ENVIRONMENTAL IMPACT OF STRUCTURAL MODIFICATIONS IN OFFICE FLOORS TO SATISFY VIBRATION SERVICE ABILITY

摘要

Modern office floors (featuring slender slabs, longer spans, open-plan spaces, less furniture) are increasingly susceptible to walking-induced excessive vertical vibrations. Therefore, vibration serviceability has become the governing design criterion for office floor structures. Structural modifications are normally performed to tackle this problem, but they considerably increase the amount of construction materials needed, which is directly linked to the embodied energy (EE) and embodied carbon (EC) in floor design. In fact, reduction of EE and EC is becoming a necessary feature in building construction due to urgent global sustainability issues. However, structural modifications are frequently carried out with no optimisation analysis, resulting in reduced sustainability of office floor design. This paper investigates the environmental impact of structural modifications to satisfy vibration serviceability, in terms of embodied energy and carbon, for a finite element model of a steel-concrete composite office floor, featuring a trapezoidal steel deck supported by downstanding steel beams. The original floor design has minimal structural dimensions to comply with all design criteria (i.e. strength, thermal comfort, acoustic insulation, fire protection, maximum deflection), except for vibration serviceability under walking-induced loads. The desktop study was performed by employing structural modifications in the slab depth and beam profiles until the response factor of 4 was achieved over the whole floor area, for pacing frequencies from 1.4 Hz to 2 Hz. Results showed that the compliant floor design nearly features 14 %, 27 % and 37 % extra EE, EC and structural weight (SW), respectively, compared with their counterparts in the original design. This is one of very few studies in the public domain demonstrating the huge financial and environmental costs of meeting current vibration serviceability criteria for office floors.