Redistribution of internal forces in the lateral bracing system / Schnittgrößenumlagerungen bei der Gebäudeaussteifung

The lateral bracing system of a building should ensure the stability of the building, in terms of the usability and the total load capacity. The governing loads for the lateral bracing system are horizontal loads due to wind and earthquake. The horizontal loads are traditionally distributed to the bracing elements according to the uncracked elastic state dependent on the bending stiffness in the elastic (uncracked) state. This method does not allow consideration of non‐linear effects and load redistribution. Within the framework of the PRB Research Cooperation – Improving the Practical Use of Structural Design Standards through pre‐normative work – Subcontract 5: Masonry Construction, Subproject 3: “Large Shear Walls” [7], the cracked or plastic state can be taken into account through a displacement based approach. A matrix formulation for both the linear and cracked states has been derived and implemented.     

Surface-Water Abstraction Controls in Scotland

ABSTRACT The system of abstraction controls for irrigation in Scotland is one of local control orders where, to limit abstractions from any particular watercourse, the river purification authority must apply for an order from the Secretary of State for Scotland to cover abstractions from that one watercourse and its catchment. This contrasts sharply with the heavily protective system in England and Wales where the National Rivers Authority has statutory powers to license all abstractions. The purpose of this paper is to examine the abstraction control system in Scotland with a view to highlighting its advantages and limitations, and to suggest ways by which the system can be improved or made more effective.     

ADAPTING LOW-FLOW FREQUENCY ANALYSIS FOR USE WITH SHORT-PERIOD RECORDS

Low-flow frequency analysis techniques are robust only where the flow record is relatively long and the flow regime is known to be stationary over time. If applied to short-period flow records. low-flow frequency analysis can give poor or misleading results. This paper examines the effectiveness of data-transfer methods for improving the characterisation of low-flow frequency relationships for gauged sites with flow records of less than fifteen years.
Two transfer methods were considered. In each case the sequence of annual minimum flows from an analogue catchment was used to provide extra information about the sequence of flows at the site of interest. Transposing the standardised probability distribution function of annual minima between analogue sites worked where their flow records were highly correlated. However, better results were obtained where recurrence intervals for observations at the subject site were estimated from recurrence intervals for the same years in the analogue record.     

CONSTRUCTED WETLANDS FOR MINEWATER TREATMENT: PERFORMANCE AND SUSTAINABILITY

Wetlands were constructed between 1995 and 1999 to treat discharges from abandoned coalmines in the Pelenna Valley, South Wales. This was one of the first and most comprehensive demonstrations of passive minewater treatment technology in Europe, incorporating aerobic and anaerobic cells, including 'reducing and alkalinity-producing systems. The wetlands were monitored to assess their performance and longevity and were found to remove 82-96% of the incoming iron, with no decline in treatment performance over the monitoring period to 2002. Oxidation was found to be the dominant iron-removal process, even in vertical-flow cells which were designed to utilise anaerobic processes. Factors limiting the longevity of iron-removal processes were identified. maintenance requirements were highlighted and life-span predictions were calculated for the systems. The wetlands were shown to be an effective and low maintenance (but not maintenance-free) method of treating net-acidic and net-alkaline minewater.     

Substrate Removal by In-Sewer Oxygenation

This paper describes a study which was carried out to investigate the degree of in-sewer treatment which could be achieved by suspended heterotrophs (normally present in domestic sewage), under aerobic conditions and under different retention periods and sewage strengths.     

Aeromonads in Drinking-Water Supplies: Their Occurrence and Significance

Traditionally, bacteriological monitoring of drinking-water supplies has focused on the detection of Escherichia coli and related coliform bacteria. However, attention has recently been given to the occurrence of biofilms and associated organisms which occur in distribution systems. One group of bacteria which have been isolated from water supply systems are the Aeromonads. This group is gaining increased recognition as they have been implicated as causal agents of gastro-enteritis in humans and are indicators of regrowth potential. In order to obtain a better insight into these organisms and their relationship with other parameters, a number of laboratory and field-based studies were undertaken. These included (a) comparison of isolation media, (b) examination of biofilms, (c) temperature growth studies, (d) toxicity testing, and (e) sampling and analysis at treatment works and in distribution systems.     

The Health Effects of Low-Contact Water Activities in Fresh and Estuarine Waters

Four studies were carried out at separate locations to investigate the relationship between health effects and low-contact water sports, and intensive microbiological sampling was conducted in parallel to the health studies at each site. The two sports examined were marathon canoeing and rowing.
The extremes of water quality were at the estuarine sites on the River Torridge, where pollution levels varied from a geometric mean faecal coliform value of 62/100 ml at the Appledore/Instow site to 4613/100 ml at the Bideford site.
A comparison of 'exposed' and 'unexposed' groups, 5–7 days after exposure, showed that the health effects of low-contact water sports are minimal, within the water quality ranges which were studied.     

Measurements of Head Variations within Observation Boreholes and their Implications for Groundwater Monitoring

As part of several groundwater investigations of the Permo-Triassic Sandstone aquifers in north west England, a detailed measurement of piezometric heads and groundwater flow within observation boreholes was made which showed that vertical differences of groundwater heads persist within aquifers. A number of case histories of these studies are presented, which are used to consider the impact of head variations on typical groundwater level and groundwater quality measurements taken in observation boreholes, with a view to recommending design criteria for observation boreholes and groundwater monitoring programmes.     

A Large-Scale Grid-Based Hydrological Model of the Severn and Thames Catchments

This paper addresses the issues of scale and appropriate model complexity for large-scale hydrological models. A grid-based hydrological model, which employs the UK Meteorological Office Rainfall and Evaporation Calculation System, is applied to the Severn and Thames catchments using a grid scale of 40 km, and is shown to reproduce the observed mean annual runoff over a 10-year period to within 6% with no prior calibration. The variation in the model performance is strongly correlated with the linearity of the annual rainfall/runoff relationship and a climate index. At the monthly scale, runoff routing becomes significant, and the introduction of a two-parameter routeing algorithm significantly improves the monthly runoff simulations giving efficiencies of 90% and 88% for the Severn and Thames respectively. The results provide guidance to climate modellers looking for efficient and robust land-surface parameterizations, and indicate the potential application of such a modelling scheme to water resource managers.