Structural Internal Force Research Articles

Numerical Analysis of a New Block-Type Rail Bearing Beam for the Mid-Low-Speed Maglev Train

In this study, a new block-type rail bearing beam is presented, which consists of a cast-in-place base and prefabricated blocks. The finite element analysis is conducted to assess the proposed new rail bearing beam structure. The performed finite element method (FEM) simulation focused on the dynamic stress at the bottom of the rail bearing beam and structural internal force and deformation under the case of train loading, etc. Besides, the relationship between first-order natural frequency and activation frequency in the new support rail beam structure is analyzed and the beneficial effects on the internode connection structure are quantified. The results show that the increase in driving speed has the most significant effect on the vertical acceleration of the structure, and the self-vibration frequency of the structure is relatively large, which means the structure is safe. Since previous research seldom focuses on this block-type rail bearing beam, this study lays a valuable foundation for the construction of a rail bearing beam for the mid-low-speed maglev train.

Analysis on the stiffness iteration of segmental joints in segmental linings: Method and sensitivity analysis

In current structural analyses on segmental linings, the bending stiffness of segmental joints is usually treated as a constant, which results in a deviation in the calculated internal forces and deformation. In view of this, a finite element model of segmental linings is established using one ring and two half rings. An iterative algorithm is designed with a 3D curved surface of bending stiffness for the segmental joint, obtained from a series of full-scale tests under different axial force and bending moment cases. The rational convergence criteria for the iterative algorithm are recommended by evaluating the convergence efficiency of the iterative algorithm. Moreover, the influence of load magnitude and initial value of bending stiffness, as well as the changing laws of structural internal forces and deformation with the assembly angles, are presented and analyzed. The results show that with the same load, the convergence of the iterative algorithm in staggered-jointed assembly structures (STGS) is better than that of straight-jointed assembly structures (STRS), owing to its greater overall stiffness. The initial input value of bending stiffness has no effect on the convergence of the proposed iterative algorithm, and generally the convergence performance in STGS is better than that in STRS. In STRS, the bending moment is most sensitive to the changes of assembly angles, while in STGS the assembly angles have great influence on both the bending moment and structural displacement. Without the stiffness iteration, the maximum differences for maximum axial force, bending moment, and displacement under different assembly angle in STRS are 11.7%, 31.9% and 22.3%, respectively, and that differences in STGS are 10.4%, 59.3% and 35.1%, respectively. With the stiffness iterative method, the increase amplitude of the maximum axial force, the maximum bending moment, and the maximum displacement in STRS and STGS are 50.0%, 317.4%, 77.1% and 41.9%, 459.3%, 156.5%, respectively, indicating that changing the assembly angles is a rational way to control the internal structural forces and deformations.

Study on thermo-mechanical coupling method of ship cabin with ceiling vent under fire condition

Objectives The performance analysis of ship cabin steel structures in fire situations is fundamental to structural fire resistance design. Compared with research conducted under traditional standard fire conditions, research based on the real fire temperature field can more accurately analyze the mechanical response behavior of cabin structures. Aiming at an open cabin (i.e. engine room) structure, a fire-heat-structure coupling method combining FDS and ANSYS is developed. Methods First, the FDS simulation is utilized to obtain the temperature information of the inside ship wall exposed to the fire, which is then used as the boundary condition transferred to the structural finite element analysis software ANSYS. Transient thermal analysis concerning the temperature field of the cabin structure is then conducted, and the thermal-structural coupling analysis of the ship cabin structure carried out in a real fire scenario. Results The results of the case study using the proposed method demonstrate that the stress distribution is not uniform due to the uneven temperature distribution. The maximum stress is concentrated at the edge of the cabin, with a value of 19 MPa. The structure does not reach the failure limit after being exposed to fire. Conclusions Compared with the traditional standard fire curve method, the proposed method has two advantages for addressing structural response: the non-uniform elevated temperature of the structure and real fire temperature rise. More attention should be paid to the change in structural internal force caused by non-uniform temperature rise in an open ship cabin.

EFFECTS OF SPOILER ON WIND LOAD OF FLAT ROOFS EXPOSED TO SEPARATION BUBBLE

Through wind tunnel test, wind pressure characteristics of flat roofs exposed to separation bubble with or without spoilers were investigated and compared. Based on this, the mechanism of the spoiler for reducing wind-induced effect and the recommended inclination were given. Distribution and statistics of wind pressures were demonstrated. It is shown that the mean and fluctuating pressures are reduced by setting the spoilers, except those near the leading edge. In the separated region, the skewness and kurtosis of wind pressures significantly decrease, which implies the less obvious non-Gaussian nature. The influence of spoilers on wind pressure correlation was analyzed. It is observed that the longitudinal correlation attenuates dramatically, while the degenerative transverse correlation only occurs near the leading edge. The variation of total uplift forces and overturning moment were given. For the spoilers with inclination of 0°, 10° and 20°, the total mean uplift forces are decreased by 6.3%, 8.2% and 6.6% respectively, the total mean overturning moment are decreased by 18.2%, 21.9% and 23.3% respectively. With the obtained wind loads, the static response analysis was conducted. It is demonstrated that the axial force at the column bottom, the moment at the column bottom and the displacement at the roof center can be reduced by up to 13.1%, 15.6% and 10.1% respectively. Based on the statistics, the correlation, the total force, and the structural internal force, the recommended inclination of spoilers on flat roofs is 10° within the investigated scope.

Analysis of 120m Circular Enclosed Coal Yard Based on Finite Element Mechanics

Large diameter circular closed coal yard has large coal pile, high coal pile height, and the cancellation of expansion joints, which has many adverse effects on the structure. The study of finite element analysis method, in view of the large stack on the effect of pile and pile of coal load and temperature effect on structure to do the analysis, the influence of material parameters was verified the correctness of the structure internal force under the condition of various loads is obtained as a result, the temperature effect may produce several times the pile of coal load internal force, provides reference for engineering design.

Wind Resistant Analysis of 5000m Hyperbolic Parabolic Spatial Mixed Cable Suspension Bridge

Combined with the engineering background of a 5000-meter Strait Suspension Bridge, the configuration study of the hyperbolic parabolic space cable suspension bridge was carried out, and the ANSYS finite element analysis model was established to analyze and study the structural internal force and dynamic modal characteristics. The research shows that the hyperbolic parabolic space mixed cable suspension bridge has excellent spatial stiffness and wind stability performance, its torsional frequency and torsional frequency ratio are significantly improved, the critical wind speed of flutter is greatly improved. In order to further improve the wind stability of the hyperbolic parabolic space mixed cable suspension bridge, temporary wind resistance cable measures adopted during strong typhoons are proposed. This method can ensure that the 5000-meter-level hyperbolic parabolic space mixed cable suspension bridge has the ability to withstand 120 m / s rare extreme typhoons.

Research on Seismic Reduction and Isolation Measures for Urban Underground Station Structure

Based on a rectangle underground station structure, two-dimensional finite element models are established in this study to explore the effectiveness of different seismic reduction and isolation measures for underground structure, where Davidenkov model is adopted to consider the soil nonlinearity and the underground structure is considered elastic. The performances of the seismic reduction and isolation measures are evaluated by assessing the structure internal force and deformation responses. Depending on the ratio of wave impedance between the isolation layer and the structure, the isolation layers are divided into rigid and flexible types. The effects of the length and elastic modulus of rigid isolation layer as well as that of the thickness and shear modulus of flexible isolation layer are investigated. The results show that the seismic reduction effect of rigid isolation layer is better with the increase of stiffness, and the effect of flexible isolation layer is more obvious with the decrease of stiffness, which are consistent with the classical impedance theory. Furthermore, the middle column of subway station is usually the most vulnerable during seismic shakings, and one viable way to improve its seismic behavior is to reduce the column end constraints. Therefore, different column constraints consisting of swing, hinge, sliding connection and isolation bearing are considered. The numerical results suggest that among the different column end constraints considered, the sliding connection is comparatively more favorable, which can effectively limit the lateral deformation of column while imposing no horizontal reaction force.

Research Overview on Numerical Simulation of The Dismantling Process of Large-span Steel Structural Roof

The dismantling of large-span steel roof is a complex evolutionary process involving redistribution of internal force. In order to ensure conformity of the structural internal forces to the design, safety and reliability during the demolition, it is necessary to make accurate simulation analysis of the dismantling process to determine a reasonable dismantling plan. With a review of the simulation methods adopted in the dismantling process of large-span steel structure and analysis of the relevant research results, this paper elaborates on advantages, disadvantages and adaptability of each method, which can serve as a basis for the study of roof dismantling.

Research on General Design and Application of Double-circuit T-Connection Tower In 110kV

Based on the investigation results and the current general design of state grid, this paper reasonably planned the design conditions of the tower. Taking the general design module as the basic tower type, a kind of double loop T-connection tower in 110kV with high generality was proposed, then carry out tower head planning and structural internal force analysis. Finally, the electric field finite element simulation is carried out to demonstrate the safety and reliability of the T-connection tower of cross arm arrangement. The tower can cover the T-connection conditions of 110kV double-circuit line in most areas of the country, and draw the tower diagram, which can be included in the general design of state grid transmission tower for reference of line designers. The cross arm of tower head is arranged in a crisscross way, which greatly simplifies the the double-loop T-connection scheme. One tower can replace the traditional multi-tower to complete the T-connection of the line, which reduces the cos t and occupation of land, also achieves good economic and environmental benefits.

Seismic experiment on blind-bolted joint in concrete-filled double steel tubular structure

In this study, blind-bolted joints were designed for use between steel beams and concrete-filled double steel tubular (CFDST) columns to utilize the structural advantages offered by double steel tubes. Six joint specimens were tested under a constant axial load and lateral cyclic load for a CFDST column. The seismic behaviors of these blind-bolted joints were estimated in terms of the hysteretic curves, ductility, and energy dissipation. The effects of a T-plate section type and steel beam-type on the semi-rigid joints were studied. The test results showed that the failure of the joints began with the yielding of the T-plates, and that the final failure mode was plastic deformation at the steel beam ends. The obtained hysteretic curves were complete, and the energy dissipation ability of the bolted joint was strong. The bearing capacity and energy dissipation of ribbed joints were higher than those of unribbed joints. Based on a steel volume comparison, the installation of stiffening ribs proved to be considerably more effective than the thickening of the T-plate flanges. The strain response of the inner tube in each CFDST column was also estimated. It was concluded that the blind-bolted joints exhibit excellent deformation capacities and structural internal force redistributions. The results of this experimental research could be helpful for the application of blind-bolted joints in fabricated CFDST structures.

Experimental study on seismic performance of a new transfer joint in the steel-concrete vertical hybrid structure

Steel-concrete vertical hybrid structure (S-RC structure) is usually composed of upper steel and lower reinforced concrete (RC) structures. The transfer joint between them is the key part to ensure the vertical structural internal force transferring. This study proposed a new kind of joint by inserting the upper steel column into the lower RC column. To study the seismic performance of this joint, four specimens are tested under cyclic loading. The effects of axial force ratio, steel column size, and embedded depth ratio are investigated and discussed. Test results show that the failure patterns are typical beam flexural failure with plastic hinges formed at the beam ends adjacent to the corbel. All the specimens exhibited satisfied seismic performance with stable load-displacement response, excellent energy dissipation capacity and ductility. Furthermore, the increase of steel column size shows positive influence on the joint strength and stiffness, and larger axial force ratio can greatly improve the energy dissipation capacity, while increasing the embedded depth ratio only improves the strength by less than 10%. Finally, calculation methods for the bearing capacity and design suggestions on the embedded depth ratio of the steel column are both proposed for the new joint, which provide useful guidance on the design of the transfer joint in S-RC structures.

Optimum design calculation method for the reasonable buried depth: A case study from Hong Kong-Zhuhai-Macao immersed tunnel

Immersed tunnels are built on the seabed, which is washed and unloaded by seawater, resulting in a thinner covering layer when compared to drilling blast tunnels. If the overburden layer is too thin, it increases the tunnel's buoyancy and the shear stress of the joints; if the overburden layer is too thick, the external pressure increases and reducing structural stability. To limit the impacts of stress, instability, and costs, the buried depth of a tunnel is an important variable. In this study, a calculation of the reasonable buried depth for an immersed tunnel is presented. Using the Delphi method and fuzzy set theory, the weights associated with an engineering analogy, foundation settlement, structural internal force, and seismic load methods each method were obtained for a set of proposed buried depths. These weights were used to construct an optimization calculation model for optimal buried depth, which was then applied to the Hong Kong-Zhuhai-Macao immersed tunnel. Based on the model results a buried depth of 14.25 m was selected. The results provide a reference point and guide for future research on calculating a reasonable depth for immersed tunnels.

Case Study of the Effect of Rainfall Infiltration on a Tunnel Underlying the Roadbed Slope with Weak Inter-Layer

It is a common type of tunnel under-cross the roadbed slope with weak inter-layer. Rainfall infiltration will cause soil softening, matric suction and strength reduction, which seriously threaten the safety of slope and tunnel. This paper presents a case where a tunnel underlying the roadbed slope with weak inter-layer in Guiyang 1# line, China. The seepage calculation model in MIDAS GTS/NX software, considering hydraulic permeability coefficient characteristic curve and soil-water characteristic curve, was used to analyze the stress and deformation of the roadbed slope and tunnel. The results reveal that rainfall infiltration has great influence on the deformation of roadbed slope with weak inter-layer and the force of internal tunnel. Slope displacement increases rapidly in the early stage and decreases in the late stage, but the absolute value of displacement increases continuously and the slope safety factor decreases gradually, which makes the slope in a dangerous state. The force of tunnel lining increases in the early stage and decreases with the recovery of soil strength after rainfall. The control effects of anchor cable and anti-slide pile reinforcement on slope sliding and tunnel stress were studied. And the anchor cable reinforcement measure is more effective on reducing slope slip and tunnel lining structure internal force.

The effect of rise-span ratio on the rigid-framed arch bridges

The rigid-framed arch structure is a popular bridge structure on medium and small span bridge such as flyover. Rise-span ratio affects the rigid-framed arch structure performance, in order to analyse the influence on the rigid-framed arch structure of different rise-span ratio, a calculation model of the rigid-framed arch structure on the basis of the project established using the large general finite element software, by adjusting the rise value to change the rise-span ratio, analysing and comparing the structural internal force and deformation condition of the rigid-framed arch in different rise-span ratio under the action of constant live load, temperature change, and foundation settlement. The influence of different rise-span ratio on the rigid-framed arch stress summarized.

STRUCTURE SETTING ON COMPOSITE-BASED SOILS

The paper studies the interaction between the building construction and composite-based soil with a view to determine its elastic properties affecting the structure deformation and internal forces. The soil model is assumed to be elastic, according to the Winkler coefficient calculated from the Kolosov stress decay function. The Galerkin numerical method used in calculations utilizes basic functions corresponding to the type of fixing the discontinuous and continuous structures. Unknown coefficients in linear combinations of basic functions are obtained via linear algebra methods, solving the system of equations. The force functions of the structure are found by derivation of the deflection function. Geological parameters are accepted to be real and matching the construction conditions of a large industrial warehouse of agricultural designation in the Pskov region, Russia. The soil effect on the flexural strength, shearing forces, and bearing reaction is estimated under the discontinuous and continuous structures at the available geological soil parameters. The structure setting on composite-based soils under the operating load is predicted herein.

Pre-supporting mechanism and supporting scheme design for advanced small pipes in the silty clay layer

This study presents a design method for the advanced support of subway tunnels for different water content conditions in the silty clay layer. The influence of particle size distribution and water content on the mechanical properties of silty clay is studied through laboratory tests. In addition to the actual construction of the Harbin subway with a silty clay layer, a numerical calculation model is established to study the surface settlement, crown settlement, and supporting structure internal force during the tunnel excavation and support process under different working conditions. Furthermore, the mechanism of action of the advanced small pipe support is clearly defined, and a stability analysis model of the top and bench excavation in a silty clay layer is proposed to evaluate the stability of the tunnel face. The necessity and rationality of the pre-support is quantitatively analysed using the stability coefficient. The laboratory tests illustrate that within a certain range of clay content, the shear strength of silty clay decreases with an increase in water content. The silty clay was further divided into subgrades. The pre-support transfers the loose soil load to the initial support, which improves the early utilization of the lining structure. The advanced small pipe grouting increases the range of the bearing arch, shortens the interval distance of the supporting arch feet, and reduces the vertical load acting on the tunnel face. For the condition of subgrade V in silty clay strata, the stability of the tunnel face can be maintained without the advanced small pipe support. For the condition of subgrade VI1, the advanced small pipe support must be applied to ensure the stability of the tunnel face, but the grouting reinforcement measures are not required. For the condition of subgrade VI2, the advanced small pipe support and grouting reinforcement must be used simultaneously to ensure the stability of the tunnel face.

Modal analysis of support structure of cylindrical container

The paper deals with dynamic analysis of a container. The analyzed structure consists of a steel support structure and a cylindrical container. The container is used for storage of road salt and other spreading materials during winter road maintenance. Three variants of support system of a structure have been analyzed. These have been introduced into the model as different boundary conditions. The modal analysis was performed, whose results are eigenfrequencies and eigenshapes of the structure. In the final part, the results obtained from the seismic analysis of the structure (displacements and internal forces) have been presented.

Spectral analysis of the support structure of the cylindrical container

The paper deals with dynamic analysis of a container. The analyzed structure consists of a steel support structure and a cylindrical container. The container is used for storage of road salt and other spreading materials during winter road maintenance. Three variants of support system of a structure have been analyzed. These have been introduced into the model as different boundary conditions. The spectral analysis was performed in which the response spectra taken from the Eurocode were used. In the final part, the results obtained from the seismic analysis of the structure (displacements and internal forces) have been presented.

Research on Tight Seam Stitching Technology for Bidirectional Composite Floor Slabs

A new type of tight seam stitching technology for bidirectional composite floor slabs is proposed in this paper. Full-scale tests on the construction of slab joints were carried out and contrasted with cast-in-place slabs. The mechanical properties of a new type of joint structure were studied, including the failure mode, bearing capacity, stiffness, and crack distribution of a floor slab. Based on these tests, a refined finite element analysis was performed, and then the mechanism of the force transfer between a steel bar and the concrete at the joint was deeply studied. The results show that the mechanical performance of the new joint of the tight seam stitching was essentially the same as that of the cast-in-place structure. The numerical calculation agreed well with the experimental results. A closed annular steel bar at a joint location could effectively transfer the structural internal force.

Different configurations of cores and shear walls in tall buildings

A core system for buildings has been recognized as an effective tool for managing the response of the building when an earthquake happens by decoupling the building structure from potentially damaging earthquake-induced forces. A challenging issue in this context is the application of the configuration of the core system. A review of recent studies shows that the configuration of cores has not been substantial investigated. This study presents seismic design concepts in which different configurations of cores are applied to a building. Nine steel buildings were modeled with rectangular core, octagon core, circle core, lozenge core, cross core, multi core, irregular core 1, and irregular core 2. All structural models are subjected to components of the 1940 El Centro earthquake and are evaluated and compared with the response of a structure without core. All models were also compared with and without opening in cores. The performance of the structural models under seismic excitation was evaluated by conducting linear dynamic time history analysis. Seismic results are investigated in terms of joint displacement and structure internal member forces. Results show that the presence of irregular core 1 significantly reduces the seismic response of the structure in this plane.