Prediction Of Collapse Load Research Articles

Approximate limit analysis of full scale FRP-reinforced masonry buildings through a 3D homogenized FE package

Abstract A 3D homogenized FE limit analysis software for the numerical prediction of collapse loads and failure mechanisms of entire masonry buildings reinforced with FRP strips is presented. In particular, a two steps approach is adopted: in step I, masonry homogenized failure surfaces are obtained through an admissible kinematic FE approach in the representative element of volume (REV), constituted by a brick interconnected with its six neighbors with finite thickness mortar joints. 8-Noded rigid infinitely resistant parallelepiped elements interconnected with interfaces with frictional behavior and limited tensile and compressive strength are utilized to model the REV. A simple linear programming problem in few variables is obtained, suitable to recover numerically masonry failure surfaces when loaded in- and out-of-plane. In step II, homogenized failure surfaces are implemented in the novel FE kinematic limit analysis software for an inexpensive evaluation of collapse loads of entire buildings. Delamination is considered in the model imposing to FRP–masonry interfaces a limited resistance in agreement with Italian code CNR-DT-200. 6-Noded rigid infinitely resistant 3D wedge-shaped elements are used to model homogenized masonry, whereas FRP strips are modeled by means of triangular 3-noded rigid elements. A two story masonry building reinforced in various ways with FRP strips and experimentally tested at Georgia Tech under quasi-static horizontal loads is analyzed to assess numerical results. Good agreement is found both in presence and absence of reinforcement, meaning that the procedure proposed may be used by practitioners for a reliable evaluation of collapse loads and failure mechanisms of complex 3D strengthened masonry structures.

FE homogenized limit analysis model for masonry strengthened by near surface bed joint FRP bars

A homogenized limit analysis model for the prediction of collapse loads and failure mechanisms of masonry walls reinforced with near surface bed joint GFRP bars is presented. Reinforced masonry homogenized failure surfaces are obtained by means of a compatible identification procedure, where each brick is supposed interacting with its six neighbors by means of finite thickness mortar joints, filler epoxy resin and FRP rods. In the framework of the kinematic theorem of limit analysis, a simple constrained minimization problem is obtained on the unit cell, suitable to estimate – with a very limited computational effort – reinforced masonry homogenized failure surfaces. A FE strategy is adopted to solve the homogenization problem at a cell level, modeling joints, bricks, filler and FRP rods by means of eight-noded infinitely resistant parallelepiped elements. A possible jump of velocities is assumed at the interfaces between contiguous elements, where plastic dissipation occurs. For mortar and bricks interfaces, a frictional behavior with possible limited tensile and compressive strength is assumed, whereas for epoxy resin and FRP bars some formulas available in the literature are adopted in order to take into account in an approximate but effective way, the delamination of the bar from the epoxy and the failure of the filler at the interface with the joint. In order to validate the model proposed, two meaningful examples are critically analyzed. The first relies on a reinforced masonry beam in four-point bending, whereas the second is a full scale wall constrained at three edges and loaded until failure with a distributed out-of-plane pressure. While the first example is useful to test the model at a cell level, since only horizontal ultimate bending moment is involved in the failure mechanism, the second provides a full assessment of the procedure proposed at a structural level. In both cases, very good agreement is found with literature data, meaning that the model proposed may provide useful information for all practitioners interested in the design of masonry walls reinforced with bed joint FRP bars.

705 フロントサイドメンバの崩壊荷重の予測(GS.S 構造解析)

705 フロントサイドメンバの崩壊荷重の予測(GS.S 構造解析)

A Simple Mechanism Solution for Predicting the Collapse Loads of I-Beams Subjected to Concentrated Load

In order to solve the problem of web buckling for hot rolled I-beams without membrane subjected to concentrated load, a plastic mechanism analysis that involves consideration of the plastic hinges developing in the flanges and the yield lines forming in the web plate have been made, and a simple theoretical prediction of collapse loads have been developed. At the same time, wide ranges of finite element studies have been made. Based on the finite element results, certain approximations and empirical modifications are introduced because of the complex geometrical nature of the problem and the purpose to make the resulting design method simple enough for routine practical application. The theoretical results have been compared, and show close correlation, with the finite element results.

Collapse Loads for a Cylinder Embedded in Trench in Cohesive Soil

This study investigates the relationship between the sediment resisting force and embedment depth for horizontal cylinders in a vertical trench. Plane-strain calculations of collapse loads are performed for a series of trench depths. Collapse load predictions are based on finite element predictions validated by upper and lower bound solutions from classical plasticity theory. This study extends work by previous investigators by considering variable soil shear strength profiles and embedment depths exceeding one cylinder radius. Curve fits are applied to the finite element predictions to develop simplified equations relating collapse load to trench depth. The predictions are relevant to a number of applications, including pipeline penetration, waste disposal, and mine detection.

Non-linear Finite Element Analysis of Masonry Arches for Prediction of Collapse Load

The paper presents a summary of experimental and theoretical investigations on the load carrying capacity of masonry arch bridges. The experimental program includes static testing of two arches constructed in the heavy testing laboratory. Tests were also conducted on control specimens to investigate the properties of the masonry employed in the construction of the arches. The details of the two-dimensional non-linear finite element computer program developed for the analysis and load prediction of the masonry arch bridges are given. The program takes into account the non-linearity due to the non-linear stress-strain relationship and the cracking of the masonry. The load test results of the arches are compared with the results of a finite element analysis.

Monte Carlo simulation for arch bridge assessment

A Monte Carlo simulation is integrated with the mechanism method to perform risk analysis based masonry arch bridge assessment. A parametric study was carried out involving: live load dispersal angle; material bulk unit weights; backfill lateral pressure mobilisation; angle of shearing resistance; and Boussinesq's limiting live load influence value. These parameters had the biggest effect on collapse load predictions. The arch span was not considered here as a random variable because it is accurately measurable. This integrated Monte Carlo simulation is offered alongside routine assessment methods. Its principal benefit lies in its efficacy as a risk assessment tool whose users would primarily be interested in the probability of collapse under certain conditions.

Efficient Tubesheet Design Using Repeated Elastic Limit Analysis Technique

Conventional analysis of tubesheets in nuclear steam generators involves elastic analysis of a solid plate with equivalent properties. It has recently been recognized that alternate design techniques such as inelastic finite element analysis would lead to substantial cost reductions in material and manufacturing. Due to the anisotropy, arriving at yield criteria for an equivalent solid tubesheet is more complicated than for an isotropic solid. In addition, applying plastic finite element analysis in design is significantly more complex and time-consuming than elastic analysis. This paper proposes a relatively simple method to perform tubesheet collapse analysis. An anisotropic yield criterion is applied in conjunction with the classical lower-bound theorem of limit analysis and repeated elastic analyses involving elastic modulus modification. Two yield criteria are examined, namely Hill’s yield criterion and a recently suggested compressible fourth-order yield function. The collapse load predictions of the lower-bound equivalent solid methods are compared with the elastic-plastic finite element collapse load of the equivalent solid and of the actual perforated tubesheet.

Computation of bearing capacity factors using finite elements

The Paper shows how finite elements, in conjunction with elasto-plastic theory, can give excellent collapse load predictions for footings resting on c-φ soils. The problem is approached by considering each of the three components of bearing capacity appearing in Terzaghi's classical equation. The results show that the contributions to bearing capacity of the Nc and Nq terms can be computed with confidence and economy. The NT term, which is theoretically less sound than the other two, is also computed to be in close agreement with published approximate solutions but takes more computing effort. This is shown to be particularly so when the soil friction angle is increased. The superposition assumption in Terzaghi's equation is assessed using finite elements. The conservative nature of the equation is confirmed, with the inherent error shown to occur solely because of non-linearities in the Nγ term. It is thought that the techniques used in obtaining the results given may be applied with confidence to a wide range of soil collapse problems for which no known solutions exist. Le présent article décrit la manière dont des éléments finis. associès à la théorie élastoplastique, permettent d'obtenir d'excellentes prévisions des charges de rupture dans le cas de semelles reposant sur des sols c-φ. Pour résoudre le problème, on considère chacune des trois termes de la capacité portante telles qu'ils figurent dans l'equation classique de Terzaghi. Les résultats montrent que l'on peut calculer de manière sûre et simple la contribution des termes Nc et Nq à la capacité portante. Le terme Nγ qui est théoriquement moins précis que les deux autres termes, semble, d'après les calculs, concorder étrottement avec les solutions approximatives publiées mats qui exigent des calculs plus complexes, notamment lorsque l'angle de frottement interne du sol s'accroit. L'hypothèse de superpositton dans l'equation de Terzaghi est contrôlée à l'aide d'élements finis. Le caractère conservatif de l'equation se trouve confirmé et l'on constate que l'erreur inhérente ne se produit qu'en raison de la non-linéarité du terme Nγ. Les auteurs estiment que les techniques utilisées pour l'obtention des résultats indiqués peuvent être appliquées en toute confiance à un grand éventail de problémes relatifs à la rupture du sol pour lesquels aucune solution connue n'existe.

Numerical prediction of collapse loads using finite element methods : Sloan, S W; Randolph, M F Int J Num Anal Meth Geomech, V6, N1, Jan–March 1982, P47–76

Numerical prediction of collapse loads using finite element methods : Sloan, S W; Randolph, M F Int J Num Anal Meth Geomech, V6, N1, Jan–March 1982, P47–76

The load-carrying capacity of initially imperfect eccentrically loaded plates

Theoretical analyses of compressed plates with various loading and boundary conditions previously published by the authors are extended to include the effects of initial imperfections. Comparison of the theoretical results is made with experiment. It is shown that for plates with supports on both unloaded edges the simple criterion that collapse occurs when the maximum membrane stress reaches yield, gives accurate estimates of failure for eccentrically loaded plates. The collapse modes of plates which have one edge free are found to be rather complex in nature and vary with plate thickness and loading eccentricity. A simplified design analysis for the prediction of collapse loads of eccentrically loaded simply supported plates is formulated and shown to predict experimental results very accurately.