Masonry Macro-block Analysis

This research investigates numerically the potential failure of different framed structures after removal of a corner column. This study is directed towards the role of the joint above the removed column in terms of framed structures stability and internal forces redistribution utilizing linear static, nonlinear static and nonlinear dynamic analysis procedures. First, the preliminary linear static analysis as a part of more detailed nonlinear static and dynamic analysis to model reinforced concrete frames is performed. For nonlinear numerical models, three different moment-rotation capacity curves are considered for the joint above the removed column. These curves are taken according to FEMA 356 regulation according to the reinforcement condition at the joint location to represent normal joint, anchorage deficient joint and shear deficient joint. In linear static models, the results confirmed that, the more moment the joint can resist at the removed column location, the less moment is generated at the beam’s other end. In nonlinear static analysis, the model with normal plastic hinge properties recorded a higher carrying capacity than the model with both shear and anchorage plastic hinges. Nonlinear dynamic analysis with less assumptions offer the more representative modeling for the considered case study which is obvious from its closer perdition of internal forces and deflection compared to the reference findings.

The Special Issue of The Open Civil Engineering Journal entitled “New trends in the numerical analysis of masonry structures” provides an insight into the most up-to-date nu-merical techniques used at academic and professional level to perform advanced structuralanalyses on masonry struc-tures. Masonry is a building material that has been used for more than ten thousand years. In many countries, masonry structures still amount to 30–50%of the new housing devel-opments. Also, most structures built before the 19th century and still surviving are built with masonry. Masonry is usu-ally described as a heterogeneous material formed by units and joints, with or without mortar, and different bond ar-rangements. Units are such as bricks, blocks, ashlars, adobes, irregular stones and others. Mortar can be clay, bitumen, chalk, lime/cement based mortar, glue or other. The almost infinite possible combinations generated by the geometry, nature and arrangement of units as well as the characteristics of mortars raise doubts about the accuracy of the term “ma-sonry”. Still, much information can be gained from the study of regular masonry structures, in which a periodic repetition of the microstructure occurs due to a constant arrangement of the units (or constant bond). The difficulties in performing advanced testing and pro-viding sufficiently general numerical models for this kind of structures are basically due to the innumerable variations of masonry typologies, the large scatter of in situ material prop-erties and the impossibility of reproducing all in a specimen. Therefore, most of the advanced numerical research carried out in the last decades concentrated in brick / block masonry and its relevance for design. Accurate modelling requires a comprehensive experimental description of the material, which seems mostly available at the present state of knowl-edge. From a numerical point of view, masonry behaviour is quite complex to model, exhibiting non-linearity very early during the loading process, with softening in both tension and compression, low ductility and differed deformations under sustained loads. In addition, masonry is the result of the assemblage of bricks or stones, where mortar is laid, with common geometric irregularities adding further complexity to the problem. The special issue collects ninepapers from experts in the field, including contributions of researchers from six differ-ent countries (Czech Republic, Iran, Italy, Portugal, Spain, Switzerland), either devoted to the utilization of non-standard numerical models for case-studies or presenting new approaches for the interpretation of masonry behaviour in presence of different kinds ofnon-linearity. The effort is always to put the knowledge beyond the existing state-of-the art. Karbassi and Lestuzzi [1]present a fragility analysis per-formed on unreinforced masonry buildings, conducted by means of the so called Applied Element Method (AEM), to define fragility curves of typical masonry buildings which may be regarded as representative of building classes. A se-ries of nonlinear dynamic analyses using AEM are per-formed for a 6-storey stone masonry and a 4-storey brick masonry building using more than 50 ground motion re-cords. The distribution of the structural responses and inter-storey drifts are finally used to develop spectral-based fragil-ity curves for the five European Macro-seismic Scale dam-age grades. In the second paper, Milani et al. [2]perform a detailed non-linear analysis (both pushover and limit analysis) on the San Pietro di Coppito bell tower in L’Aquila, Italy, trying to have an insight into the causes of the collapse occurred dur-ing the devastating 2009 earthquake. Sykora et al. [2]review several topics related to the ho-mogenization of transport processes occurring in historical masonry structures. Particular attention is paid to variations of temperature and moisture fields, whose contribution to structural damage usually far exceeds the effects of me-chanical loadings. The concept of Statistically Equivalent Periodic Unit Cell (SEPUC) is reviewed and utilized to deal with historic masonry and random patterns. Accepting SEPUC as a reliable representative volume element, a Fast Fourier Transform to both the SEPUC and large binary sam-ples of real masonry is used to tackle effective thermal con-ductivities problems. Fully coupled non-stationary heat and moisture transport problems are addressed next in the framework of a two-scale first-order homogenization, with emphases on the application of boundary and initial condi-tions at the meso-scale.

Importance of ‘DAF’ in evaluating structural adequacy of gravity-load designed RC buildings

This study is the compared seismic performance that are difference between the performance of structures on various site classes and beam-column connection. this analysis model was designed the previous earthquake load. To compare the performance levels of the structure was subjected to nonlinear static and nonlinear dynamic analysis. Nonlinear analysis was used to The Perform 3D program. Nonlinear static analysis was compared with the performance point and Nonlinear dynamic analysis was compared the drift ratio(%). Analysis results, the soft site class of the displacement was more increase than rock site classes of the displacement. Also The smaller the displacement was increased beam-column connection stiffness.

In this paper, a simplified analysis procedure to calculate the column removed point displacement at progressive collapse analysis of reinforced concrete structures is proposed. The energy absorption capacity under the column missing event is used for formulations. The approximate method is simple to utilize, user friendly, yet accurate. For progressive collapse analysis of structures, linear static analysis, nonlinear static analysis, linear dynamic analysis and nonlinear dynamic analysis can be performed. In this paper, the nonlinear static analysis from alternate load path method is used and the reason of initial local collapse has not been considered. In fact, an energy-based method by using load-displacement curve of RC frame and considering the effect of floor slab for the progressive collapse analysis is considered. The accuracy of the proposed method is demonstrated by comparing the results to three experimental and analytical results. Finally, the effects of the spans length, sections dimensions, material properties and the beams reinforcements of column removed spans on substructure behavior is studied, as well.

Investigation of progressive collapse resistance and inelastic response for an earthquake-resistant RC building subjected to column failure

Recent research trends have indicated an interest in High-Altitude, Long-Endurance (HALE) aircraft as a low-cost alternative to certain space missions. These missions require a lightweight vehicle operating at low speeds, high lift and minimum drag. These conditions necessitate high-aspect ratio wings. Due to its large span and light weight, the wing structure is very flexible. The wings undergo significant deflections as a result of the fluid loads acting on them, and require the consideration of aeroelastic effects. To reduce the structural deformation and increase the total lift, a sensorcraft model with a joined-wing configuration is employed. The results of the simulation of the complex, three-dimensional flow past the joined wing of a HALE aircraft are used as an input for the structural analysis. In the existing studies to date, only simplified structural models have been examined. In the present work, a semi-monocoque structural model is developed. All stringers, skin panels, ribs and spars are represented by appropriate elements in a finite-element model. Linear and nonlinear static analyses under the aerodynamic load are performed. The stress distribution in the wing is explored. Starting with a structural model with uniform mass distribution, a design optimization is performed. The optimized model has a maximum stress 42% lower and a maximum deflection 26% lower than obtained for the initial model. Linear and nonlinear buckling analyses are performed as well. The nonlinear analysis yields a critical buckling load 18% lower than that predicted by linear analysis. This paper will discuss the details of the structural modeling as well as the results obtained before and after optimizing the model.

Purpose nonlinear dynamic analysis of triangular and quadrilateral membrane elements with in-plane drilling rotational degree of freedom. Design/methodology/approach The nonlinear analysis is carried out using the updated co-rotational Lagrangian description. In this purpose, in-plane co-rotational formulation that considers the in-plane drilling rotation is developed and presented for triangular and quadrilateral elements, and a tangent stiffness matrix is derived. Furthermore, a simple and effective in-plane mass matrix that takes into account the in-plane rotational inertia, which permit true representation of in-plane vibrational modes is adopted for dynamic analysis, which is carried out using the Newmark direct time integration method. Findings The proposed numerical tests show that the presented elements exhibit very good performances and could return true in-plane rotational vibrational modes. Also, when using a well-chosen co-rotational formulation these elements shows good results for nonlinear static and dynamic analysis. Originality/value Publications that describe geometrical nonlinearity of the in-plane behaviour of membrane element with rotational d.o.f are few, and often they are based on the total Lagrangian formulation or on the rate form. Also these elements, at the author knowledge, have not been extended to the nonlinear dynamic analysis. Thus, an appropriate extension of triangular and quadrilateral membrane elements with drilling rotation to nonlinear dynamic analysis is required.

This paper presents a comparative review of three major seismic analysis methods used for reinforced concrete (RC) structures: linear static analysis, nonlinear static (pushover) analysis, and nonlinear time-history analysis. The study evaluates their underlying theory, modelling requirements, assumptions, accuracy, and level of computational effort. Published global and regional research was reviewed to assess when each method is appropriate for performance evaluation and design. The findings show that linear static analysis is simple and code-friendly but often unreliable for irregular, taller, or higher–mode-sensitive buildings. Nonlinear static analysis better represents inelastic behaviour, stiffness degradation, and hinge formation but may overlook torsional and higher-mode effects. Nonlinear time-history analysis offers the most realistic predictions of seismic response; however, it requires significant modelling detail, computational resources, and careful selection of earthquake records. This review highlights conditions where simplified methods are acceptable and where nonlinear approaches are necessary for accurate and safe seismic assessment and retrofit decisions.

Comparison of near and far-fault ground motion effects on low and mid-rise masonry buildings

Effect on non-linear soil-structure interaction due to base slab uplift on the seismic response of a high-temperature gas-cooled reactor (HTGR)

The ground motion vertical component is typically ignored in the analysis of ordinary building structures, even though damage observed in recent Emilia (Italy) earthquakes indicate that the vertical accelerations may have influenced the response of older masonry buildings. This manuscript presents a numerical study that investigates the effects of the ground motion vertical component on a reference unreinforced masonry building. These effects are evaluated considering the in-plane wall behaviour due to different input ground motions and different mechanical properties for the masonry walls. Nonlinear dynamic analyses with natural ground motion records selected based on source-to-site distance, fault rupture type, ground category and moment magnitude were carried out. First, the velocity spectrum intensity (VSI) of all records was studied to identify records with strong vertical components. Second, nonlinear history analyses were carried out and selected engineering demand parameters (EDPs: horizontal and vertical displacements, axial and shear forces) were checked. The results show the clear correlation between the vertical VSI and the EDPs and the incidence of the source-to-site distance on the vertical component effects. For records characterized by low source-to-site distances and high moment magnitudes, the vertical component can generate tensile forces in the masonry piers, especially where the gravity loads are small. In these cases, fluctuations in the axial load strongly affect the flexural and shear capacity of the piers. Finally, the analysis of the Eurocode 8 provisions indicates that the absence of clear guidelines on the use of the vertical seismic component can be strongly non-conservative for masonry structures.

Experimental tests performed on scaled masonry buildings provide key information to improve the knowledge under seismic actions. Masonry buildings behavior is strongly influenced by their physical and mechanical parameters under dynamic actions. In fact, the actual structural behavior is very complex to predict due to the significant variability of the input parameters and the strong heterogeneity of masonry. Furthermore, the behavior of masonry buildings is often influenced by the interaction with adjacent building units. In this context, the SERA AIMS project aims to improve knowledge on the interaction between adjacent buildings. In order to assess the seismic capacity of masonry structures and their damage evolution, nonlinear models often require a numerical calibration of nonlinear parameters. Simplified Finite Element (FE) models, with some very simple assumptions, can be more suitable for complex problems like as the interaction between adjacent building aggregates. The low initial knowledge level in the SERA AIMS blind competition favored simple assumptions. The availability of simple models allowed to perform consecutive time histories including the cumulative effects of previous signals. In fact, the tested prototype was subjected to many replicas. The masonry structure and the crucial interfaces between the units have been modelled by means of nonlinear elements according to the reduced knowledge level at the blind prediction stage. The main goal was to estimate the key information of a masonry building under seismic action like as: triggering and the type of damage at the most stressed areas and therefore the load threshold at which evident damage is expected. Global FE model provides information on the global behaviour (in plane behaviour), while, according to the failure models typically found in masonry buildings, kinematic analyses have been performed to assess the out of plane (local) behaviour, too. The numerical results obtained by the preliminary analysis have been compared with the experimentally detected damages. The simplified approach, based on limited information without calibration, discussed in this paper, represents a useful support tool to design dynamic tests on full-scale or scaled masonry buildings, but also to assess the vulnerability of real masonry structures.

Current codes and guidelines provide different methods to perform nonlinear static analysis of structures that require some non-intuitive assumptions in their application. In the present paper an energy-based method for nonlinear static analysis that allows to overcome these assumptions is proposed. In the method the capacity and the demand are both expressed in terms of energy. An energy capacity curve is computed considering that at each step the work of the lateral forces is equal to the structure internal work. The demand is represented in terms of an energy quantity, defined pseudo-energy, that is computed from both the maximum response displacement and the maximum response force. Constant ductility pseudo-energy spectra are introduced as energy demand design spectra, alternative to the input energy demand spectra. The definition of the performance point does not require iterative procedures for equating the internal dissipated energy to the demand energy. For the direct evaluation of the performance point two different operative procedures are proposed. The proposed method is evaluated comparing the earthquake-induced deformations of single degree-of-freedom systems resulting from the application of the presented nonlinear static analysis procedures with those obtained from the time-history analysis and from the application of the EC8 nonlinear static analysis procedure. The method is also applied in the case of a RC plane frame representing the inner frame of a six story building. The results obtained with the proposed method are in good agreement with those computed using nonlinear dynamic analyses, moreover they are characterized by a better accuracy with respect to the results obtained with the method provided by EC8.

Efficient meta-heuristic mesh adaptation strategies for NURBS upper–bound limit analysis of curved three-dimensional masonry structures