Nor Azizi Yusoff

Analysis of the effect of vibration from footfalls on office building

Human footfalls are the main source of vibration in office building and it could affect the structure of the building as well as causing discomfort and annoyance to the occupants of the building when the vibration level inside the building exceeds the recommended level. The objectives of the study are to determine the level of vibration on each floor of a multi-storey building due to footfalls and to perform structural response on the multi-storey building due to footfalls input. The selected building for this study is Registrar Office building located in Universiti Tun Hussein Onn Malaysia (UTHM). The scope of study is focused on the effect of vibration induced by footfalls on multi-storey building and analyzing the data using MATLAB and ANSYSv14. The real inputs of vibration induced by footfalls were measured and obtained using Laser Doppler Vibrometer (LDV). The vibration level induced by footfalls on the multi-storey office building can be determined using Vibration Criteria (VC) guidelines. Finally, from the study, the vibration level achieved for this Registrar Office building is in ISO level range which is still under the acceptable limit for office building.

The Study of Soil-Roots Strength Performance of Soil Slope by Using Guinea Grass

Vegetation has been proven for establishing and implementing resistive measures against erosion and failure of slopes, river banks, removal of air pollution and reduced storm water runoff. Installation of cover crop involved soil element usage as growth medium which create several interaction between both strands. This study was carried out to investigate the soil strength performance by using Guinea grass at different construction period up to three months. Grass was planted in a 300 mm x 300 mm x 700 mm test plot with a suitable soil medium. Direct shear tests were conducted for each plot to determine the soil shear strength according to different construction period. Some basic geotechnical testing also were carried out. The results showed there is an increment in shear strength for soil sample over the time at various depths. During period of 1st, 2nd and 3rd month, the average shear stress of 100 mm depth was 50.56 kPa, 63.96 kPa, and 96.59 kPa respectively. Meanwhile, for 200 mm depth the result was 40.843 kPa, 53.91 kPa and 62.93 kPa respectively. Lastly, on 300 mm depth, shear stress was 37.21 kPa, 51.09 kPa, and 59.27 kPa respectively. Based on the result, the higher shear strength was obtained at different construction period and at varying depths. From the observation, roots mass increased for different construction period. In terms of tensile strength, the diameter of the root affects the rate of resistance against the tensile forces. This indicated that the roots structure growth affects the soil shear strength.

Simulation of Sub-Drains Performance Using Visual MODFLOW for Slope Water Seepage Problem

Numerical simulation technique was used for investigating water seepage problem at the Botanic Park Kuala Lumpur. A proposed sub-drains installation in problematic site location was simulated using Modular Three-Dimensional Finite Difference Groundwater Flow (MODFLOW) software. The results of simulation heads during transient condition showed that heads in between 43 m (water seepage occurred at level 2) until 45 m (water seepage occurred at level 4) which heads measurement are referred to mean sea level. However, elevations measurements for level 2 showed the values between 41 to 42 m from mean sea level and elevations for level 4 between 42 to 45 m from mean sea level. These results indicated an increase in heads for level 2 and level 4 between 1 to 2 m when compared to elevations slope at the level 2 and level 4. The head increases surpass the elevation level of the slope area that causing water seepage at level 2 and level 4. In order to overcome this problems, the heads level need to be decrease to 1 until 2 m by using two options of sub-drain dimension size. Sub-drain with the dimension of 0.0750 m (diameter), 0.10 m (length) and using 4.90 m spacing was the best method to use as it was able to decrease the heads to the required levels of 1 to 2 m.

Soil-roots Strength Performance of Extensive Green Roof by Using Axonopus Compressus

Green roof technology has been proven to provide potential environmental benefits including improved building thermal performance, removal of air pollution and reduced storm water runoff. Installation of green roof also involved soil element usage as a plant growth medium which creates several interactions between both strands. This study was carried out to investigate the soil-roots strength performance of green roof at different construction period up to 4 months. Axonopus compressus (pearl grass) was planted in a ExE test plot with a designated suitable soil medium. Direct shear test was conducted for each plot to determine the soil shear strength according to different construction period. In addition, some basic geotechnical testing also been carried out. The results showed that the shear strength of soil sample increased over different construction period of 1st, 2nd, 3rd and 4th month with average result 3.81 kPa, 5.55 kPa, 6.05 kPa and 6.48 kPa respectively. Shear strength of rooted soil samples was higher than the soil samples without roots (control sample). In conclusion, increment of soil-roots shear strength was due to root growth over the time. The soil-roots shear strength development of Axonopus compressus can be expressed in a linear equation as: y = 0.851x + 3.345, where y = shear stress and x = time.

Preliminary Overview on Thermal Performance of Green Roof

Green roof has shown potential contribution on improving the functional performance of buildings by lowering the roof exterior surface temperature, which is indirectly, could potentially reduce the energy demand. In addition, it is likely to provide important ecological services to urban areas through lowering of urban heat island (UHI) temperatures, increasing storm water retention and improves the biodiversity. This paper will then present the initial outcomes of the joint initiative between Malaysia Agricultural Research and Development (MARDI) and Universiti Tun Hussein Onn Malaysia (UTHM) in promoting this green technology in Malaysia. As green roof technology is still emerging, there is limited technical data available at present in Malaysian climate. The study aims to provide initial observation on the thermal performance of green roof and its effect towards surrounding and associated significant environmental benefit. In order to achieve the goal, the thermal performance of green roof system in experimental plot at MARDI had been monitored. The green roof experimental plot has been set up on two flat roofs in Horticulture Research Centre, MARDI, Serdang, Selangor and the treatments consists of two green roof system known as conventional system and self-watering system. The substrate depths were 50 mm and 100 mm. In addition, some observation on the attracted wildlife to the green roof was initiated. Based on the initial results, it is interesting to report that the temperature reduction for the green roofs on Roof 1 and Roof 2 were in averages of 6.1°C and 10°C, respectively. In conclusion, this joint study between UTHM and MARDI may facilitate the development of roof top gardening system in greening the urban area. With more studies, it will possibly highlight the engineering significance, furthermore promoting the application of green roof technology in Malaysia.

Ground Vibration Attenuation Measurement using Triaxial and Single Axis Accelerometers

Peak Particle Velocity is one of the important term to show the level of the vibration amplitude especially traveling wave by distance. Vibration measurement using triaxial accelerometer is needed to obtain accurate value of PPV however limited by the size and the available channel of the data acquisition module for detailed measurement. In this paper, an attempt to estimate accurate PPV has been made by using only a triaxial accelerometer together with multiple single axis accelerometer for the ground vibration measurement. A field test was conducted on soft ground using nine single axis accelerometers and a triaxial accelerometer installed at nine receiver location R1 to R9. Based from the obtained result, the method shows convincing similarity between actual PPV with the calculated PPV with error ratio 0.97. With the design method, vibration measurement equipment size can be reduced with fewer channel required.

Dynamic Analysis of an Office Building due to Vibration from Road Construction Activities

Construction activities are widely known as one of the predominant sources of man-made vibrations that able to create nuisance towards any adjacent building, and this includes the road construction operations. Few studies conclude the construction-induced vibration may be harmful directly and indirectly towards the neighbouring building. This lead to the awareness of study the building vibration response of concrete masonry load bearing system and its vibrational performance towards the road construction activities. This study will simulate multi-storey office building of Sekolah Menengah Kebangsaan (SMK) Bandar Enstek at Negeri Sembilan by using finite element vibration analyses. The excitation of transient loads from ground borne vibrations which triggered by the road construction activities are modelled into the building. The vibration response was recorded during in-situ ambient vibration test by using Laser Doppler Vibrometer (LDV), which specifically performed on four different locations. The finite element simulation process was developed in the commercial FEA software ABAQUS. Then, the experimental data was processed and evaluated in MATLAB ModalV to assess the vibration criteria of the floor in building. As a result, the vibration level of floor in building is fall under VC-E curve which was under the maximum permissible level for office building (VC-ISO). The vibration level on floor is acceptable within the limit that have been referred.

Vibration Analysis of Beam and Block Precast Slab System due to Human Vibrations

Beam and block precast slabs system are very efficient which generally give maximum structural performance where their voids based on the design of the unit soffit block allow a significant reduction of the whole slab self-weight. Initially for some combinations of components or the joint connection of the structural slab, this structural system may be susceptible to excessive vibrations that could effects the performance and also serviceability. Dynamic forces are excited from people walking and jumping which produced vibrations to the slab system in the buildings. Few studies concluded that human induced vibration on precast slabs system may be harmful to structural performance and mitigate the human comfort level. This study will investigate the vibration analysis of beam and block precast slab by using finite element method at the school building. Human activities which are excited from jumping and walking will induce the vibrations signal to the building. Laser Doppler Vibrometer (LDV) was used to measure the dynamic responses of slab towards the vibration sources. Five different points were assigned specifically where each of location will determine the behaviour of the entire slabs. The finite element analyses were developed in ABAQUS software and the data was further processed in MATLAB ModalV to assess the vibration criteria. The results indicated that the beam and block precast systems adequate enough to the vibration serviceability and human comfort criteria. The overall vibration level obtained was fell under VC-E curve which it is generally under the maximum permissible level of vibrations.

The Potential of Recycled Locally-Sourced Waste Materials for Green Roof Soil Mixtures

The increase in surface runoff has become a serious environmental problem and concern in Malaysia. Hence, promoting the use of green roofs in urban areas will potentially allow some storage area and time attenuation for any rainfall. Initial studies on a few substrate mixtures were done in order to find out the properties of green roof media. These included vermiculite (V), perlite (P) and peat moss (PM) together with locally-sourced waste materials such as empty fruit bunches (EFB) and wet diaper gel (D) which are expected to potentially retain more storm water runoff. A test on the substrate mixture properties and evaporation tests were conducted on seven types of soil mixtures. The results show that a basic substrate mixture of PVPM3,5,2 has a maximum water capacity of 50%. The modification and addition of diaper gel in DVPM1,3,2 and empty fruit bunch (EFB) in PEFBPM1,0.3,2 show an increment in both mixtures’ water holding capacity (54%). All the proposed mixtures have shown permeability values larger than 0.0005 cm/s. To investigate the maximum water storage availability, the evaporation tests show that both mixtures could provide 60 - 62 mm of water storage after 34 days without rainfall under ambient climatic condition (32 ̊ to 34 ̊) whereas under extreme heat temperatures (50 ̊), both mixtures took only 1 day to provide the same storage as the ambient condition. Therefore, this study has provided an initial understanding of the properties of the substrate mixture as well as the evaporation rate of the materials tested. This information can be used to demonstrate the relationship between soil characteristics and local climatic factors (temperature).

Vibration Response of Multi Storey Building Using Finite Element Modelling

Interaction between building, type of foundation and the geotechnical parameter of ground may trigger a significant effect on the building. In general, stiffer foundations resulted in higher natural frequencies of the building-soil system and higher input frequencies are often associated with other ground. Usually, vibrations transmitted to the buildings by ground borne are often noticeable and can be felt. It might affect the building and become worse if the vibration level is not controlled. UTHM building is prone to the ground borne vibration due to closed distance from the main road, and the construction activities adjacent to the buildings. This paper investigates the natural frequency and vibration mode of multi storey office building with the presence of foundation system and comparison between both systems. Finite element modelling (FEM) package software of LUSAS is used to perform the vibration analysis of the building. The building is modelled based on the original plan with the foundation system on the structure model. The FEM results indicated that the structure which modelled with rigid base have high natural frequency compare to the structure with foundation system. These maybe due to soil structure interaction and also the damping of the system which related to the amount of energy dissipated through the foundation soil. Thus, this paper suggested that modelling with soil is necessary to demonstrate the soil influence towards vibration response to the structure.