The analysis of trusses

A truss: A truss is a structure made of two force members all pin connected to each other.

The method of joints: This method uses the free-body-diagram of joints in the structure to determine the forces in each member. For example, in the above structure we have 5 joints each having a free body diagram as follows

Note how Newton’s third law controls how one introduces on the joints A and on the joint B. For each joint one can write two equations (). The moment equation is trivially satisfied since all forces on a joint pass trough the joint. For example, for the above truss we have 5 joints, therefore we can write 10 equations of equilibrium (two for each joint). In the above example there are seven unknown member forces (F_AB, F_BC, F_CD, F_ED, F_EC, F_BE, F_AE) plus three unknown support reactions (A, D_x, D_y), giving a total of 10 unknowns to solve for using the 10 equations obtained from equilibrium.

The method of sections: This method uses free-body-diagrams of sections of the truss to obtain unknown forces. For example, if one needs only to find the force in BC, it is possible to do this by only writing two equations. First, draw the free body diagram of the full truss and solve for the reaction at A by taking moments about D. Next draw the free body diagram of the section shown and take moments about E to find the force in BC.

In the method of sections one can write three equations for each free-body-diagram (two components of force and one moment equation).

Things to consider:

· Zero force members: Some members in a truss cannot carry load. These members are called zero force members. Examples of zero force members are the colored members (AB, BC, and DG) in the following truss.

Consider the following free-body-diagrams

If you sum the forces in the y-direction in the left free-body-diagram, you will see that F_AB must be zero since it is not balanced by another force. Then if you sum forces in the y-direction you will find that F_BC must also be zero. If you sum the forces in the y direction in the right free-body-diagram, you will see that F_DG must be zero since it is not balanced by another force.

· A redundant joint: Sometimes a joint is redundant. For example, in the following free-body-diagram the load is directly transmitted from each member to the one opposite it without any interaction.

By summing forces along the y-direction one will get F₂=F₄, and by summing forces along the Y‑direction one will get F₁=F₃.

· Redundant members: Sometimes a structure contains one or more redundant members. These members must be removed from the truss, otherwise one will have an insufficient number of equations to solve for the unknown member forces. Slender members are not very useful in compression since they buckle and, as a result, lose their load carrying capability. For example, in the following truss one of the two members AC or BD is redundant. To solve the problem, we remove member BD which will go into compression as a result of the applied loading (i.e., the diagonal AC will have to increase in length and the diagonal BD will have to decease in length for the structure to bend to the right). If we did not remove this member we would have 9 unknowns (five member loads and four support reactions) and only 8 equations (two for each joint).

· Mechanisms: Sometimes there is too much freedom in a structure. For example, the following structure cannot carry any load since it will collapse under the load.

· Curved members: Remember that the two forces acting on a two-force-member are along the line connecting the two points on which the loads are applied.

kuliyyah kami..(KULIYYAH OF ENGINEERING)

cuti-cuti malaysia..

view la page cuti.com.my untuk dapatkan harga murah sempena cuti sekolah nnt yer..

Pengajaran untuk students..tonton la KAMI =P

Teenage movie “KAMI” follows a group of five friends as they squeeze in as much fun and reckless abandonment on their road to self-discovery before entering a new stage in their lives – higher education.

Lynn is a form five student who juggles her studies while helping her mother at their food stall and hangs out with Ali,Abu, Sofie, and Adii. Although they have made her part of their circle, Lynn is holding back a dark past from her buddies. Unknown to them Lynn and her mother had moved from their small town home to start afresh in the city away from a persistent small-time drug dealer, Boy, whom Lynn used to run errands for to gain extra pocket money.

To complicate matters, Lynn writes under the pseudonym Teka Teki for her own, well known fanzine called KAMI and has recently contributed a scathing write-up on Ali’s band in a local music magazine.

As she struggles to keep her secrets under wraps, Lynn soon learns that they are all hiding something from each other.

Renungan...(Darwin yang cerdik tapi bodoh..)

IF DARWIN HAD KNOWN ABOUT DNA

Too small to be seen with the naked eye, DNA serves as the data bank of our cells. Information about all the living things around you is concealed within this miniaturized data bank inside every cell of every organism. All the structural characteristics of a rose, an orange, a sparrow, a tiger or a human being are present in the nuclei of the cells that comprise these organisms. Look at your hand that is holding this book. These data stores exist in the nucleus of every single one of the cells that compose that hand.

These DNA molecules are invisible to the naked eye but in terms of their contents and data-storage capacity, they are equal to a library consisting of tens of thousands of books. As you observe the miraculous aspects of DNA, which we can be seen only by magnifying it thousands of times, you will also appreciate how such this minute essential component of life places the theory of evolution in an insuperable quandary. Examining the details of this extraordinary structure will give you the opportunity to ponder the infinite might, incomparable knowledge, scope and dominion of our Lord, Allah (God) and the universe He has created.

However, at the time when Darwin launched his theory, the level of science was extremely backward. Not even the basic structure of the cell had been revealed, let alone the discovery of the helix structure and data capacity of the DNA molecule, which James Watson and Francis Crick revealed nearly 100 years after the publication of Darwin’s book The Origin of Species. Darwin had no means of foreseeing the advances that molecular biology would subsequently make. Clearly, his theory of evolution built on fundamentally flawed knowledge and hypotheses cannot account for the existence of a structure like DNA, which amazes scientists.

Hayati maksud ayat-ayat Al-quran di bawah..

Dan kesejahteraan semoga dilimpahkan kepadaku, pada hari aku dilahirkan, pada hari aku meninggal dan pada hari aku dibangkitkan hidup kembali"". (QS. 19:33)

Dengan menyebut nama Allah Yang Maha Pemurah lagi Maha Penyayang ¹. (QS. 1:1)

Segala puji ² bagi Allah, Rabb semesta alam ³, (QS. 1:2)

Maha Pemurah lagi Maha Penyayang. (QS. 1:3)

Yang menguasai ⁴ hari pembalasan ⁵. (QS. 1:4)

Hanya kepada Engkaulah kami menyembah ⁶ dan hanya kepada Engkaulah kami mohon pertolongan ⁷. (QS. 1:5)

Tunjukilah ⁸ kami jalan yang lurus, (QS. 1:6)

(yaitu) jalan orang-orang yang telah Engkau anugerahkan ni'mat kepada mereka; bukan (jalan) mereka yang dimurkai dan bukan (pula jalan) mereka yang sesat ⁹. (QS. 1:7)

1. Demi (buah) Tin dan (buah) Zaitun ¹⁵⁸⁸, (QS. 95:1)
2. dan demi bukit Sinai ¹⁵⁸⁹, (QS. 95:2)
3. dan demi kota (Mekah) ini yang aman, (QS. 95:3)
4. Sesungguhnya Kami telah menciptakan manusia dalam bentuk yang sebaik-baiknya. (QS. 95:4)
5. Kemudian Kami kembalikan dia ke tempat yang serendah-rendahnya (neraka), (QS. 95:5)
6. kecuali orang-orang yang beriman dan mengerjakan amal saleh; maka bagi mereka pahala yang tiada putus-putusnya. (QS. 95:6)
7. Maka apakah yang menyebabkan kamu mendustakan (hari) pembalasan sesudah (adanya keterangan-keterangan) itu? (QS. 95:7)
8. Bukankah Allah Hakim yang seadil-adilnya? (QS. 95:8)

muke2 dak stady..ahaks..