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Introduction to the analysis and design of excavations
Published in Chang-Yu Ou, Deep Excavation, 2014
When Terzaghi (1943) was first considering the stability of excavations, he defined those whose excavation depths were smaller than their widths as shallow excavations while those with depths larger than their widths were deep excavations. Years later, Terzaghi and Peck (1967), and others, including Peck et al. (1977), revised that excavations whose depths were less than 6m could be defined as shallow excavations and those deeper than that as deep excavations, considering that use of sheetpiles or soldier piles grows uneconomical once the excavation depth goes beyond 6m. Generally speaking, the analysis methods for shallow excavations are comparatively simple. In fact, more and more excavation projects are located in populous urban areas. To avoid damage to adjacent properties caused by excavation, diaphragm walls are commonly used as retaining walls. What's more, computer programming has done most of the job of analysis and design, which applies to all depths, following the same theories. Therefore, it is not meaningful to distinguish between deep and shallow excavations any more.
Earthquake Effects on Buildings
Published in Bungale S. Taranath, Tall Building Design, 2016
Diaphragms are classified into one of three categories: rigid, flexible, or semirigid. Rigid diaphragms are those that possess the strength and stiffness to distribute the lateral forces to the lateral-force-resisting frames in proportion to the relative stiffness of the individual frames, without significant deformation in the diaphragm. On the other hand, the distribution of the lateral forces through a flexible diaphragm is independent of the relative stiffness of the lateral-force-resisting frames.
Design
Published in Ajaya Kumar Gupta, Peter James Moss, Guidelines for Design of Low-Rise Buildings Subjected to Lateral Forces, 2020
Edwin G. Zacher, Coley Altman, Douglas A. Foutch, Louis F. Geschwinder, Melvyn Green, Mark Schaefer, Mete A. Sozen, John R. Tissel
A diaphragm is an approximately horizontal structural system that transfers the lateral forces applied to a structure to vertical structural elements for transfer to the foundation. In typical building design, the lateral forces are from wind or seismic forces. The resisting elements are often shear walls (vertical diaphragms) but may be vertical trusses and, where resisting elements are placed only at the perimeter, may be moment resisting frames.
Empirical Performance Levels of Strengthened Masonry Buildings Struck by the 2016 Central Italy Earthquake: Proposal of a New Taxonomy
Published in International Journal of Architectural Heritage, 2023
Luca Sbrogiò, Ylenia Saretta, Maria Rosa Valluzzi
Horizontal diaphragms, i.e., roofs and floors, were categorized according to their stiffness, as flexible (F), semi-rigid (S) or rigid (R). In this work, only a 5 cm-thick r.c. slab was considered as in-plane rigid (MIT 2018), and the other conditions were determined as a function of the subfloor (in-plane stiffness) and the bearing elements (out-of-plane stiffness). Similarly to masonry, interventions could aim at strengthening (improvement), or at replacing (upgrading), the existing diaphragms, acting on the bearing elements and the subfloors as well, thus determining the final stiffness. Local interventions, which consisted of a simple strengthening to vertical loads of bearing elements, had a limited effect on the overall seismic performance and they were difficult to observe. As a result of the application to the sample of the methodology given in Figure 12 (apart local interventions), a systematic mapping of the stiffness of horizontal structures, observed on site, resulting from construction types and interventions, is presented in Table 4.
The impact of service core reduction in supertall buildings: a study on structural design, embodied carbon, and leasable floor area
Published in Architectural Science Review, 2023
Beste Fakıoğlu Gedik, Bekir Özer Ay
The aspect ratio is defined as the ratio of the building height to the narrowest structural width in the plan (Zils and Viise 2003). Zils and Viise (2003) claimed that, for buildings where structural elements at perimeter considerably contribute to the lateral load resisting system, an aspect ratio of 8 is feasible. As shown in Table 1, this value is also compatible with the median aspect ratio of the case study building set that includes existing office buildings with an outriggered frame system. Thus, the aspect ratio of generic buildings is determined as 8 in this study, which yields floor plan dimensions as 37.5 × 37.5 m (1406.25 m2 as the typical floor area). 30 cm thick reinforced concrete solid slabs are used in all the generic building models. Regarding their in-plane stiffness property, the floor diaphragms are defined as semi-rigid. Table 2 lists the main design parameters of the generic models.
Experimental and numerical study on the in-plane behaviour of a new long-span assembly composite floor system under lateral load
Published in Journal of Asian Architecture and Building Engineering, 2022
Zaihua Zhang, Ran He, Gangxiang Mao, Xingping Shu
Floor diaphragms are important structural elements in a building system, with the purpose of carrying both vertical and lateral loads. Usually in structural design, a great deal of attention is given to the vertical lateral load resisting elements (moment frames, shear walls and bracing), while the equally critical horizontal lateral load resisting elements (diaphragms) are usually ignored (Scarry 2014). In fact, as the horizontal resistance component of the structure, the floor system contains most of the gravity of the building structure, once the diaphragms cannot sustain the seismic forces they are subjected to, and transfer those forces properly to the vertical lateral load resisting elements, those vertical lateral load resisting elements may as well not be there. Especially for assembly floor structures, the connection between the assembled units is relatively weak, and the in-plane performance of this type of floor should be paid more attention.