Equal Spans Research Articles

The EU Commission During the Covid‐19 Crisis: Attempts at Self‐Empowerment, or Not?

AbstractWe argue that the European Commission, like national governments, is likely to have used the Covid‐19 crisis as an opportunity to bolster its own powers. We focus on the Commission's attempts to insert into legal proposals provisions to adopt delegated or implementing acts, as this is the only possible way to gain lasting rule‐making powers. We analyse all the Commission's legal proposals for an equal time span before and after the start of the Covid‐19 crisis and study whether the number of proposed delegation provisions has changed after the onset of the crisis. The analysis, to our surprise, does not show any clear evidence of a self‐empowerment strategy. In the conclusion, we discuss likely explanations for this non‐finding.

Effects of Soft Story Locations on the Nonlinear Time History Analysis of Multistory Reinforced Concrete Buildings

Abstract The current paper included studying the effects of soft storey locations on dynamic response of reinforced concrete (RC) buildings under the impacts of earthquakes. Soft storey is essential to provide the building with a functional space such as vehicle garages or open meeting rooms. Further analytical investigation was necessary to understand the impact of these flexible floors on the building's response during earthquakes, as conducting experimental research to address this issue is highly difficult. The research encompassed the effects of soft storey location in two types of buildings, one with equal spans and the other with unequal spans, on the nonlinear time history response. Each building consists of a 10-stories (G+9) RC residential structure subjected to earthquake effects. The analysis was carried out using program sap2000 v23. An analogous diagonal strut was used to illustrate the infill panels. The study included the effect of soft storeys on the natural period, the change in base shear with time, and the change of displacement and acceleration along time for each building. The obtained results showed that including a soft storey in the analysis for buildings having either equal or unequal spans increased the time period, displacement, and storey drift, causing a decrease in the acceleration and base shear forces. Building with the soft storey on the fifth floor (at the mid-height of the building) showed a better dynamic response compared with that using the soft storey on the ground and last floors.

Flexural Strength of RC Continuous Beams Strengthened by CFRP Using EBR and EBROG Methods: Experimental and Analytical Study

Abstract Recently, a new proposed technique named; Externally Bonded Reinforcement on Grooves (EBROG) has been presented as a strengthening method to postpone or eliminate the undesirable debonding failure mode that is accompanying to Externally Bonded Reinforcement (EBR) method. This paper introduces an experimental and analytical study to evaluate the validity and accuracy of the formulas that were introduced by the standard codes and researchers, in estimating the ultimate load of RC continuous beams strengthened with carbon fiber reinforced polymer (CFRP) sheets in flexure. The experimental program includes testing of ten RC beams with cross section of (200×130) mm and two equal spans, each span has a 1050 mm length. The comparison between the ultimate load collected from the test results and that predicted using ten different analytical models is conducted. It is found that the ACI 440.2R-17 and most of other analytical models well predicted the ultimate load of RC beams strengthening with one layer of CFRP sheets using EBR, but most of these models significantly underestimate the ultimate load of tested beams that were strengthened using EBROG method. ACI, Shehata el. al., and Teng et al. models give close predicted load to the experimental results in case of EBR beams strengthened with two layers.

Large deformation assessment of three-tower suspension bridges: An enhanced analytical model and solution algorithm

An enhanced nonlinear approach is proposed in this study to address the limitations of traditional deflection theory in analyzing large deformations of three-tower suspension bridges. In this approach, the three-tower suspension bridge is simplified as two quasi-independent bridges for analysis, and detailed considerations are given to the vertical and longitudinal deformations of the main cable, which produce the expression for the relationship between the cable's internal force and deformations. By employing the complementary energy principle and variational calculus, the nonlinear differential equations describing bridge deformations are then established. To ensure the displacement continuity at the middle tower, this paper proposes the use of Chebyshev polynomials to approximate the solutions of the differential equations, and the weighted residual method is then used to transform these differential equations into algebraic equations. On this basis, the developed nonlinear adjustment optimization algorithm enables efficient solving of the nonlinear equation and thus determination of bridge deformation under various load conditions. The accuracy and effectiveness of the proposed scheme are validated through the analysis of two suspension bridges with equal and unequal spans. Finally, the extended applications of the proposed scheme on the other type of multi-span suspension bridges are introduced for further applications.

Analyzing Social Media And Traditional Media Coverage Of Elections 2018 In Pakistan

The study has been designed to investigate the social media and traditional media coverage of elections 2018 in Pakistan. For social media, X (formerly Known as Twitter)) was selected and for traditional media, Geo News and Dawn Newspaper were selected. The media coverage of the selected media was examined from 2nd July 2018 to 25th July 2018 in four equal time spans. The study uses agenda setting as a theoretical frame. Using content analysis, the study addresses research questions regarding first-level agenda-setting. The results indicated that the issue agendas of X, Geo News, and Dawn were similar during the elections 2018 in Pakistan.

Resonance reduction for linked train cars moving on multiple simply supported bridges

The dynamic interaction of a moving train over a series of railway bridges with equal spans can result in a coupled vibration problem of wave transmission between two periodic structures. Dual resonance occurs when both systems vibrate in phase and the train travels at a resonant speed. The objectives of this paper are to (1) develop an active pitching resonator (APR) to attenuate resonance waves in a train; (2) study the dispersion relation for pitching motion control of periodically linked train cars; (3) investigate the key parameters that affect the dispersion band gaps of wave attenuation in a train; (4) present an active vibration cancellation method to enhance the control performance of the APR; and (5) demonstrate the effectiveness of using the optimal APRs to reduce resonance of a moving train. Through dispersion analysis, the optimum APR can not only shift the target frequency level away from resonance of a moving train, but also create a wide resonance band gap to reduce wave transmission in the train. Finally, the effectiveness of the optimum APR unit in reducing the resonance and attenuating the waves of a train travelling over multiple-span simple beams is demonstrated by dynamic finite element analysis of the train-bridge interaction.

Effect of Concrete Strength on Shear Capacity of Reinforced High-Strength Concrete Continuous Beams without Web Reinforcements

In order to evaluate the shear strength and behavior of high-strength concrete beams without web reinforcing, eight high-strength continuous concrete beams with cross sections of 200 mm by 300 mm were cast and tested to failure. The ultimate load-carrying capability and shear behavior are presented. The applicability of the Sudheer et al. equations and ACI 318M-14 is examined. In addition, the effects of the compressive strength ( f c ′ ) and shear span to effective depth ratio (a/d) on the shear strength and behavior of HSRC beams without stirrups are also studied. 63 MPa, 78.8 MPa, 85.9 MPa, and 92 MPa were the concrete’s compressive strengths, while 2.41 and 3.33 were its shear span to effective depth ratios. There were two equal spans of continuous beams, and at each span, they were evaluated under a single-point load. It was found that with increasing compressive strength, the failure load was increased. But the deflection did not affect it significantly. While increasing, (a/d) led to a decrease in failure load but increased deflection. It was also found that both ACI 318 M-14 and Sudheer et al. equation were more conservative.

Blind competition on the numerical simulation of continuous shallow steel‐fiber reinforced concrete beams failing in bending

AbstractThis article describes the second blind simulation competition (BSC) organized by the fib WG 2.4.1, which aims to assess the predictive performance of models based on the finite element method (FEM) for the analysis and design of fiber reinforced concrete (FRC) structures. Slabs supported on columns or piles have becoming competitive applications for FRC due to the technical and economic benefits may be obtained by combining properly the fiber reinforcement mechanisms to those provided by conventional reinforcement placed, as a strip, in the alignment of columns/piles. Therefore, a representative zone of this structural system, namely a hybrid fiber reinforced concrete (R/FRC) shallow beam, is chosen in this BSC to show the potentialities of FRC in these types of applications, as well as to assess the predictive performance of FEM‐based computational models on the design verification at serviceability and at ultimate limit state conditions (SLS and ULS, respectively). Two statically indeterminate shallow beams of two equal spans were tested up to their failure, by recording the applied loads, the strains in the conventional reinforcements and in the FRC of the critical zones of the structure. By using digital image correlation, the average crack width at the level of the flexural reinforcements was recorded. The participants had to predict these results by receiving information about the mechanical properties of the materials, the geometry of the prototypes and their loading and support conditions. In this article, the rules and the results of this 2nd BSC competition are presented, and the data obtained experimentally is thoroughly analyzed.

Lasting Effects of COVID-19 Pandemic on Prehospital Emergency Medical Service Missions.

The COVID-19 pandemic confronted prehospital emergency medical services (PHEMS) with immense challenges. This study aimed to investigate the development of PHEMS mission numbers and times in the COVID-affected region of Southwest Saxony (SWS). This was a retrospective analysis of PHEMS in SWS during lockdown periods and equal time spans in the previous and following years. Differences were tested for statistical significance using the chi-squared test and one-way analysis of variance (ANOVA). The total number of missions showed a substantial drop during the first (-16.6%) and the second (-4.5%) lockdown period compared with the previous year. Next-year periods showed a recovery that was nearly equivalent to the starting point. The first lockdown period was not associated with longer overall mission times. The minutes spent at the scene differed significantly between the first lockdown period (31.1 ± 3.52 min), previous year (28.4 ± 4.84 min), and follow-up period (31.8 ± 0.98 min). During the second lockdown, the overall mission times (71.6 ± 2.91 min), response times in minutes (8.9 ± 0.49 min), and minutes spent at the scene (31.4 ± 2.99 min) were significantly longer. The minutes spent at the scene (32.3 ± 18.68 min) and the overall mission time (69.6 ± 1.92 min) remained significantly longer during the control period. Our data confirm the impact of the SARS-CoV-2 pandemic on German PHEMS. It can be concluded that nationwide lockdown measures led to lasting effects regarding a reduction in the total mission number, transport-on-site released-ratio, and emergency time intervals in the following year, without lockdown restrictions. The lasting effects on the transport-on-site released-ratio and emergency time intervals call for a re-evaluation of the delivery of emergency services during pandemics. These findings can inform future policy decisions and resource allocations to ensure optimal emergency medical services.

Formulation and characterization of lamotrigine nasal insert targeted brain for enhanced epilepsy treatment

Lamotrigine. (LMT) is a triazine drug has an antiepileptic effect but with low water solubility, dissolution rate and thus therapeutic effect. Spanlastics are nano-vesicular carriers’ act as site-specific drug delivery system. Intranasal route could direct the drug from nose to brain and provide a faster and more specific therapeutic effect. Therefore, this study aimed to upload lamotrigine onto nano-vesicles using spanlastic nasal insert delivery for effective epilepsy treatment via overcoming lamotrigine’s low solubility and improving its bioavailability. Lamtrigine-loaded nano-spanlastic vesicles were prepared by ethanol injection method. To study different formulation factor’s effect on formulations characters; particle size (PS), Zeta potential (ZP), polydispersity index (PDI), entrapment efficiency percentage (EE%) and LMT released amount after 6 h (Q6h); 2^1 and 3^1 full factorial designs were employed. Optimized formula was loaded in lyophilized nasal inserts formulation which were characterized for LMT release and mucoadhesion. Pharmacokinetics studies in plasma and brain were performed on rats to investigate drug targeting efficiency. The optimal nano-spanlastic formulation (F4; containing equal Span 60 amount (100 mg) and edge activator; Tween 80) exhibited nano PS (174.2 nm), high EE% (92.75%), and Q6h > 80%. The prepared nasal inserts (S4) containing 100 mg HPMC has a higher mucoadhesive force (9319.5 dyne/cm2) and dissolution rate (> 80% within 10 min) for rapid in vivo bio-distribution. In vivo studies showed considerable improvement brain and plasma’s rate and extent absorption after intranasal administration indicating a high brain targeting efficiency. The results achieved indicate that nano-spanlastic nasal-inserts offer a promising LMT brain targeting in order to maximize its antiepileptic effect.

Three-dimensional transition in the wake of two tandem rotating cylinders

Three-dimensional (3-D) transition in the wake of two tandem co-rotating cylinders is studied numerically for Reynolds numbers $180\le Re\le 500$ . Infinite cylinders of equal diameter ( $D$ ) and span ( $8D$ ) are placed at streamwise gaps $Lx=2.5D$ and $7.5D$ , and rotated at rotation rates $\alpha =0$ , $0.5$ , $1$ and $2$ . For $\alpha =0$ and $Lx=7.5D$ , 3-D transition in the wake of the upstream cylinder resembles that for an isolated cylinder with the formation of Mode-A and Mode-B instabilities, whereas for the downstream cylinder, only Mode-A instability occurs in both the $Lx=2.5D$ and $7.5D$ cases with $\alpha =0$ . When the cylinders rotate at $\alpha =1$ for $Lx=7.5D$ , staggered transition takes place with the appearance of only Mode-B and only Mode-A instabilities in the near-wake regions of the upstream and downstream bodies, respectively. In the case $Lx=2.5D$ , the wake of the rotating cylinders transitions via Mode-C and Mode-D instabilities for $\alpha =0.5$ , Mode-D and Mode-D $^\prime$ for $\alpha =1$ , and Mode-C and Mode-A for $\alpha =2$ . A sudden decrease in near-wake fluctuations, accompanied by a downward jump in the force coefficients, is observed as the 3-D instability shifts from one mode to another, for $\alpha \ge 1$ and $Lx=2.5D$ . This discontinuity is caused by the formation of a pair of opposite-signed recirculation zones that mitigate each other's effects in the near-wake region.

Quasi-Static Influence Line Identification and Damage Identification of Equal-Span Bridges Based on Measured Vehicle-Induced Deflection

The bridge influence line (IL) reflects the response of a certain section due to varying load positions. As a result, IL has a wide application prospect in damage identification and condition assessment. Up to date, studies regarding IL have been focused on the structure condition evaluation. A feasible and practical method for damage identification is still not yet available. The present paper proposes a comprehensive damage identification methodology based on IL under a moving vehicle is composed of data pre-processing, IL extraction, and damage detection. Firstly, a thorough review of existing IL identification methods based on signal processing is provided. Then three quasi-static IL identification methods based on measured data are discussed. Consequently, the study proposes a two-stage damage identification approach for simply supported bridges with equal span length. Also, the effectiveness of this approach is verified through field tests on a real girder bridge. At last, conclusions are drawn, and potential issues for the application of the proposed method in practice are discussed.

Study on Dynamic Characteristics of an Improved Composite Box Girder with Corrugated Steel Webs

Composite box girders with corrugated steel webs (CBGCSWs) are used worldwide owing to their light self-weight, high efficiency of prestressing application, and reasonable distribution of shear force and bending moment. An improved composite box girder with corrugated steel webs (ICBGCSWs) has been recently introduced to further reduce the dead weight and improve its durability. Because the innovative ICBGCSW has emerged as a new structure, very few studies have been conducted on its dynamic characteristics. In the present study, a theoretical analysis was first conducted. By comprehensively considering the shear lag effect and the shear deformation of CSWs, the element stiffness matrix of ICBGCSW was derived based on the principle of stationary potential energy. The natural frequencies and mode shapes in vertical bending vibration were calculated via a self-developed software program. The proposed method was verified by comparing the results with finite-element analysis and experimental results. Then, sensitivity studies were performed to investigate the influences of the shear lag and shear deformation on the natural frequencies of vertical bending vibration. Finally, vibration frequencies of the continuous ICBGCSW were calculated, and a general formula for calculating the fundamental frequency of simply supported girders, continuous girders with equal spans, and continuous girders with unequal spans was proposed. The proposed method, being able to consider both the effects of shear lag and shear deformation of the box girder, delivered very good performance in studying the dynamic characteristics of the ICBGCSW, whereas the proposed general formula of fundamental frequency could serve as a good reference for the bridge design in practice.

Effects of Floor System on Progressive Collapse Behavior of RC Frame Sub-Assemblages

The ability to predict the resistance of reinforced concrete (RC) structures to progressive collapse as a result of an interior column removal has become a need in structural design. In general, three resistance mechanisms characterize the structure resistance to progressive collapse, flexural action, compressive arch action, and tension catenary action. The objective of this study is to investigate the effects of floor system configurations on the progressive collapse-resistance of RC frame sub-assemblages and the amount of energy dissipated in each resistance mechanism. This investigation employs a fiber element-based modeling technique to present findings into the effects of beam size and reinforcement details on the progressive collapse-resistance and energy dissipation of RC beam-column sub-assemblages with four equal spans. Three different span lengths of 5, 6, and 7 m were considered. A total of 38 floor system designs for gravity loads were performed in accordance with the ACI 318-14 design code. The modeling technique employed in this study was validated and utilized by the authors in previously published works. The study shows that beam size and the presence of slab are critical as they significantly affect the energy dissipation and progressive collapse-resistance and failure pattern of the sub-assemblage frames. Moreover, the presence of a slab was found to increase the energy dissipation by around 28%.

In situ ground settlement sensor for oil-tank monitoring by combining a fiber-optic low-coherent interferometry with a fine mechanical design.

An in situ robust ground settlement (IR-GS) sensor was designed to meet the requirements for oil-tank health monitoring by combining a low-coherent fiber-optic interferometry with a fine mechanical spline shaft. A floating mirror was mounted on the shaft and moved up and down along with the liquid surface. The liquid-contained chambers were hydraulically connected at the bottom by using a liquid-filled tube. The liquid level inside each chamber was initially at equal level. One of the chambers was fixed on a steady ground point, which was chosen in a surveying point of view and served as a reference. The others were distributed around an oil tank and separated the tank's perimeter into eight equal spans. Thereby, the health states of the oil tank were able to be evaluated based on these sensing results. Interrogation of the sensor was employed via a low-coherent fiber-optic Michelson interferometer. One path of the interferometer was composed by the floating mirror, whereupon a light was reflected. The other path was projected to a mirror that was fixed on a stepping motor. Therefore, the corresponding liquid level could be optically surveyed. Differential settlements between each chamber and the reference served as a measure of how much the liquid level was changed from its initials. Experimental tests demonstrated that this IR-GS design, with the optimized shape and weights of the spline shaft, could overcome the error caused by dust, hysteresis, temperature, etc. and meet the practical requirement in the accuracy of ±0.5mm. A practical application was carried out, and its long-term stability has been proved.

Experimental and numerical investigations on moment redistribution in reinforced concrete frames subjected to vertical loads

In this study, experimental and numerical investigations of the moment redistribution behaviour in reinforced concrete (RC) frames subjected to vertical monotonic loads are presented. By testing 12 RC single-storey continuous frames over two equal spans of 3000 mm, the evolution of moment redistribution during the whole process of loading was observed, and two-stage moment redistribution that occurred at the serviceability limit state (SLS) and ultimate limit state (ULS) was proposed. The test results showed that with the increase in the yield strength of the reinforcement, the degree of moment redistribution at SLS was improved, which should not be neglected in the prediction of the permissible moment redistribution. Meanwhile, the strain penetration of the high-strength reinforcement was more obvious. This is beneficial to the moment redistribution in frame beams. To further investigate the influence of various parameters on the two-stage moment redistribution quantitatively, a nonlinear finite element (FE) model based on the damage plasticity constitutive law was developed and verified using the teste results. A parametric study was conducted based on 96 simulated specimens and the influential factors included the neutral axis depth factor, yielding strength of reinforcement, concrete strength, geometric dimensions of the frame columns and beams, M-V interaction, and loading patterns. The results indicated that M-V interaction had a detrimental effect on the plastic moment capacity, thus promoting the process of moment redistribution in RC structures. Based on the experimental and FE results, new practical calculation formulas that comprehensively reflected the influential factors were proposed to estimate degree of two-stage moment redistribution in RC frames.

Mathematical law of size effect on the flexural property of ceramics

Brittle materials generally exhibit size effects, and the mechanical properties of these materials degrade significantly with an increase in size. However, the mathematical law governing the attenuation degree of mechanical properties with the increase in size is still unknown. In this study, maximum loads of differently sized ceramic test strips were subjected to three point bending tests under two working conditions of equal spans and span amplifications, respectively. Subsequently, the theoretical maximum loads of materials were calculated using the finite element method (FEM). By calculating the difference between the calculated values and the actual maximum loads, the attenuation of mechanical properties of ceramic samples were observed. The results show that the theoretical mechanical properties and the performance attenuation caused by the size effect tend to increase according to the following equation: y=ax 3 +bx 2 +cx+d. Therefore, mechanical properties and performance attenuation of any sample exhibiting a size within the experimental range can be predicted by a mathematical law, which was obtained through mechanical tests results of four samples with different sizes. The obtained mathematical law holds great significance for predicting the mechanical properties of materials under size effects.

Finite Element Analysis of Overlapped Z-Purlins Restrained by Sheeting

Cold-formed steel Z-purlins with overlapping at the intermediate supports ensures the continuity of the bending moment. A continuous beam with two equal spans of 6 m is investigated under gravity loading using the finite element method. The numerical model includes the beneficial interaction between the Z-purlins and the trapezoidal sheeting. Finite element results show that the screw spacing and sheeting thickness has a limited influence on the resistance of the member. The effect of the overlapping length and detailing of the connection is studied through a parametric study. Six overlaps varying from 100mm to 1200mm (1.6% to 20% of one span) capture the change of the failure mode from the overlap edge to the support region of the purlin. The connection detailing is studied considering multiple bolt/screw patterns. The detailing and length of the overlap connection has a major influence on the moment distribution and consequently on the failure mode. The detailed finite element analysis shows that assuming the beam connection as continuous in 1D beam models lead to an unrealistic bending moment distribution and failure mode. Connecting the bottom flange using screws improves the overall load carrying capacity of the beam especially for short overlap lengths. The increase in resistance is attributed to the restraining effect on the free flange which fails due to distortional buckling.

Fire behaviour of deep beams under unsymmetrical loading

This paper focuses on the condition where a reinforced concrete (RC) deep beam is subjected to two concentrated loads (P1 and P2), which are positioned at respective distances a and c from bottom supports. In general, equal shear spans (a = c) and equal point loads (P1 = P2) are commonly assumed in most experimental programmes. Nevertheless, such cases are rare in practice. In contrast, due to the fact that deep beam floor normally subjects to irregular layout of column grid, deep beams are usually subjected to unequal load magnitude (load inequality or P1 ≠ P2) and unsymmetrical load positions (load asymmetry or a ≠ c). Although previous research has demonstrated the significant influences of load asymmetry and inequality on the structural performance of deep beams at room temperature, no research programme has been performed to study their influences on the fire performance of deep beams. As a result, this study is proposed to investigate the shear behaviour of unsymmetrically-loaded deep beams at fire condition, analytically and experimentally. The current research first derives a strut-and-tie-model (STM) to predict the shear capacity of RC deep beams under unequal/unsymmetrical loading conditions and at elevated temperatures. The STM takes into account the effects of unsymmetrical loading configurations, contribution of steel reinforcement on strut capacity, and thermal-induced gradient. Additionally, a test programme on six RC deep beams under fire condition is conducted for verification of the proposed model. Observations from this experimental programme show that load asymmetry and inequality have different effects on the fire performance of deep beams. To be more specific, an increase in load inequality leads to an alteration in failure mode of the deep beams, whist load asymmetry does not affect the failure mode as much. On the other hand, increasing load inequality can result in a significantly increased mid-span deflection at failure and a slightly increased failure time. Besides, effect of load inequality on deflection and failure duration depends on the loading positions. Furthermore, the proposed STM yields good agreement between test data and model predictions for unequally- and/or unsymmetrically-loaded deep beams, at both room and high temperatures.

Nonlinear Dynamic Analysis of Multi-vehicle Vehicle-bridge Coupling System

By analyzing different nonlinear models of vehicle-bridge coupling vibration when multiple vehicles travel on a bridge, this paper proposes the nonlinear vibration equation of multiple vehicle vehicle-bridge coupling. A comprehensive analysis is conducted on the quarter vehicle model, the nonlinear motion model of the bridge, and the coupled coupling equation of the vehicle and bridge. The vehicle-bridge coupled nonlinear analysis model of a single vehicle is established, and the correctness of the results calculated by the model is verified by calculation examples. In addition, taking the three-span continuous beam bridge with equal cross section and equal span as an example, this paper studies the driving conditions of multiple vehicles respectively from the influence of vehicle number, vehicle spacing and vehicle speed on the dynamic response value of the bridge. The results show that vehicle speed, vehicle number and vehicle spacing have significant influence on the dynamic response value of the bridge.