Archive for ‘Enclos’

March 7, 2011

enclos

Service and Technology

Enclos is expert in the design, engineering, fabrication, assembly and erection of custom facade systems, providing complete design-build services to the construction marketplace.

We specialize in innovative architecture and challenging building projects. No project is too large, no building site too difficult for our seasoned operations teams.

Our work experience includes many projects with specialized materials, complex geometry, novel structural and mechanical system designs. Enclos curtainwall, facade and skylight systems combine innovative design with state-of-the-art materials and performance.

Our client groups are threefold:

Architect
The most comprehensive design-assist services in the industry have created a committed client base of leading architects that call on us early in the concept development phase of new projects.

General Contractor
The attributes most appreciated by our general contracting clients are our site management capabilities and a track record of meeting demanding project schedules on some of the most challenging building sites imaginable.

Developer
A long history of providing facade solutions combining top quality and performance with competitive economy has created allies of many leading developers.

Loyola University Chicago: Richard J. Klarchek Information CommonsLoyola University Chicago: Richard J. Klarchek Information CommonsLoyola University Chicago: Richard J. Klarchek Information CommonsLoyola University Chicago: Richard J. Klarchek Information Commons

Technology

1.Custom Curtainwall Systems

Enclos offers the most innovative curtainwall systems in the marketplace, combining aesthetic, performance and economic considerations into optimum solutions to our client’s needs. Our inventive unitized systems have evolved through their application on numerous major building projects to represent the state-of-the-art in curtainwall technology and performance. Sophisticated system design features and installation methods have paralleled this evolution, resulting in improved economy as well as superior performance.

What Is Curtainwall

What Is Curtainwall?

Curtainwall is a term applied to a widely used facade technology for cladding large buildings. Curtainwall systems do not carry any dead loads imposed from the building structure. They are designed to support their self-weight and to transfer horizontal loads (wind) incident upon them to the primary building structure.Curtainwall systems are typically “hung” from the building structure — from whence derives the “curtain” reference — and typically attached to the floor slabs. The primary functions of the curtainwall are to resist air and water infiltration and to provide a thermal barrier between inside and out. Curtainwall systems are also designed to accommodate the complexities of deflections, thermal expansion and contraction, building sway and relative movements between floors as caused by wind or seismic loads acting globally or locally on the structure.Special design considerations can include daylighting, thermal, acoustical, security and blast-resistant performance. Curtainwall designs for large buildings are almost always customized to individual project requirements.The craftsmanship required for AESS is a rare competency. We have developed a network of qualified AESS steel fabrication vendors, a network built over time and upon the experience of many successfully completed projects. Enclos is able to manage the delivery process in a manner that best assures predictability of outcome, thus mitigating the risk of budget overruns and schedule delays. Enclos’ QA programs fully incorporate AESS requirements.

Cladding

Cladding

Glass is the most common infill material used in curtainwall systems, but other cladding materials include metal panels, natural stone and terracotta. The curtainwall systems typically span across the floor slabs, creating a need for opaque cladding material over and in the vicinity of the floor slab to conceal the slab edge, fire-safing and any between-floor mechanical systems. A spandrel panel is often located between vision glass panels to conceal this area. To achieve opacity, spandrel glass is treated with a ceramic coating (called a frit), a film, or is incorporated into an assembly called a shadow box.Glass is used extensively as a curtainwall cladding material because of its transparency and ability to provide daylight and view. Solar gain in such applications can present challenges with respect to energy performance, thermal and visual comfort, and represent important design considerations in the development of an appropriate curtainwall facade. Ongoing research and development has positioned the Enclos team to provide optimum solutions to these challenges, and has worked with leading architects in the development of high performance glass facades on many buildings pursuing LEED certification by the US Green Building Council.Enclos has designed curtainwall systems for many LEED certified buildings

Anchorage

Anchorage

It is an exciting time for the development of advanced facade technology. At the same time, the fundamentals of sound curtainwall design have lost none of their critical import.One of the basic considerations that impacts every building project without exception is the means by which the curtainwall is anchored to the building. Anchor design can affect many things beyond the immediate curtainwall design, including the work of other trades and the design of the building interior. As with so many other aspects of the building skin, Enclos continues to lead the way with anchor design. Enclos anchor designs can be positioned on the face, top or bottom of slab, or recessed in any of these positions. The Enclos anchoring method is highly efficient, speeds field installation of the curtainwall and provides optimum economy to the building developer.Curtainwall anchors are set prior to the commencement of unit installation. If the anchors are to be recessed, they are sometimes set prior to the concrete floor slabs being poured, or provision is made for a cavity in the slab into which the anchor assembly will be installed.Our inventive unitized systems have evolved through their application on numerous major building projects to represent the state-of-the-art in curtainwall technology and performance. Sophisticated system design features and installation methods have paralleled this evolution, resulting in improved economy as well as superior performance.

Framing

Framing

Curtainwall is typically designed as cladding materials that are framed and fixed in place by extruded aluminum components. There are two basic types of systems:

  • Stick systems are built from long vertical extrusions (mullion) attached to the building structure, with shorter horizontal extrusions spanning between the vertical mullions to create the frames. Cladding materials are then installed into the frames. Extrusions may be fabricated in the shop, but all assembly, installation and glazing takes place in the field.
  • Unitized systems are a newer adaptation of curtainwall technology that has rapidly grown in use in recent years. The vertical and horizontal framing members are figuratively split, allowing independently framed “units” to be assembled and glazed in the factory. The units can be designed to span multiple floors or multiple horizontal modules, and can incorporate multiple cladding elements including operable vents and windows. The completed units are shipped to the site and simply hung on the building. Unitized systems concentrate fabrication and assembly under controlled factory rather than in the field. The selection between them is dependent upon project specific variables.

Enclos technical personnel can assist you in determining which system type is best for your particular project.

Facade Integration

Facade Integration

In addressing the challenges discussed above, and in meeting the generally escalating performance demands on the building skin, curtainwall designs have become increasingly complex. Facade system requirements now frequently include daylight harvesting, daylight and glare control, artificial lighting, and even power generation. Techniques for addressing these considerations are being integrated into the curtainwall system, providing advanced functionality to the building facade. Photovoltaic systems, shade fins, light shelves, louvers, operable blinds, sensors and multiple skins are among the things being integrated into the curtainwall system.The building community has recognized the facade as a primary means to improve energy performance and occupant comfort, and even as a potential power source.

Installation

Installation

Installation strategy is highly sensitive to specific site, schedule and coordination requirements. All Enclos operations are driven by the requirements of the building site.Unitized curtainwall systems provide optimum flexibility in this regard. Materials can be fabricated, assembled and stored offsite, and be delivered on a just-in-time basis as required to support installation crews, thus minimizing on-site storage and staging requirements on highly congested building sites. Assembled units are delivered to the site on open flatbed trailers. The units can be lifted by crane from the trailer and directly set in place on the building facade. Alternately, units can be designed to be installed from inside the building. Installation crews working from a floor above use a small jib crane to lower the units to a setting crew below. Other techniques are possible depending upon specific project requirements.Installation strategy, site logistics and operations are among the greatest strengths of Enclos, and represent the capability most valued by our general contracting clients.

2.Structural Glass Facades

A new facade technology has gradually emerged in recent decades, driven largely by the pursuit of transparency in the building facade among leading international building designers. This new technology has evolved in long-span applications, and can be categorized by the various structural systems employed as support. New glazing systems are also a part of this technology, with the various point-fixed systems finding most frequent use.

Structural Systems

Structural glass facades are most easily categorized by the structure types that support them.

1.Strongback Systems

Strongback systems comprise a remarkably diverse range of novel structural solutions in facade applications. The structural systems are built up from structural sections capable of accommodating the required span. These systems can include both vertical and horizontal structural components. Sometimes verticals are used with no horizontals. Conversely, an interesting variation of this system type eliminates the vertical mullion, with horizontal components suspended from overhead cables and fixed to anchoring building structure at their ends. Strongback systems also include hierarchical structural frames and braced frames.

Cathedral of Christ the Light
LAUSD Central LA Area High School #9
Orange County Performing Arts Center

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2.Truss Systems

Truss systems employ a planar truss design, often in a hierarchical system that may combine other element types including tension components. Truss designs vary widely, with an emphasis on fine detailing and craftsmanship. They often involve complex steel fabrications, frequently manufactured to Architecturally Exposed Structural Steel (AESS) standards. Rod or cable elements may be incorporated into the truss design, and lateral tensile systems are often used to stabilize the facade structure. Simple truss elements are often bordered by one or two cable trusses in a repeating pattern as a means to lighten the structural profile of the facade.

LA Live Tower & Residences: Podium
Eskind Biomedical Library
San Diego Convention Center
Washington Convention Center

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3.Cable Trusses

One type of truss system utilizes a minimalist structural form called a cable truss. While cable trusses can vary widely in both truss design and configuration with vertical, overhead, vaulted and domed forms easily achieved, the trusses themselves are most often characterized by spreader strut elements representing the only compression members in the structural system. As with cable nets, these systems rely on the pre-tensioning of truss elements to provide stability, and thus benefit significantly from the early involvement of the facade design/build team.

Suvarnabhumi Airport Bangkok
Lloyd D. George Federal Courthouse
San Jose Civic Center

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4.Grid Shells

Grid shell structural systems are another means to minimize the visual mass of structure. Configurations can be vaulted, domed and double-curved. Systems can be welded, bolt-up, or some combination of each. Grid shell structures with integrated cable bracing can produce a highly efficient structure with a refined aesthetic. Cable prestress is required on such systems. Grid shells can be used in vertical and overhead applications, as well as to form complete building enclosures.

Boston Courthouse
Cerner Corporate Headquarters
Desert Bloom Porte Cochere: Casino Morongo

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5.Cable Nets

Frei Otto developed and popularized cable nets as a structural system in the 1960s and 70s. Architect Helmut Jahn with engineering firm Schlaich Bergermann applied the technology in a most innovative manner in 1992 as a flat cable net supported glass facade for the Kempinski Hotel in Munich, fueling widespread interest in this structural form in glass facade applications.

Cable nets represent the ultimate in elegant minimalist structural systems and can provide optimum transparency when the effect of a sheer glass membrane is desired. The glass is supported by a net geometry of pre-tensioned cables. Designs can be flat, or the net can be pulled into double-curvature. A clamping component locks the cables together at their vertices and fixes the glass to the net. Large pre-stress loads in the net structures require the early involvement of the facade design/ build team with the building engineer.

Newseum
Richard J Klarchek Information Commons

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6.Glass Fin Systems

This is the earliest form of structural glass facade dating back to the 1950s and the French Hahn system used at the Maison de la Radio in Paris in 1953. Here 2-story glass plates were suspended and laterally stiffened by the use of glass fins set perpendicular to the plates at the vertical joints between them. This technology was popularized by the Willis Faber & Dumas Building, Ipswich, England circa 1972. In this curved facade designed by Foster Associates, multiple plates of reflective glass are suspended to provide one of the first examples of an entire building facade being skinned by frameless glass. This project inspired a diffusion of glass fin technology in numerous applications throughout Europe and America starting in the 1970s and continuing today. Glass fin-supported facades still represent one of the most transparent forms of structural glass facades and an economical solution (especially at lower spans).

Belmont Police Department and City Hall
River East Center
Shure Corporate Headquarters

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7.Glass Structures

Glass is increasingly being explored as a structural element. Glass stair treads and landings have become commonplace, and the material has even seen limited use in column and beam applications. Apple stores have explored this capacity to spectacular effect.

One of the hottest areas of glass development is in glass beams. These typically take the form of multi-ply laminates of heat-treated glass, and special structural laminates are sometimes used. The analysis and connection detailing of these components requires particular expertise. Enclos completed what is believed to be the largest single application of structural glass with the Howard Hughes Medical Center, which included the extensive use of glass beams.

Howard Hughes Medical Center
Ventura Canopy

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3.High-Performance Facade Systems

High-Performance Facade Systems

Enclos is the leader in high-performance facade systems. We were the first to design and proof a blast resistant facade system through destructive testing performed at White Sands Missile Base. We have developed and tested impact-resistant facade systems that have been approved by Miami-Dade County for use in hurricane zones. Our projects have often required the development of curtainwall systems with enhanced thermal and/or acoustical properties.

4.Art Glass Facades

Art Glass Facades

Enclos has provided art glass solutions on many high-profile building projects, often working with glass artists and architects in developing innovative designs. Our talented design team has an expertise with glass materials and processes that greatly facilitates the development of novel design solutions. Coupled with our fabrication and site operations, you cannot find a stronger, more capable team for providing art glass solutions.

see a select list of art glass projects

Glazing Systems

Framed Systems

Framed systems support the glass continuously along two or four sides. There are many variations of framed systems, most of which fall into two general categories. Conventional unitized curtain wall systems are seldom used with structural glass facades.

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Veneer

Truss systems can be designed with an outer chord of square or rectangular tubing, and may include transom components of similar material, presenting a uniform flat grid installed to high tolerances. Such a system can provide continuous support to the simplest and most minimal off-the-shelf glazing system, thus combining relatively high transparency with excellent economy. A veneer glazing system is essentially a stick-built curtainwall system designed for continuous support and representing a higher level of system integration with resulting efficiencies. Variations can include 4-sided capture, 2-sided capture, structurally glazed and unitized systems.

Orange County Performing Arts Center
Eskind Biomedical Library

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Frameless Systems

Frameless systems utilize glass panes that are fixed to a structural system at discrete points, usually near the corners of the glass panel (point-fixed). The glass is directly supported without the use of perimeter framing elements. The glass used in point-fixed applications is typically heat-treated.

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Point-fixed Clamped

Point-fixed clamped systems accomplish the point fixing without the requirement for perforations in the glass. In the case of a spider type fitting, the spider is rotated 45 degrees from the bolted position so that its arms align with the glass seams. A thin blade penetrates through the seam between adjacent pieces of glass. An exterior plate attaches to the blade and clamps the glass in place. The bolted systems present an uninterrupted glass surface, while the clamped systems expose the small exterior clamp plate. Some facade designers prefer the exposed hardware aesthetic. While the clamped systems have the potential for greater economy by eliminating the need for glass perforations, the cost of the clamping hardware may offset at least some of this savings depending upon the efficiency of the design.

51 Louisiana
LA Live Tower & Residences: Podium
Richard J Klarchek Information Commons
Shure Corporate Headquarters

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Stick

Stick-built glass facades are a method of curtainwall construction where much of the fabrication and assembly takes place in the field. Mullions of extruded aluminum may be prefabricated, but are delivered as unassembled “sticks” to the building site. The mullions are then installed onto the building face to create a frame for the glass, which is installed subsequently. Economical off-the-shelf stick curtain wall products are available from various manufacturers that may be suitable for application in structural glass facades, primarily on truss systems.

LAUSD Central LA Area High School #9
San Diego Convention Center
Washington Convention Center

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Panel/Cassette

Panel systems are typically constructed of a framed glass lite. The framed panel can then be point-supported by a supporting structural system, while the glass remains continuously supported on two or four sides. This also allows the panel to be stepped away from the support system — a practice that tends to visually lighten the facade. Panel systems can be prefabricated, benefiting from assembly under factory-controlled conditions.

Cassette systems combine properties of stick, veneer and panel systems. While variations exist, the predominant makeup of a cassette system is comprised of a primary structural mullion system, which is stick built. These provide the support and facilitate the attachment of the glass panels. The glass lites are factory assembled into minimal frames, which form an integral connection with the primary mullion system. A cassette system can be designed to be fully shop-glazed, requiring no application of sealant during field installation.

Cerner Corporate Headquarters

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Point-fixed Bolted

The most popular glass system — and frequently the most expensive — for application with structural glass facades is the bolted version. The glass panel requires perforations to accommodate specialized bolting hardware. Specially designed off-the-shelf hardware systems are readily available, or custom components can be designed. Cast stainless steel spider fittings are most commonly used to tie the glass to the supporting structure, although custom fittings are often developed for larger facade projects. The glass must be designed to accommodate bending loads and deflections resulting from the fixing method. An insulated-laminated glass panel as required for overhead applications will require the fabrication of 12 holes per panel, which can represent a cost constraint on some projects.

Cathedral of Christ the Light
Lloyd D. George Federal Courthouse
Newseum
San Jose Civic Center
Suvarnabhumi Airport Bangkok

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Weather Seal

The weather seal in most structural glass facade systems is provided by a field applied butt-glazed silicone joint. This technique provides a reliable and durable weather seal if simple procedures are followed during installation. An advantage of this sealing strategy is that any leaks, usually caused by installation errors, are easily detected and repaired. The joint design is critical, and is largely a function of the glass makeup and thickness. Compatibility between the field-applied silicone and the interlayer, if using laminated glass, or the edge seal in the case of an IGU, must be confirmed with the silicone material provider. The provider should also be consulted about the joint design. Craftsmanship is critical for the field application of the sealant to assure a visually satisfactory result.

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Other Considerations

1.Cables, Rods, Castings, and Machined Components

In addition to the glass and structural systems that comprise structural glass facade technology are the components that in turn comprise these systems — components quite unlike those typically used in exterior wall systems. The use of tensile elements in the form of steel cables and rods is a primary design strategy to dematerialize the structure and enhance the transparency of a facade design. Compression elements are frequently minimized or eliminated, and where present are crafted from cast and machined components in an elegant expression of exposed structure. The fittings and components that tie these structural members together are similarly crafted.

Here an entirely different set of material and process considerations come into play.
The Enclos design team has mastered these materials and processes as a necessary prerequisite to their appropriate application in component design. We can develop and provide custom designs of remarkable diversity in response to your particular project needs. Where appropriate, we can also source off-the-shelf components from a variety of suppliers, all carefully qualified to Enclos Corp standards and subject to our uncompromising quality assurance program. All this, from concept design through installation, as part of a single-source package from the largest national specialist in structural glass facade technology.

Cables

Bridge builder and engineer John A. Roebling first manufactured wire rope in America in the 1840’s. These materials ultimately found their way into the vernacular of architecture through such stunning works as Mathew Nowicki’s Dorton Arena of 1952 and the Ingalls Rink at Yale University of 1958 designed by Eero Saarinen. Structural glass facade technology has embraced these tensile materials as a means to minimize the structural profile of the support system. Wire rope composition, material type, finish, and end terminations are all important considerations in specifying these materials, which are available from a relatively limited number of manufacturers and specialty fabricators. Enclos Corp has put many of these manufacturers through its rigorous qualification process, resulting in several exceptional vendor/partners that have successfully provided materials on various structural glass facade projects that we have completed in recent years.

Rods

The use of steel rods as a substitute for cable in the design of structural glass facades was a practice borrowed from the yacht racing industry, and popularized in the Louvre Pyramid designed by IM Pei. The rods are most commonly fabricated from ASTM A316 stainless steel because of the material’s combination of strength and corrosion resistance. In high load applications or when super thin profiles are desired, there are other higher strength stainless options. The rod terminations are often custom designed and can be quite refined, with the intent of minimizing or eliminating any exposed threads, turnbuckle or other tensioning mechanism. Rod fabrication typically involves slipping the end fittings over the rod and upsetting the rod ends through a process called cold-heading. Alternately, equally elegant threaded fittings have also been developed. Depending upon the design of the structure, cable systems can have significant advantages over rod systems, particularly with respect to cost. However, some feel that the refined appearance of a rod system is worth a premium cost.

Casting

Casting is an ancient process with a longtime role in the construction industry, including the naming of a “cast-iron architecture” during the industrial revolution resulting from a dramatic increase in the availability of low cost cast materials. Castings were much later used to spectacular affect in the gerberettes and other components for the Center Pompidou by architects Rogers and Piano. The casting of structural components however demands a high level expertise in both the design and fabrication process. Cast nodes for the space frame structure on the Javits Convention Center in New York were famously discovered during construction to contain cracks, requiring the disassembly of nearly half the structure and a project delay of nearly two years. An intimate knowledge of the materials and processes of casting is critical to the development and implementation of a custom cast structural component. Among components appropriate for casting are spiders and glass-fixing devices, spacer struts and anchor assemblies. Various options for material and finish must be considered depending upon component design application.

Machined Components

In many respects, structural glass facade technology is more closely akin to the automotive industry than it is to conventional construction. Spider fittings are about as far from the brick as a building component can be. Structural glass facades are highly engineered structures built to very high tolerances. There is also an important visual aspect to the components because of their use in exposed structural systems. Despite a widespread pursuit of facade transparency, many designers choose to express this exposed structure in dramatic fashion, sometimes even at the expense of ultimate transparency. These factors and considerations make the use of machined components a frequent and effective choice. We design custom components or specify off-the-shelf parts as appropriate, and source both from our network of vendor/partners.

2.Architecturally Exposed Structural Steel (AESS)

The art of steel. Structural glass facades are not simply about transparency. Often the designer seeks to express the structural system supporting the facade, sometimes even at the expense of transparency. What is necessarily required here is a level of craftsmanship that extends far beyond what is found in conventional structural steel.The AISC specification for Architecturally Exposed Structural Steel (AESS) is often applied to structural glass facade designs. These designs frequently include exposed structural systems in high profile public areas, such as building lobbies and atria, and as long-span facade systems in airports, museums, and government buildings.The AESS spec is intended to provide the designer a means to control the visual quality of structural steel used in such applications. However, this specification is no panacea to the problem of communicating the requirements for visual quality such that the same expectations are shared by all relevant parties. An AESS Supplement published by Modern Steel Construction states, “Unfortunately, existing codes and standards — even AISC’s Code of Standard Practice — do not fully address the unique level of detail needed to successfully design, detail, fabricate and erect Architecturally Exposed Structural Steel (AESS).”Enclos has designed and provided many AESS structures as part of its custom facade work. We understand the demanding design, fabrication, assembly and installation requirements involved in the successful implementation of this specification, and we can bring this valuable capability to your team.

Exposed Structural Systems

The use of transparency and exposed structural systems in architectural design go hand-in-hand. While structural glass facade systems make frequent use of cables, rods, and machined fittings, they also often include fabricated steel assemblies ranging from exposed anchor components to custom truss systems.The craftsmanship required for AESS is a rare competency. We have developed a network of qualified AESS steel fabrication vendors, a network built over time and upon the experience of many successfully completed projects. Enclos is able to manage the delivery process in a manner that best assures predictability of outcome, thus mitigating the risk of budget overruns and schedule delays.

Weld Quality and Workmanship

An important consideration with exposed structural steel is the treatment of welds. Designers often want welds to be ground flush and smooth, sometimes even polished. However, primary consideration must be given to the structural integrity of the weld. Accommodating both the structural performance requirements and the desired appearance starts as a critical design issue; welds must be designed such that both criteria can be satisfied in the fabrication and finishing processes. We are practiced at controlling this process from concept design through completed fabrication. The fit-up requirements for bolted connections can be an equally important consideration.

Finishes

Red iron rusts. Of the many great attributes of steel, this is not one of them. Exposed structural steel must be protected, and most often the finish requirements are meant to augment the appearance of the structure and not merely to protect the steel.The term “automotive finish” is frequently heard yet seldom achieved. Hot-dipped galvanizing can provide superior protection with a top color coat for appearance. Most steel fabrications are too large for this process however, and there are environmental concerns regarding its use. The application of paint over a galvanized surface can be tricky as well. Various other paint systems exist, most involving the application of a primer coat over a carefully prepared surface, followed by one or two color top coats. Metallic finishes are available and have been used successfully in a number of applications. A key decision is whether to apply the final coat in the field or in the shop. Shop application is invariably superior, but almost certainly subject to damage during shipping, assembly and erection even when extensive precautions are taken to protect the finish. A field touchup specification is as important as the basic finish specification in the case of factory applied finish.

Budgeting

The AESS Supplement comments, “…because AESS costs more to fabricate than standard structural steel, it is critical that these designs are properly budgeted. The repercussion of not properly budgeting AESS is often the need for redesign, project delays, and ultimately even higher project costs.” The budget for AESS is affected by subtle decisions regarding material, surface quality, weld quality and finish.Whether the concern is for welds, finishes, budgeting or any other aspect of AESS, Enclos can act as an expert guide through the maze of decision making to best assure the development of an appropriate AESS specification and its effective implementation.

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