Overall Complex and Main Sports Venues for the 1972 Olympic Games, Munich

The main venue for the 1972 Summer Olympics in Munich was the "Oberwiesenfeld." Its centerpiece was the large stadium, the sports hall, and the swimming pool. The facilities and buildings belonging to this core area were to be planned and constructed within a cohesive framework, guided by the overarching concept of a landscaped setting, reflecting the themes of "Olympics in the Green," "Olympics of the Muses and Sport," and "Olympics of Short Distances." An area in the northwest of the city was available to realize these visions. The existing features—the rubble mound, the television tower, and the Nymphenburg Canal—served as the starting points for the design of an "Olympic Landscape." The prominent elevation of the rubble mound was incorporated and extended across the site in the form of embankments, thereby dividing the originally flat terrain into manageable areas. The pedestrian walkways on these embankments, separated from vehicular traffic, offered pedestrians diverse views into and out of the lower-lying areas. All embankments lead to the central plateau, around whose periphery the competition venues are nestled. This design allows the stadiums, despite their large dimensions, to appear less imposing; the unity of the terrain, buildings, and landscaping gives them a human scale. The stadium and sports hall are single-tiered, allowing everyone to see each other. This seating arrangement is intended to emphasize the sporting event as a shared experience. By integrating the stands into the topography of the central plateau, only the areas of the stadiums most relevant to the spectator are incorporated into the landscape. All ancillary spaces are either located underground or as naturally lit rooms beneath the built-up stands on the outer edges of the central plateau. The exterior and interior of the stadiums are interwoven. These fluid transitions dissolve the boundaries between individual structures. Where, as in the sports hall and swimming pool, they are essential for climate control, every effort is made to maintain transparency. The continuous glass facade runs independently of the roof edges. All steel components are painted in shades of green to match the landscape. The connection to the landscaped surroundings is most immediately apparent in the stadium, which is only partially roofed. The large stadiums are not designed as isolated structures, but rather as integral parts of the landscape. They consist of depressions in the terrain, complemented externally by grandstand structures. The roof spans the stadiums and parts of the landscape, uniting the individual buildings into a single, cohesive form that, together with the mountain, lake, and television tower, creates the Olympic Center. (Original text 1972)

Olympic Park in the year 2000

For the first Olympic Games in the Federal Republic of Germany, the striking complex was built almost thirty years ago, just four kilometers from the city centre. Since then, the "Olympic roof" in particular, with its impressive architecture, has become a major landmark of the city – and not just for architects.

The entire sports complex, the park-like landscape, and especially the magnificent roofs have become a national architectural monument. They demonstrate a design ambition and a new sense of form, which can also be seen in the context of the social upheavals of the 1960s.

The buildings set decisive standards in terms of content, form, and, not least, construction technology. They ideally demonstrate a planning symbiosis of architecture, structural engineering, and landscape design (in this case, the firms Behnisch und Partner, Frei Otto, Leonhardt + Andrä, and Günther Grzimek).

The application of lightweight surface structures, specifically cable net construction, was successfully implemented in a large-scale, internationally acclaimed project. The construction method and dimensions remain fundamentally valid today. Therefore, no modifications were necessary during the recent renovation.

Leisure park and competition venue

The entire Olympic Park area – undoubtedly aided by its location – has gained great importance as a local recreation area within the city of Munich. The distinctive landscape design – an integral part of the entire project – continues to be extremely attractive.

As planned by the designers, the city now boasts another recreational area in the form of the Olympic Park, on par with its traditional parks. The vegetation that has grown over the past 30 years has created an attractive area, partly with dense tree cover, in the heart of a densely populated urban area.
The outdoor facilities attract many visitors not only on weekends – up to 30,000 people on nice days.

The topography of the area—the dams, hills, depressions, valleys, and lakes—creates defined yet open spaces that allow for a good distribution of even large crowds. Both tranquility and activity can be found in different areas. From the viewpoints, one can overlook the city, and on clear days, the Alps are visible. Walkers, cyclists, joggers, inline skaters, boaters, sunbathers, and tourists frequent the area in all seasons. Even a small ski slope and a toboggan run offer children a rare treat for city centres in winter. In summer, various festivals find a well-situated venue in the Olympic Park.

Even today, sporting competitions and events of all kinds take place in the stadiums, arenas, and outdoor venues. Large concerts and shows are also held there. The swimming pool and ice rink are open to the public. The local adult education centre operates the so-called "Health Park" in the buildings, offering countless sports and leisure programs that are popular with Munich residents.

The most well-known organizers and regular users of the stadium are the two largest Munich football clubs, whose home games take place there on weekends.

Current renovation plans

The various plans to convert the Olympic Stadium from an athletics venue into a football-only arena, as demanded by its primary users, are currently causing discussion, not only in Munich. This would require not only a complete roof and a greater number of seats, but also a shorter distance between the seating and the pitch, while increasing the difference in elevation.

The addition of several steeper tiers and boxes is incompatible with the existing layout, which is why the entire grandstand structure, i.e. everything below the recently renovated roof, is being put up for discussion.

The architects holding the copyright have developed several models for grandstand construction and a complementary roof, one of which is currently awaiting a decision. Aside from the potential dismantling of an outstanding example of West German architecture, difficulties arise from two main aspects: firstly, formal considerations – the different roof design for the east side and the raised grandstand structure, which contradicts the landscape concept – and secondly, technical aspects, such as the costly lowering of the playing surface down to the groundwater level.

As an alternative, a functionally adapted new football stadium on the site of the former cycling stadium is under discussion – a solution that could ensure the preservation of the Olympic venue with its athletics facilities for other sporting competitions as well.

Opinions on whether to preserve or renovate the building diverge widely, especially between German architects and decision-makers. Thirty years after its creation, the outcome of this debate will also reflect the social and intellectual movements of the time.

roof construction

The roof's supporting structure is based on a prestressed, double-curved steel cable net with a 75-centimeter mesh size. It transfers the forces to edge cables, which converge at nodes. From these bearing points, the forces are anchored to tension foundations or transferred via masts to compression foundations; in the inner edge area, they are also transferred to air supports.

For the actual roof covering, which rests on the movable rope knots, various materials were initially considered. Lightweight concrete was discussed, as were metal shingles and wooden formwork. Ultimately, the media's demands were decisive: avoiding harsh shadows was crucial for colour television. Accordingly, the choice fell on a tried and tested translucent material: three-by-three-metre polymethyl methacrylate resin panels, i.e., acrylic glass.

The fire resistance was also a crucial factor. The pre-stretched panels shrink back to their original size when heated, causing the surface to rupture in the event of a fire and ensuring immediate smoke extraction. This also protects the cable net from heat. The material is treated with a fire retardant additive, does not itself burn, and does not drip burning material.

Roof renovation

The planners estimated the roof membrane's lifespan at approximately twelve years. In reality, renovation became necessary after 25 years. Regular technical inspections revealed no issues, with only a few isolated cases. It was only after a surprisingly long time that the material became brittle, and crumbling panels began to appear. The fire retardant additive likely contributed to this, causing progressive weathering, surface flaking, and consequently, the panels becoming cloudy.

These factors affecting the entire roof prompted the start of the 75,000 m² renovation in 1997, a project that lasted just over two years. Corrosion of the supporting structure was minimal, affecting only the edge cables and sections of cable near the anchorages or in the saddles. These areas were completely restored through cleaning and the renewal of the corrosion protection.

The acrylic glass panels, their joint profiles, support and fastening elements, however, had to be manufactured again.

The use of alternative roofing materials was also reconsidered. During a year-long trial, in addition to acrylic panels with a lower dose of fire-retardant additive, two further sample surfaces were tested: one made of polycarbonate, the other of a fluorinated film. However, polycarbonate is not manufactured in the required format. Due to its fragile UV-protective coating, it also failed to meet the requirements for walkability, and it yellows over time.
The use of a membrane failed due to a variety of problems:

The accessibility was not adequately provided.
The fire safety regulations, which included the increased requirements of 1972, were not met.
The expansion joints in the roof surface are essential for proper water drainage and protection against snowdrifts. The raised edge for a completely smooth surface would have been excessively large.
The necessary prestressing of the extremely long, differently curved tracks is technically impossible to manage.
The appearance would have been drastically altered, which had to be considered for reasons of historic preservation.

An attempt to equip the acrylic glass panels with a lower fire protection rating showed that the requirements could not be met. Therefore, the decision was made to use the exact same material for the new roofing. The manufacturer used the same machines that had been used in the initial production run. The associated components – aluminium strips, joint profiles, rubber buffers, etc. – were also manufactured in the same way as in the 1970s.

Most of the panels, as originally intended, received an additive of soot particles, which provides a slight tint. In accordance with the architectural concept, these were used to form the large, doubly curved roof surfaces. Where two panels meet, connecting fields, the so-called "eyes," are created at the ridges, through which the masts also pass. Here, and in the edge areas, untinted elements were laid to visually differentiate the various surfaces of the structure.

Gradually, specially trained assembly teams replaced the acrylic panels of all stadiums and connecting roofs with the new covering, so that today they can be seen again in virtually their original form.