Influence of Performance and Design of Structural Silicone Joints on the Resilience of Curtain Wall Units Exposed to Seismic Impacts

Overview

Authors

Photo of Viviana Nardini

Viviana Nardini

Market Field Engineer Facade / Insulating Glass

nardini.viviana@ch.sika.com

Photo of Florian Doebbel

Florian Doebbel

Business Development Manager, Facades

Sika Corp.

doebbel.florian@us.sika.com


Abstract

Facade failure due to seismic event represents a potential hazard to people and can cause serious damages to buildings with consequent high-cost remedial works. As a result, interest in the design of buildings and facades to resist seismic loads and displacements has increased. Current standards and literature recognize the benefits offered by Structural Sealant Glazing (SSG) systems to enhance the performance of unitized curtain walls exposed to seismic impacts but no precise criteria are available for the seismic design of the structural silicone joints. This paper proposes a design concept to evaluate the effect of forces and displacements imposed to the structural joints due to panel seismic racking; referring to the design philosophy developed by Japanese Standard, the concept is engineered based on three performance levels associated to different design requirements, which aim at balancing costs and risks with no compromise on safety. Tensile and shear tests performed on sealant H-bars and Hockman cycle tests simulating accelerated life cycles at different deformation rates are used to exploit the deformation capability of the joints correlated to residual strengths. The comparison of different structural sealants enables an even more active use of structural silicone joints for improving the resilience of specific curtain wall units.

Introduction

Past earthquakes have focused the attention on the performance of facades and architectural glazing, revealing their seismic vulnerability. Two major concerns related to their performance during and after a seismic

Members Only

Seismic Design Requirements for Glazed Curtain Walling in Building Codes

Even if an increased attention is arising on the seismic response of glass facade systems, only limited guidelines are provided to design and evaluate architectural glazing systems exposed to earthquake

Members Only

Benefits Offered By SSG Systems in Areas Prone to Earthquake

Captured glazed systems in unitized curtain walling typically consist of glass panels retained to a main frame by mechanical means able to transfer the loads acting on the glass panels

Members Only

Concept for Seismic Design of SSG-Joints In Unitized Curtain Walling

Even if the benefits offered by SSG systems in CW exposed to earthquake are widely recognized, no official regulation currently provides clear seismic design criteria or performance levels to ensure

Members Only

Conclusions

Even if the benefits offered by Structural Sealant Glazing systems in unitized curtain walling exposed to earthquake are widely recognized, current available standards provide very poor guidelines to assess the

Members Only

Rights and Permissions

References

EN 1998-1, Eurocode 8: Design of Structures for Earthquake Resistance – Part 1: General Rules, Seismic Actions and Rules for Buildings (2004).

ASCE 7-10, Minimum Design Loads for Buildings and Other Structures (2010).

AAMA 501.6-09, Recommended Dynamic Test Method for Determining the Seismic Drift Causing Glass Fallout from a Wall System (2009).

AAMA 501.4-09, Recommended Static Testing Method for Evaluating Curtain Wall and Storefront Systems Subjected to Seismic and Wind Induced Interstorey Drift (2009).

FEMA E-74, Reducing the Risks of Nonstrcutral Earthquake Damage – A practical Guide (2012).

JASS 14, Japanese Architectural Standard Specification – Curtain wall, AIJ (1996).

ASTM C 1401-09, Standard Guide for Structural Sealant Glazing (2009).

EOTA ETAG002-1, Structural Sealant Glazing Systems – Part 1, 2012.

ASTM C 719, Standard Test Method for Adhesion and Cohesion of Elastomeric Joint Sealants Under Cyclic Movements (Hockman Cycle) (1998).

EN 12153, Curtain Walling – Air Permeability – Test Method, 2000.[12] ISO 8339, Building Construction – Sealants - Determination of Tensile Properties (2005).

Galli, U.: Seismic Behavior of Curtain Wall Facades - A Comparison Between Experimental Mock Up Test and Finite Elements Method Analysis, Politecnico di Milano (2011).

Nardini, V., Doebbel F.: Concept for Seismic Design of structural Silicone Joints in Unitized Curtain Walling. Conference Proceedings, Glass Performance Days 2015 – Tampere, Finalnd, 26-31 (2015).

Beher, R.A., Architectural Glass to Resist Seismic and Extreme Climatic Events, Woodhead Publishing Limited and CRC Press LLC (2009).

Memari, A.M., Shirazi, A.: Development of a Seismic Rating System for Architectural Glass in Existing Curtain Walls, Storefronts and Windows, 13th World Conference on Earthquake Engineering, Vancouver, Canada (2004).