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• Six static tests on S-UHPC-S composite deep beams are carried out. • Failure mechanism of S-UHPC-S composite deep beams is explored systematically. • Quantitative relationships are obtained by FE simulation analysis. • Theoretical models considering bond-slip are proposed. Configurations of steel faceplate (SP) and filled concrete (FC) are the main concern issue in steel- ultra-high performance concrete (UHPC) -steel (SUS) composite deep beams, which have important effects on failure modes, mechanical behaviors and interfacial slip. This paper aims to quantify the relationship between failure modes and configurations of SP. Results can be used to explore the failure mechanism and propose the theoretical models of SUS composite deep beams. 6 SUS composite deep beams were measured. Results indicate that SUS composite deep beams with different configurations of SP and FC, exhibit different failure modes, including shear without slip failure, slip failure and flexural without slip failure. Influence mechanism of SP, FC, spacing of shear studs on failure modes, mechanical behaviors and interfacial slip was explored. Failure mechanism was revealed by a modified Strut-and-Tie model. Subsequently, finite element (FE) models of SUS composite deep beams were developed to obtain the width of concrete diagonal strip, and configuration relationship between SP and FC. Based on the test results and FE results, the theoretical models of SUS composite deep beams corresponding to different failure modes were deduced and validated, considering the interfacial slip between SP and FC. [ABSTRACT FROM AUTHOR]

Steel-concrete-steel composite structures (SCS-CS) with ultra-high performance concrete (UHPC) exhibit wide potential applications in civil constructions. This paper aims to revealing the failure mechanism, proposing the theoretical models and conducting the reliability assessment of SCS composite beams with UHPC (SUS-CB). Firstly, several static tests on SUS-CB were summarized to analyze the failure features and failure modes. A nonlinear finite element (FE) model of SUS-CB was developed and validated. Parametric study was carried out to explore the structural behaviors of SUS-CB, including matching relationship between steel plate (SP) and core UHPC, and bond-slip. Subsequently, failure mechanism of SUS-CB was revealed and failure modes were defined systematically. Considering slippage and effects of steel fibers, the novel theoretical model of calculating ultimate capability of SUS-CB was proposed and compared with existing design codes. Based on these theoretical models, uncertainties of statistics variables were calculated, and reliability analysis of SUS-CB was conducted. Results indicate that reliability index of these theoretical models and design codes is lower than target reliability index. Consequently, adjustment factors of ultimate capacity were calculated to confirm reaching the target reliability index in offshore structures. Finally, sensitivity analysis of statistic variables was performed to provide advices for offshore structural design. • Failure mechanism of SCS composite beams with UHPC is explored systematically. • Theoretical models considering bond-slip are proposed. • Uncertainties of statistics variables are determined. • Reliability analysis is performed to meet the demand of structural design. [ABSTRACT FROM AUTHOR]

• Eight SCS and S-UHPC deep beams under static loads are tested. • Effects of shear span ratio, concrete type and shear stud spacing are explored. • Failure mechanism of specimens is analyzed by a modified Strut-and-Tie model. • A slip coefficient is deduced to design the shear connectors reasonably. • Theoretical models of ultimate capacity with different failure modes are proposed. In this study, a type of steel–concrete–steel (SCS) composite deep beam with ultra-high-performance concrete, named S-UHPC deep beam, was developed. Eight simply supported deep beams, including three SCS deep beams and five S-UHPC deep beams, were tested under static loads. The effects of different parameters (including the shear span ratio, concrete type, and shear stud spacing) on the ultimate capacity, ductility, and interfacial slip of the specimens were explored. Moreover, the observed failure modes were categorized into shear failure without slip, slip failure, and flexural failure with the snapping of steel fibers. To analyze the failure mechanism systematically, finite element (FE) models of the specimens were established and validated. By analyzing the FE simulation results on the compressive damage and stress distribution of the filled concrete, the von Mises stress distribution of shear studs, and the equivalent plastic strain distribution of the bottom steel faceplate, the failure mechanism of the specimens with the observed failure modes was simplified as a modified Strut-and-Tie model. Based on the force transfer analysis of the modified Strut-and-Tie model, a slip coefficient was deduced to quantify the composite action and provide theoretical supports for the reasonable design of shear connectors. Theoretical models of SCS deep beams and S-UHPC deep beams with different failure modes were presented to predict the ultimate capacity. [ABSTRACT FROM AUTHOR]

A novel steel–concrete–steel composite structure constructed using ultra high-performance concrete (forming an S-UHPC composite structure) was applied in Arctic offshore structures. This type of structure can withstand ice pressure derived from impinging sheet ice in the Arctic region. In this study, the failure mechanism of S-UHPC composite beams was explored experimentally and analytically, considering the effects of steel fibers in UHPC. Five groups of push-out tests were conducted to reveal the interfacial performance between steel plates and UHPC. Static tests on S-UHPC composite beams were performed to study their structural behaviors. The results indicate that steel fibers have a significant effect on the failure modes, slippage behavior, and mechanical behavior of the S-UHPC composite beams. Furthermore, on the basis of test results, finite element (FE) models of the push-out tests and static tests of the S-UHPC composite beams were developed and validated. Further, a parametric study was carried out to summarize the failure modes of the push-out tests and to explore the influence mechanism of steel fibers on the structural behavior of the S-UHPC composite beams. Finally, an analytical model for predicting the ultimate strength of S-UHPC composite beams was proposed and compared with existing design codes. • Push-out tests and static tests on S-UHPC composite beams are carried out. • Effect of steel fiber on structural behavior of S-UHPC composite beams is studied. • Failure mechanism of S-UHPC composite beams is explored systematically. • Analytical model of ultimate strength for S-UHPC composite beams is proposed. [ABSTRACT FROM AUTHOR]

• Static tests of SCS composite beam with UHPC and without cross ties are carried out. • Effect of cross ties on composite action between steel plate and concrete is studied. • Influence mechanism of match between steel plate and core concrete is investigated. • Contribution coefficients of steel plates to ultimate strength are proposed. • Failure patterns judgment regulations of SCS composite beams with UHPC are explored. Steel–concrete–steel (SCS) composite structures are widely applied in nuclear power plants, tunnels, and offshores. In this study, steel-fiber-reinforced ultra-high performance concrete (UHPC) is adopted as a core material to improve the structural behaviors of SCS composite structures. A series of static tests on SCS composite beams with UHPC under shear loads are performed to analyze failure patterns and failure mechanism. Results indicate that match relation between steel plates and core UHPC has an important effect on the structural behavior of SCS composite beams with UHPC; furthermore, effects of cross ties on the composite action between steel plates and core materials cannot be neglected. In addition, three-dimensional finite element (FE) models for SCS composite beams with UHPC are established and verified to investigate the effects of match relation between steel plates and core UHPC on the failure mechanism. Based on the experimental and FE simulation results, contribution coefficients of steel plates are proposed to reflect the composite action between steel plates and core materials for SCS composite beams with UHPC. Moreover, the judgment method of failure patterns for SCS composite beams with UHPC is studied. Finally, analytical method to predict the ultimate resistance for SCS composite beams with UHPC is presented and validated by comparison with ACI 349-06 and JEAG 4816 codes. [ABSTRACT FROM AUTHOR]