Monday, June 22, 2009


The NatHaz lab is attending the 11th Americas Conference on Wind Engineering in San Juan, Puerto Rico.

Some of the topics we will present include:

- Analysis of the surface pressure characteristics of prismatic models in gust front and downburst outflows

- Efficacy of damage detection measures for digital images

- Anatomy of damage to coastal construction: a multi-hazard perspective

- Consequences of urban aerodynamics and debris impact in extreme wind events

- A framework for Gust-Front Factor

- Load factors for dynamically sensitive structures

Tuesday, June 16, 2009

NY Times: study says U.S. winds are slowing

A June 15th, 2009 article in the New York Times (click here for the link) highlights a recent study that suggests wind speeds in the U.S. have been decreasing over the last 30 years.

A copy of the paper can be found here: S.C. Pryor et al., 2009 (Journal of Geophysical Research - Atmospheres)

Although there are issues pertaining to the data sets themselves, and the conditions of data collection (which are discussed in the paper), it does pose an interesting problem for U.S. Government mandates to harness more energy from wind to replace non-renewable sources. One of the authors did point out that most wind speed measurements are collected at airports, ~30 feet above the ground surface, which may differ from the wind speeds experienced by wind turbines at higher elevations.

The more interesting comment, however, was that a possible cause for the "slowing" winds might be the level of reforestation occurring in the U.S., the fourth fastest rate in the world between 2000 and 2005. Increasing forest cover my provide some much needed wind protection for many low rise structures that are currently reside in open exposures.

Thursday, June 11, 2009

The Multi-Hazard Threat

(In addition to features about research in the NatHaz lab, we will periodically post news reports of interest which might spark interesting conversations)

As engineers, we typically like to focus on one problem at a time. However, multiple hazards occurring at the same time present an interesting puzzle for risk assessment and engineering design.

This report, Typhoons trigger earthquakes on Taiwan (click link for news report), highlights research which identifies sensor recordings of 20 "slow" earthquakes coinciding with 11 typhoons. The "slow" earthquake unfolds over a hours or days, rather than a few minutes or seconds. The researchers suggest that the low atmospheric pressure generated by the typhoon actually relieves pressure on one side of the converging plates. Interestingly, it is theorized that the stress relief caused by the typhoon may actually inhibit larger earthquakes from occurring, periodically releasing the stress build-up.

The question that remains is how do tall structures in Taiwan react to both the occurrence of "slow" earthquakes and wind action of the typhoon?

Friday, June 5, 2009

Saga of glass damage in hurricanes

Hurricane Ike impacted the Houston CBD at 2:30am on Sept. 13, 2008. Interesting damage patterns emerged, prompting engineers and researchers to examine the issue of urban aerodynamics related to glass damage.

The NatHaz Lab collected images of the damage, eyewitness accounts and utilized various techniques to assess the causes of glass/cladding damage to the JP Morgan Chase Tower (wikipedia link).

An earlier preliminary report of this investigation can be found on the NatHaz website. A direct link to the report is here (link to .pdf of report). Details of the findings since the earlier report, being presented at 11ACWE, can be viewed here (link to .pdf of full paper)

We invite you to post comments and your ideas about our findings, or the overall issue, in the "comments" section.

There is a lot to be learned!

Welcome to the NatHaz Blog

Welcome to the NatHaz Modeling Laboratory Blog. This will be a space to showcase some of the research being conducted in the lab, and to facilitate discussions about important topics using web-sourcing involving the "TechnoCrowd".

For more information about the NatHaz Lab, please view our laboratory website at the University of Notre Dame (NatHaz @ UND)