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Civil Engineering Questions and Answersen-USActiveForums 4.2Copyright 2000-2013 ENGINEERING.comMon, 22 Sep 2014 20:26:08 GMTSeptic Tank overflow in hardpan calcreteWe are currently building a shopping centre in hardpan calcrete and the issue came up that the overflow from the septic tank would not word as it will be constructed in hardpan calcrete. What other cost effective options do we have. Note that the septic tank has already been constructed and the current issue is the honeysucking cost.
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Danie le RouxMon, 22 Sep 2014 20:26:08 GMThttp://www.engineering.com/AskForum/aff/30/aft/1661/afv/topic.aspx0Wood bridgeI need to construct a temporary wooden bridge over a shallow (1') stream. I will be approx 10' long, and needs to support 8,000 lbs. ( a loader and a tree) would 6 x 6 lumber work for that span and load? Any help would be appreciated <br /> <br />
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Devin MulhareThu, 18 Sep 2014 17:30:05 GMThttp://www.engineering.com/AskForum/aff/30/aft/1657/afv/topic.aspx0Shallow Foundation doubtQuestion: <br /> A strip footing is located at a depth of 0.75 m in a sand of unit weight 18 kN/m3 <br /> ; the water table being well below the foundation level. The characteristic shear strength parameters are c’ = 0 and φ’ = 38o. The footing supports a design load of 500 kN/m. Determine the required width of the foundation for the ultimate limit state to be satisfied to EC7 DA1b. <br /> <br /> Answer: <br /> As attached as an image. <br /> The final answer is 310.5B + 243B. But, as you see, ((310.5 + 243B)B)/1.0, why is it not 243B^2? Is the width negligible? Or? <br /> <br /> I do not quite understand why is it not 243B^2 instead of the given answer by my school teacher that is 310.5B + 243B. <br /> <br /> Thank you in advance. <br /> <br />
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Apple XNThu, 18 Sep 2014 06:48:20 GMThttp://www.engineering.com/AskForum/aff/30/aft/1656/afv/topic.aspx0Harmonic Vibration of Undamped systemFor the frequency ratio ω/ωn = 1, the graph goes to infinity. Why is this? What practical consequences come from this?
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Tamika ProctorWed, 17 Sep 2014 15:54:36 GMThttp://www.engineering.com/AskForum/aff/30/aft/1654/afv/topic.aspx0specified concrete compressive strengthhow to select a specified concrete compressive strength( f'c) for a designing bulding and ...?
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shahram shahramMon, 15 Sep 2014 01:24:17 GMThttp://www.engineering.com/AskForum/aff/30/aft/1650/afv/topic.aspx0Southern yellow pine floor beamHi, new here. First forum I found, so forgive if not exactly the right place to ask. <br /> <br /> I live on an out island in the Bahamas, which means steel beams, lvl, glulam etc is unavailable or very expensive and months away, so looking for an old-school solution... <br /> <br /> Building a 24x24ft wooden house, as a complete amateur. It's 2 storey (with a small tower on one corner and a roof deck). I want the lower floor to be completely open inside and have been advised a built up beam is the way to go. So, I can get 24ft long 2x12 (actually 1.5x11.25" or 3.8x28.5cm) pressure treated southern yellow pine. <br /> <br /> We're considering a 3-ply built up beam, glued with 1/2" plywood between the lumber, and bolted together. <br /> <br /> Can I use this as a floor beam, and run 8ft and 16ft 2x12" floor joists off of it, 16"oc? Would that span 24ft OK, with a storey above it (2 beds/1bath, but non-loadbearing internal walls)? <br /> <br /> TIA for any advice. <br /> <br /> Mark
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Mark HaySat, 13 Sep 2014 05:48:05 GMThttp://www.engineering.com/AskForum/aff/30/aft/1648/afv/topic.aspx0Need Interview for my class. Please answer short questions.Please answer these questions for me. <br /> <br /> What is your name and field that you are in? <br /> <br /> Email address for further questioning? (Not required) <br /> <br /> 1. How do you feel about the workload in engineering? <br /> 2. What is most challenging engineering project that you have been a part of? Explain. <br /> 3. What do you enjoy most and least about engineering? <br /> 4. What are some of the things that you have spent the most time on in the past week? <br /> 5. What features do you think are necessary to be an effective engineer? <br /> <br /> <br />
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Ryan CusackTue, 09 Sep 2014 07:30:06 GMThttp://www.engineering.com/AskForum/aff/30/aft/1640/afv/topic.aspx0Steps in doing a structural investigationWhat are the steps in doing a structural investigation?
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Kevin SaluagueFri, 27 Jun 2014 14:09:50 GMThttp://www.engineering.com/AskForum/aff/30/aft/1521/afv/topic.aspx1Concrete Slab Floor Finish FlatnessBuilding a 32 mgal concrete tank. It will be filled with radioactive grout. The engineer of record requires us to test the slab for "flatness". The engineer states this test is only to determine the adequacy of the concrete cover since the floor will be covered with grout. I can't find any literature describing that this test gives any indication of concrete cover over rebar. No rebar is exposed.
http://www.engineering.com/AskForum/aff/30/aft/1581/afv/topic.aspx
scott youellWed, 23 Jul 2014 06:26:15 GMThttp://www.engineering.com/AskForum/aff/30/aft/1581/afv/topic.aspx1Complex beam problem# In simple beam the cross sectional area is constant. So Mom of inertia and neutral axis is also constant. <br /> ----- <br /> <br /> # This is not a simple beam, <br /> <br /> - Here the cross sectional area varies. <br /> <br /> - So moment of inertia must vary. <br /> <br /> - As the CG of two beams also vary then there should be change in neutral axis too. <br /> <br /> -So Mom of inertia wrt a axis also varies, must not go through CG!! <br /> <br /> --------- <br /> # My que is HOW IS THAT? <br /> <br /> Is that will be like the green line? <br /> <br /> -------- <br /> # How to calculate that? To find axial and shear stresses... Please help!!! <br /> <br /> -------- <br /> # I dont like to draw any touch of Area moment or double integration methods to find stresses! <br /> <br /> ------------ <br /> <br /> I have seen it in some perspective and it feels like below the Red line of fat section of beam the whole area is compressed. So neutral axis remains Red line. The whole thing is caused by the Shear force occurred between two layers of beam. <br /> <br /> But if the fat section is considered too long then it feels like Neutral axis will go through its CG of fat section. <br /> <br />
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Adnan ShahriarWed, 20 Aug 2014 23:25:17 GMThttp://www.engineering.com/AskForum/aff/30/aft/1616/afv/topic.aspx0Solar Glasses: How to Translate Material Hardness to Not Breaking when hit with HailHello, <br /> <br /> I am choosing glasses for a novel solar cell design, and part of the criteria is if the glass will be able to withstand hail and other things (?) falling from the sky, since this glass will be the cover glass for the entire solar cell. I can gather information on the glass including Knoop/Moh's hardness, Young's modulus, etc., but 1. I'm not sure which of these structural properties translates to being able to withstand things like hail and 2. If it's hardness, how hard is hard enough/how can I determine this? <br /> <br /> Any help is greatly appreciated. Thanks. <br />
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Nick FoleyMon, 28 Jul 2014 06:50:37 GMThttp://www.engineering.com/AskForum/aff/30/aft/1585/afv/topic.aspx0Uplift on brick wall: connector choicesI have to look over engineering analyses of uplift of beams attached to the top of a brick wall. The wall is 12" wide multiwythe unreinforced solid brick, the uplift force is typically between about 300 and 1000#. I'm not an engineer but my physics background helps me follow the reasoning and calculations involved. <br /> <br /> I have looked at many dozens of these, stamped by many different PE's. Far and away the most common method of attachment is a bolt or threaded rod embedded in the top of the wall 6-10" with Hilti HY70 ro equivalent epoxy. In looking into this further, I've realized that the HY70 ratings are for mounting into the side of the wall, not the top, and require a 16" distance from edges, obviously not possible in the top of a 12" wall. Some other approaches include essentially the same but with anchoring cement in the hole, or threaded or mechanical expansion devices (typically with fairly shallow embedment, 2-4"). <br /> <br /> I've talked with engineers at Hilti, and they basically said they have no tests or reliable way of determining the best way to do this. I've done a fair bit of web research. I've talked with several experienced structural engineers. I have found no solid information, nor really anything that could justifiably be called "best practices". <br /> <br /> The reason this came to a head was that one PE, undertaking an analysis of his own, concluded that the embedment of the 3/8" threaded rod required for the uplift had to be embedded 50". If you understand how these are installed, you'll know that's impossible, or at least practically so. And yet, he's actually the only engineer that didn't improperly apply the load tables. <br /> <br /> Now there are real problems with the issue to begin with: unreinforced brick walls are inherently suboptimal for uplift. And yet, the problem needs to be solved. So I'm looking for something that I can have some faith in, research towards that end, or any help towards a "best practices" solution. Thanks for any help. <br /> <br />
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Keith WinstonSat, 26 Jul 2014 12:52:11 GMThttp://www.engineering.com/AskForum/aff/30/aft/1584/afv/topic.aspx0Can I remove this wall without adding a header?Hi, <br /> <br /> First post here, structural is not really my forte (I'm more of an HVAC guy), so I'm looking for some professional opinions here. I would like to take down the wall separating my living room and dining room. I took a bunch of measurements of the first floor and the structural members in the basement below. I attached an overlay of the first floor walls (the one in green is the one I want gone) and the structural members in the basement below in red dashed lines. I'm 90% sure this wall is not load bearing for a few reasons: <br /> <br /> 1.) The floor joists run parallel to the wall I want to remove. <br /> 2.) There is no walls directly above this wall on the second floor. This isn't shown on my plan but I did also make a plan of the second floor and overlaid it on the first floor to double check. <br /> 3.) The floor joists for the second floor run in the same direction. Again, this isn't shown here but I verified this visually. <br /> <br /> What was throwing me for a loop were the doubled up members beneath the wall in question but I read in a book that this was good practice back in the day to support the weight of the wall above. So I suspect the wall can come out without the need to install a header in it's place but I would like to be 100% sure. House is circa 1875, balloon framed, plaster & lathe with field stone foundation if it matters. <br /> <br /> What does everyone think? All help is appreciated.
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Michael LeachFri, 18 Jul 2014 10:34:04 GMThttp://www.engineering.com/AskForum/aff/30/aft/1572/afv/topic.aspx4Civil EngineeringI am developing an android application (system) which measures the building vibration and calculates its natural frequency. I was planning to map these natural frequencies and during a disaster, this application can be used for risk assessment. But since only magnitude of an earthquake is known it seems impossible to compare the earthquake frequency and building natural frequency. I referred many articles, but I was unable to find what can be done if only the natural frequency of the building is known. If anybody have some idea about this matter, please share me. <br /> I will be grateful for any help you all can provide.
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43544Tue, 15 Jul 2014 04:04:20 GMThttp://www.engineering.com/AskForum/aff/30/aft/1567/afv/topic.aspx0principal stressesformula of principal stresses: <br /> <br /> (Sx+Sy)/2 +- sqrt( [(Sx+Sy)/2]^2 + T^2 ) <br /> <br /> I got Sx, Sy, and T in a complex format: a+bi <br /> <br /> I would like to know what is the correct way to compute the principal stresses: <br /> <br /> <br /> --- perform the calculations in a complex format and in the end compute the magnitude, or <br /> <br /> --- compute magnitude of Sx, Sy and T and replace in the formula of the principal stresses. <br /> <br /> Thank you
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Alan Shear ShearTue, 24 Jun 2014 04:47:15 GMThttp://www.engineering.com/AskForum/aff/30/aft/1365/afv/topic.aspx0architectural design of buildingsplease visit the site "mybuildingdesign.com" and help me to know how can our team help architecture students and professionals.
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mariam yousafMon, 22 Jul 2013 11:49:49 GMThttp://www.engineering.com/AskForum/aff/30/aft/1071/afv/topic.aspx1Changing floor joist directionI am currently in the middle of drawing plans for my home to rebuild and add an additional level due to termite damage. The home is currently a split level with vaulted ceilings throughout with cinder block foundation, and crawl space. I am trying to design floor joists that run the width of the room with no posts/beams, but have been told I need to make one of the walls a load bearing wall to do so. Dotted lines in the picture represent foundation under the floor, as well as the two piers under the floors. My issue is with determining loads for the roofs (peak over the center of each side of home) and if this is something that is feasible. What I'm trying to avoid is: <br /> <br /> 1.Structural post shown in entertainment room <br /> 2.Boxing out for HVAC/plumbing if joists run parallel to roof rafters <br /> <br /> While creating an open floor plan <br /> <br /> Span charts ive seen are showing 2x12s 12 OC. Any tips or suggestions on making the center wall load bearing?
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Joe MaioFri, 13 Jun 2014 15:36:57 GMThttp://www.engineering.com/AskForum/aff/30/aft/1322/afv/topic.aspx0International Conference on: Conservation of Architectural HeritageWe have the honor to invite you to attend our international conference on: "Conservation of Architectural Heritage". at the magical towns Luxor and Aswan. <br /> This conference is planned to be held on board a Nile cruise between Luxor and Aswan, Egypt. Overlooking the Nile River. <br /> The Conservation of Architecture Heritage conference helps university researchers, professionals and policy makers to get together to discuss the most pressing issues concerning the conservation of archaeological, architectural and urban landscapes. <br /> For registering and more details about the conference: <br /> http://www.ierek.com/Conferences/Conference-Details/345#.U3ivUvmSxt0 <br /> Follow us at: <br /> https://twitter.com/IEREKcom <br /> http://www.linkedin.com/groups/IEREK-7430826?gid=7430826&mostPopular=&trk=tyah&trkInfo=tarId%3A1398779878248%2Ctas%3Aierek%2Cidx%3A1-1-1 <br /> Contact us at: <br /> diana@ierek.com <br /> omnia@ierek.com <br /> Call us at: <br /> (+2) 01027233310 <br /> (+2) 01000028021 <br />
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ierek ierekSat, 31 May 2014 22:10:22 GMThttp://www.engineering.com/AskForum/aff/30/aft/1307/afv/topic.aspx0What size beam to clear span 24'?What size beam do I need to span 24' across a garage? This beam will support 2x6 by 16' roof rafters, 16" on center. The roof will be metal and 3/4" plywood. Home located in Florida, no snow load issues. This house is block wall construction and the existing beam is a 3' tall box truss with plywood on both sides. I want to replace it with something shorter height wise. The garage is set about 3' lower than the house and the rafters are an extension of the roof beyond the house truss system. This beam will be perpendicular to and btwn the house truss and garage roof. I would like to use double 2x12 by 24' pine with plywood sandwiched btwn, but am concerned about sag. Do I need to use a microlam beam? If so what size? <br /> <br /> Thank you <br /> SP
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Steve PowersTue, 25 Feb 2014 09:57:48 GMThttp://www.engineering.com/AskForum/aff/30/aft/1239/afv/topic.aspx0Single Girder Electric Overhead Crane!I am currently producing a technical report (topic of my choice) of the structural design of an overhead crane, it is mandatory to complete this to graduate from my program. <br /> <br /> The design guides I am using are the CISC Handbook of Steel Construction 10th edition, CISC Design guide for overhead crane supporting steel structures, Whiting Crane Handbook, and CMAA Spec. No.74. <br /> <br /> I am having difficulty understanding Clause 26.0 of CISC HSC. This is Fatigue Design Criteria. I am confused about variable n and N. The number of cycles I wish to design for is 2,000,000. This will give my structure approximately 50 years of operation. I am using detail category A, Table 9 of S16-09 HSC. <br /> <br /> If anyone could explain to me the process of going through fatigue design I would greatly appreciate it. The mathematics involved in this is not my problem, just the literature of the codes and what variables correspond with the values I have for my crane.
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Josh MitchellSun, 16 Feb 2014 07:24:00 GMThttp://www.engineering.com/AskForum/aff/30/aft/1233/afv/topic.aspx0