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This study is a comparison of wind and seismic loads on medium and high-rise buildings in Muscat, Oman. It uses the proposed Omani Seismic Code and Eurocode EN1991 for seismic and wind calculations, respectively. Muscat falls under Zone-1 in the Omani seismic code and experience basic wind speed of 30 m/sec. The research investigates buildings with varying aspect ratios (1:1 and 1:2), heights (11, 15, and 19 stories), and structural layouts (frame only, core shear wall, and corner shear wall), using ETABS for structural analysis. The findings reveal that seismic actions are generally more significant than wind actions for buildings in Muscat. In frame-only structures, wind-induced base shear ranges from 16%-33% for 1:1 aspect ratio and 21%-43% in the x-direction and 10%-20% in the y-direction for 1:2 aspect ratio, when compared to seismic actions. This difference decreases with increasing building height. Incorporating shear walls notably reduces the maximum lateral displacement across all scenarios, with core-located walls being most effective, leading to a 49% reduction in lateral displacement. Shear walls also substantially mitigate first-story column shear forces and bending moments. The study concludes that seismic actions are more critical than wind actions in Muscat for simple moment-resisting frame systems. Additionally, using shear walls in these buildings is highly beneficial for controlling lateral displacements and reducing member forces. [ABSTRACT FROM AUTHOR]

DynABlock_2D is a standalone MATLAB® application for rocking dynamics, nonlinear static and limit analysis of masonry block structures under seismic actions and support movements. The software was designed in order to provide an integrated tool for the different types of analysis recommended in technical standards and commentaries on the assessment of failure mechanisms in historic masonry structures. The objective of this paper is to describe the architecture, the main functionalities and the general form of the optimization-based formulations implemented in the code for the different types of analysis. Masonry is represented as an assemblage of rigid blocks interacting at no-tension frictional contact interfaces, with elastic or rigid behavior. A simple .xls file is used for the input of mechanical parameters and loading conditions related to the analysis types. CAD .dxf files are used for the generation of geometric models. Efficient solvers available in the literature are used for the optimization problems, involving short CPU times to obtain a solution. Examples of applications to arches and arch on buttresses are presented to illustrate the capabilities and computational efficiency of the developed software.

Recent studies indicate that the structural collapse probability of large-scale seismically isolated structures under seismic actions and the effect of vertical seismic effects are usually neglected in structural analysis. The differences in the seismic design codes in different countries also lead to a challenge in assessing the structural efficiency. A numerical model is developed in this paper for investigating the behavior of an elevated large-scale transportation hub with series seismic isolation systems (SIS). The 3D finite element model considers concrete and steel stiffness degradation under reciprocating seismic actions, geometric nonlinearity and both horizonal and vertical seismic actions, which aims to provide a reliable and simplified tool to describe the seismic performance of seismically isolated structures designed by the minimum criteria of GB 50011–2010 and ASCE/SEI 7–16. Nonlinear time history analysis of six seismic waves under MCER and extremely rare strong earthquakes is carried out to study the base shear, drifts of columns and isolation bearings, structural failure, energy dissipation and vertical load effects. The results show that the structure designed according to ASCE/SEI 7 has better performance when the seismically isolated structure subjected to MCER due to additional reinforcements. When the structure is subjected to extremely rare strong earthquakes, structures designed according to GB50011 shows a higher probability of structural collapse.

Reinforced concrete water storage tanks are civil engineering structures subject to very aggressive atmospheric conditions that expose them to harmful corrosion risk. This dangerous phenomenon caused by the penetration of chloride ions causes pitting corrosion and leads to the reduction of the section of the reinforcements and consequently to the loss of strength and the structure performance. In this study, we are interested in analyzing the performance of an elevated storage tank, taking into account the corrosion of the reinforcements subjected to tensile stress, by considering environments with different rates of aggressiveness. A method based on Housner's model is used to evaluate the tension stresses in the reinforced concrete (RC) pedestal (supporting system) of the tank, subjected to the seismic actions. A pitting corrosion model is developed in order to determine the evolution in time of the reinforcements section in different environments. Several parameters influencing corrosion are taken into account, such as concrete cover and the concentration of chlorides ions.

Base isolation is a widely-used method used to minimise the harmful effects of earthquakes on buildings. Unlike a fixed base building, a building with a base isolation system essentially decouples the superstructure from the substructure resting on the ground. Then, during earthquakes, the superstructure’s relative displacement is significantly reduced, minimising the structural damage. Auxetics, which are materials with a negative Poisson’s ratio, are known for possessing properties such as high energy absorption. Based on the energy absorbing capabilities of auxetic materials, it is proposed that incorporating them into base isolation structures would positively impact on the performance of the system. Therefore, the article aims to investigate the response of structures under seismic loading incorporating re-entrant hexagon layers into the base isolation system. This is assessed by defining and numerically testing the system using finite element analysis. The models developed for this study represent multi-storey structural steel frames combined with fixed base, conventional lead-rubber bearing and auxetic composite base isolation. Differences in the response obtained from the mentioned systems are highlighted. Results indicate that the auxetic base isolation may improve the dynamic response of structures, although a unique performance is not recorded.

In Europe, the qualification of injection anchors in masonry under static and quasi-static actions is based on an assessment of tests performed in undamaged masonry. Nevertheless, in seismic prone countries like Italy the influences deriving from earthquake actions cannot be disregarded. Masonry elements are very sensitive to cyclic/seismic action and research on the behavior of anchors in damaged masonry is rather limited. The paper presents the results of an experimental campaign aimed at evaluating the residual tensile strength of adhesive anchors installed into undamaged walls that were subsequently subjected to cyclic in-plane loading to simulate seismic actions before. Consequently, the anchors experienced different stresses depending on their location within the walls. Overall, 29 tests were performed with anchors placed both, in undamaged and damaged areas. The results showed that there is a correlation between residual tensile strength and masonry initial conditions, and therefore the installation of anchors in masonry elements should be carefully planned avoiding areas that could be heavily damaged during seismic events or considering redundant connections in critical areas. In particular, it seems that the width of the crack (created by cyclic actions) that passes nearby/into the anchor borehole is the main parameter that affects the ultimate resistance of the anchors. [ABSTRACT FROM AUTHOR]

Seismic verification of masonry buildings based on realistic calculation models and increased behavior factors With the application of the traditional linear verification concept to masonry structures it is already no longer possible to carry out structural safety verifications even for buildings with standard ground plan configurations in areas with moderate seismicity. This problem will be exacerbated in Germany with the introduction of continuous probabilistic earthquake maps. Due to the increased seismic actions, it is necessary to make the existing load‐bearing capacity reserves that have not yet been taken into account available in comprehensible verification concepts in construction practice. This article presents a concept for the building‐specific determination of increased behavior factors. The behavior factors are composed of three components, which take into account the load redistribution in ground plans, the deformation capability and energy dissipation and all kinds of overstrength effects. For the calculation of these three components, a non‐linear verification concept based on pushover analyses is applied, in which the interactions of walls and floor slabs are described by a level of restraint. A non‐linear modeling approach of the overall building is introduced for the determination of the restraint levels, with which the interaction of walls and floor slabs can be simulated. The results of the linear verifications with increased behavior factors for this building are significantly closer to the results of non‐linear verifications and thus the standard ground plan configurations in areas with moderate seismicity can still be verified with the traditional linear calculation approaches. [ABSTRACT FROM AUTHOR]

This paper is a diagnostic study and it is the 3 rd in a series of scientific articles which investigate the environmental factors that affect the archaeological buildings all over the country (Egypt). It explores the Nektenebo II temple in Bahbit El-Hagar, which is one of the most significant archeological sites in Pharaonic Egypt. It is particularly selected to assess and evaluate the deterioration conditions, which affect its components. The temple has an aggressive harmful deteriorated appearance because of severe seismic actions, especially earthquakes and unstable lands. Thus, the site is investigated via close inspection and a complimentary survey (CICS) to check the decay conditions that resulted from the severe effects of seismic actions. Moreover, it investigates some samples collected from the aforementioned monumental site using certain techniques, such as PM, SEM-EDX and XRD, in addition to define the effective physio-mechanical properties to identify the deterioration products caused by secondary environmental factors. The results asserted that the deteriorated appearances that dominate the study area are mechanical destruction (cracks and micro fissures) as well as other deterioration symptoms, such as salt crystallization, soiling and crusting, as well as crumbling and scaling [ABSTRACT FROM AUTHOR]

Reinforced concrete water storage tanks are civil engineering structures subject to very aggressive atmospheric conditions that expose them to harmful corrosion risk. This dangerous phenomenon caused by the penetration of chloride ions causes pitting corrosion and leads to the reduction of the section of the reinforcements and consequently to the loss of strength and the structure performance. In this study, we are interested in analyzing the performance of an elevated storage tank, taking into account the corrosion of the reinforcements subjected to tensile stress, by considering environments with different rates of aggressiveness. A method based on Housner's model is used to evaluate the tension stresses in the reinforced concrete (RC) pedestal (supporting system) of the tank, subjected to the seismic actions. A pitting corrosion model is developed in order to determine the evolution in time of the reinforcements section in different environments. Several parameters influencing corrosion are taken into account, such as concrete cover and the concentration of chlorides ions. [ABSTRACT FROM AUTHOR]

The load features of ground motion are mainly reflected by three factors: amplitude, frequency, and duration. The combination of these factors determines the response of rock-soil mass and the structure safety under seismic load. By finite element method, this paper analyzes the influence of the three factors of ground motion on the dynamic response of a slope. The analysis shows that the slope displacement increased with the elevation from the bottom. The anti-dip fault puts the slope in an unfavorable deformation state. Due to the large residual deformation in the fault zone, a large displacement occurred on the slope top. It was also learned that the adjustment of amplitude only leads to proportional growth in the absolute value of the acceleration of the slope. Under the same conditions, the dynamic responses in different parts of the target slope are not greatly affected by the changing amplitude, but depend more on the material and spectral features of the rock-soil mass. The research results provide a reference for the evaluation and prediction of slope seismic stability and the evolution of slope damage under earthquakes with different frequencies, amplitudes, and durations. [ABSTRACT FROM AUTHOR]

Resonance avoidance is an important topic in engineering seismic design. However, there is little report on the resonance features of rock slopes with anti-dip weak rock layers under seismic actions. Through finite-element method, this paper carries out modal analysis and harmonic response analysis on a slope, captures the natural frequencies and vibration modes of the slope, and plots the resonance curves about displacement frequency relationships. The results show that slope resonance is greatly affected by damping ratio: the greater the damping ratio, the lower the resonance peak; the inverse is also true. This means that weak and broken rock mass is capable of absorbing shocks, but not necessarily easy to be damaged. On the contrary, broken rock mass has poor mechanical performance and is prone to damage under small vibration. Besides, the resonance effect of the slope is mainly excited by the natural frequencies of the first three orders; the vertical resonance displacement peaked at about 1.1 Hz, while the horizontal resonance displacement peaked at about 1.38 Hz. From the vibration modes and frequency response curves, the resonance peak of the slope is amplified in the vertical direction and on the free face, and the maximum resonance displacement appears on the surface of the slope, indicating that the strongest resonance occurs on slope surface. This research fully clarifies the stability and dynamic response law of rock slopes with anti-dip weak interlayer under seismic actions, laying a solid basis for the mic fortification, landslide prediction, and landslide control of slopes. [ABSTRACT FROM AUTHOR]

Seismic verification of masonry buildings based on realistic calculation models and increased behavior factors With the application of the traditional linear verification concept to masonry structures it is already no longer possible to carry out structural safety verifications even for buildings with standard ground plan configurations in areas with moderate seismicity. This problem will be exacerbated in Germany with the introduction of continuous probabilistic earthquake maps. Due to the increased seismic actions, it is necessary to make the existing load‐bearing capacity reserves that have not yet been taken into account available in comprehensible verification concepts in construction practice. This article presents a concept for the building‐specific determination of increased behavior factors. The behavior factors are composed of three components, which take into account the load redistribution in ground plans, the deformation capability and energy dissipation and all kinds of overstrength effects. For the calculation of these three components, a non‐linear verification concept based on pushover analyses is applied, in which the interactions of walls and floor slabs are described by a level of restraint. A non‐linear modeling approach of the overall building is introduced for the determination of the restraint levels, with which the interaction of walls and floor slabs can be simulated. The results of the linear verifications with increased behavior factors for this building are significantly closer to the results of non‐linear verifications and thus the standard ground plan configurations in areas with moderate seismicity can still be verified with the traditional linear calculation approaches. [ABSTRACT FROM AUTHOR]

Seismic verification of masonry buildings in German earthquake regions With financial support of the "Deutsche Gesellschaft für Mauerwerks‐ und Wohnungsbau e.V." (DGfM) and the "Deutsches Institut für Bautechnik" (DIBt) in Berlin, two consecutive research projects were carried out to improve the seismic verification of masonry buildings in German earthquake regions. First, the seismic behavior of three modern unreinforced masonry buildings in the region of Emilia Romagna in Italy during the earthquake series in 2012 was investigated in detail in cooperation with the University of Pavia. Based on the results of these investigations an improved seismic design concept for unreinforced masonry buildings was developed. The paper presents the main results of the conducted research work and their transfer into standardization and engineering practice. [ABSTRACT FROM AUTHOR]

Steel structures are widespread in areas with high seismic activity due to the ductile behavior and efficient energy dissipation capacity. Tubular columns have a better behavior at the lateral forces by seismic actions due to the effective distribution of the material. Combining of these two elements is a real challenge due to the inefficient distribution of the stress in the classical (welded) beam-to-columns joints, which lead to the premature failure of the column flanges by buckling, crushing or veiling which categorically contradicts the "strong column - weak beam" principle, which guides the design of joints according to Eurocode 3. This paper describes several types of beam-to-column connections, designed to solve the problem of the stress distribution in the beamto- column joints, and to ensure efficient energy dissipation. The joints were divided into two different categories depending on the shape of the column section: circular or rectangular; each having a specific design of the joints. However, it should be noted that both types of joints can be adapted to the shape corresponding to the used column section. [ABSTRACT FROM AUTHOR]

Base isolation is a widely-used method used to minimise the harmful effects of earthquakes on buildings. Unlike a fixed base building, a building with a base isolation system essentially decouples the superstructure from the substructure resting on the ground. Then, during earthquakes, the superstructure’s relative displacement is significantly reduced, minimising the structural damage. Auxetics, which are materials with a negative Poisson’s ratio, are known for possessing properties such as high energy absorption. Based on the energy absorbing capabilities of auxetic materials, it is proposed that incorporating them into base isolation structures would positively impact on the performance of the system. Therefore, the article aims to investigate the response of structures under seismic loading incorporating re-entrant hexagon layers into the base isolation system. This is assessed by defining and numerically testing the system using finite element analysis. The models developed for this study represent multi-story structural steel frames combined with fixed base, conventional lead-rubber bearing and auxetic composite base isolation. Differences in the response obtained from the mentioned systems are highlighted. Results indicate that the auxetic base isolation may improve the dynamic response of structures, although a unique performance is not recorded. [ABSTRACT FROM AUTHOR]

The present paper proposes a new methodology for the load-bearing capacity analysis of 2D masonry constructions by extending and reformulating the Continuous Airy-based for Stress Singularities (CASS) method, with a particular focus on the incorporation of volume forces, crucial to solve mechanical problems involving masonry constructions accurately. The masonry material is modelled using a Normal, Rigid, No-Tension (NRNT) model, largely adopted by the scientific community as material parameters, often unknowable, are not needed. The load-bearing capacity problem is derived from an energy-based formulation and framed as a classic limit analysis approach, allowing for the direct determination of the maximum incremental load that a masonry structure can withstand, along with the corresponding internal stress pattern. The structural domain is discretised with a simple finite element mesh, and the Airy stress potential is adopted to enforce the internal equilibrium directly. The boundary value problem is then solved as second-order cone programming (SOCP). The CASS method is shown to offer modelling and computational advantages. Indeed, it accurately describes the mechanical response, including the ability to capture singular stress fields typically exhibited by masonry structures, particularly where cracks appear. The adoption of the Airy potential allows for a reduction in the number of explicit constraints from the problem. Moreover, the formulation of the boundary value problem as a SOCP ensures the existence of a unique load multiplier while offering computationally fast solutions even for large problems. Several numerical examples are presented to demonstrate the CASS potential. Specifically, the ability to capture singular stress patterns diagonally crossing the finite elements showcases the CASS mesh independence, providing a straightforward approach to modelling complex geometries and loading conditions. • Mesh-independent formulation for 2D seismic assessment of masonry façades. • Incorporation of volume forces into the CASS method. • Validation against experimental, analytical, and numerical solutions. • Singular stresses captured as concentrated on narrow bands. • The CASS method reveals the resisting compressive structure activated at the onset of collapse. [ABSTRACT FROM AUTHOR]

Historic buildings have a high architectural value and their maintenance, repair and rehabilitation require a special approach. This approach is mainly based on the buildings’ performance under non-destructive tests such as operational modal analysis (OMA). Under extreme loads, such as earthquakes, these buildings require representative numerical models to simulate their expected response. In historic buildings, tie rods transfer axial loads and are typically used to balance horizontal trust due to static and dynamic loads associated with seismic actions. It is very important to determine the possibility of exceeding their load-bearing capacity under extreme loads, such as an earthquake. In this context, this paper presents an approach for the analysis of seismic action on the tie rod system in a historic building. The analysis was performed by combining the on-site experimental testing and the finite element model updating (FEMU) of the local models of tie rods and the global model of the structure. It was shown that the combination of analyzing local and global structural models, experimental on-site testing and FEMU is a viable solution for assessment of historic buildings’ load bearing capacity.

Abstract. Objectives The aim of the study is to search for methods to improve the efficiency of the earthquake protection systems with rubber-metallic seismic insulating supports by combining them with dry friction and brittle uncoupling elements. Method The research is based on dynamic modelling methods. Results The computational dynamic model of the combined earthquake protection system and the system of differential equations of the seismic motion of a five-story frame building were compiled and an algorithm for estimating the efficiency and selection of the optimum parameters of the earthquake protection system was developed. Horizontal shifting seismic forces, maximum mass movements and maximum movements of rubber-metallic seismic insulating supports at different intensities and prevailing periods of seismic soil oscillations were determined. It is shown that, by using a combined earthquake protection system, seismic loads on frame buildings can be reduced by a factor of 1.5-2 and maximum mass movements – by 4-5 times. In addition, the area of rational application of seismic isolation systems with rubber-metallic supports in relation to the prevailing periods of seismic ground oscillations is expanding substantially. Conclusion The combined earthquake protection system allows the area of effective use of rubber-metallic supports to be expanded by increasing the range of possible prevailing periods of seismic soil vibrations at which the maximum movement of the top of the rubber-metallic supports does not exceed the maximum allowable value. The maximum residual movements of rubber-metallic supports can be reduced by using a lead core.

Nonlinear static analysis, known as a pushover method (NSPA) is oftenly used to study the behaviour of a bridge structure under the seismic action. It is shown that the Equivalent Linearization Method - ELM, recommended in FEMA 440, is appropriate for the response analysis of the bridge columns, with different geometric characteristics, quantity and distribution of steel reinforcement. The subject of analysis is a bridge structure with a carriageway plate - a continuous beam with three spans, with the 24 + 40 + 24 m range. Main girder is made of prestressed concrete and it has a box cross section of a constant height. It is important to study the behaviour, not only in the transverse, but also in the longitudinal direction of the bridge axis, when analysing the bridge columns exposed to horizontal seismic actions. The columns were designed according to EN1992, parts 1 and 2. Seismic action analysis is conducted according to EN 1998: 2004 standard. Response spectrum type 1, for the ground type B, was applied and the analysis also includes 20% of traffic load. The analysis includes the values of columns displacement and ductility. To describe the behaviour of elements under the earthquake action in both - longitudinal and transverse direction, pushover curves were formed.

Energy dissipation and stiffness degradation are important seismic performance indicators within the numerical modelling of structures, and in this case particularly of masonry. They are of great importance for evaluation of the seismic performance of masonry walls. An example of an existing masonry residential building located in Sarajevo, Bosnia and Herzegovina was investigated in this paper. It was observed that during the response of the building to horizontal actions the stiffness degradation of masonry walls was evident.

Steel structures are widespread in areas with high seismic activity due to the ductile behavior and efficient energy dissipation capacity. Tubular columns have a better behavior at the lateral forces by seismic actions due to the effective distribution of the material. Combining of these two elements is a real challenge due to the inefficient distribution of the stress in the classical (welded) beam-to-columns joints, which lead to the premature failure of the column flanges by buckling, crushing or veiling which categorically contradicts the "strong column - weak beam" principle, which guides the design of joints according to Eurocode 3. This paper describes several types of beam-to-column connections, designed to solve the problem of the stress distribution in the beamto- column joints, and to ensure efficient energy dissipation. The joints were divided into two different categories depending on the shape of the column section: circular or rectangular; each having a specific design of the joints. However, it should be noted that both types of joints can be adapted to the shape corresponding to the used column section. [ABSTRACT FROM AUTHOR]

Due to the brittle nature of wood material, the dissipation of seismic energy in timber structures is typically ensured through yielding of the mechanical connectors, where plastic deformations are developed in fasteners that have adequate ductility and cycle-fatigue strength. These structural components are denoted dissipative zones, whereas all other structural elements are assumed to behave elastically. Such elements are designated as non-dissipative zones and are designed with sufficient over-strength, to meet the requirements of capacity-based design (CD). Despite the general consensus that using the principle of CD could lead to safe buildings, where brittle failures are avoided, the applicability of such approach to light frame timber (LFT) and cross laminated timber (CLT) buildings has lacked analytical expressions that depend on the structural typology and failure mechanism. The current paper aims to fill this gap in knowledge by proposing an analytical approach that incorporates the CD philosophy to LFT and CLT buildings at the substructure (wall) and super-structure (building) levels. A simplified approach is adopted for structures with a low-to-medium energy dissipation capacity whereas a more rigorous approach is presented for structure with a high energy dissipation capacity. An experimental comparison and design example is included to present the applicability of the proposal. [ABSTRACT FROM AUTHOR]

Titanium-clad (TC) bimetallic steel is a versatile and high-performance material that offers a unique combination of different service properties, making it ideal for various engineering applications where both durability and strength are critical. Existing studies are exploring the application possibility of TC bimetallic steel in seismic zones. The severe seismic action tends to induce large-strain cyclic reversals in structural members. Thus, it is necessary to clarify the cyclic behavior of TC bimetallic steel under large-magnitude cyclic strains, whose strain range exceeds the strain level of conventional low-cycle fatigue tests. This paper has performed 7 large-strain cyclic coupon experiments on hot-rolled TA2 + Q355B TC bimetallic steel. The influences of different loading protocol on cyclic behaviors are clarified. All hysteretic stress-strain relations of TC bimetallic steel exhibit favorable plumpness under large-strain reversals. The increase in maximum strain and accumulation of plastic strain both induce apparent deterioration on elastic modulus. Based upon the experimental stress-strain relations, the Chaboche combined isotropic/kinematic hardening model parameters are calibrated and validated. The flow stresses of most tests exhibit little change over the full-range plasticity, illustrating that the isotropic hardening behavior is negligible. The cyclic behavior of TC bimetallic steel under large-strain reversals can be precisely simulated by a pure kinematic hardening constitutive model rather than a combined isotropic/kinematic hardening model. The Chaboche parameters calibrated from small-strain and mediate-strain cyclic loading tests tend to overestimate the hysteretic energy dissipation ability under large-strain reversals. In addition, the stress-strain relations of TC bimetallic steel are compared with those of low yield point steels, mild steels and high strength steels. The hysteretic energy dissipation ability of TA2 + Q355B TC bimetallic steel is greater than that of low yield point steels, but less than those of mild steels and high strength steels. • Large-strain cyclic loading tests are performed on titanium-clad bimetallic steel. • Parameters of cyclic constitutive model are calibrated and validated. • Model parameters calibrated from small-strain and large-strain tests are compared. • Behaviors of structural steels and titanium-clad bimetallic steel are compared. [ABSTRACT FROM AUTHOR]

The seismic behaviour of structural systems representing Greek Orthodox churches is examined. All these churches are made of stone masonry in various architectural forms. During the years such churches developed damage to their stone masonry structural elements due to the amplitude of the gravitational forces acting together with the seismic forces. In certain cases such damage was amplified due to the deformability of the foundation. The behaviour of structural systems representing Greek Orthodox churches was simulated through linear and non-linear numerical models. The numerical results together with assumed strength values or failure criteria were utilized to predict the behaviour of the various masonry parts in in-plane shear and flexure as well as out-of-plane flexure. The deformability of the foundation partly explains the appearance of structural damage as can be seen both from observations and the numerical predictions. A limit-state methodology is presented whereby the demands obtained from linear elastic numerical models combined with limit-state in-plane behaviour of unreinforced stone masonry walls in shear/flexure or diagonal tension can yield reasonably good predictions of observed behaviour. Furthermore, the possibilities offered by non-linear inelastic numerical analyses as alternative means for examining the performance of unreinforced stone masonry walls is also briefly presented. Towards this objective, non-linear inelastic numerical simulation results are presented that yield reasonably good agreement with the relevant measured behaviour of stone masonry wall specimens of prototype dimensions that were subjected to simultaneous vertical compression and horizontal cyclic seismic-type loading in the laboratory. The obtained results from these specimens were utilized to also validate an expert system based on this limit-state methodology. Again, the observed behaviour was predicted with reasonable accuracy in terms of bearing capacity and mode of failure by this expert system.

Unreinforced stone masonry made of low strength mortar has been used for centuries in forming old type stone masonry churches of the “Basilica” typology. The seismic performance of such stone masonry structures damaged during recent strong seismic activity in Greece, combined with long term effects from foundation settlement, is presented and discussed. A simplified numerical process is presented for evaluating the performance of such damaged stone masonry structures, making use of linear and non-linear numerical tools and assumed limit-state failure criteria. In order to obtain a quantification of the in-plane sliding shear failure criterion, a number of stone masonry wallets were built with weak mortar and were tested in the laboratory. Through the comparison of the obtained numerical predictions with the observed structural behaviour for selected cases of stone masonry “Basilica” churches, the validity of the applied simplified numerical process is demonstrated. It is shown that reasonable approximation of the observed performance of such structures can be obtained when the assumed failure criteria are realistic.

During seismic events, the gravity loads may cause a reduction of the lateral stiffness of structures; inelastic deformations combined with horizontal loads ( P -Δ effect) can bring to a state of dynamic instability that obviously influences building safety. Especially for flexible structures, the P -Δ effect amplifies structural deformations and resultants stresses, and thus may represent a source of sideway collapse. Since this type of collapse is the result of progressive accumulation of plastic deformation on structural components, the specific objective of this works is to study this effect on a three floor metallic frame (made of aluminium alloy). A non-linear finite element (FE) model of the frame has been developed to study the dynamic non-linear behaviour of the structure, and compare it with the experimental results obtained from a scaled model of the real structure. The FE model, where a simple isotropic hardening behaviour was assumed for the material, was not able to reproduce the real behaviour of the structure. Rather, the correct description of the cyclic plastic behaviour of the material was essential for the numerical analysis of the structure. The characterization of the non-linear behaviour of the material was made by cyclic tension–compression tests on material specimen, from which the coefficients of Chaboche's model were properly calibrated. In this way, the finite element model of the structure provided results in optimum agreement with the experimental ones, and was able to predict the lateral collapse very well. [ABSTRACT FROM AUTHOR]

The given work to some extent meets the shortage of experimental investigations directed to the study of the behavior of buildings with dynamic oscillation dampers. Investigations were carried out by means of vibration testing on a large-scale model of a 9-story frame building. The purpose was revealing the effectiveness and damping properties of two-mass damper and comparing them with the effectiveness of single-mass damper. Before construction of such a damper in a form of an additional tenth floor, the dynamic characteristics of the model (periods and damping factors) were determined and their values are given in the paper. It was revealed that the maximum amplitude of oscillations on the top level of model (the slab of the 9th floor) with the main damper is almost 3 times less than the amplitude of oscillations on the top level of the model without damper. The amplitude of oscillations of the main damper was about 3-4 times bigger than the amplitude of oscillations on the top level of model. A damping factor of the main damper determined by the record of free oscillations was equal to =0.7%.Then the damper was transformed from the single-mass to the two-mass damper by suspending the second mass to the slab of the main damper The obtained results show the high effectiveness of the two-mass damper as its damping degree reaches to about 4.4, that is 46.7% bigger than that of one-mass damper. If before suspending the second mass to the single-mass damper its maximal amplitude was about 3.5cm, then after it the amplitude became equal to 1.4cm. The experimental investigations confirm the quite high effectiveness of the dynamic oscillation dampers and incontrovertible expediency of their application for increasing of earthquake resistance of buildings and structures.

A rigid block modeling approach is presented for rocking dynamics and nonlinear static analysis of dry-joint masonry structures subjected to settlements and earthquake excitations. For the different types of analysis, a unified optimization-based formulation is adopted, which is equivalent to the system governing the static and dynamic structural response. Sequential solution procedures are used for time integration and for pushover analysis which take into account the effects of large displacements under the combined action of support movements and lateral loads. No-tension elastic contacts with finite shear strength are considered at block interfaces for time-history analysis and to obtain the elastic branch of pushover curves in nonlinear static analysis. A unilateral rigid contact behavior is also considered to obtain the descending post-peak branch of pushover curves corresponding to the activation of the rigid-body rocking motion, according to displacement-based assessment methods of failure mechanisms adopted in the standards. Comparisons with numerical models and experimental tests on a rocking block and on a buttressed arch are presented to show the accuracy of the developed approach. Simple tests on dry-joint tuff panels on the tilting table were also carried out to show the effects of imposed movements at support on the response to lateral loads. Finally, an application is presented to a full-scale triumphal arch subjected to the combined action of support movements and earthquake excitation to discuss, on the basis of the developed model, the effects of settlement-induced damage on seismic performance. The numerical analyses showed that the lateral force, the displacement capacity and the rocking response can be significantly affected by support movements, pointing out the relevance of the current building condition in the seismic safety assessment. • A 2D rigid block modeling approach is presented for rocking dynamics and nonlinear static analysis. • An integrated optimization-based formulation is used to take account the effects of settlements on seismic response. • No-tension frictional contacts are considered at block interfaces. • Applications are presented to evaluate the effects of settlements on seismic capacity by pushover and time-history analysis. [ABSTRACT FROM AUTHOR]

Full dynamic analyses that follow a coupled approach for the soil-structure interaction, provides satisfactory interpretation of non-linear boundary problems during earthquakes. This paper illustrates the results of a numerical study aimed at modelling the performance of continuous and segmental linings of shallow tunnel under seismic loading. A set of 3D finite-element full dynamic analyses have been carried out, calibrated on the experimental results of a centrifuge test on a model tunnel in a dense dry sand layer subjected to transversal dynamic loading [1]. The numerical study was extended to model and compare the seismic demand of a continuous and a segmental reinforced concrete lining, including the effect of the excavation process on the pre-seismic conditions and the influence of different input signals. The results show that even in rather simple ground conditions, a suitable constitutive model for soil is needed to capture the effect of soil-lining interaction during and after the seismic event. [ABSTRACT FROM AUTHOR]

The first part of the paper presents the results of two series of in situ pull-out tests of injected anchors embedded in existing yellow tuff masonry walls. Anchors are made of steel and GFRP bars with diameter of 12 and 20 mm and were embedded by means of two types of grout: a cement-based and a pozzolana-based grout. The results were examined in terms of both maximum load and displacement to determine the most efficient bar-grout coupling. The experimental pull-out forces are also compared with the predictions given by several literature formulas. The second part of the paper is devoted to verify the efficiency of the tested injected anchor systems for avoiding out-of-plane damage mechanisms in masonry walls having varying slenderness and subjected to horizontal forces; to this aim parametric analyses were performed to calculate the seismic acceleration required to activate several out-of-plane mechanisms and to verify the effectiveness of injected anchors similar to those experimentally tested into avoiding them. [ABSTRACT FROM AUTHOR]

Anchors used in seismic applications have to resist cyclically pulsating loads and cyclically opening and closing cracks which potentially intersect the anchor location. In reality, cyclic load and cyclic crack phenomena act on anchors simultaneously; however, seismic tests in laboratories are carried out with either one of the two parameters kept constant. To investigate the effect of simultaneous load and crack cycling on anchor behavior, experimental tests with synchronized load and crack cycling protocols on headed bolts cast in special concrete specimens were carried out. The test results demonstrate that the anchor displacement depends on the phasing of load and crack cycling, and justify the reduction of the constant anchor load during simulated cyclic crack tests to compensate for disregarded load cycling effects. The influence of various phase lags and different frequencies on the relative anchor displacement is described by an analytical model based on the integrated cumulative damage regime. [ABSTRACT FROM AUTHOR]

This paper presented an innovative method for nonlinear simulation of masonry structures under seismic loading conditions. The method is based on a macro-modeling formulation of a masonry panel. A new finite element (FE), called a 'multi-fan' (MF) element, is developed on the macro scale, whereby the stress field within the panel is determined at each load step by minimizing the current complementary potential energy. Because only one element is required to model a single masonry panel in the structure, this approach enables a reduction in the total number of degrees of freedom (DOFs) of the system and the total computational effort. The ability of the proposed approach to estimate the ultimate capacity of masonry walls was analyzed both by comparing its predictions with available experimental results and through FE analyses based on a micro-modeling approach. The comparisons show satisfactory accuracy at both the global and local levels. Therefore, the new macro-element can be effectively used in safety assessments of masonry buildings. [ABSTRACT FROM AUTHOR]

SUMMARY The response of structures subjected to seismic actions is always influenced by P-Δ effects. The importance of this effect is generally modest for structures experiencing an elastic response but often relevant for structures responding well within the inelastic range of behaviour. Seismic codes indicate that P-Δ effects may be counterbalanced through an increase in the structural strength required by a first order analysis. This increase is calculated by means of a strength amplification factor. The expressions suggested in codes for this factor are simplistic and often criticized by researchers. In this paper, the effectiveness of some of the provisions reported in the literature or suggested in seismic codes is evaluated on single degree of freedom systems with different periods of vibration. As suggested by past studies, attention is focused on the influence of the interstorey drift sensitivity coefficient, significant duration of the ground motion, class of the site soil, displacement ductility and equivalent viscous damping ratio of the system. Finally, an accurate expression of the strength amplification factor is proposed. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]