Some arch uses, such as barrel vaults and domes, can be completely self-supporting even while being built. However, most modern uses of the masonry arch need suitable shoring and bracing. During construction, both structural and non-structural arches should be appropriately supported. Once the building is completed, internal or external systems must be put in place to prevent any one part of the arch from collapsing.
The three main types of masonry arches are round, pointed, and segmental. A fourth type, called a Pratt, was once popular but is now used only in special cases where a round or pointed arch would interfere with door openings or window frames.
Round arches have the advantage of simplicity and ease of construction. They require no detailed drawing for their design and can be erected in any size without difficulty. However, they cannot be built below ground level because there is no way to brace them against pressure from below. As a result, they are not well suited to high-stress applications like bridge decks or tunnel walls.
Pointed arches add more strength and resistance to compression by having points rather than flat surfaces at each floor level. This makes them useful in applications where round arches might be expected to fail under pressure (such as stadium roofs). However, they are more complex to construct and design, so they are used less often.
Because brick masonry is particularly strong in compression, brick masonry arches can withstand significant loads. Historically, arches were built using unreinforced masonry. Steel reinforcing may be required for very long-span arches and arches with a slight rise to sustain tensile loads. Modern arches are often constructed of reinforced concrete.
Brick arch construction is based on the principle of varying the number and size of bricks used in creating a pattern that will direct most of the compressive force into the center of the arch where it can be resisted by the base material. The key factor in determining how much force an arch can withstand is called its "strength." The strength of an arch is determined by how many square feet of brick wall it takes to support such weight as would cause it to collapse under its own weight. For example, an arch 1 foot wide and 12 feet long supported by brick walls on each side would have a maximum load capacity of about 14,000 pounds.
The type of mortar used to bind the bricks together affects their ability to resist compression forces. A mixture of sand and cement is most resistant to compression; thus, it's ideal for building arches. Other types of mortars include one-third sand and two-thirds pea stone or river gravel. The use of this type of mortar in building bridges requires that they be able to support heavy traffic over long distances until they become too old or weak to do so.
Brick masonry arches are built using temporary shoring, known as "centering," or permanent supports, such as a structural steel angle. Centering is utilized to maintain the weight of a brick masonry arch as well as the loads it supports until the arch itself has achieved adequate strength. Once this occurs, the centering may be removed.
The centering should be able to withstand at least 20% of the total load in order to prevent any damage from occurring. If the centering is not strong enough, then it will have to be replaced which will cause additional costs. The type and size of the centering used depends on the load you expect the arch to support. For example, if the arch is supporting a heavy roof then larger centering should be used compared to an arch under light traffic. Brick masonry arches can reach great heights and weigh hundreds of tons; therefore, they require strong building materials and experienced workers for their construction.
Brick masonry arch construction involves several different types of bricks that are assembled into patterns to create the arch shape. First, vertical posts are erected inside of the footprint of the arch (to avoid damaging surrounding property). Next, the centering is placed between the posts to provide support while the mortar sets up. When complete, the centering is removed leaving only the arch's exterior face brick wall.
Arches are remarkable because they are a completely natural type of bridge. The form of the building is what gives it strength. Additional support or cables are not required for an arch bridge. In fact, a stone arch does not even require mortar. The key to its strength is that shape--the arch itself provides the support you need from an overhead structure.
An arch bridge is most commonly seen in ancient architecture but also appears in modern structures as well. Arches have been used since at least 300 B.C. They were invented by Kirtlel, a Chinese engineer who is considered the father of architecture. Roman architects also used arches, as did many other cultures throughout history. Today, engineers use arches in buildings like bridges and tunnels where they need maximum strength with minimum material.
The word "arch" comes from two Greek words: archaeo meaning "I uncover" and rho meaning "root". This describes how an arch keeps its foundation dry by reaching up into the wet ground.
Arches come in three main shapes: round, pointed, and voussoirs (which look like half shells). These different shapes provide varying amounts of support. Round arches are the weakest but also take the smallest amount of material to build. Pointed arches are next in strength and can be more expensive to construct than round or voussoir arches.
Arches are compressive constructions, which means they do not have tensile stresses. They are self-supporting, held in compression by the force of gravity acting on their weight. This makes them exceptionally sturdy and efficient, allowing them to span greater distances and withstand higher weights than horizontal beams. This is why arches are used in construction projects, such as bridges and buildings.
An arch is a structure that provides support for a load without using pillars. An arch has two major parts: the arch itself and the base upon which it rests. The arch's form is determined by its geometry, but it must be strong enough to carry its intended load. Loads are transmitted through arches in three ways: directly, via ties or supports; and indirectly, via girders or joists.
The word "arch" comes from Greek arktos, meaning "bear". Before the development of engineering techniques, builders would use natural arches when constructing houses or other buildings, especially where wood was available. These required very careful planning and many modificaions were needed over time to avoid damage to the arch.
Today, engineers use models and calculations to design arches. They first study how loads are distributed within a building and then choose an appropriate shape for the arch. The type of arch used will determine what kind of reinforcement is needed.