Víctor Yepes

Multiobjective Optimization of Concrete Frames by Simulated Annealing

This article aims to describe a methodology to design RC building frames based on a multiobjective simulated annealing (MOSA) algorithm applied to four objective functions, namely, the economic cost, the constructability, the environmental impact, and the overall safety of RC framed structures. The evaluation of solutions follows the Spanish Code for structural concrete. The methodology was applied to a symmetrical building frame with two bays and four floors. This example has 77 design variables. Pareto results of the MOSA algorithm indicate that more practical, more constructable, more sustainable, and safer solutions than the lowest cost solution are available at a cost increment acceptable in practice. Results N s -SMOSA1 and N s -SMOSA2 of the cost versus constructability Pareto front are finally recommended because they are especially good in terms of cost, constructability, and environmental impact. Further, the methodology proposed will help structural engineers to enhance their designs of building frames.

Design of reinforced concrete bridge frames by heuristic optimization

This paper deals with the economic optimization of reinforced concrete box frames used in road construction. It shows the efficiency of four heuristic algorithms applied to a problem of 50 design variables. Heuristic methods used are the random walk and the descent local search. The metaheuristic methods are the threshold accepting and the simulated annealing. The four methods have been applied to the same frame of 13 m of horizontal span. The comparison of the four heuristic algorithms leads to the conclusion that the proposed threshold accepting is more efficient, since it improves cost results of the random walk and descent local search by 7.5% and 1.4%, respectively, while improving deviation of random results of the simulated annealing. Finally, the inclusion of the deflections and fatigue limit states appears to be crucial, since their ignorance leads to 3.9% more economic but unsafe results.

Organizational Improvement Through Standardization of the Innovation Process in Construction Firms

Abstract: The purpose of this article is to identify the drivers, success factors, benefits, and barriers to innovation in a medium size construction firm with a standardized innovation management system. The case study method is used to compare theory to reality from different perspectives, building explanations from a Spanish contractor observed over a three year period. Findings suggest that innovation management can be standardized, which leads to an organizational improvement for the company, and at the same time this improvement facilitates organizational problem-solving on a regular basis, increasing technical capabilities, knowledge management, business profit, and client satisfaction. The framework described in this research aims to provide guidance for managers, thus they can innovate in a systematic way; however, this exploratory study has still to be validated by empirical investigations on a larger scale through a significant number of certified companies, which is currently not yet the case in the Spanish construction industry.

Design of reinforced concrete road vaults by heuristic optimization

This paper aims at the automatic design and cost minimization of reinforced concrete vaults used in road construction. This paper presents three heuristic optimization methods: the multi-start global best descent local search (MGB), the meta-simulated annealing (SA) and the meta-threshold acceptance (TA). Penalty functions are used for unfeasible solutions. The structure is defined by 49 discrete design variables and the objective function is the cost of the structure. All methods are applied to a vault of 12.40m of horizontal free span, 3.00m of vertical height of the lateral walls and 1.00m of earth cover. This paper presents two original moves of neighborhood search and an algorithm for the calibration of SA-TA algorithms. The MGB algorithm appears to be more efficient than the SA and the TA algorithms in terms of mean results. However, the SA outperforms MGB and TA in terms of best results. The optimization method indicates savings of about 10% with respect to a traditional design.

Model for Systematic Innovation in Construction Companies

AbstractThe reasons that drive construction companies to innovate, as well as the processes they use, have not yet been fully explored in the construction management literature. This paper describes the “hows” and “whys” behind the push for innovation in a construction company. The research method is founded on the validation of a model developed by a case study; this is focused on a medium-sized construction company which implemented and certified an innovation management system, as established by a Spanish standard. The studies conducted by the authors over a five-year period generated a set of 18 propositions reflecting an explanatory model of innovation management. This paper reports on the external validation of this model by means of a set of interviews; the results fully corroborate 15 of these propositions. The strongest drivers of innovation in construction companies are technical problems in construction projects, client requirements, and upper management. Innovation opportunities are identified...

Optimization of concrete I-beams using a new hybrid glowworm swarm algorithm

In this paper a new hybrid glowworm swarm algorithm (SAGSO) for solving structural optimization problems is presented. The structure proposed to be optimized here is a simply-supported concrete I-beam defined by 20 variables. Eight different concrete mixtures are studied, varying the compressive strength grade and compacting system. The solutions are evaluated following the Spanish Code for structural concrete. The algorithm is applied to two objective functions, namely the embedded CO2 emissions and the economic cost of the structure. The ability of glowworm swarm optimization (GSO) to search in the entire solution space is combined with the local search by Simulated Annealing (SA) to obtain better results than using the GSO and SA independently. Finally, the hybrid algorithm can solve structural optimization problems applied to discrete variables. The study showed that large sections with a highly exposed surface area and the use of conventional vibrated concrete (CVC) with the lower strength grade minimize the CO2 emissions.

Employability of Graduate Students in Construction Management

AbstractThe economic crisis that currently affects some Western countries has reduced the employability of graduates in the construction industry. Nevertheless, many young professionals consider this situation as an opportunity to further their training, thus the higher enrollment in graduate programs in the construction industry. In light of this scenario, the authors of this paper sought to identify students’ perceptions of training gaps that affect their employability. The research was based on a case study, conducted in a Spanish graduate program (M.Sc.) in construction management during two consecutive academic years; a questionnaire survey was given to all of the enrolled students at the beginning of the first semester. The statistical analyses consisted of a principal-component analysis of the 21 variables listed as possible explanations for their graduates’ unemployment and an analysis of variance based on the previously noted principal components. Respondents recognized the intrinsic internal bar...

Social Sustainability in the Lifecycle of Chilean Public Infrastructure

AbstractTo enhance concern for the social aspects of sustainability and to delineate the criteria to be considered at each stage of the lifecycle of an infrastructure, this paper aims to determine the relevance of a set of criteria that evaluate social sustainability throughout the lifecycle of a public civil infrastructure. This research presents the results of a case study applying the Delphi method to 24 Chilean experts consulted in a series of three rounds. In addition, binomial statistical tests and Kendall’s coefficient were used to show the convergence of the experts. Thus, it was identified that of 36 initial criteria assessed at each stage of the lifecycle, the consideration of 20 is required at the design stage, 29 at the construction stage, 33 during operation, and 27 at demolition. The most relevant criteria, per lifecycle stage, were Stakeholder Participation (design and demolition stages), External Local Population (design stage), Internal Human Resources (construction and demolition stages)...

Current models and practices of economic and environmental evaluation for sustainable network-level pavement management

Ground transportation infrastructures, particularly road infrastructure, are essential for economic and social development. The quality level that the user perceives is mainly determined by the pavement condition. More than 400 billion dollars are invested globally each year in pavement construction and maintenance; these tasks increase by 10% the environmental impact generated by vehicle operation. Therefore, a sustainable approach should be incorporated in the assessment of preservation alternatives that consider technical, economic, environmental, political and institutional aspects in an integrated manner over their life-cycle. The purpose of the present research is to examine the models and practices for the economic and environmental evaluation of pavement assets, in order to analyze the advantages and limitations of the current state of the practice and identify the opportunities to improve their sustainable management. One of the main limitations identified is the lack of models that consider the economic and environmental aspects integrally. A need for models which consider the impact on users in work zones, as well as the use of new technologies and recycled materials that are more respectful of the environment, has been detected.

Memetic Algorithm Approach to Designing Precast-Prestressed Concrete Road Bridges with Steel Fiber Reinforcement

AbstractThis paper describes the influence of steel fiber-reinforcement on the design of cost-optimized, prestressed concrete, precast road bridges, with a double U-shaped crosssection and isostatic spans. A memetic algorithm with variable-depth neighborhood search is applied to the economic cost of these structures at different stages of manufacturing, transportation, and construction. The problem involved 41 discrete design variables for the geometry of the beam and the slab, materials in the two elements, active and passive reinforcement, as well as residual flexural tensile strength corresponding to the fibers. The use of fibers decreases the mean weight of the beam by 1.72% and reduces the number of strands an average of 3.59%, but it increases the passive reinforcement by 8.71% on average, respectively. Finally, despite the higher cost of the fibers, their use is economically feasible since the average relative difference in cost is less than 0.19%.