Xi Zhao

Beijing University of Civil Engineering and Architecture · Civil Engineering

This paper insightfully studies geometric imperfection simulations of cee-section CFS members from laser-based measurements. A machine-vision imperfection inspection technique is first developed where an algorithm is implemented to automate imperfection characterization from volumetric data. The measured imperfections are statistically analyzed and...

Cold-formed steel (CFS) structures are widely used in construction and infrastructure due to their lightweight and high-strength properties. However, their thin-walled nature makes them geometrically sensitive to compressive loading. The Digital Twin (DT)-based numerical simulation method is developed using the actual geometries of CFS shapes, whic...

This research focuses on modeling of as-true geometric uncertainty of cold-formed steel (CFS) members with a multidimensional Gaussian process, the coefficients of which are trained by a maximum-likelihood machine-learning method. The stochasticity and correlations of geometric features, including geometric imperfections, are embedded in the model....

Exploratory search is a search paradigm that plays a vital role in databases, data mining, and information retrieval to assist users to get familiar with the underlying databases. It supports iterative query formulation to explore the data space. Despite its growing importance, exploratory search on graph-structured data has not received adequate a...

Among many solutions to the high-dimensional approximate nearest neighbor (ANN) search problem, locality sensitive hashing (LSH) is known for its sub-linear query time and robust theoretical guarantee on query accuracy. Traditional LSH methods can generate a small number of candidates quickly from hash tables but suffer from large index sizes and h...

Cable domes achieve structural stiffness and loading capacity through tension cables and compression struts. Friction from cable-strut joints contributes a major prestress loss during tensioning. This paper presents a novel hemispheric rolling cable-strut joint which provides smooth load transmission and high prestress efficiency. It comprises a he...

Indexing is an effective way to support efficient query processing in large databases. Recently the concept of learned index has been explored actively to replace or supplement traditional index structures with machine learning models to reduce storage and search costs. However, accurate and efficient similarity query processing in high-dimensional...

Indexing is an effective way to support efficient query processing in large databases. Recently the concept of learned index , which replaces or complements traditional index structures with machine learning models, has been actively explored to reduce storage and search costs. However, accurate and efficient similarity query processing in high-d...

The pseudo-static tests were conducted for a box-shaped column connection achieved by plug welding-core sleeve (SHJD), for a box-shaped column connection achieved by self-lock one-side bolt-core sleeve (DLJD), and for a traditional fully-penetrated welded connection (HJJD), to comparatively analyze the difference of mechanical behaviors on test phe...

A general formula of Jacobian matrix is derived in an incremental harmonic balance (IHB) method for general nonlinear delay differential equations (DDEs) with multiple discrete delays, where the fast Fourier transform is used to calculate Fourier coefficients of partial derivatives of residuals. It can be efficiently and automatically implemented i...

This paper reports on experiments addressing the buckling and collapse behavior of back-to-back lipped channel built-up cold-formed steel (CFS) columns assembled using 16 different CFS lipped channel sizes. The lipped channel sections are connected at the web using a pair of self-drilling screw fasteners at a specified spacing along the column leng...

This paper reports on experiments addressing the buckling and collapse behavior of common built-up cold-formed steel (CFS) columns. The built-up column consists of two individual CFS lipped channels placed back-to-back and connected at the web using two self-drilling screw fasteners at specified spacing along the column length. The experiments aim...

The objective of this paper is to present procedures for processing three-dimensional point clouds that are generated from laser-based scanning of a cold-formed steel member into useful measurements of cross-section dimensions and imperfections, as well as for use in finite element simulations of the as-measured geometry. The measurement data comes...

Thin-walled cold-formed steel members are advantageous due to their low weight and high strength, but both strength and overall response sensitivity to geometric imperfections must be considered. It is important to accurately estimate geometric imperfections for meaningful simulation of cold-formed steel members. This paper presents recently perfor...

Geometric imperfections play an important role in the performance and behavior of cold-formed steel members. The objective of this paper is to present recent results from measurements of cold-formed steel members conducted by a laser scanner. The measurements provide complete and precise three-dimensional point clouds of the specimens and can be pr...

Geometric imperfections play an important role in the strength and behavior of thinwalled metal parts such as those commonly used in cold-formed steel construction. The objective of this paper is to detail a newly developed imperfection measurement platform, where the full-three dimensional (3D) imperfect geometry of a cold-formed steel member can...

Post-buckling behavior of thin-walled, cold-formed steel members is complicated. The discrepancy between the experimentally measured load-deformation curves and computational simulations stems from a fundamental lack of knowledge about the initial stage of these members, in particular geometric imperfections. Attempts to push numerical simulations...

Local flange and web imperfections, cross-sectional twist, and global sweep were measured for cold-formed steel C-section structural members (studs and joists) using non-contact measurement methods (photogrammetry and laser scanning) and a manual measurement method (dial gauges mounted on a precision rail). Cold-formed steel members acquire geometr...

Geometric imperfections play an important role in the performance and behavior of cold-formed steel members. The objective of this paper is to detail a newly developed imperfection measurement rig, where the full three-dimensional (3D) imperfect geometry of a cold-formed steel member can be measured and reconstructed. The measurement results in a d...