Home ⁄ Articles (page 15)

The Devil in the Details

Structural design considerations for rooftop equipment platforms.

Supporting rooftop mechanical or electrical units is a simple problem with a complicated solution. While some units are small and light enough to bear on the roof with minimal additional support, many require supplemental structural roof framing. Depending on the building structural system below, the units may be supported on a pad or curbs, sleepers or loose dunnage, or raised platforms. Typically, the term dunnage has been used interchangeably with raised platforms. Still, it is more accurate to say that dunnage consists of loose structural members that distribute the unit’s load over the existing roof without penetrating the roof membrane. These members are not connected to existing roof structural framing.

…

Aug, 2023 By John P. Phelan, P.E. and Michael F. Hughes, P.E., S.E. In Structural Design

Enhancing Light-Frame Shear Wall Performance with Elastomeric Adhesives

A test program study.

Modern elastomeric adhesives can potentially transform the realm of light-frame wood (LFW) construction, offering a cost-effective solution to increase strength, stiffness, and energy dissipation under lateral loads induced by earthquakes and wind. LFW shear walls are integral to the lateral force-resisting system, providing a primary source of stiffness and strength to the structure by transferring loads to the foundation. The current model of shear walls dissipates energy through plastic deformation of the sheathing-frame connections, resulting in nail yielding, nail withdrawal, and sheathing edge tearing. Investigators found that conventional adhesives, including water-based, solvent-based, and polyurethane-based (PU), can significantly improve shear walls’ strength and stiffness. However, concerns about volatile emissions, lack of durability, and brittleness limit their application in LFW structures. On the other hand, silyl-modified polyether (SMP) are modern adhesives gaining interest in construction for their moisture-curing, isocyanate-free, UV-stable, chemically resistant, and high flexibility properties. This article demonstrates the efficiency and cost-effectiveness of SMP adhesive in improving the seismic performance of shear walls through an experimental program.

…

Aug, 2023 By Bilal Alhawamdeh, Ph.D., A.M.ASCE and Xiaoyun Shao, Ph.D., P.E., M.ASCE In Structural Adhesive

Climate Change and the Structural Engineer

How it may affect the profession. Part 3

Parts 1 and 2 of this series were previously published in the May and July issues of STRUCTURE. Part 1
provided a general overview of how climate change could impact an engineer’s services; Part 2 looked at the engineer’s professional standard of care. This final article looks at contractual provisions that could help to protect engineers against allegations that they failed to address climate change in their designs.

…

Aug, 2023 By Gail S. Kelley, P.E., Esq. In Legal Perspectives

Statue of Liberty National Monument

Safety renovations for the Statue of Liberty.

When Keast & Hood, Structural Engineers were contacted one day in April 2009 and asked to be at the Statue of Liberty the following Monday, the authors had yet to learn what to expect. What followed was a four-year journey that would take them to nearly every interior corner of the iconic National Monument and UNESCO World Heritage Site. That journey, with a design team led by Mills + Schnoering Architects working under the auspices of the National Park Service, resulted in significant life-safety improvements to the Monument as described in the June 2014 Structure article Designing Life Safety Renovations for the Statue of Liberty.

…

Aug, 2023 By Denise L. Richards, P.E. and Thomas J. Normile, P.E. In Iconic Structures

Temporary Structure Design

Management in the entertainment industry.

The development of the International Building Code 2024 for temporary structures goes a long way toward defining the criteria that engineers should use in design. It provides design loads and operational management plans that both the building official and structural engineer can agree on and acknowledges that performance-based criteria for a structure with a limited duration can be achieved safely. The proposed Code has also referenced the operational management plan and inspection criteria specified in ANSI E1.21-2020, “Temporary Structures Used for Technical Production of Outdoor Entertainment Events.” While it is the best of both worlds, it is only one piece of the puzzle.

…

Aug, 2023 By Kyle Kusmer, P.E. In Codes and Standards

Lessons Along the Path to Licensure

Job interviews are stressful. The interviewer and interviewee alike often play an unconscious game of chicken, each trying to second guess what the other really wants to hear. Engineering graduates and early career professionals often share their goal of attaining P.E. or S.E. licensure. Yet this is often just a rote answer because it sounds like what an employer wants to hear. Clearly, an engineering license is a critical step in a career; it leads to promotion, status, and increased responsibility. Yet, many new graduates and engineers-in-training (EITs) do not fully grasp what it will take or what it means. This is not surprising considering most firms eagerly await the chance to announce the new P.E. or S.E. within their ranks and often push passage before preparation. In lieu of pushing staff to pass an exam, the profession of structural engineering will be better served when firm leaders and mentors prepare staff members for success.

…

Aug, 2023 By Kenneth D. O’Dell, P.E., S.E. In Editorial