Shear Wall Buildings Research Articles

Seismic vulnerability of pre-code reinforced concrete shear wall buildings in Romania

Prior to 1963, when the first earthquake design code was implemented in Romania, mid height (over 8 storeys) shear wall buildings were already being built in some of the major cities. These buildings have important structural weaknesses when assessed using the current regulations. An 11 storeys residential building in Bucharest built in 1962 is analysed. Results show that the building is extremely vulnerable on the longitudinal direction, where the lateral resisting system is composed by only two shear walls. If bending capacity is lacking mainly at the base of the building, shear strength deficiencies are present over the entire height of the building, due to a lack of shear reinforcement in the walls. An analysis of several possible strengthening solutions is made, and conclusions are drawn regarding the feasibility of these solutions.

Straightforward Prediction for Responses of the Concrete Shear Wall Buildings Subject to Ground Motions Using Machine Learning Algorithms

The prediction of responses of the reinforced concrete shear walls subject to strong ground motions is critical in designing, assessing, and deciding the recovery strategies. This study evaluates the ability of regression models and a hybrid technique (ANN-SA model), the artificial neural network (ANN), and Simulated Annealing (SA), to predict responses of the reinforced concrete shear walls subject to strong ground motions. To this end, four buildings (15, 20, 25, and 30-story) with concrete shear walls were analyzed in OpenSees.150 seismic records are used to generate a comprehensive database of input (characteristics of records) and output (responses). The maximum acceleration, maximum velocity, and earthquake characteristics are used as predictors. Different machine learning models are used, and the accuracy of the models in identifying the responses of the shear walls is compared. The sensitivity of input variables to the seismic demand model is investigated. It has been seen from the results that the ANN-SA model has reasonable accuracy in the prediction.

20 Katlı Betonarme Yapının Farklı Perde Duvar Yerleşimlerine Göre Deprem Analizi

Especially in recent years, there has been a marked increase in the construction of tall residential and commercial buildings. Due to this significant increase, the effects of lateral loads such as earthquake loads and the problems of providing sufficient strength and resistance against earthquakes have attracted much attention. Severe earthquakes could cause severe damage or collapse in tall buildings. Academic studies have shown that structural damage caused by the earthquake is the cause of the large displacement. Shear walls are a type of structural system that provides lateral resistance to a building or structure. With Shearwall systems, the lateral loads on the building are reduced by countering the effects of lateral loads on high buildings. Thus, the use of shearwalls in buildings could prevent large displacement and damage caused by this displacement. The aim of this study is to investigate the effects and behaviour of the shear walls, which have different placement, performance of the building under the earthquake loads. To the aim, a reinforced concrete structure with 20 stories have been modelled by SAP2000 V22 finite element program to conducted earthquake analysis of the structure.

Use of convolutional networks in the conceptual structural design of shear wall buildings layout

In the structural design of shear wall buildings, the initial process requires the interaction between the architecture and engineering teams to define the appropriate distribution of the walls, a stage typically carried out through a trial-and-error procedure, without any consideration of previous similar projects. In previous work, a database of 165 Chilean residential projects of reinforced shear wall concrete buildings was built, which fed a regressive neural network model to predict the wall’s engineering thickness and length values from an architectural 30-feature input vector, which accounts for geometric and topological properties, archiving remarkable results regarding the coefficient of determination (R2). However, a regressive model of this nature does not incorporate a spatial detail or contextual information of each wall’s perimeter, and also, the prediction of other parameters such as the wall translation has a poor performance. For this reason, the present research proposes a framework based on convolutional neural network (CNN) models to generate the final engineering floor plan by combining two independent floor plan predictions, considering the architectural data as input. The first plan prediction is assembled using two regressive models that predict the wall engineering values of the thickness, the length, the wall translation on both axes from the architectural plan, and the floor bounding box width and aspect ratio. The second plan prediction is assembled using a model that generates a likely image of each wall’s engineering floor plan. Both independently predicted plans are combined to lead the final engineering floor plan, which allows predicting the wall’s rectangles design parameters and propose new structural elements not present in architecture, making the methodology an excellent candidate to accelerate the building wall layout’s early conceptual design.

Structural design of reinforced concrete buildings based on deep neural networks

In shear wall building design, the initial process requires the interaction between the architectural and structural engineering groups to define the adequate wall layout, usually done with a trial-and-error procedure to fulfill architectural and engineering needs, slowing down the design process. For the engineering analysis, first, the wall thickness and length are required to check the building deformation limits, base shear strength, among other parameters. For this reason, the present investigation develops a structural design platform for reinforced concrete wall buildings that uses a deep neural network to predict the wall’s thickness and length based on previous architectural and engineering projects. The study includes, in the first place, the surveying of the architectural and engineering plans for a total of 165 buildings constructed in Chile; the generated database has the geometric and topological definition of the walls and the slabs. As a second stage, a model was trained for the regression of the wall segments’ thickness and length, making use of a feature vector that models the variation between the architectural and the engineering plans for a set of conditions such as the thickness, connectivity (vertical and horizontal), area, wall density, the distance between elements, wall angles, foundation soil type, among other engineering parameters. The regression model results in terms of R2-value are 0.995 and 0.994 for the predicted wall thickness and length, respectively, proving to be a reliable method for the initial engineering wall definition.

Damage and sensitivity analysis of a reinforced concrete wall building during the 2010, Chile earthquake

Buildings with Reinforced Concrete (RC) walls are commonly used to resist lateral forces in seismic countries because they provide high lateral stiffness and strength. In recent earthquakes, shear wall buildings have shown good behavior in general; however, a small percentage underwent severe damage localized typically in lower stories. Several numerical models have been developed and proposed to simulate the failure mechanism and behavior of RC walls. From the existing models, only those denoted as micro-models can accurately simulate the stress and strain distributions. The aim of this research is double: (i) to validate a nonlinear finite element wall model and the associated material stress-strain constitutive relationship using the behavior of a real building during the 2010 Chile earthquake; and (ii) to analyze the uncertainty of the response of the building due to changes in model parameters. To validate the response of the wall model, four experimental benchmark RC wall specimens were studied, and model accuracy was evaluated using five parameters: initial stiffness, peak base-shear, ultimate base-shear, maximum displacement, and dissipated energy. A sensitivity analysis was carried out to study the influence of material parameters in the wall response and its damage. The case-study is a 18-story building with 1 basement, which suffered severe damage during the 2010 Chile earthquake, which has been studied by non-linear response-history analysis. Uncertainty in the building response due to three important modeling assumptions was considered: Rayleigh’s damping model parameters; effective elastic bending stiffness of the structural elements; and effect of the vertical ground motion component. Results showed that the proposed model can predict the seismic response of the building with reasonable accuracy by identifying correctly the damage location. This case-study enabled us to assess also the effect of damping in non-ductile structures, the important influence of the slab stiffness in the response, and the effect of the vertical ground motion component in the sequence of damaged walls.

Multiscale Investigations of RC Shear Wall Buildings

ABSTRACT The precise description of reinforced concrete shear wall (RCSW) systems under severe dynamic loading remains a difficult research question owing to the intrinsically multi-scale underlying mechanisms, ranging from building’s irregularity to individual core walls, and even to the millimeter length-scales nonlinear shear over cracks and progressive steel bar buckling. This study adopted a parallel multiscale finite element analysis platform that can link the millimeter-level microphysical phenomena to the entire building-level dynamic responses in order to analyze weak pre-1980 buildings that lack modern codes such as boundary elements of walls. Results offer physically sound rationales behind the multi-scale damage behaviors.

Seismic Performance of Reinforced Concrete Shear Wall Buildings

Seismic Performance of Reinforced Concrete Shear Wall Buildings

Earthquake Performance Analysis of Existing Reinforced Concrete Structure in the Istanbul Metropolitan Area Using Non-Linear Method

Many people suffer loss of life and property due to the earthquake disaster in Turkey. In order to minimize this disaster, the resistance of the structures to earthquake should be determined under the light of studies done before. Turkey is in one of the most dangerous seismic regions in the World. As a sub plate between the large Eurasian, Arabian and African plates, Turkey rests on the Anatolian tectonic plate. Arabian plate in the direction of pushing Turkey to the North, the Anatolian plate moves in the opposite clockwise. However, it is prevented to move in the North direction due to the Eurasian plate. In this case, it contains many active faults and Turkey’s most populous city of Istanbul is in danger. In this study, it is aimed to perform a performance analysis according to the Turkey Building Earthquake Code 2018 in a six-story reinforced concrete shear wall-framed structure in Istanbul where active fault lines are located. This existing complex designed reinforced concrete building investigated in this study is in the city of ?stanbul, Turkey. This city is under danger of approaching and inevitable Great Istanbul Earthquake likely greater than Mw 7. The nonlinear seismic behavior of a complex reinforced concrete (RC) residential building is investigated by and linear and the static pushover. The selected reinforced concrete structure was designed according to 1998 version of Turkish Earthquake Code (TEC-1998). In the earthquake engineering, performance-based design method is used to determine the level of expected performance of the structures under the earthquake effect. According to the code, the reinforced concrete shear wall building is not expected to satisfy controlled damage (life safety) performance levels under design earthquake

Evaluating the shear resistance of deep beams loaded or supported by wide elements

It is common in concrete structures to encounter deep beams that are loaded or supported by wide elements such as shear walls in buildings and large piers in bridges. This type of boundary condition results in stress concentrations at the edges of the loading or supporting elements, and this in turn results in steep diagonal cracks and concentrated diagonal struts. In this study the shear strength of deep beams affected by stress concentrations is studied in detail with two methods: a two-parameter kinematic theory (2PKT) and a nonlinear finite element model (FEM) VecTor2, which is based on the Disturbed Stress Field Model and the Modified Compression Field Theory. It is shown that, with appropriate simple modifications to account for the loading or support conditions, as well as the dowel action of the longitudinal web reinforcement, the 2PKT captures well the shear strength of 10 test specimens from the literature. The average test-to-predicted ratio for the peak strength, as determined from the 2PKT, was 1.09 with a coefficient of variation of 8.69%. The average test-to-predicted ratio for the peak strength, as determined from the VecTor2 models, was 0.99 with a coefficient-of-variation of 5.27%. The VecTor2 models are also able to accurately capture the strain concentrations measured in the experiments. These FEM analyses and detailed experimental measurements assist in ultimately developing rational approaches, including kinematic and strut-and-tie methods, for evaluating deep beams with stress concentrations, as occurs in members with large loading or supporting elements.

Impacts of simulated M9 Cascadia Subduction Zone earthquakes considering amplifications due to the Georgia sedimentary basin on reinforced concrete shear wall buildings

AbstractSouthwest British Columbia has the potential to experience large‐magnitude earthquakes generated by the Cascadia Subduction Zone (CSZ). Buildings in Metro Vancouver are particularly vulnerable to these earthquakes because the region lies above the Georgia sedimentary basin, which can amplify the intensity of ground motions, particularly at medium‐to‐long periods. Earthquake design provisions in Canada neglect basin amplification and the consequences of accounting for these effects are uncertain. By leveraging a suite of physics‐based simulations of M9 CSZ earthquakes, we develop site‐specific and period‐dependent spectral acceleration basin amplification factors throughout Metro Vancouver. The M9 simulations, which explicitly account for basin amplification for periods greater than 1s, are benchmarked against the 2016 BC Hydro ground motion model (GMM), which neglects such effects. Outside the basin, empirical and simulated seismic hazard estimates are consistent. However, for sites within the basin and periods in the 1‐5 s range, GMMs significantly underestimate the hazard. The proposed basin amplification factors vary as a function of basin depth, reaching a geometric mean value as high as 4.5 at a 2‐s period, with respect to a reference site located just outside the basin. We evaluate the impact of the M9 simulations on tall reinforced concrete shear wall buildings, which are predominant in the region, by developing a suite of idealized structural systems that capture the strength and ductility intended by historical seismic design provisions in Canada. Ductility demands and collapse risk conditioned on the occurrence of the M9 simulations were found to exceed those associated with ground motion shaking intensities corresponding to the 975 and 2475‐year return periods, far exceeding the ∼500‐year return period of M9 CSZ earthquakes.

Regional seismic ground‐motion simulation and observation with engineering applications

Regional seismic ground‐motion simulation and observation with engineering applications

Influence of soil–structure interaction on the fundamental frequency of shear wall structures

Numerous studies indicate that soil–structure interaction has a great influence on the dynamic characteristic of buildings. This study presents an analysis of the effect of soil–structure interaction (SSI) on the natural frequency of shear wall building structures. The system is modeled by a 3D finite element model and using elastic discrete springs to represent the soil–structure interaction. A parametric study for different soil profiles is performed on one-storey building followed by a generalization on multi-storey buildings. Analysis of the results leads to the definition of the relative soil–structure parameter Kss for this type of structures. A multi-regression analysis allows to set up a dimensionless chart for the assessment of the fundamental frequency of shear wall building structures.

Experimental study on cyclic behavior of stiffened perforated steel shear panels

The use of steel shear walls in buildings has recently received much attention as a system resisting against lateral loads imposed by earthquakes. An opening in the steel shear wall may cause adverse effects on seismic behavior such as a decrease in strength, initial stiffness and energy dissipation capacity of the shear wall. Proper stiffeners can be installed around the openings to overcome these drawbacks. Seven steel shear panels with and without circular openings in the center of the panels with a diameter to width ratio of 20% and 35% with horizontal and vertical stiffeners recommended in the AISC 341-16 Regulation as well as diamond-shaped stiffener were tested under cyclic loading. The seismic parameters of the specimens, including strength, initial stiffness, ductility and energy dissipation, were determined using hysteresis diagrams obtained from experiments. Horizontal and vertical stiffeners improved the seismic performance of the shear panel appropriately. The specimens with diamond-shaped stiffeners showed an appropriate seismic performance before rupture on the plate in the vicinity of the lower corner of stiffener on the welded area during high loading cycles. Accordingly, the use of diamond-shaped stiffeners around the opening is not recommended in structural systems with high ductility demand.

Three-dimensional nonlinear response history analyses for earthquake damage assessment: A reinforced concrete wall building case study

Nonlinear dynamic analysis techniques have made significant progress in the last 20 years, providing powerful tools for assessing structural damage and potential building collapse mechanisms. The fact that several reinforced concrete shear wall residential buildings underwent severe structural damage in walls at the lower building levels during the 2010 Maule earthquake (Chile) presents a scientific opportunity to assess the predictive quality of these techniques. The objective of this research is to compare building responses using two completely different three-dimensional nonlinear dynamic models and study in detail the observed damage pattern and wall collapse of one reinforced concrete shear wall building in Santiago, Chile. The first model is a mixed fiber-shell model developed in MATLAB, and the second is a shell finite element model developed in the software DIANA. Results of both models are consistent with the hypothesis that high axial loads trigger a limited ductility failure in critical walls at roof-to-base drift ratios less than 0.34% with little capacity of hysteretic energy dissipation, which contradicts the ductile design philosophy of current code provisions.

Shear modulus analysis of cross-laminated timber using picture frame tests and finite element simulations

Determining the mechanical properties of cross-laminated timber (CLT) panels is an important issue. A property that is particularly important for CLT used as shear walls in buildings is the in-plane shear modulus. In this study, a method to determine the in-plane shear modulus of 3- and 5-layer CLT panels was developed based on picture frame tests and a correction factor evaluated from finite element simulations. The picture frame test is a biaxial test where a panel is simultaneously compressed and tensioned. Two different testing methods are simulated by finite elements: theoretical pure shear models as a reference cases and picture frame models to simulate the picture frame test setup. An equation for calculating the shear modulus from the measured shear stiffnesses in the picture frame tests is developed by comparisons between tests and finite element simulations of the CLT panels. The results show that pure shear conditions are achieved in the central region of the panels. No influence from the size of the tested panels is observed in the finite element simulations.

Estimating economic losses of midrise reinforced concrete shear wall buildings in sedimentary basins by combining empirical and simulated seismic hazard characterizations

SummaryStudies of recorded ground motions and simulations have shown that deep sedimentary basins can greatly increase the intensity of earthquake ground motions within a period range of approximately 1–4 s, but the economic impacts of basin effects are uncertain. This paper estimates key economic indicators of seismic performance, expressed in terms of earthquake‐induced repair costs, using empirical and simulated seismic hazard characterizations that account for the effects of basins. The methodology used is general, but the estimates are made for a series of eight‐ to 24‐story residential reinforced concrete shear wall archetype buildings in Seattle, WA, whose design neglects basin effects. All buildings are designed to comply with code‐minimum requirements (i.e., reference archetypes), as well as a series of design enhancements, which include (a) increasing design forces, (b) decreasing drift limits, and (c) a combination of these strategies. As an additional reference point, a performance‐based design is also assessed. The performance of the archetype buildings is evaluated for the seismic hazard level in Seattle according to the 2018 National Seismic Hazard Model (2018 NSHM), which explicitly considers basin effects. Inclusion of basin effects results in an average threefold increase in annualized losses for all archetypes. Incorporating physics‐based ground motion simulations to represent the large‐magnitude Cascadia subduction interface earthquake contribution to the hazard results in a further increase of 22% relative to the 2018 NSHM. The most effective of the design strategies considered combines a 25% increase in strength with a reduction in drift limits to 1.5%.

Spectrum-based pushover analysis for the quick seismic demand estimation of reinforced concrete shear walls

In the design of medium- and high-rise buildings, the reinforced concrete (RC) shear wall structure is widely used to resist seismic loading. Thus, accurately predicting the seismic demand of this structural form becomes particularly important. However, existing multi-mode pushover analysis methods are mainly applied to predicting seismic demands of frame structures, while few attentions have been paid on other structural forms. In this paper, by revising the equation for predicting the overall roof displacement, the spectrum-based pushover analysis (SPA) of RC shear wall structures for the fast prediction of the seismic demand is presented. The accuracy of the SPA method in the fast prediction of seismic demands of RC shear wall structures was investigated through a case study on two representative RC shear wall buildings. The impact of the input ground motions (IGM) scaling target spectra on the accuracy of the SPA method was studied by selecting and scaling IGMs with the target spectra being the ASCE design spectra and conditional mean spectra. Seismic demands computed by the SPA method, the nonlinear response time history analysis (NLRHA), and the other two advanced methods of multi-mode pushover analysis were compared. It is indicated from the comparison of the seismic demands that the SPA method predicted seismic demands of RC shear wall structures with outstanding and consistent accuracy. Therefore, the SPA method can be considered as a solution for the fast seismic demand prediction of RC shear wall structures for different regions, where different target spectra are used as the seismic intensity representatives.

Material Quantities of Reinforced Masonry versus Reinforced Concrete Shear Walls

Shear wall system is a common seismic force resisting system that is used for both reinforced masonry (RM) and reinforced concrete (RC) buildings. RM shear walls can provide a considerable level of ductility like RC walls, especially for walls with boundary elements. The latest provisions of the Canadian Standard for Masonry allowed a higher level of ductility for RM shear walls based on their ductile response. This paper aims to estimate the quantities of construction materials required for RM shear walls compared to those of RC walls. Three multi-storey RM shear wall buildings with different heights located in three different cities in Canada were selected. 5-, 10-, and 15-storey buildings were located in Toronto, Montreal, and Vancouver cities which represent three different levels of seismic hazard. For each building’s height and location, the RM shear walls were designed with the level of ductility that results in the least construction material quantities. The analysis and design procedures were repeated for each case when RC material was used. The amount of construction materials used for the shear walls of each building was evaluated for both RM and RC cases and they were compared. Moreover, the cost of labour and temporary works for RM and RC shear walls was estimated and compared. The comparisons showed that RM shear wall construction can be as economic as the RC one for different walls’ ductility levels.

Fragility curve modifiers for reinforced concrete dual buildings, including nonlinear site effects and soil–structure interaction

We investigate the influence of soil–structure interaction (SSI) and nonlinear soil behavior on the seismic fragility of reinforced concrete (RC) dual (frame + shear wall) buildings resting on shallow foundations. This article includes a holistic methodology to account for nonlinear soil behavior and soil–foundation–structure interaction in a modular way. Using nonlinear dynamic analyses, we derive fragility curves for a wide set of building typologies and soil profiles, showing that soil behavior during strong shaking significantly affects the vulnerability of the soil–foundation–structure system. The influence of SSI is pronounced mostly for soft soil profiles, varying in a building-specific way. Post-processing of our results evolves into a set of fragility modifiers that enable risk analysts to massively account for soil-related and/or SSI effects in large-scale risk assessments.