Esperienze progettuali di edifici per attività natatorie

Alla città di Milano manca un centro natatorio di spicco atto ad ospitare eventi sportivi di caratura internazionale. L’articolo affronta il tema della progettazione di edifici per attività natatorie proponendo l’inquadramento di possibili soluzioni progettuali attraverso degli studi eseguiti nell’ambito del corso “Building Technology Studio” al Politecnico di Milano. I progetti sono contestualizzati nell’ambito di un quartiere originariamente pensato per il rapporto con l’acqua, ovvero Porto di Mare, sito alla periferia sud-est di Milano

Slender precast voided slabs under walking-induced vibration

Disturbance/discomfort caused by vibrations, induced by pedestrian walking on slabs in residential/office buildings, is a typical design issue for lightweight slender slabs, including prestressed concrete ones. Precast slabs are typically made with pretensioned members which allow for only partial collaboration in the transverse slab direction, which becomes even less effective when they are dry-assembled without cast-in-situ topping since it relies on the arrangement of mutual mechanical connections only. This study investigates through tests and numerical analyses the response of slender precast long-span slabs made with voided members, dry-assembled with mechanical connections, when subjected to vibrations generated by human activities. A parametric set of dynamic modal and time-history analyses encompassing floor member geometry, connection arrangement, mass, and damping, is carried out. The numerical models are validated against results from an experimental test program carried out on two decks of a prototype precast building. The tests and the numerical models allowed to characterize the fundamental dynamic properties of the slab and its vibrational performance, identifying the most efficient technological solutions among those investigated to mitigate human-induced vibrations

Structural assessment of modular precast 3D cell mid- to high-rise buildings with different connections

Precast construction employing modular 3D cells for housing was developed alongside frame and panel buildings since the end of WWII, mainly in Europe. This technology combined with in-situ concreting of wet joints was employed with a certain success throughout Europe up to the ‘80s, after which it became progressively less popular due to the difficulties in handling transportation (both lifting and shipping due to the large cell dimensions) and limited benefits in construction due to the partial prefabrication, framing its modern application in many countries to relatively small-size building components, such as kitchen/bathroom or service blocks. Thanks to the recent innovations of the precast concrete technology (both in production and structural connections), combined with the market evolution, this technology is nowadays experiencing a renovated interest for mid- and high-rise buildings, especially in Asia, where rapid dry or semi-dry assemblage of the cells ensures the full finishing of the units in factory, and the full exploitation of the benefits induced by the prefabrication process. As a matter of fact, the current literature regarding the structural behaviour of buildings employing this technology is lacking from a robust assessment, especially concerning their seismic performance. As a preliminary attempt to fill this gap, this paper presents the results of traditional seismic analysis with response spectrum carried out on a representative large residential building designed having 6, 12, 18 and 24 storeys modelled with shell elements and spring connections, analysing the limit PGAs associated to each typology and commenting the role of different connection devices and the possible design implications

The (In)Efficiency of interaction

Evaluating higher-order functional programs through abstract machines inspired by the geometry of the interaction is known to induce space efficiencies, the price being time performances often poorer than those obtainable with traditional, environment-based, abstract machines. Although families of lambda-terms for which the former is exponentially less efficient than the latter do exist, it is currently unknown how general this phenomenon is, and how far the inefficiencies can go, in the worst case. We answer these questions formulating four different well-known abstract machines inside a common definitional framework, this way being able to give sharp results about the relative time efficiencies. We also prove that non-idempotent intersection type theories are able to precisely reflect the time performances of the interactive abstract machine, this way showing that its time-inefficiency ultimately descends from the presence of higher-order types

LINEAR DYNAMICS OF PRECAST VERTICAL PANELS CLADDING INDUSTRIAL FRAMES UNDER EARTHQUAKE ACTION

The dynamic interaction of heavy vertical cladding panels with single-storey precast industrial frame structures plays a relevant role upon the generation of seismic actions in the connection devices out of the plane of the panels. Nevertheless, the current design approaches consider the panels as “non-structural members” and the forces at the connections are evaluated with approximate expressions available in the literature and mainly conceived for suspended masses. This paper, starting from a rigorous definition of the problem, highlights a minimal set of parameters that control the linear dynamics of the system and presents a novel analytical solution for the evaluation of the system response under seismic excitation. This task is indeed complex due to the peculiar kinematics of the panel and to the different accelerations imparted to the panels, at the same time, in foundation and in correspondence of the connection to the frame. Applications of the code expeditive evaluation of the maximum forces at the top and bottom connections of the panel highlight large discrepancy with respect the newly proposed rigorous solution, albeit being on the safe side

Environmental impact reduction of precast multi-storey buildings by crescent-moon seismic dampers hidden in beam-column joints

The growing demand of sustainable precast structures for multi-storey con-structions is often driven by the optimisation of cross-sections and reinforcement volumes of the structural elements. The present paper describes a real building recently designed and assembled with the installation of crescent-moon hysteretic dampers in the beam-column joints, recently proposed and patented. The joint continuity allows for an optimisation of the lateral load resist-ing system, reducing the size of the columns with respect to the classical precast frame structural arrangement with hinged joints, whilst protecting columns and beams from the large actions deriving from the classical moment-resisting cast-in-situ or partially precast technological solu-tions. After the complete detailed design of the case study building employing the 3 solutions described above, the precast dissipative one being designed with dynamic non-linear analysis, the results of an environmental impact analysis are compared and discussed, confirming a reduced environmental impact for the dissipative solution, with respect to both precast with hinged beam-column joints and moment-resisting cast-in-situ alternatives

Cyclic shear tests on RC precast beam-to-column connections retrofitted with a three-hinged steel device

Recent European earthquakes demonstrated that the seismic response of RC precast structures can be significantly influenced by the connection systems. Moreover, during past seismic events, many failures of the beam-to-column connections occurred due to their inadequate strength under seismic loads. The seismic safety of these connections has a crucial role in the overall seismic capacity of existing precast structures. A new connection system is employed as a retrofitting solution for a damaged beam-to-column connection and its cyclic shear performance is investigated by means of two cyclic shear tests on two different configurations. In both the experimental tests, the results demonstrate an efficient behavior of the retrofitted connections under horizontal cyclic loads. The comparison between the performance of the investigated connection and the response of a typical beam-to-column dowel connection allows to discuss the main critical features of the dowel connection system

Experimental tests on shallow foundations of onshore wind turbine towers

The current effort towards the progressive switch from carbon-based to renewable energy production is leading to a relevant spreading of both on- and off-shore wind turbine towers. Regarding reinforced concrete shallow foundations of onshore wind turbine steel towers, possible reductions of reinforcement may increase their sustainability, speed of erection, and competitiveness. The article presents the results of an experimental program carried out at Politecnico di Milano concerning both cyclic and monotonic loading, simulating extreme wind conditions on 1:15 scaled models of wind turbine steel towers connected by stud bolt adapters to reinforced concrete shallow foundations embedded in a sandy soil. Three couples of foundation specimens were tested with different reinforcement layouts: (a) similar to current praxis, (b) without shear reinforcement, and (c) without shear reinforcement and with 50% of ordinary steel rebars replaced by steel fibers. Additional vertical loads were added to the small-scale models in order to ensure similarity in terms of stresses. The test results allowed to (i) characterize the mechanical behavior of the foundation element considering soil-structure interaction under both service and ultimate load conditions, (ii) assess the foundation failure mode, (iii) highlight the role of each typology of reinforcing bars forming the cage, and (iv) provide hints for the optimization of these latter

Phase I study of sorafenib combined with radiation therapy and temozolomide as first-line treatment of high-grade glioma.

BACKGROUND: Sorafenib (Sb) is a multiple kinase inhibitor targeting both tumour cell proliferation and angiogenesis that may further act as a potent radiosensitizer by arresting cells in the most radiosensitive cell cycle phase. This phase I open-label, noncontrolled dose escalation study was performed to determine the safety and maximum tolerated dose (MTD) of Sb in combination with radiation therapy (RT) and temozolomide (TMZ) in 17 patients with newly diagnosed high-grade glioma. METHODS: Patients were treated with RT (60 Gy in 2 Gy fractions) combined with TMZ 75 mg m(-2) daily, and Sb administered at three dose levels (200 mg daily, 200 mg BID, and 400 mg BID) starting on day 8 of RT. Thirty days after the end of RT, patients received monthly TMZ (150-200 mg m(-2) D1-5/28) and Sb (400 mg BID). Pharmacokinetic (PK) analyses were performed on day 8 (TMZ) and on day 21 (TMZ&Sb) (Clinicaltrials ID: NCT00884416). RESULTS: The MTD of Sb was established at 200 mg BID. Dose-limiting toxicities included thrombocytopenia (two patients), diarrhoea (one patient) and hypercholesterolaemia (one patient). Sb administration did not affect the mean area under the curve(0-24) and mean Cmax of TMZ and its metabolite 5-amino-imidazole-4-carboxamide (AIC). Tmax of both TMZ and AIC was delayed from 0.75 (TMZ alone) to 1.5 h (combined TMZ/Sb). The median progression-free survival was 7.9 months (95% confidence interval (CI): 5.4-14.55), and the median overall survival was 17.8 months (95% CI: 14.7-25.6). CONCLUSIONS: Although Sb can be combined with RT and TMZ, significant side effects and moderate outcome results do not support further clinical development in malignant gliomas. The robust PK data of the TMZ/Sb combination could be useful in other cancer settings