German architecture firm SL Rasch uses ESI's Virtual Performance Solution to achieve architectural excellence in Medina and Mecca

20 October 2014
Paris, France

Paris, France – October 20, 2014 – ESI Group, pioneer and world-leading solution provider in Virtual Prototyping for manufacturing industries, announces the recent success of our client, SL Rasch: an architecture firm based in Germany that specializes in innovative buildings and lightweight structures. SL Rasch recently completed two complex architectural projects at the sacred sites of Medina and Mecca. The first was the design of foldable umbrellas that now protect pilgrims from the sun in the Medina Haram Piazza and the second was the design of the Mecca Royal Hotel Clock. Using ESI’s flagship software, Virtual Performance Solution, SL Rasch confidently investigated innovative designs and replaced physical models by virtual tests.

The umbrellas now in place at the Piazza of the Prophet's Holy Mosque in Medina. ©SL Rasch

The umbrellas now in place at the Piazza of the Prophet's Holy Mosque in Medina. ©SL Rasch

Today, the millions of pilgrims that travel every year to the Great Mosque of Medina, in Saudi Arabia, are sheltered by more than 250 hydraulically powered, foldable umbrellas, each measuring 26 x 26 meters. These translucent umbrellas are folded at night and open up during the day to create a micro-climate beneath them that is up to 8°C cooler than the surrounding area. Pilgrims visiting the important holy site in Mecca can admire the Mecca Royal Hotel Clock, situated at the top of a 601m high tower, which became the second tallest building in the world in 2012.

In order to test their designs of umbrellas for Medina SL Rasch initially used reduced scale physical models, but found that approach to be limiting. Dr. Mahmoud Bodo Rasch, CEO of SL Rasch therefore approached Dr Eberhard Haug, co-founder of ESI Group and author of the Lightweight Structure Analysis code “LISA”, seeking to collaborate in applying simulation methods in the evolution of more elaborate designs for these complex structures.

SL Rasch then virtually built and tested different types of structures using Virtual Performance Solution, ESI’s software that enables the assessment of all domains of product performance around a single core model. This required great care because of the complex geometry and importance of the architectural appearance of the umbrella’s double curve structure. In particular, a form finding process was used to determine a shape that would result in optimal minimum energy – necessary to guarantee that the membranes would last in time and under extreme weather conditions.

For structural analysis of turbulent wind loads on such lightweight structures, the team used Fluid-Structure Interaction (FSI) simulations, coupling Computational Fluid Dynamics (CFD) with Computational Structural Dynamics (CSD); both available as part of Virtual Performance Solution. SL Rasch and ESI co-created special tailor-made modules for modelling naturally turbulent wind loads and optimizing the shape and structure of the umbrellas. These were then used in computer simulations that investigated the safe folding and stowing of the giant umbrellas, taking into account gravity, overlaps, and wind loads. ESI’s unique expertise in the simulation of airbag folding for the automotive industry proved to be highly relevant throughout the studies.

Dr Rasch, Founder and Owner of SL Rasch GmbH comments

With the know-how of ESI experts and the capabilities built into ESI’s advanced CAE software solutions, designing our innovative structural systems became possible.”

Virtual Performance Solution also helped SL Rasch to overcome significant engineering challenges when designing the Mecca Royal Hotel Clock; constructed as a high strength steel structural skeleton clad with lightweight ornamented carbon-epoxy sandwich panels. The giant hollow-section composite clock hands - 23 meters long in the case of the minute clock hand - presented a special challenge as SL Rasch had to ensure these were aerodynamically stable even under high wind velocities and pressure; especially in the least favorable 12 o‘clock position, where the danger of periodic aero-elastic flutter was highest. The team performed wind tunnel test and CFD calculations before FSI simulation allowed them to validate their designs.

By using simulation, instead of building and testing physical prototypes for these two complex projects, SL Rasch was able to test many versions of the design and achieve optimal results while, at the same time, addressing all applicable safety requirements. This study also spared SL Rasch the production of physical prototypes, thereby saving time, considerable costs and environmental waste.

For more information about Virtual Performance Solution, please visit

For more pictures of these amazing projects, please visit the page dedicated to the folding umbrellas and the one about the Mecca Clock Tower on SL Rasch’s website

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About SL Rasch

SL Rasch se spécialise dans la construction de bâtiments spéciaux et structures légères; intégrant architecture et ingénierie. Une équipe interdisciplinaire de professionnels, composé d'architectes, d'ingénieurs structurels, mécaniques et aéronautiques, des physiciens et des informaticiens en collaboration avec les départements internes de gestion de projet, conception graphique et modèle de décision, apporte des techniques de pointe et des connaissances nécessaires pour l’élaboration du design et la résolution de problèmes. Pour plus d'informations, visitez