Allowable Bending Moment Research Articles

System reliability and sensitivity analysis of lateral loaded pile considering soil’s spatial variability

ABSTRACT Probabilistic analysis has been widely used to assess the inherent uncertainty of variables in laterally loaded pile systems, but the calculation is still difficult and time-consuming. The present study presents an efficient probabilistic analysis framework for a laterally loaded pile system. The performance of the system is defined as the lateral deflection at the pile head and maximum bending moment of the pile shaft, corresponding to two failure modes. Within this framework, the spatial variability of the soil and the correlation between failure modes are considered by the random field theory and the First-Order Reliability Method, respectively. Moreover, the Sequential Compounding Method is used as an efficient tool to determine the system reliability indexes. The framework is confirmed by comparing the reliability indexes of failure modes and systems with those of the Monte Carlo Simulation Method. Furthermore, a parametric analysis and system sensitivity analysis are performed. The results show that the auto-correlation distance, allowable lateral displacement at the pile head, and allowable bending moment of the pile shaft have a great influence on reliability indexes of failure modes and system, and the major parameter of soil in affecting pile is the elastic modulus compared with the undrained shear strength.

Study on the cell configurations and mechanical strength of planar-type solid oxide fuel cells

For solid oxide fuel cells, the following cell configurations have been developed: electrolyte-supported cell (ESC), anode-supported cell (ASC), and metal-supported cell (MSC). In this study, to compare the mechanical load tolerance corresponding to each of the abovementioned cell configurations, the curvature and residual stress were calculated using the Euler–Bernoulli beam theory. The results indicated that when the cells were flattened under the application of an external bending moment, the stress gradient in each layer of the cell disappeared, and the maximum stress in the cell was shown to decrease. Eventually, the failure probability of the cell substrate was demonstrated to take the smallest value. The allowable bending moments for the cell substrates were as follows: −0.17 to 0.08 Nm for ESC, −0.18 to 0.11 Nm for ASC, and −0.29 to 0.40 Nm for MSC at room temperature. Thus, MSC was found to possess the highest bending moment tolerance.

Pile groups under vertical and inclined eccentric loads: Elastoplastic modelling for performance based design

This paper presents a numerical study of 3×3 pile groups embedded in clay under vertical and inclined eccentric loads. Simplified modelling, based on elastic beams embedded in a soil continuum, is used to explore the soil-pile-cap response. This simple model allows rigorous treatment of the 3D foundation geometry and local soil plasticity, demonstrated through validation with 3D finite element analysis. The numerical results reveal that complex roto-translational displacements of the pile group are induced by eccentric or inclined loads, with highly nonlinear relationships when soil plasticity is considered. Interestingly, vertical eccentric loads mobilise the lateral soil resistance at large cap displacements. Thus, while existing t-z type models are shown to be adequate for serviceability predictions, they could provide overly-conservative estimates of the ultimate load capacity. Also, foundation internal forces can exceed allowable bending moments of reinforced concrete piles under multi-directional loads. For performance based design of pile groups under inclined eccentric actions, engineers should estimate the impact of soil yielding on both displacements and rotations of the cap, to satisfy limit state requirements. Dimensionless charts are presented, which describe the reduction in vertical capacity, for a prescribed cap displacement, as a function of load eccentricity and inclination.

Shape optimization of no-tension arches subjected to in-plane loading

In this paper a novel method for the shape optimization of tapered arches subjected to in-plane gravity (self-weight) and horizontal loading through compressive internal loading is presented. The arch is discretized into beam elements, and axial deformation is assumed to be small. The curved shape of the tapered arch is discretized into a centroidal B-spline curve with beam elements. Constraints are imposed for allowable axial force and bending moment in the arch so that only compressive stress exists in the section. The computational cost for optimization is reduced, and the convergence property is improved by considering the locations of the control points of B-spline curves as design variables. The height of section is also modeled using a B-spline function. A section update algorithm is introduced in the optimization procedure to account for the contact and separation phenomena and to further speed up the computation process. The objective function to minimize the total strain energy of the arch under self-weight and horizontal loading. Numerical examples are presented that demonstrate the effectiveness of the proposed method. To validate the findings, the properties of the obtained optimal shapes are compared to shapes obtained by a graphic statics approach.

Structural performance of non-plastered modular straw bale wall panels under transverse and gravity loads

Abstract Straw bale construction has a proven track record as a viable alternative for residential construction. Structural (load-bearing) straw bale panels typically consist of stacked straw bales and plaster skins. These systems exploit the structural capacity of the plaster/straw composite. The plaster is critical for providing structural strength and stiffness, as well as protection against pests, moisture, and fire. However, plastering bales is labour intensive and costly. A recent development has been dry bale wall (DBW) panels. These panels have a perimeter timber frame, recycled wood sheathing on both sides and straw bale infill. By eliminating the labour-intensive plastering of traditional straw-bale walls, DBW panels can be constructed rapidly and off-site in a sheltered environment, thus preventing exposure of the straw to moisture during construction. This paper describes the gravity and transverse load testing (based on ASTM E72 -15 [3] ) of DBW panels in-filled with wheat straw bales. To evaluate their strength capacity and failure modes is described. The out-of-plane flexural (OPF) tests exhibited a mean allowable bending moment of 1.80kNm with a factor of safety of 3. The axial compression (AC) tests exhibited a mean allowable line load of 22.8 kN/m with a factor of safety of 2.5. The local flexural header beam (HP) tests exhibited an allowable line load of 11.2 kN/m with a factor of safety of 3. The OPF and AC capacities of the DBW exceeded the Abbasi (2014)’s conventional structural insulated (STUD) wall. However, the DBW’s header beam strength and stiffness was inferior to Abbasi (2014)’s STUD wall.

Port-Harcourt International Airport Terminal Building Assessment of Structural Safety and Serviceability

To accomplish the renovation and upgrade of the Port Harcourt International Airport Terminal Building, one aspect of the work required that the VIP Lounge at the First floor, be relocated to 20m offset from its original location. To relocate the VIP lounge, its reinforced concrete structure at its original location, had to be demolished and reconstructed at the new location. This structural assessment was initiated because of the change in resistance to the structure resulting from this partial demolition, and reconstruction. Model based Safety and Serviceability assessment methodologies comprising; Acquisition of data of loading and resistance, Calculation of load effects on structural models, and Safety and Serviceability verification, was utilized in the assessment of the existing structure of the Port Harcourt International Airport Terminal building. A summary of the Safety and Serviceability verification show that, for the structure at both the original location and the new location of the VIP lounge, the allowable Columns loads and maximum bending moments exceeded the actual column loads and maximum bending moments; and the allowable bending moments of Beams exceeded the actual maximum bending moments in the Beams. This indicates that the structure, at neither location, is overloaded. In addition there were no visible cracks or ruptures, the telltale signs of damage to the structure, on any of the elements of the structure.

Analysis of the metal-to-metal contact flange joint subject to external bending moment

Metal-to-metal contact flange joints are widely used in nuclear and petrochemical industry for severe conditions, because of the relative stability of the sealing gasket stress under complex service condition. In the present work, finite element models were used for analyzing the stress distribution of metal-to-metal contact pipe flange connection under different internal pressures, temperatures, and external bending moments to evaluate the sealing and strength performance. A metal-to-metal contact pipe flange connection device was also experimented. It was found that the results of the axial bolt force and flange hub stress obtained from the experiments were in fairly good agreement with the finite element simulations. The leakage test of metal-to-metal contact type gasket was conducted to highlight its leakage characteristics under different temperatures. The methods to determine the maximum allowable bending moment of a metal-to-metal contact flange joint according the strength criterion and the sealing criterion were analyzed. The results showed that the maximum allowance bending moment was determined by the strength criterion rather than by the sealing criterion with different thermal loadings when the initial bolt-up stress was high enough to achieve metal-to-metal contact contact.

Optimization of the bending stiffness of beam-to-column and column-to-foundation connections in precast concrete structures

Abstract This work involved the structural optimization of precast concrete rigid frames with semi-rigid beam-to-column connections. To this end, several frames were simulated numerically using the Finite Element Method. Beams and columns were modeled using bar elements and their connections were modeled using spring elements, with variable bending stiffness. The objective function was based on the search of the least stiff connection able to ensure the global stability of the building. Lastly, a connection model with optimal stiffness was adopted to design the frame. Semi-rigid beam-to-column connections with a constraint factors of 0.33 sufficed to ensure the maximum allowable horizontal displacement and bending moment of the connection, with a global stability parameter of 1.12. This confirms that even connections with low constraints generate significant gains from the structural standpoint, without affecting construction and assembly-related aspects.

A Study on the Behavior of Single- and Twin-Gasketed Flange Joint Under External Bending Load

Gasketed flange joints are widely used in pressure vessels and piping systems. They are subjected to bending load due to differential thermal expansion, wind load, self-weight, etc., in addition to assembly and internal fluid load. Most of the flange designs are based on equivalent pressure method to include the effect of external bending loads. The behavior of gasketed flange joint is complex due to the nonlinear hysteretic behavior of gasket material and contact interfaces between joint members. It becomes more complex when the joint is subjected to bending load at elevated temperatures. In the present work, performance of a flange joint has been studied under internal pressure and external bending load at elevated temperatures. A 3D finite element model is developed, considering the nonlinearities in the joint due to gasket material and contact between its members along with their temperature-dependent material properties. The performance of joint under different bolt preloads, internal fluid pressures, and temperatures is studied. Flange joint with two gaskets (twin-gasketed flange joint, TGJ) placed concentric is also analyzed. The results from finite element analysis (FEA) are validated using four-point bending test on gasketed flange joint. The sealing and strength criteria are considered to determine the maximum allowable bending moment at different internal fluid temperatures, for both single- and twin-gasketed flange joints with spiral wound gasket. Twin gasket is able to withstand higher bending moment without leakage compared to single gasket. Results show that the allowable load on flange joint depends on operating temperature and gasket configuration.

Bolts Connection Technique Of Bamboo In Construction Work

The construction industry is increasingly developing and growing rapidly with more advanced technologies. The world timber demand is increasing at a rapid rate but the timber supply is however depleting. It has been found through research that bamboo can suitably replace timber and other materials in constructions. This study was conducted to investigate the structural strength of bamboo connections involving only spliced joint and compared with control samples strength of bamboo which were not connected. Bending test was conducted on four types of bamboo connection structures which werehalf-lapped splice joint using 3 bolts, half-lapped splice joint using 2 bolts, side plate splice joint, sleeves and insert joint and control sample bamboo. Every connection had six samples to determine the structural strength of the bamboo connection. From the tests conducted, the maximum load that can be borne by the bamboo structure and the bending ofthe bamboo structure will be obtained. Data were compared with the theoretical calculation based on the study of Janssen's. The connection structure that can bear maximum load was sleeves and inserts which was 5.997 kN. The control samples bamboo maximum load was 4.504 kN. Meanwhile, half-lapped splice joint using 3 bolts and 2 bolts were 4.789 kN and 4.04 kN. Structural connections that carriedthe lowest load was side plate splice joint which was only 2.659 kN.Compared with the bending moment of Janssen’s theory, all the connections did not exceed the maximum allowable bending moment. This showed that the study was in accordance with the standards approved by Janssen's theory. The study found that the structure of connections that can be used in the construction work was sleeves and inserts.

Structural Analysis of Folded Glass Plate Structures

Folded glass plate structures have the potential to become the next generation of structural glass. By connecting glass plates along their edges and creating a folded plate geometry, glass can be used to transparently self-span large areas without the need for additional supporting structure. An experimental glass connection is used as a basis for this paper. Available test and numerical data is used to create an interaction diagram for this connection, giving allowable axial forces, shear forces and bending moments. Due to the dependency of folded plate structures on geometry, a parametric numerical analysis approach is developed. This captures the global behaviour of the structures whilst also being calibrated against the local behaviour of the connection detail. The approach is based on established techniques for structural glass analysis using the finite element software Strand7. The results are presented graphically, illustrating that connection utilization drives design. It is shown that parametric finite element analysis is a powerful tool to extend feasibility-studies for new shapes and configurations.

658 配管フランジ締結部の漏れに対する許容曲げモーメントの算定

658 配管フランジ締結部の漏れに対する許容曲げモーメントの算定

내부충전 콘크리트와 횡보강 및 축방향 철근으로 보강된 PHC 말뚝의 휨강도

PHC 말뚝은 우수한 축하중 저항 능력에 비해 상대적으로 전단 및 휨 저항 성능이 낮은 단점을 가지고 있다. 이 연구의 목적은 기존 PHC 말뚝의 단점을 개선할 목적으로 개발된 중공부에 내부충전 콘크리트, 축방향 철근과 전단 철근으로 보강한 합성 PHC 말뚝(ICP 말뚝)의 휨성능을 평가하는 것이다. 이를 위하여 기존의 교대 설계사례로 부터 말뚝에 발생하는 축력과 휨모멘트를 조사한 후, ICP 말뚝 계산을 위하여 개발한 축력-휨모멘트 상관관계 프로그램을 이용하여 허용 축력과 휨모멘트가 발생하는 부재력을 만족하도록 ICP 말뚝을 설계하였다. 설계에 따라 ICP 말뚝을 제작하였으며, 휨실험을 수행하였다. 실험 결과 ICP 말뚝은 PHC 말뚝에 비하여 약 45% 큰 휨내력을 나타내었다. 또한 계산에 의해 예측한 ICP 말뚝 휨강도의 25%를 허용 휨모멘트로 취할 경우, 약 4.5의 안전율을 갖는 것으로 평가되었다.

국부 감육과 균열이 발생한 TP316 스테인리스강 배관의 파괴거동에 관한 실험적 연구

Although nuclear power plant piping system is designed conforming to design specifications, the piping systems are deteriorated with increase in service life. In this study, monotonic and cyclic loading tests were carried out on TP316 stainless steel pipe specimens, and the effect of local wall thinning and cracking on failure behavior was investigated. In the tests, 0%, 35% and 75% wall thinning and cracking of initial thickness were artificially introduced to inside elbow and straight pipe specimens, and internal pressures of 20MPa were applied to simulate real operation condition. From the test results, the effect of local wall thinning and cracking on failure mode, ultimate load, number of cycle and strain energy was presented, and maximum bending moment was compared with allowable bending moment calculated by ASME code.

Evaluation of critical stranding incidents

A method is introduced to quickly measure the total bending moment and shear force for any ship due to soft groundings. Therefore, the ship design program e4 and the FE program ANSYS are used and coupled. The grounding points or areas are combined with different load cases. These combinations are being considered for different water levels due to tide. The critical combinations that lead to an exceedance of the maximal allowable bending moment and shear force according to classification societies can be determined. The ship is modelled as a rigid body and the sliding phase is not considered. The presented method is verified through existing formulas. Also, the acting forces and moments as well as the sections at risk can be identified. The method is exemplary applied for a container vessel.

A study on the sealing performance of flange joints with gaskets under external bending using finite-element analysis

The effect of external bending on flange joints in pipelines, pressure vessels, and pressure vessel nozzles is significant and difficult to assess. In the current work, the sealing performance of a gasketed flange joint under external bending has been studied by using a three-dimensional finite element analysis, considering the non-linear material behaviour of the gaskets. Spiral wound gaskets and non-metallic gaskets with various sealing materials are considered. Results show that the allowable bending moment on a flange joint depends on the tightness required, type of gasket, and its deformation characteristics. Gaskets with elastomeric sealing materials show good performance against leakage under external bending.

Optimal design of a mono-symmetrical open cross section of a cold-formed beam with cosinusoidally corrugated flanges

The paper is devoted to a thin-walled beam with a flat web and cosinusoidally corrugated flanges. Considered beam has an open cross section and is mono-symmetric. Two different types of load are taken into account, i.e. pure bending and uniformly distributed load. The authors are searching for an optimal cross section shape of the beam. The beam cross section is characterized by dimensionless parameters, which are design variables. The dimensionless objective function is so defined as to comprise both a cross section area and a maximal allowable bending moment. The constraints follow from the local buckling condition for corrugated flange and geometric restrictions. The beams with different length to height ratio are analyzed. Results of the numerical calculations are presented graphically.

Optimization of open cross sections of thin‐walled beams with plate‐shell‐flanges

AbstractThe paper is devoted to a monosymetrical cold‐formed thin‐walled beam with open cross section. Its flange consists of plates and circular shells. The beam is under pure bending. The cross section is characterized by dimensionless parameters. The authors are searching for an optimal cross section shape of considered beam. This optimal shape is determined by means of parametric optimization. The dimensionless objective function is so defined as to comprise both cross section area and a maximal allowable bending moment. The constraints follow from the local buckling conditions and geometric restrictions. Moreover, there are optimized cross sections of beams, for which the shear center is located either in the web or in the centroid of the cross section. Results are compared and analyzed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Deformation of Windmill Support and Operation

The wind-induced deformation of windmill supports wind is analyzed. A monolithic hollow cylinder support is replaced and designed to endure wind velocity of 60m/s at rest and 20m/s in blade rotation. A windmill with fixed pitch blade angles and a permanent magnetic generator are controlled to meet both allowable bending moment and electric brake current. To operate the windmill efficiently for power generation, local wind characteristics must precisely determined, giving the critical cutoff parameter and magnitude of wind bursts at a certain average wind velocity.

Progressive Collapse Analysis of a Ship's Hull under Longitudinal Bending (2nd Report)

This paper describes the further improvement of the simplified method of progressive collapse analysis of a ship's hull under longitudinal bending proposed by the authors. Here, the method of analysis of flexural behaviour of stiffener elements was extended to deal with coupled flexural-torsional behaviour of angle bar stiffeners welded to continuous plating.A series of elastoplastic large deflection analysis was performed and the rationality of the proposed method was examined.With the improved computer code 'HULLST', two alternative analyses were performed on existing bulk carrier including and neglecting tripping of stiffener elements. It was found that the ultimate strength of stiffener elements decreases when stiffener tripping takes place, which results in reduction of ultimate bending moment of the cross-section. The load carrying capacity of stiffener elements in the post-ultimate strength range was more decreased and so that of the cross-section. The allowable bending moment according to the Lloyd's Register of Shipping was calculated and the reserve strength above it until the initial local collapse was 22.4% of the allowable bending moment. Interaction diagram for longitudinal hull strength under bi-axial bending is also presented.Progressive collapse analysis was performed also on a large scale frigate model tested by Dow, and the applicability of the present method was demonstrated.