Nonlinear Analysis Procedure Research Articles

Comparison of seismic assessment guidelines using a case study reinforced concrete wall building

There are several seismic assessment standards and guidelines available around the world that can be used to identify vulnerable buildings. The assessment procedures and criteria in these documents are different, and thus, the assessment outcomes for a particular building, if assessed using different standards, can also be different. In this study, provisions of the linear static and non-linear static analysis procedures of three prominent seismic assessment documents, the American Society of Civil Engineers /Structural Engineers Institute standard ASCE 41 (2017) [1], the New Zealand Seismic Assessment Guidelines (2017) [2], and the European Standard EN 1998-3 (2005) [3] (also known as Eurocode 8 Part-3 or EC8-3) are discussed and compared, highlighting some of their similarities and differences. A reinforced concrete (RC) wall building used in FEMA P-2006 (2018) [4] for demonstration of ASCE 41 provisions is taken as the case study building for comparison of the assessment provisions. The linear and non-linear static analysis procedures specified in the three documents are applied to the case study building and the assessment outcomes are compared. The assessment results are found to vary across the analysis methods and guidelines. However, the critical governing vulnerability for the building is found to be the same. It is observed that with the simplifying modelling assumptions, coupled with the inherent conservatism in the assessment using linear static analysis, a more conservative outcome is obtained using the linear static methods as compared to the non-linear static methods. Overall, EC8-3 provisions are found to be the most conservative of all three guidelines considered for the assessment of the example building.

Propagation of Modelling Uncertainties for Seismic Risk Assessment: The Effect of Sampling Techniques on Low-Rise Non-Ductile RC Frames

ABSTRACT Quantifying the impact of modelling uncertainty on seismic performance assessment of existing buildings is non-trivial when considering the partial information available on material properties, construction details, and the uncertainty in the capacity models. This task is further complicated when uncertainty related to ground motion representation is considered. To address this issue, record-to-record variability, uncertainties in structural model parameters, and fragility model parameters due to limited sample size are propagated herein by employing a nonlinear dynamic analysis procedure based on recorded ground motions. A one-to-one sampling approach is adopted in which each recorded ground motion is paired up with a different structural model realization. Uncertainty propagation is explored by measuring the impact of different sampling techniques, such as Monte Carlo simulation with standard random sampling and Latin Hypercube sampling (with Simulated Annealing) in the presence of three alternative nonlinear dynamic analysis procedures: Incremental Dynamic Analysis (IDA), Modified Cloud Analysis (MCA), and Cloud to IDA (a highly efficient IDA-like procedure). This is all illustrated through application to an existing reinforced-concrete school building in southern Italy. It is shown that with a small subset of records, both MCA and Cloud to IDA can provide reliable structural fragility (and risk) estimates for three considered limit states, comparable to the results of more resource-intensive schemes.

Thick-shell finite element analysis of reinforced concrete flat plates with non-uniform connection stresses

This paper presents the application of a thick-shell nonlinear finite element analysis procedure to estimate the punching shear resisting performance of reinforced concrete slab-column connections under variable connection shear stress conditions. In the analyses performed, varied connection shear stress conditions stem from slabs being supported by columns with different cross-section aspect ratios, being subjected to different distributions of gravity loading, being constructed with different planar reinforcement ratios in orthogonal directions, as well as the application of unbalanced bending moments. Forty-eight isolated slab-column connection specimens presented in the literature were modelled and analyzed using a thick-shell finite analysis procedure. All numerical results were developed using a predefined set of material models and analysis parameters, a consistent meshing procedure, and are shown to provide meaningful agreement with experimental data without the need for case-specific model calibration or the adoption of specialised failure criteria. The results show that thick-shell modelling methods can be suitable for estimating the punching shear response of slabs subjected to non-uniform shear stress development in connection regions, and can provide similar levels of precision to that obtained for the analysis of idealised slab-column connections typically used for design procedure and model development.

A critical assessment of the design displacements of friction pendulum systems

The equivalent linear static procedure suggested in seismic codes for determining the maximum displacements of seismic isolation systems is evaluated comprehensively for friction pendulum isolators with respect to the benchmark nonlinear response history analysis procedure for a set of radii of curvature and coefficients of friction. A large set of selected and scaled near field ground motions recorded on stiff and soft soils are employed in comparative evaluations. It has been observed that equivalent linear static procedure significantly overestimates the maximum isolator displacements for all practical combinations of radius of curvature and friction coefficient. Overestimation is larger for ground motions on soft soils. Alternatively, a practical description of inelastic displacement spectra is introduced where the hazard is defined in terms of the 1-second spectral acceleration accounting for the seismicity and soil class of the site, and friction pendulum isolation systems are characterized by their radius of curvature and nominal friction coefficient. Employing the proposed design spectra in design and production may lead to significant reductions of the isolator sizes. Moreover, realistic estimation of maximum isolator displacements also leads to realistic estimation of isolator stiffness, as well as the internal design forces of both the isolation system and the superstructure through response spectrum analysis under design spectrum.

Prediction of nonlinear seismic demand of inter-story isolated systems using improved multi-modal pushover analysis procedures

The engineering community requires a simple and engineering-friendly procedure to evaluate the seismic performance of inter-story isolated structures (IIS), considering the widespread application of IIS and the limitations of current static nonlinear analysis procedures. This paper proposes an improved multi-modal pushover analysis procedure (IMMPA) that is compatible with the code design spectrum and can account for the effects of higher mode responses and the strongly nonlinear nature of IIS. Nonlinear response history analysis (NRHA) is unnecessary for a reliable assessment of IIS seismic performance when IMMPA is utilized. The IMMPA involves converting the IIS into a linear non-proportional damping structure to satisfy performance requirements, decoupling it into modal oscillators with the equivalent of the nonlinear structure in the modal coordinates using complex-mode-superposition approaches, adjusting the input response spectrum excitation with its equivalent parameters, and converting the response spectrum excitation into the demand spectrum. The main modal oscillators are identified by the complex modal participation mass ratio; the respective acceleration is used as the weight factor of the lateral pushing force; and the capacity spectrum procedure is employed to determine the performance point. Combining the main modal responses using a complex-mode superposition complete square combination rule (CCQC) produces an effective nonlinear peak response. Finally, the IMMPA procedure is demonstrated using an IIS example and evaluated with NRHA data. The evaluation demonstrated that the IMMPA procedure can overcome conventional pushover limitations and efficiently evaluate IIS seismic requirements.

Nonlinear analysis procedures for safety assessment of existing RC bridges under traffic loads

AbstractThe Italian infrastructural asset, mainly consisting of RC bridges, is affected by significant obsolescence: many bridges overpassed their theoretical nominal life and did not experience any maintenance intervention. Such a critical scenario is even worse if it is additionally considered the increase of vehicular traffic that occurred in the last decades. From a management point of view, many structures needed restrictions on use due to their inadequacy to withstand the traffic load provided by the current codes. This is a direct consequence of accurate safety assessments of such structures. In this paper, the opportunity to adopt nonlinear analyses for the safety assessment of existing RC bridges is discussed. The safety‐format proposed in EuroCode 2 for designing new RC bridges and based on nonlinear analysis methodology is critically reviewed to consider its possible application to existing bridges. Then, the estimation of modelling uncertainty is proposed to define some acceptance criteria for the specific numerical solution strategy to be used, following the most recent international research outputs. Finally, a case study is addressed with the aim to compare linear and nonlinear results, the latter based on a calibration and verification of the adopted modelling strategy.

Nonlinear Dynamic Analyses Utilising Macro-Models of Reinforced Concrete Building Structures and Site-Specific Accelerograms

This paper aims to guide structural engineers on how to apply the rapid nonlinear time history analysis (RNLTHA) procedure effectively to predict seismic demand, taking into account ductility and overstrength, and effects of dynamic phenomena including cyclic degradation of strength and stiffness in structures, in a direct and expedient manner. The shortcoming of the conventional force-based approach of design involving the use of a force reduction factor to account for nonlinear effects is well recognised. Nonlinear static (pushover) analysis and dynamic nonlinear time history analysis (NLTHA) are offered as alternative methods of analysis by major codes of practices to achieve better optimisation in the use of materials. NLTHA has advantages over pushover analysis in being more direct and capable of capturing cyclic response behaviour. Despite the merits of NLTHA, its adoption in the industry has been limited, mainly because of the complexity and the higher analysis cost involved. RNLTHA proposed in this article uses a macroscopic model of the building to fulfil the purpose of NLTHA, whilst saving computational time and achieving a good degree of accuracy, as verified by comparison with results generated from SeismoStruct.

FEM education in undergraduate studies: Industry‐informed research

AbstractRecent mechanical engineering graduates are expected to utilize Finite Element Analysis (FEA) in structural and machine design activities. However, after decades of implementation in engineering schools, the Finite Element Method (FEM) still challenges instructors and course designers. To align learning outcomes with industrial requirements, this article analyzes the opinions of Mexican industrial and academic experts about four important aspects of FEM education. The results suggest that specialists agree on the importance of including a mixture of theoretical and applied topics in the syllabus but prefer practical skills over fundamental concepts. Besides learning from defeaturing to postprocessing a model, engineering students must know how to plan, verify, and validate their finite element studies. Experts expect early design engineers to be proficient with Computer‐Aided Design (CAD) and have relevant mathematical and programming skills. Instead of using specialized software, students' first exposure to FEM may be based on FEA tools embedded in CAD systems. Also, academic and industrial respondents request the incorporation of modal, thermal and nonlinear analysis procedures in the course timetable. Finally, the statistical analysis shows that the two types of respondents share one common vision about the importance of the aspects under study. The findings from this work are useful for the design of FEM‐related coursework and can be used to guide course instructors about the right balance of theory and practice, overall course contents, and the selection of the software utilized for the practical part of the program.

Liquefaction behavior evaluation of a multi-layered site with fines-dominated soils

Characterization of liquefaction response in terms of triggering and manifestation at sites with soils containing significant amounts of fines is critically important. Saturated fines-dominated soils, that are known as liquefaction-susceptible materials, would represent a range of extreme responses to earthquake excitations from cyclic mobility to cyclic liquefaction causing excessive displacements. In a multi-layered soil profile, the interaction of adjacent layers in porewater pressure redistribution along the site profile plays an important role in liquefaction response. In this study, an advanced Nonlinear Dynamic Analysis (NDA) procedure in predicting the liquefaction mechanism and manifestation at a site with multiple fines-dominated soil layers is presented. The procedure specifically aims at simulating the interactions in a multi-layered system containing both sand-like and clay-like materials. The liquefaction data recorded by Wildlife Liquefaction Array (WLA) in 1987 Superstition Hills Earthquake (M = 6.6) was deployed to validate the NDA procedure. WLA site consists of sandy silt, silty sand, clayey silt, silty clay, and silt deposits in its upper 20 m and has provided invaluable records of porewater pressure and ground motions. Two critical-state-based constitutive models, PM4Silt and PM4Sand, in a coupled dynamic-fluid finite difference platform were employed. Calibration of the constitutive models was conducted using Cyclic Direct Simple Shear (DSS) test single-element modeling. The simulated response of the site from the proposed approach was compared with those of other NDA procedures conducted on this case history in terms of liquefaction parameters such as excess porewater pressure ratio and maximum shear strain. These comparisons revealed that incorporating multi-layer effects in an advanced NDA procedure can enhance the liquefaction behavior predictions at sites with fines-dominated materials.

Novel Plastic Hinge Element for Seismic Performance Assessment of RC Bridge Columns with Lap Splices

This paper presents a nonlinear analysis procedure for evaluating the seismic performance of reinforced concrete (RC) bridge columns with lap splices using a novel plastic hinge element considering shear deformation. To accurately assess the inelastic behavior of RC bridge columns, reliable three-dimensional (3D) constitutive models are required. However, developing a 3D nonlinear material model is difficult and computationally intensive. In this study, to address these issues, a new plastic hinge element considering shear deformation for RC bridge columns is developed. The new plastic hinge element is based on the Timoshenko beam theory and utilizes two-noded zero length element with six degrees of freedom. The finite element model was implemented in a computer program named Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST) developed by the authors. The developed plastic hinge element for seismic performance assessment of RC bridge columns with lap splices was validated through comparison of the numerical and experimental results.

Punching shear code provisions examination against the creation of an opening in existed RC flat slab of various sizes and locations

Punching shear is a critical problem in flat slabs directly supported at columns resulting in a high-stress concentration area, increasing the probability of brittle punching shear failure. However, the capacity is reduced by creating an opening that affects the overall behavior of the slab based on its size and location with respect to the loaded area. Furthermore, the design and analysis of the various structural elements are based on international regulations that have major differences in their basis and executions. In this study, the different code provisions in punching shear of RC two-way flat slab without shear reinforcement are examined under various opening sizes and locations using the Nonlinear Finite Element Analysis (NLFEA) procedure using ABAQUS software. A total of twenty-one model has been simulated for examining the prediction accuracy by the ACI318-19, MC2010, and EC2 under the effect of opening size (100, 200, and 300) mm, and locations (zero, 0.25d, 0.50d, 2.0d, 4.0 h, 5.5d, and 6.0d) under two main categories; the critical punching perimeter, and the critical opening location. However, it has been revealed that the proposed value of 0.50d as the critical punching perimeter is the most reliable one; besides, the value of 4 h is enough for defining the position where the effect of an opening could be neglected regardless of its size. Furthermore, it has been found that the column-to-opening ratio (C/O) is a very significant factor in controlling the punching shear capacity prediction accuracy by the different codes. Predictions get more overestimated under larger (C/O) values where increasing the C/O ratio by half increases the ultimate deflection percentage by an average of 22 %, except for those with smaller C/O values of less than 0.5, where it only reaches a maximum value of 13 %. Moreover, code prediction of the ACI318-19 and the MC2010 was found to be overestimated in all cases. In contrast, the EC2 was underestimated with an accurate prediction for an opening location of 2.0d from the column's face. However, it has been found that ACI318-19 is the most accurate one regarding the critical punching perimeter (0.5d) and critical opening location (4.0d).

Dynamic Modal Analyses of Building Structures Employing Site-Specific Response Spectra Versus Code Response Spectrum Models

This paper is aimed at giving structural designers guidance on how to make use of elastic site-specific response spectra for the dynamic modal analysis of a structure in support of its structural design. The use of response spectra in support of the pushover analysis of an RC building forming part of the non-linear static analysis procedure (that can be used to predict seismic demand without relying on the code-stipulated default R factor) is also presented. Seismic analysis of structures based on the use of site-specific response spectra can help to achieve a more optimised, and cost-effective, structural design compared to the conventional approach employing a response spectrum model stipulated by the code for different site classes. Currently, the methodology is only adopted in major projects in which enough resources are available to engage experts who are skilled in operating the procedure; thus, the use of site-specific response spectra in structural engineering practice is still limited despite the merits of the procedure. Deriving a site-specific response spectrum requires a database of representative ground motion records to be developed. Extra analytical tasks to be undertaken include the processing of bore log data, site response analyses, and selection/scaling of bedrock accelerograms for input into site response analyses. Guidelines for implementing this design methodology are currently lacking. To promote the wide adoption of site-specific seismic design, this article presents the procedure for developing the required site-specific design spectra, as well as guidelines for applying these spectra for seismic design based on analyses of linear, or nonlinear, models of the building. Non-linear analysis can be accomplished by dealing with macroscopic models as illustrated in a case study.

A new automatic procedure for nonlinear analysis of masonry arches subjected to large support movements

To predict the settlement and the collapse mechanisms of masonry arch structures caused by largely moving supports and the value of the support movement leading to collapse, an automatic procedure based on the use of Somigliana’s distortions is proposed. The proposed procedure is an incremental method that computes the inner forces at the joints of the arch, composed of rigid blocks and deformable mortar joints, at each increase of the support movement. Somigliana’s distortions are introduced at the joints to nullify the inadmissible forces, basically the tensile ones, and to restore material continuity at the cracked joints (equilibrium and congruence). The Somigliana distortions method allows for material and geometric nonlinear analysis, avoiding updating the stiffness matrix. The strength and robustness of the procedure are ascertained by analyzing case studies from the literature. The results are consistent with experimental and numerical outcomes provided by other authors.

Nonlinear modelling parameters and acceptance criteria in ASCE/SEI 41: a critical review and applicability to Canada

The National Research Council Canada is currently developing seismic evaluation and upgrading guidelines (SEG) for existing buildings in Canada. The SEG consist of both linear and nonlinear analysis procedures to evaluate the seismic adequacy of existing buildings. Where nonlinear analysis procedures are selected, nonlinear modelling parameters (NMP) and acceptance criteria (AC) are to be used. Due to the lack of Canadian guidelines for nonlinear analyses, the state of the practice in Canada often refers to ASCE/SEI 41 for guidance. Given the differences in seismic design and construction practices in the United States and Canada, ASCE/SEI 41 should be used with caution. This technical note presents a critical review of NMP and AC in ASCE/SEI 41 and recommends key steps for the investigation of the applicability of NMP and AC in ASCE/SEI 41 to the Canadian context. An example is included to demonstrate the recommended steps and the importance of such investigation.

Evaluation of progressive collapse behavior in reinforced concrete buildings

Progressive collapse is a catastrophic chain reaction of failure of a structure that is caused due to loss of vertical load bearing element of the structure, resulting damage of a part of the structure or entire structure. In our research work 10 storey regular Reinforced Concrete framed structure is considered and is seismically designed with IS 1893:2016 in SAP2000 version 20 modeling. The different column removal scenarios both in plan and elevation suggested by guidelines were examined by alternate load path method using nonlinear staged construction available in the software and then identify the potential of the structure to withstand progressive collapse. Numerical results were compared by analyzing columns and beams separately by calculating demand capacity ratios and the requirement of percentage of steel for failed structural elements are predicted both in flexure and shear stresses. Our objective is to provide clear conceptual step-by-step descriptions of various procedures for progressive collapse analysis 3D (three-dimensional) Finite Element Methods (FEM) and non-linear static push-down analysis in SAP2000 software was used to assess the progressive collapse potential of a typical gravity-load designed mid-rise reinforced concrete building with open ground floor. The beam is actually designed to resist the shear force up to 39.84 kN. So in order to resist the shear failure we need to provide enough vertical reinforcement. The failed structural elements were re-designed to resist progressive collapse in order to satisfy the acceptance criteria recommended by the guidelines. It’s showed that the incorporation of perimeter beams in buildings improved the progressive collapse resistance as it reduces joint displacement and chord rotation at column removal locations by providing sufficient stiffness and load paths for increased gravity loads. The study results can be used to develop and calibrate the nonlinear numerical model for analyzing high-rise building progressive collapse behavior and can help provide information that may improve new and existing reinforced concrete core-wall building robustness against progressive collapse.

An Integrated Test-Based Nonlinear Aeroelastic Analysis Method to Freeplay-Induced Limit-Cycle Oscillations

The nonlinear limit-cycle oscillations induced by aileron rotational freeplay are investigated by numerical simulation and flutter wind tunnel tests. An integrated nonlinear aeroelastic analysis method and procedure based on the nonlinear system identification technology is proposed. Based on the characteristics of the structure, a low-speed nonlinear flutter wing-aileron model that considers both the linear flutter test and the nonlinear limit-cycle oscillation test with aileron rotational freeplay is designed. The wind tunnel tests are conducted with the model, and the stable limit-cycle oscillation is observed by accelerometers under the linear flutter boundary with a 0° angle of attack. Higher-order harmonic vibration is also observed with a low proportion compared to the fundamental oscillation, and the limit-cycle oscillation grows gradually with the increase of airspeed until flutter occurs. The comparison of numerical and experimental investigation shows high consistency.

Estimation of extreme rainfall quantiles at ungauged sites in the Loess Plateau, China by regional frequency analysis

AbstractAn increase in the frequency of extreme rainfall events has caused more severe floods than before under the influence of climate change, and is receiving a lot of attention in data‐scarce areas like the Loess Plateau, especially in some small basins without hydrometeorological data, and to avert the risk of disaster needs the estimation of extreme rainfall quantiles. In this study, generalized additive models (GAM) are combined with a nonlinear canonical correlation analysis (NLCCA) procedure to estimate extreme rainfall quantiles at ungauged sites in the Wei River basin on the Loess Plateau. Also, the single inverse distance weighting (IDW) interpolation, NLCCA‐backpropagation (BP), and NLCCA‐radial basis function (RBF) models were used as comparative methods for testing the efficiency of the NLCCA‐GAM model. Because meteorological data are generally lacking in rainfall‐ungauged basins, data at ungauged sites was interpolated by IDW interpolation when NLCCA delineated homogeneous regions. Results of validation indicated that maximum daily rainfall quantiles in the Loess Plateau were well estimated by NLCCA‐GAM‐based regional frequency analysis, implying the NLCCA‐GAM is a useful tool for estimating design extreme rainfall in ungauged basins. Results of comparison demonstrated that NLCCA‐GAM was more robust and better reflected the nonlinear relationship between explanatory and response variables in the region than did comparative approaches. In addition, it was found that the NLCCA‐GAM approach made full use of the data from sites in homogeneous regions to mine the valuable nonlinear correlation between ungauged and gauged sites and estimate extreme rainfall quantiles at ungauged sites.

Seismic performance and design of the damped-outrigger system incorporating buckling-restrained brace for buildings with various heights

The keen purpose of this study is to investigate the seismic performance of buildings equipped with damped-outrigger system using the buckling-restrained brace (BRB) system (BRB-outrigger) and to propose the optimal design recommendation for buildings with a different height. The numerical models with building heights of 72, 144, 216 and 288 m, each contains two layers of BRB-outrigger and a 40 m by 40 m structural plan are analyzed using response spectral analysis (RSA) and nonlinear response history analysis (NLRHA) procedures. To get more closer to the actual reality, the member-by-member benchmark models are designed based on the seismic code requirement. In the response spectral analysis procedure, the equivalent damping ratio is computed in order to include the BRB’s inelastic response. For the main purpose of parametric study, a simplified model which will be using a Timoshenko beamcolumn element in order to capture shear-type to flexural-type lateral deformation for a lower to higher raising buildings are proposed. The dimensionless parameters that actually describe the relationships between the core structure stiffness, outrigger flexural stiffness, the axial stiffness of BRB and perimeter column in the parameter study are considered based on practical design and allowable structural sections. The optimization targets include the maximum roof drift, inter-story drift ratio, core structure base shear, core structure overturning moment and the BRB energy dissipation performance. Based on the analyzed result, the ranges of optimal design parameters vary in the different optimization targets and building heights. This study concludes with a design recommendation for building equipped with BRB-outrigger system with different building heights.

Seismic Vulnerability Assessment of Building For Retrofitting Strategies: Simplified Vulnerability Assessment

In India, 85% of existing buildings are unreinforced masonry and 5-7% are reinforced concrete and 5-7% are traditional buildings. And most buildings do not qualify to resist earthquakes, technically it can be said that they would not be able to resist earthquake loads. In the past, it is seen at the time of the earthquake, millions of lives and the economy of that region is affected. Demolition of ageing building mass is not only harmful to the environment but also it is not viable economically to rebuild all vulnerable buildings. Such buildings are recommended to be retrofitted. Recent earthquakes have demonstrated the need to identify and improve the performance of the existing seismic deficient buildings. For this reason, Seismic vulnerability assessment is considered a part of a better strategy to mitigate the risk and improve the resiliency of the country and its infrastructure. Due to the high volume of building archetypes in our country, for Seismic Vulnerability Assessment at a huge scale, a rapid, simplified method is being adopted that can facilitate the assessment procedure in a lesser computational time period. This paper was primarily engrossed in the analysis of some simplified methods proposed in the literature for assessing the simplified seismic vulnerability. A hypothetical building is analyzed using structural software (Etabs) by Nonlinear Dynamic Analysis Procedure. Using Etabs software, various structural parameters like Story Response Drift, Displacement (max) and Base Shear are considered and discussed. By proper interpretation of the result, a suitable measure to minimize vulnerability and ensure sustainability and cost-effectiveness, retrofitting strategies is recommended. Keywords: Seismic vulnerability, Existing Building, Simplified Analytical Method, Rapid Visual Screening, Detailed vulnerability assessment, Etabs, Non-linear Dynamic Analysis, Retrofitting Strategies

Influence of the P-delta Effect and Stiffness Irregularity on the Structural Behavior of Reinforced Concrete Buildings

In this research, the influence of the stiffness irregularity and the p-delta effect on the structural behavior of a reinforced concrete building is analyzed. The main objective is to determine the impact of the stiffness irregularity and the p-delta effect on the structural behavior in regular and irregular buildings. First, the linear dynamic analysis procedure is performed in order to determine the structural response in terms of drifts, shear force and moments per floor. Subsequently, we proceed with the nonlinear static analysis procedure to obtain the capacity curve of the structure. The post elastic stiffness and the overall ductility of the structure are determined from the capacity curve. Finally, a comparative analysis of the responses from the linear and nonlinear analysis is carried out to determine the percentage variation of the results. When analyzing the structures that consider the stiffness irregularity and the p-delta effect, variations of up to 16.50%, 11.00% and 14.00% have been obtained in drifts, shear force and moments per floor respectively, which are considerable values. When the p-delta effect is considered in structures with the presence of stiffness irregularity, there is a variation in stiffness of up to 59.85%. With this result it is explained that the p-delta effect produces a greater degradation of the overall stiffness of the structure.