Structural Crack Monitoring

S1364032116301976-gr1.jpg' alt='Structural Crack Monitoring' title='Structural Crack Monitoring' />This is a chapter from the Construction Vibration Damage Guide for Homeowners CVDG, a 100 page free document with over 200 color photos, diagrams and other. Short periods of rapid crack growth when the temperature 600C during the cleaning cycles. Long periods of very slow crack growth at the normal reactor. Keep your aircraft in the air with efficient structural integrity monitoring and realtime crack detection technology. Fast, cost effective fatique testing. Buffalo Tools Electric Chain Saw Sharpener'>Buffalo Tools Electric Chain Saw Sharpener. Chartered Engineer Clive Richardson explores structural movement including the causes and outcomes of subsidence, settlement and other forms of movement as well as. Burn barrier mastic no. Web portal for buildingrelated information with a whole building focus provided by the National Institute of Building Sciences. Areas include Design Guidance. Structural integrity and failure Wikipedia. Collapsed barn at Hrsne, Gotland, Sweden. Structural integrity and failure is an aspect of engineering which deals with the ability of a structure to support a designed load weight, force, etc. Structural integrity is the ability of an itemeither a structural component or a structure consisting of many componentsto hold together under a load, including its own weight, without breaking or deforming excessively. It assures that the construction will perform its designed function during reasonable use, for as long as its intended life span. Items are constructed with structural integrity to prevent catastrophic failure, which can result in injuries, severe damage, death, andor monetary losses. Structural failure refers to the loss of structural integrity, or the loss of load carrying capacity in either a structural component, or the structure itself. Structural failure is initiated when a material is stressed beyond its strength limit, causing fracture or excessive deformations one limit state that must be accounted for in structural design is ultimate failure strength. In a well designed system, a localized failure should not cause immediate or even progressive collapse of the entire structure. IntroductioneditStructural integrity is the ability of a structure to withstand its intended loading without failing due to fracture, deformation, or fatigue. It is a concept often used in engineering to produce items that will serve their designed purposes and remain functional for a desired service life. To construct an item with structural integrity, an engineer must first consider a materials mechanical properties, such as toughness, strength, weight, hardness, and elasticity, and then determine the size and shape necessary for the material to withstand the desired load for a long life. Since members can neither break nor bend excessively, they must be both stiff and tough. A very stiff material may resist bending, but unless it is sufficiently tough, it may have to be very large to support a load without breaking. On the other hand, a highly elastic material will bend under a load even if its high toughness prevents fracture. Furthermore, each components integrity must correspond to its individual application in any load bearing structure. Bridge supports need a high yield strength, whereas the bolts that hold them need good shear and tensile strength. Springs need good elasticity, but lathe tooling needs high rigidity. In addition, the entire structure must be able to support its load without its weakest links failing, as this can put more stress on other structural elements and lead to cascading failures. HistoryeditThe need to build structures with integrity goes back as far as recorded history. Houses needed to be able to support their own weight, plus the weight of the inhabitants. Castles needed to be fortified to withstand assaults from invaders. Tools needed to be strong and tough enough to do their jobs. However, the science of fracture mechanics as it exists today was not developed until the 1. Alan Arnold Griffith studied the brittle fracture of glass. Starting in the 1. During World War II, over 2. In the 1. 95. 0s, several De Havilland Comets exploded in mid flight due to stress concentrations at the corners of their squared windows, which caused cracks to form and the pressurized cabins to explode. Boiler explosions, caused by failures in pressurized boiler tanks, were another common problem during this era, and caused severe damage. The growing sizes of bridges and buildings led to even greater catastrophes and loss of life. This need to build constructions with structural integrity led to great advances in the fields of material sciences and fracture mechanics. Types of failureeditStructural failure can occur from many types of problems, most of which are unique to different industries and structural types. However, most can be traced to one of five main causes. The first is that the structure is not strong and tough enough to support the load, due to either its size, shape, or choice of material. If the structure or component is not strong enough, catastrophic failure can occur when the structure is stressed beyond its critical stress level. The second type of failure is from fatigue or corrosion, caused by instability in the structures geometry, design or material properties. These failures usually begin when cracks form at stress points, such as squared corners or bolt holes too close to the materials edge. These cracks grow as the material is repeatedly stressed and unloaded cyclic loading, eventually reaching a critical length and causing the structure to suddenly fail under normal loading conditions. Structural Crack Monitoring' title='Structural Crack Monitoring' />The third type of failure is caused by manufacturing errors, including improper selection of materials, incorrect sizing, improper heat treating, failing to adhere to the design, or shoddy workmanship. This type of failure can occur at any time and is usually unpredictable. The fourth type of failure is from the use of defective materials. This type of failure is also unpredictable, since the material may have been improperly manufactured or damaged from prior use. The fifth cause of failure is from lack of consideration of unexpected problems. This type of failure can be caused by events such as vandalism, sabotage, or natural disasters. It can also occur if those who use and maintain the construction are not properly trained and overstress the structure. Notable failureseditBridgeseditDee bridgeedit. The Dee bridge after its collapse. The Dee bridge was designed by Robert Stephenson, using cast iron girders reinforced with wrought iron struts. Tomtom Home 2.6 Windows. On 2. 4 May 1. 84. Its collapse was the subject of one of the first formal inquiries into a structural failure. This inquiry concluded that the design of the structure was fundamentally flawed, as the wrought iron did not reinforce the cast iron, and that the casting had failed due to repeated flexing. First Tay Rail BridgeeditThe Dee bridge disaster was followed by a number of cast iron bridge collapses, including the collapse of the first Tay Rail Bridge on 2. December 1. 87. 9. Like the Dee bridge, the Tay collapsed when a train passed over it, killing 7. The bridge failed because it was constructed from poorly made cast iron, and because designer Thomas Bouch failed to consider wind loading on it. Its collapse resulted in cast iron being replaced by steel construction, and a complete redesign in 1. Forth Railway Bridge, making it the first entirely steel bridge in the world. First Tacoma Narrows BridgeeditThe 1. Tacoma Narrows Bridge is sometimes characterized in physics textbooks as a classic example of resonance, although this description is misleading. The catastrophic vibrations that destroyed the bridge were not due to simple mechanical resonance, but to a more complicated oscillation between the bridge and winds passing through it, known as aeroelastic flutter. Robert H. Scanlan, father of the field of bridge aerodynamics, wrote an article about this misunderstanding. This collapse, and the research that followed, led to an increased understanding of windstructure interactions. Several bridges were altered following the collapse to prevent a similar event occurring again. The only fatality was a dog named Tubby.