Monte Carlo Study of the Spin-1 Baxter-Wu Model

The two-dimensional spin-1 Baxter-Wu model is studied by using Monte Carlo simulations. The standard single-spin-flip Metropolis algorithm is used to generate the configurations from which the order parameter, specific heat and magnetic susceptibility are measured. The finite-size scaling procedure is employed in order to get the critical behavior. The extensive simulations shown that the critical exponents are different from those of the spin-1/2 model suggesting that the spin-1 model is in a different universality class.Comment: 3 pages, 3 figures, 1 tabl

Seismic vulnerability of Modern Architecture building's: Le Corbusier style: a case study

In Portugal, at the end of the World War II, a new generation of architects emerged, influenced by the Modern Movement Architecture, born in Central-Europe in the early twenties but now influenced also by the Modern Brazilian Architecture. They worked with new typologies, such as multifamily high-rise buildings, and built them in the most important cities of the country, during the fifties, reflecting the principles of the Modernity and with a strong formal conception inspired in the International Style’s codes. Concrete, as material and technology, allowed that those “Unity Centre” buildings become modern objects, expressing the five-point formula that Le Corbusier enounced in 1927 and draw at the “Unité d’Habitation de Marseille”, namely: the building lifted in pilotis, the free design of the plan, the free design of the façade, the unbroken horizontal window and the roof terrace. In Lisbon, late forties urban plans transformed and expanded the city, creating modulated buildings repeated in great extensions – that was a progressist idea of standardization. The Infante Santo complex is a successful adaptation to the Lisbon reality of the Modern Urbanism and Architecture. In the fifties, it was built a large number of Modern housing buildings in Lisbon, with structural characteristics that, in certain conditions, can induce weaknesses in structural behaviour, especially under earthquake loading. For example, the concept of buildings lifted in pilotis can strongly facilitate the occurrence of soft-storey mechanisms, which turns these structures very vulnerable to earthquake actions. The development and calibration of refined numerical tools, as well as, assessment and design codes makes feasible the structural safety assessment of existing buildings. To investigate the vulnerability of this type of construction, one building representative of the Modern Architecture, at the Infante Santo Avenue, was studied. This building was studied with the non-linear dynamic analysis program PORANL, which allows the safety evaluation according to the recently proposed standards

Experimental response of RC columns built with plain bars under unidirectional cyclic loading

A large number of existing reinforced concrete (RC) buildings structures were designed and built before mid-70’s, when the reinforcing bars had plain surface and prior to the enforcement of the modern seismic-oriented design philosophies. This paper describes a series of unidirectional cyclic tests performed on seven full-scale columns built with plain reinforcing bars, without adequate reinforcement detailing for seismic demands. The specimens have different reinforcing steel details and different cross sections. A further monotonic test was also carried out for one of the specimens and an additional column, built with deformed bars, was cyclically tested for comparison with the results for the specimens with plain bars. The main experimental results are presented and discussed. The influence of bond properties on the column behaviour is evidenced by differences observed between the cyclic response of similar specimens with plain and deformed bars. The influence of reinforcement amount and displacement history on the column response is also investigated

Experimental and numerical analysis of the cyclic behaviour of RC beam-column connections with plain reinforcing bars

The information available in the literature about the cyclic behaviour of reinforced concrete elements with plain reinforcing bars is scarce. As a consequence, the influence of bar slippage in elements with plain bars is not yet comprehensively understood. In this paper are presented and discussed the main results of the cyclic tests carried out on five full-scale reinforced concrete beam-column joints with plain bars and without specific detailing for seismic demands. An additional joint specimen with deformed bars was also tested for comparison. Furthermore, numerical models were built to simulate the response of two of the specimens. Particular attention was given to the influence of bar slippage. The results of the conducted analyses underline the importance of accounting for bond-slip in the numerical modelling of elements with plain bars and also highlight the need for specific models to simulate the effects of this mechanism in the presence of plain bars

Zero-temperature TAP equations for the Ghatak-Sherrington model

The zero-temperature TAP equations for the spin-1 Ghatak-Sherrington model are investigated. The spin-glass energy density (ground state) is determined as a function of the anisotropy crystal field $D$ for a large number of spins. This allows us to locate a first-order transition between the spin-glass and paramagnetic phases within a good accuracy. The total number of solutions is also determined as a function of $D$.Comment: 11 pages, 2 ps figures include

Cyclic response of RC beam-column joints reinforced with plain bars: an experimental testing campaign

Existing reinforced concrete (RC) buildings constructed until the mid-70’s, with plain reinforcing bars, are expected to behave poorly when subjected to earthquake actions. This paper describes an experimental program designed to investigate the influence of poor detailing on the cyclic behaviour of RC beam-column joint elements. Cyclic tests were performed on five interior and five exterior full-scale beam-column joints with different detailing characteristics and reinforced with plain bars. An additional joint of each type was built with deformed bars for an evaluation of the influence of bond properties on the cyclic response of the structural element. The force-displacement global response, energy dissipation, equivalent damping and damage behaviour of the joints was investigated and the main results are presented and discussed. The experimental results indicate that the bond-slip mechanism has significantly influenced the cyclic response of the beam-column joints. The specimens built with plain bars showed lower energy dissipation, stiffness and equivalent damping