Joint Layout Design: Finding the Strongest Connections within Segmental Masonry Arched Forms

Segmental arched forms composed of discrete units are among the most common construction systems, ranging from historic masonry vaults to contemporary precast concrete shells. Simple fabrication, transport, and assembly have particularly made these structural systems convenient choices to construct infrastructures such as bridges in challenging environmental conditions. The most important drawback of segmental vaults is basically the poor mechanical behaviour at the joints connecting their constituent segments. The influence of the joint shape and location on structural performances has been widely explored in the literature, including studies on different stereotomy, bond patterns, and interlocking joint shapes. To date, however, a few methods have been developed to design optimal joint layouts, but they are limited to extremely limited geometric parameters and material properties. To remedy this, this paper presents a novel method to design the strongest joint layout in 2D arched structures while allowing joints to take on a range of diverse shapes. To do so, a masonry arched form is represented as a layout of potential joints, and the optimization problems developed based on the two plastic methods of classic limit analysis and discontinuity layout optimization find the joint layout that corresponds to the maximum load-bearing capacity.

Causes of the Collapse of the Polcevera Viaduct in Genoa, Italy

The article investigates the causes of the Morandi viaduct collapse in Genoa. This three-span viaduct was a part of the A10 motorway leading to Savona. The structure design of the viaduct supports and diagonal stay cables was unique. The viaduct included three cable-stayed system, each supported a three-span continuous beam by two sets of prestressed concrete cables on the two sides of the pylon across the width. The pair of V shapes piers supported upside-down V pylons that supported the top ends of two pairs of diagonal stay cables. The stays were constructed from steel cables with prestressed concrete shells poured on. This article provides information on the technical condition of the viaduct and the way of strengthening the cables in the early 1990s. At that time, the author of the article visited the structure. In August 2018, the viaduct collapse occurred, and one of the structure supports collapsed. In June 2019, during the demolition process, the other two supports were destroyed. Since in Venezuela and Libya there are still two more bridges with a structure similar to that in Italy, the concept of strengthening the structure, as proposed by the author of the article 25 years ago, may still be useful.

Buckling of Spherical Concrete Shells

This study is focused on the buckling behavior of spherical concrete shells (domes) under different loading conditions. The background of analytical analysis and recommended equations for calculation of design buckling pressure for spherical shells are discussed in this study. The finite element (FE) method is used to study the linear and nonlinear response of spherical concrete shells under different vertical and horizontal load combination buckling analysis. The effect of different domes support conditions are considered and investigated in this study. Several dome configurations with different geometry specifications are used in this study to attain reliable results. The resulted buckling pressures from linear FE analysis for all the cases are close to the analytical equations for elastic behavior of spherical shells. The results of this study show that geometric nonlinearity widely affects the buckling resistance of the spherical shells. The effect of horizontal loads due to horizontal component of earthquake is not currently considered in the recommended equation by The American Concrete Institute (ACI) to design spherical concrete shells against buckling. However, the results of this study show that horizontal loads have a major effect on buckling pressure and it could not be ignored.

Buckling of Spherical Concrete Shells

This study is focused on the buckling behavior of spherical concrete shells (domes) under different loading conditions. The background of analytical analysis and recommended equations for calculation of design buckling pressure for spherical shells are discussed in this study. The finite element (FE) method is used to study the linear and nonlinear response of spherical concrete shells under different vertical and horizontal load combination buckling analysis. The effect of different domes support conditions are considered and investigated in this study. Several dome configurations with different geometry specifications are used in this study to attain reliable results. The resulted buckling pressures from linear FE analysis for all the cases are close to the analytical equations for elastic behavior of spherical shells. The results of this study show that geometric nonlinearity widely affects the buckling resistance of the spherical shells. The effect of horizontal loads due to horizontal component of earthquake is not currently considered in the recommended equation by The American Concrete Institute (ACI) to design spherical concrete shells against buckling. However, the results of this study show that horizontal loads have a major effect on buckling pressure and it could not be ignored.