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Test results of steel-ultra high performance concrete (UHPC) composite beams with welded steel shear keys (SSKs) under four-point bending are presented in this paper. The objective of the investigation is to reduce the self-weight and manufacturing cost of large-span structures. The study investigates the effects of strength of concrete slab, type, spacing and size of SSK, and concrete slab height and width on flexural behavior of composite beams. The experimental results demonstrate that enhancing concrete strength, reducing SSK spacing, increasing concrete slab size, and using large-size SSK can all significantly enhance the flexural performance. The composite beams with welded SSK exhibit a maximum relative slip of less than 4 mm, while the counterpart with welded bolts has a maximum relative slip greater than 4 mm. The study shows that the welded SSK is more effective than welded bolts in improving the interface shear performance of composite beams and improving the stiffness and load capacity. Additionally, the study defines four failure modes of steel-UHPC composite beams, and the formulae for flexural capacity is developed based on the reasonable basic assumptions. The calculated results fit well with the tested results. The research findings can be provided as a technical support for the design and application of steel-UHPC composite beams. • The flexural behavior of steel-ultra high performance concrete composite beams with welded steel shear keys was tested. • Effects of concrete slab and steel shear key on flexural behaviour of composite beams were studied. • Four failure modes of steel-UHPC composite beams were defined, and the formulae for flexural capacity is developed. [ABSTRACT FROM AUTHOR]

Four precast concrete composite walls with embedded extruded polystyrene insulation layer were designed, and the seismic performance was systematically investigated. The failure mode, hysteretic curve, skeleton curve, stiffness degradation, displacement ductility and energy dissipation capacity were explored by quasi-static tests. Moreover, the strain variation of reinforcements at the key positions of the specimens was analyzed and discussed. The test results indicated that the failure mode of the specimen with extruded polystyrene insulation layer thickness of 200 mm was flexural failure, accompanied by the concrete crushing and spalling at the wall toes; while the specimen with extruded polystyrene insulation layer thickness of 100 and 120 mm showed better cooperative working performance. The precast composite concrete wall adding diagonal braces possessed better bearing capacity, deformation capacity and cumulative energy dissipation capacity. Furthermore, the connecting reinforcements at the horizontal joint can effectively transfer stress. Finally, a simplified calculation model of bearing capacity of the precast concrete composite walls with embedded extruded polystyrene insulation layer connected by tooth groove and grouted sleeve was proposed. • An innovative precast concrete composite wall with embedded XPS insulation layer was proposed. • An innovative tooth groove and grouted sleeve connection method was proposed. • The seismic performance of precast concrete composite wall was investigated by quasi-static test. • A simplified calculation model of bearing capacity of precast concrete composite wall was established. [ABSTRACT FROM AUTHOR]

Recently, a new steel-UHPC composite deck system is used for long-span bridges, which uses the perfobond rib (PBL) shear connectors with a thinner steel perforated plate. Because the steel perforated plate is thinner, its failure mode may be different from that of thicker steel perforated plate. To explore the shear behavior of PBL shear connectors in this new composite deck system, five sets of ten specimens are tested in this study. The parameters of the hole diameter, D , the traverse rebar diameter, d s , and the perforated steel plate thickness, t s are considered. The failure modes, strain development versus loading, and some mechanical indexes are discussed. The experiments show that the PBL shear connector with a thinner perforated steel plate causes a shear failure, while the thicker one results in bending or bending-shear failure. According to FE (finite element) analysis, the orthogonal analysis is conducted to investigate the effect of each parameter and their interaction on the mechanical behavior. It is found that the ultimate capacity and stiffness are the most sensitive to the diameter of the traverse rebar, d s , and the perforated steel plate thickness, t s. In addition, a theoretical formula is proposed to predict the bearing capacity of PBL shear connectors. The proposed formula considers the relationship between shear strain and the dilation angle for the first time. The results show a good agreement with the experiments. The study in this paper provides a good reference for the application and optimization of PBLs with a thinner steel perforated plate in new steel-UHPC composite deck system. • Introducing a new steel-UHPC bridge deck with perforated steel plate as the shear connectors and longitudinal rib. • Shear behavior on PBL shear connector in the new steel-UHPC deck is conducted. • The influence of each parameter of PBL shear connector and its interaction on the structure is obtained. • The formula for the shear capacity of PBL shear connector in the new steel-UHPC bridge deck is presented. [ABSTRACT FROM AUTHOR]

The use of aluminum alloy-reinforced coral concrete columns is an effective measure for enhancing the bearing capacity of coral concrete columns. To understand the axial compression performance of aluminum alloy circular tube-reinforced coral concrete short columns, this paper first designed nine short columns for axial compression testing with the parameters of aluminum contents (α , i.e., 0.085, 0.148, and 0.216) and coral concrete strength (C20, C30, and C40). The failure pattern, bearing capacity, and load–deformation relationship was obtained, and the effects of the coral concrete strength (f c), aluminum content (α), and hoop coefficient (ξ) on the bearing capacity, stiffness, and ductility of the combined columns were analyzed. The finite element method was used to analyze the parameter extension. Eight models were subsequently tested for their applicability to determining the bearing capacity of CCFAT circular short columns via experiments and finite element analyzes. The results showed that the failure patterns of the CCFAT short columns were similar, the load–deformation relationships included three stages, and the combination of aluminum alloy round tubes and coral concrete exhibited good performance. The ultimate bearing capacity and axial compressive stiffness increased with increasing coral concrete strength and aluminum content, respectively. The strength index showed approximately quadratic growth with the hoop coefficient, and the stiffness index was positively correlated with the hoop coefficient. Its ultimate strain increased with increasing aluminum content and decreased with increasing coral concrete strength. The yield strain did not show any significant changes in characteristics. The ductility index exhibited a strong positive correlation with the hoop coefficient. The finite element validation results were preferable, the accuracy of the computations was high, the hoop coefficient was more important than the coral concrete strength for enhancing the ultimate bearing capacity, and the Mir or STL model can be used to calculate the bearing capacity of CCFAT short columns. • Local Waist drum shape bucking and shear slip line were the two failure patterns of circular CCFAT. • The failure process of circular CCFAT without an enhancement stage. • A set of load-deformation curves was investigated. • The Finite element analysis on the failure of CCFAT was studied. • Two load capacity prediction formulas based on restrained concrete were proposed. [ABSTRACT FROM AUTHOR]

In this study, the CFRP sheets and CFRP stirrups are employed to confine the compression zone in GFRP-reinforced concrete (GFRP-RC) beams to improve the ductility of the beams. Four-point bending tests are conducted on four CFRP sheets and six CFRP stirrups confined GFRP-RC beams. The cracking bending moment, crack width, mid-span deflection, bearing capacity, and ductility of all the beams are analyzed. Results show that the effect of the confinement in the compression zone on the cracking bending moment and crack width under service load can be ignored. The cracking bending moment can be accurately estimated using ACI 440.11–22, while the GB50608–2020 standard provides an accurate prediction for the crack width under service load. The GFRP-RC beams confined with CFRP stirrups exhibit mid-span deflections reaching up to 95 mm prior to failure. In addition, the CFRP stirrups confinement is more effective compared to CFRP sheets confinement due to the poor bond performance between the CFRP sheet and concrete. Furthermore, an accurate equation for the calculation of bearing capacities of GFRP-RC beams confined with CFRP sheets and stirrups has been proposed. It has also been demonstrated by this study that significant improvements in the ductility of GFRP-RC beams can be achieved by confining the compression zone. Deformation ductility factors of all the beams are analyzed to support this conclusion. • The ductility can be greatly improved by confining the compression zone. • CFRP stirrups confinement is more effective compared to CFRP sheets. • An accurate equation for the bearing capacity has been proposed. [ABSTRACT FROM AUTHOR]

• The eccentric compression behaviors of circular and square CFAT long columns were tested. • The factors of eccentric compression properties of CFAT long columns were discussed. • The applicability of current typical CFST design codes for CFAT long columns was evaluated. In this paper, eccentric compressive experiments of 12 circular and 6 square concrete-filled 6061-T6 aluminum tubular (CFAT) long columns were carried out. The influence of the section form, thickness of aluminum tube, slenderness ratio, and eccentricity on the flexural performance of CFAT long columns was investigated. The results showed that all the specimens exhibited flexural-dominated failure. The variation of eccentricity had little impact on the overall failure mode of the aluminum tube, while it dramatically influenced the failure mode of the internal concrete. The internal concrete failed in concrete crushing for all the square columns, while it remained intact for the circular columns. This indicates that circular tubes provide a better constraint effect on the internal concrete, there by increasing the ultimate strain of concrete under compression. It was also found that the increase of eccentricity leads to the weakening of the confinement afforded to the internal concrete, while the increase of slenderness ratio has no obvious effect on the restraining effect. Finally, the applicability of current design provisions for concrete-filled steel tubular (CFST) long columns to CFAT long columns was evaluated, and design suggestions were proposed. [ABSTRACT FROM AUTHOR]

• The three-point bending tests to study the mechanical behavior of round bamboo under transverse local compression were conducted. • The effects of different parameters on the mechanical behavior of round bamboo under transverse local compression were analyzed. • Prediction equations for the transverse local compressive ultimate bearing capacity of round bamboo were established. Bamboo is a material with low transverse mechanical properties. To study the mechanical behavior of round bamboo under transverse local compression, 60 round bamboo culms were subjected to three-point bending tests. The effects of different parameters on the transverse local compressive behavior were investigated experimentally. Finally, the transverse local compressive ultimate bearing capacity of round bamboo was estimated using prediction equations. The results indicated that under three load boundary conditions, axial cracks appeared on both sides of the specimens in the midspan region, dents of different sizes appeared at the loading points, and additional fractures occurred in the inner diaphragms of the specimens with the loading point at the node. The specimens subjected to point and line loads underwent brittle failure. Under the space-curve load, the specimens with a loading point at the internode exhibited ductile failure, whereas the specimens with a loading point at the node exhibited brittle failure. To obtain a favorable transverse local compressive ultimate bearing capacity, it was optimal to consider the space-curve load as the load boundary condition and position the transverse local compression at the bamboo node. The results of the prediction equations agreed well with the test results. [ABSTRACT FROM AUTHOR]

Highlights • Bearing capacity of cold-formed high strength steel RHS was examined. • A total of 37 web crippling tests was undertaken. • Finite element models were developed and verified against the test results. • Parametric study of 156 specimens was performed on both slender and stocky RHS. • Existing web crippling provisions are evaluated and improved design rules are proposed. Abstract The structural response of cold-formed high strength steel (CFHSS) rectangular hollow sections (RHS) under localised bearing forces is investigated. Web crippling tests were undertaken on cold-formed steel RHS that had nominal yield strengths (0.2% proof stresses) of 700 and 900 MPa. The experiments were conducted under end and interior load cases. The experimental results were utilised in a numerical investigation to verify finite element (FE) models. Upon verification, an extensive parametric study was conducted. The ultimate capacities obtained experimentally and numerically were compared with nominal resistances computed by the current North American Specification, European Code and Australian Standard. Overall, the codified resistance provisions gave either unconservative or overly conservative predictions. Therefore, improved design rules for CFHSS RHS under localised bearing forces were proposed. The reliability of the codified as well as modified design provisions were appraised. It is demonstrated that the modified design rules proposed in this paper can provide reliable predictions for the CFHSS RHS under localised bearing forces. [ABSTRACT FROM AUTHOR]

Highlights • Finite element models of BBC joints were established and verified. • The uniaxial compression bearing capacity of the BBC joint was defined. • Influence factors on the ultimate load of BBC joints were studied. • Formulae of the ultimate load of BBC joints were proposed. Abstract Bolted ball-cylinder joint (BBC joint) is an innovative joint system applied in non-purlin spatial truss structures. According to the theoretical analysis, the fitting formulae of the uniaxial compression bearing capacity of the BBC joint were proposed in this paper. Experiments on 5 BBC joints were introduced briefly at first. The finite element (FE) models were established using ABAQUS and verified by the experimental results. The numerical and experimental results agreed well with each other in failure modes and load-displacement curves. Subsequently, parametric study was conducted to investigate the effects of the dimensions of hollow cylinder, rectangular tube and ribbed stiffener on the bearing capacity of the joint. Finally, the formulae to estimate the uniaxial compression bearing capacity of the BBC joint were obtained by means of regression analysis. And the increasing coefficients of bearing capacity were obtained on the basis of parametric study. The calculation results were verified against the experimental and numerical results. It is indicated that the practical calculation formulae can estimate the uniaxial compression bearing capacity accurately. [ABSTRACT FROM AUTHOR]

Highlights • The influence of fire exposure and column-to-beam bending capacity ratio on the post-fire seismic performance of reinforced concrete frames were investigated experimentally. • Under room temperature, the strong-beam-weak-column frame failed in column-end shearing, the strong-column-weak-beam frame failed in beam-end plastic hinging. • After exposure to fire, the failure modes of both the two frames changed to column shear-bond failure. • The bearing capacity, stiffness, ductility factor, and energy dissipation decreased after fire, and the bearing capacity of the strong-beam-weak-column frame decreased more seriously. Abstract To investigate the post-fire seismic behaviour of reinforced concrete (RC) frames with different column-to-beam bending capacity ratios, four specimens were fabricated, which included a strong-beam-weak-column frame and a strong-column-weak-beam frame either under room temperature or after being exposed to fire. The fire test was conducted in a furnace chamber, followed by quasi-static tests under a low-frequency cyclic load. The crack patterns, hysteretic loops, plastic hinges, and failure modes were investigated in the loading process. The influence of two factors, i.e., the fire exposure and the column-to-beam bending capacity ratio, on the mechanical performance, ductility, stiffness degradation, and energy dissipation was compared and analysed. The experimental results indicated that the ultimate bearing capacity, the stiffness, the ductility factor, and the energy dissipation capacity of the RC frames decreased after fire exposure. The bearing capacity of the strong-beam-weak-column frame decreased even more seriously. Although the yielding displacements of the post-fire frames increased, their ultimate displacements decreased. In addition, the strong-column-weak-beam frame under room temperature failed in the form of beam-end plastic hinging, while after being exposed to fire, the failure mode changed to shear-bond failure in column. [ABSTRACT FROM AUTHOR]

Highlights • Construction details of large dimensional CFST columns are given. • Test samples were extracted from China Zun Tower. • Six CFST columns are investigated by repeated uniaxial compression loading tests. • The hysteretic behaviour, energy dissipation capacity, et al., are discussed. • A bearing capacity calculation method is proposed. Abstract To improve the compression performance and ductility of rectangular concrete-filled steel tube (CFST) columns with large dimensions, longitudinal stiffeners, horizontal tie bars, studs, internal diaphragms, and steel reinforcement cages, were set inside the columns. Six CFST column specimens with different construction characteristics were designed and tested under repeated uniaxial compression loading. Test samples were extracted from the rectangular cavities at the two ends and along the long axis of the mega-column from China Zun Tower. The hysteretic curves, skeleton curves, energy dissipation capacity, bearing capacity, stiffness and strain of specimens, and the effect on the axial compression performance based on different construction characteristics are herein discussed and clarified. Based on the conducted tests on these columns, a bearing capacity calculation method is proposed. The test results indicate that the longitudinal stiffeners set inside the CFST columns facilitate the sharing of axial forces and strengthen the stiffness, bearing capacity, and ductility. The horizontal tie bars help the improvement of the constraint of the concrete at loads higher than the ultimate load. Welding studs on the inner surface of the steel tubes help to strengthen co-operative work between the steel tubes and the concrete upon application of the ultimate load. Setting internal diaphragms inside CFST columns can enhance the ultimate bearing capacity and energy dissipation significantly. The setting of steel reinforcement cages inside the CFST columns stabilizes the mechanical performance manifested by the significant improvements in the ultimate bearing capacity and ductility. [ABSTRACT FROM AUTHOR]

Highlights • A new connection named ECS connection at precast concrete beam end was developed. • Static bearing capacity experiments on twelve ECS connections were conducted. • The ultimate load of the ECS connection was investigated by parametric studies. • The optimum design of the ECS connection was proposed. Abstract Embedded channel-shaped steel (ECS) connection at precast concrete beam-end proposed in this paper is a kind of novel connection. To study the performance of ECS connection, experiments on 12 specimens were carried out. The embedded length of the ECS, the stirrup spacing, the cavity in the mid-span of the beam and the eccentricity of the ECS were taken into account. Two kinds of failure modes were observed: lever-out of ECS and crushing of the beam-end concrete. The experimental results indicate the following: (1) as the length of ECS increases, the bearing capacity of the ECS connection increases; (2) the stirrup densification could significantly improve the bearing and deformation capacity; (3) the mid-span cavity of the beam has limited influence on the bearing and deformation capacity of the connection; (4) the eccentricity of ECS could slightly reduce the bearing capacity owing to the additional torsion. Subsequently, finite element (FE) models were developed using ABAQUS and validated by the test results. The FE simulations show good agreement with the test results. Based on the verified FE models, a parametric study was conducted, considering different ECS properties including embedded length, section and eccentricity, various stirrup spacing at the beam-end, concrete grade and the distance between cavity and ECS. Finally, to prevent the lever-out of ECS, the optimum design of the ECS connection was proposed according to previous discussion. [ABSTRACT FROM AUTHOR]

• Three failure modes are observed with the increase in the eccentricity. • There exist two inflection points in theoretical N-M interaction diagrams. • The failure modes are affected by the axial stiffness of longitudinal bars. Using FRP bars instead of steel bars to reinforce concrete columns in harsh environments has become an important method for solving corrosion problems. FRP bars have high tensile strength but low compressive strength and high brittleness, while stainless steel (SS) bars have high tensile and compressive strength and good ductility. Therefore, this paper studied the eccentric compression behavior of seawater and sea sand concrete (SSC) columns reinforced with GFRP and SS bars, in which GFRP bars were arranged on the tension side and SS bars were arranged on the compression side to improve the ductility and to analyze the effect of axial stiffness of reinforcement on the N-M interaction diagrams. A total of 48 SSC columns were designed, of which 20 were reinforced with GFRP and SS bars, 14 were reinforced with GFRP bars and 14 were reinforced with SS bars. To analyze the eccentric compression performance of SSC columns and propose the bearing capacity calculation equation, test variables were designed, including the reinforcement type, reinforcement ratio, and eccentricity, to ensure that the equation had certain universal applicability. The three failure modes of compression failure, combined compression-bending failure, and bending failure were found with the increase in the eccentricity for the GFRP and SS bars reinforced SSC (GFRP-SS-SSC) columns. The ductility indices of the GFRP-SS-SSC columns were approximately 1.5 times those of the GFRP bars reinforced SSC columns, which indicated that the ductility could be improved by replacing the compression GFRP bars with SS bars. Finally, the theoretical N-M interaction diagrams were established through the cross-section force analysis and compared with the experimental N-M interaction diagrams. Moreover, the failure mode is influenced by varying the axial stiffness of the longitudinal bars on both sides of the column section by analyzing the N-M interaction diagrams. [ABSTRACT FROM AUTHOR]

This paper aims at contributing to a better understanding of the physical-mechanical behaviour of partially loaded areas in reinforced concrete. Following a review of the current state of the art on this topic, which includes a description of the mechanical behaviour and existing predictive models, a remarkable knowledge gap in this standard problem is revealed. A new stress field solution for reinforced concrete blocks under strip loading is developed herein which is based on the lower-bound theorem of limit analysis and adopts a modified Coulomb failure criterion for concrete. Contrary to existing empirical design rules, the new mechanical model consistently accounts for the behaviour of concrete under multiaxial compression as well as the favourable effect of transverse reinforcement. While a comparison of the ultimate loads predicted using the new stress field solution shows a good correlation with the available test data, further experiments are required particularly for the validation of the predicted higher resistances of heavily confined areas as compared to existing design rules. [ABSTRACT FROM AUTHOR]

The bolted-flange connection is used to connect rectangular HSS columns in prefabricated multi-story and high-rise steel structures. It may subject to coexisting axial compression, bending moments and shearing under the combination of dead, live, wind loads or earthquake action. The bearing performance is different from that of bolted-flange connections used in pipelines, towers and mast structures. To investigate the bearing performance of a connection subjected to coexisting compression, bending moments and shearing, static tests and a finite element analysis (FEA) were applied to 12 column-to-column bolted-flange connections with different flange thicknesses, bolt edge distances, flange edge widths and bolt hole diameters, as well as one column without connection. The effects of flange thickness, bolt edge distance, flange edge width, and bolt hole diameter on the stiffness and strength of connections, bolt tension levels, and contact forces between flanges were obtained as well as effects on the failure mode and mechanisms of the connections. Flange thickness was found to have a considerable impact on the performance of connections, while the bolt edge distance and flange edge width were found to have a lesser effect. The FEA results agree well with the test results, verifying the finite element model (FEM). Some performance results that could not be obtained through testing were obtained. Based on yield line theory and T-stub analogies, the load transfer mechanism of bolted-flange connections was obtained and formulas for yield-bearing capacity are proposed. The results obtained from the formulas agree well with the test and FEA results. [ABSTRACT FROM AUTHOR]

Axial compression tests of circular concrete-filled steel tubes with different diameters (219 mm, 426 mm, and 630 mm) and ratios of tube diameter to steel thickness (55 and 88) were conducted to investigate the effect of size on the bearing capacity. The experimental results indicated that the peak nominal stress decreased as the size increased, and the decrease in the nominal stress due to the size effect increased at higher ratios of diameter to thickness. At the peak load moment, an increased specimen diameter corresponded to a decreased hoop stress in the steel tube as well as a decreased concrete strength due to the confinement effect of the steel tube. When the ratio of diameter to thickness increased, the extent of reduction of the hoop stress and the confining effect of the steel tube influenced by the increasing specimen size increased. However, the vertical stress in the steel tube was increased at increased size, and increases in the ratio of diameter to thickness improved the increase degree of the vertical stress of steel tube due to the enlargement of specimen size. Hence, the vertical bearing capacity of the steel tube was affected by both the specimen size and the ratio of diameter to thickness. Based on the size effect law (SEL) proposed by Bazant, and taken the effect of the ratio of diameter to thickness into consideration, a size-dependent formula to evaluate hoop stress in the steel tube was developed. A size-related model considering situations with different ratios of diameter to thickness was established in order to estimate the bearing capacity of large-size circular concrete-filled steel tubes. The model and experimental results showed good agreement. [ABSTRACT FROM AUTHOR]

• Four balanced failures defined for corroded RC columns in eccentric compression. • Six failure modes identified for corroded RC columns in eccentric compression. • Failure mode-based bearing capacity calculation method proposed for corroded RC columns under eccentric compression. This paper proposed a failure mode-based calculation method for bearing capacities of corroded RC columns under eccentric compressive loads, which considered corrosion-induced mechanical property degradation of steel bars, cross-sectional reduction of steel bars and cross-sectional reduction of concrete. Through analyzing the stress and strain distributions over the normal cross-section, four balanced failures and six failure modes were identified for corroded RC columns under eccentric compressive loads. Balanced corrosion degrees were defined and methods to calculate them were proposed. Based on corrosion degree and balanced corrosion degrees, the failure mode of an eccentrically compressed corroded RC column could be predetermined in advance. Then, the methods to calculate the eccentric compressive bearing capacity under each failure mode were proposed. Subsequently, a dataset of eccentric compressive tests on 118 corroded and 27 non-corroded RC columns was established. The eccentric compressive bearing capacities calculated by the proposed failure mode-based method were found in good agreement with the test results, which demonstrated the validity of the proposed method. The failure mode-based calculation method will contribute to not only rapid and accurate performance evaluation of existing corroded RC columns, but also fast and efficient time-dependent reliability analysis for planned RC columns. [ABSTRACT FROM AUTHOR]

The behaviour and design of cold-formed ferritic stainless steel tubular structural members subjected to concentrated bearing loads are presented in this paper. A total of 37 web crippling tests was conducted on cold-formed square and rectangular hollow sections of grade EN 1.4003 ferritic stainless steel. The tests were conducted under end loading and interior loading conditions, which closely simulated the support conditions of floor joist members seated on solid foundation. Finite element (FE) models were developed and validated against the experimental results. Upon validation of the FE models, a parametric study comprised 160 FE analyses was performed using the validated models. The web crippling strengths obtained from experimental and numerical investigations were compared with the nominal strengths calculated using the current American, Australian/New Zealand and European specifications for stainless steel structures. Furthermore, the North American Specification (NAS) and the Australian Standard AS4100 for carbon steel structures as well as the suggested design rules in the literature for stainless steel structures were also compared. Improved design rules are proposed for ferritic stainless steel tubular structural members subjected to concentrated bearing loads by means of modified NAS and Direct Strength Method. The reliability of the proposed design rules has been assessed through reliability analysis. [ABSTRACT FROM AUTHOR]

Although the bolted side-plating (BSP) technique is feasible to upgrade the shear capacity of reinforced concrete (RC) beams, related studies on its strengthening effect have yet to be sufficient. Therefore, an experimental study of seven specimens was conducted to investigate the shear performance of BSP beams. The failure mode was found shifting from shear–tension to shear–compression after strengthening. The decrease of bolt spacing, the increase of plate breadth and thickness improved the shear capacity, stiffness and ductility effectively. Although the additional stiffeners improved the stiffness considerably, it exhibited no obvious improvement in the shear capacity and caused a serious reduction in ductility. Due to the shear deformation of bolt shaft and the tensile principal stress in the steel plates that was perpendicular to the main diagonal crack, uneven relative longitudinal and transverse slips existed on the interface between the bolted steel plates and the RC beams. An analytical model was developed according to the force equilibrium and deformation compatibility of the beam segment in the shear span. A design procedure, which can be conducted conveniently using ordinary computing software or even a calculator by structural engineers in their strengthening design practise, was also provided to estimate the shear bearing capacity of BSP beams. [ABSTRACT FROM AUTHOR]

• A multiple-cell section steel shell-concrete composite structure(SSC structures) for the bridge tower was proposed. • The uniaxial compressive tests of two specimens were conducted with different concrete strengths, and the experimental results were verified by nonlinear finite element simulation. • Failure modes and carrying capacity of specimens were conducted. • The load transfer mechanism and the influence of section form and material strength on bearing capacity were analyzed. To improve the mechanical performance and construction convenience of the bridge towers, a steel shell-concrete composite tower (SSC structures) was proposed. The steel shell consists of outer and inner steel plates, diaphragms, and stud connectors inside the cells. Then the high fluidity concrete is poured into the steel shell to form the composite tower. Through the uniaxial compressive tests of the specimens with different concrete strength and the nonlinear finite element parametric analyses, the force transfer mechanism of the steel shell, the infilled concrete, and the stud connectors at the steel–concrete interface were revealed. The results show that the proposed steel shell-concrete composite tower has a higher bearing capacity than the conventional concrete-filled steel tube tower, in which the bearing capacity of concrete was increased by about 20% from the test results due to the composite effect between steel and concrete. Diagonal breakage bands were formed when the specimens finally failed, on which the concrete was crushed, and the steel plates had large out-of-plane deformation and weld cracking. Through finite element calculation, it was found that the increase of stud forces mainly occurred after the yield of the steel wall plates, and the maximum values of the shear forces and tension forces were 3.6 kN and 4.7 kN, respectively. The results also show that the multiple-cell section has better mechanical performance than the double steel section, which is suitable for the section form of the composite bridge tower. [ABSTRACT FROM AUTHOR]

• A novel SPCW with PEC columns and welded reinforcement grids is proposed. • The SPCWs exhibited good seismic behaviors under a reasonable axial compression ratio. • The effect of diagonal cross-distribution reinforcement on the shear wall was studied. • Residual displacement formulae were established to assess post-seismic repairability. • The flexural bearing capacity and shear bearing calculation formulae were proposed. An innovative shear wall was proposed by introducing partially encased composite (PEC) columns and welded reinforcement grids (WRGs) into steel plate concrete composite shear wall. This work conducted an experimental investigation of the seismic behavior of seven 1/3-scale proposed walls subjected to cyclic lateral loading. The design parameters included the forms of distribution reinforcement, axial compression ratio, thickness of the built-in steel plate, shear-to-span ratio and thickness of the PEC column-section steel flanges. The results revealed that the specimens had good bearing capacity, deformation ability, energy dissipation capacity, and stiffness under a reasonable axial compression ratio. Compared with a specimen featuring orthogonal distribution reinforcement, the cracking load and ductility of a specimen with diagonal cross-distribution reinforcement were increased by 6.5% and 13.6%, respectively. And increasing the thickness of the built-in steel plate and the PEC column-section steel flanges could augment the bearing capacity and ensure the late stiffness of the specimens. Then, the residual displacement fitting formulae were presented herein to assess post-earthquake repairability. Besides, the bearing capacity calculation formulae of the novel shear wall with certain prediction accuracy were proposed. Finally, finite element models of the tested specimens were established in ABAQUS and validated with experimental results. Also, further investigations regarding the influence of axial compression ratio and shear-to-span ratio were implemented by finite element analysis and engineering recommendations for the designed axial compression ratio limits of the novel shear were given. [ABSTRACT FROM AUTHOR]

• Explored the influence of different UHPC-based rehabilitation forms with the post-installed rebar connection. • Clarified the mechanism of different failure modes with the different embedded depths of post-installed rebar. • Established and verified a method to determine the minimum embedded depth required for the post-installed rebar. • Characterized the force–displacement curves of the post-installed rebar connection under shear loads. • Proposed a calculation formula to estimate shear bearing capacity for post-installed rebar connection. The reliable bonding effect between the ultra-high performance concrete (UHPC) layer and the existing reinforced concrete (RC) components is always expected when UHPC is used to rehabilitate deteriorated RC structures. The post-installed rebar connection has been demonstrated to possess robust mechanical performance. However, no research to date clarifies how to design the post-installed rebar connection in engineering practice. To this end, this study conducted 34 push-out tests to investigate the interfacial shear performance of UHPC-strengthened RC structures using post-installed rebar connections. The primary variables in the tests included strengthening form, embedded depth of rebar, rebar diameter, rebar spacing, and substrate type. Based on the test results, three different failure modes were identified. The analytical results indicate that the embedded depth of the rebar has a significant influence on the performance of the post-installed connection. A formula was proposed to determine the minimum embedded depth, and its accuracy was validated by the physical experiments. The load-bearing mechanisms were revealed based on the experimentally measured force–displacement curves. The shear capacity of the connection mainly comprises the adhesive effect, rebar shearing, and friction. The connection capacity can be approximated by the rebar shear capacity due to its robust shear resistance. Also, a formula was proposed to estimate the shear capacity of the rebar. The experimental and theoretical results facilitate the design and application of post-installed rebar connections in UHPC-strengthened RC structures. [ABSTRACT FROM AUTHOR]

• The mechanical behaviour of concrete under local compressive forces is reviewed. • A knowledge gap exists in the theoretical understanding of the problem. • Stress fields for plane and axisymmetric bearing capacity problems are presented. • The stress fields have several advantages over existing design approaches. • A step towards mechanically-based design rules for partially loaded areas is made. The introduction of high compressive forces on concrete members over limited contact areas is a common problem in engineering practice. Despite extensive research, a knowledge gap persists in the mechanical understanding of this seemingly simple problem. This paper first summarises the state of the art regarding the bearing capacity problem in structural concrete and then introduces two new stress field solutions for plane and axisymmetric cases of partial area loading. Contrary to most existing design approaches, which are purely empirical, the models proposed build on consistent mechanical bases that ensure safe design. The stress fields consider consistently the beneficial effect of reinforcement and the multiaxial compressive strength of concrete. Moreover, they enable the flow of forces to be followed through the structure, resulting in consistent dimensioning and detailing of the reinforcement. The comparison with existing design approaches shows that the stress fields predict significantly higher bearing capacities, enabling the design of more efficient and sustainable structures. In a companion paper, the stress fields are validated with published experimental data and an extensive test campaign conducted by the authors. [ABSTRACT FROM AUTHOR]

• Torsional behavior tests on composite girders with CSW-CFST truss chords are conducted. • Sectional form, twist failure mode and torsional behavior are obtained. • A method for calculating the compound stiffness of CFST specimens is proposed. • A novel method for calculating the torsional bearing capacity of composite girders with CSW-CFST truss chords is proposed. Torsional behavior tests and a theoretical analysis were conducted on the composite girders with corrugated steel webs and concrete-filled steel tubular (CSW-CFST) truss chords. Their performance was compared with that of composite girders with circular hollow section (CSW-CHS) truss chords and composite box girders with CSW-CFST chords. The study revealed the influence of the concrete in the chord and the sectional form of the composite girders on their twist failure mode and torsional behavior. The test results showed that the sectional form of composite girders with CSW-CFST truss chords can perform as well as closed box cross-sections. The point of twist failure was found to be when the concrete roof obliquely cracked with an angle of 45° between the crack and the girder axis and the rebar had already yielded. The concrete in the chord contributes to the torsional stiffness and bearing capacity of composite girders. The paper puts forward a method for calculating the compound stiffness of CFST specimens by superposing their linear stiffness. Then, on the basis of the four types of twist failure that can affect composite girders with CSW-CFST truss chords, a method for calculating their torsional bearing capacity is proposed. The deviation between the results acquired using the proposed method and the results from the tests and a finite element analysis is less than 8.5%. [ABSTRACT FROM AUTHOR]