Construction Safety Research Articles

Critical safety climate dimensions for improved safety behavior: perspectives of construction workers

Although extensive research has been conducted to explain the high accident rates in the Indian construction industry, studies focusing on the contributions of the prevailing safety climate as an enabler of such incidences remain sparse. Safety climate plays a crucial role in shaping workers’ safety behaviors. Therefore, eliciting the perspectives of construction workers concerning safety climate dimensions that are critical for engendering improved safety behavior will provide valuable insights into the dimensions required to sustain the desired safety performance levels on construction sites. This study adopted a sequential mixed-methods research design. Purposively selected respondents and interviewees were surveyed and interviewed at various intervals. The study established that safety climate dimensions, such as effective leadership, effective communication, consultation, training, resources, incentives, and recognition, are critical in improving safety behavior among construction workers. The results of this study have significant implications for practice and knowledge, as they provide an approach for assessing the impact of different safety climate dimensions on the safety behavior of construction workers in India. Understanding these dimensions will lead to a framework for managing these challenges and improving construction safety performance. The study reported in this paper remains one of the few studies seeking to explore the impact of safety-climate dimensions on worker safety behavior in the construction industry.

Decision‐making regarding safety investments: A case study of fluidized‐bed reactors

AbstractIn chemical plants, the pressure to prioritize production and minimize operating costs often leads to delays in safety investments. To allocate limited management resources effectively, decision‐making regarding safety investments must follow a logical approach. This article outlines how engineers can provide valuable information to the management, enabling them to make informed decisions. We demonstrate that decision‐making involves both technical and economic considerations, following a well‐defined process with distinct stages. This study highlights the importance of technical data in making informed decisions regarding safety investments. Decision makers must consider various factors, including risk assessment, economic efficiency, technology reliability, and construction safety. In addition, economic efficiency considerations should incorporate new proposals that account for environmental profit/loss. Our findings confirm that effectiveness of the proposed method, particularly when applied to fluidized‐bed reactors. In conclusion, accurate allocation of management resources at appropriate times leads to reasonable risk reduction.

Enhancing Sustainable Safety Practices in Construction: Insights from Cultural and Socio-Economic Analysis

Exploring cultural diversity and socio-economic factors offers a holistic approach to fostering sustainable safety practices within the construction industry. This study investigates the relationship between cultural and socio-economic factors and their influence on safety practices within the construction industry, focusing specifically on Saudi Arabian construction. Employing a comparative research design, data were gathered through a questionnaire distributed among various stakeholders, including construction workers, safety officers, project managers, supervisors, and other professionals involved in construction projects. Structural equation modeling (SEM) was utilized to analyze the relationships between cultural, socio-economic, and safety practices. The findings showed significant associations of cultural and socio-economic factors with safety practices and attitudes. Specifically, positive workplace norms and values, effective communication styles, higher income levels, and better education and literacy levels were found to positively influence adherence to safety guidelines and the effectiveness of training programs. Conversely, job insecurity exhibited a negative impact on safety-related outcomes and training effectiveness. This study demonstrates the importance of fostering a positive safety culture within organizations, emphasizing leadership commitment, effective communication, and employee engagement. It also highlights the significance of addressing socio-economic factors, such as job security, income levels, and education, to promote a safer work environment and enhance safety practices. Practical implications derived from the research findings offer actionable insights for organizations to develop targeted interventions aimed at improving sustainable safety practices and training effectiveness within the construction industry in Saudi Arabia.

Decentralized adaptive work package learning for personalized and privacy-preserving occupational health and safety monitoring in construction

Precision construction occupational health and safety (COHS) is a prerequisite for project success. Work package-based distributed monitoring shows a high capability for this purpose. However, a theoretical dilemma exists between larger work packages with greater technical efficiency and smaller ones with greater data privacy. This paper develops a decentralized adaptive work package (DAWP) learning model and blockchain for personalized COHS monitoring. The DAWP learning model is first formulated to form adaptive topologies to concatenate and share model parameters of work packages with their neighbors. DAWP learning can compute graphs using mixing weights and similarity to improve personalization. Then, studying blockchain can transform DAWP into a decentralized collaboration. Lastly, blockchain-DAWP (BC-DAWP) is evaluated by controlled experiments of multiple monitoring tasks. The results indicated that the BC-DAWP with lightweight models outperforms the proposed baselines in a personalized and privacy-preserving manner, which paves the way for the next-generation decentralized COHS monitoring.

Assessment of Tunnel Lining Stability through Integrated Monitoring of Fiber Bragg Grating Strain and Structural Deformation.

Tunnel excavation induces the stress redistribution of the surrounding rock. Structural cracks may develop in the secondary lining due to this stress redistribution and bias pressure, consequently affecting the overall construction safety of the tunnel. This paper aims to achieve real-time monitoring of the excavation stability of the lining structure by integrating two monitoring technologies: structural deformation monitoring and fiber grating strain monitoring. Additionally, it proposes a method to simultaneously measure the thermal strain and applied stress-strain of the structure. By analyzing the displacement and deformation of the lining structure, its stability can be preliminarily evaluated in the short term. To achieve long-term real-time monitoring and a more accurate assessment of the tunnel structure's stability, the paper introduces fiber Bragg grating (FBG) strain sensor monitoring technology. First, based on the geological stratigraphy information obtained from the exploration, a simulation model of the tunnel under different section bias angles is established. The displacement and stress concentration areas of the lining structure are then analyzed to optimize the sensor deployment array and provide a theoretical basis for the sensor arrangement. FBG strain sensors are installed on the surface of the structure to measure thermal strain and loading stress-strain, whereas FBG temperature sensors measure local temperature. The findings indicate that following tunnel excavation, the maximum daily strain differences at K107+043 and K107+240 were 126.87 µε and 209.38 µε, respectively. After a period of rock disturbance, the average daily strain differences due to applied stress-strain were 16.8 µε and 12.65 µε, respectively. The thermal strain was close to the daily strain difference. Therefore, after the rock disturbance subsided, the strain fluctuations in the lining structure were mainly caused by local temperature changes, and the surrounding rock tended to stabilize. This offers a viable method for evaluating structural stability post-tunnel excavation.

Analysis and Real-Time Monitoring of the Influence of Wind Load on a High-Altitude Steel Connecting Bridge with Small Spacing

With the development of steel-structure construction technology in high-rise buildings, the design and construction of high-rise steel structures tend to be complicated. Based on the Zhuhai Tiejian Square project, the fluid-structure coupling calculation analysis and on-site monitoring are carried out in view of the wind load of the high-altitude steel-structure connecting bridge in the hoisting stage of the Zhuhai Tiejian Square project. The main structure of the project is four towers and five high-altitude, small-spacing steel structures connecting the four towers. The lifting process of the third zone is taken as the analysis object, and the hoisting idea of “low-altitude hoisting, overall lifting” is adopted. Because the span of the high-altitude steel-structure connecting bridge is small and the installation height is high, the influence of wind load on the hoisting process cannot be ignored. Therefore, the unidirectional fluid-structure coupling model of the high-altitude small-space steel-structure connecting bridge in the third zone was established by using CFD calculation software ANSYS Fluent 2022 R1, and the corresponding flow field and solid calculation results were obtained and analyzed. The analysis results show that the lifting structure still produces a certain deformation when the wind speed is 5 m/s or 10 m/s, and the calculation results show that the stress calculation results are still within the safe range of steel strength for the sensitivity of the lifting structure under wind load. With the increase of wind speed, the local maximum stress of the structure increases greatly, but the overall deformation remains stable, which indicates that the greatest challenge of hoisting steel structures under wind load may be the stability direction rather than the strength, so it is necessary to strictly monitor the displacement deformation of the structure during construction. Then, through the monitoring of the overall lifting process of the high-altitude, large-span, steel-connected structure of Zhuhai Tiejian Square from pre-lifting to formal lifting, real-time monitoring and data analysis show that the lifting process of the high-altitude steel bridge of Zhuhai Tiejian Square is safe and reliable, the force transformation of each component is reasonable, the lifting process is relatively stable, the external environment has little impact, and the expected monitoring effect has been achieved. The calculation simulation and on-site monitoring in this paper can provide theoretical and practical guidance for the construction safety under the influence of wind load in the construction process of high-altitude steel-structure hoisting, and provide an important reference value for similar projects.

Evaluation of cooling measures performance and thermal-humidity environment for ultra-high geothermal railway tunnel construction by using WBGT

High-geothermal damage is one of the major challenges in high-speed railway tunnel construction. Current studies have shortcomings in the formation mechanism of tunnel environment and the environment evaluation system. This may lead to an over-optimal environmental acceptability evaluation and jeopardize tunnel construction safety. This study established a mathematical model of the tunnel environment formation mechanism, proposed the wet-bulb globe temperature (WBGT) standard (26.49°C) for the tunnel construction, analysed the cooling efficiency of different environmental control measures. The results show that increasing the mechanical air supply volume can reduce tunnel temperature. Fog cannon can reduce the air temperature near the tunnel working face, the cooling range in front of the tunnel working face is 10.8 m. The cooling shield can control the WBGT below the standard. Under the 90°C rock temperature, the environmental acceptability of the tunnel under pure mechanical ventilation is 0%; the single fog cannon and double fog cannon (both cooperate with double-duct ventilation) are 22.85% and 54.29% respectively; the cooling shield with one fog cannon and double duct ventilation is 95.72%. This study improves the tunnel environment evaluation system during the construction stage, and provides design reference for temperature control measures in tunnel construction. Highlights: Tunnel environment under the impact of multi-physical coupling fields was analysed. Thermal radiation is taken into account in the formation of the tunnel environment. A new benchmark based on WBGT for high-geothermal tunnels construction was proposed. A tunnel environment assessment system was proposed. Cooling shield environmental-control measure was proposed for tunnel construction.

Prediction of Buildings’ Settlements Induced by Deep Foundation Pit Construction Based on LSTM-RA-ANN

In view of the shortcomings of existing methods for predicting the settlement of surrounding buildings caused by deep foundation pit construction, this study uses the monitoring data of a foundation pit project in Shanghai and divides the construction process of the pit into three working conditions, that is, enclosure construction, earthwork excavation, and basement support construction. The attention mechanism and residual update are integrated into the artificial neural network (ANN) model, and the root-mean-square error, average absolute error, and determination coefficient are used as the evaluation indices of the model. The artificial neural network prediction model LSTM-RA-ANN for building settlements in deep foundation pit construction was then established. The prediction performance of the model was also analysed under different working conditions, and the influences of the main factors (including the soil parameter, monitoring point location, activation function, hyperparameter, and input number) on the evaluation index was further explored. The results indicate that the performances of the established LSTM-RA-ANN model are closely related to the construction conditions, the predicted settlements agree well with the monitored ones in three working conditions with the greatest errors occurring at a later time of the working conditions, and the prediction accuracy of the great–small order corresponds to basement support, enclosure construction, and earthwork excavation respectively. The farther the monitoring point is from the edge of the pit, the better the model performance is. The activation function, initial learning rate, and maximum iteration batch have a great influence on the evaluation indices of the model, while the number of input points has little effect on the evaluation indices. These results may serve as a reference for the safe construction and normal operation of foundation pit engineering.

Analysis of the Effect of Outdoor Thermal Comfort on Construction Accidents by Subcontractor Types

The impact of climate on construction site safety varies significantly depending on subcontractor types due to the diverse nature of workplaces and work methods. This study introduces a novel approach by categorizing construction work according to subcontractor types and assessing accident risk probabilistically through the Physiologically Equivalent Temperature (PET), an outdoor thermal comfort index. Additionally, a Hidden Markov Model (HMM)-based clustering methodology was proposed to classify new groups using PET and accident probability. This study proceeded in the following sequence: (i) collection and classification of data, (ii) PET calculation, (iii) calculation of accident probability, and (iv) clustering and Pearson correlation coefficient analysis. As a result of clustering, each group was classified according to the workplace. Groups 2 and 3 demonstrated a strong positive correlation between accident probability and PET, with correlation coefficients of 0.837 and 0.772, while Group 1 exhibited a moderately positive correlation of 0.474. This study quantitatively evaluated the impact of climate on workers for each subcontractor type using PET, an outdoor thermal comfort index for construction work, and accident probability, resulting in the identification of new groups. The findings of this study may serve as novel benchmarks for safety management in construction worker safety based on PET.

Spalling Criterion of Hard Brittle Rock Mass Based on Dilatation Lateral Strain.

Spalling failure is a typical failure phenomenon after excavation and unloading of a deep, hard brittle rock mass, which seriously threatens the safe construction of deep roadways (tunnels) and other projects. From the engineering viewpoint, it is essential to accurately evaluate the range and depth of surrounding rock spalling failure. From the perspective of the laboratory and engineering site, the strength and formation mechanism of hard rock spalling failure were statistically summarized and analyzed. Under uniaxial and low confining pressure conditions, when the load reached the rock damage stress, cracks in the rock penetrated to form a failure plane approximately parallel to the axial loading direction, and the strength of rock mass spalling was much smaller than that of intact rock spalling. A triaxial compression test was conducted to analyze the dilatation axial strain and dilatation lateral strain characteristics of gneiss. The results showed that dilatation axial strain gradually increased with the increase of confining pressure, whereas dilatation lateral strain was almost unchanged. Therefore, a safety factor (FS) based on dilatation lateral strain was developed. Through comparison with other strain-based spalling criteria, the establishment and physical meaning of the method were described in detail. In addition, FS was applied to analyze the deep roadway of the Hongtoushan Copper Mine in China and the Rm415 test tunnel in Canada. The results showed that the spalling criterion could accurately indicate the range and depth of the surrounding rock spalling failure, which verified the rationality and applicability of the new spalling criterion. Thus, FS can be utilized as a new theory and analysis tool for the assessment and prevention of spalling failure in deep hard rock roadways.

Exploring the feasibility of prestressed anchor cables as an alternative to temporary support in the excavation of super-large-span tunnel

AbstractExcavating super-large-span tunnels in soft rock masses presents significant challenges. To ensure safety, the sequential excavation method is commonly adopted. It utilizes internal temporary supports to spatially partition the tunnel face and divide the excavation into multiple stages. However, these internal supports generally impose spatial constraints, limiting the use of large-scale excavation equipment and reducing construction efficiency. To address this constraint, this study adopts the “Shed-frame” principle to explore the feasibility of an innovative support system, which aims to replace internal supports with prestressed anchor cables and thus provide a more spacious working space with fewer internal obstructions. To evaluate its effectiveness, a field case involving the excavation of a 24-m span tunnel in soft rock is presented, and an analysis of extensive field data is conducted to study the deformation characteristics of the surrounding rock and the mechanical behavior of the support system. The results revealed that prestressed anchor cables integrated the initial support with the shed, creating an effective “shed-frame” system, which successively maintained tunnel deformation and frame stress levels within safe regulatory bounds. Moreover, the prestressed anchor cables bolstered the surrounding rock effectively and reduced the excavation-induced disturbance zone significantly. In summary, the proposed support system balances construction efficiency and safety. These field experiences may offer valuable insights into the popularization and further development of prestressed anchor cable support systems.

A data-driven and knowledge graph-based analysis of the risk hazard coupling mechanism in subway construction accidents

With the development and expansion of subway construction, accidents usually cause economic losses and seriously threaten personnel safety. Exploring the experience and lessons from accident reports is beneficial for promoting subway construction safety management. Therefore, this study proposes a data-driven and knowledge graph-based approach to reveal the coupling mechanism of risk hazards in subway construction. A total of 231 subway construction accident reports in China from 2001 to 2023 are collected as the database of the knowledge graph. By developing a subway construction safety accident knowledge graph (SCSAKG), the potential paths for accidents can be revealed. To further investigate the internal features of the knowledge graph, topological indicators are proposed to explore the relationships between hazards, hazard types, hazard frequencies, hazard occurrence times, accidents, and accident consequences. Prevention strategies for key risk hazards in subway construction are developed based on the proposed coupling mechanism. The proposed methods that combine knowledge graphs with accident reports can provide decision-making references for subway construction safety management.

Development of a Multi-Robot System for Pier Construction

The construction industry is a challenging field for the application of robots. In particular, bridge construction, which involves many tasks at great heights, makes it difficult to implement robots. To construct a bridge, it is necessary to build numerous piers that can support the bridge deck. Pier construction involves a series of tasks including rebar connection, formwork installation, concrete pouring, formwork dismantling, and formwork reinstallation. These activities require working at heights, presenting a significant risk of falls. If bridge construction could be performed remotely using robots instead of relying on human labor, it would greatly contribute to the safety of bridge construction. This paper proposes a multi-robot system capable of remote operation and automation for rebar structure connection, concrete pouring, and concrete vibrating tasks in pier construction. The proposed multi-robot system for pier construction is composed of three robot systems. Each robot system consists of a robot arm mounted on a mobile robot that can move along rails. And to apply the proposed system to a construction site, it is essential to implement a compliance control algorithm that adapts to external forces. In this paper, we propose an admittance control that takes into account the weight of the tool for the compliance control of the proposed robot, which performs tasks by switching between various construction tools of different weights. Furthermore, we propose a synchronization control method for the multi-robot system to connect reinforcing structures. We validated the proposed algorithm through simulation. Furthermore, we developed a prototype of the proposed system to verify the feasibility of the suggested hardware design and control.

A method for predicting deformation field of deep foundation pit considering spatial effect

Urban underground spaces have experienced significant development and utilization due to the rapid progress of urban construction and continuous advancements in construction technology. The number of foundation-pit projects immediately adjacent to buildings, structures, and pipelines has been increasing. Ensuring the safety of construction and surrounding facilities, it is essential to predict deformation caused by foundation pit excavations. In this study, a simple calculation method was proposed for predicting deformation of an envelope structure and surface settlement caused by deep foundation excavation with spatial effects. Firstly, the principle of minimum potential energy was applied and the lateral displacement equation of the envelope structure was derived, considering spatial deformation effects. Secondly, based on linear elasticity theory, a surface settlement expression was formulated utilizing the plane strain boundary. Finally, the stratigraphic loss method was used to establish a connection between horizontal envelope deformation and surface settlement, allowing for calculations of surface settlement at any position behind the envelope structure. The effectiveness and practicability of the proposed method were demonstrated by comparison of two existing foundation-pit engineering examples.

How safety value is exchanged in Chinese modern megaprojects: A stakeholder value network perspective

To visualize and quantify these exchanges among primary stakeholders in megaprojects, this study introduces network stakeholder value network as the core methodology. Starting with a qualitative organizational safety behavior model encompassing 8 stakeholders and 61 value flows, it's built based on 3 organizational safety behavior categories. Moreover, questionnaire data from 356 experts quantifies the model, and the design structure matrix identifies 13845 safety value paths, including 4827 cycles. Analysis delves into critical cycles, stakeholders, flows, and organizational safety behavior types to refine safety strategies. The findings, based on Chinese megaprojects, suggest that contractors and governments must lead safety awareness efforts, with safety compliance paramount for all parties. The study's contributions are threefold: firstly, it broadens the scope to encompass organizational safety behavior; secondly, it introduces a novel approach to visualize and quantify safety value flows; and thirdly, it considers multiple types of value exchanges, underscores their significance in promoting safety value, and offers practical recommendations to strengthen construction safety performance.

Multifractal Characteristics and Displacement Prediction of Deformation on Tunnel Portal Slope of Shallow Buried Tunnel Adjacent to Important Structures

The tunnel portal section is often in extremely weak and fragmented strata, and the deformation of the portal side and slope will affect the stability of the surrounding rock and the tunnel-supporting structure. However, the deformation characteristics and displacement development patterns of slopes in the tunnel portal section are not clear. In this paper, the multifractal characteristics and displacement prediction of the deformation sequence of the tunnel portal slope at of a weak and water-rich shallow buried tunnel adjacent to an important structure are studied in depth. Combined with the deformation characteristics of the tunnel portal slope, a suitable slope monitoring and measurement scheme is designed to analyze the deformation pattern of the tunnel portal slope. Based on the multifractal detrended fluctuation analysis (MF-DFA) method, the multifractal characteristics of the deformation monitoring sequences at each monitoring point of the tunnel portal slope are analyzed. The multifractal characteristics of displacement sequences at different monitoring points of the tunnel portal slope are consistent with the actual monitoring results. Furthermore, the Long Short-Term Memory (LSTM) model is optimized using the Particle Swarm Optimization (PSO) algorithm to predict the deformation of the tunnel portal slope. The results show that the maximum mean square error (MSE) of the horizontal displacement test set prediction results is 0.142, and the coefficient of determination (R2) is higher than 91%. The maximum value of MSE for vertical displacement test set prediction is 0.069, and the R2 are higher than 91%. The study shows that the performance of the PSO-LSTM prediction model can meet the requirements for predicting the displacement of the tunnel portal slope. Based on the MF-DFA method and PSO-LSTM prediction model, the fluctuation characteristics of the displacement value of the tunnel portal section can be accurately identified and the displacement development pattern can be effectively predicted. The conclusions of the study are of great practical significance for the safe construction of the tunnel portal section.

Characteristics of sandstone unloading creep and modelling for safe tunnel construction under high perimeter pressure and high pore water pressure condition

Research on the properties of sandstone in the tunnel environment has been conducted due to the building industry’s rapid development, which is gradually involving underground water. Sandstone used in tunnel construction is susceptible to high perimeter and water pressures as a result of the abundance of sand and gravel close to groundwater, which might result in mishaps resembling collapses. The modified Burgers Model for the Malm dataset is the foundation of this study, which aims to reduce the internal crack extension caused by sandstone’s unloading creep. First, the study increased the material’s Poisson’s ratio in accordance with the Mohr–Coulomb strength criterion and builds a triaxial loading model on its foundation. Next, it analyzed the extension of the fracture surface of sandstone while taking high peripheral pressure and high hydraulic pressure into account. Finally, it discretized the unloading creep of sandstone using the improved Burgers model. On the basis of the model put forward in the study, experimental validation was then done on the Malm dataset. The sandstone would reach the final rupture area without any protection measures in just 10 days, but the model suggested in the study can delay this time to 200 days, while the effects of the other three models would delay this time by 75, 60, and 41 days, respectively. The model’s breadth was indicated by the linear fit value of 0.9827 for 36 experiments. The experimental findings demonstrated that the model suggested in the study can successfully lower the rate of sandstone unloading creep and increase worker safety.

Predictive modeling of shallow tunnel behavior: Leveraging machine learning for maximum convergence displacement estimation

Accurate prediction of maximum convergence in unsupported, shallow tunnel construction is crucial for optimizing the lining and ensuring tunnel safety. Machine learning (ML) algorithms, especially through boosting techniques, enable effective solution of complex engineering problems and demonstrate their capabilities in problem solving and optimization. In this study, the FLAC 3D package was used to create a robust and validated database of 954 datasets. Five tree-based ML algorithms, including extreme gradient boosting (XGBoost), adaptive boosting (AdaBoost), gradient boosting machine (GBM), histogram-based gradient boosting (HGB) and categorical boosting (CatBoost), were used to predict the maximum convergence displacement for unsupported shallow tunnels. For the test dataset, XGBoost outperformed the other models with an excellent coefficient of determination of 0.9633, a minimum mean absolute error of 0.0021 and a low root mean squared error of 0.00725. HGB followed closely behind, and GBM and CatBoost showed strong performances, while Adaboost was less effective. The superior performance of XGBoost highlights its effectiveness in predicting maximum convergence in shallow tunnels. An in-depth sensitivity analysis within the XGBoost model showed the significant influence of soil elastic modulus on the maximum convergence displacement in unsupported tunnels. The remarkable results achieved by the XGBoost algorithm on our complex tunnel convergence predictions illustrate the profound ability of ML to tackle complicated geotechnical challenges. This interdisciplinary collaboration demonstrates the potential of advanced algorithms to improve safety and efficiency in construction, underlining the crucial role of technology in tackling complex problems and establishing a new paradigm for innovation in the field.

Numerical Simulation Study on the Effective Distance of Pressurized Ventilation in Gas Tunnel Construction

The ventilation of gas tunnel construction has always been a difficult point in the construction of gas tunnels, and the construction risk is high, and the ventilation cost is large. How to efficiently and quickly analyze the gas emission of different sections and take corresponding ventilation measures can improve the safety of gas tunnel construction and reduce the consumption of funds. Therefore, in this paper, the source term of gas emission is used to deal with it, and the actual pollution source is regarded as the source term in the air at a small distance from the wall of the tunnel face, and its emission is the actual emission of the tunnel gas source, and the source term S of these units is equal to the amount of gas generated per unit volume and unit time. Numerical simulation analysis can be carried out more vividly for the improvement of the construction safety of gas tunnels. In recent years, with the proposal of China's "double carbon" goal, the requirements for green construction have also been raised to a new height, and the ventilation standards for gas tunnel construction are getting higher and higher.

Comparative Analysis of Health and Safety Training Practices: Advancing Safety in Nigerian Construction

Comparative Analysis of Health and Safety Training Practices: Advancing Safety in Nigerian Construction