Papers by Keyword: Nonlinear Analysis

Abstract: The application of high-strength prestressing steel represents a major step forward in the field of concrete structure design and construction. Prestressing steel with a tensile strength exceeding 1860 MPa enables more effective prestressing of structural elements, which in turn results in a substantial reduction in the required amount of reinforcement. At the same time, it allows for the design of more slender, lighter, and structurally optimized members. Due to these characteristics, this type of reinforcement finds wide application particularly in bridge engineering, prefabricated systems, high-rise buildings, and long-span structures. The paper focuses on analysing the principal advantages of employing high-strength prestressing reinforcement with regard to both structural behaviour and construction economy. From the structural design perspective, the main benefits include an increase in load-bearing capacity and a reduction of deformations, even when using smaller cross-sectional dimensions. From the economic viewpoint, advantages are primarily linked to reduced material consumption, lower self-weight of prefabricated elements, and significant cost savings in transport and erection. The concluding part of the paper addresses the anticipated direction of further development in high-strength materials, with particular emphasis on the possibilities of design optimization through nonlinear computational methods. High-strength prestressing reinforcement thus constitutes a promising means of improving the efficiency and sustainability of modern concrete structure design. The study provides a comprehensive summary of the main benefits of this technology, points out practical and design-related limitations, and indicates future development trends consistent with the objectives of sustainable and cost-effective construction.

Abstract: This article deals with increasing the load-bearing capacity of reinforced concrete panels by replacing the compressed part of the cross-section by a layer of ultra-high performance fiber reinforced concrete (UHPFRC). The geometry of the tested samples is based on a real example of a ceiling slab in a typical multi-storey car park. The load curves of the individual variants are compared using numerical simulation with nonlinear material models describing the specific behavior of concrete. In conclusion, the contribution of the UHPFRC layer to the properties and behavior of the investigated structure is evaluated.

Abstract: This article develops two three-dimensional models: one for designing an 18-story building, considering the E030 and E060 norms of Peru, and a second nonlinear model aimed at estimating the lateral capacity of the structure through nonlinear static analysis and verification of seismic performance. It highlights the prevalence of informal structures in Peru, which lack a performance-based design methodology. In this context, relying solely on elastic design may be insufficient, especially for tall buildings. A "seismic gap" is identified, referring to the discrepancy between current design practices and the actual seismic demands that structures may face, raising concerns about the vulnerability of existing and future structures to a potential earthquake. The nonlinear static analysis showed that the 18-story structure reached a maximum base shear of 1752 tons and a maximum displacement of approximately 53 cm in the X direction, and similarly, a maximum base shear of 1538 tons and a maximum displacement of 51 cm in the Y direction.

Abstract: The article is devoted to the description of analytical and structural methods used in the design to avoid progressive collapse of buildings and structures in the case of extreme influences. Three directions are described to avoid the process of development of local to global destruction. The concept realized in the LIRA-SAPR software, which is aimed at automating analysis for progressive collapse in quasi-static and dynamic formulations, including linear and nonlinear analysis taking into account the dynamic factor, is also substantiated. The purpose of the analysis is to design structures for various purposes, which in addition to accident-free performance of functions during the specified period of operation, in case of an accident due to natural and man-made phenomena (defects in production technology, explosions, impacts), as well as other causes not provided for by the conditions of normal operation, would cause minimal damage to people and the environment.

Abstract: The work is devoted to the numerical analysis of connections of light frame elements in the Sunday system technology. The analyzed technology is described, which in the light of the requirements in terms of structure mechanics as well as more and more stringent energy efficiency is an economical and effective solution. Complex numerical calculations require the introduction of appropriate input data to create computer models. In order to perform the simulation, the influence of the adopted schematic characterization of the material on the course of the stress-strain curves obtained by numerical analysis using the Ansys Reaserch 2021 program based on the finite element method was presented. The authors described the procedure for performing numerical analysis, taking into account material nonlinearity. The material models used for this type of calculations were also noted. On the example of a connection of elements of a light frame structure, the influence of the adopted material characteristics on the result of the obtained numerical calculations is presented.

Abstract: Floors have a key role in the seismic behaviour of structures, especially in multi-story buildings. The in-plane behaviour of a floor system influences the seismic response of the structure significantly and affects the distribution of lateral forces between seismic resisting systems and over the height of the structure. In buildings where the seismic resisting systems are in the same location in plan on each floor over the height of the building, inertial and displacement compatibility shear forces are the principal shear forces generated at the interface between the floor system and the seismic-resisting system. These two are called interface diaphragm forces. These interface forces must be transferred into the appropriate lateral load resisting system and the interface must be well designed and detailed. Determination of the magnitude of the interface loads on concrete diaphragms are not well understood and still a matter of debate. There is no consensus of a design procedure for determining the diaphragm actions and distribution into the seismic resisting systems. In this paper, interface forces generated in floor diaphragms by asymmetrical actions of the braced framing system on each side of the building in the direction of analysis have been investigated. A numerical study using Numerical Integration Time History Analysis (NITH), has been undertaken to evaluate the interface forces of concrete floor diaphragms in a 12-story braced steel building. The results of nonlinear time history analyses using ground motion records from three different earthquakes are presented.

Abstract: The work herein presented is devoted to the validation of TPMC design procedure applied to steel MRFs equipped with FREEDAM dampers located at beam-to-column joints. The seismic performances evaluations of the designed structure have been carried out by means of both Push-over analysis and Incremental Dynamic Analysis. In particular, the Push-over analysis aims to confirm the real development of a collapse mechanism of global type, while, through IDA analysis, Maximum Interstorey Drift and Top Residual Displacement performed by the designed structures have been pointed out. For this reason, a MRF whose design procedure by TPMC is detailed in a companion paper has been subjected to both push-over and IDA analysis.

Abstract: Supplemental dissipation plays a vital role in reducing structural damage, repair costs, and downtime due to earthquakes. A hybrid dissipation mechanism has been developed to offer repeatable and consistent energy dissipation, while maintaining significant re-centring capability. This dissipation device consists of a viscous damper (VD) and a friction ring-spring (RS) combining rate-dependent dissipative behaviour of the viscous device with rate-independent dissipation and re-centring from the ring-spring. This approach, ensures simultaneous displacement reduction and increased self-centring potential. Spectral analysis of a single-degree-of-freedom structure has been carried out to outline the efficacy of the device and delineate the impact and contribution of each component to the overall device behaviour. A prototype hybrid device is tested comprising a viscous damper with silicone fluid and a ring-spring with peak design force of 26kN. These components are connected in a parallel configuration through a fixed outer shell and a moving coupled shaft. Experimental proof-of-concept testing for the hybrid device and single ring-spring includes sinusoidal displacement inputs with amplitude of 25 and 30 mm, loading frequencies of [0.25-1.75] Hz, and ring-spring pre-load of 21 and 34%. The overall device has a peak response force of 32kN at input velocities of ~200 mm/s. At this speed, ~20kN comes from the ring spring and ~12kN from the viscous damper. Further tests on the single viscous device are conducted using silicone oils with viscosities of 100, 500, and 1000 cSt and peak input velocities of [50-300] mm/s to evaluate the impact of viscosity on the damping force. These experimental tests are used to delineate the function of the individual components of the device and assess the behaviour of the hybrid combination, in comparison to the predicted analytical behaviour.

Abstract: A heritage building in Wellington, New Zealand (NZ) was classified as potentially earthquake-prone following an initial seismic assessment (ISA) by the Wellington City Council (WCC). The first four stories of the building were constructed originally in 1908 and an additional lightweight story was added in 1955 and altered in 1993. The building has a rectangular floor plan measuring 24 x 10.5 m. In the longitudinal direction, steel frame with solid unreinforced masonry (URM) infill walls provided resistance to seismic forces. In the transverse direction, perforated URM walls with large openings and nonductile concrete encased steel frames were used for both gravity and seismic load transfer. A detailed seismic assessment (DSA) of the building structure confirmed seismic capacity of the building in excess of 100% of New Building Standards (%NBS) in the longitudinal direction. However, in the transverse direction, the structure, secondary components and non-structural components had a seismic capacity less than 34%NBS, hence the building was confirmed earthquake-prone in its current state under the NZ Building Act. Performance-based engineering was used to devise the seismic retrofit for the principle structure. To retrofit the principle building structure to 100%NBS in the transverse direction, new Buckling Restrained Braced (BRB) frames were designed to carry seismic load. A geotechnical investigation showed that the underlying soil was competent and thus soil-structure interaction (SSI), tie foundation beams and nonlinear analysis were used to obtain realistic demand and capacity for the building after seismic retrofitting. The BRB manufacturer was consulted and the BRB size distribution along the height was optimized. The construction of the seismic retrofit is currently underway.

Abstract: The aim of the paper is a nonlinear analysis of concrete structures. For these type of tasks is an important suitable choice of model input parameters and concrete. Especially if the analysis is preceding the results of an experiment, which can determine the exact properties of concrete. The following properties of concrete are needed for nonlinear analysis: tensile strength and compressive strength of concrete. There are more procedures how to determine some unknown input parameters. The paper presents some approaches to calculating and selecting parameters, which are based primarily on the recommendations of the Model Code and professional articles. Specifically, the numerical analysis performed in our developed program which allows observing a nonlinear behaviour of concrete at loading case.