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CROSS-US Newsletter 2 - September 2020

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Report Overview

Following its launch in 2019, CROSS-US continues to mature and gain momentum. Reports are flowing in, and from them our expert Panel is extracting invaluable lessons; our readership community has expanded greatly; and we have corresponded with many companies and professional organizations interested in CROSS’s mission. As an organization of the Structural Engineering Institute of ASCE, we are proud to participate in the expanding CROSS International community. The reports of this newsletter remind us of the importance of keeping structural safety top of mind through study of the continuous flow of lessons from lessor failures, near misses, and other precursors, besides the less frequent catastrophic, news-making collapses. Each case reported has insights gained before but incompletely translated into enduring improved practice. Reports US-07 and US-08 involve shortcomings in mandatory seismic retrofit projects for “soft-story” structures. Since the 1906 San Francisco earthquake, the US seismic community has done a fantastic job of learning from failures and translating those lessons into guidelines and requirements for better practice. Yet these two reports cite problems in the execution of regulations that seek to ameliorate lessons learned from the 1989 Loma Prieta earthquake. A similar example of failure to meet improved seismic regulations was previously reported in US-06. We are reminded to never relax our guard. Reports US-04 and US-14 discuss the complexities and challenges of delegated design and the associated ethical dilemmas of professional responsibility. These issues were so tragically present in the 1981 walkways collapse of the Hyatt Regency Hotel in Kansas City. US-10 describes a structural failure caused by a subsurface drainage problem. We must be ever mindful of the structural impacts of effects we may consider outside our normal purview – witness the 2017 Grenfell Tower fire disaster. Finally, US-15 involves failure of a wood truss following a “nonstructural” renovation of an existing building. The dangers of inadvertent but critical modifications of structural elements in existing buildings were revealed in the 1972 collapse of the Hotel Vendome in Boston. The success of CROSS hinges on our professional community. Please submit reports and encourage others to do so. Sign up for CROSS-US email alerts, be a student of CROSS lessons, and encourage this in your organization, so we may translate lessons into improved practice. We are interested in collaboration with other professional organizations who have interest in the mission of CROSS-US. Glenn and Andy glenn@cross-us.org | andy@cross-us.org

Overview of Reports in this Newsletter

US-04: Bottom-chord bracing for metal plate-connected wood trusses used in light-commercial applications

Concerns regarding metal plate-connected wood trusses in light-commercial construction when subject to net uplift.

US-07: Inadequate design and quality assurance on a mandatory seismic retrofit project

Tenant's structural engineer discovers widespread design and related quality problems on a mandatory seismic retrofit project.

US-08: Mandatory seismic retrofit construction with quality control problems

Standard seismic retrofit details were used for a building with non-standard foundation.

US-10: Under slab perimeter drain failure

Foundation, wall, and basement slab settlement damage due to high water table and layers of subsurface fine (sugar) sand.

US-14: Structural engineer faces ethical challenge

Engineer's professional obligations in delegated designs.

US-15: Failure of existing long-span wood roof truss following installation of new roof-top HVAC units

Failure of an existing long-span wood roof truss following installation of new roof-top HVAC units offers lessons in the special challenges of renovations to existing buildings.

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