Restraint Capacity Research Articles

Experimental, numerical simulation and design methodology of axial compression performance of combined steel columns for modular buildings

Load-supporting columns of modular buildings are their key load-bearing components, but fewer research studies have been conducted so far. To investigate the effects of initial defects of components, bolt-hole sizes, end stiffness, and component slenderness ratios on the axial compressive performance of load-supporting columns, this paper carries out a full-scale modeling experimental study and parametric finite element analysis. Subsequently, the test and finite element results were compared with the predicted results of the specifications in China (GB 50017-2017), the United States (ANSI/AISC 360-22), and Australia (AS 4100-2020) to assess the appropriateness of the specifications. The results show: It is recommended that small-section high-strength bolts be used to connect the load-supporting columns. When the overall and local defect magnitude meets the accuracy requirements, the magnitude size has little effect on the component bearing capacity. The direction of the overall bending defect has little effect on the initial stiffness and peak load-carrying capacity of the steel tube spandrel column. When the regularized slenderness ratio of the components is less than 0.4, the reduction of the hinged restraint capacity is less than 10% compared with that of the stiffened restraint capacity. The Chinese specification can be used for component design and its predictions are on the conservative side. As the section width-to-thickness ratio becomes larger, the predictions of the U.S. specification change from an accurate prediction to one with too large an error. The Australian specification predictions were all on the unsafe side, but most components had errors of 10% or less. The results of this paper help to promote the development of modular building technology.

Mechanical performances of thin-walled high-strength concrete-filled steel tube square columns with high-strength reinforced cages under biaxial eccentric compression

In the current research that both steel tube and concrete use high-strength materials, there are few studies on the small wall thickness of steel tube exceeding the standard. In order to make full use of the mechanical properties of high-strength steel and enhance its restraint ability on concrete, this paper designs a steel cage dominated by transverse steel bars. A total of 15 square high-strength steel tube high-strength concrete medium-long column test pieces are tested and studied. The main parameters of the specimens are slenderness ratio, loading eccentricity and the form of internal steel reinforcement cage. After the loading test, according to the test results, the failure mode of the specimen is obtained and the mechanical properties of middle-long concrete-filled steel tubular columns are analyzed. The research results show that the ultra-thin high-strength steel pipe can restrain concrete well, but with the increase of eccentricity, its restraint capacity is slightly insufficient; the built-in steel cage can slow down the bulging of the specimen and help the steel pipe to further strengthen the restraint on concrete, but the steel cage as an indirect constraint cannot avoid the final bulging damage. Due to the existing formula overestimating the effect of ultra-thin steel tubes, this paper proposes a calculation formula for the axial compression of thin-walled high-strength concrete-filled steel tubes with steel cage short columns. Based on this method, the bearing capacity of medium-long columns under biaxial eccentric compression is calculated with good accuracy.

Mechanical Property of Lateral Piles for Pile Composite Foundation Loaded by Model Test

Under vertical load, the composite foundation may be damaged due to insufficient lateral restraint capacity. If the lateral restraint pile is added to the edge of the composite foundation, the lateral stability can be effectively enhanced. This new reinforcement scheme is called a combined composite foundation. For the combined composite foundation, the lateral restraint piles will bear a certain force when the composite foundation is loaded, and the force may cause the piles horizontal displacement, instability, or even failure. After preload on the composite foundation, the mechanical behavior of lateral restraint piles will be more sophisticated. To study the mechanical behavior of lateral restraint piles under such condition, a laboratory model test was conducted. The results are suggested as follows: Axial force distribution curves tend to be “S” shape with two peak values at the upper and lower parts, respectively. The negative axial force is distributed at the upper part, and the positive axial force is distributed at the lower part. The bending moment and lateral soil pressure distribution of piles appear with the regularity of “increase-decrease” along the depth. Such a phenomenon is associated with the expansion of a potential slip surface. In accordance with the relative location of the potential slide surface and the piles, the lateral restraint piles can fall into three sections. Different sections get different stresses. The reinforcement scopes have an impact on the stress of different lateral restraint piles. With the increase of the reinforcement scope, the axial force, soil pressure, and bending moment show the regularity of increase. The values of axial force, the lateral soil pressure, and the bending moment increase with load growth and become stable when the load is larger than 60 kN. This is associated with the piles in the composite foundation, which verifies the reinforcement effect to prevent the soil slide and the foundation deformation.

ACL Research Retreat IX Summary Statement: The Pediatric Athlete, March 17-19, 2022; High Point, North Carolina.

ACL Research Retreat IX Summary Statement: The Pediatric Athlete, March 17-19, 2022; High Point, North Carolina.

Study of bond-slip performance and ultimate bearing capacity calculation under static and reciprocating action of folded perfobond shear keys

The PBL (Perfobond Leiste) shear key has advantages such as high load capacity and high restraint capacity. However, at the same time, there are also problems such as insufficient deformation capacity and low stiffness along the weak axis direction. In addition, shear key performance degradation, ductility, and other problems are not yet clear under the reciprocal seismic action. To this end, a folded perfobond shear key is proposed in this paper to solve the problems of insufficient deformation capacity and uneven stiffness distribution of the traditional PBL shear key. At the same time, numerical analysis is carried out to investigate the seismic performance of the shear key under earthquakes, such as stiffness degradation, ductility, and energy dissipation. Through the push-out test, it is found that the steel plate outside the shear key deforms, showing a certain semi-rigid characteristic; concrete forms a trapezoidal constraint area centered on shear keys, and the constraint effect is significantly improved compared with the point constraint of studs. On the whole, under the condition of a similar shear section, the bearing capacity of the shear key is 1.5 times that of the stud. The ductility coefficient is above 3.0, showing good deformation ability. Through parameter analysis, it is found that the bearing capacity of shear keys increases with the increase of web width-thickness ratio, but the deformation capacity degenerates. The opening rate mainly affects the embedded effect of shear keys and concrete. Based on the fitting analysis, the variation laws of web width influence coefficient γB, web height influence coefficient γH, and embedded effect influence coefficient γD are obtained, and the calculation formula of shear key bearing capacity is proposed. Finally, based on the push-out test, the hysteretic behavior of the shear key is studied. It is found that the load-displacement hysteretic curve of the shear key is full, the ductility coefficient is 4.2, and the equivalent viscous damping coefficient is 0.27, which shows good seismic capacity. In summary, the new shear key realizes the good unity of bearing capacity and deformation and has high engineering application value.

Investigation of intrinsic de-bonding in bonded concrete overlays: Material characterisation and numerical Study

© 2018 Growing Science Ltd. All rights reserved. This study investigates the evolution of intrinsic interfacial de-bonding of Roller Compacted Steel Fibre Reinforced Polymer Modified Concrete (RC-SFR-PMC) bonded on substrate Ordinary Portland Cement Concrete (OPCC), using both experimental and numerical techniques. The relative effects of evolving material inhomogeneity and composite dimensional stability during curing was studied as a function of overlay structural scale, using a 2D plane strain Interface Cohesive Zone Model (ICZM). The effects of creep coefficient on interface restraint capacity and ensuing cohesive zone length were clearly evaluated. The results showed that the applied curvature due to the measured shrinkage strain was inadequate to cause critical de-bonding. In the FEA results, while the rate of interface energy release generally varies as a function of the bi-material relative stiffness and overlay structural scale, it is also evident that the two variables lose effects as the overlay structural scale approaches 0.50. The overall indicative trend shows that the rate of energy release in compliant overlay when relative stiffness (α0. Therefore, a more compliant overlay typically exhibits less relative restraint to bending induced de-bonding.

Recovery length of high strength tapes in damaged flexible pipes

The application of filaments wound around damaged high strength tapes (HSTs) in flexible pipes may be one of the simplest methods to reestablish the initial restraint capacity for the armor wires. This paper aims at evaluating the effectiveness of such method observing the recovery length of filaments and investigating the mechanical behavior of both perfect and damaged HSTs. Analytical formulations that depict the restraint ability of undamaged HSTs are derived from a combination of Clebsch–Kirchhoff equilibrium equations and a modified non-linear friction law in terms of normal stress. As a base case, the restraint ability induced by the interaction between original damaged HSTs and filaments is obtained as well as the required recovery length. The solution is presented in non-dimensional form and it is shown that the repair method is feasible. Besides, some important parameters affecting the recovery length are investigated. It is found that the application of tension force at both ends of filament is the most effective way to reduce the recovery length. It is also shown that external pressure has insignificant effect if tension forces at ends are large. In addition, a case study shows that the recovery length grows almost linearly with the increasing radius of tape.

Research on Stability Bearing Capacity for Pole and Tower Compression Members with Two Legs Connection

In order to research the stability bearing capacity of high strength pole and tower compression members, analytical method and numerical simulation method were used to study stability on high strength axial compression members. Researched the impact of different slenderness ratio, different cross-section factors on the bearing capacity; energy relationship was using in analytical method, the boundary conditions issue is simplified according to different end restraint capacity; the failure modes and stability bearing capacity of members were studied by numerical simulation. Compared with the experimental results show that the numerical simulation and elastic theory analytical solution overestimate the capacity of members, but the numerical results have better agreement than the elastic theory analytical solution, which can show the numerical simulation method is right. Experiment method can obtain more secure mechanical behavior of high-strength angle steel member with axial loading.

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Stability Bearing Capacity Analysis for High-Strength Angle Steel Members with an Eccentric Load at One End

Single-angle compression members with an eccentric load at one end were widely used in transmission towers, analyzing the stability bearing capacity become a very complex issue due to end restraint conditions and the impact of defects. Experiment method and analytical method were used to study the size of the stability capacity on four kinds of members, analytical method use energy relationship, the boundary conditions issue is simplified according to different end restraint capacity, and finally discuss the theoretical ultimate bearing capacity of the test members. Compared with the experimental results show that the elastic theory analytical solution overestimates the capacity of members, using experiment method can obtain more secure mechanical behavior of high-strength angle steel member with an eccentric load at one end.

Dynamic Restraint Capacity of the Hamstring Muscles Has Important Functional Implications After Anterior Cruciate Ligament Injury and Anterior Cruciate Ligament Reconstruction

Bryant AL, Creaby MW, Newton RU, Steele JR. Dynamic restraint capacity of the hamstring muscles has important functional implications after anterior cruciate ligament injury and anterior cruciate ligament reconstruction. Objective The purpose of this study was to investigate the relation between knee functionality of anterior cruciate ligament deficient (ACLD) and anterior cruciate ligament reconstruction (ACLR) patients and hamstring antagonist torque generated during resisted knee extension. Design Cross-sectional. Setting Laboratory based. Participants Male ACLD subjects (n=10) (18–35y) and 27 matched males who had undergone ACLR (14 patella tendon [PT] grafts and 13 combined semitendinosus/gracilis tendon grafts). Interventions Not applicable. Main Outcome Measures Knee functionality was rated (0- to 100-point scale) by using the Cincinnati Knee Rating System. Using electromyography data from the semitendinosus (ST) and biceps femoris muscles, we created a mathematical model to estimate the opposing torque generated by the hamstrings during isokinetic knee extension in 10° intervals from 80° to 10° knee flexion. Results Pearson product-moment correlations revealed that more functional ACLD subjects generated significantly ( P<.05) higher hamstring antagonist torque throughout knee extension. In contrast, more functional PT subjects produced significantly lower hamstring antagonist torque at 80° to 70° knee flexion, whereas no significant associations were found between hamstring antagonist torque and knee functionality for the ST/gracilis tendon subjects. Conclusions An increased hamstring antagonist torque generated by the more functional ACLD subjects, reflective of increased hamstring contractile force, is thought to represent a protective mechanism to compensate for mechanical instability. The restoration of anterior knee stability through ACLR negates the need for augmented hamstring antagonist torque.

Advanced smart airbags: The solution for real-life safety?

Today, numerical simulation is used all over the world to develop and optimise the restraint system performance. But more than just helping engineers to design restraint systems fulfilling the homologation and ratings requirements, the numerical simulation enables them to extend their field of investigation by going beyond the laboratory test conditions, making their first steps in “real life safety”. This paper presents the simulation of a concept of an adaptive restraint system for the passenger side. Its restraint capacity is continuously adjustable to the occupant, by an airbag whose shape and volume can be varied. In addition to this, the airbag outflow hole characteristics have also been optimised. The performance of this restraint system has been evaluated using the three standard adult dummies (5th, 50th and 95th percentile), each one in various seating positions for both US and Euro-NCAP pulses. The results will be shown with respect to a state-of-the-art restraint system. The design process, starting from the 95th percentile dummy, will be explained as well as the problems encountered during the optimisation process.

火災加熱を受ける鋼架構の構造安定性

Overall instabilities of locally heated steel frames are processes indicated by snap-through phenomena. A way of analysis of such unstable process has been developed and the resulting solutions have clarified realistically the ultimate states as well as failure modes of steel frames subjected to fire. The ultimate temperature of a frame under fire does not always coincide with the one at which a local failure such as column buckling takes place. The larger restraint capacity of the neighboring members leads to the higher frame ultimate temperature owing to their stress redistribution abilities. Carrying vertical load, a hat truss installed into the top floor adds definitely redundancy to the frame.

Restraint Effectiveness in Unbonded Tendons for Prestressed Masonry

Currently, the Masonry Standards Joint Committee does not provide any guidance on the design of intermittent restraint systems. Posttensioned masonry is most cost-effective when the amount of restraint necessary to provide adequate performance is minimized. This paper presents an analytical approach to determining the force transferred between the restraint and the tendon. In addition, experimental results of component testing on restraints are presented. Specimens tested include restraints formed by filling cells with mortar and grout as well as the use of a bar positioner. Analytical methods to predict the restraint capacity are also presented and compared with the results of the component testing. Finally, design provisions are suggested along with a design example problem.

Pipe Whip—Bounding the Required Restraint Capacity

Energy balance methods commonly in use for the design of pipe whip restraints are based on the solution for the motion of a rigid-plastic pipe before impact against the restraint, with the assumption that after impact, the whipping portion of the pipe continues to rotate about the plastic hinge location determined for conditions before impact. Such energy balance methods are not necessarily conservative because: 1) the plastic hinge which forms in the pipe moves after impact on the restraint; and 2) elastic pipe deformations are not considered. Here, upper and lower bounds to the required restraint capacity are derived. In contrast to finite element methods, which are very time-consuming, the upper and lower bounds can be evaluated by simple hand calculations. Another advantage is that the required restraint capacity is calculated directly. No trial and error design is required. A numerical example shows that for a typical pipe and restraint, the upper and lower bounds differ by as little as 20 percent.