Multi-Storey Precast Concrete Framed Structures

Kim S. Elliott, Colin Jolly

• Publisher: Wiley-Blackwell
• Year: 2013
• Print ISBN: 9781405106146
• eBook ISBN: 9781118587355
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

Precast reinforced and prestressed concrete frames provide a high strength, stable, durable and robust solution for any multi-storey structure, and are widely regarded as a high quality, economic and architecturally versatile technology for the construction of multi-storey buildings. The resulting buildings satisfy a wide range of commercial and industrial needs. Precast concrete buildings behave in a different way to those where the concrete is cast in-situ, with the components subject to different forces and movements. These factors are explored in detail in the second edition of Multi-Storey Precast Concrete Framed Structures, providing a detailed understanding of the procedures involved in precast structural design. This new edition has been fully updated to reflect recent developments, and includes many structural calculations based on EUROCODE standards. These are shown in parallel with similar calculations based on British Standards to ensure the designer is fully aware of the differences required in designing to EUROCODE standards.

Civil and structural engineers as well as final year undergraduate and postgraduate students of civil and structural engineering will all find this book to be thorough overview of this important construction technology.

CHAPTER 1

Precast Concepts, History and Design Philosophy

The background to the relevance of precast concrete as a modern construction method for multi-storey buildings is described. The design method is summarised.

1.1 A Historical Note on the Development of Precast Frames

Precast concrete is not a new idea. William H. Lascelles (1832–85) of Exeter, England devised a system of precasting concrete wall panels, 3 ft × 2 ft × 1 inch thick, strengthened by forged, ¹/₈ inch-square iron bars. The cost was 3d (£0.01) per ft². Afterwards, the notion of ‘pre-casting’ concrete for major structural purposes began in the late nineteenth century, when its most obvious application – to span over areas with difficult access – began with the use of flooring joists. François Hennebique (1842–1921) first introduced precast concrete into a cast-in situ flour mill in France, where the self-weight of the prefabricated units was limited to the lifting capacity of two strong men! White [1.1] and Morris [1.2] give good historical accounts of these early developments.

The first precast and reinforced concrete (rc) frame in Britain was Weaver’s Mill in Swansea. In referring to the photograph of the building, shown in Figure 1.1, a historical note states: … the large building was part of the flour mill complex of Weaver and Co. The firm established themselves at the North Dock basin in 1895–6, and caused the large ferro-concrete mill to be built in 1897–98. It was constructed on the system devised by a Frenchman, F. Hennebique, the local architect being H. C. Portsmouth … At this time Louis Gustave Mouchel (1852–1908, founder of the Mouchel Group) was chosen to be Hennebique’s UK agent. Mouchel used a mix of cast-in situ and prefabricated concrete for a range of concrete framed structures, building at the rate of 10 per year for the next 12 years.

Figure 1.1 Weaver’s Mill, Swansea – the first precast concrete skeletal frame in the United Kingdom, constructed in 1897–98

(courtesy of Swansea City Archives).

The structure was a beam-and-column skeletal frame, generally of seven storeys in height, with floor and beams spans of about 20 feet. The building has since been demolished owing to changes in land utilisation, but as a major precast and reinforced concrete construction it pre-dates the majority of early precast frames by about 40 years.

Bachmann and Steinle [1.3] note that the first trials in structural precast components took place around 1900, for example at Coignet’s casino building in Biarritz in 1891, and Hennebique and Züblin’s signalman’s lodge in 1896, a complete three-dimensional cellular structure weighing about 11 tons [1.3].

During the First World War storehouses for various military purposes were prefabricated using rc walls and shells. Later, the 1930s saw expansions by companies such as Bison, Trent Concrete and Girling, with establishments positioned close to aggregate reserves in the Thames and Trent Valley basins. The reason why precast concrete came into being in the first place varies from country to country. One of the main reasons was that availability of structural timber became more limited. Some countries, notably the Soviet Union, Scandinavia and others in northern Continental Europe, which together possess more than one-third of the world’s timber resources but experience long and cold winters, regarded its development as a major part of their indigenous national economy. Structural steelwork was not a major competitor at the time outside the United States, since it was batch-processed and thus relatively more expensive.

During the next 25 years developments in precast frame systems, prestressed concrete (psc) long-span rafters (up to 70 feet), and precast cladding increased the precasters’ market share to around 15 per cent in the industrial, commercial and domestic sectors. Influential articles in such journals as the Engineering News Record encouraged some companies to begin producing prestressed floor slabs, and in order to provide a comprehensive service by which to market the floors these companies diversified into frames. In 1960 the number of precast companies manufacturing major structural components in Britain was around thirty. Today it is about eight.

Early structural systems were rather cumbersome compared with the slim-line components used in modern construction. Structural zones of up to 36 inches, giving rise to span/depth ratios of less than 9, were used in favour of more optimised precasting techniques and designs. This could have been called the ‘heavy’ period, as shown in C. Glover’s now classic handbook Structural Precast Concrete [1.4]. Some of the concepts shown by Glover are still practised today and one cannot resist the thought that the new generation of precast concrete designers should take heed of books such as this. It is also difficult to avoid making comparisons with the ‘lighter’ precast period that was to follow in the 1980s, when the saving on total building height could, in some instances, be as much as 100 to 150 mm per floor.

Attempts to standardise precast building systems in Britain led to the development of the National Building Frame (NBF) and, later, the Public Building Frame (PBF). The real initiative in developing these systems was entrenched more in central policy from the then Ministry of Public Building and Works than by the precasting engineers of the building industry. The NBF was designed to provide: … a flexible and economical system of standardised concrete framing for buildings up to six storeys in height. It comprises a small number of different precast components produced from a few standard moulds [1.5].

The consumer for the PBF was the Department of Environment, for use within the public sector’s expanding building programme of the 1960s. Unlike the NBF, which was controlled by licence, the PBF was available without patent restrictions to any designer. The structural models were simple and economical: simply supported, long-span, prestressed concrete slabs up to 20 inches deep were half recessed into beams of equal depth. By controlling the main variables, such as loading (3+1 kN/m² superimposed was used throughout), concrete strength and reinforcement quantities, limiting spans were computed against structural floor depths. Figures 1.2 and 1.3 show some of the details of these frames. Diamant [1.6] records the international development of industrialised buildings between the early 1950s and 1964. During this period the authoritative Eastern European work by Mokk [1.7] was translated into English, and with it the documentation of precast concrete had beg...

Table of contents

• Cover
• Title page
• Copyright page
• Preface
• Notation
• CHAPTER 1 Precast Concepts, History and Design Philosophy
• CHAPTER 2 Procurement and Documentation
• CHAPTER 3 Architectural and Framing Considerations
• CHAPTER 4 Design of Skeletal Structures
• CHAPTER 5 Design of Precast Floors Used in Precast Frames
• CHAPTER 6 Composite Construction
• CHAPTER 7 Design of Connections and Joints
• CHAPTER 8 Designing for Horizontal Load
• CHAPTER 9 Structural Integrity and the Design for Accidental Loading
• CHAPTER 10 Site Practice and Temporary Stability
• References
• Index