Behaviour And Design Of Concrete Industrial Ground Floor Slabs

EPSRC Grant Final Report

Grant Number GR/L66786

Behaviour and Design of Concrete Industrial Ground Floor Slabs

S A Austin, P J Robins and J W Bishop Department of Civil & Building Engineering

December 2000

Index
page

1 2 3 4 5 6

Background Aims and Objectives Methodology Project Plan Review Industrial Collaboration Key Advancements and Achievements 6.1 6.2 6.3 6.4 6.5 LongStrip Floors Mesh Reinforced Jointed Large Area Pours Fibre Reinforced Jointed Large Area Pours Fibre Reinforced Jointless Large Area Pours Material Performance Modelling

1 1 1 3 3 5 5 9 11 11 13 14 14

7 8

The Objectives, Associated Deliverables and Dissemination Implications for Engineering Practice

References Publications written by the research team Publications not written by theresearch team Presentations

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Behaviour and Design of Industrial Concrete Ground Floors

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Background

Many businesses are reliant on the ground floor industry and are placing growing demands on ground floor performance in terms of flatness, joint integrity, reduced cracking and resistance to wear. In many buildings the floor forms the working platform, so any failurein the floor can have a significant impact on the operational performance. Much theoretical and experimental work has been carried out on the performance of floors under loads - starting with Westergaard [1], however, there has been little work on the early-life behaviour of slabs. Much of the detail design guidance currently in existence is based on unsubstantiated empirical values, which alsodate back to forms of construction which are no longer widely in use, i.e. long strip. The purpose of this research was to address this lack of understanding of the early life behaviour of industrial ground floor slabs, by instrumenting a series of commercial slabs during construction. The data from this large scale monitoring of slabs will enable the development of more robust design methods basedon a combination of full-scale empirical data and theoretical analysis. This will reduce the number and extent of failures and allow more cost effective slabs to be built. 2 Aims and Objectives

The aim of the research was to advance the understanding of how industrial concrete floors behave, through in-situ monitoring during and after construction. In particular how the early-age development ofthe concrete’s material properties can be made to interact with the joint arrangement and the climate and curing to form a lightly stressed concrete that can effectively carry the subsequent stresses due to the imposed load. The objectives are as listed in the accompanying IGR form. 3 Methodology

An extensive literature review identified: little work on the early-age behaviour of industrialfloors; a range of relevant information on thermal and moisture induced concrete movements; and several material models already in existence which were suitable for incorporation in either finite element or spreadsheet based models of concrete behaviour. Initially the ambient temperature, relative humidity (rh) and wind speed were identified as the parameters most likely to affect the behaviour ofthe slabs. Instrumentation was chosen to monitor these ambient characteristics as well as the internal temperature of the slab, and in some cases the internal rh, and dew point of the slab. The movement of the concrete and of the saw-cut joints were recorded by several types of vibrating wire (vw) strain gauges, which were chosen for their longterm stability, precision and sensitivity. Theinstruments were connected to dataloggers which stored the results until they were downloaded into a portable computer. An iterative procedure was used to develop the techniques required to locate the strain gauges correctly in the slab and to connect them reliably and efficiently to the datalogger. This was developed in the laboratory and then further refined on a trial instrumentation before embarking...