Numerical Simulation of Failure Analysis of Storage Tank with Partition Plate and Structure Optimization

Storage tanks with partition plates are widely used in the petrochemical industry. However, relevant standards do not propose corresponding design criteria and methods for this type of structure, and theoretical design formulas cannot be applied to ensure the reliability of its structure. Therefore, it is necessary to analyze and design the storage tank with a partition plate by using finite elements. This paper studies the problem of buckling depression and cracks in the welded parts of the S-shaped tank with a partition plate during its operation. We used the finite element software ANSYS to analyze the overall strength and stability of the structure and obtain the larger stress area. Based on this, a safe and economical optimization plan is proposed: under the condition of strictly controlling the liquid level difference on both sides of the partition, the tank structure is optimized by adding stiffeners and tie rods. The study revealed that the measure effectively improves the overall rigidity of the tank body and reduces the maximum stress of the structure and enhances the safety performance of storage tank. Additionally, it provides a reference for the structural strength design of storage tanks with partition plates.

Analysis of Seismic Action on the Tie Rod System in Historic Buildings Using Finite Element Model Updating

Historic buildings have a high architectural value and their maintenance, repair and rehabilitation require a special approach. This approach is mainly based on the buildings’ performance under non-destructive tests such as operational modal analysis (OMA). Under extreme loads, such as earthquakes, these buildings require representative numerical models to simulate their expected response. In historic buildings, tie rods transfer axial loads and are typically used to balance horizontal trust due to static and dynamic loads associated with seismic actions. It is very important to determine the possibility of exceeding their load-bearing capacity under extreme loads, such as an earthquake. In this context, this paper presents an approach for the analysis of seismic action on the tie rod system in a historic building. The analysis was performed by combining the on-site experimental testing and the finite element model updating (FEMU) of the local models of tie rods and the global model of the structure. It was shown that the combination of analyzing local and global structural models, experimental on-site testing and FEMU is a viable solution for assessment of historic buildings’ load bearing capacity.

A Novel Bond Anchor for Unidirectional FRP Member: Conceptual Design and Experimental Investigation

Fiber-reinforced polymer (FRP) is an advanced composite material with many advantages including light weight, high strength, and high fatigue and corrosion resistance, which makes unidirectional FRP suitable for tension members, such as cables, prestressing tendons, and tie rods. However, the unidirectional FRP is a typical isotropic material, which is difficult to be anchored and hence unable to give full play to the advantages of FRP. To solve the anchoring problem of unidirectional FRP member, a novel bond anchor, i.e., dissolution-rebond anchor, is proposed in this paper. In this novel anchorage system, the polymer matrix of two ends of the unidirectional FRP member is dissolved by solvent and the fibers in the anchorage length are directly bonded by the binder. Theoretical analysis was performed to illustrate the high anchorage bearing capacity of this dissolution-rebond anchor. Static tensile test was conducted to verify this novel anchor design and compare with traditional bond anchor. Results show that the novel dissolution-rebond anchor is feasible and its anchorage efficiency is significantly higher than the traditional bond anchor.

The City of L’Aquila after the 2009 Earthquake: Review of Connections between Depopulation, Identity and Continuity

The chapter wants to take into consideration the progressive loss of identity and authenticity of the city of L’Aquila, located in the Abruzzi region of central Italy about a hundred kilometers east of Rome, after the earthquake of 2009. Described as “a small Florence of the Italian Renaissance”, L’Aquila is nestled in a basin surrounded by mountains, with what was a fully recognizable identity until the devastating earthquake which took place on April 6, 2009, the night after Palm Sunday. After those violent seismic shocks, repeated in 2016 and 2017, there was a progressive demographic depopulation, since the historic center of the capital and that of the hamlets have been closed and declared a “red zone”. The population, especially the younger ones, no longer recognizes themselves in their place of origin, and many people have preferred to leave. Authenticity, both material and formal (of the urban form) is also increasingly diminishing. Today the image of the city, which had been handed down over centuries, is lost. Immediately after the 2009 earthquake the city was closed and barred, preventing residents from remaining in their homes, even in the less damaged ones. The historic center was isolated and emptied, occupied by the military forces and the Fire Brigade. Contrary to any common sense, instead of immediately carrying out consolidation and restoration work (especially with regards to the more characteristic minor structures), it was decided to begin with long and expensive shoring and scaffolding installations. A forest of props and tie rods that secure the walls and draw imaginative and imposing patterns, thus postponing sine die urgent works. With the forced expulsion of the inhabitants which has now lasted for nearly seven years, the younger generation particularly, is showing (perhaps unconsciously) more and more indifference and detachment from their roots in the historic center. As time passes social and economic interest (as well as those of identity) in returning to their past houses fade. They prefer to pass time elsewhere, either in the suburbs where anonymous shopping centers have mushroomed, or in other cities (in some aspects this has been favored by the possibility of obtaining funds for the purchase of houses outside the municipality). This is why one can speak of a double loss of identity and continuity. The topic should, therefore, be approached from a twofold point of view: identity and continuity. Identity meaning that which transmits the original model and characteristic of place and the inhabitants; and continuity meaning that which allows you to remain permanently in the same place with a stable dwelling. We also find a dual meaning in lasting continuity; the people (inhabitants), and the space and form of architecture. Identity and continuity are also reflected in lifestyle, as well as in details, materials, colors and common feelings. A ‘sentimental heritage’ as well as a material one, which is now lost. There is, therefore, a twin theme: that of the continuation of archetypes, and that of housing models in which the population recognizes itself. Today in L’Aquila, identity has disappeared. The inhabitants no longer appear as protagonists, but are reduced to extras, to mute actors against the backdrop of an incomprehensible scene. Even if the search for a lost identity and continuity may now seem an unreal or utopian goal, it should have been the opposite; they should have been the priority and gone hand in hand with the reconstruction. At the end, the various restoration and reconstruction criteria for the survival of what remains of the city will also be examined.

Dynamic Analysis of the Rod-Fastened Rotor Considering the Characteristics of Circumferential Tie Rods

The research on the dynamic performance of the rod-fastened rotor (RFR) has always been a hotspot. However, the structural complexity of RFR has brought significant challenges to the dynamic study of the RFR. The tie rods provide preload for the rotor shaft segment, while the coordinate deformation of the tie rods will occur during the process of vibration. In addition, the tie rods and the rotor shaft segments are structurally connected in parallel. These factors all will influence the dynamic performance of the RFR. In this paper, for a RFR system, the vibration equation of the RFR considering all factors of the tie rods is deduced in detail. The influence of various factors on the dynamic performance of the rotor is investigated. Results show that the preload directly affects the dynamic performance of the RFR system. When the preload is small, the tie rod has a larger influence on the natural frequencies of the rotor. However, when the preload force reaches a certain value, the influence of the tie rod on the natural frequencies of the rotor is almost negligible. The research results provide a theoretical reference for the understanding of and further research on RFR.

Dynamic Identification of Tensile Force in Tie-Rods by Interferometric Radar Measurements

An experimental investigation on the accuracy of dynamically determined tensile force in tie-rods by applying the interferometric radar technique was performed. Tie-rods were used in historical masonry constructions for absorbing thrusts of arches and vaults, and the radar interferometry may represent a fast and easy non-destructive approach for the tensile force identification in the occasion of structural assessments. Laboratory dynamic tests on a cable under a known tensile force show that, provided that a suitable dynamic identification model is used, tensile force evaluations made stating from interferometric radar measurements were characterized by a very good accuracy (mean error in the tensile force estimation less than 2%), comparable with evaluations made starting from accelerometric measurements. In particular, the dynamic identification model considered is a modified version of a model proposed in the literature. The influence on the accuracy in the determination of the tensile force of some features of the experimental setup, like, e.g., the employ of corner reflectors, is discussed.

Effect of Detuning of Clamping Force of Tie Rods on Dynamic Performance of Rod-Fastened Jeffcott Rotor

In view of the advantages of lightweight, high strength, easy cooling, and easy assembly, the rod-fastened rotor is widely used in the aeroengine and heavy gas turbine. However, because of assembly, stress relaxation, material creep, and other reasons, the clamping force of the tie rods will be out of tune during the long-term operation of the rotor. The detuning of the clamping force of the tie rods not only affects the contact stiffness of the contact interface but also causes the rod-fastened rotor with a certain residual shaft bow, which will affect the dynamic characteristics of the rod-fastened rotor. Based on the statistical model of rough surface contact (GW contact model), this paper presents a method to calculate the equivalent flexural stiffness of rough surface considering the detuning of the clamping force of the tie rods and gives the calculation method of the residual shaft bow deformation of the rod-fastened Jeffcott rotor with detuning of the tie rods. The effect of the preload, the rate of detuning of the tie rods, the number of detuning tie rods on the natural frequency, and the response of residual shaft bow of the rod-fastened Jeffcott rotor at a certain speed are investigated. The results show that the detuning of the tie rods makes the flexural stiffness of the rotor inconsistent along with two main stiffness directions of the rotor, which makes the natural frequency of the rotor divided into two. The negative detuning of the tie rods decreases the natural frequency of the rotor, while the positive detuning of the tie rods increases the natural frequency of the rotor. The smaller preload or the larger rate of detuning of the tie rods makes the detuning of the tie rods have a greater influence on the natural frequency of the rotor. These results will provide a theoretical reference for the dynamic analysis and design of the rod-fastened rotor.