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In order to study the occurrence mechanism of rock burst in L-shaped zone during a fully mechanized mining period, the No. 705 working face which is located in Baojishan Colliery is taken as a typical engineering background. By means of in situ investigation, theoretical analysis, numerical simulation, in situ tests, and relevant monitoring methods, the occurrence mechanism of rock burst and corresponding prevention technology are studied. The results show that a coal pillar with some confining pressure in the L-shaped zone is established by FLAC3D numerical simulation software, and the numerical simulation results indicate that the change in static load has a greater effect than dynamic load on coal pillar unstable failure; the static load plays a role in storing energy, and dynamic load plays a role in inducing rock burst; the bolt-mesh-cable support and high-pressure water jet unloading combined technology is put forward to prevent rock burst in roadways, and the numerical simulation results show that stress distribution of surrounding rock meets the model of strong-soft-strong (3S) structure, and the moment distribution is reasonable. In the follow-up mining, a limit value of coal fines is used to determine that this measure is a reasonable method to prevent rock burst. The study conclusions provide theoretical foundation and new guidance for preventing rock burst by synergistic effect technology in roadways.

In this study MVLEM (Multiple Vertical Line Element Model) is utilized to model a shear wall made of concrete with asymmetric openings. For this aim, an experimental RC shear wall with asymmetric openings was studied and modeled by the 3D microscopic FEM (Finite Element Method) via ABAQUS software package. To achieve a macroscopic model with a high accuracy two macroscopic shear walls were modeled. These macroscopic walls are identical whereas the main difference is the stiffness in the beam at the connection zone. The macroscopic modeling for different members of the studied concrete shear wall column next to the openings coupling beams and the wall is developed by horizontal and vertical springs that simulate shear and flexural behaviors. Modeling of these parts depends on the moment distribution from horizontal loading. Responses of the macroscopic models under static cyclic and monotonic loading were compared with the validated microscopic model. According to the results the proposed macroscopic model in which low connection stiffness was used shows acceptable accuracy with the microscopic model.

Wind turbine mainly relies on blades to capture wind energy and complete energy conversion. Wind turbine blade is one of the key components of wind turbine. In the full scale load test of wind turbine blade, the moment matching is the key part of the test and the premise of wind turbine blade certification. In order to solve the matching problem of the bending moment and the arrangement of counterweight in the fatigue loading test, an improved intelligent optimization algorithm was proposed to achieve the purpose of moment matching. The relationship between the excitation frequency of the rotating mass and the natural frequency of the blade was determined through the identification of the modal test parameters, and the calculation model of the section bending moment was constructed. Based on the optimization algorithm, the joint optimization of moment distribution and amplitude control was carried out with the mean square error as the fitness function. The correctness and feasibility of the balance weight optimization scheme for moment matching in uniaxial fatigue test were verified through the blade test.

Dara and Ahmad (Recent advances in moment distribution and their hazard rates, Academic Publishing GmbH KG, Lap Lambert, 2012) proposed the length-biased exponential (LBE) distribution and proved that the LBE distribution is more flexible than the exponential distribution. In this paper, we have obtained new explicit algebraic expressions and some recurrence relations for both single and product moments of order statistics from LBE distribution. Further, these expressions are used to compute the means, variances and covariances of order statistics for different sample of sizes and for arbitrarily chosen parameter values. Next, we use these moments to obtain the best linear unbiased estimates of the location and scale parameters based on complete as well as Type-II right censored samples. Finally, we carried out a simulation study to show the application of our results.

Mining pit in a channel bed causes disturbance to the flow characteristics. To interpret the phenomenon of change in flow characteristics in a mining pit, experimental study was performed in a tilting laboratory flume. This research focuses on the impact of mining pit on different turbulent parameters, such as flow velocity, Reynolds shear stress distribution, turbulent kinetic energy fluxes, and higher order moment distribution. We have observed dropped in flow velocity in the pit and also significant reversal velocity layer at the pit bottom. The analysis of Reynolds shear stress and higher order moment distribution shows higher values of velocity fluctuations in the pit than the upstream section. The response of bursting events, which is identified by the third order moment, shows influence of sweep events near the bed in all four sections. Third order moment analysis also shows a rise in dominance of sweep events along the flow depth in the pit and it’s downstream, compared to the upstream section. The kurtosis distribution shows highly intermittent nature of turbulence close to the channel bed. The longitudinal turbulent kinetic energy fluxes and vertical turbulent kinetic energy fluxes are in downstream and downward directions for both inner and outer layer in the pit region, which shows an increase in bed particle mobility in that region, whereas it is present only in the inner layer at the upstream section. Additionally, improved bed load transport equation by incorporating pit geometry has been proposed for alluvial channel subjected to sand mining.

The inelastic behaviour of a steel beam is complicated by reductions in the section rigidities which depend on the moment distribution and residual stress pattern. The inelastic beam is effectively tapered and mono-symmetric, and iterative numerical methods need generally to be used for the analysis. The in-plane moment distribution in an inelastic continuous beam lies between the commonly assumed rigid-plastic “plastic” path and a “yield” moment path. The yield path is the more critical for lateral buckling of the continuous beams considered in this paper. Approximations of the inelastic out-of-plane moduli of continuous beams developed from closed form lateral buckling solutions for simply supported beams in uniform bending can be used in a computer program for the buckling analysis of tapered mono-symmetric beams. Residual stresses cause significant reductions in the inelastic buckling resistance. The AISC design code predicts strengths which are similar in shape but significantly higher in magnitude than the inelastic buckling resistances of simply supported beams in uniform bending. The predictions for beams with central concentrated loads are much higher than the corresponding inelastic buckling resistances. Closer but still conservative approximations are obtained by using the method of design by inelastic buckling, which can also be used for continuous beams. This method is much simpler than those used to obtain accurate predictions.

The evaluation and design of concrete bridges in large part depend on the transverse distribution characteristics of the live load carried and the service level. The live load distribution for continuous concrete multicell box-girder bridges varies according to bridge configuration, so when designing such bridges, it is important to determine the maximum negative stress at the piers, the midspan positive (tensile) stress and the deflection of the bridge when subjected to live loads. This paper reports an extensive parametric study to determine the maximum stress, deflection, and moment distribution factors for two span multicell box-girder bridges based on a finite element analysis of 120 representative numerical model bridges. Bridge parameters were selected to extend the parameters and ranges of current live load distribution factors defined by AASHTO LRFD specifications. The results indicate that the span length, number of boxes, and the number of lanes all significantly affect the positive (tensile) and the negative (compression) stress distribution factors. A set of equations proposed to describe the behavior of such bridges under AASHTO LRFD live loads yielded results that agreed closely with the numerically derived results for the stress and deflection distribution factors.

The China Fusion Engineering Test Reactor (CFETR) is a superconducting magnet tokamak, and one mission is to demonstrate a full cycle of self-sustaining tritium. In this study, in order to validate the electromagnetic (EM) load distribution on the helium-cooled ceramic breeder (HCCB) blanket, a three-dimensional model of the CFETR sector was developed in the finite element software ANSYS. The system was analyzed considering a plasma major disruption scenario with an exponent current quench of 36 ms. The EM forces and the moment distribution on the blanket module as well as on the segment were calculated. Then, the EM loads were used as the input for the structural analysis of the HCCB blanket. Moreover, the results were compared to those of linear analyses to underline the effect of the non-linearity of the ferromagnetic materials on the EM load distribution of the HCCB blanket. These results indicated that the maximum equivalent stress and displacement satisfied the requirements of structural safety design. With respect to the design and optimization of CFETR, this investigation will provide technical reference and data support for the future design and optimization of the HCCB blanket.

The vertical movement of a trimaran caused by external disturbances during sailing, may lead to seasickness of the passengers and damage of the equipment onboard. Based on computational fluid dynamics (CFD) calculations, the hydrodynamic coefficients are obtained and a mathematical model of the trimaran is established, and with experiments of trimaran sailing in water tanks, the hydrodynamic coefficients solved by CFD are verified. Then, the T-foil and flap are designed, and the lift force and moment are solved by CFD. Next, the slope of the force of different attack angles on the T-foil and flap is obtained by the polynomial fitting. Finally, the trimaran vertical stabilization proportion and derivative (PD) controller, based on the sigmoid function, is designed with a new method of the resultant force and moment for a dynamic decoupling T-foil and flap. Through the simulation of trimaran movements systems with active T-foil and flap, the PD parameters are obtained. Then, the effect of the controller on trimaran vertical stabilization is verified by the experiments in the water tanks.

In general, a structure is to be designed resistant to the sudden and natural disasters. So, in order to compete in the ever-growing global market, a structural engineer should be precise in his work considering all the possible loads that show an impact in the behavior of a building when it is prone to sudden loading. So, this project is an attempt to analyze and design a G + 10 multi storied building by taking into consideration all types of loading such as dead load, live load, wind load and especially seismic loads. The analysis is performed using conventional methods like moment distribution method, flexibility matrix method and a computer aided software called STAAD Pro. The design of the multistoried structure is done using the Indian Standard Code IS 456. The load consideration is as follows; dead and live loads are taken as per the design regulations in IS 875 Part-I and II respectively, the wind loads are considered as per IS 875 Part-III and the seismic loads are taken as per IS 1893:2016. The analysis of the structure using STAAD Pro software involves modeling and defining the structure and as the result, parameters like shear force, bending moment and deflection are obtained. The results obtained in the analysis of the structure by using both software and manual calculations are compared, and the design is performed for the maximum obtained results.

This paper presents a comprehensive study of the support effect and characteristics of a collaborative reinforce system of U-steel support and anchored cable (USS-AC) for roadway under high dynamic stress in a coal mine in China. The deformational behavior of the roadway and the load characteristics of reinforcing elements were measured in real time and analyzed. A numerical simulation study has also been conducted to identify the interaction of the reinforcing elements to the surrounding rock under dynamic load. The research results suggest that the stress distribution of roadway surrounding rock could be changed and that residual strength of the surrounding rock near opening could be increased by using USS-AC. Based on the action of anchored cable, the moment distribution of U-steel support is optimized. The load capacity and nondeformability of the U-steel support are promoted. And the global stability of U-steel support is enhanced so as to achieve the goal of high supporting resistance. When the deformation stress of the surrounding rock is higher, the U-steel support deforms as the surrounding rock. The two side beams and the overlapping parts of U-steel support suffer the highest deformation stress. As a result, the anchored cable provides higher reaction force for the previous locations of the U-steel support in order to prevent deformation of support towards to excavation. As an integral structure, the U-steel support is confined to a limited deformation space under the action of anchored cable. The larger deformation is released through sliding motion of the overlapping parts so as to reach the ultimate of high supporting resistance of USS-AC.

Conventional slit dampers are widely used for the purpose of seismic retrofitting, however, the structure of these dampers is susceptible to fractures, due to stress concentration at the ends of the strips in the event of large earthquakes. To address this issue, a novel radius-cut coke-shaped strip damper featuring improved ductility is proposed herein. This damper was developed based on the moment distribution over the strip when both its ends were constrained. The height-to-width ratio of the strip was increased to induce bending rather than shear deformation, and the reduced beam section method was employed. A radius-cut section was used to intentionally focus the stress to induce the plastic hinge. This reduced the fracture fragility of the specimen, resulting in an increased inelastic deformation capacity. Cyclic loading tests were conducted to verify damping performance against earthquakes. Experiments and finite element analyses proved that the coke-shaped damper exhibits improved ductility. The final fracture occurred in the radius-cut section after sufficient energy dissipation during cyclic loading. The results also indicated further improvements in strength due to the membrane effect under cyclic loading, caused by the tensile resistance of the strip due to its constrained ends.

This thesis develops a new structural system suitable for low-cost transitional prefabricated housing. The system utilises rotational press-fit (RPF) integral joints, a lightweight hybrid fibre reinforced polymer (FRP) timber material, and a novel folded assembly method. Together, these techniques allow for extremely high system performance, including low cost and streamlined fabrication; high-speed and uncomplicated construction; and strong and predictable structural behaviour. The new system has been developed following systematic improvement to existing features of digitally-fabricated residential housing systems, specifically systems that employ press-fit connections for plywood building component assembly. The key findings of this thesis are in three areas, summarised as follows.First, experimental, numerical, and analytical methods are used to accurately characterise the structural behaviour of press-fit integral connections. Digitally-fabricated thin-walled square hollow sections (SHS), formed by attaching four plates with press-fit integral joints, are tested under uniaxial compressive loading and shown to fail through both conventional crushing and novel pop-off bifurcation failures. Pop-off buckling behaviours are shown to be governed by integral joint transverse stiffness and its magnitude relative to a critical edge stiffness value. Columns with joint transverse stiffness values less than a critical edge stiffness value exhibit pop-off failures and comparative investigations show thin-walled sections with integral joints can match the compressive capacities of glued sections, only when crushing governs.Second, a detailed geometric design-to-fabrication procedure is presented for the new folded timber sandwich structural system. The computational method segments and unfolds a target building profile, with generated segments formed as timber sandwich panels with integral press-fit and RPF joints. Two structures are built to validate the procedure and hypothesised rapid construction speed: a 30m2 house comprising six identical folded timber arches, built in one week; and a 42m2 canopy structure comprising 4 pairs of curved timber wings, built in two weeks. The as-built structures were 3D scanned and a defect analysis was conducted to assess the reliability and precision of assembled geometries. Both structures were highly accurate, with average absolute surface error generally less than the thickness of the timber material.Third, experimental and numerical methods are used to investigate the structural behaviour of the folded sandwich arch structures. Six arches are tested to failure to validate the suppression of press-fit pop-off instability and the structural performance of the assembly method. Experimental testing of the arches show failures occurring through both FRP tensile rupture and core compressive failures. A nonlinear static analysis and simplified 2D frame model is proposed to predict moment distribution and failure load for FRP rupture modes. This model characterises the RPF joint as a nonlinear semi-rigid hinge, with assigned bilinear moment-curvature relation obtained from analysis of joint strain data collected during arch testing. Core compressive failures are shown to occur as an inelastic core buckling behaviour when there is misalignment between assembled core segments.Overall, the new structural system demonstrates a fast, accurate, and consistent built form with strong and robust structural performance. It succeeds in creating a new design solution for low-cost prefabricated system and is likely to be adaptable for construction of many other curved and lightweight building types.

Kimura et al. [2, 3] has proposed the concept to realize beam yielding mechanism of a steel moment-resisting frame by applying a mid-story pin column base system. Controlling moment distribution, the system reliably prevents yielding of the first story columns. As design procedure to predict their elasto-plastic behavior, modified D-value method has been proposed. Previous papers [1] examined flexural strength of columns to keep them in elastic when frames were modeled as those having perfect elasto-plastic beams. In reality, however, bending moment keeps increasing due to strain hardening after beams yield. In this paper, the authors develop the modified D-value method to consider strain hardening effect. Using a proposed method, required flexural strength of columns is clarified to avoid them from yielding up to when the frame forms beam yielding mechanism. The results of the modified D-value method sufficiently agree with those of static analysis of low-to-mid-rise steel moment resisting frame. It is clarified that the story drift is reduced for larger strain hardening gradient, and that the maximum bending moment of the column does not change significantly, compared with those of perfect elasto-plastic frame.

Stretch bending is commonly used in the fabrication of profile-based shapes. However, one of the challenges in many bending-type forming processes is controlling springback upon unloading. Springback appears sensitive to upstream and in-process parameters, making prediction and control difficult. The springback problem is particularly important in forming processes where stringent control strategies are needed to assure product dimension, process flexibility and overall equipment effectiveness. In this research, we present an analytical framework for springback assessment in a stretching-controlled bending process. A new, flexible rotary stretch bending machine is designed and built, which allows the manufacture of complex-shape profiles with varying curvatures, including straight portions, with low tool investments. Furthermore, a Full Moment (FM) analytical model is developed for springback assessment. The modeling strategy employs a full moment distribution along the entire profile upon bending, introducing a stretching-controlled moment transition between different curvature portions such that the springback contribution from the plastic moment outside the theoretically bent portions is considered. Additionally, the influential factors related to material, geometry and process, including the applied stretching strains, are comprehensively considered. In this way, the modeling strategy enables accurate evaluation of springback in the flexible stretch bending process. Moreover, the proposed forming process is validated by a series of experiments conducted for a wide range of stretching levels using rectangular hollow aluminum alloy profiles. This forming strategy demonstrates high capability for controlling springback and dimensional accuracy. By comparing experiments, numerical simulations and analytical calculations, this proves that the developed FM model provides accurate and efficient assessment of springback. The average relative error provided by the FM model is 2.2%, as compared to 10.5% for a classical method used for comparison. Using the analytical model combined with numerical simulation, the crucial deformation characteristics, including stretching-dependent evolution of strain transition, are revealed. Overall, the FM analytical strategy has proven its capability as an effective tool, which can make springback knowledge more explicit, generic and reuseable for stretching-controlled bending processes. © 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

Understanding how individuals distribute mechanical demand imposed on their upper extremity during physically demanding activities provides meaningful insights to preserve function and mitigate detrimental mechanical loading of the shoulder. In this study, we hypothesized that parameterization of the shoulder net joint moment using four functional axes could characterize distribution tendencies about the shoulder during manual wheelchair propulsion and that regardless of demographics, a shoulder flexor dominant NJM distribution would be predominantly used by individuals with paraplegia (n = 130). Forces and kinematics of the upper extremity and trunk were quantified using motion capture and an instrumented wheel during steady state manual wheelchair propulsion at self-selected fast speeds on a stationary ergometer. The results indicate that parsing out the internal/external rotation component of the shoulder net joint moment about the upper arm and distributing the remainder across the three orthogonal axes of the torso was successful in identifying common shoulder net joint moment distribution techniques used across individuals with paraplegia during manual wheelchair propulsion. Distribution tendencies were predominantly flexor dominant across injury level, gender, time since injury, body mass index, and height demographics. The 4-axis parameterization of the shoulder NJM effectively differentiated moment distribution tendencies used by individuals during manual wheelchair propulsion using a functionally relevant representation of shoulder kinetics. Use of the four-axis parameterization of joint kinetics in future studies is expected to provide important insights that can advance knowledge, preserve function, and inform clinical decisions.

To realize a beam-to-column joint for precast concrete (PC) frames with simple details, adjustable performance, and desirable seismic performance , an innovative dry-connected rotational friction dissipative beam-to-column joint (DRFDBJ) is proposed in this study. To validate the advantages of introducing DRFDBJs into PC frame structures, PC frame with DRFDBJs (NPCF) is proposed and considered as the research object. This investigation highlighted on (1) validating the advantages of the DRFDBJ and NPCF, (2) revealing the critical design parameters of the NPCF, and (3) developing a high-efficiency design method for the NPCF. Based on parametric analyses of 300 NPCF study cases and three monolithic reinforced concrete frame study cases, the seismic performance of NPCF is investigated with emphasizing on the control effect. Based on the results, the critical design parameters of the NPCF are identified to be sliding moment ratio ( ρ ) and sliding moment distribution pattern (SMDP). The rational type of SMDP for the seismic design of NPCF is recommended to be the uniform cumulative SMDP. The quantitative relationship between number of stories and rational value of ρ is also recommended. Subsequently, a design method with high efficiency and compatibility is proposed for the NPCF, and two NPCFs are successfully designed using this method, thus further validating the advantages of the DRFDBJ and the reliability of the proposed design method.

A composite wind turbine blade is one of the largest composite structures in the world. These blades are designed to have a fatigue life beyond 20 years. Fatigue testing of these blades is one of the mandatory procedures requested by the international standard. A testing technology exploiting resonance phenomenon has become prevalent as composite wind turbine blades become larger. To control resonance-type fatigue testing, both the moment distribution on the blade calculated by the modal analysis and the testing amplitude calculated by the damping analysis must be known. Historically, there has been no proper damping model able to predict the testing amplitude during resonance-type fatigue testing. This study presents a damping mechanism model based on a new concept, fluid inertia damping caused by a delayed response of flow development, and 132 measured modal damping ratios of four different composite wind turbine blades. Fitting the calculated modal damping ratios to the measured data, general constants of the damping model that do not vary with respect to blade dimensions were found. The results of this study makes a significant step forward in analyzing oscillatory motion of a large structure in resonance beyond resonance-type fatigue testing of a composite wind turbine blade.

A numerical technique to calculate real-space electron transport coefficients in gas under crossed electric and magnetic fields ( $E \times B$ fields) by the propagator method (PM) was newly developed. Components of a centroid drift velocity vector of an electron swarm and its diffusion coefficients defined in the $E$ , $B$ , and $E \times B$ directions were calculated by applying the PM stepwise to the zeroth-, first-, and second-order $x$ , $y$ , and $z$ spatial moment equations derived from the Boltzmann equation. The results calculated for SF6 at $N = 10^{22}\,\,\text{m}^{-3}$ in $E/N$ and $B/N$ ranges of 100–1000 Td and 100–1000 Hx, respectively, agreed with those obtained by Monte Carlo simulations with discrepancies of a few percent. The Hall deflection of the drift velocity vector and the direction dependence of the diffusion coefficients were appropriately reproduced. A relaxation scheme developed for quick convergence of the electron velocity distribution function was effective also in the relaxations of the first- and second-order spatial moment distribution functions. A prototype of the PM as a calculation scheme to derive a set of electron transport coefficients necessary for fluid model simulations of magnetized plasmas was established.

This study explores several types of macroscopic models, by modifying Multiple-Vertical-Line-Element-Model (MVLEM), to represent the coupled concrete shear wall, with different ways of connection to simulate coupling beam. For this purpose, an existing shear wall in which several openings are symmetrically embedded was studied. The wall was analyzed by the microscopic Finite-Element Method (FEM) in ABAQUS. In order to investigate the macroscopic modelling of the mentioned wall, three different macroscopic coupled shear walls, composed of several nonlinear springs, representing flexural and shear behaviors were studied. The main difference among the three walls is in the type of the coupling beam connection used. Hence, three connections were proposed with different stiffnesses. Unlike the connection, the macroscopic coupling beams for the three models were identical based on moment distribution. In order to model the coupling beam, two separate shear walls were considered which were connected to each other from the uppermost part. Responses of the walls under cyclic, monotonic, and dynamic loadings were compared with those of the verified FEM model. The results indicate that the macroscopic wall with moderate connection stiffness has acceptable consistency in terms of static and dynamic responses of the microscopic model.

Reinforced concrete coupled walls are widely used as the main seismic resistant structural system in high-rise buildings. This paper proposes a new mixed beam-shell model for the seismic analysis of reinforced concrete coupled walls with sufficient efficiency and accuracy on the platform of general finite element software MSC.Marc. Boundary elements at the ends of wall piers are simulated by conventional fiber beam-column elements, while the web of the wall pier is modeled by the layered shell element. Coupling beams are simulated by non-conventional fiber beam-column elements, which can not only take into account the shear and shear-sliding deformation together with various failure modes of conventionally reinforced beams, but also the shear and rebar slip deformation of diagonally reinforced beams. RBE2 link elements are utilized to connect the coupling beams to the wall piers. Eight test specimens reported in the literature are used to validate the proposed model. The mechanism of the coupled wall is thoroughly investigated in terms of the beam deformation, base shear and moment distribution as well as axial force of the wall piers. Furthermore, parametric analyses on specimens with different degrees of coupling and types of reinforcement layouts of coupling beams are conducted. Based on the analyses, the influences of the complex behavior and various modeling parameters of coupling beams on the behavior of coupled wall are revealed quantitatively. As a conclusion of the parametric analyses results, it is recommended that the complicated behavior of coupling beams be accurately considered for most cases in the seismic analysis of coupled wall systems.

In the frame analysis, the local analysis model of the joint must follow the behavior of the joint. When completing the elastic global analysis, the initial rotational stiffness of the joints should be known to obtain the reliable moment distribution between the members of the frame. This paper evaluates the existing calculation approach for the initial rotational stiffness of welded rectangular hollow section T joints. Validation with the experiments shows that the current calculation approach significantly underestimates their initial rotational stiffness. Based on the existing experimental data, the paper proposes the improvement for determining the initial stiffness. The second part of the article investigates the effect of the axial force in the main member on the initial rotational stiffness of the joint. The conducted numerical study on square hollow section T joints shows that the reduction of their initial stiffness can reach 50%, when the main member experiences the normal stresses close to yielding. Using the curve fitting approach, the paper proposes and validates a corresponding chord stress function, similar to the existing ones for the moment resistance. acceptedVersion

In this paper, the higher order asymptotic expansion of the moments of extreme from generalized Maxwell distribution is gained, by which one establishes the rate of convergence of the moment of the normalized partial maximum to the moment of the associated Gumbel extreme value distribution.

It is known that when a structure is in neutral equilibrium, only infinitely small disturbing forces are required to maintain the structure in the buckled mode. By making use of this basic principl...

A steel-concrete composite waffle floor system (SCCWFS) that consists of orthogonal steel beams and a flat RC slab has potential applications in long-span building floors because of its large loading capacity, low depth-to-span ratio, and excellent ductility, as demonstrated by a previous experimental program. According to the test results, the spatial composite effect between the orthogonal steel beams and concrete slab significantly influences the performance of the SCCWFS. However, the complexity of the spatial composite effect in the SCCWFS makes it much more difficult to determine the rigidity and the internal force distribution in a routine design practice than the one-way steel-concrete composite floor or the RC waffle slab. To address this problem, a parameterized grillage method is developed in which intrinsic factors are defined to describe the critical properties of the deformation pattern, the reaction force and moment distribution of the SCCWFS; relation factors are defined to relate these properties of the SCCWFS to that of its corresponding steel grillage. Based on the parameterized grillage method, parametric analyses are conducted using a beam-shell mixed finite-element (FE) model and the influence of various parameters on intrinsic and relation factors is investigated, in which the beam height, slab thickness, length-to-width ratio, and so on are shown to be of importance. The data of a total of 5190 numerical models associated with seven parameters covering almost all the practical cases are then obtained, and a step-shaving procedure is proposed to derive formulas that are influenced by multiple variables. Based on the parameterized grillage method and the step-shaving procedure, formulas to predict the vertical displacements, reaction force and moment distribution of the SCCWFS are derived and verified. Finally, design procedures, recommendations and simplified forms of the formulas are proposed, in which the formulas are proved to have an error of approximately 10%.

Seismically designed mid- to high-rise steel moment resisting frames in the United States are commonly constructed with the lowest portion of the first story column embedded into a concrete footing to transfer large moments and forces. Despite their prevalence, these Embedded Column Base (ECB) connections have not been experimentally examined until recently, such that strength estimation methods for other types of connections are usually adapted for their design. Based on recent experiments, current approaches for designing ECB connections are examined, and a new strength characterization method is presented. Mechanisms for internal force transfer within the connection are postulated; these include horizontal bearing of the column flange against the concrete, panel zone shear, and vertical bearing of the embedded base plate against the concrete. The proposed approach has two components: (1) a process for moment distribution between the horizontal and vertical bearing mechanisms, and (2) idealized stress distributions for estimation of associated limit states. The proposed method is able to characterize the experimentally observed specimen strengths with good accuracy, such that the average test-predicted ratio is 1.01, with a coefficient of variation 0.06. No significant bias in accuracy of the method is observed with respect to test variables. Limitations of the study are discussed; these arise from its empirical aspects which may not be generally extrapolated to configurations significantly different from the experiments upon which the method is based.

No appropriate method exists to calculate the in-plane flexibility of Cross Laminated Timber as a floor diaphragm. This flexibility affects the load distribution between shear walls, bracing or cores, as well as adding to local deflections and inter-storey drift. This paper presents a sensitivity analysis based on experimentally measured connection behaviour from the literature and the present study. An important new contributing factor is described: the connection of the floor panels to the supporting wall panels below allows the walls to act as top and bottom chords in the bending and shear of the panel. A new equivalent frame model is described to capture the significant mechanisms of deformation of the diaphragm, validated against a planar finite element model of the elastic behaviour of the panels and the connections between them. The low computational cost of the simplified model allows a wide sensitivity analysis to be carried out, and also makes it suitable for practical design calculations. The flexibility of the floors studied here was seen to be dominated by the slip between panels, rather than panel rotation or bending of the panels themselves. The supporting walls have a strong influence on the moment distribution, but do not strongly influence the slip between panels.

In this paper, an aerodynamic and wing structure is investigated by low-fidelity methods. Bell-shaped lift distribution was rediscovered in the last decade as a perspective alternative to traditional wing design. This leads to lower aerodynamic drag than elliptical lift distribution for a given lift force and root bending moment. Root bending moment is used as a surrogate model of wing structure weight. It is relatively raw simplification introduced by Prandtl to estimate the weight of the spar as a main part of the wing structure. For a more accurate wing weight estimation, the main parts of the wing are dimensioned under CS-23 regulation in this work. The design procedure starts with defining the elementary parameters of the wing shape (chord/twist distribution, wingspan). After geometry generating a non-linear lifting line is used to calculate aerodynamic characteristics for all regime, determined from the flight envelope. The dimensions of a spar, ribs and skin are calculated in the next step of the procedure for given bending moment, load and torque moment distribution. The structure of the wing is assumed as a two-spar, manufactured by aluminum. A target of design is to find out the shape of the wing for given weight. The solution is verified by CFD calculation.

The multiphase pump is the key technology for offshore oil-gas resources exploitation, and great efforts should be made to guarantee its high-efficiency and stable operation. In the present work, a design method of controllable velocity moment in combination of singularity method is proposed for multiphase pump, and the ranges of dimensionless controllable parameters are determined. Under IGVF (inlet gas volume fraction) = 0%, the pressure rise and efficiency of optimization pump I increase by 11.9 kPa and 3.6% in comparison of baseline pump, respectively, and the maximum amplitude of pressure fluctuation in impeller decreases by 23.1%. Under IGVF = 10%, the pressure rise and efficiency of optimization pump II increase by 7.6 kPa and 4.51% in comparison of baseline pump, respectively, and the average pressure fluctuation intensity of impeller decreases by 47.53%. The optimization mechanism is that the rotor-stator interaction and gas-liquid interaction are suppressed in optimization pump with optimal velocity moment distribution.

This paper proposes a novel integrated controller with three-layer hierarchical structure to coordinate the interactions among active suspension system (ASS), active front steering (AFS) and direct yaw moment control (DYC). First of all, a 14-degree-of-freedom nonlinear vehicle dynamic model is constructed. Then, an upper layer is designed to calculate the total corrected moment for ASS and intermediate layer based on linear moment distribution. By considering the working regions of the AFS and DYC, the intermediate layer is functionalised to determine the trigger signal for the lower layer with corresponding weights. The lower layer is utilised to separately trace the desired value of each local controller and achieve the local control objectives of each subsystem. Simulation results show that the proposed three-layer hierarchical structure is effective in handling the working region of the AFS and DYC, while the quasi-experimental result shows that the proposed integrated controller is able to improve the lateral and vertical dynamics of the vehicle effectively as compared with a conventional electronic stability controller.

The Hardy Cross method of moment distribution admits, for any problem, an entire family of distribution sequences. Intuitively, the method involves clamping the joints of beams and frames against rotation and balancing moments iteratively, whether consecutively, simultaneously, or in some combination of the two. We present common versions of the moment distribution algorithm and generalizations of them as both sequential and multiprocess algorithms, with the latter exhibiting the full range of asynchronous behavior allowed by the method. We prove, in the limit, that processes so defined converge to the same unique solution regardless of the distribution sequence or interleaving of steps. In defining the algorithms, we avoid overspecifying the order of computation initially using a sequential, nondeterministic process, and then more generally using concurrent processes.

The reliability and limits of solutions for static structural analysis depend on the accuracy of the curvature and deflection calculations. Even if the material model is close to the actual material behavior, physically unrealistic deflections or divergence problems are unavoidable in the analysis if an appropriate fundamental kinematic theory is not chosen. Moreover, accurate deflection calculation plays an important role in ultimate strength analysis where in-plane stresses are considered. Therefore, a more powerful method is needed to achieve reliable deflection calculation and modeling. For this purpose, a new advanced step was developed by coupling the elasto-plastic material behavior with precise general planar kinematic analysis. The deflection is generated precisely without making geometric assumptions or using differential equations of the deflection curve. An analytical finite strain solution was derived for an elasto-plastic prismatic/non-prismatic rectangular cross-sectioned beam under a uniform moment distribution. A comparison of the analytical results with those from the Abaqus FEM software package reveals a coherent correlation.

Liquefied natural gas (LNG) cryogenic submerged pumps are important transmission devices in LNG terminals and filling stations. In this study, the impeller of a two-stage LNG submerged pump was designed by the quasi-3D hydraulic design method based on the S 1 and S 2 relative stream surfaces theory. In the design procedure, the finite element method (FEM) with a quadrilateral nine-node element was adopted for the S 1 stream surfaces calculation, and the quasi-orthogonal method was used for the average S 2 stream surface calculation. The flow field was obtained by the iterative computations of S 1 and S 2 stream surfaces. Given a reasonable velocity moment distribution along streamlines considered cavitation, the blade drawing was realized by iterating the camber lines and circulation equations on an average S 2 stream surface. Moreover, a steady numerical simulation of the designed pump was conducted. The simulation result showed that the head of the designed pump was 260.15 m and the efficiency was 62.82% at the designed flow rate condition. The net positive suction head required (NPSHr) at the conditions with 0.9 Q 0 , 1.0 Q 0 and 1.1 Q 0 were, respectively, 1.69 m, 2.54 m and 3.12 m, which met the industrial needs. Furthermore, both the cavitation and hydraulic performance of an impeller designed by the method presented in this study were better than those of an impeller which was designed by the two-dimensional method.

Adopting UHPC in practical construction is very expensive due to the high steel fibre content (>2.5 vol%) and passive flexure reinforcement. Aiming at balancing the performance and cost, two UHPC column designs (2000 × 168 × 168 mm) are proposed in the present study. Hollow-core components and steel wire mesh reinforced components were cast with UHPC that contained 1.5 vol% steel fibre, and the impact resistance of both structural types was studied. The test specimens included two hollow-core UHPC columns with square and circular hollow shapes, and two steel wire mesh reinforced UHPC columns with 6 and 10 layers wire mesh reinforcement. The impact scenario was modelled with a 411 kg drop hammer falling freely from 1.25 m height to the mid-span of the test specimen. The results demonstrated that all UHPC specimens remained a flexural response with minimal damage. The developed numerical model captured the impact force, structural deformation and damage with reasonable accuracy. With the validated model, the energy evolution, dynamic shear and moment distribution, residual axial capacity and damage level of post-impact columns were evaluated. The effects of hollow section shape and ratio, axial load level, and longitudinal reinforcement ratio for hollow-core UHPC columns and the effects of layers of steel wire mesh for steel wire mesh reinforced UHPC columns were investigated. Compared with other hollow-core UHPC columns under the impact velocities between 4.95 m/s – 6.64 m/s, UHPC columns with a circular hollow section and 15% hollow ratio was the most effective in balancing the cost and impact resistance. For steel wire mesh reinforced UHPC columns, the column with steel wire mesh strengthening in the whole section had better impact resistance than its counterpart that only had wire mesh reinforcement in the tensile zone.

Steel cantilevers are very different from the simply supported beams under uniform bending which provide the basis for designing steel members against lateral buckling. Cantilevers have different end restraint conditions, while the most critical loading condition for cantilevers is one of concentrated end load leading to a linear moment distribution. Thus the elastic lateral buckling formulations for uniform bending of simply supported beams used more generally for design are inappropriate for cantilevers. The mono-symmetric yield patterns in simply supported beams with residual stresses in uniform bending are of opposite sense to those of cantilevers because of the opposite sense of the bending moments. Thus formulations which take account of the effect of mono-symmetry on the inelastic lateral buckling of simply supported beams are inappropriate for cantilevers. Further, the linear cantilever moment distribution leads to very localised yielding instead of the uniform yielding of beams under uniform bending. This paper studies the inelastic lateral buckling of cantilevers in order to produce better design guidance than that currently based on the inelastic buckling of simply supported beams in uniform bending. The effects of mono-symmetry on the elastic buckling of beams and cantilevers are first investigated, and then the effects of the mono-symmetric non-uniform yielding patterns which complicate the prediction of the inelastic buckling resistances of cantilevers are studied. Cantilevers with reduced (instead of rigid) end warping restraints occur in overhanging beams, and so the effects of yielding on overhanging segments are also studied. These studies are used to develop simple approximate methods for designing cantilevers and overhanging segments against inelastic lateral buckling.

An extensive numerical study of Class 4 section beams at elevated temperature is described in the paper. The study focuses on welded I-section beams of slender web and flange and covers beams of constant height as well as beams with significant web taper ratio. The numerical parametric study extends previous test results significantly in terms of various temperatures, section slenderness for flange and webs considering also combination of more stocky flanges with a slender web, various beam slenderness and moment distribution along the beam. Based on the numerically calculated resistances, a simple design rule was developed for both constant and web tapered members. The proposed model is believed to be predicting the beam capacity accurately with formulas simple enough to be used and accepted by structural engineers.

Introduction Structural analysis and design Structural idealisation Structural members and elements Structural systems Types of loads Supports for structures Statics of structures: Equilibrium and support reactions Introduction Coordinate systems Force Moment of a force Resultant force and moment Reactions Free-body diagram Equilibrium equations for planar structures External statical determinacy and stability Internally stable structures Determination of reactions Equilibrium and reactions in three-dimensional structures Problems Internal actions of beams and frames Introduction Internal actions at a cross-section Sign convention of internal actions Determination of internal actions and statical determinacy Axial force, shear force and bending moment diagrams Problems Statically determinate trusses Introduction Assumptions for truss analysis Sign convention and notation An introduction to the method of joints Method of joints in matrix form Method of sections Statical indeterminacy and stability of trusses Deformation of trusses Trusses with loaded members Space trusses Problems Euler-Bernoulli beam model Introduction Equilibrium of a small length of beam Kinematic (or strain-displacement) equations Constitutive equations Method of double integration Governing differential equations (as a function of displacements) Relationship between bending moment, shear force and member loading Problems Slope-deflection methods Introduction Method of double integration with step functions Moment-area method Conjugate beam method The slope-deflection equations Problems Work-energy methods Strain energy The work theorem Virtual work Virtual work applied to trusses Virtual work applied to beams and frames Castigliano's theorem Problems The force method Introduction The force method applied to trusses The force method applied to beams and frames Problems Moment distribution Introduction Basic concepts Continuous beams Frames without sidesway Frames with sidesway Problems Truss analysis using the stiffness method Overview of the stiffness method Sign convention, notation, coordinate systems and degrees of freedom Derivation of the stiffness matrix in local coordinates Transformation between local and global coordinate systems Truss element in global coordinates Assembling Solution procedure Calculation of internal actions Nodal coordinates Space truss Problems Beam analysis using the stiffness method The beam element Derivation of the stiffness matrix Beam element in global coordinates Assembling of the stiffness elements Member loads Solution procedure and post-processing Problems Frame analysis using the stiffness method The frame element Derivation of the element stiffness matrix Transformation between local and global coordinate systems Frame element in global coordinates Member loads Assembling, solution and post-processing Problems Introduction to the finite element method Introduction Euler-Bernoulli beam model Timoshenko beam model Problems Introduction to the structural stability of columns Introduction Assumptions Critical load from equilibrium Critical load from potential energy Buckling of an elastic column Effective buckling length Buckling stresses Imperfections in columns Problems Introduction to nonlinear analysis Introduction Nonlinear material properties Illustrative examples Nonlinear analysis using the Newton-Raphson method Finite element analysis using the Newton-Raphson method Problems Appendices Index

The need for upgrading understrength bridges in the United States has been well documented in the literature. In this thesis, two methods of strengthening are presented: post-tensioning of the positive moment regions of the bridge stringers and the addition of superimposed trusses at the piers. The use of these two systems is an efficient method of reducing flexural overstresses in undercapacity bridges. The objective of the research described in this thesis was to develop a design methodology to assist bridge engineers with designing a strengthening system to obtain the desired stress reductions. In addition, one such strengthening system was designed for use on a three-span continuous steel stringer bridge in the field. A design methodology was developed to simplify the design process for the strengthening system on a typical continuous-span composite bridge. As a result of the longitudinal and transverse force distribution, the design methodology presented in this thesis for continuous-span composite bridges is extremely complex. To simplify the procedure, a spreadsheet has been developed for use by practicing engineers. The force and moment distribution fraction formulas developed in this study are primarily for the Iowa DOT VI2 and V14 three-span four-stringer bridges. These formulas may be used on other bridges if they are within the limits stated in this study. Use of the distribution fraction formulas for bridges not within the stated limits is not recommended. The bridge selected for strengthening was in Cerro Gordo County near Mason City, Iowa on County Road B65. A strengthening system composed of post-tensioning and superimposed trusses was designed to remove overstresses that occurred when the bridge was subjected to Iowa legal