Iran during the last 40 years of the 20th century. All specimens were tested under constant gravity load and incrementally increasing in-plane loading cycles. In seismic oscillation, the instantaneous dynamic displacements of multiple positions on masonry walls can warn of crack development and reflect the propagation of the seismic waves.
More than 80% of the structures affected were masonry houses .
Dragonfly Education is an education company, that is building proprietary education content for higher learning in technical …Crack Gauge for Concrete Crack Monitoring – Displacement Measurement Devices Masonry Walls
The catastrophic consequences have offered clear evidence of the poor performance of those masonry structures during the earthquake attack. Chinese authorities at all levels have been implementing strict policies and rules on the resistance of buildings to earthquakes. A few analyze masonry structure with consideration of an earthquake or dynamic load as a model. The finite element method can reproduce the process of seismic oscillation well and reflect the influence of strain rate when a shaking table shakes, and the method is useful for studying the masonry walls in seismic oscillation.
Pressure time history, acceleration time history and strain at specific location were measured. These correlations may assist in understanding the behaviour of masonry structures subjected to explosive loading.
Ground shock wave arrival time 3.5.3. Time lag between air blast and groundshock wave 3.6. Masonry walls are generally used in almost all types of building construction in different parts of the world and have considerable historical and architectural worth.
Under blast loading, masonry walls exhibit brittle behaviour. Blast explosions generate pressures of high intensity and short duration. Retrofitting of wall is a practical way of reducing the susceptibility to blast loading, thereby, mitigating danger to occupants in the occurrence of an external explosion (1).
Dynamic response of the structures to the pressure forces was then calculated. Also it was investigated that at large scaled distance, ground shock and air blast force can be evaluated separately as the effects of both on structures decoupled.
So it was suggested that exterior masonry walls should be made stronger with glazed elements. These walls were exposed to blast loads of 0.45 kg. It was concluded that there was a marginal effect of mortar and brick strength on the structural response under larger detonation. Different types of boundary conditions of the wall were taken into consideration. Six tests with different amounts of explosives were carried out. Distance of explosive location to the target centre varies from 3 m to 4 m respectively. Vertical wooden support was erected to hold charge mass 1m above the ground. Different measuring instruments were installed to record pressure, acceleration and strains at a given locations over time during the test. These parameters were measured using pressure sensors, accelerometer and data acquisition system. Different measuring devices were employed to monitor the response of masonry wall to the blast loading. Sensors of 200 psi range was used in current blast wall pressure measurement to measure the overpressure generated by shock waves. In addition a data acquisition instruments was used. Figure 6 shows the damage pattern of detonated masonry wall. Masonry wall still maintains the integrity as before. Depth of cracks grows with increasing the quantity of explosive. Under the explosive load of 12 kg, a large longitudinal crack along the front and back side of the wall was noticed. For 14 kg explosive load, the wall fall down along the weak plane i.e. Using the experimental pressure time history, the peak value of incident overpressure is determined. Ahmad et al.′s derived relations show similar behavior but peak pressures are quite different. Also it can be stated that at the same scaled distance, the smaller the explosive weight is, longer will be the arrival time.
Reflections from the surface or a lower layer are not included. Peak particle acceleration is the maximum acceleration of acceleration time history graph. The values of backfill density, seismic velocity and attenuation coefficient have been assumed on the basis of apparent characteristics of soil, which vary with distance and depth.
With increasing scaled distance air blast wave arrival time decreases. Consideration of both air blast and ground shock parameters can develop deep understanding of response of structure against explosion. For a deeper understanding of response of masonry wall, there is a need for carrying out an extensive experimental work with charge weights of a number of intensities at various standoff distances.
Damage to brick masonry panel walls under high explosive detonations. Model validation and parametric study on the blast response of unreinforced brick masonry walls. What to look for in the aftermath of an explosion?
Cyclic behavior of perforated masonry walls strengthened glass fiber reinforced
Numerical solutions of spherical blast waves. The dynamics of explosion and its use. Blast and ballistic loading of structures. Modeling of simultaneous ground shock and airblast pressure on nearby structures from surface explosions. International journal of impact engineering, 31 , 699–717. Funny how this information was not in the original instructions. Snapping a picture of the position during inspections makes it easy to track movement. Want to mointor that crack in your concrete to see if it’s moving over time?
Since most cracks which appear in buildings are associated with difficult circumstances, this was very off-putting. I originally agreed to answer their questions anticipating they would be things like how easy the monitors were to install, if instructions were clear, if the product performed as intended, etc.
It is very important to mention that during the construction of the masonry wall, water absorption of bricks generates a decrease in the available water for hydration of mixture.
These bricks have an average size of 6.5 (±0.13) cm thick, 16.5 (±0.17) cm wide, and 26.0 (±0.27) cm in length. Mortars and concretes were mixed using electric mixers. The masonry was placed with mortar forming the walls in the laboratory of structure on a 1:1 scale. Due to the dimensions and the weight of the specimens in the study, there should be an adaptation to the test. This load is applied at a distance of 10 cm from the longitudinal edge and centered on the width of the element. Finally, device 8 measured the vertical displacement on the loading face. This is given in the three tested elements. The vertical joints have lateral displacements since the lower masonry tries to keep to its initial position and the brick on the top moves depending on the load and/or displacement applied.
Two models were used to reflect the behavior of the interaction, considering the transverse and longitudinal response of the joint. Interaction surfaces must be analyzed from the definition of a set of properties according to their behavior. Each of these properties is defined for each type of interaction, whether at the level of horizontal or vertical interactions. At this point of “rupture,” the process of tension work of adjacent areas begins, yielding or not according to the load to which it is subjected.
From there, the interaction starts to operate. Head: this element simulates a top head that allows the correct distribution of load all over the wall. Horizontal joint: this element is used for horizontal interaction at every level of joints. Brick: it is used to model the masonry element. According to the boundary condition, restrictions were defined on the horizontal axis in the entire frontal-inferior part that corresponds to the simulation of a base slab, on the vertical axis across the base of the model, and in the axis perpendicular to the plane of the wall in the frontal-inferior ridge.
Figure 7, the minimum stresses are distributed according to different patterns for the 45 cm and 26 cm wall sample, respectively. For the 26 cm wall sample, the connecting strut is as expected and has an angle of nearly 45°, starting in the upper vertical meeting and ending at the foot of the element.
The results of the tests on local materials showed a very slow speed convergence, more than 7 days of continuous iteration to arrive at a result.
In addition, the inclusion of interaction elements, which allow gliding between related surfaces, generates new indeterminations that must be solved by the program. The wall panel shows the classical central strut where the failure occurs, being more or less tilted depending on the tested wall thickness.
Torrisi (2012), the configuration of the vertical and horizontal joints modifies the stress state of the panel, since the shape of the fault is displaced and the transition points between the sliding fault and the diagonal tension are shifted depending on the resistance characteristics of each.
This representation allows future outline strategies for a more precise localization in the proper widths (greater than 30 cm thickness) for repair of walls. Damage analysis of brick-to-mortar interface. Interface model applied to fracture of masonry structures. Elastoplastic model for orthotropic materials. Seismic mitigation of a historic masonry building. A micro-mechanical homogenization model for masonry: application to shear walls. Second, the reference points are used to match a zero image with the successive images to eliminate the parallax errors. Lastly, the real displacements of a deformation point are equal to its corrected displacements on the reference plane multiplied by the photographing scale transformation coefficient.
The impact hammer was a 25-kg iron cylinder (50cm in height and 12cm in diameter), whose upper portion was welded with an arc steel bar as a hook.
The stakes were constructed at a stable place on both sides of the masonry wall, and reference points were laid on the stakes. Sony-350 digital cameras—the north and south sides of the masonry wall each with two cameras and the east and west sides each with only camera—were used to capture the instantaneous dynamic displacements of the masonry wall when the 25-kg hammer fell freely and hit the steel plate.3.2.
Monitoring a masonry wall in seismic oscillation in the field. Additionally, the digital cameras were adjusted to shoot the masonry wall clearly. Digital cameras shot the masonry wall when the 25-kg hammer fell freely and impacted the steel plate. Line 5) occurred on the west of the masonry wall. Cracks develop on a masonry wall when the shear stress is up to a certain extent. Masonry wall after seismic oscillation.5.2. In our paper, the correspondence points are the reference points on the stakes. This phenomenon is consistent with the results from a shaking table  and further suggests that it is feasible to simulate the seismic oscillation by using a hammer to impact a suspended steel plate.
Then, the bonding between the bricks and the mud is invalid in the middle-upper portion of a masonry wall. However, it is feasible as some test phenomena are consistent with the results from numerical simulation and shaking tables. It is feasible to use a hammer to impact a suspended steel plate to simulate seismic oscillation in the field. This phenomenon agrees with the test results from a shaking table.
In this video, Darryl demonstrates the HS line of Linear Displacement Sensors. These extremely precise displacement sensors…