Seismic behavior and design method of ECC/RC composite structures

Abstract

Engineered Cementitious Composite (ECC) which shows prominent tensile ductility and toughness and fine multiple cracking, meets the high requirements of safety and durability of the infrastructures in a sustainable society. The seismic behavior and design method of ECC/RC composite structures were studied from the material level, member level, and structural level. On the material level, the feasibility of domestic PVA-ECC was firstly studied to reduce the production cost of ECC. Based on the micromechanics model, the mix proportion of ECC was redesigned, and domestic PVA fibers were mixed with Japanese ones at a proper proportion to develop hybrid PVA-ECC with better tensile ductility. Four-point bending test, uniaxial tensile test and uniaxial compression test were carried out to characterize the mechanical behavior of PVA-ECC. On the member level, an experimental investigation was first conducted to examine the seismic behavior of one RC column, six steel reinforced ECC columns and four ECC/RC composite columns. Hysteretic hoops, stiffness degradation and energy dissipating capacity of specimens were analyzed. Test results indicate that ECC/RC columns show better seismic performance in terms of ductility, energy dissipation capacity, and damage tolerance, compared with RC columns. Proposed constitutive model based on softened membrane model (SMM) was coded in OpenSEES platform to simulate the structural responses. Verification of the proposed model is provided through the analysis of ECC columns under reversed cyclic loading. On the structural level, an ECC/RC composite frame in which normal concrete both in beam-column joint zones and column base in the ground level was substituted with ECC, was proposed to relax the requirement of transverse reinforcement in the joint core and to improve the seismic performance of the frame. The seismic behavior of ECC/RC composite frame was evaluated through pushover analysis and incremental dynamic analysis. The seismic behavior at different performance levels of RC frame, ECC frame and ECC/RC composite frame were compared.