Minimum cost strengthening of existing masonry arch railway bridges

Amin Rafiee 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.2

The preservation of historic masonry-arch railway bridges is of paramount importance due to their economic benefits. These bridges which belong to past centuries may nowadays be expected to carry loads higher than those for which they were designed. Such an increase in loads may be because of increase in transportation speed or in the capacity of freight-wagons. Anyway, adequate increase in their load-carrying-capacity through structural-strengthening is required. Moreover, the increasing costs of material/construction urge engineers to optimize their designs to obtain the minimum-cost one. This paper proposes a novel numerical optimization method to minimize the costs associated with strengthening of masonry-arch railway bridges. To do so, the stress/displacement responses of Sahand-Goltappeh bridge are assessed under ordinary train pass as a case study. For this aim, 3D-Finite-Element-Model is created and calibrated using experimental test results. Then, it is strengthened such that following goals are achieved simultaneously: (1) the load-carrying-capacity of the bridge is increased; (2) the structural response of the bridge is reduced to a certain limit; and, (3) the costs needed for such strengthening are minimized as far as possible. The results of the case study demonstrate the applicability/superiority of the proposed approach. Some economic measures are also recommended to further reduce the total strengthening cost.

On the progressive collapse resistant optimal seismic design of steel frames

Amin Rafiee,Ali Hadidi,Ramin Jasour 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.5

Design of safe structures with resistance to progressive collapse is of paramount importance in structural engineering. In this paper, an efficient optimization technique is used for optimal design of steel moment frames subjected to progressive collapse. Seismic design specifications of AISC-LRFD code together with progressive collapse provisions of UFC are considered as the optimization constraints. Linear static, nonlinear static and nonlinear dynamic analysis procedures of alternate path method of UFC are considered in design process. Three design examples are solved and the results are discussed. Results show that frames, which are designed solely considering the AISC-LRFD limitations, cannot resist progressive collapse, in terms of UFC requirements. Moreover, although the linear static analysis procedure needs the least computational cost with compared to the other two procedures, is the most conservative one and results in heaviest frame designs against progressive collapse. By comparing the results of this work with those reported in literature, it is also shown that the optimization technique used in this paper significantly reduces the required computational effort for design. In addition, the effect of the use of connections with high plastic rotational capacity is investigated, whose results show that lighter designs with resistance to progressive collapse can be obtained by using Side Plate connections in steel frames.

Experimental and Theoretical Investigations of Creep on a Composite Pipe under Compressive Transverse Loading

Roham Rafiee,Amin Ghorbanhosseini 한국섬유공학회 2021 Fibers and polymers Vol.22 No.1

The use of Glass Fiber Reinforced Polyester (GFRP) pipes in the industry increased considerably in the pastdecades. These pipes are used in various applications such as conveying water, sewage, seawater, industrial wastewater,petroleum and also in power plants and chemical industries. These pipes are resistance to corrosion resistance and thus theyare exploited for long-term purposes. Unlike metals, creep occurs in polymeric materials at any temperature. GFRP pipes aregenerally designed to withstand against the internal pressure and also transverse compressive force as the two main loadcases. Design architecture of composite layers, i.e. number of layers and their fiber orientations, is done based on the initialresponse of the pipe structure to the aforementioned loadings known as short-term behavior. But evaluating the long-termperformance of the pipes is one of the important design requirements according to the working life of these pipes. In thisstudy, the long-term behavior of a GFRP pipe undergoing transverse loading is investigated experimentally and theoretically. The influence of structural parameters including the thickness of liner, lay-up orientation and number of layers are evaluated.

A new Hybrid Algorithm for Simultaneous Size and Semi-rigid Connection Type Optimization of Steel Frames

Ali Hadidi,Amin Rafiee 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.1

A hybrid algorithm based on Harmony Search (HS) and Big Bang-Big Crunch (BB-BC) optimization methods is proposedfor optimal design of semi-rigid steel frames. The algorithm selects suitable sections for beams and columns and assignssuitable semi-rigid connection types for beam-to-column connections, such that the total member plus connection cost of theframe, is minimized. Stress and displacement constraints of AISC-LRFD code together with the size constraints are imposedon the frame in the design procedure. The nonlinear moment-rotation behavior of connections and P-Δ effects of beam-columnmembers are taken into account in the non-linear structural analysis. Three benchmark steel frames are designed and the resultsare compared with those of standard BB-BC and of other studies. The comparisons demonstrate that proposed algorithmperforms better than standard BB-BC and HS methods in all examples and that the total cost of a frame can be reduced throughsuitable selection of its beam-to-column connection types.

Harmony search based, improved Particle Swarm Optimizer for minimum cost design of semi-rigid steel frames

Ali Hadidi,Amin Rafiee 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.3

This paper proposes a Particle Swarm Optimization (PSO) algorithm, which is improved by making use of the Harmony Search (HS) approach and called HS-PSO algorithm. A computer code is developed for optimal sizing design of non-linear steel frames with various semi-rigid and rigid beam-tocolumn connections based on the HS-PSO algorithm. The developed code selects suitable sections for beams and columns, from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange W-shapes, such that the minimum total cost, which comprises total member plus connection costs, is obtained. Stress and displacement constraints of AISC-LRFD code together with the size constraints are imposed on the frame in the optimal design procedure. The nonlinear moment-rotation behavior of connections is modeled using the Frye-Morris polynomial model. Moreover, the P-Δ effects of beam-column members are taken into account in the non-linear structural analysis. Three benchmark design examples with several types of connections are presented and the results are compared with those of standard PSO and of other researches as well. The comparison shows that the proposed HS-PSO algorithm performs better both than the PSO and the Big Bang-Big Crunch (BB-BC) methods.

Harmony search based, improved Particle Swarm Optimizer for minimum cost design of semi-rigid steel frames

Hadidi, Ali,Rafiee, Amin Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.3

This paper proposes a Particle Swarm Optimization (PSO) algorithm, which is improved by making use of the Harmony Search (HS) approach and called HS-PSO algorithm. A computer code is developed for optimal sizing design of non-linear steel frames with various semi-rigid and rigid beam-to-column connections based on the HS-PSO algorithm. The developed code selects suitable sections for beams and columns, from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange W-shapes, such that the minimum total cost, which comprises total member plus connection costs, is obtained. Stress and displacement constraints of AISC-LRFD code together with the size constraints are imposed on the frame in the optimal design procedure. The nonlinear moment-rotation behavior of connections is modeled using the Frye-Morris polynomial model. Moreover, the P-${\Delta}$ effects of beam-column members are taken into account in the non-linear structural analysis. Three benchmark design examples with several types of connections are presented and the results are compared with those of standard PSO and of other researches as well. The comparison shows that the proposed HS-PSO algorithm performs better both than the PSO and the Big Bang-Big Crunch (BB-BC) methods.

An efficient simulation method for reliability analysis of systems with expensive-to-evaluate performance functions

Bahman Farahmand Azar,Ali Hadidi,Amin Rafiee 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.5

This paper proposes a novel reliability analysis method which computes reliability index, most probable point and probability of failure of uncertain systems more efficiently and accurately with compared to Monte Carlo, first-order reliability and response surface methods. It consists of Initial and Simulation steps. In Initial step, a number of space-filling designs are selected throughout the variables space, and then in Simulation step, performances of most of samples are estimated via interpolation using the space-filling designs, and only for a small number of the samples actual performance function is used for evaluation. In better words, doing so, we use a simple interpolation function called “reduced” function instead of the actual expensive-to-evaluate performance function of the system to evaluate most of samples. By using such a reduced function, total number of evaluations of actual performance is significantly reduced; hence, the method can be called Reduced Function Evaluations method. Reliabilities of six examples including series and parallel systems with multiple failure modes with truncated and/or non-truncated random variables are analyzed to demonstrate efficiency, accuracy and robustness of proposed method. In addition, a reliabilitybased design optimization algorithm is proposed and an example is solved to show its good performance.