Negative Moment Research Articles

Experimental Investigation on Flexural Behavior of U-Shaped Steel–Concrete Composite Beams with Bolt Connections under a Negative Bending Moment

Because U-shaped steel beams filled with concrete have the advantages of reduced construction period and superior structural performance, they have been widely used as structural elements. In this study, the flexural behavior of newly developed bolt-connected U-shaped steel and concrete composite beams under a negative bending moment was experimentally evaluated. The main test variables were bolt spacing in bottom steel plates and types of U-shaped steel sections. Test results showed that the flexural behavior of the composite beams is determined by the plate-buckling mode of bolt-connected bottom steel plates. Composite beams with a greater bolt spacing than that in the standard AISI S100-16 experienced early plate buckling of the bottom steel plates, resulting in reduction of flexural stiffness and maximum flexural strength. Thus, the buckling mode of bolt-connected bottom plates should be considered for bolt-connected U-shaped composite beams under a negative bending moment. The longitudinal lips of U-shaped steel sections can increase the flexural performance of composite beams due to anchorage performance of the steel sections with lips.

Engineering push–pull structural versatility in highly functional carbazole-based hole transporting materials design for efficient perovskites solar devices

This study proposes a push–pull molecular engineering strategy to design highly functional hole transport materials (HTMs) for perovskite solar cells (PSCs). The strategy involves introducing acceptor-anchor groups via benzene spacer to the versatile carbazole core containing dimethoxytriphenylamine side groups, resulting in a series of nine newly designed HTM moieties (BEN-A1 to BEN-A9). Quantum simulation protocols using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods were employed to investigate the designed HTMs. Our results demonstrate that the designed HTMs exhibit promising charge separation and transport throughout the molecule with lower spatial hole-electron overlap at the carbazole core, resulting in 98% intrinsic charge transfer and small exciton binding energy (0.003–0.108 eV). The HTMs also exhibit stabilized HOMO energy levels (by up to 0.13 eV) approaching the threshold (−5.38 eV) with appropriate HTM/Perovskite energy levels alignment, suggesting excellent charge extraction and higher VOC. Optical analysis shows that our proposed HTMs exhibit large stokes shift values (82–108 nm) and transparent absorption in broader visible region, enabling full utilization of light for perovskite layer for photocurrent generation, efficient energy conversion, reduced thermalization losses, and improved spectral selectivity. The HTMs exhibit smaller hole reorganization energy (0.111–0.137 eV) and higher transfer integral, indicating robust hole mobility owing to enhanced carbazole core functionality. Furthermore, higher negative solvation-free energy values (−16.19 to −20.89 kcal/mol) and elevated dipole moments imply better solubility and surface-wetting properties. Overall, this study broadens our understanding of push–pull molecular engineering for versatile carbazole-based HTMs, which have immense prospects for efficient and functional application in PSCs.

“That's the negative moment of the dialectic …”

“That's the negative moment of the dialectic …”

Negative Moments of L–Functions With Small Shifts Over Function Fields

Abstract We consider negative moments of quadratic Dirichlet $L$–functions over function fields. Summing over monic square-free polynomials of degree $2g+1$ in $\mathbb{F}_{q}[x]$, we obtain an asymptotic formula for the $k^{\textrm{th}}$ shifted negative moment of $L(1/2+\beta ,\chi _{D})$, in certain ranges of $\beta $ (e.g., when roughly $\beta \gg \log g/g $ and $k<1$). We also obtain non-trivial upper bounds for the $k^{\textrm{th}}$ shifted negative moment when $\log (1/\beta ) \ll \log g$. Previously, almost sharp upper bounds were obtained in [ 3] in the range $\beta \gg g^{-\frac{1}{2k}+\epsilon }$.

Research on the influence of foundation pit excavation on the lateral force and deformation of side shield tunnels based on full-scale experiments

To explore the internal force and deformation response law of the Hangzhou subway shield segment under the influence of the excavation and unloading of the side foundation pit, the self-developed “shield segment hydraulic loading system” was used to carry out full-scale loading tests on the three-ring staggered assembled segments. A preloading loading test were performed before the formal experiment to determine the loading method of the initial confining pressure. Analyzed the change mechanism of the internal force and deformation of the segment structure are influenced by factors such as the foundation pit and the tunnel clear distance. A numerical model is established based on the experimental results, and the influencing parameters that are difficult to complete in the experiment, such as the depth of the tunnel, are analyzed in detail. The research results show that the equal load maintains a balanced state of the segment to the greatest extent, and its internal force and deformation results are large, which is suitable for this experiment. After the excavation of the foundation pit, the maximum positive and negative bending moment increases, while the maximum axial force decreases. The average maximum recovery rate of tunnel section is 15.6%. Moreover, the additional internal force and deformation of the segment will increase with increasing deformation parameters of the envelope structure and decrease with increasing clear distance between the foundation pit and the tunnel. The bending moment of the segment is more sensitive to changes in the confining pressure, the convergence change can be controlled within a limited range, and the trend of the change in the internal force of the bolt shows differences. The numerical model established in this paper can better analyze the stress state of the tunnel. When the tunnel is buried deep in the slightly upper position of the excavation surface of the foundation pit, the unloading effect that is received is largest.

Investigating UHPC in deck bulb-tee girder connections, part 2: Full-scale experimental testing

Deck bulb-tee girders constitute an excellent precast concrete bridge element system for medium- to longspan bridges. The precast concrete girders are transported to the jobsite, where they are placed adjacent to each other. The girders are connected using field-cast longitudinal joints. When required, a continuity diaphragm over the pier is used to create moment continuity; however, there is a risk of cracking of the field-cast joints and construction can be difficult when adjacent girders have different camber profiles. Given these challenges, adoption of the deck bulb-tee girder systems has been limited. Analytical investigation performed in part 1 of this series of papers indicated that using ultra-high-performance concrete (UHPC) can improve the performance of the field-cast joints and help overcome construction difficulties. This paper describes full-scale experimental testing performed as a follow-up to the analytical investigation. Longitudinal joints grouted with UHPC were tested under a combination of thermal and live load. A continuity diaphragm with partial UHPC was also tested under positive and negative moments over the pier.

Experimental and Analytical Studies of Continuous Steel-Stringer Lateral-Torsional Buckling Resistance

In the 1950s and 1960s, some Louisiana’s bridges were constructed using steel twin-girder or truss systems, in which floorbeams are carried by the main members and continuous (spliced) stringers are supported by the floorbeams. The main members are either two-edge (fascia) girders or trusses. One of the byproducts of this type of design is that stringer bottom flanges are in compression in the negative moment region over the floorbeams, which could result in lateral torsional buckling (LTB) should inadequate lateral bracing be provided. When the continuous stringers are load-rated using AASHTOWare Bridge Rating analysis software (BrR 7.1), their LTB resistance is calculated in accordance with American Association of State Highway Officials (AASHTO) LRFD Bridge Design Specifications, which do not account for potential bracing provided by a noncomposite deck and could underestimate flexural strength. As a result, the rating may be low enough to require restrictive load posting or even bridge closure. This paper summarizes extensive experimental and numerical studies investigating the behavior of this type of floor system by testing two-span, continuous, steel stringers in a grillage that included three stringer lines, an interior transverse support (floorbeam), and transverse diaphragms at the end supports. The tests and finite-element analysis studies encompassed a variety of unbraced lengths and support conditions with steel diaphragms or timber ties acting as bracing members. The findings demonstrated that, for the systems examined, minimal bracing could substantially enhance LTB resistance and supported the use of higher flexural strengths than those currently predicted using AASHTO Specifications. This paper illustrates the use, challenges, and successes in LTB modeling beams with various support and bracing conditions. The most flexible cases were the most difficult to achieve close agreement with experimental results.

Investigations on influences of Engineered Cementitious Composites (ECC) on pull-out properties of studs in steel-concrete composite bridge

Stud plays an important role in the connection of steel-concrete composite bridge (SCCB). The stud is under pull-out load in the negative moment zone of SCCB. Engineered Cementitious Composites (ECC) are a new type of materials with tensile strain hardening and multiple cracking behavior to strengthen SCCBs. In this study, the cyclic pull-out effect on the ECC-stud connection was studied through pull-out tests. The stud diameter (d=13/16 mm) and the embedment depth (hef=40/60/80 mm) are included as design parameters, resulting in a total of 18 specimens of six scenarios. The failure mode, load-bearing capacity, and ductility factor of the specimens under cyclic loading are compared with those under monotonic loading, and the stiffness, energy dissipation capacity, and residual displacement of the specimens under cyclic loading are analyzed. Based on the experimental results, under cyclic loading, the concrete cone failure and splitting failure occur, and the threshold of hef/d between the two failure modes is 3.75–4.62, which is smaller than the threshold of the monotonic scenarios. Both concrete and splitting failure modes show ductile failure characteristics because of the bridging effect of fibers in ECC. The load-bearing capacity and ductility factor under cyclic loading are lower than those under monotonic load. This is because, under cyclic loading, the specimens show cumulative damage, which, however, is weakened due to the strengthening effect of ECC. As d and hef increase, the load-bearing capacity, ductility factor, stiffness, and energy dissipation capacity increase correspondingly, and the residual displacement decreases. The stud with a larger d shows a more obvious ductility holding stage.

Moment redistribution in Hybrid-RC continuous beams with T-section using FEM

The use of Fiber Reinforced Polymers (FRP) alone or together with steel as a reinforcement material in reinforced concrete, especially in structures exposed to bad weather conditions, has recently received much attention. This research was conducted with the aim of investigating the effect of different parameters on the amount of moment redistribution in continuous T-shaped concrete beams reinforced with combinations of steel reinforcement and Glass-FRP (GFRP). For this purpose, ABAQUS finite element software was used. The research variables were the ratio of GFRP reinforcement to steel in the positive and negative moment areas, the type of materials in these areas, and the effect of stirrups on the moment redistribution. After verification of modeling, new models were built, and variables were investigated. The results show that it is better for the ratio of Af/As in the upper and lower parts of the beam to be more than one and less than 0.75, respectively. Therefore, theoretically, the best case of moment redistribution is when the negative and positive reinforcement is GFRP and steel, respectively. Similar to the Steel-RC codes, an equation based on the maximum strain in the farthest tensile bar is introduced to calculate and limit the maximum moment redistribution in these beams.

Свердловская железная дорога в 1941-1945 годы: вклад в эвакуацию

The paper analyses the work of the Sverdlovsk railway divided during the Great Patriotic War into two main lines - the Perm and the Sverdlovsk lines (before 1943 - named after L.M. Kaganovich) to ensure the evacuation of industrial enterprises and population from western territories of the USSR to the eastern regions. The paper also shows the process of conversion of the railway economy to correspond to war requirements and needs and describes measures aimed at overcoming difficulties, such as staff reduction, a poor repair base, lack of locomotives and fuel for them, inconsistency of dispatching services. Particular emphasis is placed on the occurrence of “traffic jams” associated with an increase in the intensity of rail traffic and loading-to-unloading problems that directly affected the effectiveness of the rolling stock.
 The paper reveals weaknesses in organization and implementation of transporting civilians to the rear areas. The author found that systematic train schedule delays, inconsistency in the actions of evacuation and railway services generated a lot of everyday problems, e.g. low comfort, poor nutrition, spread of infectious and cold-related diseases and, as a consequence, a high percentage of mortality among evacuated passengers.
 Throughout the whole war period, the Soviet authorities intentionally corrected negative moments in the functioning of railway lines. As a result of the adoption of a number of government resolutions followed by the corresponding efficient actions, the “great migration to the East” of industry and a significant part of population from areas subjected to the Nazi invasion was successful. The Sverdlovsk railway fulfilled its tasks with honour making a significant contribution to the evacuation and creation of a powerful military-industrial complex in the Urals.

Three-Dimensional Numerical Simulation for Lateral Distortional Buckling Behaviour of Steel-Concrete Composite Beams

Lateral Distortional Buckling (LDB) is a mode of instability in Steel-Concrete Composite (SCC) beams that is yet to be fully understood by the structural engineering research and design community. This work investigated numerical methods to understand the LDB behavior of SCC beams under negative moments that exhibit nonlinear behavior. Focus of the study was to develop and validate 3-Dimensional finite element (FE) models which capture the LDB behavior of SCC beams precisely. Detailed 3-Dimensional FE models of the SCC beams were developed using ABAQUS. For modeling concrete, a nonlinear damage plasticity model was considered. A quad-linear curve was used to describe the stress-stain relationship for the steel beam. The stress-stain relationship for the rebar was described using a bi-linear curve while an elastic perfectly plastic model was assigned to the headed stud shear connectors. Steel hardening behavior was simulated using an isotropic hardening model. The interaction between the concrete slab, steel beam, and studs was described using appropriate interface elements combined under suitable constraints. The FE model’s accuracy was validated by results obtained from previous experiments found in literature together with a brief description of the experiments done by previous researchers to ensure completeness. Validation of the model was done by comparing Moment-Rotation curves obtained from the experimental tests, lateral displacements of the bottom flange along the axial direction and comparison of the failure modes between the numerical model and experimental test specimens. It was observed that the maximum relative error for the ultimate moment capacity of the composite beams from FE analysis and the experimental tests was less than 2% which shows that the FE model was in strong agreement with the experimental results. Accordingly, the numerical model developed herein proves to be capable of accurately representing the LDB phenomenon.

Numerical Model for Rectangular Pedestrian Underpass Excavations with Pipe-Roof Preconstruction Method: A Case Study

Under weak geological conditions, soil deformation and surface settlement are the key factors affecting the success of shallow-buried rectangular excavation. To investigate this issue, an underpass of Zhongxiao East Road in Taipei City was used as a case study. The surface settlement and lateral deformation of an underground diaphragm wall caused by the excavation of a rectangular pedestrian underpass using the pipe-roof preconstruction method (PPM) were investigated by 3D finite element analysis. The numerical analysis results showed that the constructed numerical analysis model had considerable accuracy. The use of PPM combined with a box culvert structure to form a pedestrian underpass could effectively control the surface displacement above the box culvert. Under the condition of the same sectional area, the smaller the width of the pipe-roof structure, the more the impact on the ground surface was reduced. The maximum positive bending moment and maximum negative bending moment on the pipe roof produced by excavation at each stage were roughly inversely related to the height per the width of the cross-section of the pipe diaphragm structure. The results showed that the pipe-roof structure was suitable for underground excavation with shallow-buried depth in the soft soil of the Taipei Basin. Moreover, the shallow-buried box culvert was more sensitive to the subsidence caused by construction than the deep-buried box culvert.

Experimental research on the structural performance of continuous composite beams with uplift-restricted and slip-permitted connectors

The uplift-restricted and slip-permitted (URSP) connector technology is a new composite technology which achieves the purpose of reducing the tensile stress in concrete slab by releasing part of the composite action in the negative moment region. In this paper, it is found that arranging URSP connectors in continuous composite beams has an end-restraint effect, which has a significant impact on the force transfer mechanism of URSP composite beams. Previous studies on URSP technology seldom mention similar constraint effects, which cannot accurately reveal the mechanical behavior of URSP composite beams. In order to properly consider the influence brought by the end-restraint effect, this study uses continuous composite beams to carry out experimental research. Three two-span continuous composite specimens are fabricated and tested in this research. Six aspects of performance are compared and analyzed in detail, including ① cracking load, ② crack distribution and development pattern, ③ interfacial slip behavior, ④ deformation and stiffness, ⑤ internal force redistribution, and ⑥ strain distribution. It is found that the URSP connector can realize the release of part of the composite action, and has a significant effect on the crack control in the negative moment region. Meanwhile, the application of URSP connectors has little effect on the stiffness, bearing capacity and strain of steel beam.

The log‐moment formula for implied volatility

AbstractWe revisit the foundational Moment Formula proved by Roger Lee fifteen years ago. We show that in the absence of arbitrage, if the underlying stock price at time T admits finite log‐moments for some positive q, the arbitrage‐free growth in the left wing of the implied volatility smile for T is less constrained than Lee's bound. The result is rationalized by a market trading discretely monitored variance swaps wherein the payoff is a function of squared log‐returns, and requires no assumption for the underlying price to admit any negative moment. In this respect, the result can be derived from a model‐independent setup. As a byproduct, we relax the moment assumptions on the stock price to provide a new proof of the notorious Gatheral–Fukasawa formula expressing variance swaps in terms of the implied volatility.

Near Ambient Superconductivity by 15N as Needles in the Haystack: Lower Temperatures and Pressures for Possible 15N Enrichment in LuH2

The author has previously noted the effects of stable isotopes having different nuclear magnetic moments on chemistry, catalysis, biochemistry, thermodynamics, optics, superconductivity and more [1]. In this controversy surrounding reported room temperature superconductivity at near ambient pressures by nitrogen doped lutetium hydride, the author hopes to convince and reason that the different synthesis conditions of the original work of Dias and coworkers [2] at low temperature, mild pressures, diamond anvil cell compression and prolong annealing may lead to selective doping of the lutetium hydride by 15N. The later attempted replication of Dias and coworkers by Hai-hu Wen and coworkers [3] may have caused different outcomes as Hai-hu Wen and coworkers appeared to try Dias work and then switched to a different synthetic method whereby Wen and coworkers instead applied high pressures and high temperatures to the reacting hydrogen, nitrogen and lutetium to produce a nitrogen doped lutetium hydride with similar lattice structure as the originally reported by Dias and coworkers [2] but lacking observed superconductivity and evidence of superconductivity by diamagnetism. The author here by his theory notes the possibility that the different later high pressure, high temperature synthesis by Wen and coworkers doped their sample with 14N rather than 15N as originally enriched in Dias’s sample. Thereby the author notes by his theory [1] that whereas 15N doped lutetium hydride manifests higher superconductivity due to its negative nuclear magnetic moment (NMM), the 14N doped lutetium hydride should not manifest superconductivity at the higher temperatures due to its positive NMM.

Calculation Method for Flexural Bearing Capacity of Composite Girders with CFST Truss Chords

To study the flexural behavior of composite girders with concrete-filled steel tubular (CFST) truss chords under positive and negative bending moments, model tests, and theoretical analysis were carried out to investigate the evolution of their flexural behavior and the flexural bearing capacity. The results showed that the web members and joints of composite girders with CFST truss chords subjected to positive and negative bending moments had high strength and rigidity, which ensured that joint failures did not occur before the failure of the entire cross section. The longitudinal strains along the member axis changed linearly along the cross-sectional height, which confirmed the correctness of the plane-section assumption. The failure mode was due to the yield of the steel tube used in the chord and the rebars in the concrete slab under positive and negative bending moments, respectively. The contributions of the web members to the flexural bearing capacity under positive and negative bending moments were 12.5% and 8.6%, respectively. Calculation methods considering the contributions of the web members to the flexural bearing capacity under positive and negative bending moments were proposed. The deviation between the results of the proposed calculation methods and the test and the results of the finite-element parametric studies was less than 8.1%.

Lattice Study of the Equation of State of a Rotating Gluon Plasma

The effect of uniform rotation on the equation of state of gluodynamics has been studied in lattice simulation. To this end, the system has been considered in the corotating reference frame, where the rotation can be modeled as an external gravitational field. The free energy of the studied system in the case of sufficiently slow rotation can be expanded in a power series in the angular velocity. The moment of inertia given by the second-order coefficient of this expansion has been calculated and its dependence on the temperature and the dimensions of the rotating system has been determined. Our results indicate that the moment of inertia of gluodynamics is negative up to the temperature T * ~ 1.5Tc, where Tc is the critical temperature of the confinement/deconfinement phase transition, and becomes positive at temperatures T > T *. The negative moment of inertia has been attributed to the thermodynamic instability of the gluon plasma with respect to uniform rotation.

EVALUASI KAPASITAS STRUKTUR EKSISTING LANTAI JEMBATAN PADA JEMBATAN TYPE PILE SLAB DI RUAS JALAN TOL JORR W1 KEBON JERUK

This research a study transverse cracking that occurred on the floor structure of the pile slab type bridge located at JORR W1 Kebon Jeruk toll road. The purpose of this study was to evaluate the capacity of the bridge floor structure that had damaged by cracks and weather its remains are in a safe condition or not. The research method is carried out by analyzing the calculation of loading that occurred in an actual condition that had cracked by modeling on structural analysis program with standard SNI 1725:2016 and actual loads that acted on the structure, then evaluating the moment capacity of the structure based on installed reinforcement and evaluating deflection from inspection results based permissible deflection. From the results of the analysis, it was found that the structure experienced a moment failure due to the actual load with a load magnitude of 18,07 tons, the moment due to the actual load on the negative moment region was 34,47 tons.m and the positive moment region was 37,46 tons.m, compared to the moment capacity of structure successively which was 25,52 tons.m and 29,16 tons.m. However, for the results of the analysis of the standard load of 11,25 tons, the moment capacity of the structure was able to withstand the ultimate moment due to the reactor load successively being 22,82 tons.m and 24,37 tons.m, whereas for the deflection test results of 0,46 mm remained in a safe condition without exceeding the L/800 permit deflection of 4,76 mm. Based on the results of the analysis, it can be concluded that the structure is overloaded and in the future, the structural ability must be improved and it is necessary to strengthen the bridge floor structure to be able to increase the capacity of the structure so that it can withstand the working load.

An Extension of the Poisson Distribution: Features and Application for Medical Data Modeling

This paper introduces and studies a new discrete distribution with one parameter that expands the Poisson model, discrete weighted Poisson Lerch transcendental (DWPLT) distribution. Its mathematical and statistical structure showed that some of the basic characteristics and features of the DWPLT model include probability mass function, the hazard rate function for single and double components, moments with auxiliary statistical measures (expectation, variance, index of dispersion, skewness, kurtosis, negative moments), conditional expectation, Lorenz function, and order statistics, which were derived as closed forms. DWPLT distribution can be used as a flexible statistical approach to analyze and discuss real asymmetric leptokurtic data. Moreover, it could be applied to a hyperdispersive data model. Two different estimation methods were derived, i.e., maximal likelihood and the moments technique for the DWPLT parameter, and some advanced numerical methods were utilized for the estimation process. A simulation was performed to examine and analyze the performance of the DWPLT estimator on the basis of the criteria of the bias and mean squared errors. The flexibility and fit ability of the proposed distribution is demonstrated via the clinical application of a real dataset. The DWPLT model was more flexible and worked well for modeling real age data when compared to other competitive age distributions in the statistical literature.

MECHANISMS OF INVESTIGATION OFTHE EXTERNAL AND INTERNAL ENVIRONMENT OF THE COMPANY WHEN CHOOSING A SUPPLIER

The article considers the need to analyze the most important factors of the external and internal environment. The article is devoted to the external and internal environment of the company when choosing a supplier. The main factors influencing the activity of enterprises are singled out. It is determined that the study of the external and internal environment of the company is a tool to identify possible threats to the organization. The study of the external and internal environment allows the company to predict possible situations in a timely manner, develop an action plan in case of negative moments, formulate a strategy that will allow the company to achieve its goals and prevent possible losses. The main definitions are considered and methods are proposed that can be used in the system of strategic analysis. The article focuses on the issues of enterprise research through SWOT and PEST analyzes, which are used to make a strategic decision, and also helps to determine the advantages and disadvantages, which will assess the need for these methods and highlight the points that require improvement of the company when choosing a supplier. It is concluded that there is a need for increased attention to the analysis of the external and internal environment, as well as the importance of internal analysis of all the main components of research mechanisms.