Dimitrios N. Kaziolas

Life Cycle Analysis and Optimization of a Steel Building

The present study seeks to couple the problem of the structural optimization of building frames, with that of the optimization of design options for their energy efficiency. The objective function is a cost function that takes into account both the structural cost and energy performance along the whole life of the building. Consequently, the following design parameters are involved: insulation thickness, wall and window insulation profile, window sizes, heating and air conditioning system sizing, sizing of steel cross-sections, as well as parameters related to the life cycle of the building. Modeling is based on acceptable from national and European regulations procedures. Optimization is solved using evolutionary algorithms. The optimization problem is implemented on a steel office building (\(10\times 15\) m), in Chania, Crete, at the south part of Greece. This is a first attempt to combine Life Cycle Cost and Optimization with classical Structural Optimization for steel structures. Depending on the requirements from the users of the building further evaluation using building energy management system (BEMS) for the intelligent operation and management of heating, ventilation and air-conditioning (HVAC) may be performed.

Analysis of steel bolted connections by means of a nonsmooth optimization procedure

A nonsmooth optimization procedure is herein proposed for the investigation of the bearing resistance of steel bolted connections. Taking into account the presence of nonlinear effects such as e.g. plasticity and interface interaction, and describing the resistance in bearing strength by means of a nonmonotone multi-valued reaction-displacement law obtained by experimental testing, the problem is formulated as a hemivariational inequality one. The latter is equivalent to a substationarity problem of the potential energy of the connection under investigation. This problem can be effectively treated numerically by applying an appropriately chosen nonconvex, nonsmooth optimization algorithm and in particular, the NSOLIB optimization algorithm based on the proximal bundle method has been applied. Two numerical examples whose results are compared to experimental testing results demonstrate the effectiveness of the proposed method.

Evolution of Environmental Sustainability for Timber and Steel Construction

The movement for sustainable development aims at the optimization of the whole of human activity in terms of environmental, economic and social impact. The aim of the present paper is the examination of the content and evolution of environmental sustainability in order to identify the key implications and requirements regarding timber and steel structures, two fields with significant potential in terms of sustainability. The conclusions drawn include the identification of issues such as raw materials, the construction stage of a project and waste management and their potential influence on the environmental sustainability of timber and steel construction.

Influence of biotic factors on the mechanical properties of wood, taking into account the time of harvesting

Abstract The aim of the present paper is to investigate the influence of biotic factors (fungi and insects) on the mechanical properties of wood through the effect of blue-stain, taking into account the time of harvesting and the time of stay of wood in the forest. Specifically, the resistance to axial compression and to bending (modulus of rupture (MOR)) was studied using infected specimens of Scots Pine (Pinus sylvestris) and Norway Spruce (Picea abies) (the usual types of wood used in woodwork). The specimens were obtained from logs of Scots Pine and Norway Spruce that were harvested in three different seasons of year, namely in July 2012, November 2012 and June 2013, respectively, in the forest of Elatia-Greece, and the attack pace by biotic factors with respect to the time of logging was studied. The placement of the experimental surfaces of each type of tree was made on skid road and in the stand. Totally, 120 laboratory measurements in axial compression and 120 measurements in bending (MOR) took place. The results proved that blue-stain hardly affect the mechanical properties of both wooden species and particularly the specimens that were derived during the winter logging.

LCA of timber and steel buildings with fuzzy variables uncertainty quantification

Steel and timber structures constitute a construction technology which holds significant potential in terms of sustainability and are therefore selected as sustainable solutions for the construction of housing, commercial or other types of building projects. This paper consists of two parts. Firstly, to quantify the sustainability potential of timber and steel construction by calculating the environmental impact caused throughout the life cycle of a steel-framed residential building and a timber building. The calculation has been extended with the usage of fuzzy variables that represent uncertainty of the various parameters involved.

Quantification of the influence of life cycle parameters on the total environmental impact of steel-framed buildings

Abstract Due to the increased urgency with which environmental issues are currently being prioritized, business sectors such as construction, that have been identified as one of the largest consumers of raw materials and energy, are actively involved in research aiming to optimize construction processes and products in terms of environmental impact. Although researchers have pointed out various issues and aspects of a construction project’s delivery process that can significantly affect its environmental impact, the extent to which these issues can influence the total environmental impact of the project is unclear. The current research aims to investigate and eventually quantify the influence of a number of such parameters, utilizing an existing steel-framed building as the basis for the necessary calculations. The conclusions drawn illustrate the actual extent of the influence of the examined life cycle parameters, while also offering specific insight in regard to the determination of criteria that can be used as the basis for recommendations for similar projects.

On the Separation Zones in Aluminium Base-Plate Connections. Numerical Simulation and Laboratory Testing

The present paper deals with the study of the separation problem under combined loading conditions of aluminium base-plate connections. The classical unilateral contact law of Signorini is applied in order to describe the contact conditions between the contact surfaces and the separation process along the connection. Thus the problem is formulated as a variational inequality that expresses the principle of virtual work of the connection at the state of equilibrium, where the unilateral contact is included in the formulation. The application of an appropriate finite element discretization scheme leads to the formation of a quadratic optimization programming problem which is coupled by inequality constraints with respect to the displacements. The latter problem expresses from the standpoint of mechanics, the principle of minimum potential energy of the connection at the state of equilibrium. The aforementioned problem can be numerically and effectively treated by the application of two easy–to–use solution strategies based on quadratic optimization algorithms. This technique is illustrated by means of a numerical application. Due to the great significance of the problem, laboratory testing has been carried to extensively investigate the phenomenon. The numerical results are compared with respective laboratory testing results.

A Hemivariational Inequality and a Nonconvex Energy Bundle Approach to the Problem of Debonding in Adhesively Bonded Composite Structures

In the present paper the problem of debonding in adhesively bonded composite structures is examined. The main reason that leads to the damage of these structures is the delamination effect due to the considered external loading. The adhesive material is assumed to obey to a nonmonotone, possibly multivalued three-dimensional stress-strain law. This kind of behaviour results in a nonconvex nonsmooth energy function in the problem introducing a hemivariational inequality that is the expression of the principle of virtual work in inequality form. This problem is equivalent to a substationarity problem of the minimum of potential energy of the structure that is an optimization problem. The application of the optimization programme NSOLIB, based on the proximal bundle method, converges to one at least substationarity point which is a solution of the problem at hand. In the last part of the paper the study of a steel frame and a composite two-layered structure demonstrates the effectiveness of the proposed method.

Structural failure study of laminated composites: the bundle optimization approach

Abstract A nonconvex energy bundle method for the structural failure study of composite structures is herein proposed. To describe the evolution of failure phenomena, two different simulations are considered: The first simulation defines a priori known critical surfaces in the structure called interfaces, assuming that their behavior obeys nonmonotone possible multivalued constitutive laws including all the nonlinearities of the structure, while the rest of the structure behaves linear-elastically. The second simulation analyses the considered structures assuming that their behavior can be described in a macroscopic way through nonmonotone possibly multivalued stress–strain or reaction–displacement laws. The selection of the suitable simulation depends on the problem. Nonmonotone stress–strain or reaction–displacement constitutive or boundary laws are the result of nonconvex–nonsmooth energy potentials. In this case they lead to hemivariational or “Panagiotopoulos” inequalities, which are expressed as the principle of virtual and complementary work in inequality form and are equivalent to a substationarity problem of the potential or the complementary energy of the structure. The numerical treatment of this problem is achieved through the optimization program NSOLIB based on the proximal bundle method which is capable to handle nonsmooth and nonconvex energy potentials. By means of this program at least one substationarity point is obtained that represents an equilibrium position of the structure. In the last part of the paper, four numerical applications are presented that illustrate the effectiveness of the proposed method.