Influence of vibrations on structures

One type of occasional structural load is a seismic load. Earthquakes and blasts are typical sources of vibrations, but vibration generated during urban tunnel construction can represent a significant problem. Evaluation of the harmful impact of vibrations transmitted through rock massif into buildings is solved using experimental measurements, detailed analyses of measured signals, knowledge of geological pattern and constructional analysis. Seismic load of structures due to earthquakes is solved using the EUROCODE 8 standard. The earthquake movements at a certain location on the surface are determined by an elastic response spectrum to the ground acceleration. Eurocode 8 puts emphasis especially on the robust foundations and simplicity of construction systems. It is also mentioned vibration effect on historical buildings and effect under the surface, for example, in mine spaces. Historical structures are usually even more prone to vibration damage than, for example, typical wood-frame homes. The greater concerns over historic structures arise from the design, structure age, building materials and building methods used. The peak values of vibration generated by earthquake decrease with depth; the decrease is faster in shallow layers compared with the deeper part. Technical vibrations differ from natural earthquakes, for a comparable value of maximum vibration amplitudes, especially in the frequency range of the signal and mostly its duration. Evaluation of technical seismicity is more complicated because there are usually used national standards. To document some common information about vibration effects on structures, some experimental measurements are presented. Examples of real wave patterns document common shapes and also signals with significant resonant vibrations. Very interesting is an example of resonant vibration that was generated as the influence of basin structures on the shape of wave patterns due to quarry blasts. To obtain complete information, measurement system has to keep sufficient parameters, especially the frequency range of the whole seismic channel, sampling frequency, and proper anchoring of the sensor. The basic methodology for evaluation of vibration on structures is outlined.Web of Science23331129

Post-Fire Assessment of Concrete Tunnel Structures

Although concrete tunnel structures can lose strength and long-term durability due to fire, the literature on the remaining capacity of structures after fire events is very scattered, and no published post-fire inspection protocols specifically for concrete tunnel structures are available. This work aims to summarize and synthesize the current state of knowledge of the deleterious effects of fire on the residual condition of concrete tunnel structures and how the extent and degree of fire damage can be assessed. The scope of this work includes an extensive literature review, heat testing of some common tunnel elements, and residual strength testing of a tunnel wall panel. The literature review includes a review of published standards, technical reports, academic papers, and a survey of post-fire inspection practices at other state DOTs and transit organizations. Topics covered in the review include the residual mechanical properties of concrete, steel, and the concrete/steel bond after fire, the residual strength and stiffness of structural members after fire, existing inspection tools and methods for assessing concrete structures after fire, and repair methods for fire-damaged concrete structures. The outcomes of the heat testing are presented, including the setup of a radiant heating system (which does not use a flame), procurement of sample specimens for testing, thermal and physical testing of specimens, and evaluation of results. Lastly, based on the literature review and experimental testing, recommendations for future work are presented

Counterterrorism civil engineering design

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (leaf 51).Because of the increasing concern about terrorist attacks, engineers have shown a substantial interest in making buildings safer for people. In order to come up with the most adequate design, experts have to carefully define the level of risk on the new structure, since people don't want to live in bunker-like buildings. Then, a good understanding of explosive devices will be a major help to keep the damage localized, preventing the overall collapse of the structure which can cause a lot more deaths than the explosion itself. The first and most important parameter is to secure the building's perimeter by increasing the standoff distance or by using security devices such as gates or even bollards around the building; careful site planning is essential and it costs a loss less when accounted for early in the design phase. Also, a wise choice of construction materials will mitigate blast effects; windows, doors, HVAC and firefighting systems should be designed to save lives and to not cause more injuries! Finally, the major driver for a successful blast protection is designing redundancies to carry the additional loads imposed by an explosion; structural members will therefore work as mediators for alternate load paths in the case of damage of their neighboring members.by Wadih J. Jreissati.M.Eng

Proceedings of the 2004 Coal Operators\u27 Conference

Proceedings of the 2004 Coal Operators\u27 Conference. All papers in these proceedings are peer reviewed in accordance with The AUSIMM publication standard

Numerical investigation of blast and fire response of secondary tunnel structures

Submerged Floating Tube Bridges (SFTB) are evaluated as potential fixed links in the Ferry-Free E39 project led by the National Public Road Administration (NPRA). However, the risk of internal explosions and the impact of fire on these structures are major concerns that must be addressed. Such events pose significant threats to the structural integrity and the safety of individuals and property. Therefore, it is crucial to thoroughly investigate and comprehend the structural response of the external and internal components of the SFTB when exposed to blast loading and the combination of blast load and fire. The objective of this thesis was to investigate the structural response of internal structures in an SFTB to blast loading and the combined effect of blast loading and fire. LS-DYNA software was utilized to explore various scenarios, including different charge sizes of TNT, reinforcement presence, and consideration of pre-existing damage. The outcomes were a combination of anticipated and unforeseen results, particularly regarding the observed visual damage attributed to element erosion. A comprehensive preliminary study was conducted to ensure the reliability and accuracy of the material and blast models. This initial investigation aimed to identify any potential design constraints or limitations, thus establishing a robust foundation for the subsequent analysi

English for Study and Work: Coursebook in 4 books. Book 2 Obtaining and Processing Information for Specific Purposes

Подано всі види діяльності студентів з вивчення англійської мови, спрямовані на розвиток мовної поведінки, необхідної для ефективного спілкування в академічному та професійному середовищах. Містить завдання і вправи, типові для різноманітних академічних та професійних сфер і ситуацій. Структура організації змісту – модульна, охоплює мовні знання і мовленнєві вміння залежно від мовної поведінки. Даний модуль має на меті розвиток у студентів стратегій, умінь, навичок читання, пошуку та вилучення професійно-орієнтованої інформації, необхідної для ефективної професійної діяльності і навчання. Містить завдання і вправи, типові для академічних та професійних сфер, пов’язаних з гірництвом і розробкою родовищ корисних копалин. Зразки текстів – автентичні, різножанрові, взяті з реального життя, містять цікаву й актуальну інформацію про особливості видобутку мінеральних ресурсів в провідних країнах світу, сучасний підхід до розробки родовищ тощо. Ресурси для самостійної роботи (Частина ІІ) містять завдання та вправи для розширення словникового запасу та розвитку знань найуживанішої термінології з гірництва, що спрямовано на організацію самостійної роботи з розвитку мовленнєвих умінь, знань про корисні копалини, методи їх видобутку. За допомогою засобів діагностики студенти можуть самостійно перевірити засвоєння навчального матеріалу й оцінити свої досягнення. Призначений для студентів вищих навчальних закладів, зокрема технічних університетів. Може використовуватися для самостійного вивчення англійської мови викладачами, фахівцями і науковцями різних галузей

Study of blast effects on structures

Engineers have a duty to the public to preserve life and protect the community and occupants within structure that we build and use. All practicing engineers are obligated to foster the health, safety and wellbeing of the community and the environment. This involves acting on the basis of adequate knowledge and foreseeable risks that pose a potential hazard towards the built environment. The terrorism threat has evolved rapidly in scale and occurrences in recent history and with that the need to create resilient structures. This dissertation endeavours to undertake a study of the global blast loading effects on structures and identify techniques for improved structural resilience of critical elements. Blasts can be delivered by explosive events either deliberate, accidental or through indirect action. A historical review of case studies and blast incidents was undertaken to identify susceptible structures to blast and development of a structural model in order to simulate a credible scenario and understand the blast effects and predicting the design loading. The scope of the dissertation is restricted to the blast pressure disturbance effects interacting with a structure delivered by an external air blast and not considering the secondary effects of a blast incident including thermal and high velocity fragments. Common structural members and materials were used to devise a Finite Element model and simulate against the blast loading cases derived from empirical methods. Since the nature of blast load only lasting for a short time and undergoes constant change Non-Linear Transient Dynamic Analysis approach was well suited to undertaking this type of analysis. Some of the findings include whipping effects due to inertia as the structure accelerating from its initial position to develop resistance against the applied loading even after the applied load has ceased. The global response of a structure due to blast pressure, is generally a consequence of lateral or out-of-plane loading. Longer pressure phase durations tend to result in bending failures while impulsive loads (short pressure phase duration) lead to shear responses. Resilience techniques including steel UC encased in concrete, RC steel plate wraps and RC shear reinforcement lacing have the potential to improve the robustness of structural elements reducing overall displacements and stress responses