In this paper life cycle assessments are carried out on 30 optimized earth-retaining walls of various heights (4-13 m) and involving different permissible soil stresses (0.2, 0.3 and 0.4 MPa) in Spain. Firstly, the environmental impacts considered in the assessment method developed by the Leiden University (CML 2001) are analyzed for each case, demonstrating the influence of the wall height and permissible soil stress. Secondly, this paper evaluates the contribution range of each element to each impact. The elements considered are: concrete, landfill, machinery, formwork, steel, and transport. Moreover, the influence of the wall height on the contribution of each element over the total impact is studied. This paper then provides the impact factors per unit of concrete, steel, and formwork. These values enable designers to quickly evaluate impacts from available measurements. Finally, the influence of steel recycling on the environmental impacts is highlighted. Findings indicate that concrete is the biggest contributor to all impact categories, especially the global warming potential. However, the steel doubles its contribution when the wall heights increase from 4 m to 13 m. Results show that recycling rates affect impacts differently.

This paper represents an economic optimization of buttressed earth-retaining walls. We explore the optimum solutions using a harmony search with an intensification stage through threshold accepting. The calibration of the resulting algorithm has been obtained as a result of several test runs for different parameters. A design parametric study was computed to walls in series from 4-16 m total height. The results showed different ratios of reinforcement per volume of concrete for three types of ground fill. Our main findings confirmed that the most sensitive variable for optimum walls is the wall-friction angle. The preference for wall-fill friction angles different to 0º in project design is confirmed. The type of fill is stated as the main key factor affecting the cost of optimum walls. The design parametric study shows that the soil foundation bearing capacity substantially affects costs, mainly in coarse granular fills (F1). In that sense, cost-optimum walls are less sensitive to the bearing capacity in mixed soils (F2) and fine soils of low plasticity (F3). Our results also showed that safety against sliding is a more influential factor for optimum buttressed walls than the overturning constraint. Finally, as for the results derived from the optimization procedure, a more suitable rule of thumb to dimension the footing thickness of the footing is proposed.

This paper shows the differences between the design of a reinforced concrete structure considering two objectives to minimize; economic cost and CO2 emissions. Both objectives depend on the amount of two high carbon intensive materials: cement in the concrete and steel; therefore, these objectives are related. As the balance between steel and cement per m 3 of concrete depends on several factors such as the type of structure, this study focuses on buttressed earth-retaining walls. Another factor that determines the balance between steel and concrete is the height of the wall. Thus, the methodology considers a parametric study for optimal designs of buttressed earth-retaining walls, where one of the parameters is the wall height. One of the objectives is to show the variation in cost when CO2 is minimized, respectful of minimizing the economic cost. The findings show that wall elements under bendingcompressive strains (i.e. the stem of the buttressed retaining wall) perform differently depending on the target function. On one hand, the study reveals an upward trend of steel per unit volume of concrete in emission-optimized earth-retaining buttressed walls, compared to the cost-optimized. On the other hand, it is checked that unlike the cost-optimized walls, emission-optimized walls opt for a higher concrete class than the minimum class available. These findings indicate that emission-optimized walls penalize not only concrete volume, but also the cement content, to the extent that a higher concrete class outperforms in reduced emissions. Additionally, the paper outlines how and to what extent the design of this typology varies for the two analysed objectives in terms of geometry and amount of materials. Some relevant differences influencing the geometry of design strategies are found.

Within the framework of the new graduate degrees linked to the European Convergence, and additionally to the specific qualifications of the academic degree, a group of transverse competences to prepare students in their access to the labour market once studies finished. In several courses of the graduate degrees of Civil Engineering and Public Works 10 conceptual elements, equivalent to transverse competences, have been selected for evaluation. The transverse competence known as 'critical thinking' was assigned to two courses of the second year; namely Construction Techniques and Construction Typologies. This competence is crucial for the engineer as part of his analytical skills in the face to face of the professional life. The featured communication represents the students' perception with regard to of the critical thinking during the professional practice, and based on the construction processes and typologies. Hence, an anonymous survey about the significance of the critical thinking in their skills profile has been distributed. The poll consists of 11 questions to be rated on a Likert scale. The questions relate to activities that potentially foster the acquisition of the competence 'critical thinking'. The evaluation of the former transferable skill has become a novelty within the graduate studies at UPV, and therefore needs a continuous improvement of the evaluation work along the subsequent academic years. The methodology followed aims to extract how close the 11 activities are to one another. A factor analysis through principal components is used to identify the underlying variables or factors that explain the meaning of the correlations. A multiple regression model is proposed to explain the most correlational variables. Results have led the design of activities based on active methodologies for the assessment of the critical thinking.

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