Modeling construction time in Spanish building projects

The literature states that project duration is affected by various scope factors. Using 168 building projects carried out in Spain, this paper uses the multiple regression analysis to develop a forecast model that allows estimating project duration of new builds. The proposed model uses project type, gross floor area (GFA), the cost/GFA relationship and number of floors as predictor variables. The research identified the logarithmic form of construction speed as the most appropriate response variable. GFA has greater influence than cost on project duration but both factors are necessary to achieve a forecast model with the highest accuracy. We developed an analysis to verify the stability of forecasted values and showed how a model with high values of fit and accuracy may display an anomalous behavior in the forecasted values. The sensitivity of the proposed forecast model was also analyzed versus the variability of construction costs.

Presencia del olmo temblón o negrillo, Ulmus laevis Pall. en Ibi (Alicante, Comunidad Valenciana)

Se ha localizado en la Rambla de la Gavarnera en Ibi, Alicante una pequeña población de Ulmus laevis Pall., que no había sido citado expresamente en localidades valencianas, ni en las floras locales, regionales, ni nacionales, en unos casos por no haberse localizado, en otros por considerar a este árbol alóctono en España. Desde hace una década un equipo de la ETSIA de Montes de la Universidad Politécnica de Madrid, viene realizando diversos proyectos y tesis doctorales que han dado como resultado la puesta en valor de esta especie, a través de su localización a nivel nacional, estudio ecológico, fisiológico y genético, que arrojan numerosas pruebas a favor de la autoctonía de esta especie en España. Según los autores de este dilatado proyecto, U. laevis habría tenido en España uno de su principales refugios cuaternarios, aunque en la actualidad se encuentre fragmentado en poblaciones dispersas, con pocos individuos y problemas para su conservación y supervivencia. No obstante esta especie ha demostrado mayores tasas de supervivencia a la enfermedad de los olmos, que otros de sus congéneres como Ulmus minor y U. glabra. En cuanto a su presencia en Alicante, son precisamente estos autores los que localizan un primer ejemplar en Ibi, al que ahora añadimos dos ejemplares más repartidos en tres puntos muy próximos y situados a lo largo de la Rambla de la Gavarnera. Este es un cauce irregular pero con nivel freático permanente, como lo atestiguan la existencia de pozos, azudes, albercas que abastecieron a los pequeños regadíos de la zona, muchos de ellos abandonados en la actualidad. Dada la rareza de esta especie a nivel nacional y la excepcionalidad de su presencia en Ibi, consideramos que el ejemplar de mayor porte merece la consideración de árbol singular para la Comunidad Valenciana y por otra parte, los otros ejemplares merecen su protección y multiplicación, para incrementar la población existente. Es necesario desarrollar un mayor esfuerzo de localización en este paraje y zonas próximas de la Comarca, para conocer su potencial distribución en la provincia y determinar un estatus de protección adecuado.

The Impact of BIM on the Distribution of Cost and Return on Investment in UK Construction Projects

It has been widely documented that when Building Information Modelling (BIM) is used, there is a shift in effort to the design phase. Little investigation into the impact of this shift in effort has been done and how it impacts on costs. It can be difficult to justify the increased expenditure on BIM in a market that is heavily driven by costs. There are currently studies attempting to quantify the return on investment (ROI) for BIM for which these returns can be seen to balance out the shift in efforts and costs to the design phase. The studies however quantify the ROI based on the individual stakeholder’s investment without consideration for the impact that the use of BIM from their project partners may have on their own profitability. In this study, a questionnaire investigated opinions and experience of construction professionals, representing clients, consultants, designers and contractors, to determine fluctuations in costs by their magnitude and when they occur. These factors were examined more closely by interviewing senior members representing each of the stakeholder categories and comparing their experience in using BIM within environments where their project partners were also using BIM and when they were not. This determined the differences in how the use and the investment in BIM impacts on others and how costs are redistributed. This redistribution is not just through time but also between stakeholders and categories of costs. Some of these cost fluctuations and how the cost of BIM is currently financed are also highlighted in several case studies. The results show that the current distribution of costs set for traditional 2D delivery is hindering the potential success of BIM. There is also evidence that stakeholders who don’t use BIM may benefit financially from the BIM use of others and that collaborative BIM is significantly different to the use of ‘lonely’ BIM in terms of benefits and profitability.