240 X4 Category 4: Special Projects Introduction The project concerns the realisation of a new building in the centre of The Hague. It consists of a parking area in the basement, a shopping area on the first 3 floors, and 6 and 12 floors with apartments. Figure 1 gives an artist’s impression. The building has been designed by the architectural firm Bedaux de Brouwer in conjunction with IMd Raadgevend Ingenieurs, and was commissioned by the development company Kalvermarkt. It is currently (March 2013) under construction and is being built by Züblin Nederland, part of the construction group STRABAG. Design One of the main characteristics of the design is the fact that the new building is constructed on top of an existing foundation. A large part of the building site consisted of a 60-year-old building. This building has been completely demolished with the exception of its basement foundation. The new complex is much larger than the previous structure. To be able to withstand the much heavier loads on the foundation on top of the floor slab of the old basement structure a new raft foundation has been designed. The basis of the raft foundation consists of a 400 mm reinforced concrete slab that is continuous over the base of the structure. The raft is able to span any area of weaker soil and it spreads the loads over a wide area. An exceptional part of the structure is the foundation of the very heavy loaded steel-concrete composite columns. The columns stand on top of walls which are located in the basement. Each wall carries 2 columns which are located at the outer ends. What makes it special is that a large part of the reinforced concrete wall structure has been replaced by a steel frame. This appeared to be necessary because of the very high compression stresses that occur. Furthermore, it was required to strengthen the concrete slabs underneath the walls by steel HEM beam frames to form a ribbed construction. For the design of this atypical complex structural element a 3D Scia Engineer model has been made. The heavy point loads from the columns are transferred and spread by the walls into a uniform load on the basement slab. In return the steel floor frames spread the uniform loads per m1 from the walls into a uniform distribution soil pressure across the foundation. The structure has been designed on basis of the assumption that the soil has the maximum allowable bearing value of 500 kN/m2. In the Scia Engineer model, the steel parts of the construction are modelled by 1D bar members. The reinforcement wall and floor sections are included by use of 2D wall and plate elements. Construction The main advantage of using the existing basement was the enormous reduction of the building costs. On the other hand, it also required a relatively complex building process. First of all, the placement of the aforementioned steel frames is a relatively unique operation and requires an experienced and skilled building team. Furthermore, the possible uplift of the basement during construction due to the groundwater pressure on the structure has to be prevented. To avoid this, the basement has to be temporarily filled with sand bags. The presence of a tunnel for public transport nearby the building site has also placed additional requirements on the building operation. Software: Scia Engineer Amadeus Kalvermarkt - Den Haag, The Netherlands
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