Beam Moment Research Articles

Research on Mechanical Characteristics of Slope Reinforcement by Spatial Arc Crown Beam Composite Supporting Structure

To effectively optimize the mechanical behavior of a traditional anti-slide pile and reduce environmental destruction, a new method for slope reinforcement by a spatial arc crown beam composite supporting structure was proposed. First, a numerical model was validated through lab-scale model test data obtained herein, and then a full-scale numerical model was created for an in-depth understanding of the distribution regularity of displacement along the pile, the soil pressure, the crown beam stiffness, and so on. The results demonstrated that: (1) The spatial arc crown beam is simplified to a two-hinged arch, and the maximum value of the bending moment in the arc crown beam is about one-third of the straight crown beam through theoretical calculation. (2) The spatial arc crown beam redistributes the load sharing among different piles, and the extreme bending moment of other piles varies within 10% along the downhill direction except for the piles at the slope foot. (3) Bending moments are close to zero at the pile end, and the anti-slide pile can be simplified as a vertical beam with one end fixed and the other end hinged. (4) The axial force in the spatial arc crown beam is always presented as pressure, so the crown beam can make full utilization of the compression resistance of concrete. (5) The distribution characteristic of soil pressure in front of the pile at the arch foot is different from that in other positions, and the stable soil at the slope foot provides greater soil resistance for anti-piles. (6) As the crown beam stiffness is above five times the reference value, the axial force of the crown beam tends to be stable, and as the crown beam stiffness increases continually, the maximum value of My is −1013.13 kN·m, and the constraining effect of the crown beam is gradually weakened.

Physical and mechanical properties and time-varying model of concrete structures under the simulated tidal environment of the South China Sea island and reef

In view of the poorer durability of concrete structures under the tidal environment of the South China Sea island and reef, the effectiveness of durability improvement measures is studied. The deterioration test of concrete, corrosion and tensile test of rebar in concrete and bending tests of reinforced concrete beams after the simulated experiment are tested. The results show that under the simulated tidal environment of the South China Sea island and reef, with the increase of concrete strength grade and the mixing of corrosion inhibitor, the relative dynamic elastic modulus of concrete increases by 21.4% to 39.6%, the mass-loss rate of rebar decreases by 42.1% to 100%, the cracking moment of beams increases by 17.8% to 53.3%, the ultimate moments of beams increases by 1.6% to 15.5%, and the ultimate deflections of beams decreases by 7.1% to 28.6%. The mechanical properties of concrete first increase and then decrease with age, and the physical and mechanical properties of rebar decrease with age. Therefore, the mechanical properties of reinforced concrete beams will be improved briefly. In addition, the univariate quadratic polynomial time-varying model on the deterioration of corroded concrete and the power function time-varying model on the physical and mechanical properties of corroded rebar are proposed and verified. Furthermore, time-varying models of the mechanical properties of reinforced concrete beams considering concrete deterioration and rebar corrosion are also proposed and verified. This study will provide a theoretical basis and method for durability studies of South China Sea island and reef engineering.

Nonlinear analysis of Euler beams resting on a tensionless soil with arbitrary configurations

BackgroundThe nonlinear interaction between an elastic Euler beam and a tensionless soil foundation is studied. The exact analytical solutions of the nonlinear problem are rather complicated. The main difficulty is imposing compatibility conditions at lift-off points. These points are determined as a part of the solution, although being needed to get the solution itself. In the current work, semi-analytical solutions are derived using the Rayleigh–Ritz method. The principle of vanishing variation of potential energy is adopted. The solution is approximated using a set of suitable trial functions. Accurate high-order approximate analytical solutions are obtained using MAXIMA symbolic manipulator. Lift-off points are identified through an iterative procedure and compatibility conditions are satisfied automatically. The methodology is designed to accommodate arbitrary configurations for the load distribution and the beam properties.ResultsExact solutions are revised briefly to verify the semi-analytical solutions in terms of deflection, bending moment, and shear. Semi-analytical solutions for constant beam properties including various support conditions and load distributions are verified. Convergence of high-order semi-analytical solutions is illustrated for cases including one and two contact points. A parametric study is provided to illustrate the effect of soil stiffness on the contact length. The case of a finite beam with free ends is considered. The semi-analytical solutions for variable beam moment of inertia are provided and verified.ConclusionsHighly accurate semi-analytical solutions can be obtained for the problem considered using the Rayleigh–Ritz method along with a symbolic manipulator. Arbitrary load and support configurations can be modeled, and the locations of lift-off points are well predicted. The semi-analytical solutions are extremely valuable for cases of variable moment inertia since exact solutions are rather rare.

STRUCTURAL EFFICIENCY OF STEEL COMBINED TRUSSES

In this article on increasing the efficiency of steel combined structures, the tasks of rational design, regulation and control of structural parameters of elements, the use of steels with increased mechanical properties are considered. It is shown that for a six-span stiffening girder of a combined truss with elastic supports, which operates under a distributed load, the moment is 72 times smaller than the moment of a single-span beam. It is suggested to use high-strength steel for truss braces. Rationality criteria are proposed. On the basis of rationality criteria, new steel combined trusses were developed and their models were designed for stress tests. The results of experimental studies of models of combined trusses are presented. The results of experimental studies conducted on models of steel combined trusses qualitatively and quantitatively confirmed the theoretical results obtained on the basis of the proposed theory.

Numerical modeling and nonlinear analysis of semi-rigid jointed steel frames

This paper investigates the effect of semi-rigid connection, geometric nonlinearity and material nonlinearity in steel frame analysis. To study the independent and combined effects of different nonlinearities, elastic and inelastic analyses are carried out using general purpose finite element software SAP2000. Connections are modeled as rotational springs and frame as one dimensional beam element. Verification and application of the simplified numerical model developed in the present study is demonstrated by considering different examples and comparing the results of present study with those available in the published literature. Numerical alternatives, key features about modeling and necessary input parameters are discussed in detail. Rotational springs are characterized by linear, bilinear, multi-linear or nonlinear moment-rotation relationships of the connection. Results in terms of beam moment and nodal displacement are presented for both elastic and inelastic analyses. With the increase in connection flexibility, beam mid-span moments and displacements increase, but beam-end moments decrease. It is observed that the influence of connection nonlinearity dominates over material and geometric nonlinearities.

Flexural behaviour of wood beams strengthened by flax-glass hybrid FRP subjected to hygrothermal and weathering exposures

This paper addressed the flexural behaviour (i.e., maximum load, ductility index, flexural strength and stiffness) of laminated veneer lumber (LVL) beams strengthened by 2-layer flax-glass hybrid fibre reinforced polymer (HFRP) exposed to hygrothermal (50℃ and 95% RH) and weathering (cyclic water spray-ultraviolet radiation) conditions for one month. Effects of environmental exposure and fabric sequences on flexural behaviour of LVL-HFRP beams were studied. LVL-FG and LVL-GF beams (inner plies bonded to LVL were flax and glass fibres, respectively) were tested under four-point bending. Tensile test on HFRP flat coupons was also conducted to provide the tensile parameters of HFRP in LVL-HFRP beams. This study showed that the hygrothermal and weathering exposures reduced the maximum load (by 11.4–32.2%), flexural strength (by 19.1–40.0%) and increased the ductility index (by 18.3–41.7%) of LVL-HFRP beams. The hygrothermal exposure did not affect flexural stiffness. The fabric sequence affected the flexural behaviour of LVL-HFRP beams. LVL-GF beams showed lower maximum load and flexural strength than those of the LVL-FG beams, which was attributed to the HFRP delamination in the LVL-GF beams. A theoretical prediction model for the ultimate bending moments of LVL-HFRP beams was used, and the calculated values showed a good agreement with the experiments.

Performance of composite stone beams with prestressed NSM longitudinal CFRP reinforcement subjected to bending

This paper presents an investigation on the performance of stone beams reinforced with prestressed near-surface mounted (NSM) longitudinal carbon fiber reinforced polymer (CFRP) bars subjected to bending. Seven composite stone beams and four bare ones were tested. The test variables included the reinforcement ratio and prestressing level of CFRP bars, and the shear span to depth ratio of the tested beams. Test results showed that, the composite stone beams with either prestressed or non-prestressed reinforcement exhibited a ductile failure with visible deflection and multiple cracks. As the level of prestressing force increased, the cracking load and the shear capacity of composite stone beams increased but the deformation capacity decreased. The increase in reinforcement ratio could suppress the crack propagation and increase the flexural capacity of composite stone beams. As the shear span to depth ratio decreased, the cracking load, the shear capacity, and the peak load corresponding to flexural capacity of composite stone beams increased accordingly. Theoretical models for predicting the cracking and peak moments of composite stone beams were developed based on sectional mechanical analysis, and a good agreement with the experimental results was obtained.

The numerical simulation of soil–structure interaction containing sustainable materials

As a result of urban transformation activities, natural disasters, regional and global wars, billions of tonnes of waste concrete occur. Therefore, the remediation process of waste concrete is one of the critical research topics of recent years. The sustainability concept provides a primary bridge between the demand for natural concrete material and the remediation process of waste concrete. Recycled aggregate and recycled concrete aggregate, which may be named sustainable materials, are obtained by the recycling process of waste concrete. Many experimental and numerical studies have been conducted in recent years to show that this sustainable material is an alternative product to natural aggregate. In this study, a comprehensive numerical simulation of foundation beams resting on soils incorporating conventional and sustainable materials has been performed. The foundation beams considered include some with conventional concrete properties and some with sustainable concrete properties. Additionally, the material conditions of soils are assessed, using six different mixed recycled aggregates as filling material. Based on the numerical simulation, the deflection, rotation, bending moment, shear force and spring force capacities of conventional and sustainable foundation beams resting on soils exhibited slightly different behaviour depending on the recycled concrete aggregate and mixed recycled aggregate ratios. Finally, comparing the numerical simulation results of soil–structural interaction members incorporating conventional and sustainable materials indicated that the soil–structure interaction modeling process applied to conventional foundation beams resting on soils is also valid for sustainable members.

Analysis of an Isolated Footing taking into account Soil Structure Interaction

In the proposed study an attempt is made to understand the effect of soil interaction on the performance of building frames resting on isolated footing. The purpose of this study is to describe and investigate different approaches of considering the linear interaction analysis (SSI- Soil-Structure Interaction) with regard to the response in the superstructure. The present study is focused on SSI analysis of symmetrical space frame of 3 bays in both x and y direction, 2 storey (3X3X2), 3 bays in direction, 4 storey (3X3X4) and 3 bays in both direction, 6 storey (3X3X6) resting on isolated footing with fixed base. Medium hard clay type of soil is used for this SSI study. The interaction approach is incorporated in the analysis using Conventional analysis (NIA model - Non interaction analysis) and Soil-structure interaction analysis (LIA model - linear interaction analysis). ANSYS is used for developing these models. The effect of SSI on various structural parameters i.e. natural time period, base shear, roof displacement, beam moment and column moment and axial force are studied and discussed. The comparison is made between the approaches of conventional and liner interaction modeling. The study reveals that the SSI significantly affects the response of the structure.

Elastic lateral-torsional buckling behavior of steel I-beams with sinusoidal web openings

Recent advances in the production of perforated steel profiles have given rise to the emergence of new opening patterns, among which the sinusoidal pattern stands out. Profiles manufactured with this type of opening are usually used to overcome large free spans and they have a cross-section height considerably higher in relation to the plain-webbed profile that originates them. Due to this, profiles of this nature are more susceptible to failure by lateral-torsional buckling. However, not enough research is found on this type of profile, especially in relation to global instability. In addition, the existing lack of consensus in determining the critical moment in alveolar beams is amplified when considering the openings in a sinusoidal pattern. Therefore, the present work consisted of a numerical evaluation of the elastic stability behavior of these elements through ABAQUS software, in which an extensive parametric study was developed with 15,205 finite element models. Through the parametric study, it was possible to evaluate the influence of several geometric parameters of these beams in the critical moment, as well as to propose an analytical calculation method suitable for beams with sinusoidal openings, considering different loading conditions, which showed excellent compliance with the numerical results.

Chromatic transverse dynamics in a nonlinear plasma accelerator

We present a theoretical investigation of the chromatic dynamics of the witness beam within a plasma based accelerator. We derive the single particle motion of an electron in an ion column within a nonlinear, blowout wake including adiabatic dampening and adiabatic variations in plasma density. Using this, we calculate the evolution of the beam moments and emittance for an electron beam. Our model can handle near arbitrary longitudinal phase space distributions. We include the effects of energy change in the beam, imperfect wake loading, initial transverse offsets of the beam, and mismatch between the beam and plasma. We use our model to derive analytic saturation lengths for the projected, longitudinal slice, and energy slice emittance under different beam loading conditions. Further, we show that the centroid oscillations and spot sizes vary between the slices and the variation depends strongly on the beam loading. Next, we show how a beam evolves in a full plasma source with density ramps and show that the integral of the plasma density along the ramp determines the impact on the beam. Finally, we derive several simple scaling laws that show how to design a plasma based injector to produce a target beam energy and energy spread.

Redistribution of Moment in Concrete Continuous Beams Reinforced with Steel Rebars and Fiber-Reinforced Polymer

Redistribution of Moment in Concrete Continuous Beams Reinforced with Steel Rebars and Fiber-Reinforced Polymer

On the unloading action of torques in beams reinforced concrete coffered floors

The purpose of this work is the qualitative and quantitative identification of the unloading effect in the beams of direct coffered floors from the action of torques. To solve the problem in the computer complex SCAD, the bending and torsional moments in the beams of a direct coffered floor hinged along the contour with a plan size of 8.0 8.0 m with different widths of the beams installed with a step of 1.0 m were determined. As a computer model, a rod finite element model of beams of rectangular section with a direct application of a linear load to them according to the law of a triangle was used, as the most accurate finite element method. Analytical calculation of the structure is carried out. The calculation data of computer models showed that as the width of the beams increases, the torques in them increase, while the span bending moments decrease. The width of the support contour beam affects the support bending moment of the span beams, which occurs at the point of their joining. The paper presents graphs of the dependence of the values of the span bending moment, the support moment and the torque on the width of the caisson beams. The analytical method for calculating coffered floors does not take into account the rigidity of the support contour, the presence of torques in the beams, their effect on bending span moments and deflections of the structure. This is one of the reasons for the discrepancy between the data compared by the researchers.

Analytical model for compressive arch action in unbonded prestressed concrete beam-column subassemblages under a column-loss scenario

This study investigates the progressive collapse behavior of unbonded prestressed concrete (PC) beam-column subassemblages with different unbonded prestressed tendon (UPT) profiles subjected to the loss of a middle column. Then, in accordance with the compatibility and equilibrium conditions, an analytical model is developed to determine the compressive arch action (CAA) capacity of PC frames considering the effect of boundary conditions and UPT profiles. The developed model can effectively reflect the influence of the prestressed force and tendon profiles on the CAA capacity of PC frames by considering the interaction between the UPTs and structures. Furthermore, the effect of UPT profiles on the progressive collapse mechanism of PC frames is elaborated. Analytical results indicate that the UPTs are a dominant source for the CAA capacity of PC frames. The CAA capacity is sensitive to variation in UPT profiles because the UPTs change the axial force and moment of beams.

Formulation of the critical lateral buckling moment of steel beams under asymmetric loadings

This article investigates the elastic lateral buckling of unrestrained beams. According to the design code, the beam strength is function of the lateral buckling moment. In literature, the buckling moment is function on bending distribution, load height position and the monosymmetry cross section shape. The coefficients C1−C3 are affected to these parameters in the solution. However, no formula or table is available for the case of beams subjected to nonsymmetrical loading. This article proposes an analytical formulation for the critical moment for lateral–torsional buckling of steel beams under asymmetrical loading. The expression of the critical buckling moment, which is based on the Galerkin method, as well as the coefficients (3C) that affect the intensity of the critical moment for asymmetric loading cases, are then proposed. The present method is compared to numerical simulations and available solutions in literature. The results obtained allowed concluding that in the case of asymmetrical loading, the application of the loading cases proposed by the CCM 97 remains unsafe.

Cyclic Testing of Replaceable Steel Coupling Beams with Reduced Beam Sections and Moment End-Plate Connections

Cyclic Testing of Replaceable Steel Coupling Beams with Reduced Beam Sections and Moment End-Plate Connections

Parametric study of 3D steel moment connections with built-up box column subjected to biaxial cyclic loads

In this numerical research, the variation of cyclic behavior of beam-to-box column connection was studied. Dimensional and load conditions were parametrically evaluated with the goal of assessing the applicability and use of this biaxial moment connection according to the Seismic Provisions, such as bending strength and rotation capacity, secant and tangent stiffness, dissipated energy and strong column-weak beam relationship. A total of 83 different models of 3D connections were developed using in ANSYS software with the load at the top of the column. Results show a cyclic behavior not controlled by axial load. However, the variations of clear span to depth beam ratio caused degradation of the strength, secant and tangent stiffness as well as in dissipated energy. The 80% of plastic moment of beam and rotation at 4% interstory drift were reached for all models analyzed according to criteria established in AISC 341. Finally, the configurations designed with low levels of axial load are controlled by the design of the web panel zone shear, while configurations designed for high levels of axial load are controlled by the strong column-weak beam criterion. • The hysteretic response curves of the joints with end-plate connections and built-up box column subjected to cyclic loading were plumped. • The beam can concentrate the inelasticity effectively in a wide deformation range. • The behavior exhibited is acceptable for 7 < L/d < 20 ratio. • A numerical prequalification was possible.

STUDY ON BEHAVIOUR OF DIAGRID STRUCTURE FOR DIFFERENT DIAGRID ANGLES WITH CONSTRUCTION SEQUENCE ANALYSIS

It is frame work of diagonally intersecting metal, concrete, or wooden beams i.e. used in the construction of building and roofs and its diagonal components can carry both gravity and lateral loads due to their trigulated design and axial actions. Construction sequence analysis is a non linear analysis approach in which the structures in analyzed at various stages corresponding to the construction sequence and partially required loads are applied sequentially at every stage. A plan of 20 m × 20m size was considered. ETABS 2016 was used in modeling and analysis of structural members and subjected to seismic loads for zone V as per IS1893-2016. In total 6 models with different diagrid angles (520 620 &amp; 680 ) and column removal scenario at different floor levels. To study bending moment and shear force variation in transfer girder beams for with and without construction sequence and study axial force variation in columns for with and without construction sequence analysis &amp; also study seismic response of diagrid structure with different diagrid angles i.e., storey displacement and storey drift. For response spectrum analysis when compared different diagrid models (620 and 680), diagrid model 680 is less displacement as compared to other degrees implying that we take above 680 diagrid angle is best for tall buildings. A more realistic design than the standard design is produced by including sequential load case in the study of multistory RCC structure. Key Words: Diagrid angle, construction sequence analysis,

Elastic lateral-torsional buckling of beams with warping restraints at supports

Analytical formulations for the evaluation of the critical bending moment for lateral-torsional buckling of a beam taking into account warping restraints at supports are proposed in this paper. A theoretically exact solution is firstly derived from differential equilibrium equations using infinite power series for the twist rotation. Next, the deflected shape is approximated using a single or several base functions for the displacement and rotation fields. The energy method is then used to derive approximate expressions of the critical bending moment of beams subjected to various loading conditions: constant/linear bending moment distributions, mid-span pointwise transverse force or uniformly distributed load. The warping coefficient kw does not depend on the bending moment diagram. The equivalent uniform moment factor C1 can be conveniently expressed as a product of two coefficients, one related to the bending moment distribution and the other to the warping restraints stiffness. Finite Element analyses of beams with warping restraints at supports have been performed considering a shell elements model created in ANSYS and a beam elements model developed in LTBeamN.

A New Proposal for Live Load Distribution Factors of Bridges with Transverse Beams

Many bridge superstructures use transverse beams as load carrying components. In these systems, usually the transverse beams are connected to the main longitudinal girders or trusses on the two sides of the bridge. Such systems are commonly used in plate girder, box girder, cable-stayed and truss bridges. The live load distribution factor (LLDF) for bridge superstructures with transverse beams in AASHTO-LRFD bridge design specification has remained unchanged for decades and is prescribed as a function of the distance between the transverse beams. However, for slab-beam superstructures in which longitudinal beams at close spacing carry the loads to the substructure, the LLDFs have gone through many changes throughout the years and in their current forms depend on many parameters such as concrete slab thickness, beam span, longitudinal beam stiffness as well as the distance between the longitudinal beams. This study investigates the factors affecting the LLDF for transverse beams and intends to obtain new equations similar to AASHTO’s longitudinal beam equations. For this purpose, 3D finite element models of different sample bridges were developed and critical parameters affecting the LLDF were identified and varied. Accordingly, the LLDFs for moment and shear forces of transverse beams were obtained through regression analyses. The proposed equations have less than 3.1% of average error for the cases considered.