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CONTENTS
Volume 48, Number 5, September10 2023
 


Abstract
The need for carbon neutrality in the world strives the construction industry to reduce the use of construction materials. Aiming to this, recycled aggregate concrete (RAC) could be used as it reduces the carbon dioxide emissions. Currently, RAC is mainly used in non-structural members of civil constructions, seldom used in structural members. To broaden its structural use, a new type of composite column, i.e., the square and rectangular RAC filled FRP tubes (CFFTs), has been concerned in this study. The investigation on their axial compressive behavior through physical test and numerical analysis demonstrated that the load-carrying capacity of such column is reduced with the increase of replacement ratio of recycled aggregate and aspect ratio of section but can be improved by the increase of FRP confining stiffness and corner radius, said capacity can be equivalent to their steel reinforced concrete counterparts. At failure, the hoop strain at corner of tube is unexpectedly smaller than that at flat side of the tube although the FRP tube ruptured at its corner first, revealing a premature failure. Besides, a design-oriented stress-strain model of concrete and an analysis-oriented finite element model are proposed to predict the load-strain response of square and rectangular CFFT columns, which facilitates the engineering use of RAC in loadcarrying structural members.

Key Words
compression; design model; finite element model; FRP; recycled aggregate concrete; square and rectangular

Address
Ming-Xiang Xiong:Earthquake Engineering Research & Test Center, Guangzhou University, Guangzhou 510405, China

Xuchi Chen:Guangzhou Second Municipal Engineering Co., Ltd., Guangzhou 510060, China

Fengming Ren:School of Civil Engineering, Guangzhou University, Guangzhou 510006, China

Abstract
Geological hazards in landslide is one of the most extensive and destructive phenomena are among natural disasters. According to the topography high mountains, tectonic activity, high seismicity, diverse conditions Geology and climate, basically China to create a wide spectrum of landslides have natural conditions and these landslides are annual. They cause a lot of financial losses to the country. It is very difficult to predict the time of the landslide, hence the identification landslide sensitive areas and zoning of these areas based on the potential risk is very important. Therefore, it should be susceptible areas landslides should be identified in order to reduce damages caused by landslides find. the main purpose of landslide sensitivity analysis is identification high-risk areas and as a result, reducing damages caused by landslides It is the way of appropriate actions.

Key Words
fuzzy logic methods; geological hazards; hierarchical analysis; landslides

Address
Shasha Yang:School of Petroleum Engineering and Environmental Engineering, Yan

Abstract
The number of studies investigating the response of concrete-filled tubes (CFTs) under shear has been very limited in the literature. This lack of research has been traditionally reflected in international design standards as rather conservative shear strength predictions for CFTs. The dearth of research on the shear response is even more pronounced for the case of concrete-filled stainless steel tubes (CFSSTs). In line with this, the present study investigates the shear response of circular and square CFSSTs using advanced finite element (FE) analysis. A thorough review of the previous studies on the shear response of carbon steel CFTs is provided along with a summary of past experimental programmes as well as the developed and codified design methods. A comprehensive numerical study is then conducted considering a wide range of circular and square, austenitic and lean duplex CFSSTs with different concrete infills and shear span-to-depth ratios. The effect of the tail length on the shear response is investigated and the minimum required tail length for achieving full shear capacity is established. The simulations are also used to highlight the importance of the dilation of the concrete core in the shear response of concrete-filled tubes and its relationship with the utilised boundary conditions. Furthermore, the numerical results are compared in detail with the predictions of design approaches developed previously for carbon steel CFTs and their accuracy and applicability to the stainless steel counterpart are demonstrated and recommendations are made accordingly.

Key Words
CFSST; concrete-filled; design; finite element analysis; shear; stainless steel

Address
Sina Kazemzadeh Azad and Brian Uy:School of Civil Engineering, The University of Sydney, NSW 2006, Australia

Abstract
Composite dowels are implemented as a powerful alternative to headed studs for the efficient combination of Ultra High-Performance Concrete (UHPC) with high-strength steel in novel composite structures. They are required to provide sufficient shear resistance and ensure the transmission of tensile forces in the composite connection in order to prevent lifting of the concrete slab. In this paper, the load bearing capacity of puzzle-shaped and clothoidal-shaped dowels encased in UHPC specimen were investigated based on validated experimental test data. Considering the influence of the embedment depth and the spacing width of shear dowels, the characteristics of UHPC square plate on the load bearing capacity of composite structure, 240 numeric models have been constructed and analyzed. Three artificial intelligence approaches have been implemented to learn the discipline from collected experimental data and then make prediction, which includes Artificial Neural NetworkParticle Swarm Optimization (ANN-PSO), Adaptive Neuro-Fuzzy Inference System (ANFIS) and an Extreme Learning Machine (ELM). Among the factors, the embedment depth of composite dowel is proved to be the most influential parameter on the load bearing capacity. Furthermore, the results of the prediction models reveal that ELM is capable to achieve more accurate prediction.

Key Words
adaptive neuro-fuzzy inference system; artificial neural network; composite dowels; extreme learning machine; pull-out test; UHPC

Address
Zhihua Xiong:1)College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi, China
2)nstitute of Steel Construction, RWTH Aachen University, Aachen, Germany

Zhuoxi Liang, Xuyao Liu and Jiawen Li:College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi, China

Markus Feldmann:College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi, China

Abstract
This study investigates the effect of bolt preloading on the rotational stiffness of stainless steel end-plate connections. An experimental programme incorporating 11 full-scale joint specimens are carried out comparing the behaviours of fully pre-tensioned (PT) and snug-tightened (ST) flush/extended end-plate connections, made of austenitic or lean duplex stainless steels. It is observed from the tests that the presence of bolt preloading leads to a significant increase in the rotational stiffness. A parallel finite element analysis (FEA) validated against the test results demonstrates that the geometric imperfection of end-plate has a strong influence on the moment-rotation response of preloaded end-plate connections, which is crucial to explain the observed "two-stage" behaviour of these connections. Based on the data obtained from the tests and FE parametric study, the performance of the Eurocode 3 predictive model is evaluated, which exhibits a significant deviation in predicting the rotational stiffness of stainless steel end-plate connections. A modified bi-linear model, which incorporates three key properties, is therefore proposed to enable a better prediction. Finally, the effect of bolt preloading is demonstrated at the system (structure) level considering the serviceability of semi-continuous stainless steel beams with end-plate connections

Key Words
bolt preloading; end-plate connection; moment-rotation response; rotational stiffness stainless steel

Address
Yuchen Song:School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia

Brian Uy:Department of Building and Real Estate, The Hong Kong Polytechnic University, Hong Kong, China


Abstract
The present research reports the application of engineered cementitious composites (ECC) as an alternative to conventional concrete to improve the seismic behavior of short columns. Experimental and finite element investigation was conducted by testing five reinforced engineered cementitious composite (RECC) concrete columns (half-scale specimens) and one control reinforced concrete (RC) specimen for different shear-span and transverse reinforcement ratios under cyclic lateral loads. RECC specimens with higher shear-span and transverse reinforcement ratios demonstrated a significant effect on the column lateral load behavior by improving ductility (〉5), energy dissipation capacity (1.2 to 4.1 times RC specimen), gradual strength degradation (ultimate drift 〉3.4%), and altering the failure mode. The self-confinement effect of ECC fibers maintained the integrity in the post-peak region and reserved the transmission of stress through fibers without noticeable degradation in strength. Finite element modeling of RECC specimens under monotonic incremental loads was carried out by adopting simplified constitutive material models. It was apprehended that the model simulated the global response (strength and stiffness) and damage crack patterns reasonably well.

Key Words
Engineered cementitious composites (ECC); finite element model; seismic behavior; short columns

Address
Syed Humayun Basha, Xiaoqin Lian, Wei Hou, Pandeng Zheng and ZiXiong Guo:College of Civil Engineering, Huaqiao University, Xiamen 361021, China

Abstract
This paper introduces a novel approach to multi-material topology optimization (MTO) targeting in-plane bidirectional functionally graded (IBFG) non-uniform thickness Reissner-Mindlin plates, employing an alternative active phase approach. The mathematical formulation integrates a first shear deformation theory (FSDT) to address compliance minimization as the objective function. Through an alternating active-phase algorithm in conjunction with the block Gauss-Seidel method, the study transforms a multi-phase topology optimization challenge with multi-volume fraction constraints into multiple binary phase sub-problems, each with a single volume fraction constraint. The investigation focuses on IBFG materials that incorporate adequate local bulk and shear moduli to enhance the precision of material interactions. Furthermore, the well-established mixed interpolation of tensorial components 4-node elements (MITC4) is harnessed to tackle shear-locking issues inherent in thin plate models. The study meticulously presents detailed mathematical formulations for IBFG plates in the MTO framework, underscored by numerous numerical examples demonstrating the method's efficiency and reliability.

Key Words
FSDT; in-plane bi-dimensional functionally graded material; multi-material; shear locking phenomenon; topology optimization; variable thickness

Address
Nam G. Luu:Faculty of Information Technology, Industrial University of Ho Chi Minh city 70000, Vietnam

Thanh T. Banh and Dongkyu Lee:Department of Architectural Engineering, Sejong University, Seoul 05006, Republic of Korea

Abstract
To avoid debonding failure, a novel type of hybrid anchorage (HA) is proposed in this study that uses a slotted plate to lock the ends of the fiber-reinforced polymer (FRP) sheet in addition to the usual bonding over the substrate of the strengthened member. An experimental investigation was performed on three groups of RC beams, which differed from one another in either concrete strength or steel reinforcement ratio. The test results indicate that the end self-locking of the CFRP sheet can improve the failure ductility, ultimate capacity of the beams and its utilization ratio. Although intermediate debonding occurred in all the strengthened beams, it was not a fatal mode of failure for the three specimens with end anchorage. Among them, FRP rupture occurred in the beam with higher concrete strength and lower steel reinforcement ratio, whereas the other two failed by concrete crushing. The beam strengthened by HA obtained a relatively high percentage of increase in ultimate capacity when the rebar ratio or concrete strength decreased. The expressions in the literature were inspected to calculate the critical loads at intermediate debonding, FRP rupturing and concrete crushing after debonding for the strengthened beam. Then, the necessity of further research is addressed.

Key Words
concrete beams; debonding; fiber reinforced polymer; hybrid anchorage; self-locking

Address
Chaoyang Zhou,Xuejun He and Yi Wang:1)National Engineering Research Center of High-speed Railway Construction Technology, Central South University, Changsha 410075, China
2)School of Civil Engineering, Central South University, Changsha, Hunan 410075, China

Yanan Yu and Chengfeng Zhou:National Engineering Research Center of High-speed Railway Construction Technology, Central South University, Changsha 410075, China



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