Seismic Movements

Mitigation Strategies, Case Studies, Parametric Analyses

Overview

Authors

Photo of Gijs Libourel

Gijs Libourel

Senior Associate

Thornton Thomasetti

glibourel@ThorntonTomasetti.com

Daniel Segraves

Thornton Thomasetti

dsegraves@ThorntonTomasetti.com


Keywords


Abstract

A common building upgrade to add value to existing commercial real estate is the renewal of the entrance lobby. The lobby facade is replaced to give the building a contemporary or less dated appearance. Under seismic loads the existing building structure undergoes significant inter-story drift. The existing facade generally can’t accommodate the level of deformation that comes with the inter-story drift, while the new facade should. Therefore the interface between existing facade and new facade need design attention from both an engineering and an architectural point of view.

The required structural performance for the new facade system is driven by an allowable limit on the damage to the facade elements resulting from elastic building movements due to seismic activity, and an allowable limit to the damage to the facade elements resulting from in-elastic building movements due to seismic.

Varying movement strategies are discussed for both the new facades and the interfaces to the existing building and provides case studies that demonstrate the applicability of the movement strategies. Standard movement joints can be unsightly and hard to incorporate into the Architecture in an elegant way.

Conclusions are that addressing seismic design criteria for facades from the start of the design process helps to apply an effective mitigation strategy; and that when addressed timely and with rigor the story drift requirements of seismic events do not prevent an elegant facade design that meets both the Architectural design and the budget requirements.

Introduction

A common building upgrade to add value to existing commercial real estate is the renewal of the entrance lobby. The façade is often replaced to give the building a contemporary

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Building Movements

The primary structure of a building moves during a seismic event. The new lobby façade movement and the movement of the existing structure have to be compatible throughout the seismic

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Mitigation Strategies

Once the existing base building movements are either assumed or determined based on (modal) analysis, the new façade of the lobby can be designed while accounting for the anticipated elastic

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Case Studies

350 South Grand Avenue

The project is a single story glass façade with an intermediate parapet structure. The existing structure is a moment frame building erected in 1990 and the

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Conclusion and Future Work

The following conclusions can be drawn:

Seismically driven story drift is specifically addressed in the Building Code, both in probability and numerical values.Pass/fail criteria for glazing during seismic events is

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