Tag: cities

Did Quick Construction Technique Lead To FIU Pedestrian Bridge Collapse?

The unfinished pedestrian overpass that toppled onto the Tamiami Trail on Thursday was being built under a relatively novel approach called accelerated bridge construction.

A fast, tested method that carries some risks if not rigorously carried out.

Until it’s fully secured, a quick-build structure is unstable and requires the utmost precision as construction continues.

Properly shoring up the bridge can take weeks, a period during which even small mistakes can compound and cause a partial or total collapse, said Amjad Aref, a researcher at University at Buffalo’s Institute of Bridge Engineering.

Just before the bridge’s concrete main span abruptly gave way on Thursday, crushing four people in cars to death and injuring others, a contractor’s crews were conducting stress tests on the incomplete structure, Miami-Dade Mayor Carlos Gimenez said.

The 950-ton span, assembled by the side of the road over a period of months, was hoisted into place in a matter of hours on Saturday morning.

That stress testing typically involves placing carefully calibrated weights on the span and measuring how the structure responds to ensure it’s within safe parameters, Aref said.

Crews may also have been adjusting tension cables that provide structural strength for the span’s concrete slabs.

In almost all bridge or building collapses, though, construction errors are to blame, not design, said Ralph Verrastro, a Cornell-trained engineer and principal of Naples-based Bridging Solutions, which is not involved in the FIU project.

Determining what exactly went wrong will likely take months. The National Transportation Safety Board has opened an investigation.

Over the coming weeks, forensic engineers will try to unravel what happened in a complicated analysis that involves picking through debris, looking at designs, and piecing together inspections, said Princeton University civil engineering professor Maria Moreyra Garlock.

The construction phase, she noted, is often the most dangerous point in the life of the bridge.

Engineers could sample material at the site to test for strength, she said, and look at the sequence of inspections to determine what happened when.

Site inspections might also reveal what caused the sudden collapse.

Thursday’s tragic accident is sure to raise questions over the decision by Florida International University to take the quick-build approach, adopted in large part to minimize the need to interrupt traffic on the busy highway.

The decision by its contractors to undertake testing while traffic flowed along the busy roadway below will also be scrutinzed. FIU was running the project under an agreement with the state.

Accelerated bridge construction has become more common in the past decade, especially in urban areas with heavy traffic, Verrastro said.

FIU’s engineering school has become a hub for accelerated bridge construction training and research in recent years.

The bridge was devised to provide FIU students and others a safe way to cross multi-lane Southwest Eighth Street, also known as the Trail, to the small town of Sweetwater, where the school estimates some 4,000 students live.

At least one student was hit and killed by a car at that busy crossing, at 109th Avenue, which leads to new apartments built by private developers designed to cater to the university.

FIU selected the contracting team in a competitive process. It consists of MCM Construction, a family owned contractor based in Miami, and Figg Bridge Group, a design and engineering firm based in Tallahassee.

MCM is one of the most influential contractors in Miami-Dade, and a top contributor to county races. Gimenez said he spoke to co-principal Pedro Munilla by telephone from Hong Kong, where the county mayor is leading a county trade mission.

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Noise Pollution Is A Bigger Threat To Your Health Than You May Think

It’s almost impossible to find complete peace and quiet.

Even if you live deep in the countryside away from aircraft routes, traffic and building work, your home is probably filled with the buzz of computers and other modern appliances.

In some locations, there are even claims of mysterious low-pitched noises with no known origin.

For example, residents of Bristol in the west of England recently complained of a “hum”, which followed reports of a similar sound in the city in the 1970s.

Such sounds aren’t just annoying. There is increasing evidence that long-term environmental noise above a certain level can have a negative influence on your health.

These effects can be physical, mental and possibly even disrupt children’s learning.

Physical reaction

Recent research shows that road traffic and aircraft noise increase the risk of high blood pressure, especially noise exposure at night.

A study of aircraft noise around London’s Heathrow airport found that high levels of aircraft noise was associated with increased risks of hospital admission and death for stroke, coronary heart disease, and cardiovascular disease in the nearby area.

Another large study that looked at aircraft noise exposure over a much longer time period of 15 years found that deaths from heart attacks increased when the noise was louder and endured over a longer period of time.

The latest estimates suggest a ten decibel average increase in aircraft noise exposure was related to an increase in high blood pressure, heart attacks and strokes of between 7% and 17%.

Your emotional response to noise pollution can also be significant, so much so that it has a specific name: noise annoyance.

This describes the negative feelings noise can create such as disturbance, irritation, dissatisfaction and nuisance, as well as a feeling of having one’s privacy invaded. Annoyance can vary widely between different people, however

As well as the type and volume of the sound, other factors include how much it interferes with your activities, the fear you feel associated with the source of the noise, your coping mechanisms and even your belief about whether the noise is preventable.

The impact of noise on children’s learning is less well understood.

It may be as simple as aircraft noise interfering with teachers communicating with pupils, or it may be that pupils focus their attention so narrowly in noisy conditions that they exclude useful speech as well as unwanted noise.

But we do know that it’s not just due to the fact that people living around airports are sometimes poorer because when researchers have taken this into account they’ve found their results still apply.

What is clear is that noise pollution does affect a large number of people and is a significant risk to their health.

Because of this, we need to think about interventions to reduce noise at source by masking or screening it using barriers or sound insulation, or even better by designing our society to be less noisy in the first place.

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Los Angeles Is Painting The Streets To Fight Climate Change

Los Angeles is slathering its streets in white sealant to fight the effects of climate change – and if it works, the rest of the US could be next.

California is pioneering the $150,000 scheme to cool down the blisteringly hot streets in August by by turning some of its streets white which can reduce temperatures by up to 15 degrees.

The lighter “cool pavements” and streets reflect as much as 30 to 50 percent of the sun’s energy, compared to only 5 percent for new asphalt, and 10 to 20 percent for aged asphalt.

And with climate scientists predicting that temperatures are only going to rise, measures such as this could be crucial to preventing heat exhaustion, heat stroke, and even heat-related deaths across America.

The average annual temperature in the Southwest has already gone up 1.56 degrees since 1901-1960 and is projected to rise another 4.8 degrees by mid-century and 8.65 degrees by the end of the century if carbon pollution continues unabated.

While California’s three-year spell of hot dry weather has been connected to climate change.

With more ‘extreme heat‘ days predicted by the mid-century, cool pavements may be one of a series of useful tools for reducing heat in American cities which suffer from the urban heat island effect – caused by a lack of vegetation and paved surfaces.

When we look at our vulnerabilities associated with climate change, we know that extreme heat is one of our top concerns,” Lauren Faber, the city’s Chief Sustainability Office, said.

For now, the city is moving ahead a few thousand square feet of cool street at a time for the pilot project. The Bureau of Street Services has budgeted $10,000 per installation, with one in each of LA’s 15 districts.

If successful it could be rolled out state, or even nationwide. But even then, the scheme would still only be applied in the areas that needed it most.

The concept of cool pavements has been around for years, and can be made from traditional pavement materials that are lighter in color, or can be painted with cool-colored coatings or surface treatments for asphalt surfaces.

But it is only now that they are being rolled out in the first scheme of its kinds. Sealants such as CoolSeal have shown around a 10-degree reduction in heat gain.

However, residents in some of the pilot areas, such as Canoga Park where the streets have been slathered with CoolSeal since May, say they have already noticed the difference.

Sealcoats are already a common maintenance practice for parking lots and schoolyards since the asphalt pavement structure degrades over time.

Traditional sealcoats provide a protective layer, keeping water out and helping to slow the oxidation of the asphalt in the pavement structure, while restoring the aged asphalt surface to a jet-black color.

Cool pavement sealants come in different hues, including green, blue and yellow, and their solar reflectance value depends on both color and material.

The benefits of cool pavements extend beyond just cooling the local ambient air. They can also impact global warming and energy loads.

Dark roofs and dark pavements both contribute to global warming by absorbing large amounts of solar energy stored in sunlight, then radiating the energy back into the atmosphere in the form of heat.

LA is also looking at tackling the heat by creating an urban tree canopy and the city is offering free shade trees to residents to cool the area, donating 18,000 free trees last year alone.

The city also enacted an ordinance that requires most new and renovated buildings to install lighter colored roofs with high solar reflectance ratings.

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