Papers

Rehabilitation/restoration systems involving bonded-in rods represent an efficient alternative method for the repair and/or reinforcement of structural timber members. However, in spite of their advantages, their use is still restrained by the lack of knowledge about their long-term performance. In order to correct this situation it is necessary to gain a greater understanding of their durability, creep and fatigue behaviour. However, reliable and realistic accelerated ageing tests do not yet exist, and the application of the existing European or American standards to epoxy bonded products are much too penalising, since they merely impose severe conditions that are not verified in service although these may be suitable for other adhesives. To address these concerns a test procedure to assess long-term behaviour of bonded-in rod connections was developed with the aim of providing a simple method for the selection of candidate repair system materials for specific applications. The data collected so far using the RPAT (realistic performance assessment test) appears to predict correctly the end-use performance for different adhesives as well as for different timbers.

The plastic criteria for the verification of steel cross-sections resistance are usually based on some basic hypotheses such as the development of plastic hinges, which depend on the interaction between the internal forces and the cross-section shape; therefore, specific equations are required for each type of cross-section. This paper presents new alternative interaction criteria for the analysis of steel I sections subjected to an axial force and biaxial bending moments, at the elastic or the plastic limit states (as long as buckling phenomena are not involved). The plastic interaction criteria are presented, in a first step, for some particular combinations of the internal forces, such as axial loading with bending about a main axis, and biaxial bending without axial loading. In these cases, they are given by exact equations (within the frame of the hypotheses adopted in this study). All these plastic interaction criteria are compared with the corresponding plastic criteria adopted in the Eurocode 3 (EC3). Afterwards, a simplified global criterion is proposed for the simultaneous combination of an axial force and bending moments about both the main axes of inertia. This new simplified plastic criterion and the corresponding plastic criterion adopted in the EC3 are compared with the exact solution, obtained by a mixed numerical and analytical integration procedure. This comparison shows that this simplified criterion usually leads to results closer to the exact solutions. Some suggestions are then presented to improve the results given by the EC3.

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Performance assessment of water supply and wastewater services is today a major issue. Over the past six years, the National Civil Engineering Laboratory (Portugal) has been developing performance assessment systems for drinking water treatment plants (WTPs) and wastewater treatment plants (WWTPs). In 2009, a national field-test was launched in Portugal, ‘PASt21’, involving 27 plants (10 WTPs and 17 WWTPs). This paper presents an overview of the second generation of the performance indicator (PI) systems for the overall performance assessment of WTPs and WWTPs, the extent to which the systems were applied in the 5-year study period (2006–2010), and the aggregated results (average, median, percentiles 25 and 75, maximum and minimum) of representative PIs in each assessment group. It was concluded that all indicators are relevant, and the results show the ability of the proposed PI systems to assess the overall performance of a given treatment plant. The aggregated results are very important for the continuous improvement of the plant performance through benchmarking and periodic reassessment of targets.

This paper compares the factors known to influence the deleterious alkali-silica reaction in concrete with the properties that polymers tend to modify in cementitious materials. A discussion on the potential ASR-influencing mechanisms of polymer additions is provided, along with a critical review of the existing literature on the subject. The influence of the potentially significant differences in mechanical properties and sorptivity between polymer-modified and unmodified cementitious materials on the expansion results of alkali reactivity tests is also discussed. According to the available results, the influence of polymers on ASR-related expansion seems to depend on both polymer type and dosage, suggesting the existence of concurrent, not yet well understood mechanisms by which polymers may influence ASR-related expansion. As polymer modification of cementitious materials can lead to significantly lower modulus of elasticity, higher tensile strength and resistance to microcracking, it is suggested that further research on the subject includes not only expansion tests but also an assessment of the resistance of polymer-modified cementitious materials to ASR-related damage, the main concern due to this deleterious phenomena.

Fazer cidade humanizada, porque é marcada por ruas vivas e solidárias, não é, hoje em dia, um objectivo simples. Todos sabemos disso, porque todos conhecemos muitas ruas, que de ruas quase só têm o nome na placa toponímica, quando a têm. São ruas sem continuidade urbana, sem habitação vitalizadora, sem actividades diversificadas, sem ligações activas à cidade viva e sem uma escala formal e funcional que esteja, verdadeiramente, ao serviço do homem a pé, e de uma comunidade humana local, pelo menos, minimamente solidária e naturalmente convivial.

Single carriageway multilane roads are not, in general, a very safe type of road, mainly because of the high number of seriously injured victims in head-on collisions, when compared with dual carriageway multilane roads, with a median barrier. In this paper the results of a study on the effect of the application of several low cost engineering measures, aimed at road infrastructure correction and road safety improvement on a multilane road EN6), are presented. The study was developed by the National Laboratory of Civil Engineering (LNEC) for the Portuguese Road Administration and involved a comparison of selected aspects of motorized traffic behaviour (traffic volumes and speeds) measured in several sections of EN6, as well as monitoring of road safety developments in the same road. The applied low cost engineering measures allowed a reduction of 10% in the expected annual number of personal injury accidents and a 70% decrease in the expected annual number of head-on collisions; the expected annual frequency of accidents involving killed and seriously injured persons was reduced by 26%.

The patterns of water quality and ecological dynamics in estuaries vary at different time scales. Characterizing this variability at short (diurnal and seasonal) time scales is a pre-requisite to investigate the effects of long-term climate changes. Seasonal scales depend mostly on the natural climatic variability, while diurnal scales are generally associated with the tidal cycle and wind events. In order to study the role of these superimposed scales in the Aveiro lagoon, an integrated approach, which combines data acquisition and numerical modelling, was followed. The analysis was conducted with the three-dimensional, fully coupled hydrodynamic and ecological numerical model, ECO-SELFE, extended to account for the oxygen cycle. For data acquisition three field campaigns were performed along a salinity gradient (Mira channel), covering different seasonal situations: March 2009, September 2009 and January 2010. These campaigns, each lasting 24 hours, included the measurement of physical, chemical and biological parameters (river flow, water levels, currents velocities, water temperature, salinity, dissolved oxygen, nutrients and chlorophyll a). Results show the ability of the model to represent both the spatial and temporal patterns observed for the different variables. Chlorophyll a and nutrients tend to present larger concentrations upstream than downstream, with the largest values observed in spring. The distribution patterns are significantly influenced by the tidal dynamics.

ABSTRACT: This study investigates sediment transport at a very low-energy backbarrier beach in southern Portugal, from a spring-to-neap tide period, during fair-weather conditions. Rates and directions of transport were determined based on the application of fluorescent tracer techniques. Wind and currents were collected locally, whereas the dominant small and short-period wind waves were characterized using a morphodynamic modelling system coupling a circulation model, a spectral wave model, and a bottom evolution model, well validated over the study area. For the recorded conditions sediment transport was small and ebb oriented, with daily transport rates below 0.02m3 day-1. Tidal currents (mainly ebb velocities) were found to be the main causative forcing controlling sediment displacements. Transport rates were higher during spring tides, tending towards very small values at neap tides. Results herein reported points towards the distinction between tracer advection and tracer dispersion in this type of environment. Transport by advection was low as a consequence of the prevailing hydrodynamic conditions (Hs<0.1 m, and max. current velocity of 0.5ms-1) and the tracer adjustment to the transport layer, whereas dispersion was relatively high (few metres per day). Tracer techniques allowed distinguishing the broad picture of transport, but revealed the need for refinement in this type of environments (bi-directional forcing by ebb and flood cycles).

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