Ordinary Moment-resisting Frames Research Articles

Seismic resilience: Innovations in structural engineering for earthquake-prone areas

Abstract Objective The contemporary structural engineering notion of "seismic resilience" is to yield a public to its pre-earthquake state in precise time. The goal of our research is the OMRF (Ordinary Moment Resisting Frame), which is mid-rise building that had exposed to several earthquakes. The research examined the constructions mechanical act and seismic confrontation. Methods For hazard evaluations, the building's proneness and functionality were measured using the Seismic Resilience Index (SRI) and delicateness tops. The course had five critical phases: Selecting the goal buildings, picking and ascending a assembly of repetitive seismic ground motion (SGM) archives, emerging brittleness outsides, manufacture incremental dynamic analysis (IDA), and scheming the functionality curve using the seismic resilience index (RI) are the other steps. Findings: It was evident from the hazard evaluation, which included IDA and flimsiness surface examination, that the nominated assemblies required the structural integrity needed to endure a 15-second repeated earthquake. Novelty As the probable seismic ground acceleration raised, it was also probable to figure the variation in functionality, SRI, resilience, structural losses, and the amount of time desirable to mend from numerous presentation stages. These outcomes highpoint the worth of cutting-edge structural engineering methods for educating buildings' seismic resilience in earthquake-prone districts. More resilient configurations that can better endure and recover from seismic shocks can be attained by addressing strategy errors and improving structural presentation.

DESIGN OF REINFORCED CONCRETE STRUCTURE WITH ORDINARY MOMENT FRAME IN LOW SEISMIC REGION (CASE STUDY: MIDRISE SHOPPING BUILDING IN SINGKAWANG CITY)

This paper focuses on the design of a reinforced concrete structure for an eight-story shopping building in Singkawang City, located in a low to moderate seismic area. The study integrates relevant design considerations in response to the region's seismic conditions. Through structural analysis, the building is categorized as seismic design category B due to moderate seismic risk, leading to the selection of an ordinary moment-resisting frame system compliant with SNI 1726:2019. Emphasis is placed on the importance of using such a system to enhance ductility and prevent brittleness during earthquakes.The research emphasizes the need to design structures capable of withstanding various loads, including dead, superimposed dead, live, wind, and earthquake loads, particularly in West Kalimantan, known for its historically low to moderate seismic activity. Recent earthquake records highlight the necessity of earthquake-resistant design for safety and durability. Structural analysis confirms the building's stability against seismic forces, with a modal participation ratio meeting SNI 1726:2019 requirements, indicating robust response under seismic loads.The study also assesses inter-story drift and P-Delta effects to ensure they meet allowable limits, which is crucial for preserving structural integrity and preventing post-earthquake instability. A detailed reinforcement design following SNI 2847:2019 enhances structural strength and durability, especially when under seismic loading. The foundation design uses tailored hollow spun piles to provide sufficient bearing capacity and stability. This approach demonstrates resilience against potential seismic events in low-to-moderate seismic regions, highlighting the importance of integrating seismic design principles and ductility considerations for effective earthquake hazard mitigation.

Shake Table response of a dual system with inline friction damper

The purpose of this paper is to investigate the structural characteristics of a dual system moment frame and concentrically braced frame with a friction damper (CBFD). The experimental test involves the design, detailing, fabrication, and testing of a full-scale dual system frame on a uniaxial shake table subjected to 16 scaled ground motions of various intensities and amplitudes and eight artificially generated sinusoidal, sweep and step functions. The dual system utilized for this testing includes two ordinary moment-resisting frames and a single ordinary concentric braced frame with and without an inline friction damper. Overall, the friction damped braced system decreased the system acceleration by 25 percent at the frame deck. The friction-damped brace increased the damping of the dual system frame by 6.7 percent while maintaining story drift below 1.7 percent. The residual frame story drifts demonstrated that the ordinary moment-resisting frames participated as re-centering frames correcting any residual elongation in the friction damper. Overall, the inline friction damper assembled within the dual system frame demonstrated enhanced structural performance and resiliency.

Design and Comparative Study of Overhead Tank Subjected to Seismic Forces in Different Zones

Overhead tank are generally classified as Ordinary Moment Resisting Frame (OMRF) and Special Moment Resisting Frame (SMRF) supported response reduction factor. Generally, the Overhead tank consists of structural members like slabs, beams, columns, and footings, where the subjected loads are transferred between the structural members and eventually transferred to the Sub-grade of the soil. The behavior of the Overhead tank is different for various sorts of loadings (Dead, Live, Wind, and Seismic) within the analysis and of overhead tank usefully Indian standards codes suggest various loads combinations supported probability of Occurrence. There are around 52 load combinations and IS codes suggest the lateral load (wind and seismic) acts independently but the load governing the planning of structural members is to be acknowledged. and therefore the present study to research the consequences of wind and seismic forces on Overhead tank structures of heights (15m) are considered in seismic zones II, III, IV, V where length and width of the structures are kept constant. An earthquake load is calculated as per IS and wind pressure calculated as per IS 875-1987. The analysis is done the use of STAAD.pro software.

Seismic Performance Assessment of Ordinary Moment Resisting Frame Equipped with Viscous Dampers under Pulse-Like Earthquakes

In conventional structures, the earthquake-resistant design is based on flexibility after yielding of structural members to provide a loss of earthquake input energy, while, using dampers, the input energy loss can be concentrated in predetermined points to prevent the nonlinear behavior of the main members that are also in the gravity bearing path. However, near-fault earthquakes might cause unexpected failure and severe structural damage, especially those with the pulse-like effect. A pulsed movement in the near field records in this system will, however, result in unusual behavior. Technology advances and the creation of vibration control systems have helped control this type of behavior since the earthquake forces are applied indirectly to the structure. For further investigation of this issue, in this study, some traditional two-dimensional frames were modeled for 3, 8, and 12 floors. Seven near-fault pulsed and seven far-fault nonpulsed accelerometers are applied. The structural behavior in four modes is examined: (1) without damper and soil-structure interaction effect, (2) without damper and considering soil-structure interaction effect, (3) with damper and considering soil-structure interaction, and (4) with damper without considering soil-structure interaction. Each model is analyzed in OpenSees software under incremental dynamic analysis. Then, the fragility curve is plotted based on the results. The results indicate that frame (4) reaches the failure level at a higher spectral acceleration, which means that the performance of the viscous damper in reducing drift between floors is one of the main criteria for predicting damages. It also shows the effect of soil-structure interaction on increasing the drift between floors and reaching failure at lower spectral acceleration in all models. Also, by comparing the fragility curves of the models under near-field and far-field records, it is found that the probability of failure under far-field documents (without pulse) is less than that under near-field documents (with a pulse).

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.

Seismic Fragility Curves for Tall Concrete Wall Building in Malaysia Subjected to Near-Field Earthquakes

Tall buildings have been widely constructed in Malaysia, and most of them have been designed only for gravity and wind loads. This study addresses the seismic vulnerability of two tall concrete wall buildings in Malaysia through the framework of seismic fragility curves. The studied buildings shared a similar plan, but the first building had five parking levels while the second building had three parking levels. The structural system of both buildings at the parking levels was an ordinary moment-resisting frame, and at the residential levels was a low-ductile concrete shear wall system. The reference structures were subjected to 15 near-field earthquake records. Fragility curves were obtained by relating the inter-story drift demands to the peak ground accelerations using a reliable statistical model. It was observed that in both buildings, the probability of exceeding minor damage to the exterior frame was larger than that of the interior frame. Besides, a decrease in the number of parking levels increased the probability of collapse. It was also found that only minor damage was expected for tall concrete wall buildings in Kuala Lumpur when subjected to near-field earthquakes.

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)).

Progressive Sidesway Collapse Analysis of Steel Moment-Resisting Frames Under Earthquake Excitations

This paper deals with the assessment of seismic collapse capacities and the related collapse durations of steel moment-resisting frames (MRFs). For this purpose, three prototypes of five-story steel structures are studied. These structures are special, intermediate and ordinary moment-resisting frames with high, medium and low ductility, respectively (SMRF, IMRF and OMRF). The structures have been designed in accordance with the Iranian codes. Furthermore, the deterioration effects of strength and stiffness for structural elements have been considered based on the results of reference experimental models. Next, using 22 pairs of far-field ground motion records proposed by FEMA P695 instruction, incremental dynamic analysis is conducted up to the dynamic instability of structures. Afterward, the collapse capacities of these structures are evaluated and compared with the fragility curves. Also, progressive sidesway collapse durations of the structures are estimated under the selected ground motion records. The results show that SMRF has larger collapse capacity than those of the other frames, and can diminish collapse probability by 33.4% and 54.6% compared to IMRF and OMRF, respectively. Moreover, the results reveal that sidesway collapse duration of SMRF is greater than IMRF and OMRF.

Performance of Moment Resisting RC Frames under Repeated Earthquakes Containing Fling-Step Effect

The ground motion record from near-field earthquake may have forward and backward directivity effects. The first has pulse and fling-step signatures in its velocity and displacement motions, respectively. It is well recognized that the ground motion with pulse and fling-step effects amplified the building drift larger than the ground motion with no pulse and fling-step effects. The building damage also occurs due to earthquakes that are not singly exhibited. This includes the ground motion with fling-step, which is not many studied so far, especially in comparison with ground motion with pulse effect. Therefore, the goals of this study are to find out the effect of repeated earthquakes containing fling-step on the reinforced concrete (RC) moment resisting frames (MRF) in form of interstory drift ratio (IDR) and collapse probability. The 5-, 10-, and 15-story RC frames are taking into account as special, moderate and ordinary MRF, which is based on the R-factor of R = 8, R = 5, and R = 3. Based on the result of incremental dynamic analysis, the cumulative distribution function is statistically developed to define the fragility function. This function is treated as the probability of collapse of RC frames. The result shows that the performance of RC frames induced by single ground motion containing fling-step is at least 2 times larger than the single ground motion with pulse effect. The repeated earthquakes containing fling-step effect propagate the drift of 1.32 and 1.50 times larger than single earthquake with fling-effect. These motions cause the 10- and 15-story RC frames with R = 8 to have 100% of probability of collapse.

Progressive Collapse Potential of Ordinary Moment Resisting R/C Frames

A nonlinear numerical procedure in joint with suitable constitutive concrete and steel models is proposed to simulate the structural behavior and progressive collapse potential of ordinary moment-resisting frames exposed to a middle column removal scenario. Previous experimental results are used to verify the proposed non-linear finite element modelling using ANSYS program. The geometrical discretization of the ANSYS in accordance with concrete and reinforcing steel bars constitutive models have been employed in the suggested approach. The proposed numerical model succeeded in simulating the pre-peak and post-peak behavior in addition to the catenary action stage until reaching the failure of ordinary frames specimens. Numerical predictions are given for the cracking patterns, load-deflection curves, and steel strain-deflection relations.

Collapse Risks of Fail-Safe RC Frames Due to Earthquakes: Fragility Assessments

The objective of this study was to determine the collapse risk of fail-safe reinforced concrete (RC) frames due to earthquakes by newly developed fragility curves. The curves were constructed based on the collapse mechanism, instead of measures of lateral drift as customarily adopted. The procedure was applied to RC open frames that were seismic resistant. A fail-safe mechanism was imposed by allowing plastic hinges to be formed mainly in the beams. This automatically satisfied the stronger column-weaker beam requirement; shear failure was neither tolerated anywhere in the columns nor in the beams. Two kinds of fail-safe RC frames were investigated: special moment resisting frames (SMF) and ordinary moment resisting frames (OMF). Their earthquake collapse risk was computed and compared. Inelastic time history (NLTH) and the non-linear static procedure (NSP) were conducted to assess their structural performance. The results showed among others that the fail-safe OMF had lower collapse risk than the fail-safe SMF. The collapse prevention performance level in NLTH could only be achieved for the fail-safe frames. The non-linear time history analysis should be the only method used for seismic reevaluation/safety checking of building frame structures.

Experimental assessment of the effects of biaxial bending moment and axial force on reinforced concrete corner columns

In this research, corner columns of low‐rise residential buildings, which might be unstable and vulnerable to seismic loadings during earthquake due to vertical and horizontal irregularities, are tested under different effects from bending moment and axial force. Here, biaxial loading is focused and developed, representing a rhombus path with 100% force in the main direction, versus 30% force in the perpendicular direction. Two of eight test specimens are subjected to axial compressive force at 30% of column capacity, while other specimens are at 10%. The eight test specimens were constructed with varying transverse reinforcement details, to control the column‐failure mechanism. The objective of this research was to investigate the seismic behavior of the corner columns of low‐rise buildings that used ordinary‐moment‐resisting‐frames (OMRF). The test results were discussed to interpret the effect of biaxial loading on the overall performance of the columns using comparison between global and local responses. It could be very helpful in deeply understanding the seismic behavior of structures which were designed in accordance with OMRF requirements. Furthermore, this information might affect decisions about using intermediate‐moment‐resisting frames or special‐moment‐resisting frames, where more demanding seismic requirements are applied.

Comparison and Optimization of 8 Storeys Ordinary Moment Resisting Frame and Special Moment Resisting Frame Building

Comparison and Optimization of 8 Storeys Ordinary Moment Resisting Frame and Special Moment Resisting Frame Building

EVALUATION OF FNP FOR RC FRAME WITH BRICK INFILL

The RC multistoryedframe buildings are commonly built with brick masonry as infill walls.Window and entryway openings are unavoidable piece of the infill dividers. The vicinity of openings in infill dividers fundamentally lessens the parallel quality and solidness of RC casings. The fundamental natural period (FNP) of the building with infill panels depend on strength and stiffness of these infill. The strength and stiffness effect of the infill walls are not considered in any of the seismic codes across the world for calculating FNP. An attempt is made in the present paper to evaluate a new empirical formula by method of least squares (MLS), considering the stiffness of the infill walls and number of bays and storeys. The analysis is carried using SAP v14.2 for gravity and seismic loading. Gravity analysis is carried out as per IS 456: 2000 code provisions. Seismic analysis is carried out as per IS 1893 (Part 1): 2002 procedures for multistoryed ordinary moment resisting frame (OMRF) buildings. All the models are constructed in seismic zone IV.The FNP results by MLS are compared with periods obtained from empirical formulae prescribed in seismic codes across the world.The authors conclude that, FNPs obtained by MLS are accurate than the FNPs calculated from the empirical formulae given in seismic codes considered in the paper.

Damage and Seismic Performance Assessment of FRP-Retrofitted Multi-Storey RC Buildings

Structures should be designed for a long in-service life at the lowest cost. Performance based design (PBD) can be used for damage and performance assessment of older FRP-retrofitted multi-storey RC moment resisting frames (MRFs). PBD can be performed using nonlinear pushover analysis according to current codes. In this paper, performance of an existing/older RC frame that has been retrofitted with steel-braced by other researchers is assessed in order to evaluate the ability of the FRP-web bonded system to upgrade the performance level and ductility of RC MRFs. Initially, the flexural stiffness of FRP-retrofitted exterior and interior joints of each level of an existing RC ordinary moment resisting frame (OMRF) is determined using nonlinear finite element (FE) analysis. The stiffness obtained is then used in a mathematical model for pushover analysis of the FRP-retrofitted frame. The plain and the retrofitted frames (both steel-braced and FRP-retrofitted) are analysed using a nonlinear pushover analysis method. The seismic performances of the retrofitted frames are then compared with the plain frame. Finally, the global damage index of the frames at the performance point (and at the life safety (LS)) are determined from the capacity curves and discussed. This evaluation demonstrates that the damage degree of the frame is reduced after retrofitting particularly by FRP. In addition, the FRP-retrofitted frame has a lower damage index at the LS level.

Structural behavior of conventional and buckling restrained braced frames subjected to near-field ground motions

In this study, nonlinear dynamic analyses were performed in order to evaluate and compare the structural response of different type of moment resisting frame buildings equipped with conventional braces (CBs) and buckling restrained braces (BRBs) subjected to near-field ground motions. For this, the case study frames, namely, ordinary moment-resisting frame (OMRF) and special moment-resisting frame (SMRF) having two equal bays of 6 m and a total height of 20 m were utilized. Then, CBs and BRBs were inserted in the bays of the existing frames. As a brace pattern, diagonal type with different configurations were used for the braced frame structures. For the earthquake excitation, artificial pulses equivalent to Northridge and Kobe earthquake records were taken into account. The results in terms of the inter-story drift index, global damage index, base shear, top shear, damage index, and plastification were discussed. The analysis of the results indicated a considerable improvement in the structural performance of the existing frames with the inclusion of conventional and especially buckling-restrained braces.

변성에폭시 모르터로 내진보강한 5층 철근콘크리트 보통모멘트골조의 경제성 분석

변성에폭시 모르터 보강은 철근콘크리트 단면내력 보강방법으로 구조적, 재료적 안정성이 우수하여 단면내력 증대뿐만 아니라 구조물 내진성능도 향상되는 것으로 보고되고 있으나 고가의 재료비로 내진보강 자재로서 실험 및 분석을 한 사례는 거의 전무한 실정이다. 이에 본 연구에서는 철근콘크리트 골조의 내진성능 보강을 위하여 변성에폭시 모르터를 활용하여 보강한 대안 별로 내진성능과 경제성을 분석하여 적절한 내진성능 보강방안을 제시하고자 한다. 이를 위해, 첫째, 본 연구에서는 변성에폭시 모르터로 보강한 부재의 재료 수직응력-변형율관계를 활용하여 단면 휨모멘트-곡률관계를 확인하고 단면의 유연도가 부재에 선형으로 변화한다고 가정하여 실험체 하중-처짐곡선에 대하여 검증한다. 둘째, 수직하중만을 고려하여 철근콘크리트 구조물을 설계하고 보강대안을 제시한다. 셋째, 부재 비탄성 거동을 고려한 구조해석을 실시한 후 보강대안 별 설계계수와 구조물 거동을 파악하여 내진성능을 확인한다. 넷째, 보강대안 별 물량을 산출하여 공사원가를 비교 및 분석한 후 요구되는 내진성능을 만족하면서 경제성이 우수한 보강방안을 제시한다. 본 연구의 결과는 향후 여러 건설현장에서 변성에폭시 모르터 보강공법으로 내진보강을 실시할 경우 기초자료로서 활용될 것이라 기대된다. As a reinforcement material for RC members, the modified epoxy mortar has been reported one of the superior materials since the material can improve the load capacity and the seismic performance of the RC members. However, there were few experimental studies and analytical research for improving seismic performance with the material. This study is to propose an effective reinforcement plan for RC Ordinary Moment Resisting Frame (OMRF) with the evaluation of seismic performance and economic analysis. For the objective, first, the load-deflection curve of a simple beam specimen was compared with the analytical results. Second, a 5-story RC OMRF structure was designed only for gravity load and the alternatives for seismic reinforcement were suggested. Third, pushover analysis was executed for evaluation of design coefficients and seismic performance of the structures. Finally, an effective reinforcement plan was suggested based on the results of quantity take-off and economic analysis. The findings of this study can be utilized as the basic data when the modified epoxy mortar is applied to practice for improving the seismic performance of RC members.

Seismic Behavior of FRP-Retrofitted Reinforced Concrete Frames

Although a significant number of studies have been conducted on the behavior of the reinforced concrete beam-column joints retrofitted with FRP materials, limited investigation considered the overall seismic behavior of the retrofitted frames. In this article, experimental and numerical studies are performed on a scaled-down eight-story and two full scaled low-rise ordinary moment resisting frames (OMRFs) retrofitted with FRP at the joints. Additional, rotational stiffness of the joints is implemented into pushover models to predict seismic performance and behavior factor of the retrofitted frames. Results indicate that FRP retrofitting is more effective than steel braces for low- and medium-rise OMRFs.

Pareto-based optimum seismic design of steel frames

The primary objective of this work is to introduce the idea of using Pareto optimal solutions for the computation of relationships among the factors involved in seismic design of skeletal steel frames. To verify the capability of this concept, multi-objective optimisation is applied and the relations between total skeletal weight, resultant seismic base shear, maximum lateral displacement and the first eigen period of the structure are investigated. Due to the importance of structural safety and for economical reasons, due to its intrinsic conflicting nature, investigation of Pareto optimal solutions for minimisation of skeletal weight against minimisation of maximum lateral displacement of the structure is also considered. For this purpose, a fast non-dominated sorting genetic algorithm is applied to compute Pareto optimal solutions. After computing related Pareto designs, they are used to determine relationships among design factors. The design of an ordinary moment-resisting frame is considered under gravitational dead loads and seismic loads in which lateral earthquake forces are calculated from modal spectral analysis. The structures are under strength and serviceability constraints. All design requirements correspond to the uniform building code and to the allowable stress design code of practice of the American Institute of Steel Construction. The effectiveness of the proposed method is verified using some examples.