Construction Technology 3 D39 TA Dr Mohamed Abdel-Wahab Edwin Chadwick Building, Room Lecture 5: Factory production (Pre-cast concrete)

WeekTopic 1Introduction to the module Part I: Offsite production 2 University is closed on Monday 19 September (NO lecture this week but there is a lecture on Thursday) An overview of MMC 3Types of offsite production 4Case studies and practical issues 5Factory production Part II: Modern methods for substructure and superstructure construction 6Foundations 7Basements 8 External Walls and insulation Guest Lecture (3 November) 9Project week 10Structural frames and Tall buildings Part III: Innovative methods for construction 11Construction automation and free form construction 12Revision

Go to m.socrative.com

Quiz 1)What are the general issues associated with offsite production? 2)How to know that the workers on-site are qualified? 3)What is CSkills and what do they do?

Lecture Outline 1)Introduction 2)Issues to consider 3)Production method

Modern pre-cast concrete frames offers design flexibility.

Closed v open environment PRECAST FACTORY PRODUCTION

Production of reinforcement cages and main connections Assembly of reinforcement

Buildability Quality and accuracy Structural efficiency (pre-stressed concrete) Issues to consider

Pre-stressed concrete Source: Pre-stressed concrete – Designer’s Handbook The cross-section of the member can be smaller, since the whole of the concrete is put to structural use; and the resistance of beams to shearing and flexural cracks is considerably increased. It is therefore possible to design longer spans or cantilevers using comparatively shallow and slender sections.

Examples of pre-stressed concrete sections produced in a factory

The elimination of beams and columns Reduced on site labour costs Utilising floor area for high density parking Elimination of formwork and scaffolding Early access to following trades; and Speed of construction. What are the implications for using long span planks?

Maximum flexibility is obtained in floor layouts by eliminating load- bearing components. Spans up to 17m give clear, uncluttered space Precast columns and beams used to complement the long span Hollow Core planks.

More issues to consider Production programming When the dates for phased deliveries to site are agreed, the components will be produced in a predetermined sequence to ensure that matured concrete components are ready for instant erection.

Supply of steel reinforcement

PRODUCTION METHOD Placing carefully specified concrete into mould Compaction of concrete using poker vibrator

Fixings for services Pre-stressed v reinforced concrete Concrete with Zero slump! Finishes from the mould Curing

HANDLING AND STORAGE

Prestressed double-tee unit being moved to the storage area

Quality control Verification of supply Aggregate testing Testing for workability

The certification process can take over a year and cost up to £100,000, meaning that not all companies apply! Testing the performance of building products is imperative.

QUALITY ASSURANCE BRITISH STANDARDS INSTITUTION. BS 5750 Quality systems. Part 1 : Specification for the design, development, production, installation and servicing. Milton Keynes, BSI, pp. Quality is not only about the production process itself, but also it relates to conformance to the project requirements as set-out by the client.

Pre-stressed / Precast Plant Tour

Construction stages of precast wall

Summary 1)Introduction 2)Issues to consider 3)Production method

Suggested references Superior Walls by Weaver Precast