Evaluation of Polymer Modified Mortar and Bonding Agent for Structural Repair

Polymer modified mortar is found to be suitable for structural repair and strengthening of damage structural elements. Conventional mortar is not preferred in repair of concrete since it has inferior mechanical property and durability performance. Polymer based mortar is an alternative to conventional mortar with enhanced mechanical properties. However, there are limited specifications and guidelines available for specifying PMM mixes for structural repair work. The research work aims to evaluate the mechanical performance of polymer based mortar with varying concentration of styrene butadiene rubber latex at laboratory scale. Another aspect in repair of corrosion damage structures is the bond between the substrate concrete and repair mortar. In order to study the effectiveness of bonding agents, the performance evaluation of bonding agents has been evaluated using slant shear test and pull-off test as per ASTM C 882 and EN 1542 respectively. Findings of study indicates that at 8-10 percent concentration of dry polymer solid by cement mass in polymer based mortar is the optimum dosage. Styrene-butadiene rubber based polymer mortar showed improvement in flow in comparison to normal mortar however, mixes with crushed sand shows decrease in flow which is due to presence of more fines. Slant shear and pull-off test method shows epoxy bonding agent give better bond strength as compared to SBR latex.

Muscular and Tendon Degeneration after Achilles Rupture: New Insights into Future Repair Strategies

Achilles tendon rupture is a frequent injury with an increasing incidence. After clinical surgical repair, aimed at suturing the tendon stumps back into their original position, the repaired Achilles tendon is often plastically deformed and mechanically less strong than the pre-injured tissue, with muscle fatty degeneration contributing to function loss. Despite clinical outcomes, pre-clinical research has mainly focused on tendon structural repair, with a lack of knowledge regarding injury progression from tendon to muscle and its consequences on muscle degenerative/regenerative processes and function. Here, we characterize the morphological changes in the tendon, the myotendinous junction and muscle belly in a mouse model of Achilles tendon complete rupture, finding cellular and fatty infiltration, fibrotic tissue accumulation, muscle stem cell decline and collagen fiber disorganization. We use novel imaging technologies to accurately relate structural alterations in tendon fibers to pathological changes, which further explain the loss of muscle mechanical function after tendon rupture. The treatment of tendon injuries remains a challenge for orthopedics. Thus, the main goal of this study is to bridge the gap between clinicians’ knowledge and research to address the underlying pathophysiology of ruptured Achilles tendon and its consequences in the gastrocnemius. Such studies are necessary if current practices in regenerative medicine for Achilles tendon ruptures are to be improved.

Numerical simulation on Crashworthiness of 105000t LNG Carrier

It is of great significance to study the crashworthiness of LNG carrier to improve its crashresistance and enhance its operation safety. In this paper, the collision process between the bulbous bow of the container ship and the side structure of the LNG ship is analyzed by using nonlinear finite element numerical simulation. Collision performance of LNG carrier and collision indicators during the collision, the impact force, velocity and displacement and energy absorption in the process of collision by changing parameters of the major velocity, impact angle and impact location and others are studied. The relevant research results have a strong practical significance for analyzing the deformation, strengthening measures and structural repair of ship side structure impact damage.

Advances in the Restoration of Buildings with LIDAR Technology and 3D Reconstruction: Forged and Vaults of the Refectory of Santo Domingo de Orihuela (16th Century)

This research presents a new intervention methodology on arches and vaults of a Renaissance factory in the Colegio Santo Domingo de Orihuela (16th century) using 3D software LIDAR technology that verifies the execution process of the works studying the different charges states and structure behavior. This document aims to explain a working methodology in the monitoring of structural repair interventions in the architectural heritage, in the specific case of the replacement of traditional one-way timber joist frame slabs on structures of former, splay and groin arches between vaults. This involves the compilation and processing of two types of data: on the one hand, the analysis of the different load states to which the intervention is exposed in its different phases: initial, dismantling of the different layers of traditional construction and replacement by the new structural system; and, on the other hand, the graphic information provided by the photogrammetry techniques used to dimension and define the spatial position of the structural elements that have historically resolved the covering of the architectural space in this type of Renaissance solution. The different layers and demolished materials have been verified by analysing their constructive disposition, thicknesses, and dimensions of the elements that formed part of the initial construction system and their own weights. In addition, the new construction systems used in the restoration project generate a state of loads similar to the existing one. The LIDAR technology used in the research process provides graphic data of the spatial position of the arches and vaults studied in the different states of the construction intervention. The point clouds obtained are analysed by taking as reference fixed points (considered unalterable and infinitely rigid) of the refectory and the coordinates of the initial and final states are compared. The results show minimal variations between the two positions, which justifies the goodness of the construction methods used and the structural safety obtained in the complex. This methodology applied to arches and vaults in heritage architecture guarantees the control and recording of the movements produced in the process.

Policy Forum: Tax, Social Security, and Employment Status—Removing the Distortions in the United Kingdom

The COVID-19 pandemic has strained tax and social security systems. Cracks that have existed for some time have been opened up further and are unlikely to close without structural repair. New insights into the shifting nature of work, combined with the development of technologies that can provide modern, practical solutions to old problems, offer the opportunity to rethink the way we tax gig workers and other non-standard providers of labour. This article argues that we need to free ourselves from the employment status classifications developed in other areas of law, for other purposes, when we consider the design of tax and social security provisions. We should aim to harmonize the tax and social security treatment of all those who provide labour as far as is practically possible in order to increase equity and remove distortions. Where that cannot be achieved, despite the benefits of new technologies, dividing lines should be dictated by tax and benefits policy objectives rather than linkages to case law that has evolved in other areas.

Structural Repair/Retrofit of Brick Masonry Walls

The various methods presently available for the repair of brick masonry walls are reviewed. Particular attention is given to structural repair made necessary as the result of earthquake induced damage or retrofit measures to be applied to an existing masonry structure to increase seismic resistance. Among the techniques discussed are: crack injection with epoxy or resin, crack or void injection with a cement based grout, surface coating methods, base isolation, repointing or limited replacement of damaged elements and installation of steel reinforcing elements. Use of nondestructive evaluation methods to determine the initial damaged state and the condition of the repaired masonry wall will also be presented.

Reactive Powder Concrete: Durability and Applications

Reactive powder concrete (RPC) is an ultra-high-performance concrete (UHPC) developed years ago by Bouygues, with the aim to build strong, durable, and sustainable structures. Some differences can be underlined between the RPC and high-performance concrete (HPC); that is to say, RPC exhibits higher compressive and flexural strength, higher toughness, lower porosity, and lower permeability compared to HPC. Microstructural observations confirm that silica fume enhances the fiber–matrix interfacial characteristics, particularly in fiber pullout energy. This paper reviews the reported literature on RPC, and it offers a comparison between RPC and HPC. Therefore, some RPC potential applications may be inferred. For instance, some examples of footbridges and structural repair applications are given. Experimental measurements on air permeability, porosity, water absorption, carbonation rate, corrosion rate, and resistivity are evidence of the better performance of RPC over HPC. When these ultra-high-performance concretes are reinforced with discontinuous, short fibers, they exhibit better tensile strain-hardening performance.

Structural repair on a composite aircraft fuselage damaged by fire.

Composite materials have been used on aircraft for decades with tremendous benefits. Through the use of these advanced materials we have seen a great increase in the aircraft’s efficiency, while improving the strength of the aircraft. Unfortunately due to the complexity of this material, it has not been used in large structural components such as the fuselage until very recently. Because of this, there are still some unknown aspects of implementing this material which have not yet been researched. One example that demonstrates this is a large section of an aircraft’s composite fuselage structure which has sustained fire damage. The main difficulties here are the unknown extent of damage caused by the fire, the unproven repair methods, and the durability of the repair patch itself. This report outlines some of these challenges as well as offers two different repair methods that are then analyzed using CATIAs FEA suite.

Structural repair on a composite aircraft fuselage damaged by fire.

Composite materials have been used on aircraft for decades with tremendous benefits. Through the use of these advanced materials we have seen a great increase in the aircraft’s efficiency, while improving the strength of the aircraft. Unfortunately due to the complexity of this material, it has not been used in large structural components such as the fuselage until very recently. Because of this, there are still some unknown aspects of implementing this material which have not yet been researched. One example that demonstrates this is a large section of an aircraft’s composite fuselage structure which has sustained fire damage. The main difficulties here are the unknown extent of damage caused by the fire, the unproven repair methods, and the durability of the repair patch itself. This report outlines some of these challenges as well as offers two different repair methods that are then analyzed using CATIAs FEA suite.