Nutritive value and physical characteristics of Xaraes palisadegrass as affected by grazing strategy

The aim of this study was to ascertain whether the defoliation frequency based on a fixed rest period would generate variable sward structural and physiological conditions at each subsequent grazing event. The relative importance of the physiological age was established in comparison with the chronological age in the determination of the forage nutritive value of Xaraes palisadegrass [Brachiaria brizantha (Hochst ex A. RICH.) STAPF. cv. Xaraes]. Two grazing frequencies were defined by light interception (LI) at initiation of grazing (95% LI - ""target grazing"" [TG] or 100% LI - ""delayed grazing"" [DG]) and one based on chronological time, grazing every 28 days (28-d). Forage produced under the TG schedule was mostly leaves (93%) with a higher concentration of crude protein (CP; 138 g/kg in the whole forage), a lower concentrations of neutral detergent fibre (NDF) in the stems (740 g/kg), and higher in vitro dry matter digestibility (IVDMD) of the leaves (690 g/kg), compared to the other treatments. Lower grazing frequency strategies (DG and 28-d) resulted in forage with higher proportions of stems (10 and 9%, respectively). Strategies based on light interception did not produce pre-graze forage with a uniform nutritive value, as the indicators varied across grazing cycles. The treatment based on fixed days of rest did not result in uniformity.FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo

Unreinforced and confined masonry buildings in seismic regions : validation of macro-element models and cost analysis

Modern design of buildings requires accounting for sustainability aspects using a life-cycle perspective, but also the early design phase where earthquake actions have a significant influence concerning the structural design. Recently, the seismic evaluation of masonry buildings using macro-element modeling approaches became popular, by applying performance-based assessment procedures through nonlinear static (pushover) analysis methodologies. This work addresses the validation for these approaches referring to two full-scale masonry structures tested under quasi-static lateral loading and almost unknown in the literature. The experimental behavior of tested unreinforced masonry (URM) and confined masonry (CM) structures is compared against the pushover response of the corresponding computational models. Then, referring to typical housing in southern Europe and its usual design with a reinforced concrete (RC) structure, the validated assessment tools are employed to evaluate the earthquake-resistant possibilities of URM and CM solutions, namely in terms of maximum applicable ground accelerations. The masonry solutions are also compared in terms of construction costs against the RC typology. The considered analysis tools present a good agreement when predicting, satisfactorily, the experimental test behavior, thus being able to be used in performance-based design. With respect to the studied housing, the predicted pushover responses for the masonry structures denote capacity to resist earthquakes adequately. These structures allow also a significant cost reduction (up to 25%) against the RC, thus appearing to be competing alternatives.The first author acknowledges the financial support from the Portuguese Foundation for Science and Technology (FCT) through the Ph.D. Grant SFRH/BD/41221/2007. This paper is in honor of Engineer Angel San Bartolome Ramos, Professor and Researcher of the Pontifical Catholic University of Peru, for his contribution in the field of masonry structures

Benchmarking of commercial software for the seismic assessment of masonry buildings

In the present work a comparative study on the evaluation of the seismic response prediction of two buildings was made, using two Italian computer codes based on macro-elements and pushover analysis, seeking to gather knowledge on the needs for national applications. The buildings response to the earthquakes predicted by the two programs, characterized by the base shear, the deformation capacity and also the maximum ground acceleration supported was compared. The results obtained show the good performance of the methods based on modelling by macro-elements, which provide realistic predictions of the structure response to the earthquake with regard the base shear. In some cases good agreement is also found in terms of deformation capacity. In correspondence to the modelling by macro-elements, the non-linear static analysis used by the two computer codes evaluated seems to be a good and easily understandable approach

Possibilities and comparison of structural component models for the seismic assessment of modern unreinforced masonry buildings

This paper addresses the possibilities of structural component models for the seismic assessment of masonry buildings using pushover analysis. The ultimate goal is to allow efficient design of new unreinforced masonry buildings in seismic areas. Different modelling strategies are presented and the implementation of a simple design tool based on structural component models is described in detail. The different approaches are applied to a two-storey building with regular plan and elevation, allowing for a comparison between them. The results indicate that macro-modelling using structural component models and pushover analysis are adequate approaches for the seismic assessment and design of unreinforced masonry buildings, as the tools require very low computational resources, allow easy interpretation of results and provide satisfactory accuracy

Pushover seismic analysis of quasi-static tested confined masonry buildings through simplified model

The confined masonry typology has been traditionally used for building, and also selected for the reconstruction of recently earthquake-damaged cities, in developing countries responding to the seismic-economic couple. However, most of the procedures in design codes adopted for these countries are force-based, which appear to be inadequate for loading cases under severe earthquakes, where the response in displacement plays the essential role for ultimate (life preservation) limit state. In this work, a worldwide review is made of the experimental response of confined masonry buildings, from which a first storey, shear-dominated, mechanism is mostly identified. Then, two full-scale confined masonry structures with regular and irregular plan configurations, quasi-static tested, are analysed under push-over loading of simplified models of the buildings. The idealized models are based on the use of frame and discrete spring elements, allowing to consider the interaction between the masonry panel and the r.c. confining elements. A comparison between the results of tests and the analytical predictions is made, particularly concerning the base shear-displacement response and the damage patterns. The accuracy of the predictions is very satisfactory, allowing to capture the base shear-displacement response envelope and the general damage trend on the buildings, and thus making the method able for performance-based design procedures

Pushover analysis of a modern aggregate of masonry buildings through macro-element modelling

The masonry building aggregates are a typology of construction typical of historical town centres, where a complex structural system with longitudinal and transversal walls is arranged at different ground and roof levels. Currently, the recuperation of the masonry as a structural solution will depend, in significant part, on its use in the construction of housing blocks, which can present many of the features of a typical building aggregate. The behaviour of this construction typology should be assessed under seismic loads, since it has been shown to be vulnerable to such type of loading. In this work, the case of a modern aggregate of masonry buildings, which is constituted by adjacent buildings at different levels, is studied under simulated seismic loading through nonlinear static (pushover) analysis on a macro-element model idealized for the aggregate. A developed concrete block masonry system is adopted as the structural solution. The aggregate is evaluated regarding its seismic performance by considering three different configurations: a set of dwellings with independent behaviour, a levelled conglomeration of buildings, and an unlevelled aggregate. A comparison between the predicted performances of solutions with unreinforced and truss type horizontally reinforced masonry is made in terms of both base shear-displacement response and damage pattern. The main conclusions are that the structural irregularity in elevation implies loss of displacement capacity, and that the horizontal truss reinforcement allows only qualitatively an improvement of the structural ductility, given a more distributed damage and a higher deformation capacity

Verificação da segurança sísmica de edifícios em alvenaria através de metodologias simplificadas

Este artigo introduz conceitos de base para o cálculo sísmico de edifícios sustentáveis em alvenaria simples de pequeno porte (até 2 pisos), usando metodologias de análise estrutural a nível global e simplificadas. Estas metodologias, ainda que relativamente simples e passíveis de utilização através de um cálculo manual, foram desenvolvidadas em países com sismicidade média a alta, e ainda assim com forte tradição de construção em alvenaria simples moderna (i.e. unidades robustas e estruturas com paredes bem ligadas e dispostas em ambas as direcções). O desempenho sísmico de edifícios assim dimensionados mostrou-se bastante satisfatório

Potencialidades de construção e projeto de edifícios em alvenaria simples

A alvenaria é a mais tradicional tipologia de construção em Portugal. No entanto, a simplicidade de utilização de betão armado e um receio pouco fundamentado sobre a resistência aos sismos rapidamente fizeram esquecer a alvenaria como solução estrutural. Recentemente, têm sido tomadas diligências no sentido de reanimar a construção com alvenaria resistente, nomeadamente através do desenvolvimento de sistemas de alvenaria modernos eficientes e sismo-resistentes e de estudos de viabilidade desta solução. Neste artigo avaliam-se as potencialidades de construção de edifícios com alvenaria simples em Portugal, nomeadamente a possibilidade de construção em altura, e com arrojo arquitectónico com referência a um caso real. Paralelamente, potencia-se a utilização de dois softwares de cálculo comerciais no projecto sísmico de edifícios em alvenaria