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The Structural Design of an LDS Church
The Church of Jesus Christ Latter-Day Saints Structural Model (Produced in RAM Frame) The entire structure is supported on a three foot thick monolithic two-way conventionally reinforced concrete mat foundation. This system was used per the Geotechnical Engineer’s recommendations and will reduce differential settlement of the structure due to poor underlying soil conditions and varying water tables that are influenced by the tides of the Charles River. This system will also provide the necessary weight to reduce the buoyancy of the structure when acted on by a design uplift... Under the column-supported slab lies the slab on grade. This slab consists of a five inch thick slab that is cast against fill soil that had been packed using a vibration machine to limit settlement of the slab. Welded wire mesh has been provided at mid-depth of the slab to limit temperature and shrinkage cracking of the slab. This mesh shall be laid in all areas of the slab on grade and #4 bars shall be placed at 12” spacing around the entire perimeter of the parking garage to allow for... During the systems studies, we performed analyses of three systems for the column-supported slab. We looked at a two-way conventionally reinforced slab, a one-way post-tensioned slab, and a two-way post-tensioned slab. Our final design decision to choose the two-way conventionally reinforced slab was based on the constraints of this project. The clear spans between columns are short and controlled by the steel superstructure above the garage. A second problem was the presence of the many... The steel superstructure structural system chosen was a concrete on metal deck system supported by composite beams and columns. The deck chosen was an 18-gage, 1.5” LOK – Floor with 3.5 inches of normal weight concrete cover. The concrete cover required was chosen to satisfy the one hour fire rating of the building. The 18-gage 1.5” LOK-Floor was chosen to maximize the spans between support beams without adding excessive deck weight. A composite beam and girder system was chosen to... The second floor diaphragm was designed according to both the 2006 version of IBC and ASCE 7-05 Chapter 12 (which details the seismic design requirements for building structures). The diaphragm of the second floor was designed with heavy consideration of the multiple floor openings. Seismic weights were collected from RAM Frame software and then tributary façade loads were added to obtain the total seismic weights acting on the diaphragm. All demands for the diaphragm were then determined... Numerous roof top units and air handlers were located on the roof of the church. Due to the large number of units, the roof was designed for an equivalent uniformly distributed live load instead of only designing for the weight of the units in their exact locations. A worst case scenario was chosen when calculating the equivalent uniform live load. It was assumed that two of the heaviest units would be placed in the middle of the longest span of the roof. The forces within the beam due to this... Located above the chapel on the south side of the building is a 45’ tall prefabricated steeple. The steeple is to be designed and installed by a company of the construction manager’s choosing and frames into the structural system of the building by four posts. Due to the height and location of the steeple, it is subject to large wind loads that are transferred to the structural system as axial forces, shear, and torsion. In order to efficiently resist the torsion on the steeple supports... The baptismal font is located on the north side of the church adjacent to the Bible study/meeting room and bathrooms on the first floor. The font consists of an opening in the slab, including concrete steps into a pool of water with a total depth of over 3’. The font loads were supported by steel beams which were hung from the steel beam supports on the first floor at one end and the structural concrete wall on the other end. Due to the large span between beams supporting the font, a... The area in question for this design is along gridline 1 and roughly between gridlines J and M. In all other section of the exterior of the structure, the façade load is carried by the exterior retaining walls. In this section, however, the façade load is carried by a beam and transferred to columns that take the load to the ground. Additionally, a precast concrete arch must be hung from this beam so that the aesthetic of the entrance matches that of the entire exterior of the structure. A... This structure contains many large study rooms that have the ability to be transformed into smaller study rooms through the use of foldable partitions. These partitions weigh approximately 9 psf of surface area and are present in five locations around the structure (with a total of seven partitions). The beams that support these partitions have been designed to resist the gravity load as well as any differential air pressure that may act on one side of the partition. The partition beams are... At the transition from the parking garage to the upper steel superstructure, there are two transfer girders adjacent to both sides of the chapel. The steel columns supporting the top two floors do not align with the concrete columns of the ground floor of the parking garage. The columns in the parking garage are offset in order to maximize parking spaces. Due to this offset, the two story steel column frames into a steel girder which transfers the load into the nearby concrete column. In order... Slab-on-grade details. The retaining wall that runs along gridline 6 between grid K.5 and C that hold back the soil under the slab on grade was designed using a fixed-simple beam, though it was proven that minimum steel controlled the design of this structure. This structure was designed to resist ten feet of active soil pressure on one side of the wall and no pressure or support on the other side, to be conservative in design. A section of this wall can be viewed on Drawing S13-1. The exterior walls were designed... The lateral force resisting system chosen for the building located in Cambridge, Massachusetts was concentrically braced frames. This lateral force resisting system was chosen because it provides the high stiffness required to meet the lateral drift requirements. When choosing the location of the braces, architectural restraints as well as symmetry were taken into account. A symmetric system was desired in order to limit the torsion imposed on the building by the lateral loads. The brace... The lateral force resisting system for the building was also designed as if the building was located in Los Angeles, California. In the high seismic region of Los Angeles an alternate lateral force resisting system had to be chosen. In the end, eccentrically braced frames were chosen to resist the lateral forces, since they provide the stiffness of concentrically braced frames at low level forces and the high ductility of a moment frame system at high level forces. Again, the braces were...

The second floor diaphragm was designed according to both the 2006 version of IBC and ASCE 7-05 Chapter 12 (which details the seismic design requirements for building structures). The diaphragm of the second floor was designed with heavy consideration of the multiple floor openings. Seismic weights were collected from RAM Frame software and then tributary façade loads were added to obtain the total seismic weights acting on the diaphragm. All demands for the diaphragm were then determined...
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The second floor diaphragm was designed according to both the 2006 version of IBC and ASCE 7-05 Chapter 12 (which details the seismic design requirements for building structures). The diaphragm of the second floor was designed with heavy consideration of the multiple floor openings. Seismic weights were collected from RAM Frame software and then tributary façade loads were added to obtain the total seismic weights acting on the diaphragm. All demands for the diaphragm were then determined according to Seismic Design Category B due to the low probability of a seismic event in Cambridge, MA. A SEA-approved example (Section 1E) was implemented as a design reference to find the required area of steel in the diaphragm. After determining that the structure was rigid, the center of rigidity of the diaphragm was located. Two shear wall forces were multiplied by a length-based ratio of each wall’s proximity to the center of rigidity with respect to the opposing wall (this accounted for eccentricity) to obtain design force. The diaphragm was then designed as a pinned beam element in SAP2000, with the two different design forces acting as individual point loads at each pin. Using a system of equations, two counteracting linear loads were then determined. Once the trapezoidal loads were determined, two different moment diagrams were analyzed: one for the uninterrupted diaphragm span and another for the opening. By dividing the moments by the effective span lengths, the tensile chord forces were determined. Division of these chord forces by the yielding strength of A992 steel and the flexural strength reduction factor culminated in the required amount of additional slab reinforcement. The final design is 4-#10 bars placed at least 12 inches away from the slab edge near any slab openings.