Papers by Keyword: Nonlinear Analysis

Abstract: Using capacity spectrum method was analyzed frame reinforced concrete structures. Capacity spectrum method has been used to analyse frame reinforced concrete structures. Geometry, material properties and reinforced cross sections were designed by experimental tested model of reinforced concrete frame joints in the scale of 1:1. The results were compared with the results of the analysis of the structure of the same geometrical characteristics but of standard material properties of concrete and steel.

Abstract: This article deals with a nonlinear analysis of the detail of the dapped-end beam, the design of which in practice usually employs the design procedures based on the strut-and-tie method. The article is a follow-up to the contribution released in 2014 which presented the experiment carried out with a view to verify the design procedure and to the study showing the influence of the used amount of vertical and inclined hanger reinforcement on the bearing capacity and behaviour of the detail under load. The experiment also included the tests of material properties performed on the used concrete. Along with the inspection certificates issued for the used reinforcement, these tests served as a basis for the nonlinear finite element analysis by the ATENA software. This article presents and compares the results of the aforementioned analysis and experiment.

Abstract: Fragility curves for typical multi-span simply supported concrete box girder bridges in eastern China are presented. A set of bridge samples, of which five uncertain parameters are considered, is established using the Latin hypercube sampling. Nonlinear time history analyses are conducted to capture the structural response quantities. Probabilistic seismic demand models are formulated by quadratic regression analysis for the capacity/demand ratios. Fragility curves of bridge components are developed and the fragility of bridge system is evaluated using the first-order bound method. The results show that the columns and expansion bearings among bridge members are more fragile under earthquake excitation, and the bridge system is more fragile than any bridge component. The typical bridges have more than 50% probability when subjected to PGAs of 0.46, 0.58, 0.82, and 1.0g for four damage states, respectively. The fragility curves can be used for retrofit prioritization for this type of bridges.

Abstract: A building context as complex as that of many historical centers in Europe is the typical scenario where more and more technicians found themselves at work. In addition to the usual difficulty of dealing with the complexity of masonry building clusters, they particularly feel the lack of the essential support of dedicated computational tools. In fact, the calculation codes currently available do not address modeling and analysis of building clusters in a personalized manner. VENUS, Italian acronym for Nonlinear Assessment of Structural Units, is a software developed in C++, which deals with the seismic assessment of building clusters in an integrated manner, accompanying the practitioner from the early stages of defining the level of knowledge, to the management of the design quantities, until the graphic elaboration of the results. Finally, it allows to test the effectiveness of a local intervention with traditional and innovative strengthening techniques and to evaluate its effects on the global response. Finally, a brief description of a stochastic approach foreseen in a future version of the software is discussed.

Abstract: The seismic response of non-structural components in civil and industrial buildings, often neglected or disregarded in the common design/assessment practice, revealed its dramatic relevance in recent seismic events that resulted in significant damage observed in the wide class of “objects” referred to as “non-structural components” (e.g., partitions, masonry infill, suspended ceilings, finishing, specific equipment and so on. The observed damage, sometimes leading to collapse of these components and even loss of human lives, highlighted the lack of knowledge that still affects both analysis procedures and design/assessment methods currently adopted for analysing their seismic response. This paper is mainly intended at providing readers with an overview of both the historical development and the current state of the formulations adopted by codes and standards for evaluating the maximum accelerations induced by seismic shakings on non-structural components. The difference among these formulations is firstly outlined and the predictions based on the most up-to-date codes are compared with the results of a wide parametric analysis based on a 2DOF system, intended at simulating the coupled response of both main structure and non-structural component. This parametric comparison shows that the current formulations are not fully capable of reproducing the effect of the interaction between main structure and non-structural components

Abstract: Advanced numerical simulations are more often used due to the increasing possibilities of computer technology. For material descriptions, generally nonlinear constitutive relations are employed. It is expected that in the near future the reliability of structures will be assessed by use of these sophisticated calculations. For this purpose, it is firstly necessary to evaluate the model uncertainty of the numerical model, because the structural reliability is directly affected by the model uncertainty. Recommended values of model uncertainties differ in individual scientific literary sources. In standard codes the partial safety factor for model uncertainty is set by relatively low value. This value was assessed by empirical way and it seems that such value is valid only for flexural failure. Contemporary numerical simulations indicate larger model uncertainties. Moreover, the value of model uncertainty should be related to particular failure mode. This paper presents a comprehensive procedure for the determination of model uncertainties of nonlinear analyses. In the second part, the value of model uncertainties is derived for punching of slabs.

Abstract: This paper presents a numerical investigation on the effect of perforation to the steel purlin on bending behaviour. In order to reduce the weight of steel sections, web profile with openings has been introduced in the construction industry, so does the purlin. However, there is no research done on the C-purlin with perforation. Hence, 33 nonlinear analyses were carried out to investigate effect of perforations to the steel purlin on bending behaviour. Yield moment of the steel purlin with and without perforation will be determined. And, effect of various perforation shapes and size on bending behaviour is investigated. Finite element model was developed using software LUSAS. C-channel steel section without opening is used as a control specimen. The results are expressed in term of yield moment. The results show that the edge distance from the opening to the support plays an important role in affecting the moment capacity of C-purlin. Increasing the opening spacing would increase the moment capacity. Number of openings also affects the moment capacity of the section. Octagonal shape with 0.40H and e= 350 mm shows the highest yield moment value with 16.318% higher than that of section without opening. In conclusion, perforation increases the moment capacity of the C-steel purlin.

Abstract: In this paper the behaviour of old floors made up of wrought iron beams supporting shallow masonry vaults is analysed. The performance of this structural system, which was extensively used in Europe in the XIX century, has been only marginally investigated thus far. Very few studies on masonry-iron composite floors are available in the literature, where the role played by the physical interaction between the vaults and the metallic profiles has yet to be fully understood. When assessing historical buildings with floors characterised by the analysed floor system, a realistic estimate of this interaction may be critical to avoid unnecessary and costly strengthening works. The floor structure with composite wrought iron beams and solid brick vaults of the “Military Hospital” in Trieste built in 1840 by the Hapsburg Military Administration have been investigated performing physical experiments and numerical simulations. Experimental tests were carried on the floor and used to calibrate finite element numerical descriptions. These have been adopted in numerical simulations to investigate the response of the analysed floor system up to collapse considering different geometrical characteristics for the floor. The numerical results shed some light on the actual interaction between the different components of the composite floor which significantly influences the floor stiffness and load bearing capacity.

Abstract: This paper proposes a nonlinear analysis of voltage sag magnitude and angle for fault distance calculation in distribution system. The method first identifies the fault section. Then, a rank approach is followed to identify and prioritize the faulty section. Later, the fault distance is calculated by creating a second order polynomial passing through the fault node. The testing is carried out in an actual distribution system of an electrical utility in Malaysia with 37 nodes. The test results show that the proposed fault distance gives very small percentage error.

Abstract: Composite slabs with prepressed embossments present an effective solution for horizontal load bearing structures. Sheeting serves as a formwork in construction stage and as a tension bearing member after hardening of concrete. There is no need for additional tensile reinforcement in case of sufficient longitudinal shear bearing capacity of the embossments. Longitudinal shear bearing capacity is not precisely determined when designing according to nowadays standards. Full scale bending tests of the slabs are used to determine characteristics for m – k method or partial connection method. Bending tests are expensive and space demanding. Alternatively small-scale shear tests can be used to determine shear characteristics of the sheeting. However, shear tests cannot include all the effects affecting the bearing capacity of bended slab, such as effect of curvature or distribution of load. Therefore, related design method has to be used to determine load bearing capacity of the slab in bending. This paper extends achievements presented by the authors in contribution in CRRB 2013. The results of small-scale tests are compared with results of numerical models of the slab in shear. Numerical models are created in two different finite element codes. Setting of steel-concrete interface properties in the models is validated using data from literature.