Nonlinear Time Domain Analysis Research Articles

Wind-Induced Dynamic Response of Inter-Story Isolated Tall Buildings with Friction Pendulum Bearing Based on an Enhanced Simplified Model

Isolation technology, especially for base isolation, is increasingly being applied in earthquake-prone areas. To satisfy some special demands (such as prevention from seawater erosion of an isolation layer, story-adding retrofit of existing buildings, avoidance of collision between base-isolated tall buildings, and so on), the isolation layer sometimes has to be set in the middle of a building to constitute inter-story isolated buildings. This special structural form inevitably encounters strong wind loads during service life, and its wind-resistant performance deserves to be investigated. This study conducts the wind-induced vibration analysis of inter-story isolated tall buildings with friction pendulum bearing (FPB). The nonlinear time domain analysis model and statistical linearization method to compute the wind-induced response of FPB inter-story isolated tall buildings are addressed based on an enhanced simplified model. Considering the independence of the upper and lower structures, two structural design schemes for inter-story isolated tall buildings are provided. Their dynamic characteristics are analyzed, and wind-induced responses are compared. Finally, the accuracy of the statistical linearization method is verified. This study provides an important theoretical basis for the structural design and wind resistance of inter-story isolated tall buildings.

A semi-analytical time-domain model with explicit fluid force expressions for fluidelastic vibration of a tube array in crossflow

It is widely acknowledged that fluidelastic instability (FEI), among other mechanisms, is of the greatest concern in the flow-induced vibration (FIV) of tube bundles in steam generators and heat exchangers. A range of theoretical models have been developed for FEI analysis, and, in addition to the earliest semi-empirical Connors' model, the unsteady model, the quasi-steady model and the semi-analytical model are believed to be three advanced models predominant in the literature. The unsteady and the quasi-static models share the merits of having explicit fluid force expressions and ease of being implemented but require more experimental inputs, whereas the semi-analytical model requires fewer parameters due to its analytical nature but is hard, if not prohibitive, to derive explicit fluid force expressions. Since the fluid force formulations set in the core of development of FEI models, the understanding and in particular the implementation of the semi-analytical model has been impaired by the nonexistence of explicit fluid force expression. This issue becomes more profound in time-domain analysis whereby the simple harmonic assumption is discarded. Here we report a new semi-analytical time-domain (SATD) FEI model with explicit fluid force expressions. The new model allows a consistent frequency-domain stability analysis and more importantly a truly time-domain response analysis. The theory was validated by calculating linear stability thresholds of two typical tube array patterns and comparing against reported experimental data. We then present a nonlinear time-domain analysis of a single loosely-supported tube with piece-wise linear stiffness. The nonlinear and nonsmooth dynamics was probed in details by utilizing various techniques, playing an emphasis on characterizing and distinguishing the chaotic vibration. We found that the system follows a quasi-periodic route to chaos. Such an in-depth study of the nonlinear dynamics of tubes in crossflow has never been reported in the context of SATD model. Our results enrich the theory and provide a different approach for linear and nonlinear dynamics of tube bundles, which are essential for the subsequent fretting wear analysis.

Nonlinear time-domain soil-structure interaction analysis of a mid-rise building benchmarked against earthquake recordings: A case study of the BRI's annex building

Performing soil-structure interaction (SSI) analysis under strong shaking scenarios using the direct method is becoming more prevalent in engineering practice. However, given the pronounced nonlinearity in soil, structure, and foundation response, the robustness of current methodologies is open to question, and benchmarking these methodologies against instrumented case histories is needed to identify the strengths and weaknesses in the approach. In this study, a three-dimensional (3D) Nonlinear (NL) Soil-Structure Interaction (SSI) analysis methodology in the time-domain code LS-DYNA is benchmarked against the actual recordings for a mid-rise building. The well-instrumented Building Research Institute (BRI) Annex Building (ANX) in Tsukuba City northeast of Tokyo, Japan, which features an adjacent free-field geotechnical downhole array, is used for this case study. A Finite Element (FE) three-dimensional 3D SSI model of the site, including the BRI ANX building, that considers both material and geometric nonlinearities is first developed. Two events are applied to the model: the 2011 Tohoku-Oki earthquake main shock (Mw9.1), referred to as the Great East Japan Earthquake (GEJE), and the 2002 Southern Ibaraki Prefecture earthquake (Mw4.9), selected from the BRI strong motion network due to the relatively wide amplitudes recorded at the site. The former event induced maximum shear strains in the soil of 1.6%, while the latter event induced maximum shear strains of 0.08%. For both horizontal and vertical components of shakings, the predicted response of the structure and adjacent free-field downhole array are compared with the corresponding recordings. The results show that the structural response is significantly affected by the accuracy of the predicted free-field ground surface response, especially at the structural fundamental period as opposed to the site period. In addition, results indicate that the fixed-base and flexible-base structural models’ responses are substantially different, mainly attributed to the SSI effects that cannot be captured in the fixed-base model. Finally, a comprehensive discussion on the minimum amount of data required to adequately capture nonlinear structural response using the proposed SSI methodology is provided in this case study.

Τhe Behavior of Hybrid Reinforced Concrete-Steel Buildings under Sequential Ground Excitations

In common construction practice, various examples can be found involving a building type consisting of a lower, older, reinforced concrete structure and a more recent upper steel part, forming a so-called “hybrid” building. Conventional seismic design rules give full guidelines for the earthquake design of buildings constructed with the same material throughout. The current seismic codes neglect to provide specific design and detailing guidelines for vertical hybrid buildings and limited existing research is available in the literature, thus leaving a scientific gap that needs to be investigated. In the present work, an effort is made to fill this gap in the knowledge about the behavior of this hybrid building type in sequential earthquakes, which are found in the literature to burden the seismic structural response. Three-dimensional models of hybrid reinforced concrete–steel frames are exposed to sequential ground excitations in horizontal and vertical directions while considering the elastoplastic behavior of these structural elements in the time domain. The lower reinforced concrete parts of the hybrid buildings are detailed here as corresponding to a former structure by a simple approximation. In addition, two boundary connections of the structural steel part upon the r/c part are distinguished for examination in the elastoplastic analyses. Comparisons of the arithmetical analysis results of the hybrid frames for the examined connections are carried out. The seismic response plots of the current non-linear dynamic time-domain analyses of the 3D hybrid frames subjected to sequential ground excitations yield useful conclusions to provide guidelines for a safer seismic design of the hybrid building type, which is not covered by the current codes despite being a common practice.

The Modification of the Estimated Seismic Behaviour of R/C Low-Rise Buildings Due to SSI

A numerical investigation of the seismic behaviour of asymmetrical low-rise reinforced concrete (R/C) frames is performed considering the deformability of the supporting soil. The typical rigid base assumption is adopted by most current seismic design codes for ordinary buildings, implicitly assuming that the “beneficial” influence of the Soil-Structure Interaction (SSI) effects results in a decrease of the internal forces of a structure. However, in recent research works, SSI is found to affect the structural response in not always a beneficial manner and occasionally in a detrimental one. In the current study, the non-linear time-domain seismic analyses of selected 2D and 3D symmetric and asymmetric R/C framed buildings are presented considering initially the fixed base assumption. Subsequently, these R/C building models, subjected to the same seismic excitations, are analysed considering SSI, by applying a set of orthogonal footings with tie beams which interact with the soil medium. In addition, in the 3D models, the case of a foundation mat supporting the frames is examined. Comparisons between the numerical response results obtained for the examined supporting conditions yield useful conclusions regarding the modified elastoplastic estimated behaviour of common low-rise R/C buildings due to SSI, which can be used for the improvement of the seismic design codes.

Stochastic nonlinear ground response analysis considering existing boreholes locations by the geostatistical method

The field and laboratory evidence of nonlinear soil behaviour, even at small strains, emphasizes the importance of employing nonlinear methods in seismic ground response analysis. Additionally, determination of dynamic characteristics of soil layers always includes some degree of uncertainty. Most of previous stochastic studies of ground response analysis have focused only on variability of soil parameters, and the effect of soil sample location has been mostly ignored. This study attempts to couple nonlinear time-domain ground response analysis with variability of soil parameters considering existing boreholes’ location through a geostatistical method using a program written in MATLAB. To evaluate the efficiency of the proposed method, stochastic seismic ground responses at construction location were compared with those of the non-stationary random field method through real site data. The results demonstrate that applying the boreholes’ location significantly affects not only the ground responses but also their coefficient of variation (COV). Furthermore, the mean value of the seismic responses is affected more considerably by the values of soil parameters at the vicinity of the construction location. It is also inferred that considering boreholes’ location may reduce the COV of the seismic responses. Among the surface responses in the studied site, the values of peak ground displacement (PGD) and peak ground acceleration (PGA) reflect the highest and lowest dispersion due to variability of soil properties through both non-stationary random field and geostatistical methods.

Non-Linear Dynamic Analysis on a Continuum Suspension Bridge Model with Spatial Layout of Main Cables

This study proposes an approach to set up a continuum full bridge model with spatially inclined cables based on the Hamilton principle. The dynamic governing functions, considering the geometric non-linearities of cables and deck, represent simultaneously the vertical motion of deck and vertical–horizontal motion of cable. With the comparison of the modal properties obtained from the model to those from the accurate model, results show that the proposed model is capable of accurately simulating the modal properties. The primary resonance responses and corresponding frequency-response curves are obtained through the multiple-scale-method. A finite element (FE) model is established, and the corresponding non-linear dynamic analysis in time domain is conducted. Comparing the results from two models, it can be checked that the proposed model is reliable. According to the results of the proposed model, it is found that the second-order shape functions (SOSFs) play a significant role in the system response. Once the non-linear vibration of the bridge becomes significant only considering the excited mode with using the classical Galerkin decomposition cannot correctly predict the structure response. The SOSFs can be classified into stationary and vibrating components. The vibrating component can deviate the time-series of response from the harmonic wave, and the stationary component directly determines the mean value of the time-series.

Wind induced dynamic response and fatigue assessment – Nonlinear time domain versus linear stochastic analysis

By performing the nonlinear dynamic analysis and calculating the wind induced fatigue damage, this paper compares the fatigue calculation results with that obtained from a linear stochastic dynamic analysis in frequency domain. It is noticed that, since linear frequency domain analysis often involves a linearization of relevant non-linear load effects, associated with non-linear drag, coherence of wind loading in space, large deformation and local plasticity development, into the linear solution of dynamic equilibrium equations, and also because the power spectrum of critical stress (quasi-static and dynamic) due to wind loading may not be narrow-banded, initiated by the influence of the background components of incident turbulence, across wind-induced vibrations, wind directional effects and structural damping and so on, the inappropriate use of the linear spectral method developed for Gaussian processes can mis-predict the dynamic response, leading to a significant bias in the fatigue damage assessment. It is found that the disadvantages of the linear method aforementioned have to be compromised by additional assumption of uncertainties implemented in calculating dynamic response, often resulting in an over-conservative evaluation in fatigue damage estimation. The wind induced fatigue calculation procedure using non-linear dynamic analysis can be widely adopted for various types of structures, which can significantly reduce the uncertainties without compromising the safety requirement.

A novel method for calculating the dynamic force coefficients of Gas Foil Bearings and its application in the rotordynamic analysis

Bearing force coefficients are a fundamental and convenient concept in the dynamic analysis of a bearing–rotor system. However, for a rotor system supported by gas foil bearings (GFBs), recent studies have shown that the onset speed of instability (OSI) predicted using the force coefficients model is inconsistent with that obtained using nonlinear time-domain analysis. To solve this problem, this study proposed a novel method for calculating the dynamic force coefficients of GFBs. The correctness and effectiveness of the proposed method were confirmed by examining the calculation of the bearing force coefficients, the stability prediction and the calculation of unbalance responses. For a classical symmetric GFB–rotor system, application of the proposed calculation method demonstrated that the OSI predicted by the force coefficients model can be in complete agreement with the OSI predicted by the fully coupled model for all compliance levels. This indicates that the force coefficient method has the potential to make accurate prediction for the stability characteristics of GFB–rotor systems. Furthermore, the proposed method is derived based on the general dynamic equation for linear structures; hence it is able to adopt a complex foil structure model. The one-dimensional finite element foil model that considers detachments of the top foil from the bump foil was used to show the ability of the proposed method to use a complex foil structure model.

Numerical modelling of offshore risers conveying slug flow under the ALE–ANCF framework

A nonuniform distribution of internal flow along the offshore riser can lead to transient in-plane excitation. To predict the global riser response due to slug flow by nonlinear time domain analyses, a finite element method is developed in this study by combining the absolute nodal coordinate formula (ANCF) and arbitrary Lagrange-Eulerian (ALE) description. This proposed method has the capacity to effectively simulate both the nonuniform gravity distribution of slug flow and geometric nonlinearity of the riser. The nodal position and slope vectors described in the global coordinate system avoid the complex coordinate transformation of the elements while the internal fluid is effectively integrated into the framework. After the accuracy of the proposed program is verified, a kind of steep wave riser (SWR) with internal flow is taken as an example to discuss the effect of slug flow. The results show that slug flow can result in large local deformations and lead to variable pattern changes in the bending moment.

Development of nonlinear framework for simulation of Typhoon-induced buffeting response of Long-span bridges using Volterra series

This paper presents a nonlinear time-domain analysis framework to simulate the buffeting response of long-span bridges subjected to the typhoon winds. The analysis framework separates the aerodynamic forces generated on the bridge deck into low- and high-frequency components modelled by the quasi-steady and Volterra series-based wind load models, respectively. The aerodynamic nonlinearity and non-stationary wind effects existing in the wind-bridge interaction are incorporated in the analysis framework in terms of the ① static force coefficients measured at low-frequency effective angle of attack, ② flutter derivatives identified at varying angles of attack, ③ higher order fluid memory terms of the Volterra series and ④ time-varying mean wind speed. The efficacy of the proposed framework is verified by presenting the numerical example of a suspension bridge fully immersed in the typhoon winds with aerodynamic characteristics sensitive to the effective angle of attack. The dynamic analysis results show good agreement in the simulation of the typhoon-induced buffeting response of the bridge deck. Moreover, the simulation results are also compared with the measurements, and the existing linear and nonlinear wind load models to elucidate the efficiency of the proposed framework.

A nonlinear soil-structure interaction analysis technique based on seismic isolation design response spectrum for seismically isolated nuclear structures with rigid basemat

Seismic Analysis of Safety-Related Nuclear Structures (ASCE 4-16) offers a two-step nonlinear soil-structure interaction analysis procedure for seismically base-isolated structures based on the seismic isolation design response spectrum. The two steps are (I) development of seismic isolation design response spectrum at the foundation level of an isolated structure using frequency domain soil–structure interaction (SSI) analysis for an equivalent linear SSI system and (II) nonlinear time domain analysis of the isolated structure using foundation input motions, which is consistent with the seismic isolation design response spectrum. In step II, the rocking component of the structure shall be considered when its effects are significant. However, the ASCE 4-16 does not present how to consider the rocking input. In this study, we propose a method of taking account the rocking component of a base-isolated structure with rigid basemat. Specifically, this paper presents a method of developing rocking input motion that is fully coupled with horizontal input motion at the base of the isolated structure. The method was verified by comparing numerical results using the rocking input for a base-isolated nuclear power plant with rigid basemat on a compliant soil medium with those of a refined nonlinear response history analysis.

A methodology to prevent process piping failures during vapor cloud explosions

The design and evaluation of offshore structures’ piping systems subject to blast events are of significance and require advanced analysis approaches. They are important because during an explosion rupture of a piping and vessel system leads to the leakage or release of hydrocarbons which will likely cause another explosion. Advanced nonlinear analysis in time domain is required in order to agreeably determine the dynamic behavior of the piping and vessels against blast loadings. A linear approach, for example using Caesar II software package, often gives very conservative results. This conservative design approach results in pipes and vessels with high wall thickness. Such pipes and vessels bring more weight to offshore facilities and are not desirable, especially for floating structures. In other words, advanced non-linear time domain analysis is required if weight reduction is a must. This analysis type, broadly, should consider; i. Drag load and blast overpressure, ii. Nonlinear material features for instance thermal and strain-rate dependence, iii. Effects of nonstructural masses and adjacent piping systems; iv. Pipe supports, v. Failure of flanges and piping detail, vi. Effects of operating temperature on material characteristics, vii. Blast direction/Ignition location/Attenuation sensitivity; viii. Shielding effect, i.e. pipes behind large objects such as vessels, and ix. Effects of pipe insulation, e.g. raised pipe diameters. The study, firstly, examines the approach/techniques to describe for such effects with finite element analysis. This paper then uses case studies to demonstrate the methodology that includes advanced simulation techniques for pipe blast behavior. The case studies include a piping system that is simulated from overall to detail modeling. Simulations are carried out using the general-purpose, FEA package, ABAQUS. The goal of the paper is to discuss the challenges and propose the methodology for realistic simulation of response of a piping system in a blast event. The paper is expected to serve as a complimentary example to recommended practice (FABIG Technical Notes and API 2FB 2006).

A non-linear static approach for the prediction of earthquake-induced deformation of geotechnical systems

This paper illustrates an original and simple method to predict earthquake-induced deformations of geotechnical systems. The method is an extension of static non-linear analysis, and is conceived to predict the behaviour of geotechnical systems, like supported and unsupported excavations, that during the seismic motion accumulate displacements in a single direction. The seismic capacity of the system is described by its capacity curve, obtained either from a numerical push-over analysis or through a simplified procedure. The corresponding seismic demand is described by a combination of the elastic response spectrum, including basic information on the maximum amplitudes of the seismic motion, and a cyclic demand spectrum, that provides additional information about the equivalent number of cycles that contribute to the accumulation of displacements. In the paper, the method is described in detail and is validated through different procedures, namely: comparisons with experimental results obtained in the geotechnical centrifuge; comparison with results of advanced numerical analyses; extensive comparison, using a large database of seismic records, with the results of non-linear time-domain analyses. In its final part, the paper provides guidance for the practical use of the method for design.

Nonlinear energy sink and Eurocode 8: An optimal design approach based on elastic response spectra

In this paper, the authors propose novel empirical formulae for the optimal design of Nonlinear Energy Sinks (NESs) to control seismic induced vibrations in structures. While large part of the existing literature on NES for seismic applications is based on deterministic analyses of the structural response to recorded ground motions, herein the effectiveness of the device is studied in a stochastic framework. In fact, the seismic excitation has been modeled using a response spectra consistent power spectral density function, taking into account design spectra prescribed into Eurocode 8. Statistics of the structural response have been determined by Monte Carlo Simulations, performing nonlinear time-domain analyses to investigate the dependence of the optimal NES parameters on the main characteristics of the primary system and on the seismic load amplitude. The outcomes of these analyses have been translated into empirical expressions allowing for computing the optimal NES stiffness and damping. Since these are closed-form relationships depending on the main structure and the response spectra parameters, their use allows for an immediate estimate of the NES optimal design configuration, avoiding demanding numerical analyses and making their implementation suitable for practical engineering purposes. The accuracy of the design formulae has been tested by comparison with numerical optimisations for a set of possible configurations of the main structure and for varying intensity of the external excitation. Although the proposed relationships have been extrapolated from single degree of freedom system responses, applications to multi degree of freedom structures is quite straightforward, as shown through two case studies involving the analysis of a 2D multi-storey structure and a 3D multi-bay frame controlled by two orthogonal NESs.

Integrated design optimization of spar floating wind turbines

A linearized aero-hydro-servo-elastic floating wind turbine model is presented and used to perform integrated design optimization of the platform, tower, mooring system, and blade-pitch controller for a 10 MW spar floating wind turbine. Optimal design solutions are found using gradient-based optimization with analytic derivatives, considering both fatigue and extreme response constraints, where the objective function is a weighted combination of system cost and power quality. Optimization results show that local minima exist both in the soft-stiff and stiff-stiff range for the first tower bending mode and that a stiff-stiff tower design is needed to reach a solution that satisfies the fatigue constraints. The optimized platform has a relatively small diameter in the wave zone to limit the wave loads on the structure and an hourglass shape far below the waterline. The shape increases the restoring moment and natural frequency in pitch, which leads to improved behaviour in the low-frequency range. The importance of integrated optimization is shown in the solutions for the tower and blade-pitch control system, which are clearly affected by the simultaneous design of the platform. State-of-the-art nonlinear time-domain analyses show that the linearized model is conservative in general, but reasonably accurate in capturing trends, suggesting that the presented methodology is suitable for preliminary integrated design calculations.

Basin edge effect on industrial structures damage pattern at clayey basins

In this numerical study, the 2D dynamic behavior of a clayey basin and its effect on damage pattern over basin edge are investigated. To attain this goal, a fully nonlinear time domain analysis method has been applied. Then, the fragility curves of the considered two typical industrial structures for that certain point are estimated using the acceleration time histories recorded at each surface point. The results show that the use of the damage related parameters in site effect analyses, instead of amplification curves, can yield more realistic estimation of the basin dynamic response. In a distance about 150m from outcrop at the basin edge, the differences between fragility curves increase when increasing the distance from outcrop with respect to the reference rock site. Outside this region and towards the basin center, they tend to occur in rather single curves. Furthermore, to connect the structural damage to the basin edge effect, the earthquake demand value at different points for two typical structures was evaluated. It was seen that the probability of occurrence of damage increases over 250 m from outcrop, while the effect of the basin edge was limited to 150 m in case of the basin edge evaluation by using fragility curves.

Time series prediction of mooring line top tension by the NARX and Volterra model

To minimize the computation burdens of long-term analysis, the mooring line top tensions under various short-term sea states were predicted using the pre-calculated nonlinear time domain analysis results of some selected sea states. A nonlinear autoregressive with an exogenous input (NARX) technique was introduced with a finite nonlinear memory length to predict the top-tension of a mooring line of the box-type floating production storage and offloading (FPSO). The NARX was designed in such a way that it takes the floater’s motions as its input and produces the mooring line top tension as an output. After training the NARX using the pre-calculated time series of the motions and tensions of some selected sea states, the tension time histories of different sea sates were predicted and compared with the direct time domain analysis results. In addition, to explore the nonlinearity of the system and its contribution to the response, the transfer functions of different orders were extracted after expanding the NARX equation using a Taylor series expansion. The nonlinear contributions coming from both the 3rd and 5th order were significant.

Nonlinear time domain and stability analysis of beams under partially distributed follower force

• A geometrically exact beam formulation is used to obtain the stability and nonlinear time domain analysis. • A wide range of beams with different flexibility ratios are utilized in this investigation. • The behavior of the eigenvalues at pre- and post-instability as well as the frequency and time domain results are obtained. • The stability and nonlinear behavior are highly affected by partially follower forces length and position. This paper aims to investigate linear and nonlinear behavior of beams subjected to externally applied partially distributed follower forces. In this investigation, the nonlinear composite beam theory of Hodges is used. The system of nonlinear equations is linearized about the equilibrium, or rest structure state, and the linear system is solved numerically. The effects of follower force position on the behavior of eigenvalues at pre- and post-instability are reported. Additionally, the contours of critical follower force are obtained by changing the position of follower force in span-wise and chord-wise directions. The effects of different parameters such as the length, and position of follower force and the ratios of stiffnesses on the critical follower force as well as the nonlinear limit cycle oscillation (LCO) are reported. The obtained results indicate that the length and the position of the partially distributed follower forces considerably affect the stability of the beam.

Review of pipeline span analysis

PurposeThe purpose of this paper is to mainly review the state-of-the-art developments in the field of hydrodynamics of offshore pipelines, identifying the key tools for analysis of pipeline free spans, their applications, their qualifying characteristics and capabilities and limitations.Design/methodology/approachThese different analytical, numerical and semi-empirical tools available for predicting such hydrodynamic loads and their effects include VIVANA, PIPESIN, VIVSIM, SIMULATOR, FATFREE, amongst others. Inherent in these models are current effects, wave effects and/ or pipe–soil interactions.FindingsAmongst these models, the most attention was given to the new VIVANA model because this model take into account the vortex-induced effects with respect to free-spanning pipelines (which have dominant effect in the span analysis in deep water) better than other semi-empirical models (such as Shear 7). Recent improvements in VIVANA include its ability to have arbitrary variation in speed and direction of current, as well as the ability for calculation of pure IL and combined IL-CF response. Improvements in fatigue assessments at free spans, i.e. pipe–soil interaction have been achieved through the combined frequency domain and non-linear time domain analysis methodology adopted. Semi-empirical models are still the de facto currently used in the design of free-spanning pipelines. However, there is need for further research on free-span hydrodynamic coefficients and on how in-line and cross-flow vibrations interact. Again, there is still the challenge due to VIV complexity in fully understanding the fluid structure interaction problem, as there is no consolidated procedure for its analysis. It has been observed that there is large scatter between the different codes adopted in the prediction of fatigue damage, as there lacks full-scale test data devoted to determination/validation of the coefficients used in the semi-empirical models. A case study of the preliminary design of a typical 48 in. pipeline has been presented in this study to demonstrate the use of the free-span analysis tool, DNV RP F105. Excel spreadsheet has been applied in the execution of formulas.Originality/valueThis review paper is the first of its kind to study the state-of-the-art development in pipeline free-span analysis models and demonstrate the use of analysis tool, DNV for MAFSL calculation. Hence, information obtained from this paper would be invaluable in assisting designers both in the industry and academia.