• Earthquakes and Structures
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• 제22권3호
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• pp.263-275
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• 2022

Structural collapses can occur as a result of a dynamic amplification of either, the building's seismic response or the ground shaking by local site effects; one of the reasons is a resonance effect due to the proximity of the structural elastic fundamental period TE and the soil fundamental period TS. We evaluate the vulnerability to resonance effects in Guadalajara, México, in a three-step schema: 1) we define structural systems in the building environment of western Guadalajara, in terms of their construction materials and structural components; 2) we estimate TE with different equations, to obtain a representative value in elastic conditions for each structural system; and, 3) we evaluate the resonance vulnerability by the analysis of the ratio between TE and TS. We observe that the larger the soil fundamental period, the higher the resonance vulnerability for buildings with height between 17 and 39 m. For the sites with a low TS, the most vulnerable buildings will be those with a height between 2 and 9 m. These results can be a helpful tool for disaster prevention, by avoiding the construction of buildings with certain heights and structural characteristics that would result in a dangerous proximity between TE and TS.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.564-567
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• 2015

The incorporation of sustainability principles into the structural engineering design of buildings is increasingly important. Historically the focus of improvements to the environmental performance of structures has been operational energy considerations. Current research has highlighted the requirement for changing the approach by increasing the consideration of embodied energy in structures. This research was conducted to build on previous research by the authors in quantifying the contribution of column optimization to the embodied energy performance of concrete framed buildings. Ultimately, the authors intend to develop mechanisms through which sustainable design can be quantified, enabling alleviation prior to construction. Columns are a key structural element to consider as part of this development process. The outcomes of this assessment reinforced previous findings, observing that reduced structural weight as a result of other sustainable design measures carries manifold benefits include column design savings. Through the quantification of the embodied energy outcomes during this research phase, the columns were shown to contribute up to 19.71% of the total embodied energy of the structural system dependent upon construction technique used.

• Steel and Composite Structures
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• 제10권3호
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• pp.207-222
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• 2010

Fire incident in buildings is common, so the fire safety design of the framed structure is imperative, especially for the unprotected or partly protected bare steel frames. However, software for structural fire analysis is not widely available. As a result, the performance-based structural fire design is urged on the basis of using user-friendly and conventional nonlinear computer analysis programs so that engineers do not need to acquire new structural analysis software for structural fire analysis and design. The tool is desired to have the capacity of simulating the different fire scenarios and associated detrimental effects efficiently, which includes second-order P-D and P-d effects and material yielding. Also the nonlinear behaviour of large-scale structure becomes complicated when under fire, and thus its simulation relies on an efficient and effective numerical analysis to cope with intricate nonlinear effects due to fire. To this end, the present fire study utilizes a second-order elastic/plastic analysis software NIDA to predict structural behaviour of bare steel framed structures at elevated temperatures. This fire study considers thermal expansion and material degradation due to heating. Degradation of material strength with increasing temperature is included by a set of temperature-stress-strain curves according to BS5950 Part 8 mainly, which implicitly allows for creep deformation. This finite element stiffness formulation of beam-column elements is derived from the fifth-order PEP element which facilitates the computer modeling by one member per element. The Newton-Raphson method is used in the nonlinear solution procedure in order to trace the nonlinear equilibrium path at specified elevated temperatures. Several numerical and experimental verifications of framed structures are presented and compared against solutions in literature. The proposed method permits engineers to adopt the performance-based structural fire analysis and design using typical second-order nonlinear structural analysis software.

• Steel and Composite Structures
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• 제26권3호
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• pp.361-373
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• 2018

This paper presents the development of finite element (FE) models to simulate the behavior of diagonally stiffened steel plate shear wall systems (SPSWs) with differently shaped openings subjected to a cyclic load. This walling system has the potential to be used for shear elements that resist lateral loads in steel-framed buildings. A number of $\text\tiny{^1/_2}$-scale one-story buildings that were un-stiffened, stiffened and stiffened with opening SPSWs are modeled and simulated using the finite element method based on experimental data from previous research. After validating the finite element (FE) models, the effects of infill plate thickness on the cyclic behavior of steel shear walls are investigated. Furthermore, triple diagonal stiffeners are added to the steel infill plates of the SPSWs, and the effects are studied. Moreover, the effects of a number of differently shaped openings applied to the infill plate are studied. The results indicate that the bearing capacity and shear resistance are affected positively by increasing the infill plate thickness and by adding triple diagonal stiffeners. In addition, the cyclic behavior of SPSWs is improved, even with an opening in the SPSWs.

• 대한건축학회논문집:구조계
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• 제34권4호
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• pp.43-50
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• 2018

The purpose of this study is to improve the seismic performance of RC framed buildings such as piloti buildings and school facilities. For this purpose, a half size RC frame specimen (SFD) was made and the inside of frame was reinforced with steel frame and S type strut steel damper. The experimental results are compared with those of the previous studies under the same conditions. The comparative specimens are non-reinforced specimen (BF) and damper reinforced specimen (AFD) that confined the column with an aramid sheet. As a result of comparing the maximum strength, stiffness degradation and energy dissipation capacity, SFD specimen was evaluated to be better than comparative specimens. According to the experimental results and FE analysis results, it was confirmed that the shear deformation was concentrated in the steel damper. And it was showed that cracks were concentrated at the upper and lower ends of the strut of the S type damper, and the final failure was observed at struts. From this, it was verified that the steel damper appropriately dissipates energy due to the lateral load.

• Steel and Composite Structures
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• 제24권3호
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• pp.277-285
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• 2017

Single-storey industrial buildings are one of the most often type of structures built among various skeletal framed steel constructions. These metallic buildings offer an exceptional opportunity to minimise the material employed, contributing to a more sustainable construction. In particular, the mansard portal frame is a typology made up of broken beams that involves different lengths and discontinuous slopes. This study aims the weight reduction of the standard mansard portal frame with design purposes by means of varying four parameters: the kink position, the eaves-apex slope, the span and the columns height. In this work, we suggest some guidelines that can improve the economical competitive capabilities of their structural design. In all the cases analysed, the joints of the portal frame are placed over the theoretical non-funicular shape to uniform loads. This allows reducing the bending moment and the shear force, but increasing the axial force. In addition, the performance of mansard and typical pitched portal frames submitted to the same boundary conditions is compared in terms of efficiency in the use of steel. In the large majority of the cases, mansard typologies are lighter than the common pitched frames and, hence, more economical.

• Steel and Composite Structures
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• 제10권4호
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• pp.331-348
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• 2010

Ample research effort has been oriented into developing damage indices with the aim of estimating in a reasonable manner the consequences, in terms of structural damage and deterioration, of severe plastic cycling. Although several studies have been devoted to calibrate damage indices for steel and reinforced concrete members; currently, there is a challenge to study and calibrate the use of such indices for the practical evaluation of complex structures. The aim of this paper is to introduce an energy-based damage index for multi-degree-of-freedom steel buildings that accounts explicitly for the effects of cumulative plastic deformation demands. The model has been developed by complementing the results obtained from experimental testing of steel members with those derived from analytical studies regarding the distribution of plastic demands on several steel frames designed according to the Mexico City Building Code. It is concluded that the approach discussed herein is a promising tool for practical structural evaluation of framed structures subjected to large energy demands.

• Structural Engineering and Mechanics
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• 제46권4호
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• pp.487-504
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• 2013

In the present work a new friction device, with a set of single or double rotational friction flanges and a link element, is described and tested. The mechanism may be applied for the strengthening of existing r/c or steel buildings as well as in new constructed buildings. The device has selectable variable behavior in different levels of displacement and an interlock mechanism that is provided by the link element. The link element may be designed to lock at preselected level of displacement, offering in this way an extra safety reserve against strong earthquakes. A summary of the existing literature about other similar mechanisms is initially presented in this paper. The proposed mechanism is presented and described in details. Laboratory experiments are presented in detail and the resulted response that proves the efficiency of the mechanism at selectable levels of strength capacity is discussed. Drawings of the mechanism attached to a r/c frame with connection details are also included. Finally a dynamic analysis of two r/c frames, with and without the proposed mechanism attached, is performed and the resulted response is given. The main conclusion is that the proposed mechanism is a cheap and efficient devise for the improvement of the performance of new or existing framed buildings to seismic loads.

• Structural Engineering and Mechanics
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• 제24권3호
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• pp.323-337
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• 2006

In this paper, the hysteretic behaviors of channel and C-section cold-formed steel members (CFSMs) under cyclic axial loading were simulated with the finite element method. Geometric and material nonlinearities, Bauschinger effect, strain hardening and strength improvement at corner zones were taken into account. Extensive numerical results indicated that, as the width-to-thickness ratio increases, local buckling occurs prematurely. As a result, the hysteretic behavior of the CFSMs degrades and their energy dissipation capability decreases. Due to the presence of lips, the hysteretic behavior of a C-section steel member is superior to that of its corresponding channel section. The intermediate stiffeners in a C-section steel member postpone the occurrence of local buckling and change its shapes, which can greatly improve its hysteretic behavior and energy dissipation capability. Therefore, the CFSMs with a large width-to-thickness ratio can be improved by adding lips and intermediate stiffeners, and can be used more extensively in residential buildings located in seismic areas.

• 국제초고층학회논문집
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• 제10권4호
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• pp.265-283
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• 2021

To ensure that fire induced collapse of a building is prevented it is important to understand the sequence of events that can lead to this event. In this paper, the initiation of collapse mechanisms of generic a multi-storey steel frame subjected to vertical and horizontal travelling fires are analysed computationally by tracking the formation of plastic hinges in the frame and generation of fire induced loads. Both uniform and travelling fires are considered. In total 58 different cases are analysed using finite element software LS-DYNA. For the frame examined with a simple and generic structural arrangement and higher applied fire protection to the columns, the results indicate that collapse mechanisms for singe floor and multiple floor fires can be each split into two main groups. For single floor fires (taking place in the upper floors of the frame (Group S1)), collapse is initiated by the pull-in of external columns when heated beams in end bays go into catenary action. For single floor fires occurring on the lower floors(Group S2), failure is initiated (i.e. ultimate strain of the material is exceeded) after the local beam collapse. Failure in both groups for single floor fires is governed by the generation of high loads due to restrained thermal expansion and the loss of material strength. For multiple floor fires with a low number of fire floors (1 to 3) - Group M1, failure is dominated by the loss of material strength and collapse is mainly initiated by the pull-in of external columns. For the cases with a larger number of fire floors (5 to 10) - Group M2, failure is dominated by thermal expansion and collapse is mainly initiated by swaying of the frame to the side of fire origin. The results show that for the investigated frame initiation of collapse mechanisms are affected by the fire type, the number of fire floors, and the location of the fire floor. The findings of this study could be of use to designers of buildings when developing fire protection strategies for steel framed buildings where the potential for a multifloor fire exists.