the initial “bounce” of the structure caused by the footstep and is a concern on light or stiff structures.

Engineers must, of course, design to reduce the vibration effects caused by either impulse or resonance.

Potential impacts from human induced vibration

Human induced vibration can lead to a number of effects upon the structure and its users. These include:

  • Interfering with sensitive equipment Depending on the building’s purpose, what it houses can be affected by the vibrations of people using the building. Universities and laboratories, for example, may have sensitive equipment whose accuracy and performance could be damaged by vibrations. Even in ordinary offices the footfall vibration can wobble computer screens, upsetting the workers.
     
  • Swaying bridges One of the most famous examples of human-induced resonance impacting a structure occurred with the Millennium Bridge. As people walked across the bridge, the footsteps caused the bridge to sway, and everybody had to walk in time with the sway because it was difficult not to. Thankfully, this feedback can only occur with horizontal vibrations so building floors are safe from it, but footbridges need careful checking to prevent it.
     
  • Human discomfort According to research, vibrations in buildings and structures can cause depression and even motion sickness in inhabitants. Tall buildings sway in the wind and footsteps can be felt, even subconsciously by the occupants. It has been argued that modern efficient designs featuring thinner floor slabs and wider spacing in column design mean that these new builds are not as effective at dampening vibrations as older buildings are.
     
  • Jeopardising structural integrity The build-up of constant vibrations on a structure can, eventually, lead to structural integrity being compromised. A worse-case scenario would be the complete collapse of the structure and is the reason some bridges insist that marching troops break step before crossing. Crowds jumping in time to music or in response to a goal in a stadium are also dynamic loads that might damage an under-designed structure.

How to avoid it

As mentioned, modern designs that favour thinner slabs and wider column spacing are particularly susceptible to all forms of vibration, human-induced or otherwise, but short spans can also suffer due to their low mass. Using sophisticated structural engineering software is an effective method for engineers to test for and mitigate footfall and other vibrations at the design stage.

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