Moment Resisting Frame System Research Articles

Seismic Performance Assessment of Conventional Construction and Ductile Concrete Moment Frames Using Performance-Based Unified Procedure

A Performance-Based Unified (PBU) procedure has recently been proposed by the National Research Council Canada (NRC) to systematically evaluate seismic design requirements available in the National Building Codes (NBC) of Canada. Conventional Construction reinforced Concrete Moment-resisting Frame (CC-CMF) and Ductile reinforced Concrete Moment-Resisting Frame (D-CMF) systems were used in this paper to first assess the proposed PBU procedure and second determine the adequacy of the basis for seismic design requirements in NBC and see its performance margin against different structural performance levels. Results indicate that the detailed screening in the PBU procedure efficiently reduces the number of Incremental Dynamic Analyses (IDA) by more than 60% for CC-CMF while providing remarkable accuracy. It was also found that the CC-CMF system designed for the Normal importance category can provide an adequate margin against Life Safety (LS) performance level objectives, while the D-CMF system designed for the same importance category passes the Collapse Prevention (CP) performance level criteria.

Comparison of Seismic and Wind Actions on Medium to High-Rise Buildings in Muscat, Oman

This study is a comparison of wind and seismic loads on medium and high-rise buildings in Muscat, Oman. It uses the proposed Omani Seismic Code and Eurocode EN1991 for seismic and wind calculations, respectively. Muscat falls under Zone-1 in the Omani seismic code and experience basic wind speed of 30 m/sec. The research investigates buildings with varying aspect ratios (1:1 and 1:2), heights (11, 15, and 19 stories), and structural layouts (frame only, core shear wall, and corner shear wall), using ETABS for structural analysis. The findings reveal that seismic actions are generally more significant than wind actions for buildings in Muscat. In frame-only structures, wind-induced base shear ranges from 16%-33% for 1:1 aspect ratio and 21%-43% in the x-direction and 10%-20% in the y-direction for 1:2 aspect ratio, when compared to seismic actions. This difference decreases with increasing building height. Incorporating shear walls notably reduces the maximum lateral displacement across all scenarios, with core-located walls being most effective, leading to a 49% reduction in lateral displacement. Shear walls also substantially mitigate first-story column shear forces and bending moments. The study concludes that seismic actions are more critical than wind actions in Muscat for simple moment-resisting frame systems. Additionally, using shear walls in these buildings is highly beneficial for controlling lateral displacements and reducing member forces.

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.

PERENCANAAN STRUKTUR KANTOR PHICOS DENGAN SISTIM RANGKA BAJA PEMIKUL MOMEN KHUSUS

Colomadu is the name of a district in Karanganyar Regency, Central Java. Colomadu's economic growth can grow through the goods and services business, tourism, and industry so that an office building is planned in the Colomadu area. Because the location of Colomadu District is not far from the province of Yogyakarta, where earthquakes often occur, an earthquake-resistant building is needed to anticipate a minimum number of casualties and material losses during an earthquake. Therefore, in planning this office, a special moment resisting frame system (SRPMK) is used. The building with the Special Moment Bearing Frame System (SRPMK) is planned with the concept of Strong Column and Weak Beam (strong column and weak beam). This planning aims to plan a building structure that is resistant to earthquake loads that will be received by the structure using a special moment-bearing frame structure system and refers to the applicable requirements in accordance with SNI 2847: 2019. Earthquake loads are reviewed using the spectrum response method and structural analysis is carried out with the help of the ETABS V9.7.4 program. From the planning results, the dimensions of the bondek floor plate thickness of 140 mm, beams B1A 150x400 mm, B2A 200x400 mm, B2B 200x400 mm, B2C 200x400 mm, B2D 200x400 mm, B2E 200x400 mm, B3A 200x500 mm, B3B 200x500 mm, B4A 300x150 mm, B5A 300x150 mm, BS 150x300 mm, and columns KP 150x150 mm, K1A 200x300 mm, K2A 400x550 mm, K3A 450x650 mm, and K4A 350x500 mm.

PERENCANAAN GEDUNG RAWAT INAP RS MM DUNDA MENGUNAKAN SOFTWARE SAP 2000

This research aims to analyze the structural analysis of a building using software Since computerization is used to complete every building plan or design, the development of technology and information, especially computerization in the world of construction, cannot be separated anymore and is not a new phenomenon. The decision to use a computer to complete construction plans was based on the fact that computers have the advantage of not only being able to finish quickly but also having accuracy, effectiveness, and ease of use (Dwi Deshariyanto, Anita Intan Nura Diana 2021). The following findings have been achieved based on the final results of the development of this final report. using the SAP 2000 version 22 program to calculate reinforcement in columns, beams, and floor slabs, Using earthquake response spectrum design analysis, earthquake load calculations refer to SNI 1726: 2019 (Procedures for Planning Earthquake Resistance for Buildings and Non-Buildings), The design of this building is based on the type of reinforced concrete structure and the Unique Moment Resisting Frame System (SRPMK). The floor difference is in accordance with the relevant SNI criteria

Perbandingan Analisis Struktur Gedung Laboratorium PGSD Universitas Samudra Metode Sistem Rangka Pemikul Momen Khusus Menggunakan ETABS dan BIM Tekla Struktural Designer

Indonesia is located on the fault line of the Eurasian and Indo-Australian plates which makes Indonesia prone to earthquakes. The structural design of the Special Moment Resisting Frame System (SRPMK) is required for reinforced concrete buildings in high earthquake-prone areas, it is hoped that using the SRPMK construction method can have a flexible structure. The purpose of this research is to discuss the comparison of test control of the Samudra University PGSD Laboratory Building with the Etabs application and the Tekla Structural Designer Application. The building structure under review is a reinforced concrete structure with 3 floors with a building length of 54 m, width of 18 m, and height of 16.8 m. The type of soil for the construction site is soft soil with earthquake design category D. Construction planning refers to SNI 1726 – 2019. The additional dead loads of floors and roofs are 0.672 and 0.710, the largest live loads are 7.18 kN/m², the earthquake loads with Ss and S1 are 0.68 and 0.34, the priority factor earthquake of 1.5 and a period of 20 seconds, the suction and compressive wind loads are -0.25 kN/m² and -0.41 kN /m². The results of structural analysis using the ETABS application and the Tekla Structural Designer application, the control values of the mass participation test, the fundamental natural vibration time, the base reaction, and the standard deviation between floors have met the requirements for earthquake-resistant building planning. The volume of concrete is 594.9 m³, the bone requirement for D22 is 3432.96 kg, D19 is 3605 4.89 kg, D16 is 26434.5 kg, D13 is 1774.72 kg, Ø12 is 6237.53 kg, Ø10 is 31599, 07 kg, Ø8 is 4589.31 kg

Analisis Struktur Beton Bertulang Tahan Gempa Untuk Berbagai Variasi Tinggi Bangunan

Indonesia is a country prone to earthquakes because it is located at the confluence of the Pacific and Trans-Asiatic Circum. Padang is included in the 5-6 earthquake area (KDS E & F), which is an area that has the potential for an earthquake accompanied by the possibility of a tsunami., comfortable and safe against the dangers of an earthquake or tsunami. The most influential factor in the planning of high-rise building structures is the strength of the building structure itself, where this factor is closely related to the safety and resilience of the building in holding and accommodating the loads acting on the structure. Instability in the structure is a basic thing that must be avoided and considered for various types of building heights. An unstable structure when subjected to loads causes the structure to experience a greater deformation than a stable structure. One way that can be done to make the structure more stable is to combine the structure with Shear Walls. Shear wall systems can be used to withstand vertical forces such as gravity loads and horizontal/lateral forces such as earthquake and tsunami loads, thereby preventing excessive swaying of the structure. The use of shear walls is also intended so that when an earthquake and tsunami occurs, the lateral forces that affect the structure are not only resisted by the beam and column elements in the structure but are also resisted by the shear wall system. because the placement of the shear walls that are not appropriate causes the shear forces that occur in the columns and beams to be greater. The research object is multi-storey reinforced concrete buildings with variations in height of 5, 7, 10, 15 and 20 floors. Buildings 5, 7 and 10 floors are designed with an open frame system, while buildings with floors 7, 10, 15 and 20 are designed with a double system, namely open portals and shear walls as lateral load resisters. Open portals use a Special Moment Resisting Frame System (SRPMK) design, while shear walls use a Special Structural Wall System (SDSK) design. The calculated structural loads are dead loads, live loads, superimposed dead loads and earthquake loads. Building location in the city of Padang with moderate soil conditions. The strength and stiffness of structures with shear walls are higher than those without shear walls

Changes in SNI-1726 and SNI-2847’S Effects on Low-Rise Reinforced Concrete Buildings’s Reinforcing Steel Weight

The updates of the Indonesian seismic design code (SNI 1726) and the reinforced concrete design code (SNI 2847) have been applied in practice simultaneously. Based on these new codes, seismic loads generally increase, especially for low-rise buildings, and the reinforcement design requirements become much more stringent. Therefore, the construction industry predicts that there will be a significant increase in the need for reinforcing steel. This paper would like to describe the comparison of the design reinforcing steel weight in a 4-story reinforced concrete case study building with a special moment resisting frame system, which is designed using a combination of SNI 1726:2012 and SNI 2847:2013, and which is designed using a combination of SNI 1726:2019 and SNI 2847:2019. This study was found that the increase in reinforcing steel is not proportional to the increase in seismic load and much smaller. This result can then be an illustration of how much increase in design reinforcing steel when using the new codes.

Seismic Study of Precast Steel-Reinforced Concrete Building using Shake Table Test

Precast Steel-Reinforced Concrete (PSRC) structural frame systems for moment-resisting, comprised of Prefabricated Steel (S) girders and Precast Reinforced Cement Concrete (RCC) columns. This structural system has the advantage of inherent stiffness and damping during a seismic event. PSRC’s moment-resisting frame system is also known for its construction efficiency, lightweight, and low cost. Earlier investigations have shown PSRC systems helpful in designing and constructing buildings while maintaining ample strength and high ductility during seismic incidents. Despite much previous research, the use of the PSRC structural system in India is still limited. Previous studies have accepted a vital need to test comprehensive structural systems, both experimentally and analytically - to validate the knowledge collected to date and act as evidence of concept for the PSRC moment-resisting frame system. This paper aims to facilitate more recognition and use of the PSRC structural system as a feasible choice for traditional RCC lateral resisting systems. A shake-table test was conducted to evaluate the PSRC building performance during maximum considered earthquake events. The comparative study of experimental and numerical results of the 1/4th scaled building is presented.

Structure Design Modification of DPW Nasdem Office Building using Steel Special Moment Resisting Frame

Manokwari is a District located at the junction of three main plates forming the earth's crust, namely the pacific plate. This makes Manokwari Regency prone to earthquakes. Therefore, building planning must be designed with the concept of earthquake-resistant buildings. Steel material is one type of material that is often used for planning earthquake-resistant building structures because it has high strength and lightweight properties that it is good for earthquake-resistant buildings. One of the methods often used in the planning of earthquake-resistant steel structures is the special moment resisting frame system (SMRF). This structural system is used because it has full ductility that it can survive in areas with a high earthquake risk. This planning modification was carried out at the DPW NasDem Office building by changing the main structure in the form of reinforced concrete using a steel structure with a special moment resisting frame system (SMRF). Based on the calculation and analysis, the results were obtained, namely: the dimensions of the secondary beam are IWF 300x150x6.5x9, the main beam 1 IWF 350x250x9x14, the main beam 2 IWF 300x200x9x14, the column dimensions KC 450x200x9x14 (floors 1-3), KC 400x200x8x13 (floors 4-5), and KC 350x175x7x11 (elevator columns). Floor slabs are 12 cm thick and 10 cm thick for roofing plates. The SRMF joint design uses a high-quality bolt (A325) with the quality of the BJ41 joint plate and the planning results meet the requirements.

Vertical floor spectra in low- and mid-rise elastic RC moment resisting frame buildings

To examine how floor spectral accelerations affect the design force of flexible Non-Structural Components (NSCs), the present study discusses the estimation of floor response spectra resulting from strong vertical seismic motion. 3-, 6-, 9- and 12-storey reinforced concrete buildings with moderately ductile moment-resisting frame systems, designed in accordance with the National Building Code of Canada [25] were selected for this research. 65 sets of historical records relating to 31 severe earthquakes from across the world were used to analyze the linear behavior of these structures. A constant amplification of the Vertical Floor Spectral Acceleration (FSAV) was observed along the building height. This amplification was noticeably elevated for slab nodes, especially at the center of the interior slab and in shorter buildings. Furthermore, the vertical component of the earthquake had a greater impact at shorter periods, since the maximum vertical acceleration occurred at periods lasting less than 0.35 sec. Finally, equations to estimate FSAV corresponding to the input vertical ground acceleration were proposed for typical code-conforming RC frame buildings.

PERENCANAAN STRUKTUR GEDUNG 3 LANTAI ASRAMA MAHASISWA (RUSUNAWA) PUTRI II UNIVERSITAS PGRI SEMARANG MENGGUNAKAN METODE SRPMM (SISTEM RANGKA PEMIKUL MOMEN MENENGAH)

AbstractThe 3 Floor Student Dormitory Building (Rusunawa) daughter II University of PGRI Semarang was built in the 4th campus area of Universitas PGRI Semarang with a building area of 2119 m2. The building is planned based on the results of the Cone Penetration Test (CPT), it is known that the building is built on soil with soft soil conditions (SE site class). The calculation of the structure uses the SRPMM method (medium moment resisting frame system) which refers to SNI 1726-2019: Earthquake Resistance Planning Procedures for Building and Non-Building Structures. Meanwhile, non-earthquake loading can be adjusted to SNI 1727-2013: Minimum Load for Design of Buildings and Other Structures. The secondary structure is in the form of plates and stairs which are carried by the primary structure, namely beams, columns and shear walls. The lower structure consists of sloof and pile cap, with drill pile foundation. The main ingredient of the structure is reinforced concrete, with reference to SNI 2847- 2019: Requirements for Structural Concrete for Buildings and Explanations. In the requirements of the SRPMM method the structural components that are considered are columns, beams, beam-column relationships and plates. In this case the building structure can respond to earthquakes with seismic design categories (KDS) A, B, and C, without collapsing. The results of the calculation of the primary structure and the substructure of the building are applied in technical drawings consisting of architectural drawings, structural plans, and detailed reinforcement drawings.Keywords: building, medium moment resisting frame system, earthquake load.

Fiber-based model for simulating strength and stiffness deterioration of high-strength steel beams

This paper focuses on the behavior, modeling, and evaluation of high-strength steel beams used as girders in moment resisting frame systems (MRFs). The results of the evaluation have led to the development and calibration of effective (phenomenological) stress–strain curves and fiber-based finite element approaches for modeling the behavior of high-strength steel beams. The key parameters influencing the cyclic behavior of high-strength steel beams are: (i) shape/geometric details, (ii) flange and web slenderness ratios, (iii) material stress–strain behavior, and (iv) fracture/damage failure criteria. This paper summarizes prior experimental results on the cyclic behavior of high-strength steel beams and develops 3D finite element models to simulate their behavior. The models are developed cognizant of the parameters (i)–(iv) listed above. The models are validated against experimental data and then used to conduct parametric studies to evaluate the effects of material and geometric parameters on the cyclic behavior and ductility of high-strength steel beams. The developed effective stress–strain relationships hold the key to developing potential design methods based on allowable strain criteria and/or continuous strength methods recently developed by other researchers.

Proposed seismic design parameters for the moment-resisting knee-braced frame system

This paper proposes and verifies the seismic design parameters, including overstrength-related force modification factor, ductility-related force modification factor, deflection amplification factor, and design period, for the steel Moment-resisting Knee-braced Frame (MKF) system. The building selected in this study is an office located in Vancouver, British Columbia, Canada, in which MKFs act as the lateral load-resisting system. 14 prototype frames spanning a wide range of geometrical configurations are designed following the requirements of the 2015 National Building Code (2015 NBC) of Canada. Nonlinear static analyses are carried out on the prototype frames to determine the preliminary ductility and overstrength factors. Six new MKFs (assessment frames) are designed using the proposed overstrength and ductility factors, and their seismic and collapse performances are examined by comprehensive numerical analyses, considering the effects of the potential sources of ground motion expected on the Canadian west coast, namely subduction intraslab, subduction interface and shallow crustal events. The results of this study suggest that the MKF system shall be designed as a moderately ductile system using overstrength and ductility factors of 1.60 and 3.0, respectively, with a height not exceeding 40 m in regions of high seismicity.

Robustness assessment of RC frame buildings with HPFRCC subjected to progressive collapse

Beam-column joints are one of the most critical components of RC structures, affecting the structure's performance under different types of loads. In recent years, some researchers have considered high-performance fiber-reinforced cementitious composites (HPFRCCs) as an alternative to conventional concrete for improving the performance of beam-column joints. The effects of HPFRCC materials on the robustness of reinforced concrete structures subjected to progressive collapse were investigated in this study. To this end, the method proposed by Fascetti et al. was utilized to assess the robustness of three five-story RC buildings with a moment-resisting frame system. The buildings were designed as special moment frames (SMF), intermediate moment frames (IMF), and intermediate moment frames with HPFRCC at joints (IMF-H) per ACI 318–14. The OpenSees finite element platform has been widely used for 3D buildings simulation and nonlinear analysis. In this study, the analyses and calculated robustness indices indicated that using HPFRCCs materials in beam-column joints significantly improved the robustness of concrete moment frames subject to progressive collapse. Furthermore, the damage distribution based on plastic rotation results confirmed that the robustness of concrete moment frames with HPFRCC joints subjected to progressive collapse was significantly improved.

PLANNING EARTHQUAKE RESISTANT UPPER BUILDING STRUCTURES WITH MOMENT GRABBING FRAME SYSTEM IN THE MARDHIKA PARK APARTMENT BUILDING 20 FLOORS TAMBUN – BEKASI

Indonesia is an area with a high level of vulnerability to earthquake disasters, where this earthquake has caused a lot of losses and damage to building structures. Therefore, to reduce the risk due to the earthquake, it is necessary to plan earthquake-resistant building structures. The structural planning of building construction is needed to get the most effective and efficient dimensions and configuration of the structure. Collapsed buildings that are not strong enough to withstand lateral loads caused by the earthquake have resulted in significant loss of property and even lives. The purpose of writing this thesis is to design an earthquake-resistant Mardhika Park Apartment Building with a moment-resisting frame system (SRPM) which is planned in accordance with SNI 1726:2019 Earthquake (Earthquake Resistance Planning Procedures for Building and Non-Building Structures), SNI 2847 for Reinforced Concrete: 2019 (Requirements for structural concrete for buildings and their explanations), and the loading in accordance with SNI 1727:2020 for (Minimum Loads for Design of Buildings and Other Structures). The structural design of the Mardhika Park Apartment Building includes the design of this superstructure which includes columns, beams, and floor plates. Then the loads that are reviewed for structural element planning are dead, live, and earthquake loads. To assist in calculating the structure is also used Software "SAP2000 " to facilitate the calculation of the structure.

Development of Near-Field Earthquake Loading Protocols for the Steel Moment Connections in Iran

Steel moment frame buildings are widely used in Iran and around the world. The observations from major earthquakes underscored the importance of the beam-to-column connections in seismic force-resisting systems and their influence on such building’s performance. Since the most catastrophic earthquakes that occurred in Iran contained the characteristics of near-field earthquakes, hence understanding the behavior of these connections under such earthquakes is needed. This study proposed loading protocols for special steel moment-resisting frame systems under near-field earthquakes in Iran. Each of them had 23 damage half-cycles with a maximum inter-story drift of 0.065 radians. The proposed loading protocols were compared numerically to each other. The most influential one was chosen as the main loading protocol since it has the most destructive effect on the connection. The main loading protocol showed a faster rate of increase in the plastic strain and imposed the highest amount of dissipated energy at a former loading stage compared to other near-field earthquake loading protocols related to other countries such as SAC and Fang et al.

Fragility curves for existing reinforced concrete buildings, including soil–structure interaction and site amplification effects

SSI and site amplification effects are investigated as influences on the seismic fragility of existing reinforced concrete moment-resisting frame and dual frame-wall system buildings supported on shallow foundations without interconnecting beams. We build upon a holistic methodology that accounts for site amplification and soil–foundation–structure interaction effects using a modular approach. We calculate fragility curves based on nonlinear dynamic analyses for various building structural typologies and geometries, infill conditions, code provisions, and soil profile materials and dynamic characteristics. We demonstrate that site amplification during earthquakes may significantly increase the fragility of the soil–foundation–structure system, which is reflected in its vulnerability. Moreover, SSI is especially prevalent for buildings on soft soil profiles and might modify their fragility. We propose a modular method to include site amplification and/or soil–structure interaction effects in a large-scale earthquake vulnerability assessment using fragility modifiers, which we express using an easy-to-code equation form.

A Comparative Study On The Seismic Performance Of Multi-storey Buildings With Different Structural Systems

The increasing need of shelter in urban cities due to overpopulated spaces and land inadequacy has forced people to limit their needs and spaces. High-rise buildings are the best solution for providing people space for living and to work on, as the buildings are getting higher and slender, they are exposed to different loading condition, which leads the building to experience higher lateral deformations. With the help of different structural systems, the lateral stiffness of the buildings can be improved, there are many structural systems introduced for the high-rise structures which can provide the buildings adequate strength and stability against lateral loading. This paper examines behaviour of Special Moment Resisting Frame System with shear wall, Outrigger Core Belt Truss Structural System and Braced Frame System on a 30 storey building under worst seismic conditions in India i.e. Zone V. To understand effectiveness of the structural systems subjected to lateral loads, three different structural system are modelled using 3D finite element software ETABS 2018, all the models are subjected to the same loading conditions with same geometrical dimension and typical storey height. Comparison is examined on the basis of different parameters like Modal Mass Participation, Base shear, storey shear, Time period, Lateral displacement, storey drift, storey stiffness, and performance points. It was observed by the dynamic analysis method i.e., response spectrum analysis, and non-liner static analysis, the parameters which were compared between three structural system observed that building with outrigger core belt truss system performs better than Special Moment Resisting Frame + Shear Wall and Braced Frame Structural System.

Collapse assessment of low-rise reinforced concrete special moment resisting frame systems using a simplified method

In this study, a simplified method is proposed to generate collapse fragility curves for low-rise reinforced concrete special moment resisting frame (SMRF) systems. Capacity curves are developed without carrying out structural modeling and nonlinear static analysis, to obtain equivalent SDOF parameters. Ground motion spectra that matches the conditional spectrum (CS) at specified seismic intensity levels are statistically generated and a displacement-based assessment procedure instead of nonlinear response history analysis (NLRHA) is adopted, to obtain the peak displacements necessary for the generation of collapse fragility curves, with and without considering uncertainty in modeling parameters. The proposed simplified method is applied to 3- and 5-story low-rise reinforced concrete SMRF systems for the generation of collapse fragility curves. In addition, a 8-story reinforced concrete SMRF system is considered to examine the applicability of the proposed simplified method to non low-rise reinforced concrete SMRF systems. The results show that the collapse fragility curves generated by using the proposed simplified method are in good agreement with the curves developed using NLRHA for the 3- and 5-story low-rise reinforced concrete SMRF systems; however, such agreement is not observed for the 8-story non low-rise reinforced concrete SMRF system.