Spiral Steel Research Articles

Axial compressive performance of spirally reinforced high-strength CFST column

The concrete-filled steel tubular (CFST) member using high-strength materials could have less ductility than its counterpart using normal-strength materials. In this study, spiral reinforcement is used to enhance the performance of CFST columns using high-strength materials. Experiments were conducted for spirally reinforced high-strength CFST stub columns. The highest yield strengths of spiral reinforcement and steel tube were 1597.6 MPa and 771.7 MPa, respectively, and the highest compressive strength of concrete was 103.1 MPa. Results showed that the presence of high-strength spiral reinforcement effectively improved both the strength and ductility of composite columns, while the fracture of spiral reinforcement was observed in tests. A numerical study revealed that spiral reinforcement provided effective confinement to the high-strength core concrete. The steel tube and spiral reinforcement reached respective yield strength corresponding to peak load. The spirally reinforced CFST column exhibited higher resistance than the equivalent normal CFST column using a thick tube. A design-oriented strength prediction method was proposed and was validated against the test data. The average ratio of formula-predicted to experimental resistances was 0.934, with a coefficient of variation being 0.079.

Behavior of GFRP reinforced concrete columns confined with inner steel spirals

AbstractThe paper investigates the behavior of glass‐fiber reinforced polymer (GFRP) reinforced concrete columns with integrated steel spirals (hybrid reinforcement). Six concrete columns were tested under eccentric axial loading, resulting in failure due to bending. Columns with outer steel longitudinal bars experienced steel yielding at peak loads, while those with GFRP outer rebars failed due to concrete crushing. The results revealed that using GFRP as outer longitudinal bars led to peak loads 3–10% lower compared to columns with steel rebars. Inner confinement by steel spirals increased the load‐carrying capacity. Additionally, columns with inner tubular steel exhibited greater strength than those with steel spirals, indicating a slightly enhanced confinement effect. A finite element model was developed to analyze structural behavior, considering both material and geometric nonlinearity. The model's accuracy was validated by comparing predictions with test results. Parametric analysis from the nonlinear FE model showed that eccentricity significantly impacted column load‐carrying capacity. Increasing inner confinement area and the number of inner longitudinal bars improved structural stiffness and load‐carrying capacity. Furthermore, a simplified theoretical method was proposed. Comparison between experimental failure loads and theoretical predictions revealed differences within 20%, indicating satisfactory reliability of the proposed method.

Comparative study on the impact behaviors of CFWST columns reinforced with steel spiral and tube

To obtain superior corrosion resistance and impact resistance, as well as good economic benefits, two new types of composite structure called as steel tube internally-reinforced concrete-filled weathering steel tube (STRCFWST) and steel spiral internally-reinforced concrete-filled weathering steel (SSRCFWST) columns are proposed and compared in terms of their impact resistance in this paper. Eleven impact tests were conducted and three parameters comprising steel spiral diameter, wall thicknesses of outer and inner steel tube were considered to evaluate their influences on the lateral impact behaviors. Results show the presence of inner steel tube and reinforcement cage significantly enhances the impact resistance while slightly decreases the energy absorption capacity. Increasing inner steel tube wall thickness helps to improve the impact resistance, however the contribution is not so good as that produced by increasing the outer steel tube wall thickness, whilst varying steel spiral diameter almost has no impact. Numerical models were developed by ABAQUS/Explicit and verified via the test, based on which the full-range behaviors of STRCFWST, SSRCFWST and unreinforced concrete-filled weathering steel tube (CFWST) columns under impact loading were compared and discussed. It is demonstrated that steel tube and reinforcement cage provide little confinement on concrete infill under impact. With the same internal steel ratio, inner steel tube makes a greater contribution to sectional bending moment resistance and energy absorption as compared to the reinforcement cage.

A robot-assisted tracheal intubation system based on a soft actuator?

Tracheal intubation is the gold standard of airway protection and constitutes a pivotal life-saving technique frequently employed in emergency medical interventions. Hence, in this paper, a system is designed to execute tracheal intubation tasks automatically, offering a safer and more efficient solution, thereby alleviating the burden on physicians. The system comprises a tracheal tube with a bendable front end, a drive system, and a tip endoscope. The soft actuator provides two degrees of freedom for precise orientation. It is fabricated with varying-hardness silicone and reinforced with fibers and spiral steel wire for flexibility and safety. The hydraulic actuation system and tube feeding mechanism enable controlled bending and delivery. Object detection of key anatomical features guides the robotic arm and soft actuator. The control strategy involves visual servo control for coordinated robotic arm and soft actuator movements, ensuring accurate and safe tracheal intubation. The kinematics of the soft actuator were established using a constant curvature model, allowing simulation of its workspace. Through experiments, the actuator is capable of 90° bending as well as 20° deflection on the left and right sides. The maximum insertion force of the tube is 2N. Autonomous tracheal intubation experiments on a training manikin were successful in all 10 trials, with an average insertion time of 45.6s. Experimental validation on the manikin demonstrated that the robot tracheal intubation system based on a soft actuator was able to perform safe, stable, and automated tracheal intubation. In summary, this paper proposed a safe and automated robot-assisted tracheal intubation system based on a soft actuator, showing considerable potential for clinical applications.

Axial compressive behavior of spiral stirrup-reinforced concrete-filled cold-formed steel built-up box stub columns

This paper aims to explore the enhancement effect of spiral stirrup on concrete-filled cold-formed steel built-up box (CF-CFB) columns. Herein, four specimens were designed and fabricated to explore the impact of the spiral stirrup and riveted form on the axial compression performance of CF-CFB columns. Then, the finite element model of spiral stirrup-reinforced concrete-filled cold-formed steel built-up box (RCF-CFB) stub columns was established, and a systemic parametric investigation was conducted to explore the impact of geometric and material parameters on the compression performance of RCF-CFB stub columns. Afterwards, the analysis included an assessment of contact stress and stress distribution was conducted to uncover the confining effect. The analysis results revealed that the failure mode of the RCF-CFB column was tube buckling and concrete crush, accompanied by the spliced tube separating at the buckling area. The built-in reinforcement could significantly improve the performance of the built-up column, while riveted forms of spliced steel tubes had little effect. Furthermore, the axial bearing capacity of the RCF-CFB column would increase with the enhancement in steel yield strength, concrete strength, tube thickness, and longitudinal bar diameter. Finally, a calculating method to predict the axial bearing capacity of the RCF-CFB column was proposed, and the applicability of the method was demonstrated by comparison with experimental and FE data.

Experimental Study on the Mechanical Properties of Recycled Spiral Steel Fiber-Reinforced Rubber Concrete

Recycled rubber (RR) and recycled spiral steel fiber (RSSF) were added to plain concrete (PC) to prepare recycled spiral steel fiber rubber concrete (SSFRC) with matrix strengths of C30, C40, and C50. Strength tests on the PC, rubber concrete (RC), and SSFRC were carried out, including the cube compressive strength, splitting tensile strength, and flexural strength. The effects of RSSF and RR on the mechanical properties of concrete were analyzed. Simultaneously, the stress–strain curve of the SSFRC was obtained through axial compressive testing, and the toughness of SSFRC was evaluated by three indexes: the tensile compression ratio, bending compression ratio, and toughness index. The results show that adding RR to PC results in a decrease in the mechanical properties of concrete with different matrix strengths, and the addition of RSSF can make up for the strength loss of the rubber. The mechanical strength of SSFRC with different matrix strengths increased first and then decreased with the increase in RSSF content. The cubic compressive strength reached its peak value when the content of RSSF was 1%, and the splitting tensile strength and flexural strength reach their peak values when the content of RSSF was 1.5%. RSSF works best with rubber particles at the right dosage to further increase the toughness of the concrete. When the rubber content is 10%, and the RSSF content is 1.5%, the mechanical strength enhancement effect of SSFRC is at its best, and the toughness is also at its best.

Hybrid machine learning model and predictive equations for compressive stress-strain constitutive modelling of confined ultra-high-performance concrete (UHPC) with normal-strength steel and high-strength steel spirals

Stress-strain constitutive model for confined ultra-high-performance concrete (UHPC) plays a pivotal role in the design and modelling of UHPC structures. However, while extensive research exists on the stress-strain responses of unconfined UHPC, a notable dearth of studies focuses on the stress-strain constitutive model for confined UHPC. Accordingly, this study introduces a novel hybrid machine learning (ML)-based stress-strain constitutive model for UHPC confined with normal-strength steel (NSS) or high-strength steel (HSS) spirals. Given the limited experimental data available, a numerical model was developed and validated against experimental results of confined UHPC. Subsequently, it was employed to generate a comprehensive dataset of confined UHPC stress-strain responses, which were then used to train the hybrid ML model. Hyperparameters of the model are subsequently optimized using Optuna along with a cross-validation technique. The optimized hybrid ML model exhibited exceptional accuracy in predicting the stress-strain response of confined UHPC with NSS or HSS spirals, as demonstrated by high coefficients of determination (R2) values ranging from 0.905 to 0.999 and low error metrics across varying stress levels and datasets. Moreover, the capability of the model to simultaneously predict both stress and strain responses was further validated through canonical correlation analysis (CCA). The results of the analysis demonstrated robust predictive performance of the model, with high CCA scores that ranged between 93.3% and 99.4%. To facilitate the practical implementation of the model, an end-to-end interactive software tool is developed. In addition, this study proposes predictive equations for the peak and ultimate stress-strain responses of confined UHPC. The evaluation of the developed predictive equations demonstrates their efficacy in accurately predicting the stress-strain responses of confined UHPC, as evidenced by the high R2 values, which ranged from 83–91%.

An Automatic Welding Robot for the Roof of Spiral Steel Silo

A spiral steel silo has become the preferred choice for building steel silos because of its short construction period, low cost, and high strength. Owing to the harsh outdoor welding conditions of the spiral steel silo and the high risk of manual welding, in this paper, an automatic welding robot is proposed, and its key technology is studied. The welding process parameters consisted of welding voltage, current, and the distance between the conductive nozzle and the base material, which were determined through experiments. The key technology of seam tracking on the roof of a spiral steel silo was studied. Finally, a weld bead tracking experiment and prototype welding experiment were carried out. The results suggest that the prototype can track the weld bead stably and accurately, and the welding effect can meet welding process requirements when the welding current is 200 A, the voltage is 20 V, and the distance between the welding nozzle and the base material is 12 mm.

Fatigue Crack Growth Evaluation of Pipeline Steels and Girth Welds

Abstract Fatigue test specimens were prepared and tested with an API 5 L X70 spiral welded pipe steel and girth weld. For a few selected specimens, two unloading compliance techniques (elastic compliance and back-face strain compliance) were applied simultaneously to a single specimen for direct comparisons of in situ crack size estimation. This paper also includes fatigue crack growth rate (FCGR) data of other pipe steels and welds available in the literature. It was observed that most FCGR curves of pipeline steels (X65–X100) remained within the BS 7910 mean and upper bound design curves in the Paris region. It was noted that the FCGR of austenitic stainless pipe steel and girth weld obtained from Arora et al. (2014), “Fatigue Crack Growth Studies on Narrow Gap Pipe Welds of Austenitic Stainless Steel Material,” Procedia Eng., 86, pp. 203–208) showed a very superior fatigue property.

Experimental and numerical investigations on eccentric compression behavior of square CFST columns with inner spiral stirrup

In this paper, eccentric compression behavior of square CFST columns with inner spiral stirrup was investigated. First, an eccentric compression test was conducted on 18 CFST columns with influential variables of the spiral pitch, the diameter-width ratio, the slenderness ratio, the eccentricity ratio, the longitudinal rebar ratio and the tube thickness. Test results showed that the spiral stirrup avoided the rapid loss of bearing capacity caused by excessive local deformation of the CFST column under eccentric compression. The performance of CFST columns with inner spiral stirrup can be improved by reducing the spiral pitch and increasing the diameter-width ratio. With the increase of the slenderness ratio and the eccentricity ratio, the ability of spiral stirrup to improve the eccentric compression behavior of CFST columns was significantly weakened. Before the peak load, the strain distribution of the steel tube along the section depth basically conformed to the plane section assumption, and the maximum strain of the spiral stirrup appeared near the corner of the steel tube in the compression zone. Furthermore, a parameter study using the fiber model method was performed to investigate the influence of steel distribution, including a spiral stirrup, longitudinal rebar and steel tube, on the bearing capacity of columns. It is found that the order of contribution efficiency of increasing the steel ratio of each component to the eccentric bearing capacity was spiral stirrup > steel tube > longitudinal rebar. Moreover, a finite element model was established for further analysis of the failure process. Finally, the recommendations on steel distribution and the formulas for calculating the eccentric load-carrying capacity were provided.

Experimental and numerical investigations on seismic behavior of spiral stirrup-confined square concrete-filled steel tubular columns

To investigate the seismic behavior of spiral stirrup-confined square concrete-filled steel tubular (SS-CFST) columns, ten square CFST columns, including eight SS-CFST columns and two ordinary CFST columns were experimentally studied through the cyclic loading tests. The critical test variables included the axial load ratio, spiral pitch, and longitudinal reinforcement ratio. First, the seismic behavior of the SS-CFST columns was herein discussed and clarified based on the failure modes, hysteretic response, skeleton curves, load-bearing capacity, strength and stiffness degradation, ductility and energy dissipation. Then, a total of 53 full-scale finite element (FE) models were established for parameter analysis of SS-CFST columns. The experimental and numerical results showed that the expansion deformation, necking and fracture of spiral stirrup were not formed when the SS-CFST columns were damaged, but the confinement effect effectively reduced the concrete fragmentation, alleviated the buckling of steel tube and longitudinal rebar, and limited the expansion of internal cracks. In the range of n=0.20–0.50, the ductility of SS-CFST columns significantly decreased with an increase in the axial load ratio, despite the stable bearing capacity and good energy dissipation of the columns. Moreover, unlike SS-CFST columns with high axial load ratio, spiral stirrup can only slightly improve the load-bearing capacity of SS-CFST columns with small axial load ratio (nt≤0.35). Compared with ordinary CFST columns, the strength degradation, ductility, collapse resistance, and energy dissipation of SS-CFST columns were significantly improved except for lateral stiffness, and the ultimate drift ratio of all SS-CFST columns in the test was greater than 3.00%. Furthermore, for SS-CFST columns, increasing the longitudinal reinforcement ratio can improve the lateral load-bearing capacity and stiffness. Finally, the formulas established in this paper can be adopted to assess the lateral load-bearing capacity of SS-CFST columns.

Study on Multiphase Flow Characteristics During RH Refining Process Affected by Nonradial Arrangement of Gas‐Blowing Nozzle

Bath stirring, degassing, and decarburization in steel refining are strongly related to flow behaviors. The bubble plume produced in Ruhrstahl–Heraeus (RH) up‐snorkel plays an important role during refining, since it not only acts as a bubble pump, but also provides the reaction interface. Herein, it is aimed to form a new flow pattern in the up‐snorkel by using a nonradially arranged gas‐injection nozzle to enhance the 260 ton RH refining process. The results show that an upward spiral steel flow is produced, when nonradial gas‐injection nozzles are used in the up‐snorkel. Meanwhile, some bubbles moved toward the center region of the up‐snorkel, which may be caused by the centripetal effect in a rotational steel flow. This leads to a more uniform bubble distribution on the cross section of the snorkel, compared to that of the conventional case. Specifically, the circulation flow rate is increased by about 18.0%, and the mixing time are shortened by about 26.2% (criteria of ±5%), compared to that of the conventional case. In addition, the inclusion removal rate is increased by 0.5%, 4.8%, and 11.3% for the inclusion size of 20, 50, and 100 μm, respectively, compared to the conventional radial nozzle case.

Axial compressive behavior of circular composite columns with external confinement

With the advance of externally confined composite columns, a generic model that can predict the ultimate axial compressive strength of both circular concrete-filled steel tube (CFST) and concrete-filled double skin steel tubes (CFDST) short columns with external confinement is very attractive. For this purpose, a rich experiment database of composite columns is assembled, guides to build up this database are outlined, and its limitations are also summarized. Based on some fundamental considerations, a simple formula for estimating ultimate axial compression of circular composite short columns is proposed first. The hoop and longitudinal stresses of outer and inner (if any) steel tubes are then determined by the stress analysis, from which the assumption frequently used in previous studies that the sandwiched concrete in a CFDST column is under uniform confinement is demonstrated to be unreasonable. Besides, the additional external confining pressure provided by external confinement in the form of steel spirals, rings, jackets, or tie bars is thoroughly investigated. Further, to comprehend the triaxial strength of infilled concrete in both CFST and CFDST columns, a novel concept of equivalent confining stress that can reflect both uniform and non-uniform confinement effects is defined, with which a modified Power-law failure criterion is established. Model validations illustrate that this generic model can reasonably estimate the strength of externally confined CFST and CFDST columns. Although it currently slightly underestimates the strength of ring-enhanced CFDST columns, this limitation can be easily overcome by recalibrating some coefficients without rebuilding the proposed framework.

Comprehensive study of compressive behavior of CFST columns with confinements and stiffeners

This paper presents a performance study of circular-shaped short steel-concrete-filled columns (CFST) with external confinement and internal stiffening under axial loading conditions. Thirty specimens of different types of HST and CFST columns were fabricated and tested. The variables studied included concrete type, inner wall design with/without vertical strips, and shear studs. The failure pattern, deflection, axial strain, hoop strain, types of lateral confinement and their combined effects, and the effect of longitudinal strips were closely examined. The results showed that using external confinement, such as spiral or ring-type steel rods, and internal stiffening, such as vertical strips and shear studs, improved the axial load-carrying capacity and stiffness of the CFST columns. The theoretical and empirical findings of the axial load-carrying ability of CFST columns were found to be in excellent agreement with experimental results. Reliability analysis was carried out, and its results signified that the CFST column specimens with studs and stiffeners were highly reliable.

Multi-scale coupling numerical modeling of metallic strip flexible pipe during reel-lay process

Complex plastic deformation and local buckling may occur due to the nonlinear contact between the pipe and drum in the offshore pipeline laying by reel-lay method. In this paper, material performance tests are carried out to obtain the nonlinear stress-strain constitutive models for high density polyethylene (HDPE) material and steel strip. Meanwhile, full-scale tensile tests are also conducted to acquire the tension-strain correlation of metallic strip flexible pipe (MSFP). Then, shell element and solid element are combined to establish an ABAQUS multi-scale finite element model (FEM) for MSFP under the coiled laying condition. The proposed multi-scale FEM consists of three components, i.e. two simplified components and one fine component, which could accurately and efficiently simulate the mechanical properties of flexible pipe under the coiled laying condition. The results indicate that: due to the radial extrusion restriction of spiral steel strips, the Mises stress distribution of inner HDPE layer shows a more uniform spiral strip distribution than outer HDPE layer; the most dangerous condition for MSFP may be when it is just partially wound up on the drum; the effect of friction coefficient on the spiral steel strips seems obviously larger than the effects of traction force and drum diameter.

Seismic behavior of wall-type spiral stirrups-confined RC column to steel beam joint

This study proposes a new interior diaphragm joint between wall-type reinforced concrete column with high-strength spiral stirrups and steel beams, and the quasi-static test was conducted to investigate the seismic performance of the new joint under cyclic lateral force. Finite element model (FEM) simulation was carried out using the software ABAQUS, and the correctness of the FEM was verified by the results of the test. Additionally, the effect of parameters including the strength of concrete, thickness of the beam flange, interior diaphragm, joint flange, and joint web on the seismic performances of the joint was analyzed. Based on the parametric analysis and existing codes, a shear capacity formula was determined with the consideration of the shear capacity of the joint web and flange, and concrete. The comparison between the calculated and FEM results indicates that this formula could be regarded as an accurate calculation method for the shear-bearing capacity of different joint types in engineering design.

Static Stiffness Properties of High Load Capacity Non-Pneumatic Tires with Different Tread Structures

A high load capacity non-pneumatic tire (HC tire) was designed and manufactured to solve the problems of air leakage, puncture, blowout, shoulder void, and delamination, which occur in traditional high load capacity tires, as well as significantly increase the unit load of tires. Experiments and numerical simulations were conducted to investigate the static stiffness properties of the HC tire. Additionally, the manufacturing process of the tire was highlighted. The tire mainly comprised polyurethane and silicon manganese steel, and a ‘π’-shaped support substructure was adopted. The tread structure was made up of a built-in spiral steel ring and a non-steel ring. The uniaxial tensile mechanical properties of the used metal and elastomer materials were tested, and the linear elastic constitutive model and Marlow constitutive model, respectively, were used to describe their mechanical characteristics. The stiffness properties of the HC tire, including torsional, longitudinal, vertical, and lateral stiffnesses, were evaluated using a tire comprehensive stiffness tester. Nonlinear finite element models of the HC tire were established, and their accuracies were verified through vertical stiffness tests. The stiffness properties of the HC tire in other directions were simulated as well. An in-depth comparative analysis of the simulation and experimental data was performed. The results demonstrated that the unit load of the unreinforced HC tire was 2.972 times and 1.615 times higher than that of the solid tire and pneumatic tire, respectively. The spiral steel ring embedded in the tread increased the vertical and longitudinal stiffness but reduced the torsional stiffness of the HC tire, thus reversing the variation trend of the lateral stiffness at the 0° and 5° test points. The findings can serve as a reference for theoretical research on, and the structural optimization of, non-pneumatic tires with a high load capacity.

Design and testing of a mechanized brush-screen cooperative vibration harvester for mudflat-buried shellfish based on the discrete element method

IntroductionTo enhance the application of mechanized harvesting and supplement research on harvesting theory in mudflat-buried shellfish harvesting in China, a brush-screen cooperative mudflat-buried shellfish vibration harvester was designed.MethodsThe harvester is primarily composed of a crank rocker double-layer vibrating screen, two stage rolling brush, and a conveyor chain. White clams (Mactra veneriformis) cultured in mudflats were used as the research objects in this paper, and the mechanics and motion states of the shellfish on the vibrating screen were analyzed. The shellfish harvesting simulation response surface experiments based on the discrete element method (DEM) were conducted to analyze the influence of the main operating parameters on the quantity of shellfish harvested.ResultsThe results revealed that the number of shellfish harvested was significantly influenced (p< 0.01) by vibrating screen amplitude, first-stage spiral rolling stainless steel brush rotation rate, and harvester travel speed. The optimal combination of key parameters was 1.4 mm, 40 rpm, and 10 m/min, respectively. With these values, the projected shellfish crushing rate was 2.82% and the shellfish harvesting efficiency was 125 pieces/m2. The equipment was then manufactured and the shellfish harvesting verification test was performed under the same operating parameters as the simulation. Test results indicated that the harvesting efficiency of the equipment was 114 pieces/m2 and the shellfish crushing rate was 6.97%.DiscussionThe shellfish harvesting work could be completed by the equipment effectively and with low loss. The results of this study provide a theoretical reference for a novel mechanized method of harvesting mudflat-buried shellfish.

Effect of high-strength steel spirals on the seismic behavior of square concrete-filled steel tubular columns under high axial load ratio

Ductility of square concrete filled steel tubular (CFST) columns is generally significantly lower than that of circular ones, especially when they are under high level of axial loads. Many previous studies suggested that adding internal steel spiral stirrups is an effective measure to improve ductility of square CFST columns. To investigate the effect of high-strength steel (HSS) spirals on the seismic behavior of the HSS spiral-confined CFST (HSS-CFST) columns under high axial load ratio, 15 square CFST columns, including 3 conventional CFST columns without internal steel spirals, 3 normal-strength steel (NSS) spiral-confined CFST (NSS-CFST) columns, and 9 HSS-CFST columns were experimentally studied through the cyclic loading tests. The critical test parameters included the steel spiral pitch and axial load ratio. Final failure modes, hysteretic response, skeleton curves, strain distributions, ductility, energy dissipation capacity, and stiffness degradation of the specimens were investigated in detail. The experimental results indicated that (i) apparent outwardly local bucking of the steel tube and core concrete crushing were observed for all specimens in the plastic hinge regions at the ultimate state; (ii) adding both the NSS and HSS spirals would beneficial in improving the hysteretic behavior and energy dissipation capacity of square CFST columns, but contributions to these improvements made by the HSS spirals were more significant than that of the NSS ones; (iii) the increase of axial load ratio and internal steel spiral pitch would impair the load-carrying capability and ultimate deformation ability of square CFST columns; (iv) ductility of the NSS-CFST and HSS-CFST columns could be improved as the increased of spiral volume ratio and the ductility enhancement was more pronounced in the HSS-CFST columns; and (v) the internal steel spirals were helpful in delaying the stiffness degradation rate of square CFST columns, particularly for those specimens under a high axial load ratio of 0.8.

Spiral-based confinement in slabs for the seismic performance enhancement of steel-concrete composite frames

The seismic performance analysis of steel-concrete composite frames involves, as known, the interaction of several load-bearing components that should be properly designed, with multiple geometrical and mechanical parameters to account. Practical recommendations are given by the Eurocode 8 – Annex C for the optimal detailing of transversal rebars, so as to ensure the activation of conventional resisting mechanisms. In this paper, the attention is focused on the analysis of effects and benefits due to a novel confinement solution for the reinforced concrete (RC) slab. The intervention is based on the use of diagonal steel spirals, that are expected to enforce the improve the overall compressive response of the RC slab, thanks to the activation of an optimized strut-and-tie resisting mechanism. The final expectation is to first increase the resistance capacity of the slab, that can thus transfer higher compressive actions under seismic loads. Further, as shown, the same resisting mechanism can be beneficial for the yielding of steel rebars, depending on the final detailing of components, and thus possibly improve the ductility of the system To this aim, a refined Finite Element (FE) numerical analysis is carried out for several configurations of technical interest. The in-plane compressive behaviour and the activation of resisting mechanisms is explored for several spiral-confined slabs, based on various arrangements. Major advantage is take from literature experimental data on RC slabs, that are further investigated by introducing the examined confinement technique. As shown, once the spirals are optimally placed into the slab, the strength and ductility parameters of the concrete struts can be efficiently improved, with marked benefits for the overall resisting mechanisms of the slab, and thus for steelcomposite frames as a whole.