Study On Reliability Analysis Of Engineering Structure Based On Intelligent Optimization Algorithms

In the design and risk of analysis of structures,it is necessary to consider the effect of various uncertainties related to dimension,load,material properties,etc.Reliability analysis is a very effective technique to consider these uncertainties,and its major task is to obtain the failure probability of structures.Among various numerical methods for reliability analysis,First-Order Reliability Method(FORM)is a very prevalent method in the structural reliability community.However,when solving the high-dimensional problem with a highly nonlinear limit state function,FORM usually encounters non-convergence or divergence.This difficulty limits the further application of FORM in engineering and complex problems.In this paper,four novel and improved FORM algorithms based on different meta-heuristics are proposed for highly nonlinear and high-dimensional reliability analysis,and their have been applied in complex engineering structures.The main work can be summarized as follows:(1)A hybrid method combined with the salp swarm algorithm(SSA)and FORM is presented for reliability analysis.SSA is inspired by the behavior of searching for foods from the salp swarm living in the deep sea,and it can find the global solution in the optimization problems.In the proposed SSA-FORM method,the exterior penalty function method is utilized to handle the constraint to facilitate meta-heuristic optimization strategies.Then,SSA with strong global optimization ability is applied to obtain the global reliability index.8 examples are used to verify the performance of SSA-FORM,while several gradient-based and heuristic-based FORM algorithms are compared.The results show that the proposed SSA-FORM has better performance for nonlinear problems.(2)An improved FORM combining Harris Hawks Optimization(HHO)is presented for high-dimensional reliability analysis.HHO is a meta-heuristic algorithm mimicking the predatory behavior of Harris haw ks,and efficient in finding the global optimum of high-dimensional problems.To implement the proposed HHO-FORM algorithm,the reliability index is firstly formulated as the solution of a constrained optimization problem according to the FORM theory.Then,the constraints are handled with the exterior penalty function method.In addition,the optimal reliability index is determined by the Harris Hawks Optimization that accelerates the convergence by the population-based mechanism and the strategy of Levy Flight.The HHO-FORM doesn't need the derivatives of the limit state functions that reduces the computational burden for high-dimensional problems.So the simplicity of the HHO-FORM greatly improves efficiency in solving high-dimensional reliability problems.The HHO-FORM is tested on several high-dimensional numerical problems and then applied in several high-dimensional engineering problems.Several versions of FORM algorithms are also compared with the HHO-FORM.The experimental results show that HHO-FORM provides promising and superior results in high-dimensional problems.(3)Teaching-learning-based-optimization(TLBO)with strong convergence is introduced to combine with FORM for reliability analysis.To implement the proposed TLBO-FORM algorithm,the reliability index is formulated as the solution to a constrained optimization problem by FORM theory.Then,the exterior penalty function method is employed to handle the constraint on the optimization problem.After that,the global reliability index is de termined by TLBO.Moreover,several versions of chaotic TLBO-FORM are developed to enhance the performance of TLBO-FORM in engineering problems.19 examples with different dimension and limit state functions are investigated to verify TLBO-FORM and CTLBO-FORM.The results indicate that TLBO-FORM has better accuracy and efficiency than other comparing FORM algorithms.In addition,the reason that TLBO-FORM is more adaptable than HHO-FORM is discussed.(4)The Equilibrium Optimization(EO)assisted FORM is pr esented for structural reliability analysis.EO is inspired by control volume mass balance models used to evaluate both dynamic and equilibrium states.To implement the EO-FORM algorithm,the reliability index is formulated as the solution of a constrained optimization problem,while the constraint is handled by the exterior penalty function method.After that,the global reliability index is searched by the EO algorithm.Several engineering examples and a high-dimensional numerical example are investigated to test the proposed EO-FORM,and the results show that EO-FORM provides good accuracy and efficiency in these reliability problems.Finally,the suggestions for using four proposed metaheuristic-FORM algorithms for different reliability problems are provided.(5)The reliability problems with large and complex engineering structures are investigated,including Burro Creek bridge,geodesic space dome structure and three-dimensional rock slope.The performance of SSA-FORM,HHO-FORM,TLBO-FORM and EO-FORM proposed in Chapter 2 to Chapter 5 are tested,and the algorithmic parameters of different values are compared.In the Burro Creek bridge reliability analysis,TLBO-FORM has best performance,and EO-FORM has good performance when the algorithmic parameters a re large.In the geodesic space dome structure reliability analysis,SSA-FORM and EO-FORM has better convergence.In the reliability analysis of three-dimensional rock slope,TLBO-FORM has best performance,and EO-FORM has good performance when the algorit hmic parameters are large.In conclusion,these proposed methods can be used for complex engineering structural reliability analysis.(6)Reliability analysis on concrete core walls with steel plate concealed bracings is implemented.According to the results of quasi-static loading test of the core wall named CW3X-1,the finite element model is established in the software Open SEES.After that,several uncertainties including load,concrete and steel material performance are regarded as random variables,so we calculate the reliability index of the novel concrete wall and evaluate the structural safety by MCS.The influence of factors on reliability index and failure probability is studied,such as axial-compression load ratio,aspect ratio,span-to-depth ratio of coupling beam,steel ratio of concealed bracing,and test procedure.Moreover,meta-heuristic-FORM algorithms are applied to evaluate the sensitivity of random variables for the reliability index.