INVESTIGATE THE CARBON FOOTPRINTS OF THREE INTERMEDIATE FLOORING SYSTEMS: CROSS-LAMINATED TIMBER, SOLID CONCRETE, AND HOLLOW-CORE PRECAST CONCRETE

This paper evaluates and compares the embodied energy and embodied carbon using a Life Cycle Assessment (LCA) approach for three different intermediate floor structures, all of which use prefabricated materials—cross-laminated timber (CLT), precast hollow-core concrete, and solid concrete—to decide which floor construction materials have less environmental impact for use in the construction of a semi-detached house in the UK. The Inventory of Carbon & Energy (ICE) and the Carbon Calculator tool were used to calculate the carbon footprint from “cradle to grave” to determine whether the use of a CLT solution provides improved environmental performance over the traditional concrete solutions. The carbon footprint results indicate that the use of a hollow-core precast concrete floor system emits less carbon than the other two systems, although the concrete requires more fossil fuel input than the timber during the manufacturing process, so based on this, the footprint from cradle to gate for the timber was expected to be the less than that of the concrete. However, the results show the opposite; this is because of the differences in the material quantities needed in each system.

Optimum design of a composite floor system considering environmental and economic impacts

The composite floor system, composed of steel deck and concrete slab, generates more efficient and economical structures. On the other hand, the design of this type of structure has a high complexity level due to the consideration of several variables. In this respect, the objective of this paper is to present the formulation of the optimization problem for a composite floor system (steel and concrete) considering such environmental as economic impacts. To formulate the optimization problem, the reduction of environmental impact was adopted as an objective function - assuming the CO2 emission and the finance cost as parameters. The restrictions were taken by the limiting states imposed in standard NBR 8800:2008. The computer program was developed via Matlab R2016a and the optimization process was carried out using the Genetic Algorithm toolbox existing in this platform. Two application examples of the formulation at hand are presented: the first from the literature and the second from an existing building - in both situations the influences of different concrete compressive characteristic strengths were analyzed. The results of the optimization problem show a reduction in geometry and, consequently, in its weight. The solution found by the program reduces by up to 17.70% of CO2 emissions and 17.47% of the finance cost. When was applying different concrete compressive strengths, the optimal solution for environmental impact did not get the lowest cost. In general, the steel deck formwork obtained the highest percentage of environmental impact, while the beams and girders, with the same shape configuration, had the highest finance cost. Therefore, it is shown that the optimal design solution to CO2 emissions is not always the better solution for the finance cost.

Effects of Wall-to-Wall Supported Ceilings on Impact Sound Insulation for Use in Residential Buildings

In Korean residential buildings, floor impact sounds were reduced over the past few decades mainly through a floating floor system. However, ceiling constructions for impact sound reduction have not been applied actively because of a lack of useful information. This study focuses on the effects of wall-to-wall supported ceilings (WSC), which are designed with construction discontinuities between concrete slabs and ceilings, and the damping caused by porous absorbers for impact sound insulation. To examine the impact sound insulation according to ceiling conditions, measurements were performed in 25 floor–ceiling assemblies. The results indicate that ceiling treatment is mostly useful in reducing the floor impact sound. The floor impact sound owing to the WSC decreased by 2–7 dB and 2–8 dB in terms of the single number quantity for the tapping machine and rubber balls, respectively, compared with representative existing housing constructions wherein ceilings were attached on wooden sticks. Furthermore, the reduction effect of the WSC appeared to be more profound when it was applied to the floor–ceiling assembly with poor impact sound insulation. Thus, the WSC can be used to enhance the impact of sound insulation of existing housings without major repairs of floor structural layers.

Finite Element Analysis of Dynamic Characteristics and Bending Stiffness for Cross Laminated Timber Floor Panels with and without Openings

The aim of this paper is to present numerical investigations of dynamic characteristics and bending stiffness for cross laminated timber floor panels with and without service openings. Five-layer panels with the outer layers oriented in the longitudinal direction of the panel have been analyzed. In order to explore the full potential of this floor system using a limited number of measurements and structural tests, models based on the finite element method have been proposed, validated against experimental results and then used to investigate the effect of opening position in the floor on main structural performance parameters. The results showed that, when the need for additional service opening appears, a slight decrease of the main structural characteristics of the cross laminated timber floor panels is achievable with an adequate geometrical position of the opening in the floor.