Cantilever Members Research Articles

Lateral impact resistance of CFST cantilever members stiffened with encased I-shaped CFRP

The lateral impact resistance of cantilever concrete-filled steel tubular (CFST) members stiffened with encased I-shaped carbon fiber reinforced plastic (CFRP) profiles subjected to lateral impact is investigated in this paper. The impact tests are performed on four specimens to examine the dynamic response. Finite element analysis models are established and verified against tested results. Baseline simulations are also created using the validated models to further analyze the damage pattern and energy dissipation mechanism of each component in the impact events. It is found that compared with traditional CFST members, the new composite members have higher peak impact force, lower dynamic displacement, and larger energy dissipation capacity. Additionally, the effects of design parameters on the impact performance are evaluated by parametric analyses, and the results provide valuable suggestions for developing design guidance.

Lateral impact resistance of full-scale concrete-filled weathering steel tube columns

This paper conducted lateral impact tests on 10 concrete-filled weathering steel tubular (CFWST) columns and studied the effect of prestressing on their resistance to lateral impact. The results indicate that by using prestressed cantilever members, the impact resistance of the column can be significantly improved. This is mainly due to the reduction of tensile stress level in the steel tube at the fixed end of the cantilever column and of the overall plastic deformation of the member, which is achieved through the application of prestress. Furthermore, the test process was also simulated numerically. Based on verifying the correctness of the numerical simulation, the parameters of the full-scale model are analyzed. The impact resistance of the model was evaluated by considering various factors such as impact angle, impact point height ratio, prestress ratio, width-thickness ratio, slenderness ratio, and mass ratio. Based on these analyses, empirical formulas for the lateral ultimate displacement and bending moment of the cantilever members were derived. Particularly, considering the difference in yield strength between tension and compression sides, the theoretical calculation of plastic limit bending moment of concrete-filled square steel tubular members is modified. Additionally, the damage level of the component is defined, and the damage limit value of the concrete-filled steel tubular cantilever column is given based on the different damage grades. On this basis, considering the bending bearing capacity and displacement response of the component, an impact resistance design approach based on the performance of the component is proposed.

Experimental Investigation on Shear Capacity of Steel-Fiber-Reinforced High-Strength Concrete Corbels.

As short cantilever members, corbels are mainly used to transfer eccentric loads to columns. Because of the discontinuity of load and geometric structure, corbels cannot be analyzed and designed using the method based on beam theory. Nine steel-fiber-reinforced high-strength concrete (SFRHSC) corbels were tested. The width of the corbels was 200 mm, the cross-section height of the corbel column was 450 mm, and the cantilever end height was 200 mm. The shear span/depth ratios considered were 0.2, 0.3, and 0.4; the longitudinal reinforcement ratios were 0.55%, 0.75%, and 0.98%; the stirrup reinforcement ratios were 0.39%, 0.52%, and 0.785%; and the steel fiber volume ratios were 0, 0.75%, and 1.5%. According to the test results, this paper discusses the failure process and failure mode of corbel specimens with a small shear span/depth ratio and analyzes the effects of variables such as shear span/depth ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio, and steel fiber volume content on the shear capacity of corbels. The shear capacity of corbels is significantly affected by the shear span/depth ratio, followed by the longitudinal reinforcement ratio and the stirrup reinforcement ratio. Moreover, it is shown that steel fibers have little impact on the failure mode and ultimate load of corbels, but can enhance the crack resistance of corbels. In addition, the bearing capacities of these corbels were calculated by Chinese code GB 50010-2010 and further compared with ACI 318-19 code, EN 1992-1-1:2004 code, and CSA A23.3-19 code, which adopt the strut-and-tie model. The results indicate that the calculation results by the empirical formula in the Chinese code are close to the corresponding test results, while the calculation method based on the strut-and-tie model of a clear mechanical concept yields conservative results, and hence the related parameter values must be further modified.

Experimental investigation on cantilever square CFST columns under lateral continuous impact loads

Concrete-filled steel tube (CFST) columns can be used in passive flexible protective engineering to improve the bearing capacity of the overall protective system. This paper conducted the lateral continuous impact resistance of cantilever square weathering concrete-filled steel tube (WCFST) columns and compared it with that of the normal CFST. Considering the effect of steel tube wall thickness and prestress on the lateral impact resistance of such components, a total of 10 specimens were subjected to impact tests. The damage form and failure mode of each member were studied in detail, and the effects of the different impact mass and the height of the impact point were considered. The dynamic strain, displacement, and acceleration of each member under different impact loads were analyzed and compared. It was found that tested members show local damage at the impact point, bent failure through whole members, and bulged or fractured at the root. Slippage occurs between the internal concrete and the steel pipe wall of the member without prestressing, and this phenomenon always occurred at the second impact. Results show that when the height of the impact point of members is 0.30 h, the position of the peak displacement point is 0.76 h, where h stands for column height. The application of prestressing can significantly reduce the dynamic strain, displacement, and acceleration of members. Under the same circumstances, applying to the prestress of cantilever members can control the final deformation of it more than increasing the wall thickness. Moreover, the smaller the wall thickness of the component, the better the effect of applying to prestress to control the plastic displacement. The final cumulative plastic displacement of the member is positively correlated with its stiffness degradation after each impact.

Structural Safety Analysis of Cantilever External Shading Components of Buildings under Extreme Wind Environment

The high intensity of solar radiation and long sunshine time in the Turpan area lead to the necessity of sunshade construction. Sunshade components can effectively block direct solar radiation and the secondary heating of buildings. Through the analysis of the importance and sensitivity of sunshade components, it was found that the importance of sunshade components accounts for the largest proportion of multi-parameters, and the sensitivity of sunshade components accounts for about 60% of the total. At the same time, the change in sunshade length has an important influence on the proportion of air conditioning energy consumption and space comfort when the sunshade length reached the 0.6 m–0.8 m range. The energy consumption curve of air conditioning no longer decreased and tended to be horizontal, which showed that a sunshade could effectively reduce the energy consumption of air conditioning, while the PMV comfort curve gradually increased and tended to be horizontal, indicating that a sunshade could effectively improve indoor comfort; therefore, a sunshade could reduce direct solar radiation, reduce the energy consumption of air conditioning and improve indoor thermal comfort. In view of the extremely harsh climate characteristics of Turpan, although Turpan needs to carry out shading design, as a typical wind-sensitive component, the structural safety of the visor under the action of an extreme wind environment is the primary focus of designers. The design requires wind loads as control loads. Based on the ANSYS Workbench platform, this study used the fluid–structure coupling technology to calculate and solve for the wind load stress and strain of a horizontal sunshade and a vertical sunshade in a cantilevered external sunshade of different buildings orientations. In this study, by solving for the maximum principal stress and maximum principal elastic strain under 10 working conditions, the results showed that the maximum principal stress of the sun visor under all working conditions was 0.39 MPa, which is much smaller than the tensile strength of C25 concrete. The calculated maximum principal elastic strain of the sun visor was 0.12 × 10−4, which is much smaller than the maximum strain value of concrete. Therefore, the wind load under this research condition had no great influence on the structural safety of the concrete sunshade, which proves the structural feasibility of the building sunshade member in the Turpan area, and provides a reference for the future practical engineering of cantilever members in the Turpan area.

Physical modelling of reinforced concrete at a 1:40 scale using additively manufactured reinforcement cages

AbstractGlobal level assumptions of numerical models have received relatively less attention, but have been indicated to be a major source of error in numerical modeling of Reinforced Concrete (RC) structures. In parallel, it has been stated that a statistical approach involving many virgin specimens and ground motions is necessary for model validation. Such an approach would require very small‐scale testing. Then, the reinforcement fabrication becomes a major issue. This paper proposes using additive manufacturing to fabricate the reinforcement cage. It presents the results from cyclic tests on 1:40 RC cantilever members. The cages were manufactured using an SLM 3D printer able to print rebars with submillimeter diameters. Different longitudinal and transverse reinforcement configurations were tested. A numerical model using existing Opensees elements was built and its parameters were calibrated against material level small‐scale tests. It captured the cyclic response of the RC members with a reasonable accuracy. The cyclic behavior of the RC members resembles the behavior of full‐scale RC members indicating that such small‐scale specimens can be used for the statistical validation of the global level assumptions of numerical models.

Cross-sectional bending strength of steel Elliptical-Hollow-Sections (EHSs) based on Equivalent-Resistance-Capacity-Method (ERCM)

An expression for cross-sectional bending capacity prediction curve is proposed in this study based on the Direct-Strength-Method (DSM) approach using a comprehensive data from the literature on structural carbon steel Circular-Hollow-Sections (CHSs). Later, according to the Equivalent-Resistance-Capacity-Method (ERCM), improved empirical expressions for the equivalent CHS diameter of Elliptical-Hollow-Section (EHS) are derived using the proposed CHS bending capacity prediction curve and the data of EHSs from the literature. A unified set of cross-section slenderness limits for assessing the CHS and EHS members under bending is proposed. Also, the proposed expression for the bending resistance curve based on DSM is transformed into the generalized form of the traditional cylindrical shell buckling capacity curve as a practical solution in harmony with the newly introduced Reference-Resistance-Design (RRD) guidelines. Finally, the behaviour of EHS cantilever members under cyclic bending is assessed in terms of cyclic moment resistance and rotation capacities based on the authors' previous study.

Interfacial stresses in reinforced concrete cantilever members strengthened with fibre-reinforced polymer laminates

Fibre-reinforced polymers have been increasingly used to strengthen reinforced concrete structures. However, premature brittle debonding failures may occur at the ends of externally bonded fibre-reinforced polymer laminates due to interfacial stress concentrations caused by stiffness imbalances. Although many studies exist on fibre-reinforced polymer-strengthened simply supported beams and slabs, the interfacial stress distributions in fibre-reinforced polymer-strengthened cantilever members are very different from those in simply supported members. Based on the assumptions of linear elasticity, deformation compatibility and static equilibrium conditions, the interfacial stresses in fibre-reinforced polymer-strengthened reinforced concrete cantilever members under arbitrary linear distributed loads were analysed. In particular, closed-form solutions were obtained to calculate the interfacial stresses under either a uniformly distributed load or a single concentrated load located at the overhanging end of the cantilever member. Existing test results on cantilever slabs strengthened by carbon fibre–reinforced polymer sheets were used to verify the model. According to the parametric analysis, the maximum interfacial stresses can be reduced by decreasing the fibre-reinforced polymer thickness, increasing the fibre-reinforced polymer bonding length and increasing the adhesive layer thickness, and by using less rigid fibre-reinforced polymer laminates with high tensile strengths. These results are useful for engineers seeking to optimize strengthening design parameters and implement reliable debonding prevention measures.

Convergence of the Rayleigh–Ritz Method for buckling analysis of arbitrarily configured I-section beam–columns

Design of the slender members requires calculation of buckling loads in addition to stress and deflection demand/capacity ratios. The Rayleigh–Ritz Method, which allows one to present approximate closed-form solutions for certain cases, is one of the simplest methods for this purpose. This study evaluates the buckling analysis of the I-section prismatic beam–columns with the Rayleigh–Ritz Method in detail. First, algebraic, trigonometric, and exponential trial functions for various restraint configurations are derived carefully in finite series form. Then, an iterative procedure to calculate buckling loads and modes is described. Finally, a software is developed with Mathematica and the sensitivity of the results and performance to trial function type and the number of terms is investigated over 1000 computer-generated numerical examples, which include doubly and singly symmetric sections, simply supported and cantilever members, intermediate torsional and lateral restraints, transversal concentrated and distributed loads acting above/below the shear center, and axial loads.

Experimental and Numerical Assessment of Corbels Designed Based on Strut-and-Tie Provisions

AbstractReinforced concrete (RC) corbels are short cantilever members that are used to transfer eccentric loads into columns or walls. Due to discontinuity in load and geometry, RC corbels cannot b...

Cyclic behavior of UHPFRC flexural members reinforced with high-strength steel rebar

Ultra-high performance fiber reinforced concrete (UHPFRC) is a unique class of fiber reinforced concrete. It features an ultra-high compressive strength and a ductile, tensile strain hardening behavior accompanied by multiple narrow cracking. The cyclic flexural performance of UHPFRC structural beams reinforced with high-strength steel with a specified yielding strength of 680MPa is experimentally investigated in this study. Six cantilever beams are prepared and tested under displacement reversals. The experimental variables include the reinforcement ratio of the high-strength longitudinal rebar and the amount, location, and length of steel fibers in the beams. The intermediate and ultimate behaviors of these cantilever members are discussed using multiple performance parameters, including strength capacity, flexural ductility, failure pattern, hysteretic response, energy dissipation capacity, and stiffness retention. The results show that UHPFRC beams reinforced with high-strength steel are able to show satisfactory cyclic flexural performance prior to failure. The addition of steel fibers substantially enhances the damage tolerance ability of the high-strength beams, even when the fibers are selectively used only in the top and bottom beam sections. The proposed composite of UHPFRC and high-strength steel rebar not only takes advantage of the ultra-high mechanical properties of both materials, but also resolves the issue of potential premature failure patterns associated with high-strength concrete and high-strength steel rebar.

Shear–flexural interaction for prestressed self-consolidating concrete beams

This work validated a model of shear–flexure interaction for prestressed self-consolidating concrete beams with varied shear span-to-depth ratios, which were tested under four-point bending as part of this work. The interaction between flexure and shear was introduced by a panel element’s biaxial behavior in a modified fiber element formulation. Two different assumptions were considered for the interaction model implementation: (i) zero transverse normal stress perpendicular to the beam axis in any cross section, and (ii) a prescribed transverse normal strain profile along the beam based on the model calibrated for cantilever members. The interaction model with a prescribed transverse strain profile and with a consideration of flexure-induced deformations had better predictions of capacity and deformation for the tested beams, as well as the transverse normal strain profile, compared to the other models.

Cantilever driven transduction apparatus

An electromechanical transducer which provides orthogonal translated motion to a piston through an attached lever arm connected to and driven by at least two electromechanical cantilever members, mounted on a separate inertial tail mass, and which under full array loading conditions provide a reduced resonance frequency that yields velocity control in the vicinity of that resonance.

Towards error‐free hybrid simulation using mixed variables

AbstractTwo procedures are developed and implemented in a hybrid simulation system (HSS) with the aim of enhancing the accuracy and reliability of the online, i.e. pseudo‐dynamic, test results. The first procedure aims at correcting the experimental systematic error in executing the displacement command signal. The error is calculated as the difference between command and feedback signals and correlated to the actuator velocity using the least‐squares method. A feed‐forward error compensation scheme is devised leading to a more accurate execution of the test. The second procedure employs mixed variables with mode switching between displacement and force controls. The newly derived force control algorithm is evaluated using a parametric study to assess its stability and accuracy. The implementation of the mixed variables procedure is designed to adopt force control for high stiffness states of the structural response and displacement control otherwise, where the resolution of the involved instruments may favour this type of mixed control. A simple pseudo‐dynamic experiment of steel cantilever members is used to validate the HSS. Moreover, two experiments as application examples for the two developed procedures are presented. The two experiments focus on the seismic response of (a) timber shear walls and (b) reinforced concrete frames with and without unreinforced masonry infill wall. Copyright © 2007 John Wiley & Sons, Ltd.

Built-up battened columns under lateral cyclic loading

Built-up members with battens designed for typical 2–2.5% of axial load may not behave satisfactorily in the presence of lateral seismic loads. Analytical evaluation of double-channel battened cantilever members designed as per the current practice, and subjected to constant axial compressive load and gradually increasing lateral load showed that the members failed to reach their expected flexural capacity due to lateral instability. The design of members was modified by changing the configuration of battens in the expected plastic-hinge region, i.e., reducing the spacing of battens in end panel by half, and designing battens for a shear demand due to moment capacity of section. The members with battens designed for moment capacity could able to reach the expected flexural strength. Five half-scale test specimens of battened members designed as per the current practice and improved design method were subjected to axial load and gradually increasing cyclic load. The specimens designed as per improved design method showed excellent performance in terms of lateral strength, lateral stiffness, moment rotation characteristics and energy dissipation capacity.

Pressures and deformations of bunker silo walls

To investigate the structural stability of horizontal silo walls, a silo (length, 27 m; width, 9.1 m) with straight panels (length, 3 m; thickness, 0.16 m; height above the floor, 2.05 m) on one side and L-shaped wall panels (length, 4 m; thickness, 0.15 m at the bottom to 0.10 m at the top; height above the foot, 1.85 m) on the other side was constructed on the experimental farm of Ghent University. Displacement, strain and pressure measurements were performed during and after filling the silo with chopped maize. The displacements of the straight and L-shaped wall panels, measured with dial gauges and linear variable displacement transducers, were much higher than those predicted from published load combinations. The maximum measured displacements were 3.5 and 13.1 mm, respectively, for the straight and L-shaped wall panels. Moreover, in contrast with the assumption of perfectly restrained panels, the measurements showed that the panels acted partially like cantilever members. Strains were measured with mechanical deformeters, fibre Bragg grating sensors and strain gauges. The majority of both displacement and strain occurred during the second half of the filling process. When full, maximum strains on the outer surface of the silo wall of −110×10 −6 [dimensionless] and −220×10 −6 [dimensionless] were measured at the lower end of the straight panel and at the lower end of the L-shaped wall panel, respectively. The influence on the displacement as well as on the strain measurements of the presence of a surcharge load acting on the silage was very small. Nevertheless, short but high pressures were registered by the load cells when a surcharge load caused by a tractor and wagon passed near the measurement panel. Beneath a filling height of 1.2 m, the load cells indicated a triangular pressure distribution. For a half-filled silo, the simplified shape of the pressure profile is a triangle with a value at the base of 9.6 h kN/m 2 , h being the filling height in m. For filling heights higher than 1.2 m, a peak value appeared at a height of 1.1 m. Beneath this height, the pressure decreased. A peak value of 23.5 kN/m 2 was measured for a completely filled silo.

Two-beam model for static analysis of mono-symmetric thin-walled cantilevers

A model for the approximate analysis of mono-symmetrical thin-walled cantilever members subjected to transverse loads is presented. It is appropriate for the analysis of uniform or varying-section members, and it can be used with widely available structural analysis computer programs. The model comprises two simple beams located on one of the principal axes of bending and on opposite sides of the shear centre of the member. It accounts for bending as well as the St Venant and warping-torsional modes of behaviour. A newly devised transition mechanism provides for complete continuity in the model where the thin-walled member changes section. This allows changes in both properties and the locations of the shear centre to be properly represented. Numerical examples comparing the proposed two-beam model with the more complex shell element model are presented. The results for displacements and rotations from the two-beam model are acceptably close to those obtained from the shell element model; the discrepancies in stresses are greater but are not excessive for many practical purposes. The model is well-suited for use by designers in the approximate static analysis of thin-walled cantilever spars and for the elevator cores of tall building structures.