Seismic assessment of a building will typically require consideration of its nonlinear force-displacement response. Such information can be estimated from pushover analysis, also referred to as ...nonlinear static analysis, in which the structure is analyzed for incrementally increasing lateral loads and the nonlinear structural behavior is accounted for during the analysis by updating the stiffness matrix at each load increment. A number of computer programs are now available to permit the application of pushover analysis in practice. However, it is argued that there is a need for simplified pushover analysis methods to permit independent checks of computer outputs and also to inform engineers of the key characteristics of the structural system being assessed. This work builds on previous contributions in the literature to provide a simplified pushover analysis approach for reinforced concrete (RC) frame structures. A novel procedure for the assessment of the displacement profile of RC frames is provided, with guidelines to account for different types of yielding mechanisms. By comparing force-displacement response predictions with those obtained from rigorous nonlinear static analyses for a range of frame configurations and mechanisms, it is shown that the proposed approach offers an effective means of undertaking simplified pushover analysis.
•This work assesses the influence of various weld patterns between beam and end-plate on the global ductile behavior of pallet racks, being one of them a novelty.•This assessment is performed by ...means of pushover analysis.•The influence of the level height is studied throughout two rack configurations.•Different numerical models for racks are presented, aiming to capture the influence of upright perforations and 3D effects.
This paper presents numerical pushover analyses on multiple bay pallet racks, aiming to quantify variations in global ductility when using different beam-to-upright connections. The connections differ in the layout of the beam-to-endplate welding, being one of them a technological novelty. They are modeled with envelopes of monotonic and cyclic moment-rotation curves obtained from component tests and presented in previous research. Moreover, the influence of the level height is studied throughout two different rack configurations. A single-column model for multiple bay racks, made with 3D beams and shells, is presented and compared with simpler 2D models to quantify the influence of 3D effects and upright perforations. Results exhibit that the novel connection improves the capacity to absorb energy, but an inappropriate rack configuration can lead to a soft-story mechanism, thus not taking full advantage of its ductility.
•The corrosion effects due to the carbonation phenomenon are evaluated considering existing RC bridges.•Multi-modal pushover analysis was conducted in order to evaluate the influence of the corrosion ...effects on the seismic performance of existing RC bridges considering two different collapse mechanisms: the ductile collapse mechanism and the brittle collapse mechanism.•The results are summarized in terms of appropriate risk indices to highlight the evolution of the collapse mechanisms during the life of the structure.
Recent collapse events of existing reinforced concrete bridges have increased the attention on the mandatory and suitable maintenance of these strategic constructions. In fact, most of these failures were due to an inadequate scheduling of maintenance interventions. One of the main issues concerning the load-bearing capacity of existing reinforced concrete structures is related to the steel reinforcement corrosion caused by carbonation phenomenon. Such aspect should not be even more overlooked considering the strategic role of infrastructures like the bridges of the Italian motorway network, mainly built around the 1960′s and widely used even right now. Consequently, reinforced concrete bridges require the execution of maintenance interventions in order to guarantee an adequate safety level under both serviceability conditions and exceptional loads, also considering that they were often designed without taking into account seismic actions.
This paper investigates the seismic performance of five existing reinforced concrete bridges under several corrosion scenarios of piers steel reinforcement caused by carbonation phenomenon. In particular, three different corrosion levels (slight, moderate and high) are considered by analysing the evolution of the phenomenon effects for a structure lifetime equal to 75 years. The seismic vulnerability is evaluated by defining appropriate risk indices expressed in terms of peak ground acceleration and corresponding return period. The risk indices are determined by performing modal pushover analyses on finite element models of the bridges, considering the corrosion effects in terms of steel rebars cross section reduction. Some correlations between corrosion levels and risk indices are drawn.
Three-dimensional nonlinear finite element analyses are conducted to evaluate the seismic performance of rectangular prefabricated and cast-in-place underground structures considering soil-structure ...interaction. The finite element models are developed based on a prefabricated subway station project in Beijing. The seismic loading conditions, damage evolution, structure deformation, internal forces and the performance index limits values are compared for prefabricated (assembly monolithic (AMT) and assembly spliced (ASF)) and cast-in-place (CIP) underground structures. Numerical results indicated that the degree of plastic damage at center column of prefabricated underground structure was less than that for CIP underground structure. The failure mechanism of both types of underground structures was the same, the central column first lost its bearing capacity then the side wall failed. The column's internal force of ASF structure was significantly reduced compared with that of CIP structure, and the most unfavorable seismic position of the three structures is the bottom of the lower column. It was also found that vertical ground motion can significantly accelerate prefabricated underground structural destroy, but it has little effect on the horizontal displacement. Finally, index limits are quantified for four seismic performance levels of prefabricated underground structures, which can be considered in performance-based design of prefabricated underground structures.
•The differences between the prefabricated underground structure and the cast-in-place underground structure are compared.•The effect of vertical ground motion on seismic performance of underground structure is analyzed.•Index limits are proposed for four seismic performance levels of prefabricated underground structures.
This paper investigates the seismic capacity and collapse mechanism of dry-joint masonry towers built with different ancient construction techniques at the Caria and Pamphylia regions in Turkey. A ...discontinuum type of analysis is performed, where masonry towers are represented as a system of individual rigid blocks based on the discrete element method (DEM). The dimensions and the morphology of the masonry towers are obtained in-situ and then utilized in the computational models. Therefore, the wall cross-section morphologies reflected in the numerical models are accurate and authentic. The motion and mechanical interaction of blocks are computed by integrating the equations of motion and point contact approach based on the relative contact displacement, respectively. The seismic capacity and behavior of masonry towers are analyzed by subjecting them to increasing horizontal forces applied in different orientations. Once the modeling strategy is validated, it is further utilized to better understand the local and global failure mechanisms of ancient masonry towers constructed with different masonry bond patterns. The results of this study highlight the importance of workmanship for the dry-joint masonry structures and underline the significance of the geometrical properties in ancient constructions that influence both the capacity and collapse mechanism.
For structural engineers, existing surrogate models of buildings present challenges due to inadequate datasets, exclusion of significant input variables impacting nonlinear building response, and ...failure to consider uncertainties associated with input parameters. Moreover, there are no surrogate models for the prediction of both pushover and nonlinear time history analysis (NLTHA) outputs. To overcome these challenges, the present study proposes a novel framework for surrogate modelling of steel structures, considering crucial structural factors impacting engineering demand parameters (EDPs). The first phase involves the development of a process by which 30,000 random steel special moment resisting frames (SMRFs) for low to high-rise buildings are generated, considering the material and geometrical uncertainties embedded in the design of structures. In the second phase, a surrogate model is developed to predict the seismic EDPs of SMRFs when exposed to various earthquake levels. This is accomplished by leveraging the results obtained from phase one. Moreover, separate surrogate models are developed for the prediction of SMRFs’ essential pushover parameters. Various machine learning (ML) methods are examined, and the outcomes are presented as user-friendly GUI tools. The findings highlighted the substantial influence of pushover parameters as well as beams and columns’ plastic hinges properties on the prediction of NLTHA, factors that have been overlooked in prior studies. Moreover, CatBoost has been acknowledged as the superior ML technique for predicting both pushover and NLTHA parameters for all buildings. This framework offers engineers the ability to estimate building responses without the necessity of conducting NLTHA, pushover, or even modal analysis which is computationally intensive.
•Generated 30,000 random steel buildings for surrogate model development.•Established novel design of experiment framework for surrogate modelling.•Used material, geometry, seismic, and pushover factors for surrogate development.•Developed GUIs for pushover and time history analysis prediction.•Used 13 ML methods for building response prediction with advanced feature selection.
Abstract The transition from the Uniform Building Code (UBC-97) to the International Building Code (IBC-21) marked a major shift in the definition of seismic hazard. The term “seismic hazard” in the ...form of peak ground acceleration (PGA) is replaced by spectral acceleration. This paper investigates the effect of using new seismic hazards on the structural performance of reinforced concrete (RC) buildings. It also looks into the financial impact on the capital costs of new buildings. Useful insights are made to understand the structural performance and financial impact of adopting IBC 21 for structural design in contrast to UBC 97. This study was carried out from the perspective of a developing country, Pakistan. Reinforced concrete moment resisting and dual frames are used as the main structural system of a typical 7-story residential building to investigate the aforementioned effect. The frames are assumed to be located in two locations with high and low seismic hazards. The effect on structural performance is investigated via nonlinear pushover analysis. Financial impact is judged mainly through cost estimation for steel and concrete. A detailed discussion is also presented on the seismic design guidelines in both codes.
In this research, the seismic behavior of single-layer diamatic dome (SLDD) structures was analyzed under earthquake loads, and then the seismic response modification factors (SRMFs) of these ...structures were extracted. For this purpose, 16 models with different span lengths (SLs) and rise-to-span ratios (RSRs) were designed, and the effects of SL and RSR on the SRMFs of these structures were evaluated. Also, the effect of member density on the SRMFs was studied. The models were first designed under the applied loads based on relevant design codes. Then, by performing the nonlinear time history analyses using the three translational components of ground motion records, the control point and target displacement in the horizontal and vertical directions were obtained to implement the pushover analyses. Thereafter, the pushover analyses were implemented by using the target displacements derived from the nonlinear time history analyses, and the SRMFs of SLDD structures in both horizontal and vertical directions were obtained. The results indicate that models with RSRs of 1/7 to 1/3 remained in the elastic range in the horizontal direction. For the models with an RSR greater than 1/3, if the RSR increases, the ductility and behavior factor increases in the horizontal direction. However, there is a downward trend in the vertical direction due to the increase in the vertical stiffness. The horizontal and vertical behavior factor was obtained in the range of 1.155–2.459 and 1.155–2.893, respectively. Finally, by using the results obtained and through the nonlinear regression analysis, equations were proposed for the period, target displacement, displacement amplification factor, and behavior factor for SLDD structures in terms of the SL and RSR in the horizontal and vertical directions.
•The seismic response modification factors (SRMFs) of single-layer diamatic dome structures are extracted.•The effect of member density on the SRMFs is studied.•Equations were proposed for the period, target displacement, behavior factor, and displacement amplification factor.•The SRMFs of these structures are obtained in both horizontal and vertical directions.
