Aerodynamic investigations for the tender design concepts of the Øresund cable-stayed bridge

For the Øresund link project two alternative tender designs were proposed, one single-level box girder solution and a double-level truss girder solution. Aerodynamic investigations, comprising wind tunnel section model tests as well as full-scale predictions, were carried out for the cable-stayed part of the two design alternatives. The section model tests covered static and dynamic tests for various configurations of bridge deck equipment, aiming at the detection of possible instabilities or vortex shedding effects and recording of the buffeting response. Cross-sectional admittance functions and aerodynamic derivatives have been estimated, and employed for full-scale predictions of dynamic displacements at a chosen value of the characteristic mean wind speed.     

The emerging aesthetic — accident or design?

During the unprecedented period of building activity in the Middle East, architects have become very aware of the way in which the ongoing Islamic tradition and 20th century technology can be reconciled satisfactorily. A substantial volume of building in the earlier days of the construction boom resulted in entirely inappropriate building forms which flagrantly ignored climate, culture and custom. However, in more recent years a more careful synthesis has been evolved which draws on the best of both cultures to provide the basis for an entirely authentic way of architectural expression.     

A 'perfect' design — and yet…

Practice shows that time and again office buildings fail to live up to expectations. Complaints are often heard that inside air temperatures are too low, yet apparently the design calculations have been numerically perfect. The obvious presumption is that some of the principles followed may not have been the right ones, but identifying those that were wrong is not always easy. Here the Professor of the Building Physics Division in the Civil Engineering Department of Delft University of Technology cites some of the possible reasons for this design problem, and discusses some likely causes of mistakes and their effects on internal air temperatures.     

Öresund Bridge. Temperature and cracking control of the deck slab concrete at early ages

High performance features are required of the concrete for the deck slab of the bridge over Öresund Straight between Denmark and Sweden and, among them, great durability. To guarantee this, it is necessary to assure, in advance, and control during the construction of the deck slabs, that the maximum temperatures and the traction stresses in the deck slab will not be greater than the allowable values, and to control these factors during the construction process. Before beginning construction, the deck slab was calculated using a program of finite elements that considers the heat generated, the shrinkage and creep of the concrete and the ambient conditions. To control the temperature during construction, temperature sensors are installed in various sections of each of the 49 deck spans and the temperatures produced during the first days of hardening are recorded on a computer. The temperatures of the components are also measured in order to estimate the temperature of the fresh concrete.     

Rural housing — Recognizing design needs

Research has identified an area of lack of knowledge between the current concerns of social scientists and those of the designers who are concerned with individual buildings. The author highlights the conflict of the role of the dwelling as evolved by urban society and the actual role that rural houses are called upon to play.     

The use of performance-based simulation tools for building design and evaluation — a Singapore perspective

This paper provides an overview of some of the state-of-the art performance-based simulation tools available for the design evaluation of environmental quality in buildings. Through an extensive industry survey, it reveals the extent of usage of performance-based simulation tools for building design and evaluation in Singapore. It highlights particularly the difficulties encountered in the usage and the needs of the industry for such tools. Recommendations are also given as to how to promote the pervasive use of such simulation tools to enhance the design process.     

Displacement ventilation in industry — a design principle for improved air quality

There is very little quantitative documentation of actual improvements resulting from the installation of new general ventilation systems in industrial settings. Therefore the performance of the common mixing design principle was compared to the displacement design principle by means of an intervention study in a workshop (V = 12,000 m³), where thermoplastics were moulded. An experimental signal-response tracer gas technique was used. In terms of supplying fresh air to the zone of occupancy the displacement system was better than the mixing system by a factor of 2. In terms of the exposure level to a simulated contanium (tracer gas) the displacement system was better by a factor 1.5–18.     

The feeling for landscape — a German example

A feeling for landscape was considered essential for the creation of a landscape close-to-nature in Germany during National Socialism. Examples of the connections between landscape, race and nation, (a race-specific understanding of landscape) and the outstanding position German man was considered to have, are given. The far reaching and disastrous consequences of such connections and their integration into a political concept are briefly sketched.     

RC columns strengthened with bandage — experimental programme and design recommendations

Results from experimental tests of 39 columns strengthened with bandages are presented. The influence of spacing and sectional area of steel strips, dimensions of angles and temperature of bandage activation on the behaviour of columns loaded by concentric normal forces are examined. The design recommendations and practical applications are presented. The design recommendations are based on the results of experimental tests, on the theoretical analysis of the behaviour of the columns and on the experience of practical application in the construction industry.     

Cold-formed steel members — design approaches in the United States

In the United States, design specifications for cold-formed steel structural members have been developed and refined over a period of 50 years or so by a consensus group managed by the American Iron and Steel Institute (AISI). Recently, the scope of these specifications has broadened significantly. The traditional allowable stress design (ASD) specification for carbon and high-strength steel sheets was extensively revised in 1986 to reflect an allowable member moment or load approach. Referred to as the unified approach, the revised specification treats all types of compression elements with a consistent effective width approach and treats all types of compression members in a consistent manner. The specification was further modified by a 1989 addendum to reflect the results of continuing research. In 1991, the ASD specification was supplemented by a separate load and resistance factor design specification (LRFD), intended to provide a more consistent index of structural reliability. The ASD and LRFD specifications of the AISI have been organized on a parallel basis to facilitate consolidation at an appropriate date. Also, as discussed in a separate paper, a new specification for the design of cold-formed stainless steel members has been recently developed by a consensus group under the auspices of the American Society of Civil Engineers (ASCE). This ASCE document, which replaces an AISI ASD specification that had not been updated for many years, is an LRFD specification that includes an appendix with the ASD approach. Thus, specification development for the design of cold-formed members in the USA has been very active. This is made possible not only by the efforts of the supporting groups, but by the extensive volunteer efforts of the many engineers who participate.     

The nature of cultural landscapes — a nature conservation perspective

This paper explores the reasons for the growing interest in cultural landscapes in nature conservation circles. It contains a brief discourse on nature and culture, emphasizing the declining power of the idea of pristine wilderness, the realization that many disturbed ecosystems are important to conservation, that agri-biodiversity is a resource to be protected along with wild biodiversity, and the need to find models of sustainable land use. Examples are given, at the global (World Heritage Convention), European and national levels, of the way in which the growing interest in cultural landscapes manifests itself; special attention is given to the category of protected area known as 'protected landscape/seascape'. Finally, the author identifies the major natural qualities found in cultural landscapes which will assist in understanding, identifying and protecting those features of value.     

Building materials — The Indian scenario

Professor Deb's analysis is timely and emphasizes the need for the Indian construction industry to react in a global manner to the importation of materials, the use of scarce natural building resources in the continent and the need to be aware of the environmental damage, production of traditional materials, such as clay, can have on fertile river plains.     

Robust design of composite cylindrical shells under axial compression — Simulation and validation

Thin-walled shell structures like circular cylindrical shells are prone to buckling. Imperfections, which are defined as deviations from perfect shape and perfect loading distributions, can reduce the buckling load drastically compared to that of the perfect shell. Design criteria monographs like NASA-SP 8007 recommend that the buckling load of the perfect shell shall be reduced by using a knock-down factor. The existing knock-down factors are very conservative and do not account for the structural behaviour of composite shells. To determine an improved knock-down factor, several authors consider realistic shapes of shells in numerical simulations using probabilistic methods. Each manufacturing process causes a specific imperfection pattern; hence for this probabilistic approach a large number of test data is needed, which is often not available. Motivated by this lack of data, a new deterministic approach is presented for determining the lower bound of the buckling load of thin-walled cylindrical composite shells, which is derived from phenomenological test data. For the present test series, a single pre-buckle is induced by a radial perturbation load, before the axial displacement controlled loading starts. The deformations are measured using the prototype of a high-speed optical measurement system with a frequency up to 3680 Hz. The observed structural behaviour leads to a new reasonable lower bound of the buckling load. Based on test results, the numerical model is validated and the shell design is optimized by virtual testing. The results of test and numerical analysis indicate that this new approach has the potential to provide an improved and less conservative shell design in order to reduce weight and cost of thin-walled shell structures made from composite material.     

Completion of a building — Scottish practice

Architect and Planning Consultant, Alan Wightman, in consultation with Professor Donald Bishop, David Leslie and Dan Carmichael describes the procedure for handover and highlights the significance of 'delivery', including a useful checklist.