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Volume 49, Number 2, October 25 2023

Firstly, a new kind of prismatic tensegrity structures with redundant cables is defined, the topology, geometry and forming conditions of which are introduced further. The development of its mechanical properties including self-stress states and structural stiffness with the increment of the twist angle is also investigated carefully. Combined with the topology of this kind of structures, a reasonable erection scheme is proposed, in which some temporary lifting points need to be set and two groups of vertical cables are tensioned in batches. Then, a simplified dynamic relaxation method is employed to track the erection process inversely, which aims to predict each intermediate equilibrium state during the construction, and give the key structural parameters that can effectively guide the construction. The removal of the active cables, the relaxation or tension of the passive cables are simulated by controlling their axial stiffness, so that the structural composition as well as the serial numbers of the elements always keep invariant regardless of the withdrawal of the slack cables. The whole analysis process is clear in concept, simple to implement and easy to popularize. Finally, several examples are given to verify the practicability and effectiveness of the proposed method further.

Key Words
dynamic relaxation method; erection process; inverse analysis; redundant cables; tensegrity structures; twist angle

Pei Zhang and Jingjing Yang:College of Civil and Transportation Engineering, Hohai University, Nanjing 210098, China

Huiting Xiong:School of Civil Engineering, Wanjiang University of Technology, Ma'anshan 243031, China

Jiayan Liu:Key Laboratory of Concrete and Pre-stressed Concrete Structures of Ministry of Education, Southeast University, Nanjing 211189, China

Recently, the design of scaffolding systems has garnered considerable attention due to the increasing number of scaffold collapses. These incidents arise from the underestimation of imposed loads and the site-specific conditions that restrict the application of lateral restraints in scaffold assemblies. The present study is committed to augmenting the buckling resistance of vertical support members, obviating the need for supplementary lateral restraints. To achieve this objective, experimental and computational analyses were performed to assess the axial load buckling capacity of steel props, composed of two hollow steel pipes that slide into each other for a certain length. Three full-scale steel props with various geometric properties were tested to construct and validate the analytical models. The total unsupported length of the steel props is 6 m, while three pins were installed to tighten the outer and inner pipes in the distance they overlapped. Finite Element (FE) modeling is carried out for the three steel props, and the developed models were verified using the experimental results. Also, theoretical analysis is utilized to verify the FE analysis. Using the FE-verified models, a parametric study is conducted to evaluate the effect of different inserted pipe lengths on the steel props' axial load capacity and lateral displacement. Based on the results, the typical failure mode for the studied steel props is global elastic buckling. Also, the prop's elastic buckling strength is sensitive to the inserted length of the smaller pipe. A threshold of minimum inserted length is one-third of the total length, after which the buckling strength increases. The present study offers a prop with enhanced buckling resistance and introduces an equation for calculating an equivalent effective length factor (k), which can be seamlessly incorporated into Euler's buckling equation, thereby facilitating the determination of the buckling capacity of the enhanced props and providing a pragmatic engineering solution.

Key Words
elastic flexural buckling; finite element modeling; load-carrying capacity; scaffold shoring systems; structural steel pipe

Zaid A. Al-Sadoon, Samer Barakat and Aroob Al Ateyat:Civil and Environmental Engineering Department, University of Sharjah, Sharjah, United Arab Emirates

Farid Abed:Department of Civil Engineering, American University of Sharjah, Sharjah, United Arab Emirates

In the previous research, the axial compressive capacity models for the glass fiber-reinforced polymer (GFRP)- reinforced circular concrete compression elements restrained with GFRP helix were put forward based on small and noisy datasets by considering a limited number of parameters portraying less accuracy. Consequently, it is important to recommend an accurate model based on a refined and large testing dataset that considers various parameters of such components. The core objective and novelty of the current research is to suggest a deep learning model for the axial compressive capacity of GFRPreinforced circular concrete columns restrained with a GFRP helix utilizing various parameters of a large experimental dataset to give the maximum precision of the estimates. To achieve this aim, a test dataset of 61 GFRP-reinforced circular concrete columns restrained with a GFRP helix has been created from prior studies. An assessment of 15 diverse theoretical models is carried out utilizing different statistical coefficients over the created dataset. A novel model utilizing the group method of data handling (GMDH) has been put forward. The recommended model depicted good effectiveness over the created dataset by assuming the axial involvement of GFRP main bars and the confining effectiveness of transverse GFRP helix and depicted the maximum precision with MAE = 195.67, RMSE = 255.41, and R2 = 0.94 as associated with the previously recommended equations. The GMDH model also depicted good effectiveness for the normal distribution of estimates with only a 2.5% discrepancy from unity. The recommended model can accurately calculate the axial compressive capacity of FRP-reinforced concrete compression elements that can be considered for further analysis and design of such components in the field of structural engineering.

Key Words
axial strain; axial strength; CFRP; composite; restrained concrete; soft computing

Mohammed Berradia:Department of Civil Engineering, Laboratory of Structures, Geotechnics and Risks (LSGR), Hassiba Benbouali University of Chlef, B.P 78C,
Ouled Fares Chlef 02180, Algeria

El Hadj Meziane:Department of Civil Engineering, Geomaterials Laboratory (LaG), Hassiba Benbouali University of Chlef,
B.P 78C, Ouled Fares Chlef 02180, Algeria

Ali Raza and Faisal Shabbir:Department of Civil Engineering, University of Engineering and Technology Taxila, 47050, Pakistan

Mohamed Hechmi El Ouni:Department of Civil Engineering, College of Engineering, King Khalid University, PO Box 394, Abha 61411, KSA

Marine structures including offshore wind turbines (OWTs) always work under cyclic loads, which arouses much attention on the fatigue design. The tripod substructure is one of the typical foundation forms for fixed OWTs. The three-planar tubular Y-joint (3Y joint) is one of the important components in fatigue design as it is most likely to have cracks. With the existence of the multiplanar interaction effect, calculating the hot spot stress (HSS) of 3Y joints is complicated. To assist with fatigue design, the distributions of stress concentration factor (SCF) and multiplanar interaction factor (MIF) along weld toe curves induced by the out-of-plane bending moment are explored in this study. An FE analysis method was first developed and verified against experimental results. This method was applied to build a numerical database including 1920 FE models covering common ranges of geometric parameters. A parametric study has been carried out to reveal the distribution patterns of SCF and MIF. After multidimensional nonlinear fittings, SCF and MIF distribution formulas have been proposed. Accuracy and reliability checking prove that the proposed formulas are suitable for calculating the HSS of 3Y joints.

Key Words
distribution formula; fatigue design; hot spot stress; offshore wind turbine; out-of-plane bending moment

Shiliu Bao and Jikai Zhou:College of Civil and Transportation Engineering, Hohai University, No.1 Xikang Road, Nanjing, China

Wenhua Wang and Xin Li:Faculty of Infrastructure Engineering, Dalian University of Technology, No.2 Linggong Road, Dalian, China

To investigate the static properties of large high strength bolt shear connector in hybrid fiber-reinforced concrete (HFRC) and normal concrete (NC), eight push-out test specimens with single/double nut and HFRC/NC slabs were designed and push-out tests were conducted. A fine 3D nonlinear finite element (FE) model including HFRC constitutive model was established by using ANSYS 18.0, and the test results were used to verify FE models of the push-out test specimens. Then a total of 13 FE models were analyzed with various parameters including fiber volume fractions of HFRC, bolt diameter and thickness of steel flange. Finally, the empirical equations considering the contribution of polypropylene fiber (PF) and steel fiber (SF) obtained from the regression of the test results and FE analysis were recommended to evaluate the load-slip curve and ultimate capacity of the large high strength bolt shear connector embedded in HFRC/NC.

Key Words
FE analysis; HFRC; large high strength bolt; mechanical behavior; push-out test

Yuliang He, Zhengxin Wang and Ying Yang:College of Civil Engineering, Shaoxing University, 508 West Huangcheng Rd., Shaoxing, China

Weiming Wu:Huahui Group, 177 Jiefang Avenue Shaoxing, China

Yiqiang Xiang:College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Rd., Hangzhou, China

Cable-girder anchorage joint is the critical part of cable-supported bridges. Tensile-plate anchorage (TPA) is one of the most commonly used types of cable-girder anchorage joints in steel girder cable-supported bridges. In recent years, it has been proposed by bridge designers to apply TPA to concrete girder cable-supported bridges to form composite cable-girder anchorage joint (CCGAJ). In this paper, the mechanical performance of CCGAJ under tensile force is studied through experimental and numerical analyses. Firstly, the effects of the external prestressing (EP) and the bearing plate (BP) on the mechanical performance of CCGAJ were investigated through three tests. Then, finite element model was established for parametrical study, and was verified by the experimental results. Then, the effects of shear connector forms, EP, BP, vertical rebar rate, and perforated rebar rate on the tensile capacity of CCGAJ were investigated through numerical analyses. The results show that the tensile capacity of CCGAJ depends on the first row of PR. The failure mode of CCGAJ using headed stud connectors is to form a shear failure surface at the end of the studs while the failure mode using PBLs is similar to the bending of a deep girder. Finally, based on the strut-and-tie model (STM), a calculation method for CCGAJ tensile capacity was proposed, which has a high accuracy and can be used to calculate the tensile capacity of CCGAJ.

Key Words
bearing plate; cable-girder anchorage; external prestressing; mechanical performance; strut-and-tie model; tensile-plate anchorage; tensile capacity

Xue Fei Shi, Yu-Zhuo Zhong and Haiying Ma:Department of Bridge Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China

Ke Hu:Anhui Transportation Holding Group Co., LTD, Hefei, 230088, China

Zhiquan Liu:Shanghai Briding Engineering Consulting Co., LTD, Shanghai, 200433, China

Cheng Zeng:Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355, Germany

Many of the recent investigations in the field of geotechnical engineering focused on the bearing capacity theories of multilayered soil. A number of factors affect the bearing capacity of the soil, such as soil properties, applied overburden stress, soil layer thickness beneath the footing, and type of design analysis. An extensive number of finite element model (FEM) simulation was performed on a prototype slope with various abovementioned terms. Furthermore, several non-linear artificial intelligence (AI) models are developed, and the best possible neural network system is presented. The data set is from 3443 measured full-scale finite element modeling (FEM) results of a circular shallow footing analysis placed on layered cohesionless soil. The result is used for both training (75% selected randomly) and testing (25% selected randomly) the models. The results from the predicted models are evaluated and compared using different statistical indices (R2 and RMSE) and the most accurate model BBO (R2=0.9481, RMSE=4.71878 for training and R2=0.94355, RMSE=5.1338 for testing) and TLBO (R2=0.948, RMSE=4.70822 for training and R2=0.94341, RMSE=5.13991 for testing) are presented as a simple, applicable formula.

Key Words
artificial neural network; bearing capacity; circular footing; sand

Wenjun DAI:Shenzhen Urban Transport Planning Center Co., Ltd, Shenzhen 518000, China

Marieh Fatahizadeh: Department of Water Engineering, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran

Hamed Gholizadeh Touchaei:Department of Civil Engineering, Southern Illinois University Edwardsville, Edwardsville, IL 62026, U.S.A.

Hossein Moayedi and Loke Kok Foong:1)Institute of Research and Development, Duy Tan University, Da Nang, Vietnam
2)School of Engineering & Technology, Duy Tan University, Da Nang, Vietnam

The present paper summarizes the results of an experimental program on the influence of using waste lathe scraps in the concrete mixture on the shear behavior of RC beams with different amounts of shear reinforcement. Three different volumetric ratios (1, 2 and %3) for the scraps and three different stirrup spacings (160, 200 and 270 mm) were adopted in the tests. The shear span-to-depth ratios of the beams were 2.67 and the stirrup spacing exceeded the maximum spacing limit in the building codes to unfold the contribution of lathe scraps to the shear resistances of shear-deficient beams, subject to sheardominated failure (shear-tension). The experiments depicted that the lathe scraps have a pronounced contribution to the shear strength and load-deflection behavior of RC beams with widely-spaced stirrups. Namely, with the addition of 1%, 2% and 3% waste lathe scraps, the load-bearing capacity escalated by 9.1%, 21.8% and 32.8%, respectively, compared to the reference beam. On the other hand, the contribution of the lathe scraps to the load capacity decreases with decreasing stirrup spacing, since the closely-spaced stirrups bear the shear stresses and render the contribution of the scraps to shear resistance insignificant. The load capacity, deformation ductility index (DDI) and modulus of toughness (MOT) values of the beams were shown to increase with the volumetric fraction of scraps if the stirrups are spaced at about two times the beam depth. For the specimens with a stirrup spacing of about the beam depth, the scraps were found to have no considerable contribution to the load capacity and the deformation capacity beyond the ultimate load. In other words, for lathe scrap contents of 1-3%, the DDI values increased by 5- 23% and the MOT values by 63.5-165% with respect to the reference beam with a stirrup spacing of 270 mm. The influence of the lathe scraps to the DDI and MOT values were rather limited and even sometimes negative for the stirrup spacing values of 160 and 200 mm.

Key Words
deformation ductility index; diagonal tension; energy absorption capacity; recycled scraps; shear-deficient beam; shear-dominated failure; waste materials

İlker Kalkan: Department of Civil Engineering, Kirikkale University, 71450, Kirikkale, Turkey

Yasin Onuralp Ozkilic: 1)Department of Civil Engineering, Necmettin Erbakan University, 42100, Konya, Turkey 2)Department of Civil Engineering, Lebanese American University, Byblos, Lebanon

Ceyhun Aksoylu: Department of Civil Engineering, Konya Technical University, 42100, Konya, Turkey

Md Azree Othuman Mydin: School of Housing, Building and Planning, Universiti Sains Malaysia, 11800, Penang, Malaysia

Carlos Humberto Martins: Department of Civil Engineering, State University of Maringa, Brazil

Ibrahim Y. Hakeem: 1)Civil Engineering Department, College of Engineering, Najran University, King Abdulaziz Road, Najran, Saudi Arabia 2)Science and Engineering Research Center, Najran University, Najran, Saudi Arabia

Ercan Isik: Department of Civil Engineering, Bitlis Eren University, Bitlis 13100, Turkey

Musa Hakan Arslan: Department of Civil Engineering, Konya Technical University, 42100, Konya, Turkey

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