•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.
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.
•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.
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.
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.
The earthquake probabilities worldwide prove that the structure’s quality, especially in the foundation, is needed. Performance Based Design (PBD) is also required tremendously in current society to ...make more efficient and effective construction. This research aims to identify and study the emergence of the overturning moment in the foundation under earthquake loads. The foundation was performed by pushover analysis until 70 mm displacement. The foundation was modelled as a constitutive model of a pile group with a 3x3 configuration and embedded in one layer of clay soil with different values of undrained shear strengths (Su), which were 40 kPa – 100 kPa with 20 kPa increment as the representation of the soil stiffness parameters. A whole model was modelled as Beam-on-Nonlinear-Winkler-Foundation (BNWF), and the soil was presented as a series of Winkler springs using the nonlinear p-y method. OpenSees application, which uses the finite element method (FEM), was used for this research. The pushover analysis has shown that stiffer soil makes more significant lateral responses in the same displacement. The sectional and reinforcement-yielding phases of stiffer soil occur in a smaller displacement than the softer soil, except for Su 40 kPa. The overturning moment was identified as the axial responses increased in the lead pile and decreased in the middle and rear piles. Combining the bending moment responses, axial responses, and yielding phase data, it can be concluded that overturning occurs when sectional yielding happens and ends when the bending moment reaches its maximum value. A stiffer soil results in a shorter period of overturning moment. The overturning moment is caused by the change of the relative stiffness in every pile row due to the development of the plastic hinge and the difference of P-Multiplier values in every pile row, where the change impacts the transformation of the axial response. The PBD concept should be more provided as the overturning moment is related to stiffness variation, resulting in different responses.
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.
Large earthquakes in the last 25 years have caused significant damage to buildings and infrastructure, including the partial or total collapse of storage tanks in various industries. Elephant foot ...buckling, or local buckling at the base, is one of the main failure modes observed in these structures, and this failure mode can lead to their collapse and/or complete loss of contents. Although hydrostatic and hydrodynamic loads typically affect the seismic response of tanks, the effect of soil type on tank buckling behavior has not been widely studied or recognized. This research aims to evaluate the effect of soil type on seismic fragility of tanks by analyzing typical storage tanks used in the wine industry. The work focuses on elephant foot buckling for tanks with both unanchored and anchored bases and compares the influence of three different types of soil and two different tank geometries. The approach uses the capacity spectrum method, as opposed to the more commonly used incremental dynamic analysis, to determine a critical peak ground acceleration to cause buckling at the tank. The tanks were subjected to 21 Chilean seismic records with three different soil types and a no-soil condition. From the results a lognormal fragility curve, and its median and standard deviation, are calculated. The results indicate that unanchored tanks built softer soils exhibit poorer performance, while tanks in competent soils and rock exhibit good performance. Anchored tanks show less sensitivity to soil types than unanchored tanks. The study demonstrates the importance of considering soil-foundation-structure interaction for wine storage tanks, but the results indicate that many comparable storage structures will be similarly affected.
•Examining how soil-foundation-tank interactions affect liquid tank buckling with finite element models•Seismic fragility of liquid storage tanks is evaluated for three different soil types.•The soil type induces dispersion in the seismic fragility curves.•Anchoring tanks is shown to reduce the dispersion in the seismic fragility curves.
This paper presents an equivalent non-uniform inelastic beam-like model for the evaluation of the nonlinear behaviour of multi-storey buildings subjected to earthquake loadings. The proposed beam can ...be used to model buildings with non-uniform mass and stiffness distribution. The model is characterised by a number of degrees of freedom corresponding to the number of floors of the building and is conceived to predict its nonlinear dynamic response after a proper calibration based on the results of pushover analyses performed on a nonlinear FEM model. In spite of its simplicity, the proposed equivalent model provides, with a very low computational effort, an accurate representation of the nonlinear dynamic behaviour of the building comparable to that obtained through the more demanding nonlinear 3D FEM models. The effectiveness of the proposed simplified modelling approach is here validated by means of nonlinear dynamic analyses firstly performed on a benchmark known in the literature as SAC9 building, modelled as a plane steel frame structure and secondly on a three-dimensional reinforced concrete structure, designed according to old standard structural design rules. The very good agreement with the results obtained through accurate 3D FEM frame modelling, for different earthquake loadings, on the considered benchmarks provides a first validation of the proposed inelastic equivalent beam-like model and suggests its potential use for the seismic assessment of building structures. The low computational cost related to the beam-like model could be particularly advantageous for all the seismic vulnerability approaches requiring several nonlinear dynamic analyses, as those related to large scale applications, or those expressed in terms of probability of failure generally expressed in terms of fragility curves.
•Inelastic non-uniform beam-like model equivalent to multi-storey buildings.•The model is characterized by a very low computational cost.•It is capable to predict the non-linear dynamic response of an entire building.•The model is calibrated by means of FEM-based pushover analyses.•The model has been validated through comparisons with full 3D FEM models.
