How the Idea Got Started

Based on early ideas founded around 1990, a builder, structural engineer and structural steel contractor developed and perfected the Girder-Slab concept. The trio has over 100 years of combined construction experience.

How We Got Started

In North America, mid to high-rise residential structures are typically cast-in-place reinforced concrete offering such benefits as low floor-to-floor height and fireproof construction. With similar benefits, low to mid-rise buildings (eight stories and under) often utilize reinforced masonry bearing walls supporting precast slabs. While these structural systems have many worthy features, they are time- consuming, weather sensitive and labor intense.

For many, there has been a long-standing desire to bring the advantages of structural steel to the multi-story residential market. With the abundant use of steel for high-rise commercial structures, builders, developers and engineers have long recognized its qualities and benefits. However, until now the industry has been forced to adapt steel based systems used for commercial buildings but not ideal for residential construction. Using structural steel systems with poured concrete decks for commercial projects, it is generally difficult to achieve a minimum floor-to-floor height and requires ceilings to conceal beams, joists or deck.

Girder-Slab® Technologies, LLC set out to develop a more efficient steel based framing system for mid and high-rise residential construction. It has specifically targeted apartments, condos, retirement communities, hotels, student housing and other multi-story residential buildings.

Background

Conventional wisdom for using steel has been to maximize spans and provide universal products that fit nearly any building type. In contrast, Girder-Slab® Technologies, LLC chose a rather unorthodox approach to find a solution. First, they determined that precast slab units, common in the mid-rise residential market, combined with a steel frame could offer speed, design flexibility and value. Although residential unit modules typically vary within a floor, they generally 'stack' vertically for structural support, utilities and shafts. After considering the modular nature of residential construction, it was concluded that long-span precast slabs in combination with short span steel girders would be both appropriate and efficient. The only dilemma was to overcome the depth issue associated with a standard wide flange beam sitting below the slab.

The key was to develop a very distinctive steel girder (in combination with ordinary precast slabs) solely for multi-story residential use. Thus the Girder- Slab® System has been carefully developed to meet the precise needs associated with residential superstructures. An eight-inch thick precast hollow core slab provides for minimum floor-to-floor heights, is non-combustible, and the underside of the slab with its smooth form finish is readymade for ceiling finish. The interior support girder commonly known as a D-Beam® Girder (short for dissymmetric beam) is an inverted tee contained within the plane of the floor.

The Girder-Slab® System assembly is supported by a conventional steel frame, which resists all gravity and lateral loads. The Girder-Slab® System is fire rated as a floor-ceiling assembly when constructed in accordance with Underwriters Laboratories Inc. assembly Design No. K912 (For Canadian Projects Referer to ULC J500). With the Girder-Slab® System, a series of slabs are placed on either side of the beam web on its bottom flange. The web is completely concealed within the space between slabs, so there is no beam projecting below the slab. The void is fully grouted between slabs. After curing, the D-Beam® Girder develops composite action.

Structural Development

In Girder-Slab® Technologies' quest to perfect its composite steel and precast system, it conceived of a design that could take the place of either masonry bearing wall construction or flat plate concrete. The principals of the company, having designed and built many residential buildings with the use of conventional structural steel and precast slabs, recognized that this approach had both pros and cons. Its primary advantage was its speed when compared to cast-in-place reinforced concrete construction; the disadvantage was that rolled steel shapes beneath the floor slab necessitated an increase in the floor-to-floor height, resulting in an increased overall building height. Also, ceilings and soffits were needed to conceal the steel beams, as were accommodations to go through and around the beams for pipes and ducts.

In order to solve the floor-to-floor and interference problems, the company implemented a research and development program. It wanted an interior structural steel girder to be placed within the plane of the precast slab units, thereby producing a flat slab (akin to flat-plate) with a minimum floor to ceiling height of 8'-0". The key to this technology would be the development of an 8" steel girder, which could support the slab and span a respectable distance.

The answer came in the form of composite action between the steel and precast slab.

The Future

What lies ahead for the Girder-Slab® System are many exciting new projects featuring its use, including a variety of distinguished mid & high-rise residential buildings.

Girder-Slab® Technologies' Composite Steel and Precast System reflects the wave of the future responding to many current trends within the construction industry such as design-build, pre-engineered and pre-fabricated components, fewer on-site skilled workers, single source responsibility, and compressed time for design and procurement.

The structural steel industry has pioneered advancements to further enhance the productivity of the design and construction process. The use of interoperable software within the structural design, detailing and fabrication process has integrated the steel process resulting in lower costs and accelerated schedules. In addition, this process is fully compatible with recent trends in the design industry toward 3D Building Information Modeling (BIMs) allowing for the creation of virtual as-built drawings prior to the commencement of construction. By coordinating the various trades in advance of construction the number of interferences, conflicts, RFIs and change orders is radically reduced.

This ground breaking technological approach to the 'building process' offers a new paradigm not attainable with a cast-in-place superstructure. By its nature, cast-in- place methodology in comparison to modern day pre-fab capability is subject to many dependencies and resources difficult to manage and control, along with the impact of weather. The complexity associated with quality control and production of a "field formed and cast" superstructure is eliminated through shop-fabricated components, delivered and assembled-in-place.

This technology is available to the entire construction industry for use on mid and high-rise projects. The Girder-Slab® System Design-Guide provides all required engineering information for architects, engineers and contractors. The Girder-Slab® System components, including the D-Beam Girder, are available competitively from steel contractors along with the entire structural steel package. Now, assembly of the entire steel and concrete superstructure including slabs is available from a single source. Choose Your Own Subs.

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