Hybrid masonry is a new type of building system that uses engineered, reinforced masonry to brace frame structures. Typically, hybrid masonry is implemented with concrete masonry panels used to brace steel frame structures. The basic concept is to attach a reinforced concrete masonry panel to a structural steel frame such that some combination of gravity forces, story shears and overturning moments can be transferred to the masonry. The structural engineer can choose from three different types of hybrid masonry (I, II, or III) and two different reinforcement anchorage types (a & b). In conventional steel frame building systems, the vertical force resisting steel frame system is supported in the lateral direction by steel bracing or an equivalent system. When the architectural plans call for concrete masonry walls to be placed within the frame, extra labor is required to ensure the masonry fits around the steel frame. Usually, this placement does not take advantage of the structural properties of the masonry panels. In hybrid masonry, the masonry panels take the place of conventional steel bracing, utilizing the structural properties of reinforced concrete masonry walls.
The system was first introduced by David Biggs, PE in 2007 at the 10th North American Masonry Conference and was based on historical masonry construction [1] and the practice of anchoring masonry walls in steel frames for out of plane strength. [2]
There are five different configurations of hybrid masonry. They consist of three different main types with two subsets; however, the first type does not allow both subsets. The three types consist of different constraint conditions within the steel frame and the two subsets are based on the anchoring of the vertical reinforcement in the masonry panel.
Type I hybrid masonry has no direct contact with the surround steel frame. For this reason, there are not two subsets of this configuration. Lateral forces are transmitted to the masonry panel through steel plates that are connected to the floor beams and attached to the wall with a through-bolt. The hole in the plate for the through-bolt is slotted so that gravity loads are not transmitted to the masonry panel; the vertical loads travel solely through the steel frame. Thus, the masonry panel takes only the story shear from the above floors and acts as a one story shear wall.
The steel plates can be designed in two manners. If the design engineer wishes the steel plate to be the weak point, the plate can be designed as a fuse. The fuse would dissipate energy after yielding and be easily replaced after an extreme event. Alternatively, the plate can be designed so it does not yield before the masonry panel experiences significant damage. A strong plate would localize the damage to the masonry.
Type II hybrid masonry is constrained vertically by the steel frame; however, the sides of the panel still have a gap between the steel and the masonry. The vertical contact transfers the gravity load from the beam into the masonry panel, increasing its flexural and shear strength. Instead of the plates transferring the lateral force from the steel to the masonry, shear studs are welded to the bottom side of the beam. Grout is then used to fill the space between the masonry and the steel beam. With this contact, the wall is subject to story shears, gravity loads, as well as overturning moments much like a continuous shear wall.
The two subsets of Type II hybrid masonry are Type IIa and Type IIb. The difference between the two systems are whether the vertical reinforcement is anchored into the base or to the steel beam. In Type IIa, the vertical reinforcement is anchored and can develop tension forces along its length. The vertical reinforcement is not anchored in Type IIb hybrid masonry and consequently the rebar cannot take the force on the tension side of the wall. Instead, the top of the wall undergoes compression. [3]
Similar Type II hybrid masonry, Type III hybrid masonry has the vertical confinement. In addition to the vertical contact with the beam, contact with the columns is also used for horizontal confinement. Shear studs are welded on the insides of the columns to transfer vertical forces that are the result of axial load in the columns as well as shear in the wall. The wall system resembles infill masonry in terms of confinement in the steel, yet differs in that it is grouted and reinforced, allowing for a more ductile response.
Prof. Ian Robertson at the University of Hawaiʻi -Mānoa(UHM) has developed and tested the steel plate connections between the masonry. The result was a design method of a fuse plate that yields along its entire length, with the aim of creating a ductile energy dissipating fuse. Bolt pullout tests were also performed at UHM to validate the strength of the masonry with through bolts. A research team at Rice University develops computational models for the study of hybrid masonry structural systems. Profs. Larry A. Fahnestock and Daniel P. Abrams are performing full scale experimental tests on hybrid masonry at the Network for Earthquake Engineering Simulation(NEES) site at the University of Illinois at Urbana-Champaign. [4]
Masonry (noun) is the building of structures from individual units, which are often laid in and bound together by mortar; the term masonry can also refer to the units themselves. The common materials of masonry construction are brick, building stone such as marble, granite, and limestone, cast stone, concrete block, glass block, and adobe. Masonry is generally a highly durable form of construction. However, the materials used, the quality of the mortar and workmanship, and the pattern in which the units are assembled can substantially affect the durability of the overall masonry construction. A person who constructs masonry is called a mason or bricklayer. These are both classified as construction trades.
Reinforced concrete (RC) (also called reinforced cement concrete or RCC) is a composite material in which concrete's relatively low tensile strength and ductility are counteracted by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars (rebar) and is usually embedded passively in the concrete before the concrete sets. Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and/or structural failure. Modern reinforced concrete can contain varied reinforcing materials made of steel, polymers or alternate composite material in conjunction with rebar or not. Reinforced concrete may also be permanently stressed, so as to improve the behaviour of the final structure under working loads. In the United States, the most common methods of doing this are known as pre-tensioning and post-tensioning.
Rebar, known when massed as reinforcing steel or reinforcement steel, is a steel bar or mesh of steel wires used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has weak tensile strength. Rebar significantly increases the tensile strength of the structure. Rebar's surface is often "deformed" with ribs, lugs or indentations to promote a better bond with the concrete and reduce the risk of slippage.
Retaining walls are relatively rigid walls used for supporting soil laterally so that it can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to. They are used to bound soils between two different elevations often in areas of terrain possessing undesirable slopes or in areas where the landscape needs to be shaped severely and engineered for more specific purposes like hillside farming or roadway overpasses. A retaining wall that retains soil on the backside and water on the frontside is called a seawall or a bulkhead.
A beam is a structural element that primarily resists loads applied laterally to the beam's axis. Its mode of deflection is primarily by bending. The loads applied to the beam result in reaction forces at the beam's support points. The total effect of all the forces acting on the beam is to produce shear forces and bending moments within the beam, that in turn induce internal stresses, strains and deflections of the beam. Beams are characterized by their manner of support, profile, equilibrium conditions, length, and their material.
Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers, the need of seismic retrofitting is well acknowledged. Prior to the introduction of modern seismic codes in the late 1960s for developed countries and late 1970s for many other parts of the world, many structures were designed without adequate detailing and reinforcement for seismic protection. In view of the imminent problem, various research work has been carried out. State-of-the-art technical guidelines for seismic assessment, retrofit and rehabilitation have been published around the world – such as the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)'s guidelines. These codes must be regularly updated; the 1994 Northridge earthquake brought to light the brittleness of welded steel frames, for example.
In structural engineering, a shear wall is a vertical element of a seismic force resisting system that is designed to resist in-plane lateral forces, typically wind and seismic loads. In many jurisdictions, the International Building Code and International Residential Code govern the design of shear walls.
Earthquake engineering is an interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to earthquakes. An earthquake engineer aims to construct structures that will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake. Earthquake engineering is the scientific field concerned with protecting society, the natural environment, and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels. Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to seismic loading; it is considered as a subset of structural engineering, geotechnical engineering, mechanical engineering, chemical engineering, applied physics, etc. However, the tremendous costs experienced in recent earthquakes have led to an expansion of its scope to encompass disciplines from the wider field of civil engineering, mechanical engineering, nuclear engineering, and from the social sciences, especially sociology, political science, economics, and finance.
Steel frame is a building technique with a "skeleton frame" of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The development of this technique made the construction of the skyscraper possible.
Formwork is temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering molds.
Anchor bolts are used to connect structural and non-structural elements to the concrete. The connection is made by an assembling of different components such as: anchor bolts, steel plates, stiffeners. Anchor bolts transfer different types of load: tension forces and shear forces. A connection between structural elements can be represented by steel column attached to reinforced concrete foundation. Whereas, a common case of non-structural element attached to a structural one is represented by the connection between a facade system and a reinforced concrete wall.
Glass fiber reinforced concrete or GFRC is a type of fiber-reinforced concrete. The product is also known as glassfibre reinforced concrete or GRC in British English. Glass fiber concretes are mainly used in exterior building façade panels and as architectural precast concrete. Somewhat similar materials are fiber cement siding and cement boards.
In structural engineering, the tube is a system where, to resist lateral loads, a building is designed to act like a hollow cylinder, cantilevered perpendicular to the ground. This system was introduced by Fazlur Rahman Khan while at the architectural firm Skidmore, Owings & Merrill (SOM), in their Chicago office. The first example of the tube’s use is the 43-story Khan-designed DeWitt-Chestnut Apartment Building, since renamed Plaza on DeWitt, in Chicago, Illinois, finished in 1966.
A steel plate shear wall (SPSW) consists of steel infill plates bounded by boundary elements.
Voided biaxial slabs, sometimes called biaxial slabs, are a type of reinforced concrete slab which incorporates air-filled voids to reduce the volume of concrete required. These voids enable cheaper construction and less environmental impact. Another major benefit of the system is its reduction in slab weight compared with regular solid decks. Up to 50% of the slab volume may be removed in voids, resulting in less load on structural members. This also allows increased weight and/or span, since the self-weight of the slab contributes less to the overall load.
An anchor plate, floor plate or wall washer is a large plate or washer connected to a tie rod or bolt. Anchor plates are used on exterior walls of masonry buildings, for structural reinforcement. Being visible, many anchor plates are made in a style that is decorative.
Cellular confinement systems (CCS)—also known as geocells—are widely used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth retention. Typical cellular confinement systems are geosynthetics made with ultrasonically welded high-density polyethylene (HDPE) strips or novel polymeric alloy (NPA)—and expanded on-site to form a honeycomb-like structure—and filled with sand, soil, rock, gravel or concrete.
A T-beam, used in construction, is a load-bearing structure of reinforced concrete, wood or metal, with a T-shaped cross section. The top of the T-shaped cross section serves as a flange or compression member in resisting compressive stresses. The web of the beam below the compression flange serves to resist shear stress and to provide greater separation for the coupled forces of bending.
The Filigree Wideslab method is a process for construction of concrete floor decks from two interconnected concrete placements, one precast in a factory, and the other done in the field. The method was developed during the late 1960s by Harry H. Wise as a more efficient and economic construction process than conventional cast-in-place technologies.
The infill wall is the supported wall that closes the perimeter of a building constructed with a three-dimensional framework structure. Therefore, the structural frame ensures the bearing function, whereas the infill wall serves to separate inner and outer space, filling up the boxes of the outer frames. The infill wall has the unique static function to bear its own weight. The infill wall is an external vertical opaque type of closure. With respect to other categories of wall, the infill wall differs from the partition that serves to separate two interior spaces, yet also non-load bearing, and from the load bearing wall. The latter performs the same functions of the infill wall, hygro-thermically and acoustically, but performs static functions too.