Strong Column-weak Beam Research Articles

Evaluation of efficacy of basalt textile fabric on retrofitting of damaged reinforced concrete external beam–column joints

Beam–column joints are crucial elements in reinforced concrete framed structures. These are prone to failure during seismic action and may result in structural collapse. In this context, retrofitting of joint demands a deep attention. This paper presents the results of numerical investigation of retrofitting of an external beam–column joint by externally bonded basalt fabrics using ANSYS along with experimental findings. An external beam–column joint using strong column-weak beam concept was modeled by using appropriate elements available in ANSYS. Three specimens of the joint were experimentally investigated and tested under simulated static loading condition. These were considered as control specimens. Based on the results, the deformations corresponding to a load level equivalent to 60% of average ultimate load were simulated to a new model which was considered as a damaged specimen. By using another suitable element available in ANSYS, the retrofitting using basalt fabric was simulated in the new model in four different configurations and their behavior was analyzed. Two specimens each were experimentally studied. The numerical investigation results show that basalt textile reinforcement enhances the performance of the retrofitted specimens and the results arrived from ANSYS showed good agreement with experimental results.

Seismic behavior of plane frame with special-shaped CFST columns, H-shaped steel beams and vertical rib connections

The seismic behavior of special-shaped concrete-filled steel tubular (CFST) column to H-shaped steel beam plane frame (SCFSTF) with vertical rib connections was investigated experimentally and numerically in this study. Double-bay two-story SCFSTFs with the scale ratio of 1/2 were tested under constant vertical compressive load and cyclic horizontal loads (or displacements), which is a pseudo static experiment considering the axial load ratio. Based on the experimental results, failure modes, bearing capacity, hysteretic curve, skeleton curve, energy dissipation, ductility, rigidity degradation and strength degradation of SCFSTFs were investigated. As a result, a typical strong column-weak beam failure mode was determined. The degradation in strength and rigidity were minimal and energy dissipation capacity and ductility of frames were adequate, demonstrating excellent seismic performance. Besides, energy dissipation capacity and horizontal resistance were improved with axial load ratio increasing within the parametric range of this test. After the test, a finite element method based on software ABAQUS was carried out to further investigate the seismic performance. The numerical results of skeleton curve, rigidity, yield load, peak load and stress distribution agreed well with the test results. The plastic hinge formation process and ultimate failure mode were further investigated using the finite element model.

Impact of the Vertical Component of Earthquake Ground Motion in the Performance Level of Steel Buildings

This study discusses the impact of the vertical component of earthquake ground motion in the performance level of steel building subjected to earthquake excitations. Analyses are carried out for the strong column-weak beam philosophy because the structural performance is focused on these elements. A realistic steel frame is also considered to investigate the impact of including the seismic vertical component in the non-linear response of the building. The main findings of this study are: (1) When an analysis is performed by considering the horizontal and vertical components of ground motion acting simultaneously (near the causative fault), larger plastic rotations in the beams are obtained as compared to those resulting by considering only the horizontal component. (2) Due to the previous finding, if a codified criterion to inspect the steel beams performance in terms of the plastic rotation is considered, the beam performance could lie within a different acceptation criterion (i.e., from immediate occupancy to collapse prevention) if the vertical component is included in the analysis.

Effect of Strong Column Weak Beam Concept on Seismic Capacity of Buildings of Varying Heights: A Review

The strong-column-weak-beam (SCWB) layout philosophy in which plastic deformation is authorized to arise most effective with inside the beams whilst the columns continue to be basically elastic is broadly followed in seismic layout codes for metallic second frames. Under this yield mechanism, the seismic strength is dissipated ordinarily with the aid of using the plastic hinges with inside the beams and on the column bases. The relative plastic flexural capacities of the beams and column bases can drastically have an impact at the response of a SCWB frame. During beyond earthquakes column plastic hinges are extra crucial than beam hinges which offers upward push to worldwide structural harm and excessive existence threatening risk. All the structural components transfers their forces through column and then column shares it with foundation to soil, so u can imagine if column fails whole structure can collapse this is strong beam weak column concept. Keywords: RC frame buildings, Strong-column weak-beam design, Push over analysis.

Assessment of building structure block D of RS BMC Padang

Padang city is the capital of West Sumatra province which is on the west side of the island of Sumatra, is an earthquake-prone area, it is near the confluence of the Asian Euro and Indo-Australia tectonic plates. In the last two decades, there have been two large earthquakes in West Sumatra, on March 6, 2007 (5.8 SR) and September 30, 2009 (7.6 SR). The earthquake on September 30, 2009 has caused severe damage in several areas in West Sumatra such as Padang Pariaman Regency, Padang City, Pesisir Selatan Regency, Pariaman City, Bukittinggi City, Padangpanjang City, Agam Regency, Solok City, and West Pasaman Regency. According to Satkorlak PB data, as many as 1,117 people were killed, the serious injuries reached 1,214 people, light injuries 1,688 people, and the missing 1 person. A total of 135,448 homes were severely damaged, 65,380 houses were moderately damaged, and 78,604 houses were lightly damaged. The earthquake has also caused dozens of multi-story buildings in Padang City to suffer damage, lightly, moderately, and severely damaged and some buildings were collapsed. Block D of RS BMC is one of the buildings of RS BMC Padang, which was built in early 2000. Design of the building structure of Block D of RS BMC used SNI 03-2847-1991 and SNI 03-1726-1989. Nowadays, the newest SNI is SNI 03-2847-2019 for reinforced concrete and SNI 03-1726-2019 for earthquake designs. The paper discusses the assessment of the building structure of block D of RS BMC using the new SNI 03-1726-2019 and SNI 03-2847-2019. The earthquake load used is a dynamic earthquake load using Padang city spectrum response and structural analysis using SAP2000 v.14 software. The analysis results obtained, structural elements of columns, beams, and plates are still able to resist the design loads according to the new SNI. The inter-story drift of floors, the effect of P-delta, the vertical irregularities of buildings, the concept of strong column weak beam, and mass participation are still following the newest SNI.

Study of Strong-Column Weak-Beam Concept on Seismic Capacity of Buildings of Varying Heights

Study of Strong-Column Weak-Beam Concept on Seismic Capacity of Buildings of Varying Heights

Joints behaviour of through steel beam to composite column connection: Experimental study

The objective of this study is to categorize the failure modes; moment and rotation capacities; ductility; stiffness; joint classification; strain behaviour; and load transfer mechanism of steel beam through CFST column connections. Eight one-third scale composite joints were tested under static load up to failure. The key parameters comprise two ηStrength ratios; the effect of beam flange and web continuity inside the connection zone; and full cross-section continuity of steel beam. Moreover, the contribution of the connection component to the overall capacity of composite joints was determined. Results indicated that through beam connection could provide an ideal rigid joint. The absence of beam flange and the discontinuity of full beam cross-section made the connection component highly susceptible to fracture. In contrast, the presence of these details leads to higher ductile behaviour and prevent joint failure. The flange contribution to the moment and rotation capacities is significant, contrarily to the web contribution, which is negligible in value. The flange contribution to ductility coefficient is more dominated compared to web contribution. When strong column-weak beam criteria are followed, the continuity contribution to initial stiffness is more dominated. In contrast, the specimens that follow the weak column-strong beam criterion, the flange contribution to the initial stiffness has the major effect.

Effect of different RC slab widths on the behavior of reinforced concrete column and steel beam-slab subassemblies

In this paper, a total of three reinforced concrete column-steel beam (RCS) subassemblies with different RC slab widths following the strong column-weak beam criterion were tested under the reversed cyclic to investigate the influence of the RC slab on the load transfer mechanism and failure feature of composite connections. With appropriate joint detail, the tested specimens fully developed a desirable beam plastic hinge mechanism with stable and ductile hysteretic response. It was found that the effect of the composite beam-slab sections constrained the core concrete in the connection region was able to obviously improve the seismic performance of composite connections. Additionally, results from this research presented that the RC slabs made a limited contribution to the strength and stiffness of the connections beyond a certain limiting value for the RCS composite moment resisting frame. By analyzing the mechanic mechanism of reinforced concrete column and steel beam-slab connection, it was indicated that effective flange width of the composite beam-slab sections has a significant effect on the capacity of beam moment and equivalent elastic moment of inertia values. Based on the test results, some suggestions are presented for the design of the RCS frame systems, which demonstrates a viable alternative structures in high seismic risk zones.

The Effect of Strong Column-Weak Beam Ratio on the Collapse Behaviour of Reinforced Concrete Moment Frames Subjected to Near-Field Earthquakes

ABSTRACT Buildings are found to be more vulnerable in near-fault regions such that they should be designed with higher strength. In this study, the importance of pulse period and peak ground velocity on the efficiency of the strong column-weak beam ratio (SCWBR) is evaluated through incremental nonlinear dynamic analysis. This work involved two aspects: improving the collapse capacity of structures and mitigation of column damage. Three 4, 8, and 12 story moment frames with varying SCWBR (from 1.2 to 3.0) are subjected to two sets of 44 far-fault and 91 near-fault ground motions. Plastic rotation of elements is utilized as a damage measure for beams and columns. The results demonstrate that idealization of collapse mechanism and early yielding of base columns are controlling factors for the 4 and 12 story buildings, respectively, in particular under long-pulse periods. Moreover, the 8 story (mid-rise) building obtains the highest improvement in the collapse capacity (up to 90%) by the increase of the SCWBR. The most dispersion in the efficiency of the SCWBR among short and large pulse period is observed for the 12 story (high-rise) building. It is also observed that the height-wise distribution of the SCWBR is significantly affected by variation in the pulse period and building height

Experimental and numerical investigation on the seismic behavior of plane frames with special-shaped concrete-filled steel tubular columns

The seismic behavior of (plane) frames with special-shaped concrete-filled steel tubular (CFST) columns (SCFSTFs), H-shaped steel beams, and exterior diaphragm connections was investigated experimentally and numerically in this study. Double-bay two-story SCFSTFs with a scale ratio of 1/2 were tested under constant vertical compressive load and cyclic horizontal loads (or displacements), which is a pseudo-static experiment considering the axial compression ratio. Based on the experimental results, failure modes, bearing capacity, hysteretic curves, skeleton curves, energy dissipation, ductility, rigidity degradation, and strength degradation of SCFSTFs were investigated. As a result, a typical strong column-weak beam failure mode was observed; degradation in strength and rigidity were minimal, and the energy dissipation capacity and ductility of SCFSTFs were adequate, demonstrating excellent seismic performance. Besides, energy dissipation capacity and horizontal load bearing capacity were improved with increasing axial compression ratios within the parametric range of this test. After testing, a finite element method based on ABAQUS was carried out to further investigate the seismic performance of SCFSTFs. The numerical results of skeleton curves, stiffness, yield load, ultimate load, and stress distribution agreed well with the test results. The plastic hinge formation process and failure mode were also further investigated using the finite element method.

Capacity-based seismic design of a middle-rise residential building in an area of moderately-high seismicity

As Indonesia is located across three active tectonic plates, it is prone to a high potential earthquake threat. Strict regulations have been introduced to prevent damage to buildings caused by seismic activity. This study aims to examine the behavior of a middle-rise residential building in a moderately-high seismicity area (i.e. Semarang City) and the design of the Reinforced Concrete (RC) members under seismic load. The design was based on the capacity method and the strong column-weak beam concept was applied to the plastic hinge effect that occurred in the beam. Therefore, the analytical computation was performed, taking the structural seismic response into account. Also, the code-based design calculation of RC members was achieved. The measured structural response showed that the building fulfilled the requirements stated in the Indonesia Code of Earthquake-based Design. The first two modes of the building translated in the Y and X directions, which is the preferred response under the earthquake. The story-drifts that occurred were within the acceptable limits and the structural stiffness in the X and Y directions were found to be similar. Finally, the exact design of RC members was found to satisfy the code.

Lateral resistance of multi-story modular buildings using tenon-connected inter-module connections

In this paper, the lateral performance of multi-story modular buildings is investigated with the effect of a tenon-connected inter-module connection being taken into account. The inter-module connection consists of tenons and through-beam bolts to resist vertical and lateral loads, and the unique configuration allows it to be installed in absence of external access. However, the semi-rigid behaviour of the inter-module connection significantly affects the global performance of the structure. In this study, a simplified joint model is created using Timoshenko beam elements and spring elements within the ABAQUS framework, which substantially reduces the computational costs and makes the system-level analyses practical. Modal analysis and non-linear static (pushover) analysis are conducted on ten modular frames with various design parameters to investigate their performance under lateral loads. Three distinct local and global failure mechanisms are observed. The effects of the strong-column weak-beam configurations, foundation conditions, and axial force levels are discussed in terms of both strength and ductility. The seismic response of the modular frames is assessed using the displacement method, as specified in FEMA-356.

Seismic collapse risk of RC frames with irregular distributed masonry infills

Masonry infills are normally considered as non-structural elements in design practice, therefore, the interaction between the bounding frame and the strength contribution of masonry infills is commonly ignored in the seismic analysis work of the RC frames. However, a number of typical RC frames with irregular distributed masonry infills have suffered from undesirable weak-story failure in major earthquakes, which indicates that ignoring the influence of masonry infills may cause great seismic collapse risk of RC frames. This paper presented the investigation on the risk of seismic collapse of RC frames with irregularly distributed masonry infills through a large number of nonlinear time history analyses (NTHAs). Based on the results of NTHAs, seismic fragility curves were developed for RC frames with various distribution patterns of masonry infills. It was found that the existence of masonry infills generally reduces the collapse risk of the RC frames under both frequent happened and very strong earthquakes, however, the severe irregular distribution of masonry infills, such as open ground story scenario, results in great risk of forming a weak story failure. The strong-column weak-beam (SCWB) ratio has been widely adopted in major seismic design codes to control the potential of weak story failures, where a SCWB ratio value about 1.2 is generally accepted as the lower limit. In this study, the effect of SCWB ratio on inter-story drift distribution was also parametrically investigated. It showed that improving the SCWB ratio of the RC frames with irregularly distributed masonry infills can reduce inter-story drift concentration index under earthquakes, therefore, prevent weak story failures. To achieve the same drift concentration index limit of the bare RC frame with SCWB ratio of about 1.2, which is specified in ACI318-14, the SCWB ratio of masonry-infilled RC frames should be no less than 1.5. For the open ground story scenario, this value can be as high as 1.8.

Comparison on yield mechanism of strong column-weak beam of reinforced concrete frame structure

Ductility is an important aspect of the seismic performance of structures. Strong column and weak beam are important means to ensure the hinge plastic failure mechanism of frame structures. The corresponding provisions on failure mechanism of strong column-weak beam has been specified in design codes of various countries, but their differences are relatively large. This paper takes a plane frame as example which is designed according to the seismic code regulations of various countries, and then the difference in the failure mechanism of the designed frame under seismic actions is compared and analyzed. Finally, some suggestions are given to ensure the realization of strong column-weak beam mechanism.

Pseudo-dynamic test investigation of recycled concrete-encased steel frame

This paper primarily focused on the seismic capacity of recycled concrete-encased steel (RCES) frame structure. A two-span three-storied RCES frame which is at 1:2.5 scale was conducted to investigate the acceleration time-history curves, acceleration amplification factors, peak restoring force and displacement, energy dissipation capacity, displacement time-history curves, bearing capacity, stiffness degradation and seismic performance evaluation during experiment. Based on the date analyzed compared with other structures, the hysteretic energy dissipation of RCES structure is better than the common reinforced concrete frame but similar to steel reinforced concrete. The pseudo-dynamic analysis method was adopted in this test. Taft, El Centro and Lanzhou synthesized wave were chosen as the input excitations. It is found that RCES structures show good seismic performance during the test. The beam is yield earlier than column, and the strain of node core area is small. The results indicate that the design of RCES frame meets the requirement of “strong column weak beam” and “strong node and strong anchorage”.

Lateral load resisting behavior of steel moment frames with reduced web section (RWS) beams

Many studies have been conducted on the monotonic and cyclic behavior of beams with Reduced Web Section (RWS) moment connections. However, the use of these structural elements in Steel Moment Resisting Frames (SMRF) have not been much considered. This paper presents a numerical investigation on the lateral load carrying behavior of steel moment resisting frames with reduced web beam sections. For this purpose six multi-story multi-bay structures with different seismic design category, framing type and geometric configurations are designed and modeled numerically. A design procedure for calculating the proper size of opening in the beam web is presented. Then, nonlinear static analysis is conducted on the frames with reduced web beam sections and results are compared with the ones corresponding to the conventional moment resisting frames. Based on the results, the average reduction in initial stiffness and ultimate base shear of the models with perforated beams are 2.5–8.5% and 3.5–6%, respectively. This is while the investigation of yielded areas in these models showed that the plastic zone moved from beam-column connection zones to the openings which is consistent with “Strong column-weak beam” rule. Therefore, the proposed design algorithm can be considered as an effective way to select the proper perforation size which decreases demand for plastic deformation at beam-column connections without causing further decrease in stiffness and strength of the frame.

Seismic Behavior of Extended End-Plate Connections Subjected to Cyclic Loading on the Top-Side of the Column.

The extended end-plate connections provide excellent performance in resisting seismic loads in high-risk areas. Most scholars’ experiments and finite element studies on this type of joint are focused on the method of applying displacement loads on the beam tip, while the method of applying displacement on the column side has not been the subject of further study. However, the load transmission mechanism of this type of connection is not completely consistent in actual engineering, as the design concept of “strong column weak beam” does not apply to all joints. Therefore, in this paper, the lateral displacement of the applied column is used to simulate the seismic horizontal force to study the mechanical properties of the connection joints of the “weak column and strong beam” under the limit state of earthquake action. Based on the two internal columns (IC-EP1/2) and two edge columns (EC-EP1/2), the failure modes, strength, stiffness, moment–rotation curve, skeleton curve, ductility, and energy dissipation of this type of connection were studied. Experiment results indicated that this type of connection features semi-rigid and partial strength joints. The connection rotation angle of all specimens in the test exceeds 0.05 rad, which suggests it is an ideal seismic joints. Besides, the relationship between the thickness of the end-plate and the diameter of the bolt has a greater impact on the failure mode of the joint. The finite element (FE) analysis models were established for the above connection. The numerical model was validated against experimental results and showed acceptable consistency.

STUDI PERENCANAN STRUKTUR GEDUNG REKTORAT MENGGUNAKAN SISTEM RANGKA PEMIKUL MOMEN KHUSUS (STUDI KASUS UNHASY TEBUIRENG JOMBANG)

The record building is located on the location of the B campus of the Hasyim Asy'ari University Tebuireng - Jombang which functions as an academic and administrative center for all faculties. The planned improvement of the new rectorate building consists of 7 floors with a height of 32.40 m and a building area of 574 m2. The main purpose of the research is to produce a picture of the structure of the new rector's building. The new rector's building structure planning uses a single system in the form of a special moment bearing frame system (SRPMK) and modeling uses an application program to calculate the moment and reaction of the components of floor plates, stairs, beams, columns, sloof and poerplat with earthquake load design using the equivalent static method. The regulations used for planning use SNI 1726-2012, SNI 2847-2013, SNI 1727-2013 and PPIUG-1983. The results of analysis and design in the new rectorate building produce primary structural components in the form of beams B1 = 450 x 600, B3 = 350 x 500 and columns K1 = 700 x 700, K2 = 600 x 600 that have met the cross section requirements for special moment bearing frame systems and the mechanism of the Strong Column Weak Beam. Secondary structural components in the form of plates with thickness = 13 cm. Lower structure components are SLO SL = 400 x 800 and template P1 = 2100 x 2100 x 650 and 35 cm minile at a depth of 14 meters.

Experimental study of a three-storey concrete frame structure with smooth bars under cyclic lateral loading

Past lateral cyclic or seismic tests of concrete frames with smooth bars in columns are very few and limited as far as the test structure’s size and geometry are concerned; moreover, they have not focused on the effect of detailing and lap-splicing of such bars on local and global behaviour. To help fill this knowledge gap with new data, the paper presents the cyclic lateral load test of a 2:3-scale three-storey, one-by-two-bay, strong beam-weak column RC frame, focusing on the effects of the column’s smooth bars and of their detailing on local and global behaviour. Slippage of bars caused concentration of column deformations in flexural cracks at the top and base sections and gave to the global hysteresis loops a shape typical of bond-slip behaviour, but without cyclic strength decay. Despite chord rotation demands of up to 0.055 rads and storey drifts of almost 5%, damage was limited and had nothing to do with the use of smooth bars in the columns. Despite the important role of bar slippage for the response, bar strains show that wherever the surrounding concrete was in compression, column bars were in compression as well. Lap splices at and/or FRP wrapping of column end regions did not have systematic effects on column behaviour. Overall, no adverse effect of the use of smooth bars was identified.

Cyclic Loading Test for Concrete-Filled U-Shaped Steel Beam to Concrete-Filled Steel Tube Column Connections

Concrete-filled U-shaped steel (CFUS) beam and concrete-filled steel tube (CFST) column are recently developed because of the quick construction and economical saving. This paper aims to investigate the seismic performance of a composite connection system connecting CFUS beam to square CFST columns. In the joint system, the grooved cuts on the square tube allowed the U-shaped steel beam passing through the joint core completely, which developed a through beam connection. To verify the seismic behavior of the beam-column connection, three specimens designed according to the strong column-weak beam and strong joint-weak member seismic concept were tested under combined constant axial compression and cyclic loading. For the test parameters, the different connection details and the axial load on the CFST column were considered. The test results showed that the specimens exhibited good load-carrying, deformation, and energy dissipation capacities. The maximum story drift ratio of all the three specimens was 5%, satisfying the minimum requirement of special moment frames. The primary failure mode of the specimens was local buckling of the webs and the fracture of the bottom flanges of the CFUS beam near the column tube. In addition, the joint shear strength of the specimens was evaluated based on ASCE design guidelines.