Civil engineering terms - I

 

1) Stilt: A Stilt is a common requirement in many apartments. A stilt is a floor where you have parking.[1]

2) Soft storey: It is a situation when the upper levels of a building is stiffer than the lower storey.[2] It is associated with stiffness concept.[3]

3) Stiffness of building: Young’s modulus and Area moment of inertia together make up this feature. the stiffness measures the resistance to elastic deformation. the stiffness measures the resistance to elastic deformation. Higher stiffness takes more load i.e. forces/loads taken by a structural element depends on their stiffness. But this is not only the condition. Support conditions also govern the force flow and stiffness also depends on support conditions.[4] stiffness is also dependent on the nearness or farness of the support. In this case that is the floor height and hence if the height is more, obviously the stiffness is lesser. This can create stiffness variation across floors and make the building susceptible to seismic or lateral loads.[5] Stiffer members fail suddenly, more like a brittle failure. No prior warnings. Stiffness = Load/Deformation

4) Flexibility: It can be defined as the inverse of Stiffness. Instead of resisting the force, the body tends to move/bend along the force.[6] if a body is stiff then the deformations are small. If a body is less stiff (flexible) then deformations are huge. We need our structures to be flexible but control the deformations. One way to do this is to increase the stiffness of certain structural elements, like a shear wall, to make your structure safe and decrease the deformations.

5) Strength of building: strength is the ability of the material to take the load or support it without failure. It measures how much stress the material can handle before permanent deformation occurs. Maximum stress taken by a material is called Strength. In other words, the maximum load taken by the material before its failure is called Strength.[7]

6) Weak storey: A weak storey is a storey which is weaker than the storey above it. The strength of the storey is lesser than above storeys.[8] It is associated with strength concept.

7) Floating column: Columns that aren’t directly connected to foundations.[9]

8) Pounding effect in building: Pounding occurs when the adjacent buildings start vibration out of phase during the seismic activity which causes collision amongst the adjacent buildings.[10] This is the situation in which one building gets collided with the other building generating an extra force during lateral displacement.

Mid-column effect: When storey-level of two building are different. It can damage the column. It is floor to column collision. Otherwise, the collision would be floor to floor which isn’t a critical situation as the former.

Tailer adjacent building pounding: It occurs when one building is taller than the other. In the taller building, there is hence generation of extra moment which leads to severe damage of the taller one.

In case of two identical buildings, there is no pounding effect because of identical behaviour under earthquake force.

Eccentric pounding: When a building forms a couple with C.G. of another building. This happens basically when two buildings are in perpendicular orientation with respect to each other.[11]  

9) Short-Column effect: Short column is stiffer than long column. It deflects more than the long under the lateral force. Since, stiffer element attracts more force, the short column collapse quickly than the long column.[12]

10) Liquefaction: Three factors required for its occurrence are: loose granular sediment, water saturated sediment and strong shake. Earthquake waves cause water pressure to increase in sediment. Sand grains loose contact with each other leading to loss of sediment strength and liquid-like behaviour.[13] Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes.[14] It is defined as “transformation of solid to a liquefied state as a consequence of increased pore water pressure and reduced effective stress. Increased pore pressure is caused by tendency of granular material to compact when subjected to cyclic loading.[15] Kathmandu valley has been established as being under high risk of liquefaction hazard during several studies by previous researchers. Eyewitness accounts and visitors log during the 1934 Nepal-Bihar earthquake mentions observations that may be attributed to liquefaction related phenomena. Furthermore, sand boils were observed at various places in Kathmandu valley during the 2015 Gorkha earthquake as well.   

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[1] premjit, “What Is Soft Storey & Weak Storey?,” Civilera, last modified May 20, 2021, accessed October 29, 2024, https://www.civilera.com/post/what-is-soft-storey-weak-storey.

[2] Ibid.

[3] “Weak Storey and Soft Storey in Building”  #Gate 2021#interview Question#earthquake, 2021, accessed October 29, 2024, https://www.youtube.com/watch?v=88BlCyILZOE.

[4] “Stiffness And Strength - Know About It Completely,” last modified June 16, 2020, accessed October 29, 2024, https://thestructuralblog.com/stiffness-and-strength/.

[5] premjit, “What Is Soft Storey & Weak Storey?”

[6] “Stiffness And Strength - Know About It Completely.”

[7] Ibid.

[8] “Weak Storey and Soft Storey in Building”  #Gate 2021#interview Question#earthquake.

[9] Ibid.

[10] Muhammad Noman et al., “Effects of Pounding on Adjacent Buildings of Varying Heights during Earthquake in Pakistan,” Cogent Engineering (December 31, 2016), accessed November 6, 2024, https://www.tandfonline.com/doi/abs/10.1080/23311916.2016.1225878.

[11] “Pounding Effect in Building” | #Gate 2021#interview Question #earthquake, 2021, accessed November 6, 2024, https://www.youtube.com/watch?v=olkje5WijmY.

[12] Short Column Effect || Example Solved, 2019, accessed November 6, 2024, https://www.youtube.com/watch?v=DmF1KuF6lT0.

[13] Liquefaction San Francisco, 1906 Earthquake [Educational], 2011, accessed November 6, 2024, https://www.youtube.com/watch?v=qmVYbjiNWds.

[14] “What Is Liquefaction? | U.S. Geological Survey,” accessed November 6, 2024, https://www.usgs.gov/faqs/what-liquefaction.

[15] Ashish Bastola and Indra Prasad Acharya, “Liquefaction Susceptibility Mapping of Kathmandu Valley” (2016).