Proceedings of the International Association for Shell and Spatial Structures (IASS) Symposium 2013 „BEYOND THE LIMITS OF MAN” 23-27 September, Wroclaw University of Technology, Poland J.B. Obrębski and R. Tarczewski (eds.) High rise buildings – Construction stage design G.C. Giuliani1, M.E. Giuliani2 , P. de Angelis3 1 dr.eng – exclusive consultant Redesco Progetti srl – Milano – gc.giuliani@redesco.it 2 dr.eng – general manager Redesco Progetti srl – Milano – me.giuliani@redesco.it 3 dr.eng – partner Redesco Progetti srl – Milano – p.deangelis@redesco.it Summary: In general, once the design tender issue for complex building has been completed, the contractors are pressed by the aims of the developers for getting the job finished as soon as possible. The structural design, drawings, specifications and verifications have to be adapted to the fast construction procedure. This scenario creates the need for a construction design stage in order to prepare for the general contractor a project suitable for the fast construction. Keywords: high-rise buildings ,erection methods, construction design stage, post-tensioned slabs, shrinkage and creep structural effects FOREWORD In general the construction design stage is as delicate as the general one, engineers indeed are called to adjust the contractor plans (construction methods, availability of equipment, time of erection, respect of time schedule) to the initial design concepts and choices that very seldom took into account the needs of the construction. In this article some paradigmatic examples occurred during the construction of the Porta Nuova Varesine plot in Milano are illustrated. The constructions are located on a former recreational area in the urban area of the city of Milan (Italy), the site features a rectangular shape (in plan) with 300m by 100m edges. A deep excavation was made to accommodate a four levels basement (parking and service areas), some buildings and a cultural centre elevated over street level (fig. 1). The buildings basic data are reported in the following table. Diamante Tower Solaria Tower Height: 140 m (30 floors) Columns / Core: Floors: Foundation: Steel / Concrete * Concrete on corrugated steel sheet Intended use: Direct foundation offices 3 pods – 35 floors(142, 112, 82 m) Concrete / Concrete Post tensioned concrete slabs Direct Foundation (soil stiffness improvement by diaphragms) residential Architecture KPF Basic structure Client: General Contractor: Construction Structural Design: Construction years: Ove Arup Varesine (Hines) CO.VAR. Redesco Progetti srl (Milano) 2009-2012 Arquitectonica / Caputo Partnership Ove Arup Varesine Srl (Hines) CO.VAR. Redesco Progetti srl+FV (Milano) 2010-2013 Fig. 1 – rendering of the plot This wide real estate operation imposed to the General Contractor a great effort for shortening the construction time. Among the several constructions three high rise residential buildings and an office one define the skyline of the plot In detail, some problems concerning the construction methods strongly interfered with the original, basic structural project. The aim of the paper is to show how these problems, if not properly taken into account during the basic design process, can affect the project even in its key concepts [1]. In this article we focus on the two highest buildings of the plot (fig. 2): the Diamante (140 m / 30 floors) and the Solaria (142 m / 35 floors) Fig. 2 – the Diamante and the Solaria towers Very efficient production systems were adopted for the erection of the structure; as a consequence the selection of the formwork system, had an extremely important role in the construction process. Formworks The development of the construction structural design was therefore carried on taking into account all the requirements depending from the formwork climbing system for the casting of the core walls and slabs. 210