Evaluation of Steel Stairwell Dynamic Characteristics, Under Few Mass Configurations Using Ambient Vibration Method

Application of external mass on existing emergency steel stairwell in this study has altered the natural frequency when the resonance threshold has been reached and allows disruption to the human comfort feeling. Ambient vibration testing and modal analysis were carried out on 6 meter height of emergency steel stairway portal frame by using 1 Hz of tri-axial seismometer sensor and open source software of GEOPSY as the processing tool. The stairwell platforms were subjected by cumulative ascending static mass configurations of 300 kg, 600 kg and 900 kg. Identification of the predominant first mode frequency, f1, and mode shapes were made with specified empirical filtering protocols were applied.  Fourier Amplitude Spectra (FAS) was used to transform the ambient vibration time series, when the first predominant frequency under bare frame (BF) condition shows at 8.32 Hz. f1 decreased linearly to 7.35 Hz (BF+300kg), 6.77 Hz (BF+600kg) and 6.23 Hz (BF+900 kg), when the masses were increased. In addition, at these frequencies’ ranges, bad human subjective experiences could be triggered as recommended by previous researchers between 8 to 5 Hz. Besides, the deflection shapes from the first mode frequency was also illustrated at higher deflection amplitude to one of the portal frame’s column which resisting two stairwell platforms. These amplitudes are higher when f1 is decreasing. It can be concluded that, ambient vibration approach has efficiently evaluated the dynamic characteristics and its influence against the structure-person interaction on existing steel stairwell portal frame in this study. Further strengthening work on the steel frame could decrease the reductions percentages of the predominant frequencies, deflection amplitudes and even increase the human comfort level when using the stairwell, especially during building evacuation procedure

Integrated protocol for ground and structures condition assessments using ambient vibration

Safety and serviceability issues on ground or structure normally arise after deterioration or damage appearances. It is worst when there is no regular maintenance program or complete engineering record to carry out the re-evaluation work. Application of ambient vibration (AV) technique is widely used on ground and structures diagnosis works, but none of an effort to integrate them into a specific protocol. The main goal of this thesis is to develop a robust integrated condition assessment protocol on ground and structure using ambient vibration and the main assessment parameter of origin natural frequency. AV testing was performed using a tri-axial seismometer on ground and reinforced concrete (RC) school buildings, with different geotechnical profiles, building configurations and structural health conditions. Determination of peak natural frequency was computed based on the popular methods of Horizontal to Vertical Spectral Ratio (HVSR) and Fourier Amplitude Spectra (FAS) via GEOPSY software. Started by ground condition assessment protocol, the soil classification, soil thickness, and microzonation maps were determined for local soil condition. Meanwhile, in structural condition assessment protocols, the evaluations were made on rocking effect, soil-structure resonance, structural health monitoring (SHM), and building vulnerability. The analysis was initiated by validation of HVSR method on ground, and verification of FAS method on 4-storey of RC buildings. HVSR has proven to be the reliable method. From repetitive AV measurements had indicated consistent prediction with less than 7.0 % disparity of fundamanetal ground frequency (Fo). FAS method showed 0 % of difference at the first mode of predominant building frequency (fo) prediction and 9.5 % at the fifth fo, with the comparison made to prior research. Microzonation map successfully described the sub-surface profile and the resonance zone. Good health of buildings was obtained in repetitive AV measurement within 1.5 years of maximum gap. In rocking effect protocol, the existence of friction piles was clearly identified. Illustrations of mode shapes at respective fo explained the influence of adjacent building, mass and geometric irregularities. A nomograph was introduced for quick evaluation of several components in the integrated protocols at the end analysis. In conclusion, the developed integrated protocol has demonstrated a novel, reliable and robust condition assessment. It will benefit to any ground and comparable RC building even without complete engineering database

Quantitative investigation of physical and mechanical properties of different artificial aggregate

Concrete is an important construction element because it is plastic and soft when newly mixed, yet strong and tough when hardened. However, when the world technologies are develop year by years, lightweight concrete has been commonly used in several structural element applications and its exploitation increases every year on a global basis [1]. Thus, where lightweight concrete is desirable, raising the need for partial or total replacement of the aggregate with a lighter substitute is needed. Lightweight concrete contains artificial aggregate that is natural or synthetic which weighs less than 1100 kg/m3. Due to the low density of Light Weight Aggregate (LWA), it provides better insulation property and can be used to produce light weight concrete. During this period, various types of aggregates have been used

Application of simple plane cap model to simulate compression failure of RC beam under impact loads

The aim of this paper is to present the non-linear analysis for impact response of reinforced concrete (RC) beam with prominence on tension and compression area. In order to envisage the RC behavior, pressure dependant yield criteria Drucker-Prager Plane-Cap (DPPC) type is assumed for the concrete, meanwhile, shear strain energy criterion Von-Mises (VM) is applied for steel reinforcement; to define the accurate strength of material during the short period (dynamic). These material models were incorporated with Adaptive Smoothed Particle Hydrodynamics (ASPH) method. Dynamic Increase Factor (DIF) has been employed for the effect of strain rate (SR) on the compression and tensile strength of the concrete; the orthotropic constitutive equation due to the damage effect is considered during the softening phase on tensile region while constitutive equation of cap model is employed on compression area. A series of experimental studies were also presented in this paper. Several beam elements were tested under low velocity impact loads. Failure mechanism such as shear cracking, bending cracking, compressive behavior of the beam were evaluated by using displacement-time histories as well as overall failure mode. Based on these studies, the investigations enabled a better understanding of the behavior of reinforced concrete beam elements under low velocity impact loads, as well as, it is confirmed that the proposed models give good agreement with experimental results

Dynamic Behavior of Connected Structures

The effect of connected structure on SMK Bukit Tinggi building was investigated based on their dynamic behaviour. The structure was constructed with four main buildings are interconnected. Ambient vibration testing (AVT) was used to predict the dynamic response and characteristics by using triaxial 1Hz seismometer and CityShark data logger. The AVT signals were analysed using GEOPSY software for Fourier Amplitude Spectral (FAS). All predominant frequencies (fo) and mode shapes were identified and verified with previous research finding using similar testing approach on the same building, but with different instrument of accelerometer sensor and ARTeMIS software processing tool. Five modes of fo were found from the FAS curves from this research, but only four fo were obtained from ARTeMIS analysis. The highest deviation percentage was indicated at the 5th mode of building frequency at 9.5 %, but 0 to 2.5% to the rest frequencies mode (1st to 4th frequencies mode). Ununiformed buildings response behaviour was believed to contribute, and initiate active progressive shear cracking on the slab panels, columns, beam and at the reentrant corners between laboratory and academic buildings of Building C. It worst when the buildings were struck by several earthquakes’ series. The unsynchronised oscillation between adjacent buildings to Building C had induced couple lateral and torsional deformations. The structural and non-structural damages mostly concentrated at the reentrant corners and mid-span of the building, which identical to the location of maximum deflection amplitudes. In conclusion, strict attention must be emphasized on the fo and mode shapes based on their dynamic response and characteristics analyses, which could be altered by the presence of connected structures

Dynamic Behavior of Connected Structures

The effect of connected structure on SMK Bukit Tinggi building was investigated based on their dynamic behaviour. The structure was constructed with four main buildings are interconnected. Ambient vibration testing (AVT) was used to predict the dynamic response and characteristics by using triaxial 1Hz seismometer and CityShark data logger. The AVT signals were analysed using GEOPSY software for Fourier Amplitude Spectral (FAS). All predominant frequencies (fo) and mode shapes were identified and verified with previous research finding using similar testing approach on the same building, but with different instrument of accelerometer sensor and ARTeMIS software processing tool. Five modes of fo were found from the FAS curves from this research, but only four fo were obtained from ARTeMIS analysis. The highest deviation percentage was indicated at the 5th mode of building frequency at 9.5 %, but 0 to 2.5% to the rest frequencies mode (1st to 4th frequencies mode). Ununiformed buildings response behaviour was believed to contribute, and initiate active progressive shear cracking on the slab panels, columns, beam and at the reentrant corners between laboratory and academic buildings of Building C. It worst when the buildings were struck by several earthquakes’ series. The unsynchronised oscillation between adjacent buildings to Building C had induced couple lateral and torsional deformations. The structural and non-structural damages mostly concentrated at the reentrant corners and mid-span of the building, which identical to the location of maximum deflection amplitudes. In conclusion, strict attention must be emphasized on the fo and mode shapes based on their dynamic response and characteristics analyses, which could be altered by the presence of connected structures

Effect of Infilled Walls On The Performance of Steel Frame Structures

Today, the subject of a building's resistance to lateral loads is one of the most important concerns of structural engineers. The partitions and infilled walls are non-structural elements that are important due to their effects on the lateral resistance of the building frame. Recently, it has been observed that great damage is occurring to infilled walls, partitions, and buildings in an earthquake-prone area. Infilled walls are effective at increasing the hardness and resistance of building frames, which changes the seismic properties of structures. Therefore, the study of interactions between the structural frame and the infilled walls is essential for a better understanding of structural behaviors. In this paper, the effect of infilled walls is investigated on the behaviour of steel frames using ABAQUS software. Modeling is carried out for different types of infilled materials, including brick and panel, as well as different thicknesses of the infills. It was observed that with an increase in the thickness of infills from 7 to 20 cm, the final capacity and energy absorption increased by 78%. Also, the panel-infilled frames have 18% more capacity and 3.8% more energy absorption than the brick-infilled frame in the same full state. As a result, panel-infilled frames outperform brick-infilled frames in terms of performance.&nbsp

Vibration Criteria Assessment due to Piling Works

In the recent years, the level and nature of the ground vibrations has been more concerned in worldwide. Vibration affected on surrounding building is often associated with the vibration from the ground that is mainly caused by internal and external sources. One of the external sources is construction activities. Identify the effects of vibration caused by piling works in construction sites was the purpose of this paper. It is also aiming to determine the vibration criteria due to piling works in Klang Valley construction site. In addition, the objective of this study is to compare the level of vibration with Department of Environment (DOE) guideline between both Kajang MRT and Klang Valley MRT construction sites. The data used for this study is obtained from past researchers and field testing is performed by using Polytec Laser Doppler Vibrometer and Rion VM-55. The data has been analyzed by using ModalV of MATLAB software. Based on the results, it can be concluded that the vibration amplitude for three distance includes 5m, 10m and 20m are located above the ISO level which stated that the area within the distances not suitable for placement of sensitive equipment.  The highest value of root mean square velocity is occurred in the distance of 5m and the reading is 80000 µm/s. According to Department of Environment (DOE) guidelines, the vibration at distance of 1m and 3m at Kajang MRT will cause major damage to surrounding buildings while minor damage was produced by the vibration at 5m, 10m and 20m distance from bored piling point which located around the area of Klang Valley MRT

Effect of Infilled Walls On The Performance of Steel Frame Structures

Today, the subject of a building's resistance to lateral loads is one of the most important concerns of structural engineers. The partitions and infilled walls are non-structural elements that are important due to their effects on the lateral resistance of the building frame. Recently, it has been observed that great damage is occurring to infilled walls, partitions, and buildings in an earthquake-prone area. Infilled walls are effective at increasing the hardness and resistance of building frames, which changes the seismic properties of structures. Therefore, the study of interactions between the structural frame and the infilled walls is essential for a better understanding of structural behaviors. In this paper, the effect of infilled walls is investigated on the behaviour of steel frames using ABAQUS software. Modeling is carried out for different types of infilled materials, including brick and panel, as well as different thicknesses of the infills. It was observed that with an increase in the thickness of infills from 7 to 20 cm, the final capacity and energy absorption increased by 78%. Also, the panel-infilled frames have 18% more capacity and 3.8% more energy absorption than the brick-infilled frame in the same full state. As a result, panel-infilled frames outperform brick-infilled frames in terms of performance.&nbsp

Damage of reinforced concrete beams consisting modified artificial polyethylene aggregate (MAPEA) under low impact load

The impact damage of reinforced concrete beams subjected to low velocity impact loading at the ultimate load range are explored. In this study, an impact tests is carried out on reinforced concrete beam consisting Modified Artificial Polyethylene Aggregate (MAPEA), where, an approximately 100 kg of impact weight were dropped three times onto the beam specimens until its fails. The waste plastic bags, that encapsulated by glass powder as known as MAPEA were used as the replacement of coarse aggregate. There are twelve beam specimens of size 120 mm x 150 mm x 800 mm are categorized into three groups, where each group consists of 4 specimens. The three groups denoted as normal reinforced concrete (NRC), reinforced concrete with MAPEA concrete block infill (RCAI) and reinforced concrete with 9% of MAPEA as a coarse aggregate (RC9A). All specimens were tested under low velocity impact loads under 0.32 m and 1.54 m (2.5 m/s & 5.5 m/s velocities) drop height of impact weight. The comparisons were made between the three types of beams under the aspect of failure (shear and flexural) and its final displacement. The result of the laboratory test showed that the RC9A beams produced less crack and low value of residual displacement