Windborne Debris Research Articles

Windborne debris and damage risk models: a review

This review paper discusses research from the last few years relating to windborne debris risk models and the essential elements of engineering damage prediction models. Generic types of windborne debris are discussed. The results of studies of debris trajectories that are relevant to damage models are described - in particular the horizontal component of debris velocity as a function of distance travelled. The merits of impact momentum versus impact kinetic energy as a relevant parameter for predicting damage are considered, and how published data from generic cannon Impact tests can be used in risk models. The quantitative variation of debris impact damage with wind speed is also discussed. Finally the main elements of previously-proposed debris damage models are described.

Windborne debris risk analysis - Part I. Introduction and methodology

Windborne debris is a major cause of structural damage during severe windstorms and hurricanes owing to its direct impact on building envelopes as well as to the \'chain reaction\' failure mechanism it induces by interacting with wind pressure damage. Estimation of debris risk is an important component in evaluating wind damage risk to residential developments. A debris risk model developed by the authors enables one to analytically aggregate damage threats to a building from different types of debris originating from neighboring buildings. This model is extended herein to a general debris risk analysis methodology that is then incorporated into a vulnerability model accounting for the temporal evolution of the interaction between pressure damage and debris damage during storm passage. The current paper (Part I) introduces the debris risk analysis methodology, establishing the mathematical modeling framework. Stochastic models are proposed to estimate the probability distributions of debris trajectory parameters used in the method. It is shown that model statistics can be estimated from available information from wind-tunnel experiments and post-damage surveys. The incorporation of the methodology into vulnerability modeling is described in Part II.

Windborne debris risk analysis - Part II. Application to structural vulnerability modeling

The 'chain reaction' effect of the interaction between wind pressure and windborne debris is likely to be a major cause of damage to residential buildings during severe wind events. The current paper (Part II) concerns the quantification of such pressure-debris interaction in an advanced vulnerability model that integrates the debris risk model developed in Part I and a component-based wind-pressure damage model. This vulnerability model may be applied to predict the cumulative wind damage during the passage of particular hurricanes, to estimate annual hurricane losses, or to conduct system reliability analysis for residential developments, with the effect of windborne debris fully considered.

The vulnerability of residential window glass to lightweight windborne debris

This paper presents the results of an experimental investigation of the momentum threshold required to damage residential window glazing when impacted by roof shingles and wooden dowels. Shingles are among the most common sources of debris in hurricane winds, and they have been observed to be a major contributor to the breach of windows. Wooden dowels represent lightweight vegetation type windborne debris (e.g., twigs, branches). Custom launching apparatuses were constructed to achieve controllable and repeatable flight modes and speeds for the debris. More than 600 annealed residential window glass specimens were tested to quantify the momentum threshold and damage accumulation. The shingle impact experiments were conducted using varying shingle sizes, flight modes, impact angles, shingle age, impact speeds, glass specimen thicknesses, dimensions, and edge boundary conditions. The wooden dowel impact experiments include varying wooden dowel diameters and angles of impact. Vulnerability curves are provided for unprotected window glass as a function of momentum, debris type, flight mode, and angle of impact.

飛散物の種類と発生要因

飛散物の種類と発生要因

飛散物の発生防止と防御

飛散物の発生防止と防御

風による飛散物の軌跡の解析

風による飛散物の軌跡の解析

飛散物の被害事例と風洞実験

飛散物の被害事例と風洞実験

Numerical calculation of the three-dimensional motion of wind-borne debris

Most previous studies of wind-borne debris have only considered two-dimensional (2D) motion. While this can demonstrate many basic principles, it is a special case that is unlikely to occur in a real storm situation. In these 2D cases, the normal force coefficient and the position of the centre of pressure are only functions of the angle of attack. In addition, the centre of pressure is always located on the plane of symmetry. In the present study, rectangular plates with side length ratios of 1, 2 and 4 and long rods with sectional side length ratios of 1, 2 and 3 were wind tunnel tested at a range of angles of attack and tilt angles. The results clearly show that the force coefficients depend on both of these angles. Further it is shown that the centre of pressure moves both towards and across the wind. A model for this movement is presented. A 6-degree-of-freedom (6-DoF) trajectory model is presented, which makes use of the measured forces and the model for the centre of pressure position. This programme also incorporates damping terms and hysteresis effects due to dynamic stall and apparent camber. It is shown that the computed trajectories reasonably match those observed with model plates and rods in free flight. The trajectory model is used to predict the three-dimensional motion of full-scale plates. It is shown that this motion includes significant lateral movement and that horizontal speeds very close to, or even exceeding, the wind speed are predicted.

Windborne debris risk assessment

A probabilistic model, based on Poisson random measure theory, is developed for predicting windborne debris damage in residential areas. It is intended for incorporation into improved methodology to estimate economic losses due to hurricanes to individual houses or entire residential developments. A sample application to a coastal housing development is provided.

Wind-missile impact capacity of essential facilities

Windborne debris during a hurricane may cause damage to building façades, resulting in significant economic losses and injury or death. Recent building codes have adopted variations of the large-wind-missile impact test in order to certify roof/wall components for hurricane resistance. The purpose of this study was to investigate the performance of commonly used Florida wall and roof assemblies under enhanced large-wind-missile impact testing, beyond the basic test specified in the Florida Building Code. Relevant standards specify similar enhanced standards for essential facilities and shelters. Based on a thorough literature review, a list of wall and roof assemblies that had not been tested before was selected. Wall assemblies included wood and metal framing systems and concrete panels. Roof assemblies included metal framing systems and concrete panels. A comprehensive list of wall and roof assemblies that passed the enhanced test was developed. Assemblies that should be avoided in the construction of essential facilities were also noted.

Trajectories of Wind-Borne Debris in Horizontal Winds and Applications to Impact Testing

This paper considers the trajectories of compact and rod-type wind-borne debris in horizontal winds, using a combination of experimental and numerical studies. These types are representative of the roof gravel and timber members currently used for testing building facades and storm shutters. These studies indicate that the ratio of horizontal debris speed to wind gust speed is primarily a function of the horizontal distance traveled by the debris as it accelerates toward the wind speed. Empirical expressions to approximate the horizontal speed of these debris as a function of travel distance and time are developed, and may be used to establish rational debris impact criteria.

Preliminary report on damage in Nobeoka City due to tornado accompanying typhoon Shanshan (T0613)

On September 17, 2006 serious damage had been caused by tornado accompanying Typhoon Shanshan (T0613) at Nobeoka City, Miyazaki Prefecture. Due to the gust the first and the second cars of a limited express train cars were overturned. More than a thousand houses were damaged. Three people were killed. The notable feature of this wind damage was impact of wind borne debris. The estimated damage scale was F2 and the maximum gust speed of 46m/s was observed at a factory yard. The area of damage footprint was spread to 7.5 km from Pacific coast to the north-east by 100m to 200m in width. Results of the site investigations were reported.

Large Wind Missile Impact Capacity of Residential and Light Commercial Buildings

Past hurricanes such as Andrew and the recent spate of hurricanes in Florida and elsewhere have shown the potential and extent of structural damage due to windborne debris during such storms. The loss of building exterior envelope and the subsequent structural damage to buildings due to such debris impact can be significant. Recent building codes have incorporated wind missile impact criteria for the roof and wall assemblies of coastal buildings. In this study, typical wall and roof assemblies for Florida residential and light commercial coastal construction were identified. In conjunction with a review of prior large wind missile testing results, assemblies that are yet to be tested were tabulated. These assemblies were tested for the Florida Building Code (FBC) large wind missile impact criteria. Based on the test results, a comprehensive list of wall and roof assemblies that passed the FBC test was developed. Also recommended were assemblies that should be avoided for the construction of residential an...

Curtain Wall Designs for Wind and Blast: Three Case Studies

Current design for curtain walls subjected to wind, wind-borne debris, and blast contain relatively new structural requirements for the curtain wall designer to address. These new criteria are defined and discussed in application to three case studies of curtain wall systems. The case studies illustrate the impact of these criteria on modern curtain wall designs and offer conclusions regarding the process and impact of designing curtain walls to current standards. It is concluded that projects in hurricane regions require fairly stout deigns and can withstand moderate blast loads. Wind tunnel testing remains a viable option to define design load criteria. Even low-rise building projects in high-velocity wind zones can benefit from wind tunnel modeling due to more precise and often reduced design pressures.

HAZUS-MH Hurricane Model Methodology. I: Hurricane Hazard, Terrain, and Wind Load Modeling

An overview of the hurricane hazard model, terrain model, wind pressure, and windborne debris models used in the HAZUS-MH hurricane model is presented. These models represent the first three of five major component models used in HAZUS for the prediction of damage and loss to buildings subjected to hurricanes. The five model components are the hurricane hazard model, terrain model, wind load model, physical damage model, and loss model. These models have been validated, wherever possible, through the use of historical data for landfalling hurricanes, wind tunnel test results, field observations of hurricane induced damage and insurance loss data. The HAZUS hurricane model represents an advancement in the state-of-the-art over other hurricane loss prediction models in that it estimates wind induced loads, building response, damage and loss, rather than simply using historical loss data to model loss as a function of wind speed.

Adoption of the International Residential Code in a High Natural Hazards Region—An Overview

South Carolina was among the first jurisdictions to adopt the 2000 International Residential Code (IRC). The adoption of this statewide building code met with significant opposition and resulted in moratoria being placed on all seismic design and wind-borne debris provisions in the code. A study was conducted to determine how well the IRC has been adopted by coastal South Carolina communities, with the discovery that most plan preparers and building departments are not following the IRC. This paper documents some of the activities and observations made during this process. The observations are troubling and point to a significant need for ongoing professional education. The findings also demonstrate the need for greater resources to be allocated not only to educational needs, but also to code enforcement.

Investigation of plate-type windborne debris. Part I. Experiments in wind tunnel and full scale

Modeling of the trajectory of windborne debris for incorporation in wind hazard risk assessment requires the knowledge of debris aerodynamics. On-going experiments to determine the flight characteristics of various types of debris are being carried out in the Texas Tech University (TTU) wind tunnel. This paper investigates the aerodynamic characteristics of plate-type debris. Useful data are presented in dimensionless form. Empirical expressions for estimating the horizontal flight speed and distance are derived. Results from wind-tunnel experiments are in reasonable agreement with those from full-scale tests. These results can be used to validate numerical calculations of trajectories of plate-type windborne debris.

Tachikawa number: A proposal

This paper describes the studies of windborne debris by Masao Tachikawa and shows that a parameter defined by him, representing the ratio of aerodynamic to gravity forces, is the main non-dimensional parameter determining the trajectories of debris items of all types. A case for naming this parameter as the “Tachikawa Number’’ is made.

Hurricane Wind Shelter Retrofit Room Guidelines for Existing Houses

The objective of this study was to develop design and construction techniques for an in-home hurricane room shelter, which is an alternative to the Federal Emergency Management Agency (FEMA) tornado safe room. Such a room will be able to withstand hurricane or tornado wind speeds up to 225 km∕h (140 mph) and associated windborne debris. Structural calculations for known material strengths, expected wind pressures, and missile impact capacity from previous research were used as the basis for the hurricane room technology. The retrofitting is achieved through reinforcing existing walls and roofs of typical small interior rooms with plywood sheets, steel plates, anchor bolts, hurricane straps and impact resistant doors. The in-house shelter, which can also be constructed as a stand-alone unit, will offer significant occupant protection and reduce the demand on public shelters in the event of mid-Category-4 hurricane. The total cost of a hurricane room is about $3,000 including readily available materials and...