The overall seismic response was evaluated in terms of the modal parameters, characteristics of pushover curves and the deformed shape of the floors. The assumption of rigid floor diaphragms is often used to simplify engineering analyses without significant loss in the accuracy of seismic response prediction for most buildings. importance is the in-plane rigidity of the diaphragm relative to the walls or frame elements that transmit the lateral forces to the ground (Figure 4-29). The reinforced concrete slabs act as a rigid diaphragm. This paper presents a design procedure covering the diaphragm action of a hybrid floor slab comprising of Dramix steel fibre reinforced concrete (SFRC) topping on profiled metal sheeting. In addition, results show that diaphragm flexibility changes the seismic response of the structures and linear analysis is not sufficient to explain this behavior. The in-plane shear force per unit length is assumed to be uniform along the depth of the diaphragm when the rigid diaphragm method of analysis is used. Diaphragm flexible. Figure 5. Karadogan, H. F.; Huang, T.; Lu, L. W.; and Nakashima, M., 1980, These testing procedures are meant to serve as a guide to inspectors while performing evaluations using a specific NDE method. Type of Roof System : Roof … Moreover, if the floor slab panels experience cracking or yielding due to pronounced in-plane distortions, the seismic response of the entire building system may be significantly altered. A three-dimensional analysis that considers the relative rigidities of the diaphragm and the elements of the LFRS provides the most accurate distribution of the forces in these components. Different intensities of earthquake load, 0.05g, 0.10g, 0.15g and 0.20g are applied to the structures to know the maximum allowable earthquake load intensities for the buildings. This paper presents a design procedure covering the diaphragm action of a hybrid floor slab comprising of Dramix steel fibre reinforced concrete (SFRC) topping on profiled metal sheeting. The building was analyzed using Finite Element Modelling (FEM) under different types of analyses using IDARC 2D depend on variety of earthquake intensities from Time History Analysis (THA) considering low to medium earthquake intensities. Where the width of the collectors is equal to the thickness of the wall, all the tension and compression forces from the collector are transferred directly into the boundary of the wall, and Avf is determined using the above equation based on the uniform shear along the length of the wall (which is equal to RA/L2). These, in turn, can be used to determine the mode shapes of the system and the participation factors for earthquake response. For diaphragms with openings, forces develop in the sub-diaphragms at the top and bottom of the opening and collector elements on each side of the opening are required to transfer the diaphragm shear into the sub-diaphragms (, An equivalent distributed load on the diaphragm can be obtained based on the reactions in the springs. A case study that has been conducted on medium-rise reinforced concrete buildings which are mostly categorized as moment resisting frames. 137-142. Engineers should concern and consider the loading for reinforced concrete building due to earthquake in Malaysia’s building design procedure. Various strand and grout defects were fabricated and placed into the full-scale post-tensioned girder and large scale stay-cable mock-up specimens for the evaluation of the NDE methods. The level of the damage state (minor, moderate, major, collapse levels) has been defined as well. The influence of stiffening the floor system was analyzed by applying conventional stiffening interventions to the two-floor systems common in the Eixample-Barcelona district. The force reduction factor of a wall panel with opening is much less when compared with fully reinforced wall panel with no opening. Tension forces govern, so the required area of chord reinforcement, As, can be determined from the following equation: where φ = 0.9. In contrast, the distribution of in-plane forces due to wind effects in diaphragms is complex. For the seismic force resistance, a dual system combining ordinary RC shear walls and intermediate slab–column moment frames was used at the upper portion, while a building frame system of ordinary RC shear walls was used at the lower portion of the structure. State University of New York at Buffalo, Buffalo, N.Y., July. In-plane design bending moments, shear forces, and axial forces in a diaphragm are permitted to be calculated by the methods in ACI 318 Section 12.4.2.4: For reinforced concrete buildings with typical span lengths and without diaphragm irregularities (such as large openings or significant changes in diaphragm stiffness in adjoining stories), the rigid diaphragm model is commonly used to determine approximate force distributions within a diaphragm. Under seismic loading, floor and roof systems in reinforced concrete (RC) buildings act as diaphragms to transfer lateral earthquake loads to the vertical lateral force-resisting system (LFRS). Perturbation techniques are also applied to simplify further the determination of the fundamental frequency of such single-storey structures. However, for certain classes of structures, such as long and narrow buildings (especially with dual-braced lateral load-resisting systems), and buildings with horizontal (T- or L-shaped) or vertical (setbacks or cross-walls) offsets, the effect of diaphragm flexibility cannot be disregarded. Comparison between flexible and rigid diaphragm . Ignoring the effects of diaphragm flexibility can lead to non-economic or unsafe structural design. We aim to close the gap to the industry by improving the awareness about latest trends in Civil Engineering. 83-100. In multi-storey constructions all other floors have RCC floor slabs. Design and Detailing of Low-Rise Reinforced Concrete Buildings. Rigid Diaphragm vs Semi Rigid or Simple Truss Diaphragm Semi Rigid or S&T Diaphragm forces are extracted from within the diaphragm using "Behavior of Flat Plate Floor Systems Under In-Plane Seismic Loading," Under seismic loading, floor and roof systems in reinforced concrete (RC) buildings act as diaphragms to transfer lateral earthquake loads to the vertical lateral force-resisting system (LFRS). The building performed the early yielding point at 3.115 s for beam element at intensity 0.20 g. Based on result, the critical frame 2A/F–B of the building can stand an earthquake happen with intensity up to 0.20 g. There is no structural damage but some non-structural damage is expected in the non-linear analysis of modal frames which indicates that the building was categorized in the light damage level. The shear transfer between the diaphragm and wall A in Figure 4 depends on the width of the collector elements. Flexibility on Seismic Response of Building Structures," Proceedings of Chord reinforcement must also be located around large openings and must be properly developed within the slab. Case Study. The Quarters Tentera Laut Diraja Malaysia (TLDM) Langkawi, Kedah was chosen as a main model for this study. Proceedings of the Seventh World Conference of Earthquake Engineering, Even when this conservative approach is used, shear strength requirements are commonly satisfied. In current practice, horizontal diaphragms are typically assumed to be rigid, thus neglecting the effect of their in-plane movement relative to the vertical LFRS. The method begins by treating the floors as bending beams and the walls as shear beams. In the structural analysis of buildings, rigid floor assumption is one of these methods. Hamburger, R. O., 1996, "Department Store, Northridge Fashion system. Previously proposed force and displacement criteria were used to assess their behavior as diaphragm. It is closely related to that part of the strong motion which contributes significantly to the seismic energy as recorded at a point and to the related spectral amplitudes. In typical cast-in-place reinforced concrete construction, this is accomplished by shear transfer reinforcement, which usually consists of dowel bars. The inelastic behaviour of diaphragms is emphasized through a study of narrow rectangular buildings with end walls. In the case of gravity loads, many methods are available that can be used to determine the factored load effects, including the approximate methods in ACI 318 for one-way and two-way systems. Variations on this model allowed factors affecting the response to be studied. concrete cover is required (see Table A-4.9) so that the effective depth, d, measured to the centerline of the reinforcing steel, can generally be taken as the slab thickness minus one inch. A study devoted to define the diaphragm condition using linear-elastic analyses for structures with the most widely used floor systems in Mexico (two-way ribbed RC slabs, beam and block, steel decks and waffle RC flat slabs is presented. The results showed that for both single story structures the ultimate strength of the diaphragms was very high about 20 to 33 times of the seismic load specified in Iran's seismic code, however the ultimate strength of the second model, where the joists direction was perpendicular to the lateral load direction, was considerable showing a reduction about 50~60% compared to the ultimate strength of the first model, where the joists direction was parallel to the lateral load direction. While Include in diaphragm is the only property used to determine diaphragm action in roof panels, for slab items the diaphragm properties are also determined by the:. The numerical analyses have enabled to give interesting indications about the reliability of the hypothesis of rigid floors as the investigated parameters change. Because the wall on the left does not extend the full depth of the diaphragm, collector elements are needed to collect the shear from the diaphragm and to transfer it to the wall. The study indicates that the plastic hinge initially formed on the column at the lower storey level for both low and high rise building frames. 283-294. diaphragm flexibility on the redistribution of lateral forces to the vertical structural system after the floor slab system has ., experienced inelastic deformation. The derived response reduction factors will be useful for the design of reinforced HCBM wall panels subjected to lateral forces generated due to earthquakes. The following equation can be used to determine the required area of the dowel bars Avf for shear transfer: For hardened concrete that is clean, free of laitance, and not intentionally roughened, μ = 0.6 for normalweight concrete in the typical case where the slab and wall are cast at different times. Publication 356, Federal Emergency Management Agency, FEMA, 565-570. The reinforcing bars must extend at least the tension development length, ld, determined in accordance with ACI 318 Section 25.4.2, past the inside face of the wall and past the underside of the slab. American Society of Civil Engineers (ASCE), 2000, "Prestandard An equivalent distributed load on the diaphragm can be obtained based on the reactions in the springs. Jain, S. K., and Jennings, P. C., 1985, "Analytical Models For Low-Rise Diaphragms may be constructed of structural materials, such as concrete, wood, or metal in various forms. The earthquake study is relevant even though Malaysia is outside the earthquake region but still had experienced and did suffer from major cases in the past like tsunami. This system is characterized by cast-in-place, load-bearing, reinforced concrete shear walls in both principal directions. The study has been firstly developed via the implementation of three-dimensional finite element models simulating the real geometry of the floors. The masonry walls thus act as shear walls. Concrete (ACI 318-99) and Commentary (318R-99)," American Conc rete ; and Huang, T., In the usual case where the resultant wind force does not act through the center of rigidity (either due to geometry or minimum eccentricity requirements in the governing building code), a floor will translate and rotate. The study addresses the earthquake study due to performance of critical frame reinforced concrete building which were subjected to low-intensity earthquakes effects. Damage Analysis of Reinforced Concrete Frame Shear-Wall Structures," Chen, S. J.; Huang, T.; and Lu, L. W., 1989, "Diaphragm Behavior of Design Biaxial Base Plates Using ASDIP STEEL, Define Material Properties – midas Civil for Beginners, Define Section Properties – Midas Civil for Beginners, Variety of Dead Loads Application – Midas Civil for Beginners, ENERCALC Structural Engineering Library 10.18.12.31 + RetainPro 11.18.12.04, Guideline for Condition Assessment of the Building Envelope: (ASCE Standard), Design Loads on Structures during Construction, Design Ground Beams, Rafts & Pile Caps in MasterSeries, Calibration of the Live Load Factor in LRFD Design Guidelines. In this method, a diaphragm is modeled as a horizontal rigid beam that is supported by springs which represent the lateral stiffness of the members in the LFRS. Cast-in-place, reinforced concrete slabs of typical proportions and span lengths can usually be considered rigid diaphragms, which means that the lateral forces are transferred to the elements of the LFRS in proportion to their relative rigidities. CRSI (Concrete Reinforcing Steel Institute). "Concrete Parking Structures," Earthquake Spectra, Supplement C to In recent years, the study of the influence of floor system flexibility on the seismic behavior of buildings, particularly URM buildings, has focused on low-rise buildings. The lateral loads in these structures are distributed to the walls through the RCC slab. 1989, Tena-Colunga 1992, Tena-Colunga y Abrams 1992, Ju y Lin 1999, De la Colina 1999, Fleischman y Farrow 2001, Doudoumis y Athanatopoulou 2001, Fleischman et al. A greater damage index means that the members yield earlier and the plastic rotation is larger and vice versa. I used to assume that all reinforced concrete slabs can be treated as rigid diaphragms. ACI 318-14, Farmington Hills, Michigan. Following, other authors studied aspects related to in-plan irregularity effects and dynamic parameters of buildings analyzed (periods, participating mass), through different modeling methods and using the hypothesis of rigid floor or not [3, ... of the in-plane flexibility. Correlations have been established between the duration of strong-motion acceleration, velocity, and displacement and Modified Mercalli intensity, earthquake magnitude, the type of recording site geology, and epicentral distance. This study addresses the vulnerability of public buildings in Malaysia subjected to earthquakes from Sumatra and Philippines. An analytical modeling scheme is developed to include the inelastic effects of flexible floor diaphragms in the analysis of reinforced concrete buildings. The models were analyzed under lateral loading. Sacramento, Calif., pp. Roof panels and slabs will both act as a diaphragms provided they have Include in diaphragm checked in their properties.. Diaphragms are usually constructed of plywood or oriented strand board in timber construction; metal deck or composite metal deck in steel construction; or a concrete slab in concrete construction. Also, during earthquake, slabs act as rigid diaphragm due to its rigidity in the in plane direction. The diaphragm of a structure often does double duty as the floor system or roof system in a building, or the deck of a bridge, which simultaneously supports gravity loads. However, previous experimental and analytical research reported that the diaphragm fl exibility of RC slabs might signifi cantly affect lateral force distributions in structures with shear walls (Panahshahi et al., 1991;Pantazopoulou and Imran, 1992; Performance Based Evaluation of the Seismic Resistance of Structures with Concrete Diaphragms. T.RangaRajan. The models were analyzed under lateral loading. Based on the results, it was found that all buildings can withstand an earthquake occurrence with intensity up to 0.20g. Two variables that favor the potential flexibility of the diaphragm were assessed in the research: a) the plan aspect ratio of buildings and, b) the stiffness of the floor system. The roof and floor systems act as the web of the beam, which resists the design shear forces that are uniform through the depth of the diaphragm. 8 (eight) reinforced concrete buildings which are mostly categorized as moment resisting frames has been selected for vulnerability study. Presented here are an extended description and the results of an experimental study of the shaking-table response of a scaled-model structure, and its pertinent component tests. 3.2, Sacramento, Calif., pp. This paper presents a new analytical method for the dynamic analysis of some one- and two-storey buildings whose floors may have significant in-plane flexibility. We leave … In this study, the linear elastic design analysis is carried out modeling floors as rigid diaphragm and flexible diaphragm. Panahshahi, N.; Kunnath, S. K.; Reinhorn, A. M.; Lu, L.W. steel, concrete, or combinations of these. rocedures were developed for the various NDE methods that were used for the evaluation of the mock-up specimens. Combinations of such materials are also possible. Figure R12.1.1 in Reference 1 depicts typical diaphragm actions in a reinforced concrete building. 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