Car-free zones saw boost in share of consumer activity compared to the rest of the city during Covid-19

Car-free zones saw boost in share of consumer activity compared to the rest of the city during Covid-19:

Analysts at the listing platform looked at restaurants in Boston’s Little Italy, San Francisco’s Mission District, Chicago Central Loop’s West Fulton Market, downtown Boise’s 8th Street and Burbank’s San Fernando Boulevard, all of which had slow streets programs that blocked vehicle access in 2020. They measured the difference in the share of consumer interest between the sample of restaurants in each slow street zone and all restaurants across each respective city, comparing the start of the pandemic (using March 15, 2020 as a proxy), when these programs weren’t yet in place, to the various time periods when the programs were in swing. (The chart below shows that difference.) Eateries in car-free areas saw more consumer interest (based on the amount of views, posted photos and user reviews on Yelp listings) when their streets were strictly limited to pedestrians and cyclists, they found. 

My Year in Cities, 2020

What a different year.

As is my tradition, below is a list of cities I have visited in 2019. I count only cities where I spend a majority of the day or a night in. Cities with an asterisk (*) denote visiting the same city on non-consecutive days.

  • New York City, NY *
  • Columbus, OH *

See where I’ve been in 2019, 201820172016201520142013201220112010, and 2008.

Weekly Links 10

Here are the things I’ve been looking at this week. Past weekly Links 9, 8, 7, 654, 3, 2, 1.

On heritage narratives

On an otherwise typical article about the interaction of city residents, outside groups, and government – Why Detroit Residents Pushed Back Against Tree-Planting – is a mention of a concept I’ve never seen: heritage narratives. The author defines heritage narratives as:

…the stories that people from all walks of Detroit life tell themselves and each other about why city conditions are the way they are. The heritage narratives that residents shared about trees in Detroit were different from the ones shared among the people in city government and The Greening of Detroit.

I love this – this encapsulates what I’ve been searching for when observing that different residents of a place have different views on what the city is, or should be. It brings together the fact that different people, with different contexts, can have a wildly divergent view of where they live, and how they got there.

About the FIU-Sweetwater UniversityCity Bridge

Yesterday the main span of the FIU-Sweetwater UniversityCity Bridge collapsed, with an unknown amount of fatalities:


The graceful pedestrian bridge was swung into place on Saturday. Heralded as a triumph of “accelerated construction,” the walkway would allow pedestrians to safely cross eight lanes of traffic separating the campus of Florida International University from the small city where many of the students lived.

Five days later, around midday Thursday, the walkway collapsed in a pile of 950 tons of metal, concrete and dust, before ever opening to pedestrians. At least six people were killed, according to the Miami-Dade County police. Some reports put the number of dead a high as 10.

I wanted to quickly talk about what is going on here, since there are lots of idle speculation on the cause. Some disclaimers: I’m a trained, yet unregistered architect, and not an engineer. But I am trained in structures, and if you want to talk offline about shear forces on a simple beam, I’m all ears.

This accident ill no doubt be taught as a case study to architects and engineers, much like the Kansas City Hyatt Regency walkway collapse or the Kemper Arena Roof Collapse:

Here’s some basic facts about the bridge which I feel are material to this accident.:

  • The bridge was designed as an asymmetrical cable-stayed bridge
  • The 174-foot, 950-ton section of the bridge was built adjacent to Southwest Eight Street
  • The main span appears to be constructed of prefabricated concrete sections, the post-tensioned in place
  • The span was then rotated and moved to be installed on two supports
  • The cable-stay were not in place yet
  • The bridge appears to not have shifted off the end supports (the two ends rotated along what looks like a pin connection).
  • It appears that the span would act as a truss, or have truss-like forces on it

It appears that the bridge failed in tension on the bottom chord (where people would walk), due to either asymmetrical weight or punching shear from one of vertical truss webs. The failure point appears to be 1/3rd from end of the span – in a simply supported beam such as this span, the highest shear stress (think material deforming) is at the ends of the span, and the largest moment (or propensity to turn over or rotate) is at the center of the span. So failure at the 1/3rd point is cause for concern and is the asymmetrical nature of the truss. Moving the bridge and installing it shouldn’t have been an issue, and this type of span construction isn’t new. That being said, it isn’t exactly a common type yet.

Here are some questions I would want to know in order to determine how it failed:

  1. What were the condition of the concrete sections? Were they given adequate time to cure?
  2. What condition are the post-tensioning system? Was it done correctly?
  3. During movement, were any of the sections knocked out of alignment?
  4. Why does it appear that some of the vertical webs punched through the bottom chord?
  5. What was the schedule? Were the contractors behind or at schedule?
  6. What unforeseen loads were placed on the bridge?

What is highly probable is that a series of small changes, or construction, or fabrication mistakes reduced the overall factor of safety on the span, speeding failure.

My Year in Cities, 2016

As is my tradition, below is a list of cities I have visited in 2016. I count only cities where I spend a majority of the day or a night in. Cities with an asterisk (*) denote visiting the same city on non-consecutive days.

  • New York City, NY *
  • Hyde Park, NY
  • Hudson, NY
  • Phoenicia, NY
  • Long Beach, CA *
  • Los Angeles, CA
  • Santa Monica, CA
  • Venice, CA
  • Rancho Santa Fe, CA
  • Akron, OH *
  • Chicago, IL *
  • Columbus, OH *
  • Las Vegas, NV *
  • Montauk, NY
  • Henderson, NV *
  • Orlando, FL
  • Sullivan County, NY
  • Cleveland, OH
  • Philadelphia, PA*
  • North Lawrence, OH
  • Fort Collins, CO
  • Denver, CO

See where I’ve been in 20152014, 2013, 2012, 2011, 2010, and 2008.

Urban Links IV

Policy

New York

Transportation

Other