Semi-rigid Models Research Articles

Nonlinear inelastic analysis of space semi-rigid steel frames subjected to static load using plastic-zone method

A new hybrid element based on plastic-zone method is proposed for static nonlinear analysis of space semi-rigid steel frames. Four zero-length nonlinear rotational springs are added to the beam ends to model both in- and out-of-plane connection rotational behavior with appropriate semi-rigid connection models. The von Mises yield criteria are applied to govern material plasticity along the member length and throughout the cross-section using Newton–Cotes integration points. The modified generalized displacement control method is used to solve the system of nonlinear equilibrium equations. Some numerical examples are investigated to show the reliability and visual illustration of the proposed hybrid element.

Formula omitted]-type doubling in the rotational spectrum of CH[formula omitted]–He: A group theoretical explanation

In a previous paper, we reported the pure rotational spectrum of the CH3+–He ion observed in a 22-pole ion trap by IR-MW double resonance spectroscopy [Töpfer et al. (2018)]. In that work the K=1 rotational levels in the ground state of the ion were observed to be split, i.e. the K-type doubling was observed. This finding would be consistent with a slightly asymmetric rotor of Cs symmetry, although ab-initio calculations predict that the equilibrium structure of the ion is of C3v symmetry. In the present study we inspect the energy-level correlation-diagram between the semi-rigid symmetric-top (C3v), the free internal-rotor (C3v(M)), and the semi-rigid asymmetric-top models (Cs), by using group theory, especially the correlation and reverse correlation in the symmetry representations. We find that the lowest K=1 rotational levels of the CH3+–He ion can be of A1⊕A2 symmetry rather than of E symmetry, and thus they can be split depending on the nature of the C–He bending vibration.

RESEARCH ON THE SEMI-RIGID COLUMN BASE OF REINFORCED CONCRETE

The stress state of the structure from external force, mainly depends on the rigidity when the deformation is minimum and depends on the load capacity when it comes to large deformation. The joints of ordinary reinforced concrete buildings are rigid joints, and the bending stress is focused on the column base of the first-floor columns, therefore the cross section of the first-floor columns turn large. Along with this, various problems are considered, such as excessive areas of the cross-section on the upper floors, and complications of the reinforcement, due to disunity of the column cross-sections. Given these backgrounds, semi-rigid column bases were developed to control the bending stress distribution of the columns. In this study, bending shear experiments were conducted in order to understand the structural characteristics of the semi-rigid columns depending on cross-sectional shapes, and the behavior of the semi-rigid columns were confirmed. In addition, semi-rigid column analysis models with various cross-sectional shapes were proposed, and the effective usages of semi-rigid columns with types of cross-sectional shapes were proposed.

RESEARCH ON THE SEMI-RIGID COLUMN BASE OF REINFORCED CONCRETE

The stress state of the structure from external force, mainly depends on the rigidity when the deformation is minimum and depends on the load capacity when it comes to large deformation. The joints of ordinary reinforced concrete buildings are rigid joints, and the bending stress is focused on the column base of the first-floor columns, therefore the cross section of the first-floor columns turn large. Along with this, various problems are considered, such as excessive areas of the cross-section on the upper floors, and complications of the reinforcement, due to disunity of the column cross-sections. Given these backgrounds, semi-rigid column bases were developed to control the bending stress distribution of the columns. In this study, bending shear experiments were conducted in order to understand the structural characteristics of the semi-rigid columns depending on cross-sectional shapes, and the behavior of the semi-rigid columns were confirmed. In addition, semi-rigid column analysis models with various cross-sectional shapes were proposed, and the effective usages of semi-rigid columns with types of cross-sectional shapes were proposed.

Seismic behaviour of Taiwanese timber complex brackets subjected to out-of-plane loading

The Taiwanese Dieh-Dou-type complex brackets used in traditional timber buildings are commonly believed to sustain both in-plane and out-of-plane loadings of the main frame during seismic events. From past statistical investigation, single-tier, double-tier and triple-tier asymmetric bracket designs were chosen as test subjects. A series of quasi-static cyclic tests was applied to full-scale specimens to evaluate their seismic behaviour when subjected to out-of-plane loading. The test specimens generally exhibited significantly higher resistance when all horizontal members sustained compression. The Gong members functioned like braces and subsequently led to enhanced resistance. However, when the global structure was subjected to tension, the joints of Gong, purlin support and purlin members were more likely to be pulled out. The counter-resistance force observed from the tension side resembled that of rigid-body rotation. The triple-tier specimen sustained more serious damage than the other two types, where the middle Dou member was more prone to split due to stress concentration. The proposed bi-linear semi-rigid spring models were in good agreement with the test results, so the general assumptions made were valid.

Nonlinear Analysis of Flat Steel Frame Structure With Semi-rigid Connection Under Static Load

The paper aims to analyze the elasticity-plasticity of a flat steel frame structure with a beam-column connection that is a semi-rigid connection; three-spring semi-rigid link models (two linear displacement springs and one rotating displacement spring); It includes hard areas at the beam-column position, with an ideal flexible-plastic material model. Based on that, it developed algorithms by PTHH method using step-by-step applying load method and programmed to determine displacement-internal force when make semi-rigid nonlinear connection in MATLAB programming language; consider the melting conditions of the section, including the influence of moments, vertical force and shear force. Make a numerical illustration with a two stage-one span steel frame.

Effect of semi-rigid locking screws on the stiffness of a fracture-fixation construct: A conceptual finite-element study

Strong stiffness provided by locking-plate system has resulted in nonunion and delayed union for long bone fracture. Longer bone plate can lengthen the working length to reduce the structural stiffness of the fixation device but will enlarge skin incision. Using the semi-rigid locking screw may be helpful but the efficacy was unclear. In simulated fracture model, four rigid locking screws were continually inserted beneath the fracture gap. The other four rigid/semi-rigid locking screws were equally distributed or concentrated at screw holes superior to the fracture gap. Axial compressive load was exerted to compare the biomechanical performance under various screw configurations and plate working length. Results revealed that using the semi-rigid locking screws, the structural stiffness of the fixation structure were lowered by 29.5%–45.1% comparing to the model with the same screw configuration using rigid locking screws. Semi-rigid screw models with shorter working length represented comparable flexibility of the fixation structure to the rigid locking screw model with longer working length. Compared to rigid locking screw, semi-rigid locking screw may provide similar flexibility with shorter bone plate, which may be beneficial to reduce the required plate length so that the skin incision may be minimized for fracture reduction.

Effect of connection modeling on the seismic response of steel braced non-moment resisting frames

Non-moment beam-to-column connections, which are usually referred to as simple or shear connections, are typically designed to carry only gravity loads in the form of vertical shears. Although in the analysis of structures these connections are usually assumed to be pinned, they may provide a small amount of rotational stiffness due to the typical connection details. This paper investigates the effects of this small rotational restraint of simple beam-to-column connections on the behavior and seismic response of steel braced non-moment resisting frames. Two types of commonly used simple connections with bolted angles, i.e., the Double Web angle Connection (DWC) and Unstiffened Seat angle Connection (USC) are considered for this purpose. In addition to the pinned condition - as a simplified representation of these connections - more accurate semi-rigid models are established and then applied to some frame models subjected to nonlinear pushover and nonlinear time history analyses. Although the use of bracing elements generally reduces the sensitivity of the global structural response to the behavior of connections, the obtained results indicate considerable effects on the local responses. Namely, our results show that consideration of the real behavior of connections is essential in designing the column elements where the pin-connection assumption significantly underestimates design of outer columns of upper stories.

Grey Relational Analysis of Fatigue Performance of Semi-Rigid Pavement Structure

A number of different semi-rigid pavement structure models are established to perform calculation and the results are led into the calculation software nSoft to analyze and acquire the fatigue property of different semi-rigid pavement structure models. The grey relational analysis of different semi-rigid pavement structure models fatigue properties are done based on the grey system theory to gain the key influence parameter on semi-rigid pavement structure fatigue performance. The research conclusion has certain instruction function to design pavement structure with excellent anti-fatigue performance.

SB5-B 소형차 충돌속도의 상향 가능성 평가

SMART Highway 종방향 배리어 상위등급 SB5-B 대형차 충돌조건을 만족하면서 120km/h의 소형차충돌속도를 130km/h로 상향시킬 수 있는 가능성이 조사되었다. 실물 충돌시험의 결과에 Calibrate된 입력 변수를 적용한 컴퓨터 시뮬레이션을 통하여 120km/h 소형차 충돌속도에 대한 차량의 종방향(longitudinal)과 횡방향(transverse) 속도변화가 THIV 한계를 만족시킬 수 있도록 다양한 배리어 모델이 개선되었고 이 과정을 통해 결정된 배리어 모델이 SB5-B 실물충돌시험을 통과하였다. 통과된 배리어 모델 slip block-out 날개의 각도를 변화시키면서 120km/h 소형차 충돌속도의 상향가능성을 유한요소해석(FEA)을 통하여 조사하고 실물차량 충돌시험을 수행하였다. 소형차충돌속도 130km/h에 대한 표준시험 여건이 갖추어 진다면 소형차 충돌속도 130km/h로 상향시킬 수 있는 가능성이 높은 것으로 조사되었다. Satisfying the large car impact condition of the high level SB5-B for "SMART Highway" longitudinal barriers, the possibility of increase of the small car impact velocity from 120km/h to 130km/h was investigated. Through computer simulation using input parameters calibrated to full-scale crash test results, various longitudinal semi-rigid barrier models were improved such that for the small car impact speed of 120km/h the change of longitudinal and transverse velocities of the impact vehicle can satisfy the THIV limit. The barrier model determined through this process satisfied the performance assessment criteria for SB5-B impact conditions. Varying the wing angle of slip block-outs of the passed barrier model, the possibility of increase of the small car impact velocity was investigated by FEA and a full-scale crash test was conducted. It has been shown that the possibility to increase the small car impact speed to 130km/h is high if the test facility condition for 130km/h impact velocity is better equipped.

Optimum design of steel frames with semi-rigid connections using Big Bang-Big Crunch method

The Big Bang-Big Crunch (BB-BC) optimization algorithm is developed for optimal design of non-linear steel frames with semi-rigid beam-to-column connections. The design algorithm obtains the minimum total cost which comprises total member plus connection costs by selecting suitable sections. Displacement and stress constraints together with the geometry constraints are imposed on the frame in the optimum design procedure. In addition, non-linear analyses considering the P- effects of beam-column members are performed during the optimization process. Three design examples with various types of connections are presented and the results show the efficiency of using semi-rigid connection models in comparing to rigid connections. The obtained optimum semi-rigid frames are more economical solutions and lead to more realistic predictions of response and strength of the structure.

The phase behavior, structure, and dynamics of rodlike mesogens with various flexibility using dissipative particle dynamics simulation

We present a systematic dissipative particle dynamics (DPD) study on the phase behavior, structure, and dynamics of rodlike mesogens. In addition to a rigid fused-bead-chain model with RATTLE constraint method, we also construct a semirigid model in which the flexibility is controlled by the bending constant of k(φ). Using this notation, the rigid model has an infinite bending constant of k(φ)=∞. Within the parameter space studied, both two kinds of models exhibit the nematic and smectic-A phases in addition to the isotropic and solid phases. All of the phase transitions are accompanied by the discontinuities in the thermodynamical, structural, and dynamical quantities and the hysteresis around the transition points, and are therefore first order. Note that the obtained solid state exhibits an in-layer tetragonal packing due to the high density. For the rigid model, the simulations show that the liquid crystal phases can be observed for mesogens with at least five beads and the nematic phase is the first one to appear. More importantly, the phase diagram of seven-bead-chain models is obtained as a function of k(φ) and temperature. It is found that decreasing the value of k(φ) reduces the anisotropy of molecular shape and the orientational ordering, and thereby shifts the liquid crystal phases to the lower temperature end of the phase diagram. Due to the different k(φ) dependence of phase transition temperatures, the nematic phase range exhibits a more marked narrowing than the smectic-A phase as k(φ) is reduced, implying that the flexibility has a destabilizing effect on the nematic and smectic-A phases. We also have investigated the anisotropic translational diffusion in liquid crystal phases and its temperature and flexibility dependence. In our study, we find that the phases formed, their statical and dynamic properties, as well as the transition properties are in close accord with those observations in real thermotropic liquid crystals. It is clear that both the rigid and semirigid models we used are valuable models with which to study the behavior of thermotropic liquid crystals using DPD algorithm.

Local Delamination Buckling of Laminated Composite Beams Using Novel Joint Deformation Models

Local delamination buckling formulas for laminated composite beams are derived based on the rigid, semirigid, and flexible joint models with respect to three bilayer beam (i.e., conventional composite, shear-deformable bilayer, and interface-deformable bilayer, respectively) theories. Two local delamination buckling modes (i.e., sublayer delamination buckling and symmetrical delamination buckling) are analyzed and their critical buckling loads based on the three joint models are obtained. A numerical finite-element simulation is carried out to validate the accuracy of the formulas, and parametric studies of delamination length ratio, the transverse shear effect, and the influence of interface compliance are conducted to demonstrate the improvement of the flexible joint model compared to the rigid and semirigid joint models. The explicit local delamination buckling solutions developed in this study facilitate the design analysis and optimization of laminated composite structures and provide simplified and improved practical design equations and guidelines for buckling analyses.

Validation of Reynolds-Averaged Navier-Stokes Simulations for International America’s Cup Class Spinnaker Force Coefficients in an Atmospheric Boundary Layer

Three semirigid models for International America's Cup Class spinnakers were tested in a wind tunnel with a simulated atmospheric boundary layer. These experiments were also simulated using a commercial Reynolds-averaged Navier-Stokes (RANS) solver with three different turbulence models. A comparison between the experimental and numerical force coefficients shows very good agreement. The experimentally measured differences in the driving force coefficients among the three sails were predicted well by all three turbulence models. The realizable k-e model produced the best results, and the standard k-e model produced the worst. The Reynolds stress model did not perform significantly better than the standard k-e model. The results suggest that RANS can be used as a design tool for optimizing spinnaker shape.

Novel joint deformation models and their application to delamination fracture analysis

Split beam type of fracture specimens is commonly used in the delamination evaluation of laminated composites. The compliance and energy release rate (ERR) of the specimens are examined in this study in the new light of the crack tip deformation. Three joint deformation models (i.e., the rigid, semi-rigid, and flexible joint models) describing the different degrees of crack tip deformation are obtained based on three corresponding bi-layer beam theories (i.e., the conventional composite beam, shear deformable bi-layer beam, and interface deformable bi-layer beam). Due to different considerations of the interface displacement compatibility in each bi-layer beam theory, these joint models, among which the semi-rigid and flexible joint ones are new, show three distinct levels of accuracy in predicting the crack tip deformation. By using these two novel joint models, the new terms, which are “missing” in the rigid joint model, are recovered for the compliances and ERRs of six common delamination specimens. As a validation, an asymmetric DCB specimen is examined by three joint models, as well as the numerical finite element analysis, and three distinct accuracy levels of the solutions are revealed again in comparison with finite element analysis. It is shown that the rigid joint model is the most approximate due to neglecting the crack tip deformation, the semi-rigid model provides better solutions due to partially inclusion of the joint deformation, and the flexible joint model is the most accurate because of the fully consideration of the crack tip deformation. The distinction on accuracy also indicates the significant effect of joint (crack tip) deformation on delamination specimen analysis. The novel semi-rigid and flexible joint deformation models presented in this study provide explicit closed-form solutions of fracture parameters which can be easily adopted in practice.

Comparison of rotational energies and rigidity of OCS–para-H2 and OCS–4He complexes

We analyze the nature of the rotational energy level structure of the OCS-He and OCS-H_2 complexes with a comparison of exact calculations to several differentdynamical approximations. We compare with the clamped coordinate quasiadiabatic approximation that introduces an effective potential for each asymmetric rotor level, with an effective rotation Hamiltonian constructed from ground state averages of the inverse of the inertial matrix, and investigate the usefulness of the Eckart condition to decouple rotations and vibrations of these weakly bound complexes between linear OCS and 4He or H_2. Comparison with exact results allows an assessment of the accuracies of the different approximate methods and indicates which approaches are suitable for larger clusters of OCS with 4He and with H_2. We find the OCS-H_2 complex is considerably more rigid than the OCS-4He complex, suggesting that semi-rigid models are useful for analysis of larger clusters of H_2 with OCS.

In-plane shear properties of the wood-based sandwich panel as a small shear wall evaluated by the shear test method using tie-rods

The fundamental in-plane shear properties were investigated for the wood-based sandwich panel of plywood-overlaid low-density fiberboard (SW) manufactured at a pilot scale to develop it as a shear wall. The shear test method using tie-rods standardized for shear walls was applied to SW with dimensions of 260 mm square and 96 mm thick as a small shear wall and to plywood (PW) and thick low-density fiberboard (FB). The shear modulus and shear strength of PW, FB, and SW were determined. To measure the shear deformation angle, a displacement meter and strain-gauge were used. The shear moduli of PW (0.68 g/cm3) and FB (0.25–0.35 g/cm3) were 460 and 21–58 MPa/rad, respectively. The shear modulus of SW as a composite was analyzed. Some experimental models of SW were proposed (i.e., rigid-α, rigid-β, flexible, and semirigid models). The shear modulus of SW (0.35–0.40 g/cm3) evaluated based on the rigid-α and semirigid models were 73–89 and 109–125 MPa/rad, respectively. The theoretical shear modulus of SW was calculated to be 110–129 MPa/rad.

The accurate computation of partition functions in non-rigid molecules

A software tool for the computation of equilibrium properties in flexible, non-rigid, molecular systems is developed. The program can use semi-rigid and anharmonic models to obtain the rotational and vibrational contributions to the partition function. In addition, a semi-empirical procedure is developed to refine the partition function using experimental information. The program is employed to determine the quantitative performance of the semi-classical closed form for the computation of the rotational partition function. At standard temperature and for medium-size molecules, the error of the usual semi-classical form is found to be smaller than 0.1%. The refinement procedure is tested using the available values for the partition function of the (HF) 2 hydrogen-bonded complex. The partition function is computed using ab initio data obtained at the MP2(Full)/6-311 + + G(2 df,2 pd) level. Three models are tested: a pure harmonic model and two anharmonic models. In the anharmonic models, the potential for the hydrogen-bond stretching is described by a Taylor series or by a Morse function. The refinement technique is able to reproduce exactly the reference data in the three cases.

Analysis program for the design of flexibly jointed frames

To estimate second-order effects on the behavior and strength of steel frames with semi-rigid connections, as well as to perform practical frame design easily and rationally, an attempt was made to develop a structural analysis program considering the characteristics of semi-rigid connections in a direct manner. The program was developed with the following three main routines: 1. 1. The practical procedure for structural analysis is based on a simplified method presented previously. This method uses the closed-form elastic solutions of beam-columns and takes into account the inelastic property of connections. 2. 2. The program PACOM (Parameter Analysis of Connection Models) prepares the parameters of semi-rigid connection models using the program SCDB (Steel Connection Data Bank). 3. 3. The graphic routine draws the general configuration and sectional force diagrams of the overall structure, the hysteresis loop in relation to the connection moment and relative rotation. The development of this system was made on an engineering workstation with a drawing function on a CRT display.

Higher order effects in beam-beam deflection

Beam-beam deflection scan is a useful tool, both in the SLC and in future linear colliders, for extracting information about the beam position, size and luminosity. This technique poses nontrivial challenges to the instrumentation in its own right. The understanding of all aspects of beam-beam deflection, in particular that of disruption, is therefore crucial to a successful implementation of this technique. When disruption effects become strong mainly due to increased beam intensity per bunch, the simple rigid-bunch formula for beam-beam deflection is no longer valid. In this report we discuss the general modification to the rigid beam-beam deflection formula in the presence of disruption using various methods including analytical calculation, rigid and semi-rigid two-disk models, and simulation. The impact on the realistic beam-beam deflection in the SLC is also discussed.