Abstract
In this study, seven steel and concrete composite beams (SCCBs) connected by T-shaped perfobond rib
(PBL) shear connectors were tested to evaluate cracking performance in the hogging moment area. The selected
parameters included the type of shear connectors, T-shaped PBL flange widths, and reinforcement ratios. The impact
of these parameters on the crack distribution and load-crack width relationship was emphasized in this study. Finally,
a modified method was developed that accounts for the T-shaped PBLs to estimate the average crack spacing and
maximum crack width in the hogging moment regions of the composite beams. It was found that the flange enhances
the cracking performance of the T-shaped PBL connectors. Compared with the composite beam with a flange width
of 70 mm, the average crack spacing of 100 mm- and 130 mm-width decreased by 22% and 24%. The reinforcement
ratio was a crucial factor affecting the cracking performance of the composite beam. The modified equations provided
accurate predictions for the maximum crack width and mean crack spacing, with average calculated-to-test ratios of
0.92 and 1.00, respectively, and standard deviations of 0.11 and 0.09. This research could improve understanding of
the cracking performance of SCCBs connected with T-shaped PBLs and provides guidance for crack control design.
Key Words
crack spacing; crack width; negative moment zone; steel-concrete composite beam; T-shaped PBL
Address
Wenfeng Huang: Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China
Yulin Zhan:1)Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China
2)Institute of Civil Engineering Materials, Southwest Jiaotong University, Chengdu 610031, China
Wenting Lyu:Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China
Hengjia Zhang:Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China
Haijun Jiang:Qingdao Municipal Engineering Design and Research Institute Ltd, Qingdao, 266000, China
Junhu Shao:1)Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China
2)School of Architecture and Civil Engineering, Chengdu University, Chengdu 610106, China
Abstract
This study investigated the effect of fiber type on the mechanical behavior of sandwich composite
structures with a rubberized cork core. The specimens were fabricated using Kevlar/epoxy and glass/epoxy as face
sheets, while a low-density, energy-absorbing rubberized cork was used as the core material in all samples. The
manufacturing process was carried out through hand lay-up, followed by pressing and oven curing to ensure proper
bonding and final mechanical strength. To evaluate the mechanical performance, the samples underwent standard
three-point flexural and low-velocity impact tests. The flexural test results indicated that although both types of
composites exhibited suitable elastic behavior in the initial stages, their ultimate flexural strength was relatively low,
with failure occurring under moderate loads. In impact tests, Kevlar/epoxy face sheet samples demonstrated higher
impact resistance and suffered relatively less damage, whereas glass/epoxy samples showed greater vulnerability and
experienced larger deformations. Analysis of force-time, force-displacement, and energy absorption curves revealed
that the cellular structure of cork played a crucial role in preventing full penetration and effectively absorbing part of the impact energy.
Abstract
The resistance, stiffness, and ductility of steel-concrete composite structures depend on the distribution of
connector shear forces, which is affected by the connector deformations under the load. This paper presents several
machine learning (ML) models with optimized hyperparameters for predicting load-slip curves of headed shear studs
in solid slabs composed of lightweight or normal weight concrete with a compression strength ranging from 30 to 113
MPa. The developed models are based on the following ML algorithms: extreme gradient boosting (XGBoost), light
gradient boosting machine (LightGBM), gradient boosting with categorical features support (CatBoost), and natural
gradient boosting (NGBoost). The first three models predict deterministic (mean) values of the relative shear load
within the stud based on the specified slip; concrete compressive strength; stud tensile strength, diameter, and height;
slab reinforcement position; and concrete density. The NGBoost model produces mean and probabilistic values of the
stud relative shear load from the same inputs. The models were developed using a database of 10,950 load and slip
measurements from 180 push tests compiled by the present authors from the literature. Model predictions were
interpreted using the SHapley Additive exPlanations (SHAP) method, which indicated that the relative shear load is
most significantly affected by slip, followed by concrete compressive strength and stud tensile strength, which were
found to be significantly less important for model predictions. The shear stiffness and slip capacity determined from
the predicted curves in accordance with prEC4 and AISC 360 showed good agreement with those obtained from the
experimental curves. The developed ML models outperformed several existing load-slip models. A web application
was developed and published online to predict load-slip curves using the CatBoost and NGBoost models, and to
determine the shear stiffness and slip capacity from the predicted curves using various criteria. The proposed models
provide important information for future numerical and analytical studies investigating the dependence of the
resistance, stiffness, and ductility of steel-concrete composite structures on stud deformations, thereby facilitating the
development of improved design provisions.
Abstract
Current research on aluminum alloy composite structures primarily focuses on concrete-filled CFRP
aluminum alloy tubular columns, and studies on aluminum alloy-steel-concrete composite columns have been
scarce. The aim of this study was to investigate axial compressive behavior of concrete-filled aluminum alloy circular
tubular stub columns with in-built H-steel through axial compression experiments and the finite element (FE)
method. Eight stub columns were used in the experiments, with the internal core concrete type and H-steel content
taken as variation parameters. Analysis revealed that the location of the bulging failure of the specimen was
influenced by the internal core concrete type. The aluminum alloy tube and H-steel exhibited good deformation
coordination under axial compression. Parametric analysis showed that the in-built H-steel can effectively inhibit the
transverse deformation of concrete and delay the damage of stub column specimens. When the same type of concrete
was used, the axial compression capacity, axial compressive stiffness, and energy absorption of the columns
increased with the increase in steel content. When the steel content was maintained, the specimens with lightweight
concrete exhibited higher bearing capacity and axial compressive stiffness. For energy absorption behaviors, the
specimens with lightweight concrete and steel content of 8.76% exhibited superior performance. An expanded
parameter analysis was conducted utilizing the FE method. Based on the results, a bearing capacity calculation
formula for the composite columns was proposed using the superposition theory. The findings of this study can help
address the durability issues of steel-concrete and aluminum alloy-concrete members and thus improve structural
performance.
Key Words
axial compression; damage analysis; FE modelling; in-built H-steel; simulation
Address
Bing Li:1)School of Civil Engineering, Shenyang Jianzhu University, Shenyang 110168, China
2)School of Architectural Engineering, Liaoning Vocational University of Technology, Jinzhou121000, China
Jia Li:1)School of Civil Engineering, Shenyang Jianzhu University, Shenyang 110168, China
2)School of Architectural Engineering, Liaoning Vocational University of Technology, Jinzhou121000, China
Bo Zhou: School of Civil Engineering, Shenyang Jianzhu University, Shenyang 110168, China
Abstract
The production of wire with improved mechanical properties, capable of withstanding significant loads
and maintaining integrity for a long time, faces certain technological limitations. Therefore, thermomechanical
processing becomes the optimal solution for high-quality wire obtaining. Technology of stainless wire
thermomechanical processing developed in this work consists of preliminary heat treatment - hardening at a
temperature of 1050°C and traditional drawing with subsequent cryogenic cooling after each deformation cycle. A
comparison of wire intermediate heating effect to room temperature between deformation cycles was also made,
which did not change stainless steel wire microstructure and properties. The use of intermediate heating led to the
formation of a unique gradient martensitic- austenitic microstructure in stainless steel wire. A nanostructured layer
with a grain size of about 500 nm was formed on the surface. This thin, high-strength shell smoothly transitions into a
zone with a gradually increasing grain size as it approaches the center of the wire. If intermediate heating to room
temperature is not used between deformation cycles, then heating in the deformation zone does not occur. In this
case, after three deformation cycles, the microstructure becomes martensitic throughout the volume of wire with 400
nm size grains.
Key Words
drawing; microstructure; martensite; nitrogen; steel; wire
Address
Irina E. Volokitina:Department of Metallurgy and Mechanical Engineering, Karaganda Industrial University,
Respublika Avenue 30, Kazakhstan
Andrey V. Volokitin:Department of Metallurgy and Mechanical Engineering, Karaganda Industrial University,
Respublika Avenue 30, Kazakhstan
Bakhyt A. Zhautikov:Department of Metallurgy and Mechanical Engineering, Karaganda Industrial University,
Respublika Avenue 30, Kazakhstan
Gulnura Zhumanazarova: Department of Metallurgy and Mechanical Engineering, Karaganda Industrial University,
Respublika Avenue 30, Kazakhstan
Abstract
With the increasing degree of assembly in prefabricated utility tunnels, their structural mechanical
performance has diverged from that of cast-in-place counterparts. The connection joints of prefabricated assembled utility tunnels have become structural weak points, where the reliability of connection performance significantly impacts operational safety. To investigate the seismic performance of groove-type prefabricated utility tunnel joints with straight-bolt connections, L-shaped tunnel joints with different bolt diameters and quantities were designed and subjected to quasi-static tests. Experimental results revealed that the typical failure manifested as crushing failure of the concrete in the spliced joint region, with radial crack systems forming at the bolt connection areas of the inner walls, outer walls, and side walls. Additionally, the concrete surrounding the bolt holes exhibited significant compressive damage due to localized stress concentrations. Increasing bolt diameters and quantities enhanced joint ductility coefficients by 27.4%-37.5%, with enhanced bolt constraint effectively delaying concrete crushing progression. Joint stiffness degradation rates decreased by 18%-22%, while energy dissipation values increased by 11.48%-31.06%, demonstrating favorable seismic performance. Based on experimental findings, a joint model was established for mechanical performance analysis, accompanied by a proposed methodology for determining joint mechanical states and a simplified calculation method for ultimate bearing capacity of tunnel joints. Finite element simulations validated the accuracy of the method and confirmed structural safety under extreme conditions. The research outcomes provide theoretical foundations for the study and application of groove-type prefabricated assembled utility tunnels.
