Limit Analysis for Historical Masonry Bridge with CFRP Reinforcements

The paper deals with the collapse behavior of a historical masonry arch bridge subject to combined seismic loads, by means of the limit analysis and shakedown theorems. The assessment of the collapse loads and shakedown multiplier have been analyzed using lower bound theorems of the limit analysis and shakedown theory. The retrofitting consists in the application of CFRP strips on the extrados of the arch with a significant increase of the collapses and shakedown multipliers. The results of a FEM analysis have been achieved with ANSYS code involving the non-linear material behavior and the structural role of the spandrel walls and filling

A tensegrity approach to the optimal reinforcement of masonry domes and vaults through fiber-reinforced composite materials

We present a tensegrity approach to the strengthening of masonry vaults and domes performed by bonding grids of fiber reinforced composites to the masonry substrate. A topology optimization of such a reinforcement technique is formulated, on accounting for a tensegrity model of the reinforced structure; a minimal mass design strategy; different yield strengths of the masonry struts and tensile composite reinforcements; and multiple loading conditions. We show that the given optimization strategy can be profitably employed to rationally design fiber-reinforced composite material reinforcements of existing or new masonry vaults and domes, making use of the safe theorem of limit analysis. A wide collection of numerical examples dealing with real-life masonry domes and vaults highlight the technical potential of the proposed approach

Optimisation of suspended-deck bridge design: a case study

The study deals with the optimum suspended-deck bridge (i.e. suspension, cable-stayed and tied-arch bridges) design through cable adjustment. An easy linear analysis procedure is proposed based on the Force Equilibrium Method. It includes a preliminary identification of the objective function through a mathematical Sensitivity Analysis (SA) and an optimisation procedure based on the Influence Matrix Method (IMM). It neglects time-dependent effects and geometric nonlinearities. In spite of its simplicity, the proposed approach has proven to be good and functional and, on account of its straightforward physical meaning, also suitable to practising engineers. It aims to obtain an optimal moment distribution on the deck with a reasonable increment in the cable forces. An optimal distribution of stress in the cables can also be pursued. The proposed procedure is rather general and can be applied to both the design and the construction stages. The Gravina Bridge in Matera, Italy, is used as a model to illustrate the method and its applicability to practical engineering problems

Nonlinear Analysis and Retrofitting of Historical Arch Bridges

The paper deals with the collapse behavior of a historical masonry arch bridge subject to combined seismic loads, by means of the limit analysis and shakedown theorems. The assessment of the collapse loads and shakedown multiplier have been analyzed using lower bound theorems of the limit analysis and shakedown theory. The retrofitting consists in the application of CFRP strips on the extrados of the arch with a significant increase of the collapses and shakedown multipliers. The results of a FEM analysis have been achieved with ANSYS code involving the non-linear material behavior and the structural role of the spandrel walls and filling

Design and optimization of pre-tension forces in cable-stayed bridges

The construction of cable-stayed bridges is characterized by several constructive phases in which geometry, boundaries and loads vary significantly in the time, causing a change in the stresses and deformations, up until the final configuration is reached. This work presents a numerical procedure for the optimal design of the cable pretensioning in cable-stayed bridges, with the aim of obtaining a desired distribution of bending moments along the deck. An optimal pre-tensioning sequence is useful for controlling stress and strain levels during the different construction phases of the examined structures. Two case studies show the potential of the proposed procedure when dealing with technically relevant examples

Wireless and stand-alone measurement system for dynamic identification of structures

This paper contains a study a study about a wireless bluetooth measurement system useful in order to control the accelerations on great dimensions structures. The structure on which they have been carried out is a steel structure with rectangular plan. On the upper level there has been installed a vibrodina for generating a sinusoidal force for dynamic characterization of the structure. The realized measurement system utilizes a datalogger and some accelerometer; they communicate among themselves through wireless bluetooth protocol, which allows to cover distances up to 100 m. The datalogger is a common PC equipped with a module for bluetooth communication. The accelerometers are constituted by: 1) a triaxial acceleration sensor, with adjustable range among the following values [1.5, 2, 4, 6] g; 2) a gyroscope with input range of 150 degrees/second; 3) a microcontroller, with analog to digital converter with maximum samplig frequency of 610 Hz, which samples the signals and manages the device; 4) a class 1 bluetooth module which allows the communication over universal platform; 5) a 860 mAh battery. The datalogger is equipped with a software developed in LabView environment; it is able to simultaneously acquire acceleration???s samples from every accelerometer and to obtain in real time plots of accelerations, speeds and displacements and to save the samples in binary files for successive processing. The experimentation has been finalized to the calibration of the numerical model to guarantee the structure functionality and also to study the structure behaviour under dynamic actions generated by wind. This experimental activity concurred also to discover modal shape not easily recognizable also using a corrected dynamics analysis

Loading noise effects on the system identification of composite structures by dynamic tests with vibrodyne

The design of new composite structures, and the system identification of existing structures strengthened through the application of composite materials, often require dynamic tests executed with the assistance of accurate forcing devices. The present paper presents a characterization of the force time-histories that can be applied through a vibrodyne, an electro-mechanical excitation machine that is able to generate vibrations, with known frequency and amplitude. Such a device is frequently employed when dealing the experimental modal analysis of composite structures at different scales. We conduct an experimental study on the forcing functions generated by a vibrodyne, and the mismatches between such loading histories and the theoretical sinusoidal profiles. Next, we study the effects of such mismatches on the simulated dynamic response of a simple structural model. Based on the results of such a study, we outline a procedure for building up a database of the real forcing functions applied by a vibrodyne, over a wide range of operating conditions. Such a tool can play a key role when conducting dynamical tests on next-generation composite structures through vibrodyne

Lateral-torsional buckling of C-beams with varying inertia

The present work deals with a numerical study on the flexural-torsional buckling of a thin-walled beam with uniformly varying C-section. Approximate solutions to the examined problem are obtained through the Dirichlet variational method and the Rayleigh-Ritz discretization procedure. The presented results prove to be asymptotically convergent for increasing numbers of test functions. This convergence property highlights the technical utility of the proposed approach, on considering the difficulty of obtaining analytic solutions for buckling problems of thin-walled beams with non-uniform cross-section. © 2019 Institute of Physics Publishing. All Rights Reserved