Novel discrete diaphragm system of concrete high-rise modular buildings

Abstract

Modular high-rises are attractive for metropolises, but few applications exist, partly due to the lack of knowledge about their lateral behaviors. Existing concrete modular high-rises usually adopt a time-consuming and labor-intensive cast-in-situ concrete layer on modules to satisfy the continuous rigid diaphragm assumption. This study aims to develop an innovative discrete diaphragm system for concrete modular high-rises without a cast-in-situ concrete layer. A private residential building in Hong Kong (HK) was selected as the case building, in which the novel horizontal and vertical connection designs were proposed. A simplified spring model considering in-plane axial and shear behaviors was proposed to simulate the horizontal connections. A three-dimensional finite element model of the case building with discrete diaphragms was established using the spring model. A parametric study was conducted to examine the influence of horizontal connections on the deflection and natural periods of the case building under the HK code-specified wind loads. A comparative study was conducted using five cases with different connection stiffness sets to systematically investigate the influence of horizontal connections on the structural responses of the case building under the wind loads. Results show that the discrete diaphragm system is feasible for concrete modular high-rises in HK. Effects of horizontal connections on the lateral behavior of concrete modular high-rises should be considered in the structural design when the discrete diaphragms are adopted. This study breaks through the continuous rigid diaphragm assumption and proves that appropriate flexible horizontal connections are a feasible option for concrete modular high-rises under wind loads.