Horizontal Restraints Research Articles

Experimental investigation into the in-plane buckling and ultimate resistance of circular steel arches with elastic horizontal and rotational end restraints

This paper presents the experimental and simulation study of circular steel arches attached on the steel columns through the rigid connection, which are loaded to failure under static load. Local buckling of the top flange at the mid-span arch or the bottom flange at end of the arch occurs under the ultimate load. The deformation shape is approximately antisymmetrical with a 0.2 rise-to-span ratio and is symmetrical with a 0.1 rise-to-span ratio. A simplified model is proposed as an arch with elastic horizontal and rotational end restraints. The corresponding stiffness is determined as equivalent horizontal and rotational stiffness at each arch end under the ultimate load. Then a large amount of parameter analysis is conducted to investigate the influence of the elastic supported stiffness, load type, rise-to-span ratio, and slenderness on the ultimate resistance. The finding is that the reduction of the ultimate resistance for the arch with the horizontal and rotational elastic end restraints is maximal under the uniform full-span vertical load, minimal under the concentrated load. Finally, a design method of the steel arch with elastic horizontal and rotational end restraints is proposed taking both ultimate resistance and maximum horizontal displacement of the supports into account for engineering reference.

Analytical study on reinforced concrete frames subject to compressive arch action

Reinforced concrete beams can resist applied vertical loads through the development of compressive arch action (CAA) when adequate horizontal restraints are provided at the ends. However, at the frame level, CAA tends to push adjoining columns outwards and may induce premature flexural or shear failure to the columns. Therefore, under CAA, flexural and shear resistances of the connecting columns need to be examined. This paper describes an analytical study on the behaviour of reinforced concrete frames subject to CAA. In the study, lateral and rotational stiffness of reinforced concrete columns is determined based on a rigid-plastic assumption. CAA of reinforced concrete frames is investigated through an analytical model, in which deformations of columns are taken into consideration. Besides, shear force and bending moment in the column are calculated from equilibrium to shed light on the possible failure mode of columns under CAA. Parametric studies are also conducted to investigate the dominant parameters on the behaviour of columns. Finally, recommendations are provided for the design of reinforced concrete columns against CAA in the connecting beam.

아스팔트콘크리트 궤도용 궤도변위 저항 장치 개발

아스팔트콘크리트 궤도는 아스팔트콘크리트 도상 위에 광폭침목 및 콘크리트 패널이 직결되는 궤도 형식으로서 각종 종 횡방향 외력에 대한 저항력이 요구된다. 따라서 본 논문에서는 광폭침목형 및 콘크리트 패널형 아스팔트콘크리트 궤도에 대해 종 횡방향 저항력 실험을 수행하고 궤도변위 저항 장치에 요구되는 필요 전단 저항력을 산정하였다. 또한 궤도변위 저항 장치로서 콘크리트 블록형 앵커 및 강관형 앵커를 개발하고 각각의 앵커 실험체에 대한 수평전단 실험을 수행하여 앵커 종류별 전단 저항력을 도출하였다. 그리고 아스팔트콘크리트 궤도에 궤도변위 저항 장치 적용 시, 전단 저항 성능 및 경제성 등을 고려하여 궤도변위 저항 장치 적정 개수 및 배치 설계(안)을 제시하였다. Asphalt concrete track (ACT) is a track system connecting wide sleepers and concrete panels on top of an asphalt concrete layer; such a system requires adequate resistance force against various longitudinal and lateral external loads. In this study, a series of experiments were carried out to assess the longitudinal and lateral resistance force of a wide sleeper and concrete panel type ACT. The required shear resistance force of the horizontal displacement restraint device (HDRD) was evaluated. Furthermore, a concrete block type anchor and a steel pipe type anchor were developed as HDRDs. The shear resistance force was decided based on the experimental results of horizontal shear tests for each anchor system. In addition, proper numbers and arrangement design guidelines for the HDRDs were suggested considering the shear resisting capacity and economics for HDRDs applied to ACT.

Numerical investigations on static and dynamic responses of reinforced concrete sub-assemblages under progressive collapse

To study the effect of blast pressure on structural resistance against progressive collapse under column removal scenario induced by contact detonation, and to investigate the development of catenary action within ultra-fast dynamic regime, a physics-based finite element model is developed in this paper. The model is first validated by a quasi-static test series on reinforced concrete sub-assemblages under middle column loss assumption and a blast test series using the same structural configurations. The sub-assemblage included a two-span beam, a middle column stub and two column stubs at both sides. Besides validations with sub-structure tests, some pull-out tests are also performed to verify the numerical models. After the verifications, parametric studies are conducted to investigate the influence of important dynamic and structural factors such as the boundary stiffness, damping ratio, and charge weight attached to the middle column. The study shows that under actual blast conditions, catenary action in sub-assemblages can be mobilised to prevent a structure from collapse even when the bottom longitudinal reinforcement in the bridging beam has already fractured. Moreover, stiffness of horizontal restraints plays an important role to mitigate disproportionate collapse in both static and blast conditions. A comparison is also made between nonlinear dynamic procedure and nonlinear static analysis incorporating simplified energy method for dynamic assessment. It is concluded that the simplified static approach in lieu of dynamic analysis can be considered as a conservative method for practical design purpose. Nonetheless, this method may over-estimate structural resistance if the localised damage is induced by a contact-detonation event.

Horizontally restrained rocking blocks: evaluation of the role of boundary conditions with static and dynamic approaches

The paper deals with the behavior of restrained rocking blocks under seismic actions. Structural or non-structural masonry or r.c. elements, such as building facades or pre-cast panels subjected to out-of-plane modes, may be assimilated to rocking blocks restrained by horizontal springs. Horizontal restraints can represent flexible floors or steel anchorages or any anti-seismic device designed to impede overturning probability. Their effect could improve, in most cases, the dynamic response of blocks in terms of reduction of rotation amplitude. Nevertheless, this effectiveness could vanish or, surprisingly, affect the response in negative way, resulting in overturning when low values of stiffness or one-sided motion in particular conditions are assumed. Two cases of horizontal restraints are analyzed: (1) concentrated restraint as single spring and (2) smeared restraint as spring bed with constant or linearly variable stiffness. The single stabilizing or destabilizing terms of the formulation are here analyzed and commented, providing practical evaluations to obtain enhancement of response in static and dynamic perspective. A numerical example of a masonry facade with non-linear boundary conditions has been provided highlighting how the choice of stiffness values affects the oscillatory motion and rebound effects. Finally, unit stiffness for masonry/concrete walls and retrofitting techniques, such as steel tie-rods, has been calculated.

Behaviour of a two-pinned steel arch at elevated temperatures

Because of their geometrical shape, two-pinned steel arches (TPSAs) have special internal force distributions and deformations compared with conventional straight beams. However, the present studies on TPSAs exposed to fire are still quite limited with regard to their fire-induced deflection modes or deflection limits and ultimate temperatures. This paper employs several numerical models to analyse the high-temperature performance of TPSAs at elevated temperatures in terms of the effects of the load ratios, horizontal restraints, rise-to-span ratios, fire fields and geometrical sizes of the cross-section. The results show that TPSAs exposed to high temperatures are more sensitive to the load ratios than the horizontal restraint stiffness and geometrical size of the cross-section. The TPSAs could not develop catenary actions such as those of straight beams in fire; previous investigations have not predicted the behaviour of TPSAs in fire. The in-plane buckling and excessive mid-span sagging of TPSAs are the final failure modes regardless of the location of the fire actions. To date, the acceptable rise-to-span ratio is approximately 0.25–0.35 for TPSAs in fire. Finally, this paper presents a prediction formula for the limit state of TPSAs at elevated temperatures by using trigonometric functions and logarithmic regression.

Numerical Investigation of Geosynthetic-Reinforced Soil Bridge Abutments under Static Loading

AbstractThis paper presents a numerical investigation of the performance of geosynthetic-reinforced soil (GRS) bridge abutments under static loading conditions. Simulations were conducted using a finite-difference program to model the Founders/Meadows GRS bridge abutment during construction and service. Simulated results are in good agreement with field measurements, including displacements, lateral and vertical earth pressures, and tensile strains and forces in reinforcement. The simulations also indicate that horizontal restraint from the bridge structure has a significant influence on abutment deflections. A parametric study was then conducted to investigate the performance of a single-span full bridge system with two GRS abutments, including effects of bridge contact friction coefficient, backfill soil relative compaction, backfill soil cohesion, reinforcement spacing, reinforcement length, reinforcement stiffness, and bridge load. Results indicate that backfill soil relative compaction, reinforcement...

Experimental study on post repair performance of reinforced concrete beams rehabilitated and strengthened with CFRP sheets. A thesis

Beam is a major structural load transferring Member that support the transverse load which usually rest on support at its ends. According to the revised codes, beams should have been better flexural, shear and torsion strength in addition to the load transferring capacity. It is been a major concern in construction industry in previous many years to increase the strength of the newly constructed beams or already existing beam. The recent researches have led to various innovations in high strengthening of beams due to developments, such as FRP NSMR (near surface mounted reinforcement for concrete structures). Various other materials such as Fibre Reinforced Concrete, Light Weight concrete and High Performance Concrete. The present study examines the shear performance and modes of failure of rectangular simply supported reinforced concrete (RC) beams designed with shear deficiencies. These members were strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets and evaluated in the laboratory. Toward that goal, twelve RC beams were fabricated and strengthened with hybrid FRPs having different combinations of CFRP in shear. The beams were loaded with different magnitudes prior to strengthening in order to investigate the effect of initial loading on the behavior of the rehabilitated beam. Then beams were retrofitted with one layer as well two layers of CFRPs, then the load was increased until the beams reach failure. The experimental results showed that the shear strength of the beams was significantly increased by the CFRP sheet and that it is beneficial to orientate the FRP at 45° to the axis of the beam. The shear strength of FRP strengthened beams is usually calculated by adding individual components of shear resistance from the concrete, steel stirrups and FRP. The series of results indicated that there was considerable increase in shear capacity from 18% to 35% and also provided considerable horizontal restraint.

産業施設を対象とした免震構造の応答特性に関する研究

The nuclear power generation does not produce greenhouse gas. In addition, even an aspect of the generation cost is a superior generation method. However, seismic condition in Japan is severe. Therefore seismic design is important for nuclear power facilities. It is useful to adapt a seismic isolation system into nuclear power facility because the seismic loading can be reduced. Because of improvement of horizontal isolation characteristics and restraint of the cardinal number of laminated rubber bearing, the current laminated rubber bearings are used in the longer period and the high surface pressure. In this case, the stiffness of the laminated rubber bearing in the vertical direction decreases. As the result, the response is increased in natural frequency of the principal components. In this paper, we examined the response acceleration of the principal components in the horizontal/vertical frequency of the laminated rubber bearing. The seismic response analysis with one lumped mass model was carried out. The input seismic waves used Kashiwazaki wave and Onagawa wave. As a result of examination, we confirmed that the response amplification of the principal components of the nuclear power facilities was inhibited by using the laminated rubber bearing with the seismic isolation specification of approximately 20 Hz in the vertical frequency and approximately 2 seconds in the horizontal period.

A buckling model for the stability design of steel columns with intermediate gravity loads

This paper points out an accurate buckling model for determining the flexural effective length of a steel column subjected to intermediate gravity loads, for applications in the 2D second-order elastic analysis based design procedure. The proposed buckling model has “notional” horizontal restraints where equivalent horizontal forces have been applied, and can be readily programmed into a structural analysis/design software. Thirty columns having various end restraints and subjected to concentrated gravity loads within their unsupported lengths are analysed to demonstrate the merits of the proposed buckling model. It is shown that, in most of the cases analysed, the proposed buckling model leads to more liberal column capacities compared to the use of the unity effective length factor or the buckling model described in the European drive-in rack design code. The more liberal capacities are very close to the ultimate loads determined through second-order plastic-zone analysis.

Competition Law and the Rail Market: The Future Liberalization of the EU Rail

How the examples from the liberalization of the UK rail markets and the case law from the ECJ can benefit us to tackle possible inefficiencies, vertical and horizontal restraints, barriers to access and cross-subsidies by States in the implementation of the Railway Packages of the EC, from the competition law perspective.

Comparison between rocking analysis and kinematic analysis for the dynamic out‐of‐plane behavior of masonry walls

SummaryThis paper provides a contribution to the rocking analysis of masonry walls by making a comparison with the kinematic analysis suggested by the Italian code. It is shown that the latter approach is generally over‐conservative and therefore potentially inappropriate for historic buildings, where rehabilitation can be expensive and can affect their cultural value. The equation of motion given by the Housner formulation, corresponding to the movement of a rigid block, is here modified to account for different boundary conditions at different heights of the wall. These boundary conditions or horizontal restraints can represent vaults, transverse walls, or retrofitting devices such as steel tie‐rods. A systemic analysis of walls having different dimensions and slenderness is performed, and the results from the Italian code and rocking analysis are compared. Finally, the improvement in the response offered by retrofitting devices is discussed in terms of reduction of amplitude ratio. Copyright © 2015 John Wiley & Sons, Ltd.

Experimental investigation of reinforced concrete and hybrid fibre reinforced concrete shield tunnel segments subjected to elevated temperature

This paper presents a comprehensive experimental study on the comparative behaviour of the reinforced concrete (RC) and the hybrid fibre reinforced concrete (HFRC) shield TBM (Tunnel Boring Machine) tunnel lining segments exposed to fire. The tests were conducted using a newly developed test facility, which is capable of accommodating different mechanical loading and boundary conditions under different fire scenarios. Six RC segments and six HFRC segments were tested to the standard Eurocode HC (Hydrocarbon) curve, while two reference specimens, one for each type, were tested in ambient environment to provide benchmark data. Apart from the spalling resistance, the fire effects on the structural behaviour were investigated under different boundary conditions at the segment ends, including free sliding (no horizontal constraint), total horizontal restraint and controlled horizontal reaction. The vertical load capacities were investigated for both under-fire and post-fire scenarios. The experimental results revealed excellent spalling resistance in the HFRC segments under thermo-mechanical loading, while the RC segments exhibited better structural performance. A combination of RC design (with flexural reinforcement) and the use of hybrid fibres is deemed to be effective in providing good spalling resistance while at the same time ensuring a robust structural behaviour.

Influence of pallets on the behaviour and design of steel drive-in racks

This paper analyses the influence of horizontal bracing restraints provided by the friction between pallet bases and rail beams on the static behaviour and design of steel drive-in storage racks. The pallet bracing restraints are shown to significantly influence the structural behaviour of the rack, and their effect on the bending moment distribution of the uprights is studied in the paper. The 2D single upright model proposed by Godley is improved in this study by including the restraints provided by the plan flexural stiffness of the rail beams and the friction between the pallets and rail beams. The improved 2D model was found to accurately reproduce the bending moment distributions obtained using 3D advanced finite element analysis. The 2D single upright model is used to analyse 36 drive-in racks under various load case combinations. The paper evaluates the influence of the pallet bracing restraints on the ultimate capacity of drive-in racks, clarifies the loading pattern(s) governing the structural design and determines the friction coefficient, or strength of a restraining device, required to prevent the pallets from sliding. It is shown that while restraints from pallets could potentially be considered in design, they would not lead to more economic structural solutions.

Understanding Behavioral Antitrust

Behavioral antitrust – the application to antitrust analysis of empirical evidence of robust behavioral deviations from strict rationality – is increasingly popular and hotly debated by legal scholars and the enforcement agencies alike. This Article shows, however, that both proponents and opponents of behavioral antitrust frequently and fundamentally misconstrue its methodology, treating concrete empirical phenomena as if they were broad hypothetical assumptions. Because of this fundamental methodological error, scholars often make three classes of mistakes in behavioral antitrust analyses: First, they fail to appreciate the variability and heterogeneity of behavioral phenomena; second, they disregard the concrete ways in which markets, firms, and other institutions both facilitate and inhibit rational behavior by antitrust actors; and, third, they erroneously equate all deviations from standard rationality with harm to competition. After establishing the central role of rationality assumptions in present-day antitrust and reviewing illustrative behavioral analyses across the field – from horizontal and vertical restraints, through monopolization, to merger enforcement practices – the Article examines the three classes of mistakes, their manifestation, and their consequences in antitrust scholarship. It concludes by offering two sets of essential lessons that the behavioral approach already can offer to make antitrust law and policy more realistic and effective in protecting competition: One concerning the value of case-specific evidence in antitrust adjudication and enforcement, the other showing how antitrust law can and should account for systematic and predictable boundedly rational behavior that is neither constant nor uniform.

The Evolving Populisms of Antitrust

Some scholars divide the history of U.S. antitrust law into eras of “populism” and “economics” and assert a fundamental conflict between the two concepts. Generally, the period from the late 1970s to the present is described as economic, and the mid-twentieth century era is labeled populist. A review of Supreme Court antitrust decisions reveals a more complex picture. From the enactment of the Sherman Act in 1890, the Court’s antitrust rulings have officially espoused the protection of non-elite groups from the power of big business – a populist goal – and aimed to advance this objective through economically informed rules. Populism versus economics is a false dichotomy.The populism and economics underlying antitrust jurisprudence have changed over time. In the decades following the passage of the Sherman Act, the Supreme Court often spoke of protecting small producers and displayed, at most, only secondary concern for consumers. The Court in the early era proscribed certain horizontal and vertical restraints but viewed many forms of dominant firm and horizontal conduct more favorably. Starting in the late 1930s, the Court assumed consumer protection as a principal aim of the antitrust laws but continued to champion the cause of small businesses as well. Antitrust economics took a skeptical posture toward many big business practices and treated many forms of horizontal and vertical conduct as inherently problematic. Since the 1970s, the Court has held that the antitrust laws exist only to protect consumers and also adopted the view that most forms of business conduct can benefit consumers.Although some scholars argue that antitrust law should seek to maximize “economic efficiency” and ignore distributional consequences, the courts should continue to interpret the antitrust laws as a consumer protection regime. First and foremost, Congress, as revealed in the legislative histories of the antitrust laws, showed an interest in preventing large firms from using their market power to raise prices and transfer wealth from consumers. The Congressmen that drafted the antitrust statutes showed no awareness of the neoclassical concept of efficiency, let alone an intention to promote it. Second, consumer-oriented antitrust enforcement, in respecting Congressional intent, can prevent regressive wealth transfers from consumers to producers and play an important part in containing growing economic inequality. Third, in light of how consumers often cannot organize politically on account of their vast numbers, the federal courts can serve as trustees for this group and protect its interests from better-organized producer groups. Last, just as antitrust can help consumers, consumers can provide vital popular support for antitrust enforcement.

Digital-image Based Numerical Simulation on Failure Process of High-sulfur Coal

Crushing of high-sulfur coal was important for physical desulfurization, but there were little research on crushing mechanism. This paper combined digital image processing technology and rock failure process analysis system RFPA2D to simulate the failure process of high-sulfur coal in Pu'an of Guizhou under uniaxial compression, and discussed the influence of horizontal restraint, existence and different geometric distribution of pyrite particle on mechanical performance and failure process of high-sulfur coal. The numerical results indicated that without horizontal restraint the compressive strength of high-sulfur coal was lower and monomial dissociation of pyrite particle was more sufficient than that with horizontal restraint. The compressive strength of coal containing pyrite particle was larger than that of pure coal and there was stress concentration in upper and lower pyrite particle during failure process. When pyrite particle distributed in the middle position of a coal sample, the compressive strength was higher than that of the other three positions, but monomial dissociation of pyrite particle was more sufficient than that of the other three positions, and this was beneficial to the following desulfurization operation. The study had certain reference value for crushing mechanism, crushing process design, selection of breaking equipment and energy saving and consumption reduction. DOI: http://dx.doi.org/10.11591/telkomnika.v11i1.1889

Experimental Study and Application of the Different Waste Rock Compaction Characteristics Filled in Roadside of Gob-Side Entry Retaining

Stress-strain relationship of waste body under different side pressures, water contents and particle fractions are investigated in this paper. The bearing features of waste filled body of entry retaining besides gob-side entry retaining are: (1) filling waste gob-side entry retaining requires adequate horizontal restraint; (2) gangue water content has little effect on filling body intensity and waste in natural water content state can be used to fill in gob-side entry retaining; (3) stress and -strain relationship of waste body (grain size ranges from 0 to 10mm) is nonlinear. The bearing capacity can meet the requirement of beside gob-side entry retaining support. Based on above experimental results, the industrial roadway retained experiment is successful. The research results provide theory design basis for wide application.

Head Restraint Backset During Routine Automobile Driving: Drivers Usually Exceed the Recommended Guidelines

Objective: Although several previous studies have evaluated horizontal head restraint backset distances, few studies have evaluated them during driving. The purpose of this study was to measure this backset during routine automobile driving and to specifically evaluate the backset during individual driving tasks such as turning, stopping, starting, and lane changes. Methods: Fourteen subjects drove around a specified route through the city of Guelph, Ontario, Canada, that included residential, thruway, and highway driving; additional minor driving tasks, such as lane changes, were evaluated. The distance of head restraint to posterior aspect of the head was measured continuously throughout the drive using an ultrasonic measurement system. The timing of specific tasks was documented using a video camera. Results: The average head-to-restraint distance throughout the driving route was 78.1 mm (standard deviation [SD] 24.8 mm); this distance did not vary significantly between the global measures during various driving areas (residential, thruway, and highway). We observed that the head restraint backsets during right turns (93.6 mm; SD 34.8 mm) were significantly larger compared to the other driving tasks (p < .001). The 7 males and 7 females showed similar backset distances: 84.52 mm (SD 12.08) and 71.68 mm (SD 5.53), respectively (p = .0785). Conclusions: We observed that most subjects maintain a relatively consistent head-to-restraint distance throughout their driving route; 2 subjects adopted very large head restraint backset distances throughout their drive and 2 others adopted very small head restraint backset distances—this appears to reflect driver posture. Twelve of 14 subjects had average backset distances that exceed the National Highway Traffic Safety Administration and the Federal Motor Vehicle Safety Standard guidelines, indicating that most drivers may be at risk for whiplash-like disorders if exposed to a rear impact while driving. Of the monitored driving tasks, turning, especially right turns, caused drivers to increase their head-to-restraint backset distance.

Boundary Condition Updating of Bridge Structure Based on Mode Parameters

According to the complex boundary condition of real bridge structure, appendix restraint parameters of structure boundary condition were detailed analyzed. The appendix horizontal and torsional restraint parameters were selected as research object. The least square constrained optimization inversion method was used to establish the question of reverse of bridge structure boundary appendix parameters based on tested and calculated mode parameters. The first order perturbation of eigen-value and eigen-vector based on matrix perturbation theory were substituted into the constrained optimization inversion equation, so the solving efficiency was improved greatly, and the iteration method was used to improve the precision. The corresponding program was made, and the example of a maglev railway girder shows that fairly well precise bridge structure boundary appendix parameters can be reserved with only former several modes parameters through four to seven times of iteration calculation.