question: Why are culverts and drainage pipes “ribbed”? Wouldn’t a smooth pipe be better for letting stuff flow through?
comment: As the other answer, it is bendable in the lengthwise direction. But also, and possibly more importantly, it is far less able to collapse. The ribbing gives it strength in the circumferential direction. It's similar to corrugated iron sheets which bend in one direction, but not across the corrugations.
passages: Windrows are the piling of erosion-resistant material on a river's bank, where if buried, they become known as trenches. When erosion persists an already determined location, these windrows and trenches are made to slide down with the bank in order to protect it from further occurrences of erosion. This allows for the need of minimal design work, in that installation is simple on high banks, although other methods could lead to failure. Disadvantages include the windows and trenches continuing to erode until they intersect the erosion-resistant material. Results of this method have been seen to be inconsistent, as the steep slope of the bank leads to increased velocity of the river.
   The technique had first been used at Moderna on the Rochdale Canal, although in this case the panels were made in Italy, as no British mills could produce such radiused panels.
   BULLET::::- The filling in, or flanking, consists of laying the spaces between the screeds with coarse stuff, which is brought flush with the level of the screeds with the floating rule.
   BULLET::::- A "ribbed slab" gives considerably more strength in one direction. This is achieved with concrete beams bearing load between piers or columns, and thinner, integral ribs in the perpendicular direction. An analogy in carpentry would be a subfloor of bearers and joists. Ribbed slabs have higher load ratings than corrugated or flat slabs, but are inferior to waffle slabs.
   To have a well-developed flow pattern, pump manufacturer's manuals recommend about (10 diameters?) of straight pipe run upstream of the pump inlet flange. Unfortunately, piping designers and plant personnel must contend with space and equipment layout constraints and usually cannot comply with this recommendation. Instead, it is common to use an elbow close-coupled to the pump suction which creates a poorly developed flow pattern at the pump suction.
   Cold formed members can be efficient on a weight basis relative to mill rolled sections for secondary member applications. Additionally, Z sections can be nested for transportation bundling and, on the building, lapped at the supports to develop a structurally efficient continuous beam across multiple supports.
  
  Section::::Etymology.
  
  Information on the origin of the term "purlin" is scant. The Oxford Dictionary suggests a French origin, with the earliest quote using a variation of "purlin" in 1447.
  
  Section::::Gallery.
  
  Note: The sketches in this section reference terminology commonly used in the UK and Australia. 
  
  Section::::See also.
  
  BULLET::::- Girt
  
  BULLET::::- Joist
   Where a course begins with a quoin stretcher, the course will ordinarily terminate with a quoin stretcher at the other end. The next course up will begin with a quoin header. For the course's second brick, a queen closer is laid, generating the lap of the bond. The third brick along is a stretcher, and is—on account of the lap—centred above the header below. This second course then resumes its paired run of stretcher and header, until the final pair is reached, whereupon a second and final queen closer is inserted as the penultimate brick, mirroring the arrangement at the beginning of the course, and duly closing the bond.
   One of the earliest examples of the introduction of the intermediate rib is found in the nave of Lincoln Cathedral, and there the ridge rib is not carried to the wall rib. It was soon found, however, that the construction of the web was much facilitated by additional ribs, and consequently there was a tendency to increase their number, so that in the nave of Exeter Cathedral three intermediate ribs were provided between the wall rib and the diagonal rib. In order to mask the junction of the various ribs, their intersections were ornamented with richly carved bosses, and this practice increased on the introduction of another short rib, known as the lierne, a term in France given to the ridge rib. Lierne ribs are short ribs crossing between the main ribs, and were employed chiefly as decorative features, as, for instance, in the "Liebfrauenkirche" (1482) of Mühlacker, Germany. One of the best examples of Lierne ribs exists in the vault of the oriel window of Crosby Hall, London. The tendency to increase the number of ribs led to singular results in some cases, as in the choir of Gloucester Cathedral, where the ordinary diagonal ribs become mere ornamental mouldings on the surface of an intersected pointed barrel vault, and again in the cloisters, where the introduction of the fan vault, forming a concave-sided conoid, returned to the principles of the Roman geometrical vault. This is further shown in the construction of these fan vaults, for although in the earliest examples each of the ribs above the tas-de-charge was an independent feature, eventually it was found easier to carve them and the web out of the solid stone, so that the rib and web were purely decorative and had no constructional or independent functions.
   If the upstream shear stress is less than the threshold value, the bed material upstream of the bridge is at rest. This is referred to as the clear-water condition because the approach flow is clear and does not contain sediment. Thus, any bed material that is removed from a local scour hole is not replaced by sediment being transported by the approach flow. The maximum local scour depth is achieved when the size of the scour hole results in a local reduction in shear stress to the critical value such that the flow can no longer remove bed material from the scoured area.
   Most state transportation agencies have used flowable fill mainly as a trench backfill for storm drainage and utility lines on street and highway projects. Flowable fill has also been used to backfill abutments and retaining walls, fill abandoned pipelines and utility vaults, cavities, and settled areas, and help to convert abandoned bridges into culverts. The most frequent use of flowable fill is reported in the states of Minnesota, Maryland, Michigan, Iowa, and Indiana.
   The stone causeway at the Suttor River was an early civil engineering project undertaken by the Queensland Government in North Queensland. The earliest appears to have been the stone bridge and culvert on Damper creek on the Dalrymple Gap Track, which was built in the mid-1860s. From 1880, responsibility for surveying, constructing and maintaining roads passed from the Works Department to local Divisional Boards and the Department of Public Lands (as the latter still built roads on Crown Lands opened for selection) and the Queensland Government did not resume a major role in building main roads until the 1920s.
   The culvert comprises a long tunnel, about wide, beneath an unsealed roadway. It is lined on the floor and to about a third of its height along the sides with rusticated sandstone blocks. The blocks lining the floor are long and considerably narrower than those lining the side. There are two courses of blocks on each side of the culvert. The arched roof of the culvert is lined with bricks.
   Samples should be representative of the installation environment since the liner is installed in the ground. Wet sandbags should be used around the restraint where the test sample will be extracted from. As with any specimen preparation for a materials test, it is important to not affect the material properties during the specimen preparation process. Research has shown that test specimen selection can have a significant effect on the CIPP flexural testing results. A technical presentation at the CERIU INFRA 2012 Infrastructures Municipales Conference in Montreal outlined the results of a research project which examined the affects of test specimen preparation on measured flexural properties. Test specimens for ASTM D790 flexural testing must meet the dimensional tolerances of ASTM D790.
   Hy-Rib products are used in the construction of tunnels, conduits, flumes, culverts, silos, cisterns, chimneys, and water tanks. For these applications the lath sheet products come in curved steel sheets. They are locked together to form a complete tube or tunnel on site. The curved sheets are stood on edge in the case of silos, water tanks, cisterns, and chimneys. The connected form then is plastered with cement. In some cases a few steel rods are added for extra strength and connecting purposes.
   One of the earliest examples of the introduction of the intermediate ridge rib is found in the nave of Lincoln Cathedral; This element, called a ridge rib, was not connected to the walls. Architects in England began adding new ribs, largely for decoration. In the nave of Exeter Cathedral three intermediate ribs were provided between the wall rib and the diagonal rib. In order to mask the junction of the various ribs, their intersections were ornamented with richly carved bosses, and this practice increased on the introduction of another short rib, known as Lierne vaulting. the lierne, a term in France given to the ridge rib. English Lierne vaulting uses short ribs that cross between the main ones; these were employed chiefly as decorative features, for example in stellar vaults, one of the best examples of which is in the vault of the oriel window of Crosby Hall, London. Ribs came more and more numerous and more and more decorative leading to the extraordinarily elaborate and decorative fan vault, first used in the choir of Gloucester Cathedral .
   Transverse rib
  
  A transverse rib () is the term in architecture given to the rib of a rib vault which is carried across the nave, dividing the same into bays. Although as a rule it was sunk in the barrel vault of the "thermae", it is found occasionally below it, as in the Piscina at Baiae and the so-called Baths of Diana (Nymphaeum) at Nîmes. In the Romanesque and Gothic styles it becomes the principal feature of the vault, so much so that Scott termed it the "master rib".
   Hump and hollow
  
  Hump and hollow, occasionally termed "flipping", is a technique of contouring pastures to improve productivity especially on the West Coast of New Zealand.
  
  The technique, used on peat soils and in areas of high rainfall, allows for faster water runoff and lowers the level the water table. 
  
  In a three-year trial at Kowhitirangi on the West Coast of New Zealand where the annual rainfall is 3000mm, an improvement of 14% was made when compared with no drainage. 
   The culvert is a highly intact example of the standard design for brick culverts on the Southern and Western Railway. The culvert follows the design approved by the Engineer in Chief for construction of the line, Abraham Fitzgibbon, in 1863 and comprises floors and sides of sandstone with an arched roof of bricks.
   Ductile iron pipe is somewhat resistant to internal corrosion in potable water and less aggressive forms of sewage. However, even where pipe material loss and consequently pipe wall reduction is slow, the deposition of corrosion products on the internal pipe wall can reduce the effective internal diameter. A variety of linings are available to reduce or eliminate corrosion, including cement mortar, polyurethane and polyethylene. Of these, cement mortar lining is by far the most common.
  
  Section::::Internal linings.:Polyurethane (PUR).
   Another technique to form tubes instead of using permanent tubing material is to use oiled rods or ropes. The oiled rod or ropes will be placed and mortared into the joints. The oil prevents mortar bond and the rods or ropes can be removed after the mortar is set, creating a hole similar to the use of a tube.
  
  The advantage of the tube type is that it is less conspicuous. However, the small holes may not allow air to circulate and vent out the moisture very well.
  
  Section::::Masonry.:Corrugated channels.
   River Ribble, West Yorkshire
  
  The River Ribble is a minor river running through the town of Holmfirth in Kirklees, West Yorkshire, England.
  
  Rising at the outflow of Holme Styes Reservoir, itself fed by Reynard Clough (which has a tributary, Catholes Gutter), Hades Clough and Long Ing Dike, the Ribble flows northwards, collecting Fox Clough and Beaver Clough from the west, before joining the River Holme by Towngate and Hollowgate in Holmfirth. The confluence of the two rivers was also marked by a weir, but this was removed in 1944 when Italian prisoners of war were tasked with removing it.
   When joining segments of tubular sheet metal pipe, such as for smoke pipes for wood stoves, downspouts for rain gutters, or for installation of ventilation ducting, one end of a tube is treated with a crimping tool to make a slip joint into the next section of duct. The joint will not be liquid-tight but will be adequate for conveying low pressure fluids. Crimp joints may be arranged to prevent accumulation of dirt.
   Spacing is the same on a putlog scaffold as on a general purpose scaffold, and ties are still required.
  
  In recent years a number of new innovations have meant an increased scope of use for scaffolding, such as ladderbeams for spanning spaces that cannot accommodate standards and the increased use of sheeting and structure to create temporary roofs.
  
  Section::::Specialty scaffolding.:Pump-jack.
  
  A pump-jack is a type of portable scaffolding system. The scaffold rests on supports attached to two or more vertical posts. The user raises the scaffolding by pumping the foot pedals on the supports, like an automobile jack.
   The heading course in English garden wall bond sometimes features bricks of a different colour to its surrounding stretchers. In English chalk districts, flint is substituted for the stretchers, and the headers constitute a lacing course.
  
  Section::::Load-bearing bonds.:Two or more stretching course per heading course.:Scottish bond.
  
  This bond has five courses of stretchers between every course of headers.
  
  The lap is generated by the use of headers as quoins for the even numbered stretching courses, counting up from the previous heading course, with queen closers as the penultimate brick at either end of the heading courses.
   BULLET::::- Soldier: A brick laid vertically with its long narrow side exposed
  
  BULLET::::- Squint: A brick that is specially made to bond around external quoins of obtuse angles. Typically 60 or 45 degrees.
  
  BULLET::::- Stopped end: The end of a wall that does not abut any other component.
  
  BULLET::::- Stretcher: A brick laid flat with its long narrow side exposed
  
  BULLET::::- Toothing: The forming of a temporary stopped end in such a way as to allow the bond to continue at a later date as the work proceeds.
  