Façades constructed of stainless steel wire mesh

Planning, constructing and installing large-scale façades made of stainless steel mesh confront metal construction builders and material suppliers with a complexity of challenges. But here, too, the principle still applies: the closer the elements of the production chain - builder, metal construction specialist and material supplier - work together from the planning stage onwards, the smoother the whole project runs. The cooperation between the construction specialists Fassadentechnik Schmidt, based in Eppelheim near Heidelberg, and the metal weavers GKD - Gebr. Kufferath AG, based in Dueren, demonstrates important aspects of mutual complementation within the framework of a highly challenging project: the achievement of an external façade for the Department of Information Technology at the University of Ulm designed by the architects of the hochstrasser.architekten agency in Ulm.

Even in the phase of bidding for the project, the collaboration of constructive-creative competences of metal construction specialists and material producers is called for in order to interpret the task at hand in terms of the specific material properties and processing techniques required. The more precise the specifications, the better the companies executing the job can apply their constructive concepts to ensure an optimal accomplishment of the project. More than basic experience with the handling and processing of stainless steel is not really necessary, according to Mr Schmidt-Kleemann, manager of Fassadentechnik Schmidt, to lay out and install stainless steel wire mesh façades. "Anyone who works with stainless steel," agrees the GKD project manager; Werner Freialdenhoven, "knows what to watch out for during welding or pickling, or that stainless steel in contact with galvanized elements causes unattractive rust spots". The know-how of the façade construction specialist is complemented by GKD's technical advisory competence and services during the planning stage. Stainless steel wire mesh has unique specific properties due to its processing. Although it is optically extremely filigree and semitransparent, the raw material used means that it is relatively heavy. This makes the material highly stable and robust, yet at the same time, because of the woven structure, it is flexible, permeable to air, and mobile. This is what gives stainless steel wire mesh its unique aesthetic quality.

The architectural concept: representational versatility This aesthetic quality is at the core of the concept of the architects in Ulm. The cubic building stands at the edge of the university campus, which is characterized by sober buildings with exposed concrete façades. The new IT building was to have a representative character, since, in addition to university functions like the new lecture hall, it is also intended as an appropriate context for special events like award celebrations or conferences. In contrast to the earth-bound optics of the surrounding buildings, the new building was to have a significantly lighter and at the same time aesthetically high-quality aura. The choice of material was for the mesh type Alpha 1625. "This material has the unique property of changing appearance according to the way light falls on it. Seen from the front, it allows you to look right into the building. Seen from the side, it looks opaque and reflects the light", says project architect Rainer Trenk, according to whom the versatility and representational grace of the textile material structure were the core arguments for the choice of stainless steel wire mesh.

Essential factors in planning: weight, wind and weather

GKD supplies the material directly to the site, in rolls already cut to the required shapes - strips of up to 8 meters wide and of theoretically unlimited length. In practice, of course, the material's own weight sets certain limits on the size of the individual elements. In Ulm, a façade with a total surface area of about 750 square meters was accomplished. The individual, differently sized components, from 5 meters wide and up to 10 meters long, weighed up to 160 kilograms each, "so we could get them to their designated places on the building using trucks and cranes with appropriate load capacities", explains Mr Schmidt-Kleemann.

Depending on the span width of each individual wire mesh façade, calculations must be made of load capacity and stress zones with respect to local conditions of wind strength and ice and snow loads. It is especially in these respects that metal construction specialists and material producers need precise minimum agreed values in order to be able to define the appropriate mesh type with corresponding design and fastening techniques. In Ulm, the façade technicians of the Schmidt company were confronted with very specific climatic conditions. With a typically high incidence of fog during the winter months, hoarfrost leads to the formation of an ice sheet up to 6 cm thick on the façade. The result is an additional weight of up to 50 kilograms per square meter. Under such conditions the façade, which can usually absorb a certain wind strength due to its flexibility and permeability to air, reacts practically like a closed surface. To bear the increase in the material's weight and the wind force, the façade technicians chose a high-resistance anchor construction: Hilti anchors made of stainless steel in a composite system (adhesive wall anchors). In contrast to initial plans, the external shell of precast concrete parts directly behind the wire mesh façade was in fact made to be load-bearing in order to ensure the required stability. The installation technicians then fastened the Hilti anchors through the construction of external shell and insulation zone into the underlying, static concrete façade.

Determining tension and fastening technique

Determination and consideration of environmental conditions in relation to mesh aperture size and weight of the stainless steel wire mesh is a decisive factor when using stainless steel wire mesh. For this reason, there are round 23 different material types in the product range of GKD - Gebr. Kufferath AG which react differently in certain parameters to wind force. Depending on the weight of the particular weave type and the size of the façade elements, edge stress in wind may behave differently to stress on the surface. This must be taken into consideration in the choice of the particular fastening technique and the degree of tension to be placed on the material by, for example, fastening the woven mesh strips at the top and the bottom. In this respect, GKD provides façade technicians with specific planning services, including static calculations and load specifications as well as standardized solutions for appropriate fastening of the wire mesh with regard to its particular mesh type, the chosen span width and strength, and the prevailing local conditions. All fastening devices which are attached to the mesh or which hook into it, like loops and hooks, are supplied by GKD. Substructures or frame constructions to which the wire mesh may have to be fitted and fixed, steel constructions as well as superstructures and scaffolds on the supporting substructure lie within the competence of the responsible installation and façade technicians.

"Well-coordinated planning in advance is the key to success", says Mr Schmidt-Kleemann, summing up. Having worked together on several projects already, the two companies, Schmidt and GKD, are a well- established team. Further projects are being discussed.

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