Retrofit Options for Historic Facades

Analysis and Design of Coil Drapery Catcher Systems

Overview

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Abstract

Building design criteria requires that government buildings be designed for a variety of extreme loads including blast, hurricane, and impact conditions. The main goal of blast-resistant window and wall design is to minimize hazardous debris to prevent human injury and minimize the response of load-bearing members to prevent progressive collapse and human fatalities. New buildings can utilize hardened facade systems designed for extreme loads. However, retrofit design of existing buildings can be more challenging—especially when historic buildings are involved. Retrofit of historic buildings requires that original facades remain as much as possible. Therefore, interior retrofits must be utilized that provide the required thermal and energy efficiency, in addition to resistance to extreme loads.

Retrofit options for windows include anti-shatter films, storm windows with laminated glass, (fabric) blast curtains, and glazing cable or bar catcher systems. Another option is use of a heavy-duty curtain as a facade catcher system. A Cascade Coil Drapery product was designed for use as a catcher retrofit for a curtainwall system. Shock tube tests had been conducted and were used to validate modeling techniques employed to represent material-level and structural-level response modes of the woven coil drapery. After validation, finite element models (using LS-DYNA) were utilized to create resistance functions for different Cascade Coil products in this application. Variables included: coil orientation, coil gauge, coil pitch, connection type, and span. The resistance functions (or load vs deflection curves) were used in the Single-degree-of-freedom Blast Effects Spreadsheet (SBEDS) distributed by the US Army Corps of Engineers Protective Design Center (USACE PDC). The fast running models allowed for quick evaluation of all retrofits subjected to all applicable blast loads for a “mock” entry curtainwall in a representative 1930’s to early 1940’s government building. Connection design to existing structural systems was also considered during the design process. An explanation of the model validation and selected Cascade Coil drapery system for this application is provided.

Introduction

Unlike conventional loads, extreme loads, particularly blast-induced loads, generate structural demands that are difficult to resist through elastic response alone. Consequently, with the exception of critical government facilities, most structures

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Background

As an alternative to a new hardened façade, catcher systems are capable of protecting building occupants from hazardous debris by arresting failed façade components before they penetrate too far into

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Objective

To demonstrate the viability of coil mesh curtains as curtainwall catcher systems, a mock design was performed in the present study considering several coil mesh alternatives. The selected sample

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Methodology

A woven coil mesh curtain is a relatively novel material for a façade catcher system. Consequently, little information is available in published literature regarding performance characteristics and important structural response

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Model Development

As described previously, the first phase of the present study involved the development of a high-fidelity finite element model of a Cascade Coil Drapery system. Accordingly, detailed material models for

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Model Validation

Modeling techniques refined using the approach described above were used to develop a full-scale model of a Cascade Coil Drapery catcher system that was previously tested at the University of

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Retrofit Design

Following development and validation of high-fidelity numerical techniques for modeling coil mesh systems subjected to blast-induced loading, such techniques were simplified and adapted to develop general-purpose resistance functions. These resistance

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Performance Advantages Compared to Conventional Systems

In addition to coil mesh catcher systems, conventional retrofit options for historic curtainwall facades include façade replacement, a secondary window wall system with laminated glass, and glazing cable catcher systems

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Summary and Conclusions

In the present study, a conceptual coil mesh catcher system was developed for a mock structure to arrest a failed façade subjected to blast loads. To form the basis for

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Acknowledgements

The authors would like to acknowledge Cascade Coil Drapery for sponsoring the present study.

Rights and Permissions

ASTM. 2017. F1642/F1642M-17, Standard Test Method for Glazing and Glazing Systems Subject to Airblast Loadings. West Conshohocken, PA: ASTM International.

Castonguay, S., E. Jacques, and M. Saatcioglu. 2015. Blast Testing of GuardianCoil as a Protection System. Ottawa, Ontario, Canada: University of Ottawa.

Cowper, G.R., and P.S. Symonds. 1958. Strain Hardening and Strain Rate Effects in the Impact Loading of Cantilever Beams. Brown University, Applied Mathematics Report.

Marchand, K., Davis, C., Sammarco, E., and Bui, J. 2017. "Extending Glass Facade Performance Predictions for Natural and Man-made Hazards Using Accesible High-Fidelity Formulations." 39th IABSE Symposium. Vancouver, Canada.

U.S. Department of Defense. 2013. "DoD Minimum Antiterrorism Standards for Buildings (UFC 4-010-01)."

U.S. Department of Defense. 2014. "Structures to Resist the Effects of Accidental Explosions (UFC 3-340-02)."