Assessing Wind Damage to Residential Structures

Most building damage occurs at relatively low wind speeds, at or below 50 m s–1 (112 mph), as certain components fail, such as doors, windows, chimneys, and roof coverings. Rainwater then enters these openings, leading to interior damage. Structural failures usually begin with the removal of gable end walls, roof decking, and poorly attached roof structures as wind speeds increase; the greatest damage occurs at roof level as wind speeds increase with height above the ground. Internal wind pressure effects can lead to additional, more catastrophic damage, such as the removal of walls and ceilings. It is difficult to measure wind speeds directly on buildings as they would have to be instrumented well in advance of the storm, and there is no guarantee the storm would strike them. Furthermore, flying debris can damage pressure sensors on instrumented buildings. Thus, damage evaluators must infer failure wind speeds indirectly by studying damage left behind in the wake of windstorms. Therefore, it is important that damage evaluators know how buildings are constructed to better understand how they fail. This chapter identifies similar failure modes in residential structures regardless of wind type according to information from more than four decades of storm damage surveys. The information presented herein highlights some of the lessons learned in evaluating storm damage to wood-framed residential structures.

Study on Cooling System for Parked Cars using Mini Air Cooler and Exhaust Fan

Deaths among children and pets, as well as damage to car interior components, have been widely reported as a result of parking under direct sunlight for a long time. Rising car cabin temperatures in this condition trigger the formation of benzene gas, but it is not possible to turn on the AC due to security and energy consumption. Therefore, this article reports the experimental study on cabin cooling system for parked car under direct sunlight by applying a mini air cooler and exhaust fan powered by a solar cell on small car Bajaj Qute RE60. Two thermocouples were installed inside and outside the cabin to monitor the temperature for 7 hours, expressing daytime heat conditions. The results showed that this cooling system could reduce the temperature to 10 K by removing 8982 kJ (0.356 kW) of heat. In conclusion, this prototype is very promising to be developed and if implemented on a larger scale will reduce car interior damage while parking under direct sunlight.

Development of a Virtual Reality Experience System for Interior Damage Due to an Earthquake – Utilizing E-Defense Shake Table Test –

To construct a virtual reality (VR) experience system for interior damage due to an earthquake, VR image contents were created by obtaining images, sounds, and vibration data from multiple devices, with synchronization information, in a room at the 10thfloor of 10-story RC structure tested at E-Defense shake table. An application for displaying 360-degree images of interior damage using a head mount display (HMD) was developed. The developed system was exhibited in public disaster prevention events, and then a questionnaire survey was conducted to assess usefulness of VR experience in disaster prevention education.

Efficient Modeling of Nonlinear Scattering of Ultrasonic Guided Waves From Fatigue Cracks Using Local Interaction Simulation Approach

This paper presents an efficient modeling technique to study the nonlinear scattering of ultrasonic guided waves from fatigue damage. A Local Interaction Simulation Approach (LISA) is adopted, which possesses the versatility to capture arbitrary fatigue crack shapes. The stick-slip contact dynamics is implemented in the LISA model via the penalty method, which captures the nonlinear interactions between guided waves and fatigue cracks. The LISA framework achieves remarkable computation efficiency with its parallel implementation using Compute Unified Device Architecture (CUDA) executed on GPUs. A small-size LISA model is tailored for the purpose of extracting the guided wave scattering features. The model consists of an interior damage region and an exterior absorbing boundary. The interior damage region captures various types of fatigue crack scenarios, while the exterior absorbing boundary surrounds the damage model to eliminate boundary reflections. Thus, the simulation of guided wave scattering in an infinite media can be achieved utilizing a small-size local LISA model. Due to the parallel CUDA implementation and the small-size nature, this local LISA model is highly efficient. Selective mode generation is achieved by coupling/decoupling excitation profiles with certain wave mode shapes, which allows the study of sensitivity of different wave modes to a certain fatigue damage situation. At the sensing locations, mode decomposition is performed on the scattering waves, which enables the study of mode conversion at the damage. Fourier analysis allows the extraction of scattering features at both fundamental and higher harmonic frequencies. A numerical case study on nonlinear scattering of guided waves from a fatigue crack is given. The higher harmonic generation and mode conversion phenomena are presented using the wave damage interaction coefficients (WDIC), from which the sensitive detection directions can be inferred to place sensors. This study can provide guidelines for the effective design of sensitive SHM systems using nonlinear ultrasonic guided waves for fatigue crack detection.

A Framework for Evaluating Pipe Repair Technologies for CuNi Shipboard Piping Systems

A shipboard piping system can be considered analogous to the transport and distribution system of a land-based piping system. The intakes and supply pumps provide the initial uptake and head pressure while the piping system provides the distribution throughout the rest of the ship. Piping systems must not degrade or corrode due to the contained fluid but also must endure structural loadings. Interior damage can come in the form of corrosion such as pitting, general wasting away of material due to galvanic corrosion, mechanical deformations due to structural and vibrational loadings. A decision matrix based framework for evaluation using a modified Pugh Controlled Convergence technique was developed for evaluation of metallic coatings under consideration for shipboard system repairs which included mechanical and electrochemical performance characteristics. Candidate coatings for further study and additional testing requirements are identified through the process. The mechanical evaluation focuses on microstructural characterization and mechanical response. The electrochemical evaluation focuses on general corrosion and galvanic interactions between each coating and Cu0.7Ni0.3, a common piping material also often referred to as 70-30 CuNi. The outcome of the evaluation sequence is the ranking of relative merit of coatings. Results are presented which show the wide range of characteristics possible. The extension of the decision matrix to manufacturability issues will also be discussed.

Material heterogeneity in cancellous bone promotes deformation recovery after mechanical failure

Many natural structures use a foam core and solid outer shell to achieve high strength and stiffness with relatively small amounts of mass. Biological foams, however, must also resist crack growth. The process of crack propagation within the struts of a foam is not well understood and is complicated by the foam microstructure. We demonstrate that in cancellous bone, the foam-like component of whole bones, damage propagation during cyclic loading is dictated not by local tissue stresses but by heterogeneity of material properties associated with increased ductility of strut surfaces. The increase in surface ductility is unexpected because it is the opposite pattern generated by surface treatments to increase fatigue life in man-made materials, which often result in reduced surface ductility. We show that the more ductile surfaces of cancellous bone are a result of reduced accumulation of advanced glycation end products compared with the strut interior. Damage is therefore likely to accumulate in strut centers making cancellous bone more tolerant of stress concentrations at strut surfaces. Hence, the structure is able to recover more deformation after failure and return to a closer approximation of its original shape. Increased recovery of deformation is a passive mechanism seen in biology for setting a broken bone that allows for a better approximation of initial shape during healing processes and is likely the most important mechanical function. Our findings suggest a previously unidentified biomimetic design strategy in which tissue level material heterogeneity in foams can be used to improve deformation recovery after failure.

Freeze-Thaw Damage Model for Different Types of Concrete

Common concrete, lightweight aggregate concrete and self-compacting concrete with strength grade C50 were tested under freeze-thaw actions. Experimental results show that the Light weight aggregate concrete has the best freeze-thaw resistance. Furthermore, the relative dynamic elastic modulus is used to quantitatively analyze the interior damage of concrete materials subjected to freeze-thaw actions, and the freeze-thaw damage evolution equations were established by using quadratic functions, and the computational damage values agree well with the experimental results.