Ze Chang

Ze Chang
Delft University of Technology | TU · Department of Geoscience and Engineering

Phd candidate of TU Delft

About

21
Publications
8,201
Reads
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278
Citations
Citations since 2017
21 Research Items
280 Citations
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
Introduction
The incremental method and geometric nonlinearity are incorporated into lattice model for buildability quantification; the printing parameters including the non-uniform gravitational load, deformed geometry, localized damage and material heterogeneity, are first studied for structural instability; the elastic buckling, plastic collapse, and combined failure modes during the printing process can be reproduced;

Publications

Publications (21)
Article
Full-text available
In this paper, optimization of vascular structure of self-healing concrete is performed with deep neural network (DNN). An input representation method is proposed to effectively represent the concrete beams with 6 round pores in the middle span as well as benefit the optimization process. To investigate the feasibility of using DNN for vascular str...
Article
Full-text available
Generative networks are effective tools for digital materials (DM) inverse design. However, the optimization performance of generative networks is restricted by the increasing discrepancy between the optimized input and the prescribed input domain as the design loop increases. Herein, a correction technique is incorporated into generative deep neur...
Article
Full-text available
This paper explores buildability quantification of randomly meshed 3D printed concrete objects by considering structural failure by elastic buckling. The newly proposed model considers the most relevant printing parameters, including time-dependent material behaviors, printing velocity, localized damage and influence of sequential printing process....
Article
Full-text available
Early‐age stress (EAS) is an important index for evaluating the early‐age cracking risk of concrete. This paper encompasses a thermo‐chemo‐mechanical (TCM) model and active ensemble learning (AEL) for predicting the EAS evolution. The TCM model provides the data for the AEL model. First, based on Fourier's law, Arrhenius’ equation, and rate‐type cr...
Article
Full-text available
Tailoring lattice structures is a commonly used method to develop lattice materials with desired mechanical properties. However, for cementitious lattice materials, besides the macroscopic lattice structure, the multi-phase microstructure of cement paste may have substantial impact on the mechanical responses. Therefore, this work proposes a multi-...
Article
Full-text available
This research studies the impact of localized damage and deformed printing geometry on the structural failure of plastic collapse for 3D concrete printing (3DCP) using the lattice model. Two different approaches are utilized for buildability quantification: the (previously developed) load-unload method, which updates and relaxes the printing system...
Article
Full-text available
Extrusion-based 3D concrete printing (3DCP) results in deposited materials with complex microstructures that have high porosity and distinct anisotropy. Due to the material heterogeneity and rapid growth of cracks, fracture analysis in these air-void structures is often complex, resulting in a high computational cost. This study proposes a convolut...
Article
Full-text available
A good bond between the layers of 3D printed cementitious materials is a prerequisite for having high structural rigidity for the printed elements. However, the influence of printing process on an interlayer bond is still not well understood. This study investigates the influence of curing methods (i.e., air curing, plastic film covering, wet towel...
Article
Full-text available
Stress evolution of restrained concrete is a significant direct index in early-age cracking (EAC) analysis of concrete. This study presents experiments and numerical modelling of the early-age stress evolution of Ground granulated blast furnace slag (GGBFS) concrete, considering the development of autogenous deformation and creep. Temperature Stres...
Article
Full-text available
This study aims to provide an efficient alternative for predicting creep modulus of cement paste based on Deep Convolutional Neural Network (DCNN). First, a microscale lattice model for short-term creep is adopted to build a database that contains 18,920 samples. Then, 3 DCNNs with different consecutive convolutional layers are built to learn from...
Article
Full-text available
This study aims to provide an efficient and accurate machine learning (ML) approach for predicting the creep behavior of concrete. Three EML models are selected in this study: Random Forest (RF), Extreme Gradient Boosting Machine (XGBoost) and Light Gradient Boosting Machine (LGBM). Firstly, the creep data in Northwestern University (NU) database i...
Article
Full-text available
In this work, the lattice model is applied to study the printing process and quantify the buildability (i.e., the maximum height that can be printed) for 3D concrete printing (3DCP). The model simulates structural failure by incorporating an element birth technique, time‐dependent stiffness and strength, printing velocity, non‐uniform gravitational...
Article
Full-text available
A combination of laboratory experiments and numerical simulations at multiple length scales can provide in-depth understanding of fracture behaviour of hydrated cement paste (HCP). To that end, the current work presents a numerical study on compressive failure of hydrated cement paste (HCP) at the micro-scale. Virtual specimens consisting of variou...
Article
Full-text available
Application of micromechanical modelling of hydrated cement paste (HCP) gains more and more interests in the field of cementitious materials. One of the most promising approaches is the use of so-called microstructure informed micromechanical models, which provides a direct link between microstructure and mechanical properties. In order to properly...
Article
Full-text available
The lattice fracture model is a discrete model that can simulate the fracture process of cementitious materials. In this work, the Delft lattice fracture model is reviewed and utilized for fracture analysis. First, a systematic calibration procedure that relies on the combination of two uniaxial tensile tests is proposed to determine the input para...
Chapter
This paper reports an extended lattice model for printing process simulation of 3D printed cementitious materials. In this model, several influencing factors such as material and geometric nonlinearity are considered. Using this model, green strength of cementitious material is investigated, deformation and crack pattern can be derived, which is cl...
Article
Full-text available
In 3D concrete printing (3DCP), it is necessary to meet contradicting rheological requirements: high fluidity during pumping and extrusion, and high stability and viscosity at rest to build the layered structure. In this paper, the impact of the hydroxypropyl methylcellulose (HPMC)-based viscosity-modifying admixture (VMA) on the 3D printability an...
Article
Full-text available
The aim of this work is to investigate the mechanical performance of hardened cement paste 8 (HCP) under compression at the micrometre length scale. In order to achieve this, both experimental 9 and numerical approaches were applied. In the experimental part, micrometre sized HCP specimens 10 were fabricated and subjected to uniaxial compression by...
Conference Paper
Full-text available
The aim of this work is to investigate the fracture process of concrete under various boundary conditions. Although numerous concrete fracture tests have been reported, showing the failure behavior of concrete, their evaluation is ambiguous due to the limitations of specimen size and experimental conditions. Therefore, it is necessary to use sim...

Questions

Question (1)
Question
For 3D beam elements, when considering the geometry nonlinearity, the final equation becomes (Ke+Kg)*deltaU=deltaF, Kg the geometric stiffness matrix is a function of total axial force acting on the element in the reference configuration. The character of symmetric positive-definite for this matrix always changes with the element force?

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Projects

Project (1)
Project
optimize the printing process