Inelastic dynamic response of reinforced concrete infilled frames

An inelastic finite element model to simulate the behaviour of reinforced concrete frames infilled with masonry panels subjected to static load and earthquake excitation has been presented. Under the loads, the mortar may crack causing sliding and separation at the interface between the frame and the infill. Further, the infill may get cracked and/or crushed which changes its structural behaviour and may render the infill ineffective, leaving the bare frame to take all the load which may lead to the failure of the framing system itself. In this study, a mathematical model to incorporate this behaviour has been presented.     

Nonlinear analysis of reinforced concrete cylindrical shells

In this paper, analysis of reinforced concrete cylindrical shells is performed using a strain-based finite element. The shell element employed is bidimensional, cylindrical circular and has four-nodes and five nodal degrees of freedom. The nonlinearities due to concrete cracking and yielding of the steel are taken into account. The constitutive models for the materials employ the smeared cracking concept and a finite element layered approach. Concrete is modeled by a strain-induced orthotropic-elastic model under plane state of stress. A bilinear steel model is used and the stress/reversal with Baushinger effect is included. Examples show the good accuracy provided by this analysis.     

Nonlinear finite element analysis of reinforced concrete stiffened and cellular slabs

A novel approach is presented in this paper for linear and nonlinear finite element analysis of reinforced and prestressed concrete cellular slabs based on a slab-beam model. Mindlin/Timoshenko assumptions are adopted in the slab-beam model which thus allows for transverse shear deformations. Several examples are presented to illustrate the accuracy and limitations of the method.     

Numerical modeling of masonry-infilled RC frames subjected to seismic loads

The behavior of masonry-infilled reinforced concrete frames under cyclic lateral loading is complicated because a number of different failure mechanisms can be induced by the frame-infill interaction, including brittle shear failures of the concrete columns and damage of the infill walls. In this study, nonlinear finite element models have been used to simulate the behavior of these structures. Diffused cracking and crushing in concrete and masonry are described by a smeared-crack continuum model, while dominant cracks as well as masonry mortar joints are modeled with a cohesive crack interface model. The interface model adopts an elasto-plastic formulation to describe the mixed-mode fracture of concrete and masonry. The model accounts for cyclic crack opening and closing, reversible shear dilatation, and joint compaction due to damage. The constitutive models have been validated with experimental data and successfully applied to the dynamic analysis of a three-story, two-bay, masonry-infilled, non-ductile, reinforced concrete frame tested on a shake table. The results have demonstrated the capabilities of the finite element method in capturing the nonlinear cyclic load–displacement response and failure mechanisms of the structure, and indicated the important contribution of infill walls to the seismic resistance of a non-ductile reinforced concrete frame.     

Explicit finite element analysis of lightly reinforced masonry shear walls

Explicit finite element analysis (FEA) of masonry shear walls containing reinforcement at spacing between 800 mm and 2000 mm, referred to as wide spaced reinforced masonry (WSRM), are modelled using macroscopic material characteristics for the unreinforced masonry (URM) panels and damaged concrete plasticity for the grouted cores containing reinforcement. The material model and some basic principles of the explicit finite element algorithm are briefly discussed. It has been shown that by minimising the kinetic energy and using an appropriate time scaling and/or damping factor, the FEA could provide reasonable and efficient prediction of the behaviour of the WSRM and URM shear walls.     

A numerical model for the flexural analysis of short reinforced masonry columns including bond–slip

A numerical model for the flexural analysis of short reinforced masonry (RM) columns subjected to vertical and lateral loading is presented. A layered line element formulated for the analysis of reinforced concrete beam columns by the authors has been suitably modified for this purpose by incorporating the material nonlinearities associated with the RM. The modelling of the RM column accounts for the effect of the early cracking in the mortar joint and the bond–slip characteristics between the steel reinforcement and the masonry grout in addition to the material nonlinearity of the masonry and the steel. The model has been validated by comparing its prediction with the load–deflection response of four RM columns tested under varying levels of the axial load. The importance of including bond–slip characteristics in the modelling is demonstrated through the examples.     

Nonlinear finite element analysis of reinforced concrete plates and shells under monotonic loading

Plane stress constitutive models are proposed for the nonlinear finite element analysis of reinforced concrete structures under monotonic loading. An elastic strain hardening plastic stress-strain relationship with a nonassociated flow rule is used to model concrete in the compression dominating region and an elastic brittle fracture behavior is assumed for concrete in the tension dominating area. After cracking takes place, the smeared cracked approach together with the rotating crack concept is employed. The steel is modeled by an idealized bilinear curve identical in tension and compressions. Via a layered approach, these material models are further extended to model the flexural behavior of reinforced concrete plates and shells. These material models have been tested against experimental data and good agreement has been obtained.     

屋面预应力混凝土双T板端部腹板裂缝原因分析与加固处理

针对某单层工业厂房屋面预应力混凝土双T板端部开裂情况,利用有限元软件Abaqus进行计算分析,发现双T板支座端部存在构造不佳、易出现初始裂缝的问题,在施工过程中未按照构造要求施工、使用过程中温度变化等产生的不利效应对双T板受力影响不能忽略.针对双T板存在的问题提出处理措施,对已有开裂构件进行加固,处理效果良好.     

Finite element modelling of compartment masonry walls in fire

A finite element model called MasSET has been developed which is capable of predicting the structural behaviour of single leaf masonry walls subject to elevated temperatures. The analysis models a slice through the wall as a column strip in plane stress, and also includes material with geometric non-linearity. The model has been previously validated by comparison with experimental results [1] and is used in this paper to conduct a parametric study investigating the effects of slenderness ratio, load eccentricity and boundary conditions. The results of the investigation are presented by way of failure temperatures for each condition, and show conclusive findings to the effects of each parameter investigated.     

Flexural analysis of reinforced fibrous concrete members using the finite element method

A numerical procedure based on the finite element method is developed for the geometric and material nonlinear analysis of reinforced concrete members containing steel fibres and subjected to monotonic loads. The proposed procedure is capable of tracing the displacements, strains, stresses, crack propagation, and member end actions of these structures up to their ultimate load ranges. A frame element with a composite layer system is used to model the structure. An iterative scheme based on Newton-Raphson's method is employed for the nonlinear solution algorithm. The constitutive models of the nonlinear material behaviour are presented to take into account the nonlinear stress-strain relationships, cracking, crushing of concrete, debonding and pull-out of the steel fibres, and yielding of the reinforcement. The geometric nonlinearity due to the geometrical change of both the structure and its elements are also represented. The numerical solution of a number of reinforced fibrous concrete members are compared with published experimental test results and showed good agreement.     

Application of ADINA to nonlinear analysis of reinforced concrete shear walls with openings

This paper is concerned with application of ADINA to elasto-plastic analysis of the shear walls with openings. The authors analyzed the types of structures. One is the shear wall with many openings (the model of a secondary shield wall in nuclear power plant), on which scale model experiments were made. The other is the shear wall with openings in concrete rigid frame (the model of a shear wall in a building), on which parametric study was made.

In both cases, concrete is modeled using 8 nodes isoparametric 2 dimensional plane stress elements, reinforcing steels are modeled as truss elements. Concrete and elasto-plastic models are adopted for non-linear material model of concrete and reinforcing steel, respectively. The total numbers of nodes are 248–308, and that of 2D elements are 66–80.

Both analytical results are satisfactory from the view point of structural design. Close agreement to experimental results in the cracking load, crack extension, elasto-plastic stiffness and total strength was verified.     

Substructuring technique in nonlinear analysis of brick masonry subjected to concentrated load

A multi-level substructuring technique and a mesh grading scheme are used in the nonlinear finite element analysis of brick masonry subjected to in-plane concentrated loads. Masonry structures are ideally suited for solution using these techniques since masonry consists of a regular assemblage of bricks and joints in a repetitive pattern. Large wall panels can therefore be modelled without the need for excessive computer storage requirements. It is shown that the dual application of these techniques is highly efficient and leads to significant savings in costs. The possibility of modelling the elastic region of brick masonry as an isotropic continuum using similar techniques is also considered.     

Validation of analytical and continuum numerical methods for estimating the compressive strength of masonry

The advances in computational mechanics witnessed in the last decades have made available a large variety of numerical tools. Sophisticated non-linear models are now standard in several finite element based programs. This paper addresses the ability of continuum numerical methods, based on plasticity and cracking, as well as on analytical methods to provide reliable estimations of masonry compressive strength. In addition, a discussion on the load transfer between masonry components is presented and special attention is given to the numerical failure patterns. The results found overestimate the experimental strength and peak strain. Alternative modelling approaches that represent the micro-structure of masonry components are therefore needed.     

Time-dependent modelling of RC structures using the cracked membrane model and solidification theory

A non-linear finite element model is presented for the time-dependent analysis of reinforced concrete structures under service loads. For the analysis of members in plane stress, the model is based on the cracked membrane model using a rotating crack approach combined with solidification theory for modelling creep. The numerical results are compared with a variety of long-term laboratory measurements, including development of deflections and cracking with time in a reinforced concrete beam, time-dependent change in support reactions of a continuous beam subject to support settlement and creep buckling of columns. The numerical results are in good agreement with the test data.     

Finite element analysis of interlocking mortarless hollow block masonry prism

Interlocking mortarless masonry system has been developed as an alternative system for the conventional bonded masonry. This paper covers the analysis of interlocking mortarless hollow concrete block system subjected to axial compression loads using FEM. An incremental-iterative finite element code is written to analyze the masonry system till failure. The stress-strain relation obtained from test is employed and equivalent uniaxial strain concept is used to account for the material nonlinearity in the compression stress field. The developed program is also capable of simulating the nonlinear progressive contact behaviour (seating effect) of dry joint taking into account the block bed imperfection. The comparison shows a good agreement between the developed FE program and the experimental test results.     

Probabilistic buckling analysis of fiber metal laminates under shear loading condition

The design allowables for compressive and shear buckling of fiber metal laminate (FML) panels need to be developed for the certification of these materials. In this paper, the shear buckling behavior of the two FML panels, ARALL3-3/2 and GLARE3-2/1, is investigated using a probabilistic analysis method in order to predict the distributions of the buckling load. The scatter associated with the material properties and the randomness in the loading conditions are accounted for in the probabilistic analysis. The shear buckling load of the panel is taken as the response function of the material properties and the load parameter. The response surface methodology (RSM) is employed for the development of the response function based on limited finite element data. Three RSM design methods: full factorial design, CCD design and saturated D-optimum design, are applied to construct the response function following which the shear buckling load distributions of the two FML panels are predicted. The predicted results are verified using independently generated finite element data.     

Failure analysis of laminated composite cylindrical/spherical shell panels subjected to low-velocity impact

A 4-noded, 48 d.o.f. doubly curved quadrilateral shell finite element based on Kirchhoff–Love shell theory, is used in the nonlinear finite element analysis to predict the damage of laminated composite cylindrical/spherical shell panels subjected to low-velocity impact. The large displacement stiffness matrix is formed using Green's strain tensor based on total Lagrangian approach. An incremental/iterative scheme is used for solving resulting nonlinear algebraic equations by Newton–Raphson method. The damage analysis is performed by applying Tsai–Wu quadratic failure criterion at all Gauss points and the mode of failure is identified using maximum stress criteria. The modes of failure considered are fiber breakage and matrix cracking. The progressive failure analysis is carried out by degrading the stiffness of the material suitably at all failed Gauss points. The load due to low-velocity impact is treated as an equivalent quasi-static load and Hertzian law of contact is used for finding the maximum contact force. After evaluating the nonlinear finite element analysis thoroughly for typical problems, damage analysis was carried out for cross-ply and quasi-isotropic cylindrical/spherical shell panels.     

A layered cylindrical quadrilateral shell element for nonlinear analysis of RC plate structures

This paper proposes a simple and accurate 4-node, 24-DOF layered quadrilateral flat plate/shell element, and an efficient nonlinear finite element analysis procedure, for the geometric and material nonlinear analysis of reinforced concrete cylindrical shell and slab structures. The model combines a 4-node quadrilateral membrane element with drilling or rotational degrees of freedom, and a refined nonconforming 4-node 12-DOF quadrilateral plate bending element RPQ4, so that displacement compatibility along the interelement boundary is satisfied in an average sense. The element modelling consists of a layered system of fully bonded concrete and equivalent smeared steel reinforcement layers, and coupled membrane and bending effects are included. The modelling accounts for geometric nonlinearity with large displacements (but moderate rotations) as well as short-term material nonlinearity that incorporates tension, cracking and tension stiffening of the concrete, biaxial compression and compression yielding of the concrete and yielding of the steel. An updated Lagrangian approach is employed to solve the nonlinear finite element stiffness equations. Numerical examples of two reinforced concrete slabs and of a shallow reinforced concrete arch are presented to demonstrate the accuracy and scope of the layered element formulation.     

Nonlinear analysis of reinforced concrete hyperboloid cooling towers—I. Material model, finite element model and validation

This is the first part of a two-part series of papers in which the constitutive material modelling of reinforced concrete, in shell structures, which resist applied loads predominantly through membrane action, is presented. The material model includes the effects of tensile cracking, tension stiffening, compression softening, interface shear transfer, and change in material stiffness due to crack rotation. A four-noded isoparametric curved shell element has been used in the nonlinear finite element analysis. The results obtained by using the model for analysis of a shear wall panel subjected to in-plane loading have been compared with those from experimental investigation.