Shock and Vibration

Volume 2017 (2017), Article ID 9567657, 12 pages

https://doi.org/10.1155/2017/9567657

## Development of Absorbed Blasting Vibration Energy Index for the Evaluation of Human Comfort in Multistorey Buildings

^{1}State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan 610065, China^{2}College of Water Resource and Hydropower, Sichuan University, Chengdu, Sichuan 610065, China

Correspondence should be addressed to Hongtao Li

Received 9 February 2017; Accepted 3 May 2017; Published 31 May 2017

Academic Editor: Isabelle Sochet

Copyright © 2017 Qiang Yao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

There have been civil disputes and complaints regarding the negative effects of blasting vibration on buildings around the blasting site. By considering the effect of blasting vibration on a human body as a process of energy transfer and conversion, the human body absorbed blasting vibration energy (ABVE) index has been developed for comfort evaluation. Using dynamic monitoring and theoretical analysis, the elevation amplification effect and selective amplification effect on different frequency components of the ABVE have been investigated. The elevation amplification factor and selective amplification coefficients on different frequency components of the ABVE index for a typical 4-storey brick and concrete building have been determined. Based on the results, the magnitude and frequency components of the ABVE index in different parts especially in different storeys for the typical building have been determined. According to the characteristics of human body’s response to vibrations of different frequencies, the frequency-based weighting method of ABVE index has been simplified. By calculating the combined effect of vibrations from all directions, the total human body ABVE and its frequency components at different floors of the building can be determined accurately. This can be used to evaluate the human body comfort against blasting vibration at different floors.

#### 1. Introduction

In recent years, with more projects in hydropower, railway, highway, and urban construction, there is more blasting near residences and businesses. As such, the number of civil disputes, complaints and lawsuits induced by the blasting has been increasing [1, 2]. Many studies have shown that human body is sensitive to the blasting vibrations. The sensitivity of human body is more than 10 times greater than that of buildings [3, 4]. At present, when blasting operations are conducted near residential areas, attention tends to be paid only to the impact of blasting vibrations on the safety of buildings [5, 6]. The vibration strength which meets the vibration comfort requirement is less than the safety limit for cosmetic cradling. Hence, the complaints and disputes cannot be solved from the perspective of structural safety [7]. Rather than safety, the problem is a typical issue of comfort that needs to resolve the annoyance, anxiety, and even complaints of residents, which are mainly caused by annoyance effects of blasting activities, fear of building damage, and disturbance effects [7, 8]. In recent years, blasting vibration comfort has become a research topic in United States, Canada, United Kingdom, Australia, and India [9–13]. The problem, as many researchers put it, has transferred from limiting structural damage to reducing lawsuits. The sensitivity of people to vibration is an important area and a new research topic in studying blasting vibration [14, 15].

There are many factors that affect the reaction of people to blasting vibration. The main factors are the amplitude, frequency, and duration of blasting vibration [16–18]. Currently, the widely used indices for the evaluation of the blasting vibration comfort are the blasting vibration peak intensity in United States, Canada, United Kingdom, and Australia, maximum weighted vibration intensity () in Germany, quadric vibration dose value (VDV) internationally, and annoyance rate index in China [18]. While the blasting vibration peak intensity is easy to understand and to determine, it neglects the effects of frequency and duration of the blasting vibration. The maximum weighted vibration intensity, , is the weighted peak vibration velocity by frequency [19]. In order to calculate the VDV index, the monitored blasting vibration velocity data needs to be converted into acceleration through mathematic approach, which likely imports some calculating errors [20–22]. The comfort evaluation index of annoyance rate proposed by Song [23] is more complicated and is still in doubt with respect to its applicability to the transient vibration.

For different comfort evaluation methods, the comfort evaluation criteria are also different. Reference [24] suggests that the peak particle velocity (PPV) should not be greater than 10 mm/s, and, for PPV > 5 mm/s, it should be limited to 5% probability. For long-term blasting vibration, PPV should be lower than 2 mm/s. Zhang et al. [25] developed the humanization control indexes for blasting vibration. The thresholds for the ground sensible vibration and the psychologically acceptable vibration are 0.7 mm/s and 5 mm/s, respectively. Yu [26] studied the reaction of a multistorey building and the people inside the building to the blasting vibration. He developed the vibration control indexes for day time, which are 3 mm/s (<10 Hz), 3–5 mm/s (10–50 Hz), and 5–7 mm/s (>50 Hz). Li and Deng [27] evaluated the effects of blasting vibration on human comfort. They found that, for , the peak vibration velocity is <5 mm/s. At this level, the blasting vibration does not annoy humans. Wu et al. [28] used the blasting monitoring data and found that the negative impact of blasting vibration is lowest and the harmonic production can be achieved when the acceleration is less than 110 dB. By analyzing the wavelet analysis energy evaluation index E_{k} and combining it with engineering practice, Chen et al. [29] developed the comfort evaluation method. Currently, there are various blasting vibration comfort indexes and standards and the difference between them is large. Hence, it can be concluded that different blasting vibration comfort evaluation methods and standards are different and, sometimes, the evaluation results are even the opposite [18].

As high-rise buildings exhibit dynamic responses to blasting vibration, people inside buildings, especially high-rise buildings, are affected by the energy and frequency of the blasting vibration. Yu [26] monitored the vibration response at different buildings and at different heights. He found that with low frequencies of blasting vibration, high-rise buildings can produce large vibration amplification effect. On the other hand, with frequencies much higher than the natural frequency of the building, the vibration amplification with the floor is not increased easily. Y. Zhang and Y. Zhang [30] monitored and numerically simulated the vibration velocity of buildings located above tunnels. They found that the peak vibration velocity showed significant amplification effect which increases with building height. Wang et al. [31] carried out field tests and numerical simulation studies on the dynamic response of framed buildings under blasting vibration. They found that the vibration velocity was amplified significantly when the natural frequency of the building was close to that of the blasting vibration. Wierschem et al. [32] validated the efficacy of a proposed passive nonlinear mitigation system to rapidly and efficiently attenuate the global structural response. Currently, research on the amplification effect has been used to evaluate the safety of buildings. However, there is little research on the effect of blasting vibration energy on human comfort in multistorey buildings. The mentioned comfort evaluation methods, such as the blasting vibration peak intensity, maximum weighted vibration intensity , and quadratic VDV, are those on the ground. Hence, sometimes when an evaluation gives a comfort conclusion, it does not fully reflect human comfort in the actual situation.

In this study, first, the human absorbed blasting vibration energy (ABVE) index on the comfort evaluation has been developed. Through analysis of a typical 4-storey brick and concrete building and human vibration characteristics, the elevation amplification effects on ABVE and frequency-based quantitative influence coefficients have been determined. By correcting the ABVE evaluation index quantitatively, the total blasting vibration energy and frequency components received by people at different floors have been accurately determined. As compared to the traditional evaluation methods, the method developed in this study is more accurate and more objective in the evaluation of the blasting vibration comfort.

#### 2. Absorbed Blasting Vibration Energy (ABVE)

The human body is not only affected by the blasting vibration intensity but also by the vibration frequency, duration, and other dynamic factors. In this study, the effect of blasting vibration on people is considered as an energy transfer and conversion. Blasting is an energy source, blasting seismic waves can be considered as energy carriers, and a human body inside a building can be treated as an energy acceptor. The final reaction of a human body can be seen as the reaction results of the receptor. Under certain input and deformation conditions, the body can be regarded as a linear system. A linear parameter centralized system can be used to approximate a vibration system consisting of lifeless mass, flexible and damping elements. Different body parts have their natural vibration frequency. When the blasting seismic waves are transmitted to the floor or seats that are in contact with the body, the vibration energy is transferred into the body, and the energy is transmitted along the body. Energy transfer and conversion concepts can be used to evaluate the vibration response of the human body, which is referred to as the “absorbed blasting vibration energy (ABVE)” [33]. The ABVE can be used as a parameter to characterize the interaction between humans and the vibration environment. Based on the assumptions of human energy transmission and absorption, the absorbed blasting vibration energy per unit time can be described as power, and the mechanical simulation of power can be described as work. As absorbed energy is a measure of the dissipated energy input by the vibration, the absorbed energy by the body during time can be expressed as follows:where* E* is the absorbed energy by the body; is a function of the input force; and is a function of the input speed.

ABVE index is a scalar that has a definite physical meaning and is suitable for periodic and random vibration inputs. The vibrating kinetic energy is considered for evaluating BV comfort [34]. Assuming that the mass is denoted by , the absorbed energy at time* t* is determined by where* E* represents the BV energy and is the BV velocity. Equation (2) can be rewritten asTherefore, ABVE at time* t* can be expressed by the square of the corresponding velocity. With integration, the absorbed energy during a certain period can be determined by where represents the absorbed energy during a certain period and and are the starting time and ending time, respectively.

Since the monitored BV velocities are discrete digital signals, (4) can be rewritten as where is the discrete digital signal of BV velocity, is the total number of samples, and is the sampling interval.

The total blasting vibration energy accounts for the change in energy over time without including the effect of frequency. The power spectral density can describe the relative magnitude of the harmonic component energy within a certain frequency range. Based on the spectral analysis on the blasting vibration velocity, different frequency bands and the corresponding power spectral density can be determined. Then, the ratio of the energy in any one of the frequency bands () to the total energy iswhere is the proportion of the energy within the frequency range in the total energy.

After determining the blasting vibration energy and the spectral analysis of the blasting vibration signal, the entire frequency domain has been segmented. Combining (5), (6), and (7), the energy ratio and magnitude in each frequency band and the total absorbed blasting vibration energy can be determined.

#### 3. Dynamic Response Characteristics of Multistorey Buildings to Blasting Vibration Load

Buildings respond to blasting vibration dynamically. To accurately determine the blasting vibration energy received by a human body in different parts of a building, it is necessary to ascertain the dynamic response of the building. To gain further quantitative understanding of the amplification effect of the building floor elevation on the blasting vibration energy, response of a four-storey brick and concrete building has been monitored. Figure 1 shows that the vibration monitoring points of #1~#4 are at the building foundation (first floor), second floor, third floor, and fourth floor, respectively. There are 20 groups of blasting vibration velocity monitoring data. Figure 2 shows typical blasting vibration waveforms at each floor. This is an indication that the building has responded to the blasting vibration. There is also more blasting vibration energy at the higher floor. According to a statistical analysis of the 20 groups of data, Figure 3 shows the amplification of the peak particle velocity. It can be seen that the peak velocity fluctuates in each direction. Using the calculation method for the ABVE index in Section 2, the total blasting vibration energy at all the floors in all the directions has been determined. Figure 4 and Table 1 show the amplification factor of the ABVE at each floor, which means the ratio of ABVE of each layer to the ABVE of the foundation layer. It can be seen that the amplification is greater at the higher floor. This suggests that the people at the higher floor will absorb more blasting vibration energy than those at the lower floor. Based on the monitoring data, the quantitative energy amplification factors of each floor in the 4-storey brick-concrete building have been determined, as shown in Table 1.