RCD 01 - Introduction to Reinforced Concrete Design

00:48:15
https://www.youtube.com/watch?v=Bfbuadb84fA

摘要

TLDRThe video introduces the principles of reinforced concrete design, explaining that concrete is a mixture of aggregates held together by a binder, typically Portland cement. It highlights the importance of steel reinforcement in providing tensile strength to concrete, which is weak in tension. The advantages of reinforced concrete include high compressive strength, resistance to fire and water, low maintenance, and long service life. However, it also has disadvantages such as low tensile strength and the need for expensive forms. The video discusses the curing process, the stress-strain relationship of concrete, and the properties of both concrete and steel. It covers design methods, structural elements like beams, columns, and slabs, and emphasizes the importance of safety and serviceability in structural design.

心得

  • 🏗️ Reinforced concrete combines concrete and steel for strength.
  • 💧 Curing is essential to prevent cracking in concrete.
  • 🔩 Steel reinforcement compensates for concrete's weak tensile strength.
  • 📏 One-way slabs bend in one direction; two-way slabs in two.
  • 🔥 Reinforced concrete is fire and water resistant.
  • 🔨 Concrete is low maintenance compared to other materials.
  • 📊 The stress-strain relationship is crucial for understanding concrete behavior.
  • 🧱 Structural elements include beams, columns, and slabs.
  • ⚖️ Safety and serviceability are key in structural design.
  • 📐 Design methods include working stress and ultimate strength design.

时间轴

  • 00:00:00 - 00:05:00

    The lesson introduces reinforced concrete design, defining concrete as a mixture of aggregates held together by a binder like Portland cement. It explains that reinforced concrete combines concrete and steel to enhance tensile strength, as concrete is weak in tension. The advantages of reinforced concrete include high compressive strength, resistance to fire and water, low maintenance, and long service life, making it suitable for massive structures.

  • 00:05:00 - 00:10:00

    The discussion continues on the versatility of concrete, which can be cast into various shapes and is made from locally sourced materials. It highlights the lower skill level required for labor compared to structural steel, making concrete construction more accessible. However, it also notes disadvantages such as low tensile strength, the need for expensive forms, and the heavy weight of concrete structures, which can complicate long-span designs.

  • 00:10:00 - 00:15:00

    The lesson covers the properties of concrete, emphasizing the importance of the water-cement ratio for strength and the curing process to prevent moisture loss. It explains the stress-strain relationship of concrete, detailing the proportional limit, elastic limit, and ultimate compressive strength, along with the significance of design codes in ensuring structural integrity.

  • 00:15:00 - 00:20:00

    The properties of steel are introduced, including the evolution of reinforcement bars from plain to deformed bars for better bonding with concrete. The lesson discusses the importance of placing reinforcement where concrete is weak in tension and outlines the different sizes and grades of steel bars used in construction, including yield points and color coding for identification.

  • 00:20:00 - 00:25:00

    Structural elements such as beams, columns, and slabs are defined, with beams primarily designed to resist bending moments. The lesson explains the types of beams and their classifications based on support conditions, as well as the importance of understanding elastic and plastic deformations in structural design.

  • 00:25:00 - 00:30:00

    The discussion on beams continues, explaining flexural and shear cracks, their origins, and the implications for structural integrity. It also covers columns as vertical elements that resist compressive loads, detailing the role of ties in preventing buckling and the importance of proper spacing for reinforcement bars.

  • 00:30:00 - 00:35:00

    The lesson introduces slabs as horizontal panels that support floors, explaining the difference between one-way and two-way floor systems. It describes how loads are transferred to supporting beams and columns, emphasizing the design considerations for each type of slab system based on their support conditions and load distribution.

  • 00:35:00 - 00:48:15

    The presentation concludes with a summary of the key concepts discussed, inviting questions and comments from the audience to clarify any uncertainties regarding reinforced concrete design principles.

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思维导图

视频问答

  • What is reinforced concrete?

    Reinforced concrete is a combination of concrete and steel, where steel reinforcement provides tensile strength to the concrete.

  • What are the advantages of reinforced concrete?

    Reinforced concrete has high compressive strength, resistance to fire and water, low maintenance, and a long service life.

  • What are the disadvantages of reinforced concrete?

    Disadvantages include low tensile strength, the need for expensive forms, heavy members, and variations in concrete properties.

  • What is the curing process for concrete?

    Curing involves maintaining moisture in concrete to prevent cracking and strength loss, often by wetting the surface or submerging specimens.

  • What are the main structural elements in reinforced concrete design?

    Main structural elements include beams, columns, and slabs, which support loads and transfer forces.

  • What is the difference between one-way and two-way slabs?

    One-way slabs bend in one direction and are supported on two sides, while two-way slabs distribute loads in two directions.

  • What is the role of steel reinforcement in concrete?

    Steel reinforcement compensates for concrete's low tensile strength, allowing it to handle tension forces.

  • What is the stress-strain relationship of concrete?

    The stress-strain relationship describes how concrete behaves under load, including proportional limits and ultimate strength.

  • What are the common types of reinforcement bars?

    Common types include longitudinal bars (rebars) and prestressed steel, which enhance tensile strength.

  • What is the importance of serviceability in structural design?

    Serviceability ensures that structures remain functional and comfortable for users, minimizing issues like vibrations and cracking.

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  • 00:00:01
    Hello everyone. Welcome to the first
  • 00:00:04
    lesson about the principles of reinforce
  • 00:00:07
    concrete design.
  • 00:00:10
    First ting
  • 00:00:12
    what is the definition of reinforced
  • 00:00:15
    concrete.
  • 00:00:20
    So of course concrete unahin natin no
  • 00:00:23
    concrete is a mixture of sand, gravel,
  • 00:00:26
    crush rock or other aggregate. So ang
  • 00:00:28
    division nito is it could be a course
  • 00:00:31
    aggregate or a fine aggregate. And they
  • 00:00:34
    are held together with a into a rocklike
  • 00:00:37
    mass.
  • 00:00:39
    with the pace of binder. Now, iyung
  • 00:00:40
    binder natin, it could be Portland
  • 00:00:43
    cement or asphalt cement. So, we have
  • 00:00:46
    Portland cement concrete and we also
  • 00:00:48
    have asphalt cement concrete. Now, dito
  • 00:00:51
    sa image, it's using cement. At pagland
  • 00:00:54
    cement yung gamit natin, this is
  • 00:00:56
    activated by water. So, magre-react
  • 00:00:59
    iyung water doon sa cement para
  • 00:01:01
    mag-harden siya.
  • 00:01:03
    Sometimes also if you can look here we
  • 00:01:07
    add what we call add mixtures to change
  • 00:01:10
    yung certain characteristics ng concrete
  • 00:01:12
    such as yung workability niya,
  • 00:01:14
    durability or yung time of hardening.
  • 00:01:22
    Now what is reinforced concrete?
  • 00:01:24
    Reinforced concrete is a combination of
  • 00:01:26
    concrete and steel wherein the steel
  • 00:01:30
    reinforcement provides stencil strength
  • 00:01:32
    locking in the concrete. Kasi iyung
  • 00:01:34
    concrete natin no, ah concrete is
  • 00:01:37
    actually very weak in tensil or tension
  • 00:01:41
    stresses. That's why we provide
  • 00:01:44
    additional support para doon sa tension
  • 00:01:46
    forces natin. So ito for example we have
  • 00:01:50
    a beam which is made up of plane
  • 00:01:52
    concrete. So if you push it with the
  • 00:01:54
    load no P
  • 00:01:57
    iyung bottom nung beam will have tension
  • 00:02:00
    forces. So magka-crack siya doon because
  • 00:02:03
    concrete cannot actually handle a lot of
  • 00:02:06
    tensil stresses. So magka-crack siya
  • 00:02:09
    doon. So ang ginagawa natin, we
  • 00:02:11
    reinforce it. We introduce a
  • 00:02:13
    reinforcement steel do sa ilalim to
  • 00:02:16
    handle those tension forces. So ito yung
  • 00:02:19
    reinforce concrete.
  • 00:02:22
    We have several advantages ng reinforced
  • 00:02:25
    concrete. One of those advantages is
  • 00:02:28
    that it has considerable compressive
  • 00:02:30
    strength. So kung mahina man siya sa
  • 00:02:32
    tension ah we have to know na we have to
  • 00:02:36
    understand that iyung concrete is
  • 00:02:39
    actually very strong in compression. So
  • 00:02:42
    yung iyung concrete natin at saka iyung
  • 00:02:45
    steel bars they complement each other
  • 00:02:47
    kasi iyung concrete malakas sa
  • 00:02:48
    compression iyung steel natin malakas sa
  • 00:02:52
    ah tension. Okay. So, one of the
  • 00:02:54
    advantages
  • 00:02:56
    compared doon sa unit cause niya,
  • 00:02:59
    maganda yung compressive strength ng
  • 00:03:00
    rainforce concrete. Also, it has great
  • 00:03:04
    resistance to the actions of fire and
  • 00:03:06
    water. In fact, it's the best material
  • 00:03:09
    available for situations where water is
  • 00:03:12
    present. So ano bang ibang material na
  • 00:03:15
    available? We have wood at saka
  • 00:03:16
    structural steel, no? So, si wood in
  • 00:03:19
    presence of water, nagkakaroonya ng
  • 00:03:21
    molds. Nagra-rut siya. si steel of
  • 00:03:24
    course kung kung mga water applications
  • 00:03:26
    kakalawangin now reinforce concrete. Si
  • 00:03:30
    concrete no ah acts as a protection of
  • 00:03:34
    protective cover doon sa mga steel bar
  • 00:03:37
    sa loob niya. Reinforce concrete
  • 00:03:40
    structures are very rigid. When we say
  • 00:03:42
    very rigid, ibig sabihin ah it's not
  • 00:03:47
    swaying much, no? Hindi siya masyadong
  • 00:03:50
    nagsu-sway lalo na versus lateral
  • 00:03:54
    forces. That's why one of the best
  • 00:03:56
    systems na ginagamit natin to counteract
  • 00:03:59
    lateral forces is yung tinatawag na uh
  • 00:04:02
    reinforce concrete sheer walls because
  • 00:04:05
    those are very rigid walls and very good
  • 00:04:10
    when there are lateral forces present.
  • 00:04:15
    It is a low maintenance material. We do
  • 00:04:17
    not need to repaint or to to protect it
  • 00:04:22
    against rusting ' ba. Yun yung
  • 00:04:24
    nangyayari kapag mga steel structures
  • 00:04:26
    you have to maintain it against yung mga
  • 00:04:29
    rust. Si concrete. If if you do it
  • 00:04:32
    right, if you maganda yung pagkakaw
  • 00:04:36
    natin, makinis yung yung mga sides niya,
  • 00:04:40
    it won't have a high maintenance cost.
  • 00:04:44
    As compared with other materials, it has
  • 00:04:47
    a very long service life. Okay? And it
  • 00:04:51
    is usually the only economical material
  • 00:04:53
    available para sa mga putings, slabs,
  • 00:04:56
    basements, and other applications kung
  • 00:04:59
    saan the structure is very massive, no?
  • 00:05:02
    If even you have a very massive volume
  • 00:05:05
    of structures, automatic concrete iyung
  • 00:05:08
    ginagamit natin. We don't do for example
  • 00:05:11
    footings. We don't do a lot of steel
  • 00:05:15
    footings no or wala atang ganon no meron
  • 00:05:20
    siguro yung mga steel piles pero usually
  • 00:05:23
    concrete talaga ang ginagamit. Now a
  • 00:05:26
    special feature of concrete of course is
  • 00:05:29
    the ability to be cast into different
  • 00:05:32
    shapes. So simple slabs, beam columns.
  • 00:05:35
    Pwede mo siyang i-shape as arches,
  • 00:05:38
    shells, no? Yung mga shell structures,
  • 00:05:40
    mga naka-curve na na mga shape. Kasi the
  • 00:05:44
    shape of the reinforced concrete
  • 00:05:46
    structure will be based
  • 00:05:49
    na gagamitin natin. Tapos ah kumbaga
  • 00:05:52
    liquid kasi siya nilalagay ' ba. And
  • 00:05:55
    then we will uh wait for it to cure at
  • 00:05:58
    mag-harden to take the shape of whatever
  • 00:06:01
    is the form na ginamit natin. In most
  • 00:06:05
    areas, concrete takes advantages of or
  • 00:06:08
    advantage of inexpensive local material.
  • 00:06:11
    So what are the local materials? You
  • 00:06:13
    have sand, gravel, and of course the
  • 00:06:16
    water used para mag-react doon sa
  • 00:06:18
    Portland cement. So madali siyang kunin.
  • 00:06:23
    You don't need to mine yung katutulad sa
  • 00:06:25
    steel 'di ba? You have to mine yung
  • 00:06:27
    steel orses to refine it para magkaroon
  • 00:06:30
    ka ng steel structure. So usually yung
  • 00:06:33
    mga steel steel natin sa Pilipinas we
  • 00:06:35
    import them uh from other countries.
  • 00:06:39
    Now, pagdating naman sa wood, we don't
  • 00:06:43
    need to chop trees. 'Di ba in in dito sa
  • 00:06:49
    atin kasi wala na tayong ano no, yung
  • 00:06:51
    mga forest nakakalbo na so mahirap. So
  • 00:06:55
    ito madaling iano i-source yung material
  • 00:07:00
    ng concrete. Okay? And a lower grade of
  • 00:07:05
    skilled labor is required for the
  • 00:07:07
    erection compared with other material
  • 00:07:09
    such as structural steel. So
  • 00:07:11
    buhos-buhos, sainta-sinta and then
  • 00:07:14
    that's it. Pag sa structural steel kasi
  • 00:07:17
    ah lalo na yung mga talagang malalaking
  • 00:07:20
    structure you have to have skilled labor
  • 00:07:23
    para doun sa mga welding non. Hindi yun
  • 00:07:25
    spot spot welding lang. Okay. So, mas
  • 00:07:29
    madali siyang ah gawin ng mga labor
  • 00:07:34
    natin.
  • 00:07:36
    Now, of course, there are also
  • 00:07:38
    disadvantages when using reinforced
  • 00:07:41
    concrete. One of that is that concrete
  • 00:07:44
    has very low tensil strength which
  • 00:07:47
    requires the use of tensil reinforcing.
  • 00:07:50
    Of course, uh this is a disadvantage and
  • 00:07:53
    also somewhat an advantage kasi
  • 00:07:57
    still actually uh
  • 00:08:00
    compliments no iyung concrete natin. So
  • 00:08:02
    you are still forced to use a steel
  • 00:08:04
    material. Okay? Ah hindi lang purong
  • 00:08:07
    concrete. Forms which are expensive are
  • 00:08:10
    required to hold the concrete in place
  • 00:08:12
    until it hardens efficiently. Ah ibig
  • 00:08:15
    sabihin
  • 00:08:17
    when when you do a concrete structure
  • 00:08:19
    pag nilagay mo yung yung beam mo yung
  • 00:08:21
    concrete beam mo hindi siya agad agad
  • 00:08:23
    nagagamit you have to wait for it to
  • 00:08:26
    attain a certain level of strength ba
  • 00:08:28
    yung mga 7 14 days strength na alam
  • 00:08:31
    natin no and bago mo mapatungan ng load
  • 00:08:37
    yung structure natin okay so you have
  • 00:08:42
    to to wait for it to cure.
  • 00:08:45
    before the members gain sufficient
  • 00:08:47
    strength to support themselves.
  • 00:08:50
    Number it has low strength per unit of
  • 00:08:53
    weight of concrete so it leads to heavy
  • 00:08:56
    members. So concrete structures are
  • 00:08:58
    heavier than structural steel
  • 00:09:02
    members dahil massive yung mga volume
  • 00:09:05
    nila, malalaki yung members. And this
  • 00:09:08
    becomes a constraint no when you want to
  • 00:09:11
    do long span structures.
  • 00:09:14
    Uh yung concrete is heavy. It's large.
  • 00:09:18
    It has large dead weight. No, this this
  • 00:09:21
    should be weight.
  • 00:09:24
    Yan weight
  • 00:09:28
    and has great effect on the bending
  • 00:09:30
    moments kasi nga concrete concrete
  • 00:09:34
    structures are heavy no heavy members
  • 00:09:37
    compared with structural steel. Now
  • 00:09:39
    similarly low strength per unit of
  • 00:09:42
    volume of concrete means members will be
  • 00:09:45
    large relatively large and this is an
  • 00:09:48
    important consideration for tall
  • 00:09:50
    buildings and long span structures. So
  • 00:09:54
    an example of this is when making great
  • 00:09:57
    force concrete beams no uh if you want
  • 00:10:00
    to span 6 meters
  • 00:10:03
    typically a concrete beam would be half
  • 00:10:06
    a meter deep. Okay. Half a meter deep
  • 00:10:10
    and half of that would be yung
  • 00:10:14
    structural steel. So ibig sabihin for to
  • 00:10:17
    span 6 meters si concrete nasa 500 mm
  • 00:10:21
    yyung depth. Pag steel 250 to 300 mm
  • 00:10:24
    lang yung depth. So mas malalaki talaga
  • 00:10:27
    yung concrete members versus sa steel.
  • 00:10:30
    So that's one of the disadvantage.
  • 00:10:35
    Number five, it has something to do with
  • 00:10:37
    the the quality control. Properties of
  • 00:10:41
    concrete vary widely because of the
  • 00:10:43
    variations in proportioning and mixing.
  • 00:10:46
    Furthermore, placing and curing of
  • 00:10:48
    concrete is not as carefully controlled
  • 00:10:51
    as is the production of other material
  • 00:10:53
    such as structural steel and laminated
  • 00:10:57
    wood. Now, dahil yung paggawa ng
  • 00:11:00
    concrete is
  • 00:11:03
    depende sa contractor kung paano nila
  • 00:11:05
    pino-proportion, medyo mas may varation
  • 00:11:08
    yung ano no mga properties nito. For
  • 00:11:10
    example, you can specify sa structural
  • 00:11:13
    design mo na 28 megapascal or 4,000 PSI
  • 00:11:16
    yung strength. In actual, it won't be 28
  • 00:11:20
    megapal. It won't be 4,000. It could be
  • 00:11:23
    lower or higher. No, but we accept that.
  • 00:11:27
    For example, 4,000 PSI ang specification
  • 00:11:31
    and it comes out na naging 4,500, 4,700,
  • 00:11:35
    4,200
  • 00:11:37
    we will still accept that because 4,000
  • 00:11:40
    yung minimum specs natin. But if if you
  • 00:11:44
    look at it from the point of view of
  • 00:11:46
    efficiencyo, parang yyung 4,700 masyado
  • 00:11:50
    ng mataas kaysa sa 4,000
  • 00:11:52
    but it's still good. Okay yun medyo mas
  • 00:11:58
    malaki lang iyung variation nung nung
  • 00:12:00
    concrete ah strength.
  • 00:12:05
    Okay. Now, let's go sa concrete and
  • 00:12:07
    steel. Ah in this in this part of our
  • 00:12:11
    lesson, we will talk about the different
  • 00:12:13
    properties of concrete and the different
  • 00:12:15
    properties of steel.
  • 00:12:19
    Unahin natin si concrete class. So
  • 00:12:22
    concrete is made by mixing cement and
  • 00:12:25
    water. This is true for hydraulic
  • 00:12:27
    cements. Okay. We need to use water para
  • 00:12:33
    mag-activate yung hydraulic cement.
  • 00:12:36
    Okay. Use in binding the aggregates
  • 00:12:38
    which are sun and gravel which are the
  • 00:12:41
    fine and c aggregates.
  • 00:12:44
    The water cement ratio greatly affects
  • 00:12:47
    the strength of concrete.
  • 00:12:51
    We want a lower water cement ratio. But
  • 00:12:54
    unfortunately if if the
  • 00:12:58
    water is less no kung onti lang yung
  • 00:13:00
    tubig na ginamit mo, the concrete mix
  • 00:13:03
    will not be workable. Mahirap siya
  • 00:13:05
    i-form pero pag napasobra ka naman ng
  • 00:13:08
    tubig humihina yung strength.
  • 00:13:11
    Okay. Now we also have the curing of
  • 00:13:14
    concrete. Curing is performed by
  • 00:13:16
    submerging the specimen underwater. This
  • 00:13:19
    is done to prevent moisture loss. Kasi
  • 00:13:23
    rapid moisture loss leads to cracking
  • 00:13:25
    and loss of strength of concrete
  • 00:13:27
    specimen. So if you can remember sa
  • 00:13:30
    ating materials testing class no sa
  • 00:13:32
    construction materials and testing
  • 00:13:35
    we built concrete specimens cylinders
  • 00:13:39
    and nilulubog iyun sa tubig no we are
  • 00:13:42
    curing the concrete. In actual you
  • 00:13:44
    cannot do that ' ba sa mga bahay sa mga
  • 00:13:47
    structure sa mga building. You you
  • 00:13:49
    cannot cure the concrete building by
  • 00:13:52
    submerging everything in water. So in
  • 00:13:55
    actual ang ginagawa ah during the
  • 00:13:58
    crewing process we we
  • 00:14:00
    [Musika]
  • 00:14:02
    wet the surface of of the forms no
  • 00:14:05
    dinidiligan yung yung mga slabs yung mga
  • 00:14:08
    pader.
  • 00:14:10
    Wini-wisikan ka ng tubig iyan every now
  • 00:14:12
    and then to make sure that there will be
  • 00:14:15
    no moisture loss. And one of the things
  • 00:14:18
    that not mentioned here is you know
  • 00:14:21
    iyung one of the purposes of of
  • 00:14:23
    submerging in water or iyung pagwipisik
  • 00:14:26
    ng tubig sa site is that we are also
  • 00:14:29
    controlling the temperature because
  • 00:14:32
    iyung reaction nung cement doon sa water
  • 00:14:36
    it is ah I think it's called exothermic
  • 00:14:39
    no it it releases heat no meron tayong
  • 00:14:42
    tinatawag na heat of hydration and if
  • 00:14:44
    you if you do not control that release
  • 00:14:47
    of heat it would
  • 00:14:51
    it would accelerate the moisture loss
  • 00:14:54
    okay and th
  • 00:14:58
    iina yyung concrete specimen natin.
  • 00:15:00
    Okay? So yun yung ginagawa no? Meron
  • 00:15:04
    tayong process na tinatawag na curing of
  • 00:15:06
    concrete.
  • 00:15:12
    Now let's look at the stress rain
  • 00:15:14
    relationship of concrete. So stress
  • 00:15:17
    strain relationship relationship will
  • 00:15:20
    tell us or or is one of the basic
  • 00:15:24
    mechanical properties of materials. So
  • 00:15:26
    ito iyung stress strain graph natin.
  • 00:15:28
    Yung strain natin would be nasa baba and
  • 00:15:32
    then yung stress sa taas. So first is
  • 00:15:36
    pag tinesting mo yung concrete you will
  • 00:15:38
    reach some kind of limit. We call it the
  • 00:15:41
    proportional limit. This is the limit
  • 00:15:44
    where the stress and strain are
  • 00:15:46
    proportional. So we connect it with a
  • 00:15:48
    straight line. Now
  • 00:15:51
    after that we will reach what we call
  • 00:15:53
    the elastic limit. This is the limit
  • 00:15:55
    kung saan if you remove the load yung
  • 00:15:58
    strain ko will go back to zero. No
  • 00:16:01
    problem. Okay? Pero beyond that,
  • 00:16:03
    magkakaroon ako ng tinatawag na
  • 00:16:05
    permanent deformations. So in this
  • 00:16:08
    region, we call this the elastic region.
  • 00:16:11
    Ah meron tayong hooks law that the
  • 00:16:13
    stress is directly proportional to
  • 00:16:15
    strain up to the proportionality limit
  • 00:16:17
    hanggang dito. So yung hooks law natin
  • 00:16:21
    is yung yung proportional
  • 00:16:25
    ah what do you call this? Yung
  • 00:16:27
    proportionality factor natin is the
  • 00:16:30
    modulus of elasticity. So yung stress is
  • 00:16:34
    proportional sa strain and yung constant
  • 00:16:37
    of proportionality
  • 00:16:38
    E is what we call the modulus of
  • 00:16:41
    elasticity. That's basically yung slope
  • 00:16:43
    nitong graph na to. Okay? And then we
  • 00:16:46
    will reach elastic limit. Ah hanggang
  • 00:16:49
    diyan na lang yung limit na na
  • 00:16:54
    after niyan meron ka ng permanent
  • 00:16:56
    deformations.
  • 00:16:57
    And then we will reach the ultimate
  • 00:17:00
    compressive strength. Ito iyung F prime
  • 00:17:02
    CO. The ultimate compressive strength.
  • 00:17:05
    And then of course dito after nitong
  • 00:17:08
    elastic limit meron na tayong nonlinear
  • 00:17:10
    elastic region. And then we have the
  • 00:17:13
    brake point. The braking or the rupture
  • 00:17:16
    point the failure occurs. The concrete
  • 00:17:18
    cracks in tension. So ito yung rupture
  • 00:17:24
    point natin. Okay. Usually yung yung
  • 00:17:27
    maximum strain na to we take it
  • 00:17:32
    in European countries that would be
  • 00:17:34
    0.0035
  • 00:17:37
    3. Okay. 0.0035 sa atin 0.003.
  • 00:17:42
    Okay.
  • 00:17:45
    Now,
  • 00:17:46
    meron tayong design codes. Of course, we
  • 00:17:49
    have the national structural code of the
  • 00:17:51
    Philippines. They provide detailed
  • 00:17:54
    technical standards that are used to
  • 00:17:56
    establish requirements nung actual
  • 00:17:59
    structural design. Nandiyan din
  • 00:18:00
    naka-specify 0.003 003 as the maximum
  • 00:18:03
    strain ng concrete. Ah it should be
  • 00:18:07
    realized however that codes only provide
  • 00:18:12
    guide for design. Okay. Remember yung
  • 00:18:16
    ultimate responsibility will always lie
  • 00:18:19
    with the structural engineer who is also
  • 00:18:22
    the engineer on record who signed the
  • 00:18:25
    calculations and the plans. Nasa nasa
  • 00:18:29
    kanila pa rin itong code na to. minimum
  • 00:18:32
    design standards. You can actually go
  • 00:18:34
    beyond the code or you can go below
  • 00:18:38
    provided that ah you have the
  • 00:18:41
    calculations to support yung yung design
  • 00:18:46
    choices mo
  • 00:18:50
    for the elastic modulus of concrete yung
  • 00:18:52
    e subsecural
  • 00:18:56
    code about this value of subc. So from
  • 00:19:00
    our national structural code 2015 ah we
  • 00:19:04
    have two categories for normal weight
  • 00:19:07
    concrete which is normal weight concrete
  • 00:19:10
    which has a weight of 2,300 kg per cubic
  • 00:19:14
    meter. So this is the density.
  • 00:19:18
    We can assume that the modulus of
  • 00:19:20
    elasticity is 4,700
  • 00:19:23
    lambda s root of f prime c and this a
  • 00:19:26
    subc is in megapascals.
  • 00:19:30
    For other weights naman where WC is not
  • 00:19:34
    2,300
  • 00:19:36
    we have this equation we have the the
  • 00:19:39
    mass density rais to 1.5
  • 00:19:42
    0.043 043 lambda s ro f prim c again
  • 00:19:46
    this values would be in megapascals.
  • 00:19:50
    Yung lambda natin it's a factor
  • 00:19:52
    considered for the type of concrete.
  • 00:19:54
    Usually it's one for normal weight and
  • 00:19:57
    75 naman para sa mga lightweight
  • 00:19:59
    concrete. Light weight is anything below
  • 00:20:02
    2,300 kg per cubic m.
  • 00:20:07
    Now for the ultimate compressive
  • 00:20:09
    strength of concrete, ito yung this is
  • 00:20:11
    the top portion nung ating stress strain
  • 00:20:14
    curve. It is the maximum value na
  • 00:20:18
    pwedeng ma-attain without
  • 00:20:21
    uh breaking the concrete. So for a
  • 00:20:24
    commercially available concrete, this
  • 00:20:26
    are in multiples of uh 7 megapcal
  • 00:20:30
    starting from 17. This would be the
  • 00:20:32
    accepted lowest value. And then we have
  • 00:20:35
    21, 28, 34 and so on. So + 7 ng + 7 to.
  • 00:20:40
    21 megcal corresponds to 3KSI or 3,000
  • 00:20:44
    PSI and then dagdag ka ng 1,000
  • 00:20:48
    or 1KSI or 7 megascal. So we have 28 34
  • 00:20:54
    and so on. So ang conversion factor nito
  • 00:20:58
    actually is 1KSI is 6.896 896 megapcal.
  • 00:21:02
    So sa iba ginagawa na lang na 7 megapal.
  • 00:21:04
    So 1 ksi is 7 megapal. But anyway, here
  • 00:21:09
    is the more accurate conversion factor.
  • 00:21:15
    Now for the design and analysis of
  • 00:21:17
    reinforced concrete uh we have first is
  • 00:21:20
    what we call the working stress design
  • 00:21:22
    method.
  • 00:21:24
    Uh the assumption is that the concrete
  • 00:21:28
    is linear uh elastic ang kanyang
  • 00:21:31
    behavior. And ibig sabihin
  • 00:21:35
    ah the consideration is hanggang doon
  • 00:21:37
    lang sa proportional limit. So pag
  • 00:21:39
    sinabing linear elastic doon lang tayo
  • 00:21:41
    sa proportional limit d sa graph kanina.
  • 00:21:44
    For ultimate strength design method
  • 00:21:46
    naman the behavior of concrete is
  • 00:21:49
    nonlinear. So lalampas tayo doon sa
  • 00:21:52
    proportional limit.
  • 00:21:53
    Okay, this is considered hanggang doon
  • 00:21:56
    sa ultimate strength. So this two
  • 00:21:58
    methods are the design methods used sa
  • 00:22:03
    pagde-design ng concrete. Actually USD
  • 00:22:05
    has is the main method of design sa
  • 00:22:08
    reinforce concrete. USD ultimate strent
  • 00:22:11
    design because it it just makes sense no
  • 00:22:13
    na na you would be considering yung
  • 00:22:16
    ultimate strength at hindi mo i-limit
  • 00:22:18
    yyung sarili mo doon sa proportionality
  • 00:22:20
    limit. But still working stress design
  • 00:22:23
    is still used today uh in particular sa
  • 00:22:28
    mga ano structures that retain water or
  • 00:22:31
    has
  • 00:22:33
    water
  • 00:22:35
    feature na na kailangan mong i-limit
  • 00:22:38
    yung mga cracking para hindi mag
  • 00:22:41
    magkaroon ng mga leak no mga water tank
  • 00:22:45
    na concrete. Most of them are still
  • 00:22:47
    designed are still designed using
  • 00:22:50
    working stress design. Okay.
  • 00:22:54
    Now other properties of concrete we have
  • 00:22:57
    shrinkage and crip. Shrinkage this is
  • 00:23:00
    the contracting of harden concrete due
  • 00:23:02
    to loss of water and moisture. Ah
  • 00:23:05
    shrinkage temperature bars are used. So
  • 00:23:09
    yung mga rebar natin is not just for the
  • 00:23:13
    tension stresses but also to prevent
  • 00:23:17
    itong excessive cracking because of the
  • 00:23:19
    contraction of concrete. Okay? Shrink
  • 00:23:23
    cage. So that's that's why yung
  • 00:23:25
    temperature bar shrinkage temperature
  • 00:23:27
    bars we also call it or I like to refer
  • 00:23:30
    to it as shrinkage and temperature
  • 00:23:34
    control bars. So controlling this
  • 00:23:37
    phenomena.
  • 00:23:38
    We also have creep. This is the
  • 00:23:40
    additional deformation because of the
  • 00:23:42
    load applied for a very long time. So
  • 00:23:45
    when when you have a very long
  • 00:23:49
    time of load application, creep happens,
  • 00:23:53
    nagre-rearrange yyung ano yung mga
  • 00:23:55
    particles ng concrete. Nagkakaroon ng
  • 00:23:57
    permanent deformation. So this is an
  • 00:23:59
    example of a bridge that has experienced
  • 00:24:03
    crif deflection. So makikita niyo
  • 00:24:05
    pagdating dito hindi napantay yung
  • 00:24:06
    bridge. Nag-lower down na siya dito. And
  • 00:24:10
    it's it's not because mahina yung
  • 00:24:12
    konkreto.
  • 00:24:14
    It's not because uh na-overload. If you
  • 00:24:18
    look at it, there's no truck sa taas.
  • 00:24:22
    But it's it's quite something like the
  • 00:24:25
    secondary consolidation sa soil no na
  • 00:24:29
    due time overtime concrete wood would
  • 00:24:32
    have this permanent deformations.
  • 00:24:38
    Now for the steel we have longitudinal
  • 00:24:40
    bars. Ito yung tinatawag natin na rebar.
  • 00:24:44
    Uh noon they use plane bars which has
  • 00:24:48
    smooth surface but it failed kasi hindi
  • 00:24:52
    siya kumakapit sa konkreto. So after
  • 00:24:55
    that they introduce yung deformations
  • 00:24:59
    doon sa bar. Ah before we have this kind
  • 00:25:02
    of bar ito yyung may mga rides and logs
  • 00:25:05
    no? Before we had that we have plain bar
  • 00:25:08
    na square tapos tini-twist. Naka-twist
  • 00:25:10
    siya. So para siyang parang ano ah meron
  • 00:25:14
    siyang grooves dahil doun sa pagtu-twist
  • 00:25:16
    nung rectangular bars no. Para siyang
  • 00:25:20
    screw. Okay? But they found out na hindi
  • 00:25:23
    rin siya ganon ka-effective. So
  • 00:25:24
    naimbento itong deform bars which has
  • 00:25:27
    this
  • 00:25:28
    rinches at saka lugs na tinatawag. Okay,
  • 00:25:32
    ito yung mga ridge. Okay, itong itong
  • 00:25:35
    straight sa side, ito yung lugs.
  • 00:25:38
    Okay. Now, we also have prestress steel
  • 00:25:41
    which which would not be part of the
  • 00:25:43
    course, but this are also reinforcement
  • 00:25:47
    bars. But instead of solid reinforcement
  • 00:25:50
    bars na isang buo, these are made up of
  • 00:25:54
    high tension cable wires bundled
  • 00:25:56
    together. Yan, ganyan.
  • 00:25:59
    And then of course sa steel we have yung
  • 00:26:02
    structural steel shapes natin na
  • 00:26:04
    iba-ibang shape.
  • 00:26:07
    Note that reinforcing steel bars are
  • 00:26:10
    place where concrete is weak in tension.
  • 00:26:13
    So we have to know kung saan yung mga
  • 00:26:17
    tension stresses sa concrete at kung
  • 00:26:19
    saan malalaki 'yung tension stresses.
  • 00:26:22
    Doon natin pinupwesto yung yung ating
  • 00:26:24
    mga reinforcement bars kasi siya yung
  • 00:26:27
    magke-carry nung tension o tensil
  • 00:26:29
    stresses na yon.
  • 00:26:33
    So longitudinal bars, yung mga bars,
  • 00:26:35
    reinforcement bars comes in different
  • 00:26:37
    sizes. Actually hindi lang to
  • 00:26:39
    longitudinal basta reinforcement bar sa
  • 00:26:41
    reinforcement sa reinforce concrete
  • 00:26:43
    design. Ito yung mga usual na sizes. We
  • 00:26:47
    have the nominal diameters 10, 12, 16
  • 00:26:51
    hanggang 36 mm meron yan. And then yung
  • 00:26:54
    mga length available usually 6 meters
  • 00:26:57
    yung meron ah depende sa contractor kung
  • 00:27:00
    ano yung pipiliin nila dito na na length
  • 00:27:02
    no kung ano yung mas advantageous sa sa
  • 00:27:05
    kanila or sa inyo kapag kayo naging
  • 00:27:07
    contractor. Ah minsan may nakita na ako
  • 00:27:10
    gumamit ng 12 para wala ng putol no wala
  • 00:27:13
    ng lapping hanggang second floor kasi
  • 00:27:16
    two story lang naman kasya yun 12 sa
  • 00:27:18
    kanya. So you you could actually order
  • 00:27:20
    this. Okay. Uh this is also one of the
  • 00:27:23
    reasons no itong mga nominal length na
  • 00:27:26
    iba-iba. It's one of the reasons kung
  • 00:27:28
    bakit ah actually nasa construction side
  • 00:27:32
    yung ano cutting list. Okay? Kasi
  • 00:27:35
    magagawa mo yung cutting list. One of
  • 00:27:38
    what one of the things na kailangan mo
  • 00:27:41
    sa cutting list is gaano kahaba yung
  • 00:27:43
    oorderin mong bakal alam mo kung ilang
  • 00:27:48
    beses kang magpuputol nung bakal. Okay.
  • 00:27:51
    Now, we also have specified yield points
  • 00:27:54
    ayon sa mga different standards. We have
  • 00:27:57
    ASM.
  • 00:27:59
    Uh this is the I think this is American
  • 00:28:02
    Society for testing materials.
  • 00:28:05
    And then we have PNS. PNS is the
  • 00:28:07
    Philippine National Standard which we
  • 00:28:11
    follow
  • 00:28:13
    no sa NSCP. So for grade 33, ito yung
  • 00:28:17
    ito yung dati ang tawag dito structural
  • 00:28:20
    grade ah yung grade 33 and then we have
  • 00:28:25
    ah grade 40 and then grade 60. So
  • 00:28:29
    structural grade dati to tapos 40 yung
  • 00:28:33
    ano yung
  • 00:28:35
    ah high grade pero iba na ngayon. Wala
  • 00:28:37
    na on'tg ano hindi na dapat tayo gagamit
  • 00:28:40
    nung 33 ngayon no. Ang ginagamit na
  • 00:28:43
    natin, ang ina-accept na itong dalawa 40
  • 00:28:46
    at saka 60. So yung 40, grade 40 o 40
  • 00:28:51
    KSI pag kinonvert mo yan, that would be
  • 00:28:54
    275 megapc. yung 60 that would be 415
  • 00:28:57
    megcals. So from the previous iterations
  • 00:29:01
    ng NSCP, ito yung ito yyung ginagamit na
  • 00:29:05
    megapascals. But I guess they opted to
  • 00:29:08
    use ano ah two two significant figures
  • 00:29:13
    lang sa latest iteration ng code. So
  • 00:29:15
    dahil two significant figures lang
  • 00:29:17
    naging 280 saka 420 siya. Okay. So 280
  • 00:29:22
    saka 420 megapcals.
  • 00:29:25
    Now, paano ia-identify 'to? Ah doon pag
  • 00:29:29
    umorder ka ng bakal meron yang mga
  • 00:29:31
    kulay-kulay doon sa dulo. Pine-paint
  • 00:29:34
    nila. Okay? Usually yung yellow that
  • 00:29:36
    would be 280. Yung green yun yung 420.
  • 00:29:40
    Tapos white naman yung grade 33. Ah
  • 00:29:43
    'yung red ito ay makikita mo doun sa
  • 00:29:46
    kabila no? Sa kabila ah minsan 'yan
  • 00:29:49
    'yung sinasabi nila na weldable versus
  • 00:29:51
    nonweldable na rebars. But anyway ah
  • 00:29:55
    nag-iiba 'to depende doon sa
  • 00:29:57
    pag-o-orderan mo. Depende sa supplier.
  • 00:30:00
    Hindi hindi siya actually standard sa
  • 00:30:02
    atin. So you have to ask your supplier
  • 00:30:05
    baka may iba silang color coding na
  • 00:30:07
    ginagamit. Okay. And aside from that,
  • 00:30:10
    meron din yang mga naka-etch doon sa
  • 00:30:12
    side nung bakal para malaman mo kung ano
  • 00:30:15
    yung grade nung bakal.
  • 00:30:18
    Okay.
  • 00:30:21
    Now, para naman sa steel. So kanina we
  • 00:30:23
    we talk about the different properties
  • 00:30:26
    of ah iyung concrete no? Yung stress
  • 00:30:29
    strain relationship ng concrete. Now
  • 00:30:32
    tingnan naman natin yung steel. So sa
  • 00:30:34
    steel ganun din no? We have the
  • 00:30:37
    proportionality limit which is yung
  • 00:30:39
    stress natin proportional doon sa
  • 00:30:41
    strain. Next is yung elastic limit kung
  • 00:30:45
    saan beyond this magiging permanent na
  • 00:30:48
    yung deformations. And by the way yyung
  • 00:30:50
    elastic modulus ng steel given to sa
  • 00:30:53
    atin we consider it to be 200,000
  • 00:30:57
    megapascals. So this is a actually a
  • 00:30:59
    requirement for the steel meals to
  • 00:31:02
    produce steel na pag ginawa iyung steel
  • 00:31:04
    kailangan ito iyung module doun sa
  • 00:31:05
    elasticity niya 200,000 megapcals.
  • 00:31:09
    Now after that we have what we call the
  • 00:31:12
    yield point. Si yield point this is the
  • 00:31:15
    point at which kahit mag-apply ka
  • 00:31:17
    dagdagan or kahit hindi ka mag-apply ng
  • 00:31:20
    maraming stress. So magpa-flat line siya
  • 00:31:23
    no'. Hindi ka nag-apply ng maraming
  • 00:31:25
    stress pero yung strain ko nadadagdagan.
  • 00:31:29
    Point in which constant stress is
  • 00:31:31
    applied but strain is continuously
  • 00:31:33
    increasing. This is what we call the
  • 00:31:35
    yield point. And then after that we have
  • 00:31:39
    the ultimate strength and the break
  • 00:31:41
    point. Okay? Ang break point is
  • 00:31:44
    mapipingal siya. The failure occurs.
  • 00:31:48
    So ito ultimate 10 strength. Now, one
  • 00:31:51
    difference between this stress strain
  • 00:31:53
    relationship between concrete and steel
  • 00:31:55
    is that uh yung sa concrete that is in
  • 00:31:59
    terms of compression no compressive
  • 00:32:01
    load. Itong sa steel kapag tinesting to
  • 00:32:04
    this is in terms of ah tension. Okay?
  • 00:32:08
    Binabatak yung steel hanggang maputol.
  • 00:32:14
    So ito yung mga points of importance
  • 00:32:17
    kapag magte-testing tayo ng steel. These
  • 00:32:20
    are the
  • 00:32:22
    universal testing machine na ginagamit.
  • 00:32:24
    And as you can see here, ito yung
  • 00:32:26
    nangyayari no kapag hinihila niya yung
  • 00:32:30
    bakal, nandito yung sample. Hinihila
  • 00:32:32
    niya and then as you can see ah liliit
  • 00:32:35
    yung diameter hanggang maputol. Okay?
  • 00:32:39
    Mapuputol siya. 'Yan 'yung tinatawag na
  • 00:32:41
    necking. So ito 'yun necking
  • 00:32:44
    beyond point C beyond the ultimate
  • 00:32:47
    ultimate point magkakaroon na ng necking
  • 00:32:49
    hanggang maputol yung bakal.
  • 00:32:56
    Now let us discuss some structural
  • 00:32:59
    elements. Structural elements on
  • 00:33:01
    buildings where we usually use reinforce
  • 00:33:06
    concrete.
  • 00:33:09
    A structure refers to a system of
  • 00:33:11
    connected parts to support a load.
  • 00:33:14
    Important examples would be buildings,
  • 00:33:16
    bridges, and towers. So 'yun yung mga
  • 00:33:19
    basic categories ng infrastructure na
  • 00:33:21
    ginagamit natin bilang mga civil
  • 00:33:24
    engineer or mga kino-construct natin. Ah
  • 00:33:27
    when designing a structure it should be
  • 00:33:30
    safe. Merong aesthetics. Ah it's it's
  • 00:33:34
    the main concern of the architecture
  • 00:33:37
    profession. And then we have service
  • 00:33:39
    ability. yung service ability sa atin uh
  • 00:33:44
    it has something to do with the feelings
  • 00:33:47
    of the people using the infrastructure.
  • 00:33:51
    It could be that the building is safe
  • 00:33:54
    pero medyo maalog no ma-vibrate. I know
  • 00:33:56
    you have experienced that sa mga I think
  • 00:34:00
    yung sa mga malls minsan ganun no? Pag
  • 00:34:02
    maraming tao minsan mararamdaman mo
  • 00:34:05
    naglalakad 'yung mga tao and
  • 00:34:07
    nagv-vibrate 'yung sahig. That's an
  • 00:34:09
    issue yung mga ganong vibration that's
  • 00:34:11
    an issue of serviceability.
  • 00:34:13
    Okay. Now,
  • 00:34:16
    issues of service will be yung cracking,
  • 00:34:18
    no? Uh, why is it an issue? Kasi if if
  • 00:34:23
    your reinforced concrete has many
  • 00:34:25
    cracks, moisture could penetrate and
  • 00:34:28
    erode the steel bars. And iyung agag
  • 00:34:32
    nagco-coro-road kasi iyung steel bars,
  • 00:34:34
    ang nangyayari doon na dadagdagan iyung
  • 00:34:38
    volume nung steel bars kasi nagkakaroon
  • 00:34:41
    ng ano eh nagba-bind iyung oxygen sa
  • 00:34:43
    kanya so madadagdagan yung volume niya
  • 00:34:46
    and it would lead to more cracking kasi
  • 00:34:49
    lumalaki yun eh. Lumalaki yung bakal sa
  • 00:34:51
    loob pag kinakalawang. Okay? Ba't
  • 00:34:54
    lumalaki? Nadadagdagan ng kalawang. At
  • 00:34:57
    pag nadagdagan siya ng kalawang,
  • 00:34:58
    ipu-push niya yung concrete lalong
  • 00:35:00
    magka-crack. So it's it's a it's an
  • 00:35:05
    issue for us. But one of the main or
  • 00:35:09
    yung pinaka-main talaga natin dito itong
  • 00:35:12
    safety.
  • 00:35:16
    Okay? Ito yung safety. Bale ng hindi
  • 00:35:18
    aesthetics no? Bale ng walang finishes,
  • 00:35:20
    walang pintura. As long as our structure
  • 00:35:24
    is safe against what? Against iyung
  • 00:35:28
    iyung environmental
  • 00:35:31
    constraints natin is yung mga load no?
  • 00:35:33
    Yung load usually earthquake 'di ba?
  • 00:35:36
    Wind
  • 00:35:38
    yung dead load at saka live load.
  • 00:35:42
    So often this requires several studies
  • 00:35:45
    of different solutions before final
  • 00:35:47
    judgement can be made uh as to which
  • 00:35:51
    structural form is most appropriate.
  • 00:35:54
    Uh the design process is both creative
  • 00:35:57
    and technical and requires fundamental
  • 00:35:59
    knowledge of material properties which
  • 00:36:01
    is pag-aaral. Ito yung pinag-uusapan
  • 00:36:03
    natin. And the laws of mechanics which
  • 00:36:06
    govern material response.
  • 00:36:09
    Ah
  • 00:36:11
    yung pagde-design is you have to do a
  • 00:36:14
    preliminary design muna and then you
  • 00:36:17
    analyze it after that preliminary design
  • 00:36:21
    before you come up with the final
  • 00:36:23
    design. So ayan.
  • 00:36:29
    Now, one of the most basic structural
  • 00:36:32
    elements are the beams and gearders. So,
  • 00:36:34
    beams are usually straight uh horizontal
  • 00:36:37
    members to carry the vertical loads. Uh
  • 00:36:41
    quite often they are classified
  • 00:36:43
    according to the way they are supported
  • 00:36:46
    as indicated in this figure. Could be
  • 00:36:49
    cantiliver. We have the overhanging
  • 00:36:52
    beams. Ito yung overhanging beams. Ah we
  • 00:36:56
    have the discontinuous
  • 00:36:59
    beam. Ito yun. Wala siyang continuity.
  • 00:37:03
    Ah sorry that is continuous pala. Okay
  • 00:37:07
    continuous beam. Sabihin direiretso
  • 00:37:09
    siya. Simply supported. Canty labor
  • 00:37:13
    simply supported. Or we also call this
  • 00:37:15
    the prop beam.
  • 00:37:21
    Okay. And then we have the fixed ended
  • 00:37:23
    beams. Now beams are primarily designed
  • 00:37:26
    to resist bending moment. However, if
  • 00:37:29
    they are short, kapag short and carry
  • 00:37:32
    large loads, meron tayong sheer na
  • 00:37:36
    maggo-govern doon sa design. Magiging
  • 00:37:39
    sheer governed design pag maikli. Pero
  • 00:37:42
    usually beams kasi mahahaba yun. So
  • 00:37:46
    bending moment.
  • 00:37:50
    Now to continue uh for bending and
  • 00:37:53
    deflections if the structure deformation
  • 00:37:56
    disappear and the structure gains its
  • 00:37:58
    original shape when the actions are or
  • 00:38:02
    the actions causing this deformations
  • 00:38:04
    are removed the deformation are termed
  • 00:38:07
    as elastic deformation. Kapag naman
  • 00:38:10
    permanent yung deformation, that is
  • 00:38:11
    kahit tanggalin mo yung load hindi siya
  • 00:38:13
    bumabalik sa dati niyang appearance no
  • 00:38:16
    sa original niyang shape. Then that is
  • 00:38:19
    in elastic or plastic deformation.
  • 00:38:22
    Now pagdating sa beams, usually we have
  • 00:38:25
    positive moment makes the beam smile
  • 00:38:30
    and then negative moment makes the beam
  • 00:38:32
    frown. So ganito 'yung usual na
  • 00:38:37
    sign convention natin.
  • 00:38:42
    So here are examples of reinforce
  • 00:38:44
    concrete beams and gearders. So as you
  • 00:38:46
    can see uh these are the
  • 00:38:50
    gearders.
  • 00:38:52
    Okay? I think this are tie beams
  • 00:38:55
    kung kung nasa baba sila nung structure.
  • 00:38:57
    So I'm not sure. Ah okay. Nasa ano sila,
  • 00:39:00
    elevated sila. Ito na yung pangalawang
  • 00:39:03
    floor. Okay. Now, this are the
  • 00:39:06
    reinforcement cage. We have the
  • 00:39:08
    longitudinal bars. And then we have the
  • 00:39:13
    sterups na tinatawag doon sa beam. yung
  • 00:39:15
    paikot yun yung sterups. We also have
  • 00:39:18
    the term what we call effective depth.
  • 00:39:20
    That is from the extreme
  • 00:39:24
    compression hanggang doon sa centroid
  • 00:39:27
    nung steel bars. Hindi siya hanggang
  • 00:39:28
    doon sa baba no? Hanggang dito lang sa
  • 00:39:31
    mga steel bars. That is the effective
  • 00:39:33
    dep.
  • 00:39:34
    Okay.
  • 00:39:38
    So typically ito yung mga beam designs.
  • 00:39:41
    Ah meron kang longitudinal bars and then
  • 00:39:45
    merong mga cuts no ah L/ 20, L/5
  • 00:39:52
    mga ganyan, L/3
  • 00:39:54
    depending on the on the detailing na
  • 00:39:57
    ginagamit. I've seen L / 4 and L /3 most
  • 00:40:02
    of the time. Okay? Diyan siya
  • 00:40:04
    nagka-cutof at saka nagi-splice. Ganyan
  • 00:40:07
    ini-specify. So ito yung bakal.
  • 00:40:10
    So kung i-splice mo siya
  • 00:40:13
    dito yung mga splice points, no? Meron
  • 00:40:15
    meron ding computation kung gaano kahaba
  • 00:40:18
    dapat yan.
  • 00:40:19
    Okay. So this are typical details. And
  • 00:40:22
    then of course yung steerups natin hindi
  • 00:40:25
    na pinapakita pero yung sterups yun yung
  • 00:40:29
    yung mga paganito na.
  • 00:40:32
    Okay.
  • 00:40:36
    So we have flexure cracks. Usually this
  • 00:40:39
    is for the slabs and beams.
  • 00:40:42
    Okay. Flexure cracks originate from the
  • 00:40:46
    maximum moment region. And nangyayari to
  • 00:40:50
    when we have in adecate flexal capacity.
  • 00:40:54
    Kulang yung ano yung moment capacity. So
  • 00:40:56
    nagkakaroon ng cracking na vertical.
  • 00:40:59
    Okay, vertical cracking. So sao 'yan sa
  • 00:41:03
    taas banda
  • 00:41:06
    sa mid span dito sa gitna.
  • 00:41:09
    We also have sheer cracks. Originates
  • 00:41:12
    near supports because you have inadecate
  • 00:41:15
    sheer capacity. Ibig sabihin kulang yung
  • 00:41:17
    ano either kulang yung size nung
  • 00:41:19
    concrete or kulang yung steerups dito sa
  • 00:41:23
    mga portion na 'to. So ayan yung mga
  • 00:41:25
    diagonal cracking dito sa support. Yan
  • 00:41:30
    ganyan.
  • 00:41:34
    Now para naman sa mga columns, columns
  • 00:41:36
    are also structural elements na
  • 00:41:40
    ginagamit yung reinforced concrete. So
  • 00:41:42
    this are members that are vertical.
  • 00:41:46
    resist compressive loads. We call that
  • 00:41:49
    columns. So makikita mo dito meron akong
  • 00:41:51
    column. Ayan column. And they are
  • 00:41:54
    carrying multiple levels. Ito yung
  • 00:41:57
    ground floor slab. We have yung slab
  • 00:41:59
    one, slab two. We have kung minsan yung
  • 00:42:02
    may roof deck ' ba lahat yan ah
  • 00:42:06
    naka-connect yan sa mga beams. And yung
  • 00:42:08
    mga beams na yon naka-connect doun sa
  • 00:42:10
    column. to
  • 00:42:13
    to transfer all those loads papunta doon
  • 00:42:16
    sa foundation. So the columns are the
  • 00:42:19
    vertical elements resisting yung mga
  • 00:42:21
    downward forces.
  • 00:42:25
    So ties naman no kung sa beams meron
  • 00:42:28
    tayong steerups, sa columns meron tayong
  • 00:42:30
    ties. This are confinement to prevent
  • 00:42:33
    buckling. Buckling ng ano nung nung mga
  • 00:42:37
    actually this is not buckling nung nung
  • 00:42:40
    column but rather backling nung mga
  • 00:42:42
    bakal sa loob nung column. Kasi one of
  • 00:42:45
    the failure niyan ' ba kungwari ito yung
  • 00:42:47
    column natin.
  • 00:42:50
    Ah teka
  • 00:42:52
    let's say ito yung column.
  • 00:42:57
    So may mga bakal yan sa loob. One of the
  • 00:42:59
    failure kasi is kung kung yung ties mo
  • 00:43:02
    is masyadong malayo sa isa't isa, what
  • 00:43:06
    happens is that pwede ong magbackle
  • 00:43:09
    pagon palabas yung bakal no? Nagkakaroon
  • 00:43:13
    siya ng backlink palabas lalo na kapag
  • 00:43:17
    yung load natin is very very large, very
  • 00:43:20
    heavy. So mag-backle siya palabas ganyan
  • 00:43:24
    kapag inadicate itong ties. Ito yung
  • 00:43:27
    ties.
  • 00:43:29
    Yan t.
  • 00:43:37
    So ito yung backling effect. Ito naman
  • 00:43:39
    itong backling effect na to. This is due
  • 00:43:43
    to moment and instability. Ito yung
  • 00:43:45
    buong column yung pwedeng mag-backle
  • 00:43:47
    lalo na kapag mahaba masyado yung yung
  • 00:43:50
    length nung column. So again yung ties
  • 00:43:53
    usually used for confinement to prevent
  • 00:43:55
    backling nung longitudinal bars but
  • 00:44:00
    still yung colum mo as a hole could
  • 00:44:03
    buckle. So that that's one of the
  • 00:44:05
    failure na pwedeng mangyari sa columns.
  • 00:44:08
    So again, I'm just discussing some basic
  • 00:44:11
    ano 'no uh basic features no' features
  • 00:44:16
    ba o bugs? Features ng mga structural
  • 00:44:20
    elements natin na ginagamitan ng
  • 00:44:22
    reinforce concrete.
  • 00:44:25
    So of course meron tayong slab. slab or
  • 00:44:27
    the flat horizontal panels that support
  • 00:44:30
    the floor. Uh it is usually supported in
  • 00:44:33
    beams and gearers or directly by
  • 00:44:36
    columns. Pwedeng walang beam and gurner
  • 00:44:38
    no pwedeng columns. They carry iyung
  • 00:44:41
    gravity loads and transfer them to the
  • 00:44:44
    vertical components, columns or walls
  • 00:44:47
    and also act as horizontal diaphrams.
  • 00:44:50
    Ibig sabihin kapag may mga lateral loads
  • 00:44:53
    lalo na iyung mga earthquake load. Si
  • 00:44:55
    slab din 'yung nagta-transfer nung mga
  • 00:44:57
    inertial forces papunta doon sa ating uh
  • 00:45:02
    elements na nagre-resist nung nung
  • 00:45:05
    earthquake by transferring lateral load
  • 00:45:08
    to vertical components. Okay? We have
  • 00:45:11
    several types of slabs pero meron tayong
  • 00:45:14
    one way and two way floor systems and
  • 00:45:17
    and there are other types of slabs pero
  • 00:45:19
    most common itong dalawa sa reinforce
  • 00:45:22
    concrete design.
  • 00:45:25
    For the oneway floor system, this are
  • 00:45:27
    slab that is supported only on two
  • 00:45:32
    slides. No, you you could assum assume
  • 00:45:35
    na supported lang siya doon sa longer
  • 00:45:38
    side. Ito ay kapag yyung shorter span
  • 00:45:41
    over the longer span is less than5, the
  • 00:45:45
    one way slab bends in only one
  • 00:45:47
    direction. Nagbe-bend siya along the
  • 00:45:49
    shorter span at 'yung support niya
  • 00:45:51
    nandito sa longer span. Ito yung L.
  • 00:45:55
    Tapos yung bending niya no, nagbe-bend
  • 00:45:58
    siya doon sa shorter span. And because
  • 00:46:01
    of that, ah yung flexural design would
  • 00:46:05
    be yung paganito no along the short
  • 00:46:08
    direction yung flexoral design. 'Yung sa
  • 00:46:10
    longer direction, ung sa L direction,
  • 00:46:12
    hindi siya flexure design but rather, as
  • 00:46:15
    you can see here,
  • 00:46:18
    we have distribution rebar. Ito yung
  • 00:46:22
    pahaba. It's not flexure but
  • 00:46:26
    distribution rebar para lang
  • 00:46:27
    ma-distribute iyung load. and
  • 00:46:31
    also
  • 00:46:33
    do sa temperature control and cracking.
  • 00:46:37
    Okay? So ito lang sa short direction.
  • 00:46:39
    Ito lang yung dine-design natin for the
  • 00:46:41
    moments kapag one way floor system.
  • 00:46:44
    Again, one way floor system nagbe-bend
  • 00:46:46
    sa short direction, short direction ng
  • 00:46:48
    bending. Ganito. Supported siya. Assumed
  • 00:46:51
    to be supported only in the long
  • 00:46:53
    direction. Hindi na nagma-matter kung
  • 00:46:55
    may beam talaga dito or doon sa kabila.
  • 00:46:58
    Okay. As long as ito yung yung ratio
  • 00:47:02
    nung shorter span and longer span, ang
  • 00:47:04
    assumption natin one way. Again,
  • 00:47:07
    this is an idealistic assumption, no?
  • 00:47:11
    Ah, lalo na kung may began naman dito,
  • 00:47:14
    of course, yung beam na yon would would
  • 00:47:16
    support some part some portion of the of
  • 00:47:18
    the slab, but we ignore it and we just
  • 00:47:21
    assume na dito siya sa mas mahabang
  • 00:47:24
    site.
  • 00:47:27
    For the two way floor system naman,
  • 00:47:29
    kapag iyung S / Ler than 5, the load is
  • 00:47:33
    assumed to be delivered to the
  • 00:47:35
    supporting beams and gearders in two
  • 00:47:37
    directions. Kaya two way. Two directions
  • 00:47:39
    ibig sabihin yyung along S at saka yyung
  • 00:47:42
    along the length na mga beams. Okay?
  • 00:47:45
    This is referred to as a twoway slab
  • 00:47:47
    system. So ito yung example yung bending
  • 00:47:51
    niya is in both directions lalo na kapag
  • 00:47:55
    supported ng apat na beam.
  • 00:47:58
    So that ends the presentation
  • 00:48:03
    if you have any question please
  • 00:48:06
    comment or tell me you could comment
  • 00:48:11
    below
  • 00:48:13
    thank No.
标签
  • Reinforced Concrete
  • Concrete Design
  • Steel Reinforcement
  • Curing Process
  • Structural Elements
  • Beams
  • Columns
  • Slabs
  • Stress-Strain Relationship
  • Serviceability