Analysis of labour productivity of formwork operations in building construction

Nomemclature

AI=Artificial intelligence

ANN=Artificial neural network

BLDG.=Building

BPNN=Back propagation neural network

DP=Daily productivity

F =Floor level

G =Gang size

kms/hr=Kilometers per hour

L =Percent labour

M =Work method

m² /man-hr=Meter square per man-hour

MAE=Mean absolute error

MSE=Mean square error

n =No of data points or input patterns

NN=Neural networks

P =Precipitation

Ppt.=Precipitation

R² =Coefficient of multiple determination

T =Temperature

TW=Work type

W =Wind speed

Introduction

The importance of labour productivity in construction arises from its impact on completing projects within their targeted time and cost. For instance, contractors have often focused on labour productivity rates as the primary source of the overall success or failure of a project ([13] Missbauer and Hauber, 2006). Contractors at the bidding stage of a project are interested in knowing site labour productivity figures, to estimate the labour cost component of the project. Thereafter, if the contract is awarded to the contractor, the company needs to ensure that the estimated level of productivity is achieved or bettered. It was widely believed, in the construction industry, that productivity exhibited decline over the past few decades ([3] Brisco, 1988, [4] Christian and Hachey, 1995). Later, however, some microeconomic studies ([2] Allmon et al. , 2000), reported the contrary. Irrespective of productivity trends, a relatively recent research cautioned against unreliability in labour productivity raw data and the uncertainties inherent in the methods used for its estimation and interpretation ([8] Eddy and Peerapong, 2003).

Though extensive research has been done on parameters influencing productivity, most focused on determinants that have mid- or long-term impacts on labour productivity ([1] AbouRizk et al. , 2001; [6] Crawford and Vogl, 2006; [12] Lam et al. , 2001; [16] Moselhi et al. , 1997; [20] Thomas, 1992; [22] Thomas and Zavrski, 1999). Considerably less number of studies have targeted individual; not multiple factors, that cause daily or short-term variations in productivity ([9] Hancher and Abd-Elkhalek, 1998; [11] Koehn and Brown, 1985; [21] Thomas and Sakarcan, 1994; [19] Sanders and Thomas, 1993; [14] Mohamed, 2005). The aim of this paper is to study labour productivity in building construction with a focus on formwork operations and to quantify its variations due to daily changes of factors considered to have direct impact on labour productivity. This paper presents...