COMPREHENSIVE STRATEGY FOR HSC BEST PERFORMANCE IN. EXTENSIVE APPLICATIONS OF LANDMARK WORKS IN ITALY
A. Migliacci1, P. Ronca1, P. Crespi1 and G. Franchi2
1 Structural Engineering Department, Politecnico of Milan, Milan, Italy
2AMiS-Structural Engineering Office, Milan, Italy
Centering on worldwidly present urban areas, there have been many high-rise landmark buildings constructed in recent years. It is recognized that reinforced concrete has merit over steel frame construction in high-rise buildings, such as less sway in high winds, better human life protection in case of accidental heavy damage, better noise resistance. The use of high-strength concrete is rising, not only for pillars, in high-rise buildings. The paper points out on the need of classifying the HP-HSC for the different requested characteristic that materials have to exhibit on different structural elements of a complex structure. Among types of concrete, which binds together characteristics of High Strength Concrete (HSC) and High Performance Concrete (HPC), particular reference is made to Limestone Concrete (LSC).
Existing literature provides data on self-levelling, high performance, rapid hardening concrete, able to reach in few days the standard of HPC (Kelham, 1998; Montgomery et al., 1998; Nehdi et al., 1998). In particular the technology here referred for limestone concrete is not the usual one, but it makes reference to a mix design, characterized by an industrially produced limestone aggregates, with total absence of Silica Fume or any other addition of pozzolanic material or accelerating admixture (Cangiano, 2005; Cangiano et al., 2004).
The paper points out the significance of Limestone Concrete, as High Performance Concrete, application, starting from the following key construction requirements: in large public works with characteristic of very high durability, the choice of a technical solution it is not at all dependent on the construction cost only. In fact in this work, life service and safety performances, that slightly increase the construction costs, are of paramount importance. Starting from this key assumption, new materials, and in particular new concretes, may be able to notably cut life service and safety costs, considerably improving the performance/cost ratio of the selected solution, due to the large cut of maintenance costs. The paper wants to briefly explain the state of the art and the today frontier which lead to the material basic choices in structural design of high-rise buildings. In particular the paper refers to a comprehensive campaign of tests, in a starting-up phase, shared among different university and private laboratories in Italy, which aims to draw Guide Lines for different specific uses of Limestone Concrete, as HPC, in different structures typologies and environmental conditions.
Italy, like other countries in Europe, has experienced high rise building constructions with significant delay, respect to different countries all over the world. Reasons due to architectural heritage, cultural and educational schools in architecture may be the principal sources of delay. The construction of high rise buildings as new land-mark of our traditional and world-wide known cities is still a debating issue. Nevertheless, or because of that, and due to some episodes unfortunately experienced by important widely known buildings, the today technological background about the best requisites of advanced materials, as well as methods of structural analysis and design, indicates the need of significant and innovative approaches and strategies for achieving the best results for the construction
M. Pandey et al. (eds), Advances in Engineering Structures, Mechanics & Construction, 853-863.
© 2006 Springer. Printed in the Netherlands.
Fig. 1. The sail building phase of the Dives in Misericordia Church.
Fig. 2. WTC in San Marino construction site.
of landmark buildings, like the high-rise buildings are (High-Rise Manual, 2003; Simiu et al., 1996; Fairweather, 2004).
The solution of the engineering project of an architecture design has to be the optimal solution among several feasible solutions, often mutually contradictory and conflicting each other. Each different architectural project has own characteristic and demands for the best solution. Recent realizations have been discussed as peculiar examples in Italy, as for example the “Dives in Misericordia” Church in Rome (Figure 1) or the main r. c. structures of the World Trade Center in S. Marino (Figure 2) .
Due to some innovative architectural solutions, the demand due to particular layout of the structural elements or due to geometrical shape and slenderness of the vaulted structure, together with particular demand for the durability of brightness, have stimulate the research toward new technological, engineering and material solutions. The best design of the so called landmark building, as the high-rise buildings mostly are, is today focused, taking advantages from previous experiences, on different main objectives. The objectives to be considered, as far as materials are concerned, are:
(a) mechanical resistance,
(c) ductility and toughness,
(e) fire resistance.
In addition the objectives to be considered in the construction site are:
(a) simplicity and easiness of the construction processes,
(b) construction immediate costs,
(c) construction time and feasibility to respect the time schedule,
(d) site job environmental impact,
(e) historical and monumental existing constraints.
The new design philosophy for landmark long-lasting architectural buildings has to take account also the objectives for the service life, from which the most significant are:
(a) construction flexibility,
(b) low maintenance costs,
(c) assurance of high safety level (human life safeguards),
(d) environmental sustainability,
(e) urban costs and constraints.
The strategy of choosing the solution has to consider all the costs among the immediate construction, the life service and the safety costs.
As it will be briefly shown in the next section, among different parameters of the optimized solution, the chosen main structural material has a significant role in improving the performances/cost ratio, due to the cut of life service costs and to further advantages, like smaller dimensions of structures, reduction of construction time.