This Day in Severud History

The Museum of Automobiles, Morrilton, AR

Summer is winding down but September is still a great time of year to hit the open highway. Road trips are a favorite American pastime and there is no shortage of attractions to discover along the way. Those traveling around Little Rock, Arkansas, may want to stop by the Museum of Automobiles, located near Petit Jean Mountain State Park, where they can learn some of the history of the vehicles that brought them there. Although modest in size at about 150 ft by 150 ft, the museum houses 50 vintage cars, thanks to its column-free interior. In the fall of 1960–almost 66 years ago–Severud Associates was retained to assist with the design of the cable-supported roof that made this possible.

Distinctive–and Artistic–Framing

The one-story museum has a single cellar that is used for a mechanic’s shop, among other purposes. The display floor, framed over the cellar at ground level, is constructed of concrete slabs and beams, supported on a grid of concrete columns–none of which extend above the floor–and perimeter concrete walls. At the corners, massive concrete buttresses, formed by walls in a beveled “L” shape, extend to a height of about 35 ft. Equally spaced along each wall, four pairs of slender precast concrete columns reach the same height. The buttresses are capped by large concrete blocks, between which precast concrete tie beams span over the perimeter columns. Precast concrete spandrel beams also frame the perimeter at about the mid-height of the columns to form the edge of the roof.

The smoothly contoured roof looks like a huge bedsheet held up at its four corners and draping under its own weight to a low point in the center. Ridge lines slope steeply from the top of the corner columns and down to the center, in a giant “X” configuration, while the valleys, framed with continuous steel beams, slope slightly down from the center to a concrete column or pilaster at the midpoint of each side, forming an equally gigantic “+” sign. In each triangular sector–formed by one side of the roof and two adjacent ridges–six steel cables splay out from the top of one corner buttress, pass through holes in a leg of the valley member, and converge back to the adjacent corner buttress, for a total of 24 cables. The roof framing plan, with four sets of chevron-shaped cables and rectilinear valleys and purlins, could be mistaken for a work of Op Art, which was very popular at the time.

An Intricate System in Delicate Balance

The intricate arrangement of buttresses, columns, cables, and beams generates a complex set of internal forces. Tension in the cables delivers the gravity loads to the four corner buttresses and, thence, the foundation. The cables also induce substantial lateral loads in the principal horizontal axes. These lateral loads are resisted by compression in the perimeter tie beams, which allows the forces at adjacent column tops to balance each other. The tie beams are composed of three parallel members, with spaces between them about equal to the individual beam widths, which makes them appear less massive than would a single solid beam. The three beams are tied together at short intervals for stability. Tension in the valley members balances the induced lateral load at the bend in each cable.

Framing of the diaphragm had to accommodate the roof’s curvature. Closely spaced glulam purlins span between cables and spandrel beams and were spliced as needed; the purlins are tied together where they meet at right angles at the ridge lines and support wood ridge members. Over the purlins, valleys, and ridges, wood decking and sheathing creates a continuous roof surface. Most of the roof is protected with a waterproof membrane while the portion between the outermost cables and the spandrel beams is clad in copper sheet. The undulating shape, varied materials, and exposed structural elements give the roof a distinctive appearance, both inside and out. The building was added to the National Register of Historic Places in 2019.

Severud Associates has provided innovative structural analysis and design for many museums, including the relocation and expansion of the Barnes Foundation in Philadelphia, PA; the Museum of Modern Art Expansion in New York City; and the National Museum of the American Indian in Washington, DC. Other iconic cable-supported roofs include the J.S. Dorton Arena in Raleigh, NC; Madison Square Garden in New York City, and the Jeppesen Terminal Roof at Denver International Airport. The firm’s engineers use their broad expertise, deep experience, and keen aesthetic sense to create structures that are artful enough to be in any museum’s collection.

Sphere Casting Light on a Smart Solution

Early collaboration and integrating casting expertise into the design process from the start ensures that components align with architectural and structural goals. Having all key stakeholders from Sphere’s design-construct team, structural engineer Severud Associates, architect Populous, steel fabricator W&W | AFCO Steel, casting manufacturer Cast Connex, and erection engineer SDL, was instrumental in guaranteeing success.

Sphere awarded 2025 Ideas2 Presidential Award for Engineering Design and Construction from AISC

THE LARGEST SPHERICAL STRUCTURE IN THE WORLD is a display of groundbreaking steel innovation that has helped redefine the immersive entertainment experience. Sphere, the next-generation music and performing arts venue just east of the Strip in Las Vegas, is a 516-ft-diameter semi-spherical building rising 366 ft above ground. It encloses a bowl-shaped theater for 17,600 guests seated beneath a domed roof and a suspended media plane.

Penn2 Redevelopment awarded 2025 Ideas2 Excellence in Engineering from AISC

A MIDTOWN MANHATTAN OFFICE BUILDING needed a boost from its original 1960s form, and its steel frame lent itself to adaptation and longevity despite its age.

New steel elements incorporated at PENN 2 created a 75-ft by 450-ft addition called the Bustle that hovers 50 ft above the sidewalk on 14 dramatically sloped columns configured around an existing trainshed. Creative connections ensured the existing structure an addition do not transfer significant lateral load to each other.

CFG Bank Arena Renovation

The 60-year old CFG Bank Arena underwent a $200 million renovation that transformed the aged facility into a state-of-the-art music, sports, and entertainment venue. Originally opened in 1962, the downtown arena has been host to many events, including music, boxing, wrestling, and other sports, and is currently hosting the Central Intercollegiate Athletic Association (CIAA) men’s and women’s basketball tournaments through 2025.

TSX – Magic on Broadway

Times Square in New York is known for many things, including its Broadway Theaters, luxurious hotels, trendy retail, great entertainment venues, and flashy billboards. In the case of TSX Broadway (1568 Broadway), the project contains all these items in one building. What makes TSX Broadway truly special is not just that it contains all the elements of Times Square in one location. How existing elements were shifted, assembled, and juxtaposed with new elements makes this Entertainment complex and hotel tower a unique structural engineering feat.

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Inside the 6 most fascinating, innovative reconstruction projects in NYC

The rat’s nest of regs that is city zoning may stymie construction, redevelopment and conversion projects — but in the hands of the right visionary architects and engineers, zoning can also produce truly innovative outcomes.  Here’s a look at some of NYC’s most fascinating extreme makeovers making their debuts right now.

DDC Journal, Fall 2023 Issue

Page 66 PANYNJ / JFK REDEVELOPMENT PROJECT

In coordination with a tremendous team of financiers, airlines, designers and contractors, the Port Authority of New York and New Jersey (PANYNJ) is making headway on a $19 billion investment program to modernize and expand New York’s John F Kennedy International Airport (JFK).  Click image to read more…

Page 86 CFG BANK ARENA

Despite being the largest city in Maryland, Baltimore was without a large, high-end venue or sports concerts and other live entertainment for many years.  The existing City-owned Baltimore Area was often passed over by major tours due to structural limitations.  Click image to read more…

Louis Armstrong Center

More than fifteen years in the making, the Louis Armstrong Center is the final piece of the campus of the Louis Armstrong House Museum in the neighborhood of Corona, Queens, where jazz great Louis Armstrong lived for nearly thirty years. Caples Jefferson Architects answered a few questions about their design of the recently inaugurated Louis Armstrong Center.

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The Garnet, 1620 Fulton Street, Brooklyn

Named after the jewel-toned accent color punctuating its façade and lobby, the Garnet is a new mixed-income multi-family building located in the Bedford-Stuyvesant neighborhood in Brooklyn. The 15,000 square foot project site was formed through the combination of vacant city-owned property with privately-owned small lots, which when unified allowed for 103 affordable apartments to be added to this thriving neighborhood. An ample lobby and large storefront windows along the entire length of the building’s base activate the lively and eclectic commercial corridor, Fulton Street, with retail spaces that enliven the streetscape. In addition to providing high quality housing and retail space, the Garnet is designed to promote the well-being of its residents as is reflected with a fitness center, playroom, and landscaped roof terrace.

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