Papers by Keyword: Collapse Mechanism

Abstract: Research on the preservation and restoration of masonry arches is of interest for the scientific and civil engineering communities, and the construction industry. Among the open investigation topics in the field, the study of new materials for strengthening masonry arches has gained attention from researchers. In this context, this paper presents the experimental results from destructive tests carried out on a masonry arch strengthened with steel fiber reinforced mortar (SFRM). The tested masonry arch was made of solid clay bricks disposed in a single layer and was strengthened with a single layer of steel FRM bonded at the arch intrados. In order to replicate the possible condition of an existing arch in which acting loads exceeded the member strength, the arch was preloaded before strengthening. The performance of the strengthened arch is discussed in terms of witnessed failure mode, ductility and increase in the load carrying capacity with respect to unstrengthened condition.

Abstract: Research on the preservation and restoration of masonry arches is of interest for the scientific and civil engineering communities, and the construction industry. Among the open investigation topics in the field, the study of new materials for strengthening masonry arches has gained attention from researchers. In this context, this paper presents the experimental results from destructive tests carried out on a masonry arch strengthened with steel fiber reinforced mortar (SFRM). The tested masonry arch was made of solid clay bricks disposed in a single layer and was strengthened with a single layer of steel FRM bonded at the arch intrados. In order to replicate the possible condition of an existing arch in which acting loads exceeded the member strength, the arch was preloaded before strengthening. The performance of the strengthened arch is discussed in terms of witnessed failure mode, ductility and increase in the load carrying capacity with respect to unstrengthened condition.

Abstract: Steel Plate Shear Walls (SPSWs) have proven to be efficient lateral force-resisting systems. SPSWs utilize the post-yielding strength of the unstiffened web plates, which makes the system economically viable. ANSI/AISC 341-10 suggests the value of response modification factor for SPSWs to be 7, which is based on judgment and qualitative comparisons with response capabilities of previously well-studied systems. This study is focused on the evaluation of the seismic performance factors for SPSW systems through the collapse analysis in accordance with FEMA P695 recommendations. Three-and six-story SPSWs are considered in the study. Aspect ratio of the web plates is varied to obtain the archetypes. Numerical models of the study frames are developed and analyzed using a computer software OpenSees. The modelling technique is validated by comparing the predicted hysteretic response with the past experimental results. Both nonlinear static and dynamic analyses are conducted for the study frames. The results of the collapse analysis are presented and the values of seismic performance factors given in ANSI/AISC 341-10 are verified. Collapse mechanisms of the models for each ground motion are identified and a probability analysis is carried out to identify the most probable mechanisms. Further, suggestions are provided to avoid unnecessary over-strengthening and to ensure adequate collapse margin ratio.

Abstract: In the last few decades, fiber reinforced polymer (FRP) composites have been widely employed in several strengthening and rehabilitation applications of existing masonry buildings. Fiber reinforced cementitious matrix (FRCM) composites are a newly-developed strengthening technique comprised of high strength fibers embedded in a cementitious matrix. FRCMs usually offer several advantages such as the high resistance to fire and high temperatures or vapor permeability with masonry substrate, therefore they appear to be a promising alternative to traditional FRP strengthening systems. In this experimental work, the results of destructive in situ tests performed on existing masonry arches strengthened with FRCM composites are reported. FRCM strips consist of a balanced bi-axial mesh made of basalt fibers embedded in a cementitious grout. Three different configurations of the strengthening system have been considered. Load responses and failure modes are presented.

Abstract: This paper examines the structural behavior of masonry arches strengthened at the intrados with fabric reinforced cementitions matrix (FRCM) composites. Textiles made of poliparafenilenbenzobisoxazole (PBO) and carbon fibers are considered. The experimental results are compared with those obtained on un-strengthened arches and arches strengthened with a carbon fiber reinforced polymer (C-FRP) composite. The tested arches are analyzed with the approach of the limit analysis of the collapse mechanisms.

Abstract: Although a structural analysis of plates based on the linear elastic theory yields good results for deformations and stresses produced by working loads, it fails to assess the real load-carrying capacities of plates on the verge of yielding. In the case of a limit analysis of plates, the yield line theory is widely used on the basis of the upper bound theorem and theoretically it overestimates the strength of plates. That is why the p-version of the finite element method has been proposed for determining the accurate limit load of plates causing collapse. In this method, the hierarchical C^o -plate element for bending of elastic-plastic plates accounting for transverse shear effects has been formulated, and is based on the incremental theory of plasticity and the Reissner-Mindlin plate theory. The numerical results are presented for a variety of rectangular plate problems and are compared to the results obtained by the h-version software ADINA, as well as with the available analytical solutions in literature.

Abstract: Reservoir bank collapse results in vegetation destruction on bank, worsens soil - water loss, impacts local economic and environment. Therefore, attention should be attached to research of reservoir bank collapse mechanism and control measures. The impoundment and operation of China Three Gorges (CTG) reservoir largely changes hydrologic and geologic conditions of the reservoir bank, greatly influences the reservoir bank stability. On the base of summarizing the structure types of main bank and slope in the reservoir area, the typical bank collapse mode and mechanism in CTG reservoir area are analyzed, including erosion degradation type, sloughing type, sliding type and collapsing type. In the light of different material composition, correlative control and harnessing measures are put forward, which can be referred in the control and harnessing of bank collapse in the reservoir area.

Abstract: The present work assesses the state of conservation of the historical Mediceo Aqueduct in Pisa, with classification of architectural elements, decay of materials and failures in view of the restoration. The preview of collapses and the design of interventions in a significant part of the aqueduct are performed. New masonry buttresses for the entire path with optimal distribution are determined to ensure safety and integrity to the monument.

Abstract: Throughout history till today, earthquake prevention and disaster mitigation has been the eternal subject in engineering field. Security is the very premise for the subsistence and development of human beings. Entrusted with government correlation department, the examination of seismic safety and structural health diagnosis will be done in relation to the type, characteristic feature and damage, etc. of current masonry structure in Minnan District, which is in the spirit of “Emphasis on hedge against disaster relief”. According to current criteria as well as considering the actual situation of construction, various constructions will be evaluated scientifically by the on-the-spot survey, investigation, evaluation and analysis, from which get the various morbid state and principle of constructions in concordance with the differences of severity. On the other hand, in line with “rescuing” principle in order of importance and urgency, corresponding classification of disaster prevention and certain applicable and practical disposal ideas will be put forward in order to provide references for engineering practice and application as well as management and policy making for relevant department.

Abstract: The Clemente Bridge is a multi-span masonry arch bridge built during the 18th century on Savio River in Cesena. The aim of this paper is to assess its static capacity under live loads prescribed by Italian Standards in force. The analysis is performed employing RING 3.0, a computational tool based on Limit State Analysis. This method allows to individuate the minimum adequacy factor, that is the multiplier on vehicle loads required to cause collapse. In this way, a first assessment on the bridge safety can be obtained.