Abstract
Currently, the electro-hydraulic servo loading control system manufactured by MTS, OpenFresco hybrid test interface software and OpenSees finite element software are widely used in structure laboratories to carry out hybrid test, but there is no relevant public information about full structure pseudo-dynamic test based on the above software and hardware. In order to study the feasibility of using the above software and hardware to carry out full structure pseudo-dynamic test, the full structure pseudo-dynamic virtual experiments of a single degree of freedom (SDOF) structure and a two degrees of freedom (2DOFs) structure are carried out based on the MTS 793 Demo Mode, and the results are respectively compared with the finite element analysis method. The results show that the finite element analysis results and full structure pseudo-dynamic virtual experiment results are highly consistent, which verifies the feasibility of carrying out the full structure pseudo-dynamic test based on the above software and hardware. Then, a three story steel frame full structure pseudo-dynamic test is conducted, and the smooth implementation of full structure pseudo-dynamic test of the three story steel frame further verifies the reliability of this testing method. The implementation method of carrying out the full structure pseudo-dynamic tests are introduced in detail, which can provide some reference for relevant research.
Key Words
full structure pseudo-dynamic test; MTS 793; OpenFresco; OpenSees; three story steel frame
Address
Zhen Tian, Yuan Cheng, Xuechong Ren and Mengmeng Yang: National center for materials service safety, University of science and technology Beijing, China
University of science and technology Beijing innovation arena, Shahe Town,
Changping District, Beijing, China
Abstract
For the problems of high compressibility and low strength of peat soil formed by lake-phase deposition
in Dianchi Lake, microbial-induced calcium carbonate deposition (MICP), phyto-urease-induced calcium carbonate
deposition (EICP) and phyto-urease-induced calcium carbonate deposition combined with lignin (EICP combined
with lignin) were used to reinforce the peat soil, the changes in mechanical properties of the soil before and after the
reinforcement of the peat soil were experimentally investigated, and the effect and mechanism of peat soil reinforcing
by the three reinforcing techniques were tested and analyzed using X-ray diffraction (XRD) and scanning electron
microscope (SEM). The results show that: compared to the unreinforced remolded peat soil specimens, the
unconfined compressive strength (UCS), cohesion and internal friction angle of the specimens reinforced by MICP,
EICP and EICP combined with lignin techniques have been greatly improved, and the permeability resistance has
been improved by two, two and three orders of magnitude, respectively; the different methods of reinforcing generate
different calcium carbonate crystalline phases, with the EICP combined with lignin technique generating the most
stable calcite, and the MICP and EICP techniques generating a mixed phase of calcite and spherulitic chalcocite.
Analyses showed that for peat soil reinforcement, the acidic environment of peat soil inhibited the growth and
reproduction of bacteria, EICP technology was superior to MICP technology, and the addition of lignin solved the defect of the EICP technology that did not have a "nucleation sit", so EICP combined with lignin reinforcement was preferred for the improvement of peat soil.
Key Words
EICP; EICP combined lignin; MICP; reinforcement mechanism; the peat soil
Address
Chao Wang, Jianbin Xie, Yinlei Sun, Jianjun Li and Jie Li: School of Architecture and Planning, Yunnan University, Kunming 650500, P.R. China
Ronggu Jia: Construction and Investment Holding Group No.1 Engineering Survey and Design Co., Ltd.,
Kunming 650500, P.R. China
Abstract
Electro-mechanical impedance (EMI) technique is a low-cost structural damage detection method. It reflects structural damage through the change in admittance signal which contains the structural mechanical impedance information. The ambient temperature greatly affects the admittance signal, which hides the changes caused by structural damage and reduces the accuracy of damage identification. This study introduces a convolutional neural network to compensate for the temperature effect. The proposed method uses a framework that consists of a feature extraction network and a decoding network, and the original admittance signal with temperature information is used as the input. The output admittance signal is eliminated from the temperature effect, improving damage identification robustness. The admittance data simulated by the finite element model of the spatial grid structure is used to verify the effectiveness of the proposed method. The results show that the proposed method has advantages in identification accuracy compared with the damage index minimization method and the principal component analysis method.
Key Words
convolutional neural network; electro-mechanical impedance; spatial grid structure structural damage identification; temperature compensation
Address
Yujun Ye, Yikai Zhu and Huaping Wan: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
Bo Lei and Hongchang Xu: China Construction Third Engineering Bureau Co., Ltd., Wuhan 430064, China
Zhihai Weng: Huzhou City Investment and Development Group Co., Ltd., Huzhou 313000, China
Abstract
The strength reduction factor spectrum is traditionally obtained from a single-degree-of-freedom (SDOF) system with a constant damping coefficient. However, according to the principle of Rayleigh damping, the damping coefficient matrix of a system changes with the stiffness matrix, and the damping coefficient of an equivalent SDOF system changes with the tangent stiffness coefficient. In view of that, this study proposes an equivalent SDOF system with an adaptive damping coefficient and derives a standardized reaction balance equation. By iteratively adjusting the strength reduction factor, the corresponding spectrum with an equivalent ductility factor is obtained. In addition, the ratio between the strength reduction factor that considers adaptive damping and the traditional strength reduction factor, denoted by n, is determined, and the n-u-T relationship is obtained. Seismic records of Classes C, D, and E sites are selected as excitations. Moreover, a nonlinear response time-history analysis is performed to establish the relationship between the n and T values for the equivalent ductility factor u. Further, by exploring the effects of the site class, ductility factor, second-order stiffness coefficient, and period T on the mean value of n, a simplified calculation equation of mean n is derived, and n is used as a modified value for the traditional strength reduction factor R spectrum.
Abstract
Structural seismic tests usually need to simulate the gravity load borne by the structure, the gravity load application devices should keep the force value and direction unchanged, and can adapt to the structural deformation. At present, there are two main ways to simulate gravity load in laboratory: roller group and prestress. However, there are few differential analysis between these two ways in the existing experimental studies. In this paper, the simulation software ABAQUS is used to simulate the static pushover analysis of reinforced concrete column and frame, which are the most common models in structural seismic tests. The results show that the horizontal restoring force of the model using prestressed loading method is significantly greater than roller group, and the difference between the two will increase with the increase of the horizontal deformation. The reason for the difference is that the prestressed loading method does not take the adverse effects of gravity second-order effect (P-Delta effect) into account. Therefore, the restoring force obtained under prestressed loading method should be corrected and the additional shear force caused by P-Delta effect should be deducted. After correction, the difference of restoring force between the two gravity load application methods is significantly reduced (when storey-drift is 1/550, the relative error is within 1%; and when storey-drift is 1/50, the relative error is about 3%). The research results of this research can provide reference for the selection and data processing of gravity load simulation devices in structural seismic tests.
Address
Yonglan Xie, Songtao Yan, Yurong Wang and Shuwei Song: National center for materials service safety, University of science and technology Beijing, China
University of science and technology Beijing innovation arena,
Shahe Town, Changping District, Beijing, China
Abstract
Domestic sewage can greatly affect the macro-micro physical-mechanical properties of building
foundation soils. In order to investigate the effect of domestic sewage on physical and mechanical properties of soils,
the physicochemical properties of three groups of different concentrations of domestic sewage contaminated soil
were tested through indoor experiments. Combined with scanning electron microscopy, X-ray diffraction
experiments, and grey relational analysis, the degree of influence of different concentrations of domestic sewage on
the physicochemical properties of soil was compared and analyzed from multiple perspectives such as microstructure
and mineral composition, revealing the influencing mechanism of soil pollution by domestic sewage. The results
showed that under the immersion of contaminated water, the color of the soaking water turned black first and then
yellow, and brownish yellow secretions appeared on the surface of the soil samples. The moisture content, specific
gravity, density, and pore ratio index of the soil samples immersed in 50% and 100% domestic sewage decreased
with the increase of sewage concentration, while the liquid limit of the soil samples changed in the opposite direction.
The immersion time had little effect on the slope of the compression curve of the soil samples soaked in tap water.
For the soil samples immersed in domestic sewage, the slope of the compression curve and the compression
coefficient increased with the increase of domestic sewage concentration and immersion time, while the compression
modulus showed the opposite trend. In the soil samples immersed in tap water, there were a large number of small
particles and cementitious substances, and the structure was relatively dense. With the increase of domestic sewage
concentration, the microstructure of the soil changed significantly, with the appearance of sigle particle structure,
loose and disorderly arrangement of particles, increased and enlarged pores, gradual reduction of small particle
substances and cementitious substances, and the soil structure transformed from compact to loose. The research
findings can provide theoretical reference for contaminated geotechnical engineering.
Key Words
domestic sewage pollution soil; microstructure; mineral composition; hysical and mechanical
properties
Address
Zhi-Fei Li, Yu-Ao Li, Yi Li, Shu-Chang Zhang and Yin-Lei Sun:
School of Architecture and Planning, Yunnan University, Kunming 650500, China
Wei Liu: Jiangxi Province Survey and Design Research Institute Co., Jiangxi, Nanchang 330095, China
