Staggered truss system
Encyclopedia
The Staggered truss system is a type of structural steel framing used in high-rise buildings. The system consists of a series of story-high trusses spanning the total width between two rows of exterior columns and arranged in a staggered pattern on adjacent column lines. William LeMessurier
, the founder Cambridge, Massachusetts
engineering firm LeMessurier Consultants
has been credited in developing this award winning system as part of his research at the Massachusetts Institute of Technology
.
's Departments of Architecture and Civil Engineering in the 1960s by U.S. Steel. The research attempted to achieve the same floor-to-floor height with steel as you could with flat plate concrete. The system was presented at the 1966 AISC Conference (the predecessor to the current North American Steel Construction Conference). Additional benefits discovered were high resistance to wind loads and versatility of floor layout with large column-free areas.
It has been used with on a number of LeMessurier Consultants
work in hotels including Lafayette Place Hotel in Boston and the Aladdin Hotel in Las Vegas
. Other locations that use this system include the Resorts International
Hotel in Atlantic City, New Jersey
, Embassy Suites hotel in New York City, Baruch College
Academic Center in New York City, Trump Taj-Mahal in Atlantic City NJ, and the Renaissance Hotel in Nashville TN
trusses in a staggered pattern at alternate column lines provide large column-free areas for room layouts. These column free areas can be utilized for ballrooms, concourses, and other large areas.
The staggered truss structural system consists of story-high steel trusses placed on alternating column lines on each floor so that the long axis of one truss is always between the trusses on the floor below. The system staggers trusses on a 12’ module, meaning that on any given floor the trusses were 24’ apart.
The interaction of the floors, trusses, and columns makes the structure perform as a single unit, thereby taking maximum advantage of the strength and rigidity of all the
components simultaneously. Each component performs its particular function, totally dependent upon the others for its performance.
The total frame behaves as a cantilever beam when subjected to lateral loads. All columns are placed on the exterior wall of the building and function as the flanges of the beam, while the trusses which span the total transverse width between columns function as the web of the cantilever
beam.
While earlier staggered truss systems utilized channels for web diagonals and verticals, today most of the trusses are designed with hollow structural sections (HSS) for vertical and diagonal members because they are more structurally efficient and easier to fabricate. The trusses are fabricated with camber to compensate for dead load and are transported to the site, stored and then erected—generally in one piece.
Fabrication of this type of structure requires certified welders and overhead cranes capable of lifting 10 to 15-ton trusses and columns for projects up to 20 stories. Fabrication involves the following components: Columns, Spandrel Beams, Trusses, Secondary Columns & Beams and the Floor System.
William LeMessurier
William James LeMessurier was a prominent American structural engineer.Born in Pontiac, Michigan, LeMessurier graduated with an AB from Harvard, went to Harvard Graduate School of Design and then earned a master's degree from Massachusetts Institute of Technology in 1953. He was the founder and...
, the founder Cambridge, Massachusetts
Cambridge, Massachusetts
Cambridge is a city in Middlesex County, Massachusetts, United States, in the Greater Boston area. It was named in honor of the University of Cambridge in England, an important center of the Puritan theology embraced by the town's founders. Cambridge is home to two of the world's most prominent...
engineering firm LeMessurier Consultants
LeMessurier Consultants
LeMessurier Consultants is a Cambridge, Massachusetts firm, founded by William LeMessurier in 1961. It provides engineering support services to architects and construction firms. They focus on advanced structural techniques and impacts to construction materials...
has been credited in developing this award winning system as part of his research at the Massachusetts Institute of Technology
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
.
History
The staggered truss system came about due to sponsored research at Massachusetts Institute of TechnologyMassachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
's Departments of Architecture and Civil Engineering in the 1960s by U.S. Steel. The research attempted to achieve the same floor-to-floor height with steel as you could with flat plate concrete. The system was presented at the 1966 AISC Conference (the predecessor to the current North American Steel Construction Conference). Additional benefits discovered were high resistance to wind loads and versatility of floor layout with large column-free areas.
It has been used with on a number of LeMessurier Consultants
LeMessurier Consultants
LeMessurier Consultants is a Cambridge, Massachusetts firm, founded by William LeMessurier in 1961. It provides engineering support services to architects and construction firms. They focus on advanced structural techniques and impacts to construction materials...
work in hotels including Lafayette Place Hotel in Boston and the Aladdin Hotel in Las Vegas
Las Vegas, Nevada
Las Vegas is the most populous city in the U.S. state of Nevada and is also the county seat of Clark County, Nevada. Las Vegas is an internationally renowned major resort city for gambling, shopping, and fine dining. The city bills itself as The Entertainment Capital of the World, and is famous...
. Other locations that use this system include the Resorts International
Hotel in Atlantic City, New Jersey
Atlantic City, New Jersey
Atlantic City is a city in Atlantic County, New Jersey, United States, and a nationally renowned resort city for gambling, shopping and fine dining. The city also served as the inspiration for the American version of the board game Monopoly. Atlantic City is located on Absecon Island on the coast...
, Embassy Suites hotel in New York City, Baruch College
Baruch College
Bernard M. Baruch College, more commonly known as Baruch College, is a constituent college of the City University of New York, located in the Flatiron district of Manhattan, New York City. With an acceptance rate of just 23%, Baruch is among the most competitive and diverse colleges in the nation...
Academic Center in New York City, Trump Taj-Mahal in Atlantic City NJ, and the Renaissance Hotel in Nashville TN
Description
The staggered truss system for steel framing is an efficient structural system for high-rise apartments, hotels, motels, dormitories, and hospitals. The arrangement of story-hightrusses in a staggered pattern at alternate column lines provide large column-free areas for room layouts. These column free areas can be utilized for ballrooms, concourses, and other large areas.
The staggered truss structural system consists of story-high steel trusses placed on alternating column lines on each floor so that the long axis of one truss is always between the trusses on the floor below. The system staggers trusses on a 12’ module, meaning that on any given floor the trusses were 24’ apart.
The interaction of the floors, trusses, and columns makes the structure perform as a single unit, thereby taking maximum advantage of the strength and rigidity of all the
components simultaneously. Each component performs its particular function, totally dependent upon the others for its performance.
The total frame behaves as a cantilever beam when subjected to lateral loads. All columns are placed on the exterior wall of the building and function as the flanges of the beam, while the trusses which span the total transverse width between columns function as the web of the cantilever
Cantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...
beam.
While earlier staggered truss systems utilized channels for web diagonals and verticals, today most of the trusses are designed with hollow structural sections (HSS) for vertical and diagonal members because they are more structurally efficient and easier to fabricate. The trusses are fabricated with camber to compensate for dead load and are transported to the site, stored and then erected—generally in one piece.
Fabrication of this type of structure requires certified welders and overhead cranes capable of lifting 10 to 15-ton trusses and columns for projects up to 20 stories. Fabrication involves the following components: Columns, Spandrel Beams, Trusses, Secondary Columns & Beams and the Floor System.
Advantages
- Large clear span open areas for ballrooms, or other wide concourse are possible at the first floor level, because columns are located only on the exterior faces of the building. This allows for spaces as much as 60 feet in each direction with columns often only appearing on the perimeter of a structure. This also increases design flexibility especially for atrium placement and open space floor plans.
- Floor spans may be short bay lengths, while providing two column bay spacing for room arrangements. This results in low floor-to-floor heights. Typically, an 8'-8" floor-to-floor height is achieved.
- Columns have minimum bending moments due to gravity and wind loads, because of the cantilever action of the double-planar system of framing.
- Columns are oriented with their strong axis resisting lateral forces in the longitudinal direction of the building.
- Maximum live load reductions may be realized because tributary areas may be adjusted to suit code requirements.
- Foundations are on column lines only and may consist of two strip footings. Because the vertical loads are concentrated at a few column points, less foundation formwork is required.
- Drift is small, because the total frame is acting as a stiff truss with direct axial loads only acting in most structural members. Secondary bending occurs only in the chords of the trusses.
- High strength steels may be used to advantage, because all truss members and columns are subjected, for all practical purposes, to axial loads only.
- A lightweight steel structure is achieved by the use of high strength steels and an efficient framing system. Since this reduces the weight of the superstructure, there is a substantial cost savings in foundation work.
- Faster to erect than comparable concrete structures. Once two floors are erected, window installation can start and stay right behind the steel and floor erection. No time is lost in waiting for other trades, such as bricklayers, to start work. Except for foundations, topping slab, and grouting, all "wet" trades are eliminated.
- Fire resistance; steel is localized to the trusses, which only occur at every 58-to-70-feet on a floor, so the fireproofing operation can be completed efficiently. Furthermore, the trusses are typically placed within demising walls and it is possible that the necessary fire rating can be entirely by enclosing the trusses with gypsum wallboard. Finally, if spray-on protection is desired, the applied thickness can be kept to a minimum due to the compact nature of the truss elements.