Cross Bracing Research Articles

The effect of frame bracing and filling percent on the natural frequency of an elevated concrete tank

Liquid storage tanks are structures of high importance which are considered as main lifeline elements in modern life. In this work an empty elevated tank made from concrete supported on concrete frame consisting of four stories had been studied for free vibration analysis. Cross bracing is added to the supporting frame on it's four sides in order to study it's effect on the values of natural frequencies. The results were different between increment and decrement in the values of natural frequencies according to the location of the bracing and the number of mode, also, filling percent had been studied to know it’s effect on natural frequency

Stability behavior of T-shaped retrofitting cross bracings in existing transmission towers

To analyze the stability behavior of T-shaped retrofitting cross bracings, finite element models were developed and validated by full-scale experiments of cross bracings available in the literature. Effects of stress ratio, nominal slenderness ratio, width-to-thickness ratio, and yield strength on the failure mode and bearing capacity were considered for T-shaped retrofitting cross bracings without auxiliary members (TCB) and with auxiliary members (TCBA). Results show that the failure modes of T-shaped retrofitting cross bracings are out-of-plane bending of the entire brace. As the stress ratio decreases, the failure modes transition to the bending of the longer section of the brace. When the nominal slenderness ratio is below 160 for TCB, local buckling dominates and nominal slenderness ratio has few effects on the bearing capacity. Also, stress ratio has a minimal impact on bearing capacity when it is less than −0.2. In addition to above, bearing capacity is related to nominal slenderness ratio and stress ratio. A higher width-to-thickness ratio increases the nominal stability coefficient for TCB, but has a negligible effect on TCBA. Increasing yield strength can effectively enhance the bearing capacity of TCB when stress ratio is below 0, while yield strength has little impact in other conditions.

Study on seismic performance and restoring force model of framed CFST column-composite box beam joints

Quasi-static tests are conducted on framed concrete-filled steel tubular (CFST) column-composite box beam joints to study the deformation characteristics and restoring force performance under seismic loads. The joints' seismic performance is evaluated. This study shows that the joints with three different connection forms (single-limbed diagonal brace, cross brace, and diaphragm) in the core area have good bearing and energy dissipation capacities. As a result, the joints exhibit excellent seismic performance. The theoretical and fitting analyses of test results reveal the stiffness degradation law for this type of joint. Additionally, a fixed-point directional degradation trilinear restoring force model is established and compared with the test results. The research results indicate that the proposed restoring force model accurately predicts the nonlinear recovery behavior of the joint under seismic loads. This model is in good agreement with the hysteretic curve of the test, providing a theoretical basis for the seismic design and performance evaluation of the joint and for the seismic design and toughness optimization of a structure.

Healing of Acute Anterior Cruciate Ligament Rupture on 3-month MRI in 235 People Managed with the Cross Bracing Protocol

Healing of Acute Anterior Cruciate Ligament Rupture on 3-month MRI in 235 People Managed with the Cross Bracing Protocol

Non-operative treatment for ACL rupture, rehabilitation and Cross bracing protocol, have unacceptably high failure rates relative to surgical stabilisation for return to pivoting sports.

Non-operative treatment for ACL rupture, rehabilitation and Cross bracing protocol, have unacceptably high failure rates relative to surgical stabilisation for return to pivoting sports.

Comparative Analysis of Various Bracing Configurations and Their Impact on Elevated Water Tank Performance

During a few extremely distressing earthquakes in India, R.C.C. elevated water tanks suffered significant damage or collapsed. This may have been brought on by incorrect staging geometry as well as ignorance of how the tank's supporting system should behave in the event of an earthquake. The elevated water tank is made up of structural components such as footings, beams, columns, and slabs. Subjected loads are passed between these components and ultimately to the soil's sub-grade. When an overhead tank is advantageously analysed, the elevated water tank behaves differently for distinct types of loadings (Dead, Live, and Seismic). Various combinations of loads that support the possibility of occurrence are indicated by the codes for Indian standards. The primary goal of this research is to improve performance during earthquakes and complement conventional staging by better understanding the behaviour of various bracing systems. Equivalent static analysis of various bracing system types applied to the elevated circular water tank staging in the seismic zone are carried out using STAAD Pro. The axial force and maximum bending moment of the circular water tank are examined in the X, Y, and Z axes. Several models are used to calculate the axial force and maximum bending moment for staging with cross bracing, diagonal bracing, and alternating diagonal bracing.

Research on the Mechanical Performance of a Mountainous Long-Span Steel Truss Arch Bridge with High and Low Arch Seats

The Loushui River Bridge is a mountainous long-span steel truss arch bridge with high and low arch seats. The design and construction of the bridge follow the principle of minimizing environmental damage and promoting sustainable development. In this article, the mechanical performance of this bridge is investigated experimentally and numerically at both the construction and operation stages. A series of validated finite element models were established for linear and nonlinear analyses by introducing geometric imperfections, geometric nonlinearities, and material nonlinearities. Then, several optimized models based on different types of design are compared with the original structure. The results indicate that the stability of the asymmetric bridge met the design requirements in both the construction and operation stages. However, the lateral stability and stiffness of the asymmetric bridge are weak due to the wind hazard that occurred in its mountain ravine. The out-of-plane instability from the short half-arch is the dominant failure mode, and the weakest area is where the arch ribs intersect with the bridge deck. It can be solved by adding more cross bracings without affecting the clearance above the bridge deck or by improving the material intensity of the arch.

Healing of acute anterior cruciate ligament rupture on MRI and outcomes following non-surgical management with the Cross Bracing Protocol

ObjectiveInvestigate MRI evidence of anterior cruciate ligament (ACL) healing, patient-reported outcomes and knee laxity in patients with acute ACL rupture managed non-surgically with the Cross Bracing Protocol (CBP).MethodsEighty consecutive patients...

Finite Element Simulation and Experiment of Temporary Active Transverse Brace of Inward-inclined Bridge Tower Construction

For the bridge tower with large inclination angle, the beam element in Midas finite element software is used to model and analyze the bridge tower structure, and its accuracy is difficult to guarantee. In this paper, taking the construction of a suspension bridge’s inward-inclined tower as the research background, the finite element simulation of the inward-inclined bridge tower is carried out by using the two modeling methods of the beam element and the solid element. The calculation accuracy of the beam element model, the specific position and the jacking force applied by the active transverse brace of the inward-inclined bridge tower are determined, and the field test of the tower bottom stress during the construction process is performed. The results show that: when the inclination angle of the bridge tower is small (5 °), the beam element element is used for modeling and analysis, which has fast calculation speed and high calculation accuracy; When the inclination angle is 15 °, the error of the beam element model exceeds 30%, and it is recommended to use the solid model for calculation; the active cross brace plays a key role in controlling the stress at the bottom of the tower column before the lower cross beam is applied. And after the construction of the cross beam, the active cross brace forms a closed frame structure with the lower tower column, and the subsequent cross brace has little impact on the stress at the bottom of the tower column; Compared with increasing the number of temporary cross braces, increasing the jacking force can improve the stress at the bottom of the tower. And by adjusting the position of the active cross brace and applying the appropriate active jacking force, the stress at the root of the tower column can be greatly improved.

Seismic assessment of different vertical bracing systems in staging of elevated liquid retaining tank

The study of earthquakes indicates that earthquakes have a significant impact on the grid system, as well as significant catastrophic effects on human life, buildings, bridges and other structures. In macro scale water distribution network, water tanks play the key point site component, and it is the most vulnerable element in case of an earthquake. Water tanks play a vital role in our lives as they help to store and supply water for domestic and commercial purposes. They also store water for firefighting, irrigation and other agricultural needs. Based on the previous literatures, papers, articles, and other sources, it can be concluded that during an earthquake generally, a liquid retaining structure, i.e., water tank failure generally occurs due to the inability of the staging system to resist lateral movement. Most post-earthquake failures of elevated tanks are likely to result from dynamic buckling caused by overturning moments of seismically induced fluid inertia and surface sloshing waves. As they are the vital structures of our society, their construction and proper seismic evaluation is crucial. In this paper, the seismic response of liquid retaining tanks for different vertical bracing systems has been compared as per IS1893:2014 part-2 and the response spectrum analysis procedure. In all the models the storage tank's capacity has been taken as 150 cubic meters, keeping all the dimensions the same. The loads are considered as per IS875, IS3370 and other relevant codes. The different models considered in this paper are – water tank without bracing, water tank with diagonal bracing, water tank with cross bracing, water tank with K-type bracing, water tank with chevron bracing and water tank with box bracing. These models have been compared on the basis of different seismic parameters and optimized model is being suggested.

Analysis of the stability behavior of cross bracings in transmission towers based on experiments and numerical simulations

Angle steel towers are widely used in various transmission lines owing to their convenient connections, easy availability, simple production processes, and high efficiencies. Cross bracings play an important role in resisting wire tension, wind, and snow loads as the main support components ensuring the stability of an angled steel tower. Thus, an analysis of the buckling resistance of cross bracings is significant in improving the bearing capacity of transmission towers. In this study, full-scale tests of equal-leg and unequal-leg angles in planar tower sections were conducted. The influence of the axial force ratio on the stability of a cross bracing was studied based on numerical simulations and compared with the current codes. The results revealed that the failure mode of an equal-leg angle cross bracing was always out-of-plane buckling, whereas the final failure mode of an unequal-leg angle steel cross bracing could be out-of-plane buckling or both out-of-plane and in-plane co-buckling. With an increase in the axial force ratio, the buckling resistance of the cross bracing decreased rapidly, with over 40% decline in the amplitude. The buckling resistance of the unequal-leg angle was approximately 20% higher than that of the equal-leg angle at all axial force ratios. Compared with the current codes for tower structures, we discovered that the code values and finite-element results were considerably different. Notably, the calculation methods of ASCE 10-15 and EN1993-3-1 neglect the variation in the effective length with the axial force ratio. Although DL/T 5154-2012 considers the effect of the axial force ratio, the values are all greater than the finite-element results. The findings of this study can help elucidate the cross bracing stability in angle steel lattice towers.

Multi‐Objective Optimization for the Cross Brace of a Computer Numerical Control Gantry Machine Tool Based on Intelligent Algorithms

A multi‐objective optimization design method for the cross‐brace structure of a computer numerical control gantry machine tool is proposed to improve mechanical performance. Dynamic and static performance indexes of the cross brace are analyzed. On basis of sensitivity analysis, size parameters which have great influence on mass and dynamic and static performance indexes of the cross brace are selected as design variables for optimization. Objective values under design variables are obtained by orthogonal experimental method, and an objective function is fitted by response surface method. After verifying the fitting effect of the objective function, entropy weight method is used to calculate weight coefficient of each optimization objective, and a comprehensive performance optimization model of the cross brace is built. Accelerated particle swarm optimization (APSO) intelligent algorithm is used to solve the comprehensive performance optimization model. Comparison results before and after the optimization show that the mass of optimized cross brace is reduced by 8.377%, the maximum stress is reduced by 13.252%, and the first‐order natural frequency is increased by 2.183%. The proposed optimization method provides a new idea to improve the dynamic and static performance of the cross brace while reducing its mass.

Comparative Analysis of Multistorey RCC and Semi-Rigid Steel Frame with Cross Bracings Subjected to Mainshock and Aftershock Earthquake Sequence

Strong Ground Motions have a significant impact on structural analysis and design. Seismic evaluation is deemed necessary for the quality, reliability, and feasibility of existing and developing structures. Earthquakes are even more disastrous when a mainshock is succeeded and preceded by aftershocks of higher magnitude. Most of the time, these aftershocks are ignored during analysis. In the last few decades, steel buildings have been crucial to the construction sector. On the other hand, RCC frames are commonly designed structures for commercial purposes and cost-effectiveness. IS 1893 (Part:1)-2002 Criteria for Earthquake Resistant Design of Structures and IS 13920-2016 Ductile Detailing of RC Structures Subjected to Seismic Reactions are majorly used for Seismic Analysis. Steel bracings in the structural system increase the ductility and stiffness of the frame structure. That can be arranged in a variety of ways, such as X, diagonally, alternatively, V, inverted V, K, etc. Cross bracings are used in this paper for the design of a typical multi-story (G+9) semi-rigid steel frame and a typical RCC frame is designed of the same dimensions. Both the frames are modelled and compared using ETABS software and a static nonlinear Time History analysis is executed to examine the performance of both the frames under the Mainshock and Aftershock of Chamoli earthquake. The Mainshock and Aftershock results of the Chamoli earthquake are extracted from the Centre for Engineering Strong Motion Research Ground Motion Database. Base shear, joint displacement, kinetic energy, and story displacement are a few of the variables of Time History Analysis that affect how well a building performs during mainshock and aftershock earthquakes. When analysing the outcomes, it is important to take into account that each of these factors significantly affects how a building responds to seismic loads.

Overall Strength Analysis of Floating Offshore Wind Turbine Foundation

The loads on the floating offshore wind turbine foundation are complex, and the evaluation of its overall structural strength is particularly important. This paper establishes a new type of semi-submersible floating wind power infrastructure finite element model based on the three-dimensional potential flow theory. The long-term forecast design wave method is used to carry out a long-term forecast of the wave load under the control parameters of the characteristic sections, with the wind pressure load superimposed and combined. Finally, the overall strength of the floating foundation under self-existing conditions is analyzed. The research shows that the max Von-Mises stress of the mid-transverse section is 115.6% higher than that of the mid-longitudinal section in the most dangerous state, and the overall strength of the structure meets the requirements of the standard. The high-stress areas appear at the connection between the lower floating body, including the cross brace and the column, while the max stress appears at the connection between the cross brace and the column supporting the wind turbine. Attention should be paid to such key parts in the detailed design stage of the floating foundation. The numerical analysis method and research conclusions can also provide a reference for the analysis and optimization of the same type of floating foundation.

Time history analysis of seismic response of through CFST non isolated and isolated arch bridges

To explore the difference in the impact of transverse bracing on the seismic effect of through concrete-filled steel tube arch bridges with non-isolated and earthquake-isolated, nine non-isolated and earthquake-isolated structural models under different cross-bracing arrangements were established, and Elcentro seismic waves were selected. The internal force, displacement, velocity, absolute acceleration, relative acceleration, and separation of arch ribs of each model were compared and analyzed under uniform excitation along the bridge, transverse and vertical directions, multi-dimensional combined excitation, and multipoint excitation considering the traveling wave effect. Based on the shear force and displacement of the earthquake support, it is concluded that the internal force response of different excitations of various models is more complicated. The installation of transverse bracing on the upper part of the arch rib can reduce the vertical displacement of the arch rib of the nonseismic structure. The “X”-shaped cross brace at the top of the arch rib and the “K”-shaped cross brace at the lower part help to reduce the transverse acceleration of the arch rib. The absolute acceleration and relative acceleration of the seismic structure arch ribs are significantly reduced.

A Comparative Study on Different Types of Passive Energy Dissipating Devices

Earthquake induced structural vibrations causes fatigue and reduction of performance of the tall steel framed structures. One of the effective ways for improving the seismic performance of a structure is the use of bracings, dampers and isolators. These devices change the stiffness and damping of the structures thereby reducing the seismic vibrations to a great extent. The main objective of this study is to compare the different types of passive energy dissipating devices in a 3 bay 10 storey steel frame building for better seismic response. The frame was modelled in SAP2000® and some of their responses to earthquake such as base shear, maximum joint displacement, inter storey drift were determined and compare during non-linear dynamic time history analysis in SAP2000®.The passive energy dissipating devices used in this study are diagonal bracing, v bracing, cross bracing, rubber base isolator and friction damper. At first a single storied shear frame model was tested in shake table and results obtained from SAP 2000® were compared. The close proximity validated the procedure. It is observed that addition of dampers to the system increases the stiffness to the frame. When compared, displacement for steel frame with dampers is reduced by 80% and that with different bracing systems are reduced up to 78% as compared to bare steel frame. For base isolators, base shear decreases up to 63.33% but an increase in the maximum joint displacement was observed. The comparison of performances of all types of dissipating mechanisms has been presented in the study.

Experimental and numerical study on the effective length of tower cross bracing

Based on the present study, a new design formula for the effective length coefficient of the commonly used cross bracing in transmission towers is proposed. A total of 22 structural tests were conducted considering the interaction in the buckling of cross bracing. The test results, including the failure modes and load-response histories, were reported. The numerical simulations were conducted and validated using multiple comparisons. The ultimate strengths, calculated by the Chinese design code of DL/T 5154, are not sufficiently accurate. An extensive parametric study based on a calibrated finite-element model was conducted to investigate several influential parameters. Implicit theoretical equations for effective length were formulated and evaluated. The numerical results were subsequently used to obtain a new design formula for the effective length coefficient associated with the stress ratios. It is shown that the proposed formula, which was obtained from piecewise linear fitting, improves the consistency and reliability of the prediction of the ultimate strength.

Experimental and numerical study on the stable bearing capacity of steel tubular cross bracing of a transmission tower

Taking the 1000 kV ultra-high voltage (UHV) steel tube transmission tower as the engineering research subject, the ultimate bearing capacity of the X-cross bracing was experimentally studied. The main tube was manufactured together to add the end constraint on the cross bracing used in the design, with six types of X-cross bracing specimens under two horizontal loading cases to study its ultimate bearing capacity and failure mode in the steel tube transmission tower. Under two loading cases as described, the two inclined tubes of the cross bracing are simultaneously compressed. One is in compression, the other is in tension. The magnitude of the force applied to the tubes remain the same. And then, the results show that the bearing capacities of the common U-joint and C-joint cross bracing specimens are low, especially the bearing capacity of the C-joint with diaphragm is insufficient as the inclined tubes of cross bracing is compressed simultaneously, while the bearing capacities of the intersecting joint and the cross-insert joint are excellent under both cases. Moreover, the corresponding ABAQUS finite element model with imperfection was verified using the test results. As a result, the stress distribution, failure mode and ultimate bearing capacity of the numerical simulation are in good agreement with the experimental results, which shows that results obtained from the subsequent numerical analysis are reasonable. The simplified finite element model is used to analyze the bearing capacity of the intersecting joint cross bracing with the different cross positions and the slenderness ratios under two loading cases. For the calculation according to the Technical Specification for Design of Steel Tube Towers for Overhead Transmission Lines, combined with the calculation results from 60 finite element models, the calculation formula of the slenderness ratio correction factor under two loading cases is elaborated. Compared with the existing formula, the improved formula is closer to the finite element calculation results, which helps reduce material waste during the stage of design.

Numerical and experimental performance evaluation of upgraded knee braces under cyclic load

In this paper, the seismic performance of the structure is analyzed by introducing a new angular knee element. Cyclic loads are applied to determine the seismic performance. The result is compared with a vertical knee element. The angular knee element showed better seismic performance as compared to the vertical knee element. The new short knee element studied in two positions including 1- a vertical knee element perpendicular to cross-brace is called VSKE 2- An angular knee element that is called ASKE. Using reduced knee section specimens for better performance. Effect of Angular knee element in knee-braced frames (KBFs) under Cyclic Loading was investigated by testing using a half scale specimen mounted on a reaction frame at two positions including horizontally for VSKE and inclined for ASKE. For experimental tests, specimens were loaded by using a hydraulic actuator. Finite element modelling was used for the simulation of detailed behavior using a verified experiment base model. It has been shown that the performance of knee element fuses can improve the ductile behavior of knee braced frames. Based on the results of vertical and angular cases, it has been shown that an increase of angle between main cross brace and short knee element (incline specimen) can reduce maximum equivalent plastic strain (EPEQ) in the web of knee element fuse.

Influence of the Structure of Lattice Beams on Their Strength Properties.

This paper presents the strength properties of wooden trusses. The proposed solutions may constitute an alternative to currently produced trusses, in cases when posts and cross braces are joined with flanges using punched metal plate fasteners. Glued carpentry joints, although requiring a more complicated manufacturing process, on the one hand promote a more rational utilisation of available structural timber resources, while on the other hand they restrict the use of metal fasteners. The results of the conducted analyses show that the proposed solutions at the current stage of research are characterised by an approx. 30% lower static bending strength compared to trusses manufactured using punched metal plate fasteners. However, these solutions make it possible to produce trusses with load-bearing capacities comparable to that of structural timber of grade C24 and stiffness slightly higher than that of lattice beams manufactured using punched metal plate fasteners. The strength of wooden trusses manufactured in the laboratory ranged from nearly 20 N/mm2 to over 32 N/mm2. Thus, satisfactory primary values for further work were obtained.