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The present work deals with the structural optimization of self-supported Composite Steel Trussed-Concrete Beams (CSTCB). CSTCB belongs to the category of prefabricated steel truss embedded in a concrete core casted in situ. The truss is typically composed of a steel plate, which represents the bottom chord, a system of diagonal bars and some coupled rebars working as upper chord. Optimized geometries lead to the minimization of material use. This results in the minimization of the costs, the achievement of sustainability targets, the reduction on the self-weight as well as many architectural advantages. At this purpose, a MATLAB code is herein presented. The code aims to optimize the geometry of the beam by means of a genetic algorithm (ga). Two different operative phases, before and after the concrete hardening, which characterize the mechanical response of the beam, are considered within the code. In addition, a case study is developed showing the application of the Matlab code to a homogenized prismatic beam. Advances beyond the state of the art are therefore shown.

Structural optimization is an important tool for structural designers that helps them to find innovative design solutions and structural forms with a better exploitation of materials as well as dec...

The overall seismic response of Hakka Tulous, massive traditional earth constructions located in the Fujian Province (China) and part of the UNESCO list of World Heritage buildings, is investigated. For this aim, non-linear static analysis (pushover) was used. Since Tulous are complex circular earth structures (about 50 m in diameter) stiffened by wooden frames along the whole inner perimeter of the circular earth wall, non-linear finite element models are hard to implement because convergence is difficult to achieve and very long computation time would be required given the large number of elements and degrees of freedom. For the above reasons, the equivalent frame approach is often used for masonry structures. Even if a few approximations are needed, non-linear static analysis of even very complex masonry structures can be successfully performed with fewer convergence problems and lower computational efforts. The seismic analysis of a representative circular Tulou is carried out. An extension to circular masonry structures of the analysis by macroelements through the equivalent frame method is hence studied. The results provides insight on the Tulou's failure modes and on its overall seismic response. Since this is the first study on the overall seismic response of these complex earth constructions, further research is needed to deepen our knowledge of their structural behaviour.

Glass block is a building product widely used for the construction of translucent buildingfaçades and roofs. The need to adapt the product to the regulations in the field of energy saving and environmental sustainability has led to the design of innovative configurations, through theintegration of different sub-components. These ones are able to improve its energy performanceby means of the integration of a “thermal belt”, cold glued to the glass shells, which constitute the traditional glass block, and 3rd generation solar cells. This paper reports the first results ofthe experimental program designed to assess some durability components: inherent and critical reliability.

Concrete Filled Steel Tubular (CFST) structures are increasingly used not only for columns in tall buildings but also in the arch trusses of many arch bridges and in the truss girders of buildings and bridge decks. Therefore, the chords of Circular Hollow Section (CHS) truss arches and girders are increasingly filled with concrete, effectively making them CFST structures. In addition to the strength and stiffness of the CFST members, the failure mode of the CFST joint connecting them to the tubular member is also affected by the concrete filling. In this study, truss girders with different web arrangements were tested, and their behaviour investigated. The girders were not slender because they were designed to attain the peak limiting state for joint failure rather than chord failure due to bending moments. Moreover, two other types of girders were tested: one without concrete-filled chords (CHS girder) and another with only the upper chord filled with concrete; thus allowing an investigation of how a concrete-filled chord affects joint failure mode. The geometry of the CHS girder joints was such that only chord face failure and punching shear failure could occur. The former required an inward deformation that was prevented by the concrete filling in a CFST girder with similar geometry. Finally, the study considers extending the Eurocode 3 and the AWS D1.1 code formulae, originally proposed for CHS joints, to calculate the resistance of CFST joints.

Integral abutment bridges (IABs) can be used to avoid the durability issues associated with bearings and expansion joints. For this type of bridge, the design of the optimal pile foundation, especially with respect to the horizontal stiffness, is a challenging issue. A structural optimization approach is proposed in this paper to optimize the pile foundation shape in integral abutment bridges. A procedure was implemented based on linking MATLAB, where an optimization code was developed, and OpenSees, which was used as the finite element solver. The optimization technique was compared with other techniques developed in previous researches to verify its reliability; the technique was then applied to a real 400 m-long IAB building in Verona, Italy, as a case study. The following two possibilities were considered and compared: (a) a pile with two different diameters along the depth and (b) a pile with a pre-hole. In fact, to increase the lateral and rotational flexibilities of the pile head, piles for an integral abutment bridge foundation are often driven into pre-deep holes filled with loose sand. Finally, the case of super-long integral abutment bridges (L = 500 m) with a corresponding displacement on one bridge end of approximately 50 mm was analysed. The following four pile design optimization cases were considered with similar study criteria as the Isola della Scala Bridge: (a) a pinned pile head for semi-integral abutment, (b) a fixed pile head without a pre-hole, (c) a fixed pile head with a pre-hole of any depth, (d) a fixed pile head of a pre-hole with a depth limit (

Architects and engineers have been always attracted by concrete shell structures due to their high efficiency and plastic shapes. In this paper the possibility to use concrete shells to support footbridges is explored. Starting from Musmeci’s fundamental research and work in shell bridge design, the use of numerical form-finding methods is analysed. The form-finding of a shell-supported footbridge shaped following Musmeci’s work is first introduced. Coupling Musmeci’s and Nervi’s experiences, an easy construction method using a stay-in-place ferrocement formwork is proposed. Moreover, the advantage of inserting holes in the shell through topology optimization to remove less exploited concrete has been considered. Curved shell-supported footbridges have been also studied, and the possibility of supporting the deck with the shell top edge, that is along a single curve only, has been investigated. The form-finding of curved shell-supported footbridges has been performed using a Particle-Spring System and Thrust Network Analysis. Finally, the form-finding of curved shell-supported footbridges subjected to both vertical and horizontal forces (i.e. earthquake action) has been implemented.

The overall earthquake response of Hakka Tulous, traditional earth constructions of the Fujian Province (China) and listed among the UNESCO World Heritage buildings, is investigated. Non-linear static analysis (pushover) with the equivalent frame approach is used. Although some rough approximations are assumed, this approach is well suited to model complex masonry structures, like Tulous. In fact, nonlinear analysis implemented by finite elements or by discrete elements would involve complex models hard to converge and needing long computational time. After carrying out seismic analysis of a Tulou prototype, its failure modes and overall seismic response were evaluated. The Tulou has shown to have good earthquake resistance with respect to the maximum seismic action that can be expected in the Fujian Province.

Structural optimization of arches under multi-load cases is faced. For this aim, truss-type arches are to be considered because, under different load cases, bending effects unavoidably occur in single-rib arches shaped under one load case only. An effective procedure for simultaneous topology, shape and size optimization of truss-arches under multi-load cases is proposed. For this aim, shape, size and topology variables are assembled in a unique set of variables that are simultaneously optimised by the optimization algorithm. For given Pratt-type brace pattern, different topologies have been considered by varying the node number, whereas Cubic Rational Bézier curves have been used to shape the arch chords. Optimum diameter and thickness of the circular hollow section members was also obtained. Optimization was performed in MATLAB environment, by applying a modified Differential Evolution (DE) algorithm implemented with a Constraint Domination Selection (CDS) criterion. For each design variable vector, a FEM analysis of the resulting model has been carried out by SAP2000 to evaluate the objective function value (volume) feasibility of each design variable vector in terms of structural performance. Optimal solutions have been found and compared, providing useful suggestions to consider as guidelines in truss-arche design.

Adobe buildings are located in many countries and are often constructed with fiber reinforced bricks, which are composite materials made of soil, water, and natural or artificial fibers. This study presents experimental findings for straw fiber reinforced adobe bricks typically used in Sardinia (Italy) and produced according to traditional worldwide handcrafted manufacturing procedures. A large number of compression and three-point bending tests were carried out on cubic and prismatic specimens, respectively. The identification of significant scatter in experimental data sets due to handcrafted manufacturing motivated the estimation of mechanical parameters at different percentile levels, in order to provide their characteristic and median values. The geometry of straw fibers was statistically characterized in terms of mean, standard deviation and probability distribution of their diameter and length. The mechanical characterization in compression included the estimation of fracture energy. Bending test data were processed to estimate Young?????????s modulus in tension, highlighting the bimodularity of the earthen composite material. Finally, both elastic?????????perfectly plastic and nonlinear stress?????????strain models are proposed for design/assessment purposes.

As a structural optimization technique, topology optimization is an important tool for helping designers to determine the most suitable shape of a structure. With this powerful tool, designers can define families of candidate solutions by modifying the input volume reduction (VR) ratio, reducing the structural weight as much as possible. However, finding the best compromise between material savings and structural performance among these candidate solutions is a critical issue for designers. To deal with this issue, an optimization index (OI) is presented in this paper. It provides a mathematical procedure that highlights the best choice among several candidate solutions obtained by the optimization procedure. The index was originally defined in a previous study on the structural optimization of composite steel-concrete bridges. In this paper, a generalized version of the original optimization index is introduced and used to investigate a particular aspect related to concrete shell-supported bridges. Starting from three shell-supported footbridges, the shapes of which are the final result of form-finding optimization procedures, different starting models are defined, and each is characterized by different edge-stiffening conditions. Despite using an anticlastic shell shape, unavoidable tensile stresses occur because of the thickness of the shell, variations in the material, the loading of the deck, and other factors. For each starting model, a finite-element topological optimization conducted with the solid isotropic material with penalization (SIMP) method is performed to minimize the weight (i.e., volume) of the shell by a certain percentage. According to the results obtained from topology optimization, the proposed generalized optimization index (OI*) analytical formulation is discussed in detail, and its effectiveness is validated.

In this paper, the dynamic behaviour of cement mortars reinforced with both glass and basalt fibres is studied. The influence of the addition of both types of fibre on energy absorption and tensile strength at high strain-rate was investigated, and the performance of the two types of fibre-reinforced mortar was compared. For this aim, basalt and glass fibres with same diameter and length were used. Static tests in compression, in tension and in bending were first performed. Dynamic tests by means of a Modified Hopkinson Bar were then carried out in order to investigate how glass and basalt fibres affected energy absorption and tensile strength of the fibre reinforced mortar at high strain-rate. The Dynamic Increase Factor (DIF) was finally evaluated. The experimental results show that DIF is not significantly affected by the addition of basalt and glass fibres, while energy absorption at high strain rate is significantly increased by the addition of glass fibres and only slightly increased by the addition of basalt fibres.

In the paper both a direct method and a sensitivity-based iterative method have been applied to update a finite element model of a curved cable-stayed bridge. The direct method is known as the Douglas-Reid algorithm. The sensitivity-based method is a Trust-Region algorithm. Thirteen experimental modes identified between 0 and 10 Hz under ambient condition have been considered as reference modal data. An a-priori finite element model has been implemented by using the SAP2000 software. The model has been firstly manually tuned and then updated through computational procedures implemented in MATLAB. The results of the direct and the iterative methods have been compared to each other for the specific case study.

Curved arch bridges with curved deck supported by an inclined arch either through web members or without are studied. Reference to shell-supported bridges is first made. It must be taken into account that even if the deck is supported by a shell, its bottom free edge (usually stiffened) is described by a thrust line, so that the shell connects the curved deck (that is a horizontal arch) with an inclined 3D funicular arch. A limit case is that the ring girder of the curved deck and the funicular arch merge dividing the shell into two parts, so that, if shell thickness tends to zero, no shell connects them. This is the case of curved bridges supported only at mid-span by an inclined arch. The efficiency of different arches is compared. Moreover, the deck can be supported not only at mid-span but also by web members connecting deck girder and inclined arch. In this latter case, the most appropriate form of the inclined arch is obtained.

The dynamic behaviour of earthen materials reinforced with natural fibres is little studied although earth buildings are often built in seismic areas. In this paper the dynamic behaviour of an earthen material reinforced with hemp fibres under different impact loadings has been experimentally investigated. The dynamic response of the material in 3-point bending was investigated through an instrumented dropweight device, while the response in tension and in compression was investigated through a modified Hopkinson bar device. Typical impact response curves for tension, compression and bending impact tests have been obtained. The favourable effect of fibres in dissipating fracture energy under impact loads has been observed in all these types of test.

In this paper, the dynamic behaviour of cement mortars reinforced with glass fibers was studied. The influence of the addition of glass fibers on energy absorption and tensile strength at high strain-rate was investigated. Static tests in compression, in tension and in bending were first performed. Dynamic tests by means of a Modified Hopkinson Bar were then carried out in order to investigate how glass fibers affected energy absorption and tensile strength at high strain-rate of the fiber reinforced mortar. The Dynamic Increase Factor (DIF) was finally evaluated.

The failure modes of K-joints of Concrete Filled Steel Tubular (CFST) truss structures were investigated through laboratory tests. CFST K-joint specimens consisted of a tubular chord filled with concrete and two braces inclined at the same angle with respect to the chord. Their size was chosen of the same scale as that of joints of real tubular structures currently used in bridges. The results were compared with those obtained by testing K-joint specimens of Circular Hollow Section (CHS) truss structures with the same size. Contrary to CHS K-joints, where a chord face failure mode occurred, in CFST K-joints no failure mode with inward deformation of the chord section can occur. Hence, punching shear failure was shown to be the typical failure mode of CFST K-joints, if no brace failure mode occurred before. Resistance of CFST K-joints to punching shear was then compared with the resistance values calculated through the Eurocode 3 and the AWS code formulae on CHS K-joints. The values provided by the former formula were quite close to (although always lower than) the actual resistance to punching shear of CFST K-joints. Finally, the favourable effect on joint resistance due to additional studs welded to the interior surface of the chord tube of CFST K-joint was also investigated.

A shell-supported footbridge was designed by shaping an anticlastic membrane in compression between deck and foundations. Since it would be subject to biaxial compression, it was appropriate to be ...

Recently, structural optimization has become an important tool for structural designers, because it allows a better exploitation of material, thus decreasing a structure’s self-weight and saving material costs. Moreover, structural optimization helps the designer to find innovative design solutions and structural forms that not only better exploit material but also give the structure greater aesthetic value from an architectural point of view. In this article, the seismic retrofitting of a bridge originally designed in reinforced concrete is illustrated, showing how lightening the bridge superstructure, rather than reinforcing the already completed foundations and abutments, allowed these latter features to resist greater seismic actions as required in the recent update of the Italian seismic code. Therefore, besides using the steel-concrete composite typology, the bridge superstructure was lightened through structural optimization. After having optimized the thickness of webs and flanges, it was ...

In this paper, structural analysis and design of a tensegrity bridge with prestressed deck is introduced. As a matter of fact, cable pretension results in prestressing of the deck. Nonlinear geometric effects, key load cases, influence of main cable’s rise and modal analysis of this type of structure is studied by finite element. The structural behaviour of the tensegrity bridge appears to be suitable for footbridges, although peculiar with respect to traditional ones. Some suggestions about structural design, material properties and structural behaviour are summarized.

This study examines the improvements provided by the insertion of hemp fibres with different weight fractions and lengths in an earthen material. The structural response of the materials was investigated by means of static and impact bending tests carried out on notched samples. The main focus of the analyses was in the characterization of the structural properties of the materials in terms of fracture resistance, post-cracking performance and energy absorption capability. The results of the study show that hemp fibres improve significantly the mechanical and fracture properties of the earthen material under both static and dynamic bending. It was also found that the structural properties of unreinforced and reinforced earthen materials are highly sensitive to the stress-rate, with higher strength and fracture resistance under impact loading than under static loading.

Specimen reinforced with glass and basalt fibers were prepared using Standard Portland cement (CEM I, 52.5 R as prescribed by EN 197-1) and standard sand, in accordance with EN 196-1. From this cementitious mixture, a reference cement mortar without fibers was first prepared. Compressive strength, modulus of elasticity, and mod of fracture were determined for all specimens. Static and dynamic properties were investigated using Instron testing machine and split Hopkinson pressure bar, respectively. Content of the glass fibers in the mortar does not influence the fracture stress at static loading conditions in a clearly observed way. Moreover at dynamic range 5% content of the fiber results in a significant drop of fracture stress. Analysis of the basalt fibers influence on the fracture stress shows that optimal content of this reinforcement is equal to 3% for both static and dynamic loading conditions. Further increase of the fiber share gives the opposite effect, i.e. drop of the fracture stress.

Hakka Tulous are massive circular earth constructions of the Fujian Province, China, included in the UNESCO World Heritage list. They are subjected to earthquakes of medium magnitude, but their response to the seismic action is not yet investigated in depth. The seismic response of Fujian Tulous was herein investigated through pushover analysis modelling the Tulou structure by finite elements. Although the Tulou is a big construction with a circular earth wall of about fifty meters in diameter, a micromechanical approach was used to model the earth nonlinear behaviour. Even if no binder is added to the earthen material, the Concrete Damaged Plasticity model can be adopted and has shown to be effective in modelling its nonlinear behaviour, as well as the nonlinear response of the Tulou earth wall. Performing pushover analysis of a big earth structure using a micromechanical approach seems to give reliable results, that must be proved by future research.