Ordinary Moment Research Articles

New seismic design method to improve collapse performance of steel ordinary moment frames

Steel ordinary moment frames (OMFs) have been widely used as a seismic force resisting system in low to moderate seismic regions. In this study, the seismic collapse performance of steel OMFs was evaluated. For this purpose, 9-, 12-, 15-, and 18-story steel OMFs were designed in compliance with ASCE 7 (ASCE, 2017) and its reference standards. To improve the collapse performance of the OMFs, a new design method was proposed with a limiting value of column moment strength ratio. Unlike OMFs designed with ASCE 7 and its reference standards, all OMFs designed with the proposed design method satisfied the target collapse probabilities specified in ASCE 7. To investigate the effectiveness of the proposed design method, seismic loss estimation was also performed. The expected annual losses of OMFs were reduced more than 20% when the OMFs were designed with the proposed design method.

Development of new types of bolted joints for cold-formed steel moment frame buildings

It has been a growing trend to use cold-formed steel (CFS) sections as primary structural members in low to multi-story buildings due to their high strength-to-weight ratios, ease of construction and flexibility in manufacturing to a variety of cross-sectional shapes. However, CFS frames are not widely used in seismic regions; one important reason is that the less redundant CFS joints generally have low ductility and energy dissipation capacity due to their inherently thin-walled properties. To address this issue, this paper presents an experimental programme and the corresponding results on two types of beam-to-column CFS joints, which are assembled to the two adjacent surfaces of the built-up CFS column in this paper. Different from the previous research, the two types of joints proposed are potentially suitable to connect CFS members in T-, L- and cruciform joints for multi-story framed-structure buildings. It was observed from the tests that the beams buckled before the occurrence of obvious damage to the tested joints. The two types of joints satisfied the seismic design philosophy of ‘strong connection-weak beam’. Joint Type 2 (JT2) exhibits overall higher performance in terms of strength, ductility, and energy dissipation capacity than the Joint Type 1 (JT1). JT1 satisfies the rotational requirement for Ordinary Moment Frames (OMFs) while JT2 satisfies the rotational requirement for Special Moment Frames (SMFs), as defined in AISC Seismic Provisions. The connection zones within both joints can be classified as semi-rigid according to the approach recommended by Eurocode 3: Part 1–8, with JT1 exhibiting higher stiffness than JT2. Overall, the proposed two joints connected with very slender beams and less bolts, have so far shown moderate performance to provide resistance and ductility to be applied in CFS framed buildings in seismic regions, which can be improved in further work.

Feeling grateful to be optimistic: The influence of recalling special moments on feelings of gratitude and optimism during the COVID-19 pandemic.

In one experiment, we tested the influence of bringing to mind the memory of a special moment versus an ordinary moment from high school on gratitude and the relationship between gratitude and optimism. Participants were first asked to report how the current pandemic has affected their lives. After, participants were randomly assigned to either recalling a special moment from their high school years or recalling an ordinary event from the same life period. Participants then completed a battery of questionnaires assessing gratitude, optimism and some demographics. Results showed a positive influence of bringing to mind the memory of a special moment on gratitude. Gratitude was then positively related to optimism. Hence, the positive relationship between recalling a special event and optimism was mediated by gratitude. Our results showed that brief interventions might help individuals see a brighter future under the current difficult conditions of prolonged lockdowns.

Active-to-sterile neutrino dipole portal and the XENON1T excess

In this paper, we find that a magnetic transition dipole moment between tau and sterile neutrinos can account for the XENON1T excess events. Unlike the ordinary neutrino dipole moment, the introduction of the new sterile mass scale allows for astrophysical bounds to be suppressed. Interestingly, the best-fit regions that are compatible with the SN1987A imply either boron-8 as the source flux. We find that sterile neutrinos in the $\ensuremath{\sim}(500--800)\text{ }\mathrm{keV}$ mass range are capable of evading astrophysical constraints while being able to successfully explain the XENON1T event rate. We also set new constraints on the dipole portal based on the Xenon 1T data. The sterile neutrino in the best fit parameter space may have significant effects on big bang nucleosynthesis (BBN). We show the region in which a low reheating temperature of the Universe may allow the BBN constraints to be alleviated.

Fighting Social Isolation With Nostalgia: Nostalgia as a Resource for Feeling Connected and Appreciated and Instilling Optimism and Vitality During the COVID-19 Pandemic.

In two experiments, we tested the influence of bringing to mind a memory of a special moment versus an ordinary moment on nostalgia and whether this elicited nostalgia was related directly to gratitude and the satisfaction of need for relatedness and indirectly to optimism and vitality. Participants from Mexico were first asked to state how the pandemic of COVID-19 has affected their lives. After, participants were randomly assigned to one of two conditions: Memory of special moment versus memory of ordinary recent moment (study 1) or memory of special moment versus or memory of ordinary moment from the same life period as the special moment (study 2). After, participants completed a battery of questionnaires assessing nostalgia, gratitude and optimism (study 1) or nostalgia, satisfaction of need for relatedness, and vitality (study 2). Results from study 1 showed a positive influence of bringing to mind a special moment on nostalgia. Nostalgia was positively related to gratitude, which was then related positively to optimism. Similarly, results from study 2 showed a positive influence of bringing to mind a special moment on nostalgia. Nostalgia was positively related to satisfaction of need for relatedness, which then had a positive relationship with vitality. In both studies, the indirect sequential effect of bringing to mind a special moment on optimism and vitality was significant.

Extended Rayleigh Distribution: Properties and Application to Failure Data

This paper introduces a new three parameter Rayleigh distribution which generalizes the Rayleigh distribution. The new model is referred to as Extended Rayleigh (ER) distribution. Various mathematical properties of the new model including ordinary and incomplete moment, quantile function, generating function are derived. We propose the method of maximum likelihood for estimating the model parameters. A real life data set is used to compare the flexibility of the new model with other models.

Parametric Study of Dynamic Analysis of High-Rise Buildings with Outrigger Systems

Design of tall buildings have their own challenges, right from resisting lateral loads due to wind and earthquake forces to huge construction costs. In order to reduce the lateral displacement of tall buildings, outriggers are employed. The optimal positioning of these outriggers at various levels of the building results in economic design. Rearranging those optimally positioned outriggers at the same level of the building further reduces the parameters like fundamental time period, drift, lateral displacements, etc. and result in further economic design of the building. Three models each of G+10, G+20, G+30 with ordinary moment resisting frame, special moment resisting frame, special moment resisting frame with outriggers are modeled, analysed and designed as per IS codes using ETABS 2016. Parameters like modal participation mass ratio, storey drifts, maximum lateral displacements against earthquake and wind, minimum base shear, soft storey, maximum to average displacement ratio are checked and brought under control as per Indian codes for lateral stability of the structures. Value engineering is performed on the structures and the final results are compared.

Seismic Evaluation of the RC Moment Frame Structure using the Shake Table

This paper presents the findings of an experimental investigation on a reinforced concrete frame structure (ordinary moment resistant frame). The test model was subjected to lateral excitation employing the 1994 Northridge earthquake accelerogram. The reinforced concrete test model was fabricated in 1:3 reduced scale acquiring dimensional similarities. The utilized ingredient mix ratio was 1:1.65:1.75 and the water to binder ratio was 0.47. The dynamic characteristics (natural frequency and elastic viscous damping) were calculated using the free vibration record. Story shear, drift, and displacement profiles were drawn using multiple excitation records along with damage patterns and capacity curves. The natural frequency of 2.47Hz was calculated for the test specimen, which is equivalent to 1.41Hz for the prototype. Structural damping (elastic viscous) of 12.36% was calculated for the prototype.

Experiential gifts as meaningful moments and memories: Their influence on nostalgia, and relive intention

AbstractWe tested the influence of experiential versus material gifts on nostalgia through their influence on perceptions of meaningful moments and memories and examined one consequence of nostalgia: relive intentions. Participants from Study 1 were randomly assigned to recall and write about an experiential or a material gift they received and completed a measure of nostalgia, perceptions of meaningful moments, and relive intentions. Results showed that meaningful moments mediated the relationship between experiential gifts and nostalgia. Nostalgia was positively related to reliving intentions. Study 2 was an identical replication. Results showed a significant mediation of meaningful moments on the relationship between experiential gifts and nostalgia. Nostalgia was positively related to reliving intentions. We conducted an additional replication with older participants in Study 3. Results showed the same mediation of meaningful moments on the relationship between experiential gifts and nostalgia. In Study 4, participants were randomly assigned to recall and write about a gift that represented a meaningful or an ordinary moment and completed the same measures as Study 2. Results showed a positive influence of recalling a gift that represented a meaningful moment on nostalgia. To our knowledge, this is one of the first studies to examine nostalgia in the gift exchange.

Comparison of progressive collapse resistance capacities of steel ordinary and intermediate moment frames considering different connection details

In this study, the progressive collapse resistance capacities of steel ordinary moment frames (OMFs) and intermediate moment frames (IMFs) with different connection details were numerically evaluated and compared. Three prototype buildings with typical configurations were designed in accordance with Korean building code (KBC). OMFs with welded unreinforced flange-bolted web (WUF-B) connections, OMFs with reduced beam section (RBS) ones, and IMFs with RBS ones were deployed for each building. Beams, columns, connections, and composite slabs were modeled using reduced models of 1-D and 2-D elements for efficient analyses. With respect to progressive collapse analyses, 1- and 2-column removal scenarios were firstly performed through non-linear static analyses and then the numerical results were employed for the energy-based approximate analyses, resulting in load-displacement relationships reflecting dynamic effects due to the sudden column removals without highly time-consuming dynamic analyses. The comparison of progressive collapse resistance capacities was based on the U.S. general services administration (GSA), structural robustness index, and sensitivity index. As a result, all the three buildings met the chord rotation criterion of GSA and indicated enough resistance capacities in the 1-column removal scenario, but not in the 2-column removal scenario. For the OMFs, it was found that the RBS connection showed better resistance capacity than the WUF-B one. Furthermore, the OMFs were superior to the IMFs from the standpoint of resistance capacity. The results can be utilized to predict progressive collapse resistance capacities of similar types of structures.

Impact of the Lead Rubber Base Isolators on Reinforced Concrete Building

Civil engineering infrastructures are prone to natural disasters like earthquakes, floods, and hurricanes. Dissipation energy plays the main role in design of structures under Earthquake loads and controls the behavior of buildings when it bears the lateral loads and transfers them to the foundation. To resist the vibrations in the structure, it is important to use a high technology like Base isolation which reduces base frequency of building vibration and reaching it to a lower value. In other words, seismic isolation has the main objective to protect structure during earthquake events. Base isolation is a flexible layer between foundation and superstructure thus decoupling the structure from damaging effect of ground motion. This edits the dynamic characteristics of the structural system. A comparative study is conducted of seismic performance on three types of thickness (100mm,200mm, 300mm) in which M1T1, M2T1, M3T1, M1T2, M2T2, M3T2, M1T3, M2T3, M3T3, M1T4, M2T4, and M3T4 has been analyzed of isolators namely Lead Rubber Base Isolators (LRBI). For this evaluation, an 8-story structure has been analyzed by using (ETABS) finite element program where Models have ordinary RC moment- resisting frames with square column cross- sections. Parameters like drift, displacement, story acceleration, frequency, and story velocity have been analyzed and it has been found that due to the presence of Lead Rubber Isolators the story drift, story accelerations, base shear, lateral shear forces, and velocity are greatly reduced and story displacement is increased in both X and Y directions compared for various thickness of lead rubber base isolation systems under near and far-field earthquakes. Most importantly it has been established that the transmission of the high energy seismic waves to the superstructure is greatly reduced by introducing base isolators in between the top of the footing and the bottom of the superstructure. The base isolator with thickness 100mm for the concrete grade M20, M30, M40 performed more efficiently than other thicknesses. In conclusion, the deformation and transmissibility ratio must be minimized to introduce as a solution for absorbing the vibrations where the engineer should consider this effect for adequate design.

Progressive collapse of reinforced concrete buildings considering flexure-axial-shear interaction in plastic hinges

Progressive collapse assessment of a reinforced concrete (RC) building designed only for gravity loads and lacking a dedicated lateral load resisting system was carried out using the alternate load path (ALP) method and finite element method (FEM) numerical model created in software SAP2000. Plastic hinge capacity of the members was evaluated considering flexure (M), axial force (N) and shear force (V) interaction and a validated procedure was devised to incorporate the plastic hinge capacity based on M-N-V interaction into the results obtained from the FEM model. It was found that consideration of M-N-V interaction resulted in plastic hinge capacities that were lower than the flexure-only capacity of the plastic hinges available in the FEM software which caused the progressive collapse to initiate at a lower load and also resulted in increased collapse area. In the second part of the study, it was demonstrated that the progressive collapse resistance of the building for the interior and the edge column removal scenarios was appreciably improved after ordinary moment frames were cost-effectively designed at selected locations without increasing member cross-sectional dimensions. However, key element design concept approach was needed for improving the progressive collapse performance for the corner column loss scenarios. Relative reduction in the plastic hinge capacity due to M-N-V interaction as compared to flexure-only hinge capacity was found to be lower for the redesigned building due to improved member capacity.

Semi-rigid behaviour of stainless steel beam-to-column bolted connections

Stainless steel is increasingly used in structural applications but there is still significant lack of experimental evidence on the moment-rotation (M-) behaviour of moment resisting beam-to-column connections. The current paper presents experimental test results obtained from full scale tests conducted on three widely used connection types i.e., double web angle (DWA), top seat angle (TSA) and top seat with double web angle (TS-DWA) connection. Considered beam, column and angle sections were fabricated using austenitic stainless steel plates and M20 high strength bolts were used for connection assembly. M- curves for all connections were carefully recorded and were used to determine initial stiffness (Ki) and moment capacity (M20mrad) for each of the connections. Eurocode 3 guidelines were used to check the classification i.e., whether or not the connections were semi-rigid in nature. Although the considered DWA connection failed to achieve partial-strength, both TSA and TS-DWA connections showed obvious semi-rigid nature despite the connection capacities were limited by bolts. In addition, extensive ductility of stainless steel ensured that all three connection types achieved a minimum connection rotation of 30 mrad, which is specified by FEMA as a requirement for earthquake design of ordinary moment frames.

Evaluating the performance of method to increase the stiffness of structure

The aim of the present research is to increasing the stiffness of the structure against lateral loading. In the present study to increase stiffness of the structure we have four lateral load resisting elements are considered such as shear wall, core wall, bracing system and tube in tube structure and compare all models with bare frame structure. Here an ordinary moment resisting building of G+13 stories located over a medium soil is considered. In the symmetric building the number of bays will be kept as 5 along both direction and the bay size will be kept as 4m with the storey height being 3m. The building will be analysed considering zone V by response spectra method using ETABS 2016 software. The parameters considered as lateral storey displacement, storey drift, storey shear, storey stiffness, base shear and time period.

Comparing the behaviour of multi-storey RCC Structure with different type of bracing system with respect to different seismic zones

Structures located in areas having high seismic activities are exposed to severe damages during earthquakes. Different structures display different deficiencies. For structures exposed to lateral loads such as earthquake loads or wind loads, bracing systems are found to be more efficient. Addition of steel braces results in increase in stiffness which further improves the lateral resistance. Steel bracings provide both practical and economic advantages as they are faster to execute. Steel braces are usually used in between columns and usually provide minimum disruption to the structure. The present study is an effort towards analysis of the structure during the earthquake. An ordinary moment resisting building of G+17 stories located over a soft soil is considered. The structural responses of these frames in terms of Base shear, Storey stiffness, Storey drift, Lateral storey displacement and modal time period are studied through dynamic analysis. The building is analysed considering zone II and zone V by response spectra method using ETABS 2016 software.

Structural performance and sustainability assessment of hybrid-cold formed modular steel frame

Hybrid cold-formed steel (HCFS) structures are new structural systems in the light steel construction industry offering new possibilities, in particular with regard to the applications in mid-rise construction. The structural performance, sustainability as well as the economic and social costs of these structures are of great importance for decision-makers when it comes to deciding on employing these systems and comparing them with their conventional counterparts. In this study, the HCFS systems are evaluated with respect to sustainability, structural performance, economic cost, and social impacts. The results then are compared with those of Ordinary Moment Resisting Frames (OMRF), as the most popular conventional HRS framed system. The methodology consists of both qualitative and quantitative analyses that include the overview of the positive and negative points of each construction method in the form of a comparative study. The results of the structural analysis of the two construction systems show that the hybrid system exhibits better structural performance with regard to the storey shear and drift. It is also shown that in terms of most environmental performance indicators, HCFS framed structures can lead to less environmental impact than OMRF systems. Moreover, the economic assessment demonstrates that HCFS framed structures can save up to the 23% in framing costs, compared to OMRF systems, primarily owing to the fact that lightweight flooring system can be easily incorporated to the design of HCFS structure. Their great potential for prefabrication, on the other hand, makes HCFS a better option with respect to many social compact indicators such as noise, air, vibration and dust pollution and traffic.

Cyclic behavior of RC OMF beam-corner column joints under unidirectional and bidirectional loadings

Reinforced concrete (RC) ordinary moment frames (OMFs) are commonly used for building construction in low-to-moderate seismic regions. Unlike those in special moment frames (SMFs), beam-column joints in RC OMFs are susceptible to damage during earthquakes because the joints are not designed to resist the large shear forces transferred from adjoined members in the elastic range. For this reason, they are more vulnerable when subjected to bidirectional seismic loading. Beam-corner column joints (corner joints) especially are exposed to bidirectional seismic loading. The aim of this study was to explore the cyclic behavior of RC OMF corner joints. Three full-scale corner joint specimens with slabs were built and tested under unidirectional and bidirectional loadings. It was observed that minimal joint transverse reinforcement placed in the OMF joints played an important role on the cyclic performance of the joints, particularly under bidirectional loading. Noticeable difference existed between measured and ASCE 41-17 force-deformation curves, particularly in bidirectionally loaded specimens and in the specimen without joint transverse reinforcement.

Single and combined use of friction-damped and base-isolated systems in ordinary buildings

This study addresses the nonlinear seismic responses of ordinary moment frame building upgraded with a series of passive protective systems. To this, friction damper (FD) as an energy dissipation device and lead rubber bearing (LRB), friction pendulum bearing (FPB), and high damping rubber bearing (HDRB) as base isolators were considered. The effectiveness of the isolation systems together with the dampers was investigated comparatively. For this purpose, eight different cases were taken into account. The first case contains a five storey steel ordinary moment frame considered as fixed-base (FB), the other four cases are the single use of FD, LRB, FPB, and HDRB in such frame, and the last three cases include the upgrading of the frame with the combination of FD with each of the base isolation systems. They are modelled using a finite element program, and evaluated by the nonlinear time history analyses in which seven ground motion records were adopted. The seismic performance of the passive protective systems was evaluated by the engineering demand parameters such as storey displacement, bearing displacement, relative displacement, roof drift ratio, interstorey-drift ratio, absolute acceleration, base shear, base moment, hysteretic curve, and energy dissipation. One of the main outcomes of this study was that single protective system could not always satisfy fully operational performance level, while the combined systems of the base isolation with friction damper effectively achieved for the case study frame. Furthermore, the results showed that the combined systems were capable of limiting the inter-storey drift without increasing the absolute accelerations.

A simplified performance based approach for the evaluation of seismic performances of steel frames

Recent earthquakes have underlined the need for a prompt classification of buildings in terms of seismic performances. The capacity of a structure can be assessed by means of inelastic analysis, requiring sophisticated numerical procedures. Therefore, a simplified method for the evaluation of seismic performance of steel frames to be used in the everyday practice is proposed in this paper. This method can evaluate the capacity of an existing building without resorting to any static non-linear or dynamic non-linear analyses. To set up the method, an extensive parametric analysis was carried out on 420 frames designed according to 3 different approaches: the first is the Theory of Plastic Mechanism Control and ensures the design of structures characterized by global collapse mechanism (Global Moment Resisting Frames (GMRFs)), the second is based on the application of the Eurocode 8 requirements (Special Moment Resisting Frames (SMRFs)) while the third is a non-seismic design, based on sizing for vertical loads only (Ordinary Moment Resisting Frames (OMRFs)).

Behaviour of RC Moment Resisting Regular and Irregular Framed Structures Situated Near and Far to Fault Zone

Near fault earthquake record are rich in high frequencies that effects structures for far fault earthquake record lower frequencies is not effects highly in structure. The objective of the study is to be investigating the effect of near-fault and far fault earthquake motion on the response of RC moment resisting regular and irregular structure considering Near and Far situated fault zones. Linear time history analysis G+10 building has carried out for two structures. The effects of Near and Far faults zones were evaluated for G+10 Two structure the ordinary moment resisting frame system was considered for two building as a lateral load-resisting system. For two building time, history analysis was performed under two example earthquake motion Uattarkashi (Almora and Bhatwari) magnitude 6.8 Mw. The peak acceleration v/s time response spectra of the two horizontal components of the two records for Near source earthquake records @ a distance 21.7 km Bhatwari and Far source earthquake records @ a distance 153.5 km of Almora records are taken in virtual data centre of India earthquake records COSMOS Virtual Data Center - Strong Motion Center. For two building and earthquake record, the analysis was carried out for both conditions and compared with fixed base results for all analysis both Near-field and Far-field earthquake were considered. The mainly evaluated parameter were storey drift, storey displacement and storey force, period vibration results based on linear time history analysis considering two structures. The comparative study of four parameters considers the graphs and curves shows higher and lower values higher values show that the earthquake effect of building and damages is more.