*3.3. Stage III (LCIA)—Life Cycle Impact Assessment*

Cycle I—construction of the MASH building/determination of cumulative QI cost equivalents

This stage was limited to the construction of a steel hall, while the costs of its use were omitted as secondary. Operating costs are variable and depend on the manner in which the structure is used (e.g., trade, production hall, etc.).

This is undoubtedly the most important stage of the selection analysis because it should define the optimal structural and ecological solution of the halls. The essence of this phase consists of the proper preparation of the object in terms of its secondary assembly and operation so that the energy accumulated in the mass of the structure is used to restore the lost ecological substance. The EET method was adopted to calculate the QI k,l equivalent energy and material costs in the first phase of the MASH structure for scheme "k" and span "l".

$$\mathbf{Q}^{\rm I}\_{\rm k,l} = (\boldsymbol{\Sigma}\boldsymbol{\Gamma}^{\rm I}\_{\rm si} + \boldsymbol{\Sigma}\boldsymbol{\Gamma}^{\rm I}\_{\rm ri} + \boldsymbol{\Sigma}\boldsymbol{\Gamma}^{\rm I}\_{\rm xi} + \boldsymbol{\Sigma}\boldsymbol{\Gamma}\mathbf{F}^{\rm I}\_{\rm i} + \boldsymbol{\Sigma}\mathbf{R}\mathbf{F}^{\rm I}\_{\rm i} + \boldsymbol{\Sigma}\mathbf{W}^{\rm I}\_{\rm i} + \boldsymbol{\Sigma}\boldsymbol{\Gamma}^{\rm I}\_{\rm mi} + \boldsymbol{\Sigma}\mathbf{T}^{\rm I}\_{\rm mi} + \boldsymbol{\Sigma}\mathbf{M}^{\rm I}\_{\rm i} + \boldsymbol{\Sigma}\mathbf{P}^{\rm I})/\mathbf{p} \, [\text{EURO}/\text{m}^2] \tag{1}$$

Construction cost in phase I of QI k,l includes the following components:


The summary of QI k,l values for schemes A, B, C and D and a span of up to 48 m is presented in Figure 3.

After cycle I of the hall construction work, the cumulative construction costs of MASH QI presented in Figure 3 reflect only the physical parameters of the adopted typological variants of the hall. At this stage, it is possible to conclude that the halls with rigid frames (scheme A) have the lowest economic cost-to-area ratios at the level of 400- 550 EUR/m2 for spans of 12–30 m, which does not prejudge their selection, as the ecological impacts throughout their life cycle have not been taken into account.

Cycle II—dismantling and reassembly, the second stage of MASH's work.

At this stage of the analysis, the QII k,l cumulative costs related to the relocation of the existing facility to another location were calculated.

**Figure 3.** Cumulative QI cost per 1 m2 of the built-up area.

Assembly errors (manufacturing imperfections) that may occur in support nodes have been taken into account. The change in the stress state of the structure optimized in stage I was examined in terms of achieving a minimum weight. The degree of stress of the structure after the second and subsequent assembly has a significant impact on the change (possible strengthening) of the nodal elements of the hall. Improper preparation of structural welds at the stage of construction may cause imperfections of geometrical contacts [66].

In the process of demolition, the structure is exposed to angle deformation α, β, γ and linear u, w and v of the plates in the assembly joints (Figure 4).

**Figure 4.** Scheme of imperfections of angular and linear butt contacts.

Therefore, it is necessary to test and carry out maintenance and measurement adaptation works in workshop conditions to adapt the object for reuse.

Including the criteria listed in chapter 3, the cumulative equivalent energy and material cost QII k,l was determined in the second life phase of the MASH structure for the scheme "k" and span "l".

$$\mathbf{Q}^{\text{II}}\_{\text{k},\text{l}} = (\boldsymbol{\Sigma}\boldsymbol{\Lambda}\boldsymbol{\mathsf{C}}^{\text{II}}\_{\text{s}\text{i}} + \boldsymbol{\Sigma}\boldsymbol{\Lambda}\mathbf{C}^{\text{II}}\_{\text{r}\text{i}} + \boldsymbol{\Sigma}\boldsymbol{\Lambda}\mathbf{C}^{\text{II}}\_{\text{r}\text{i}} + \boldsymbol{\Sigma}\mathbf{C}\mathbf{F}^{\text{II}}\_{\text{i}} + \boldsymbol{\Sigma}\mathbf{R}\mathbf{F}^{\text{II}}\_{\text{i}} + \boldsymbol{\Sigma}\mathbf{W}^{\text{II}}\_{\text{i}} + \boldsymbol{\Sigma}\mathbf{T}^{\text{II}}\_{\text{mi}} + \boldsymbol{\Sigma}\mathbf{M}^{\text{II}}\_{\text{i}} + \boldsymbol{\Sigma}\mathbf{D}^{\text{I}}\_{\text{i}} + \boldsymbol{\Sigma}\mathbf{D}^{\text{II}}\_{\text{i}})/\text{p} \text{ [EURO/m}^2\$ \tag{2}$$

Energy cost QII k,l includes the following components:



Figure 5 shows the cumulative LME cost (labor, material, equipment) of the structure in the second phase of its operation, i.e., reuse. The cost was summarized for an area of 1 m<sup>2</sup> of the MASH building area. From the estimated charts, it is possible to initially accept the hall solutions in schemes C and D due to the favorable price parameters. In particular, halls with a span of 12 m to 30 m should be distinguished. Their price threshold is at the level of 270–330 EUR/m2 of the total value of QII k,l of the second assembly of MASH.

**Figure 5.** Cumulative cost QII of stage II per 1 m2 of the built-up area.

*3.4. STAGE IV (LCI—Life Cycle Interpretation)—Interpretation of Results*

At each stage of the facility's life (HSWM-BOMM), the EET analysis presents the distribution of the calculated values of the UE and UK sub-indices as shares of the Qk,l cumulative ecological cost. These are the components responsible for ecological losses and gains.

Interpretation of Cycle I results:

Stage of creating the MASH structure

The cumulative value of Q<sup>I</sup> k,l (Equation (3)) includes the economic and ecological costs associated with the implementation and assembly of the UK<sup>I</sup> structure as well as environmental regeneration and disposal of UEI construction waste:

$$\mathbf{Q}^{\mathrm{I}}\mathbf{k}\_{\mathrm{k},\mathrm{l}} = (\mathbf{U}\mathbf{E}^{\mathrm{I}} + \mathbf{U}\mathbf{K}^{\mathrm{I}})/\mathbf{p} \,\mathrm{[EURRO/m^{2}]}\tag{3}$$

UE<sup>I</sup> —share of the ecological costs of environmental regeneration in the process of execution and operation of MASH,

UK<sup>I</sup> —share of economic costs for the execution and assembly of the MASH facility structure (original hall structure cost).

The shares of UE<sup>I</sup> and UKI of the cost of building QI k,l presented in Table 1 were examined in terms of environmental impacts in the I cycle of life of MASH and then in the II cycle of life, i.e., another assembly. Ecological costs of UEI are considered necessary in the construction process, directly interfering with the biotic layer of the area on which the building stands. These include the components ΣRFI <sup>i</sup> + EP<sup>I</sup> , which will be charged with construction costs in the first phase of life.

**Table 1.** Share of UEI ecological (environmental) and UKI economic costs.


Breaking down the cumulative costs of building the hall at UKI and UE<sup>I</sup> allows making an approximate selection of the MASH structure already in the first phase of construction work. It should be noted that the UKI component contains energy and material elements that are the subject of reuse, e.g., ΣC<sup>I</sup> si + ΣCI ri + ΣCI zi components and energy lost components such as ΣW<sup>I</sup> <sup>i</sup> + ΣT<sup>I</sup> <sup>i</sup> + ΣMI i. In the approach to the environmental costs of multiple uses of MASH's technological and operational elements and processes, this will be of significant importance. Referring to the share of UE<sup>I</sup> regeneration costs, i.e., restoration of the biologically active surface, it seems right to include them in the proecological costs, despite the destruction of the active layer of the biocenosis by foundation works and the zero state.

The total share of energy and material involved in the structure of the UKI superstructure itself (part of the building above the ground) of the selected models of hall facilities in Figure 6 is an introduction to the environmental LCA comparative analysis.

**Figure 6.** KJI unit cost of creating the UKI structure per 1 m2 of the built-up area [EURO/m2].

The structure of MASH in the first stage of construction, presented in Figures 3 and 6, confirms the initial correctness of the hall selection due to the total energy and material costs of KJI (Equation (4)) of all manufacturing processes for scheme A.

$$\text{UK}^{\text{I}} = \text{UK}^{\text{I}} / \text{p [EURO/m}^{2}\text{]} \tag{4}$$

where:

KJ<sup>I</sup> —unit cost of construction creation, [EURO/m2],

UK<sup>I</sup> —share of economic costs for the execution and assembly of the MASH facility structure (original hall structure cost), [EURO],

p—built-up area, [m2].

This proves the low impact of the economic costs of foundation work on the total QI accumulated costs. However, one should not forget about the costs of the ecological impacts generated by the construction of the MASH structure. The scope of these impacts is defined by the generalized ecological indicator WEI o (Figure 7) as the ratio of the ecological costs of the UEI to the economic costs of the UKI .

**Figure 7.** Ecological generalized WEI o index – cycle I of LCA.

Optimal solutions are contained between the schemes of construction C—with the lowest values of the WE<sup>I</sup> o index (Equation (5))—and scheme A, which shows the highest level.

$$\text{WE}^{\text{I}}\_{\text{o}} = \text{UE}^{\text{I}} / \text{UK}^{\text{I}} \tag{5}$$

Figure 7 shows that the ecological profitability of construction solutions is the best for the range marked "from below" by schemes C and D—this impact is 37–23%, while for schemes A and B the values of ecological indicators for construction WE<sup>I</sup> o are the highest and amount to 61–30%. The higher the ecological indicators, the higher the environmental costs generated by the structure.

The presented WE<sup>I</sup> o index is a value enabling the initial selection of a structure because, as already mentioned, the cumulative QI k,l costs contain partial elements responsible for losses and ecological gains in the MASH construction process. Therefore, it is necessary to carry out a further analysis of the impact of these components on the selection of the optimal structure in the full life cycle and, therefore, in the subsequent assembly phases.

Interpretation of the results of Cycle II of the analysis—option 3 was adopted; therefore, it is the phase of demolition of the MASH building structure, including the foundations.

After calculating the cumulative cost of QII k,l (Equation (6)), similarly to the first stage, its distribution was examined into:

$$\mathbf{Q}^{\mathrm{II}}\_{\mathrm{k},\mathrm{l}} = (\mathbf{U}\mathbf{E}^{\mathrm{II}} + \mathbf{U}\mathbf{K}^{\mathrm{II}})/\mathrm{p} \text{ [EURO/m}^2\mathrm{l}\text{]}\tag{6}$$

UEII—ecological cost of compensation for the lost layer of biocenosis (regenerating the environment) in the process of the secondary assembly and operation of MASH,

UKII—economic cost of reassembling the MASH structure elsewhere as a factor that degrades the environment with the use of elements from the first cycle of the facility's operation.

The ratio of ecological to economic costs will be used to search for the optimal design solution from the point of view of the ecological impacts of MASH. The shares of the individual components of QII are presented in the ecological generalized index of cycle II of the work of the WEIIo structure.

$$\text{UE}^{\text{II}}\_{\text{o}} = \text{UE}^{\text{II}} / \text{UK}^{\text{II}} \tag{7}$$

The table below shows the components UEII and UKII of the cumulative cost QII k,l. Table 2 presents the ecological costs ΣRFIIi+ EPII, necessary to regenerate the biologically active area (built-up area). The share of UEII ecological (environmental) costs in the second phase is crucial in the LCA assessment of the hall structure. Generalized ecological indicators [WEII o k,l ] create a picture (Figure 8) of the impact of individual types of HSWM on ecological costs, included between the envelopes:

**Table 2.** Share of UEII ecological and UKII economic costs of LCA cycle II.


**Figure 8.** Generalized ecological indicator WEIIo—cycle II.

	- type B for L = 12–13.5 m, WEII o k,l = 0.95–1.1
	- type C for L = 13.5–39 m, WEII o k,l = 0.85–0.65
	- type D for L = 39–48 m, WEII o k,l = 0.65–0.55
	- type A for L = 12–48 m, WEII o k,l = 1.35–0.65.

Ecological indicators WEII o k,l of the structure are at the level of 0.55–0.65 for the largest spans of 39–48 m, which proves the lowest share of 35–45% of ecological costs in the entire investment.

The unit cost of construction is:

$$\text{UK}^{\text{II}} = \text{UK}^{\text{II}} / \text{p} \text{ [EURO/m}^2\text{]} \tag{8}$$

where:

KJII—unit cost of construction creation, [EURO/m2]

UKII—economic cost of reassembling the MASH structure elsewhere as a factor that degrades the environment with the use of elements from phase I of the facility's operation, [EURO],

p—built-up area, [m2].

At the same time, in the second cycle of the hall structure's life, the UKII economic costs (as shown in Figure 9) are more than twice lower than the new structure and amount to approximately 130–180 EUR/m2 for typical spans from 12–30 m, assuming the implementation of the investment on the *Just in time* basis [47].

**Figure 9.** KJII unit cost of creating the UKII structure per 1 m2 of the built-up area [EURO/m2].

When analyzing stage II, it should be noted that the economic costs incurred to produce a "new" UKII structure in the next phase of its life accelerate the total depreciation of the facility (Equation (9)) and are pro-environmental.

The depreciation ratio (Wa) would be:

$$\mathbf{W\_{a}} = \mathbf{1} - \mathbf{K} \mathbf{J}^{\mathrm{I}} / (\mathbf{Q^{\mathrm{I}}} + \mathbf{Q^{\mathrm{II}}}) \tag{9}$$

The better the preparation of the UK<sup>I</sup> structure to work in phase II, the lower the QII adaptation costs and the faster the environmental depreciation, i.e., Wa decreasing, and vice versa. Thus, the multiplicity of multiple installations (Wkm) (Equation (10)) in order to recover environmental costs can be presented according to the formula:

$$\mathbf{W}\_{\rm km} = (\mathbf{Q}^{\rm I} + \mathbf{Q}^{\rm II}) / \mathbf{K} \mathbf{J}^{\rm I} \tag{10}$$

According to the formula (Equation (10)), the lower the value of the assembly multiplication index Wkm, the faster the path of ecological depreciation of the hall structure (this issue is the subject of further research). With each new phase of life (reuse), MASH halls reduce their ecological footprints and start generating ecological profits.

#### **4. Stage V—Conclusions, Summary, Recommendations**

The selection of the optimal ecological MASH solution was carried out taking into account the criteria listed in point 2.3. The criterion for reusing the structural elements of the facility is one of the most important. It characterizes objects with pro-ecological features. Adopting that the above-ground parts of the UK hall structure can be moved to another location and reassembled, their foundations remain on the ground and may constitute an obstacle to the redevelopment of the EU territory. Depending on the purpose of the land after the existing structure, the foundations, together with the development area, can be used, for example, as landscape elements or aggregates [67,68]. In most cases, however, the existing foundations with the remaining elements of the technical infrastructure are removed because it is difficult to guarantee their use in newly erected facilities.

Referring to the results of the total cumulative costs QI = 400–500 EUR/m2 from phase I of the construction work in relation to the costs of the secondary cycle QII = 270–330 EUR/m2, this ratio is in favor of reusing the structure and is 67% for all analyzed types of halls. The important conclusions result from comparative studies of the optimal proportions between the construction costs of UK hall structures and the ecological costs of the UE related to restoring the original (initial) state of the environment.

The UKII component of the next assembly of HSWM is a relatively constant parameter and ranges from 48–51% of the cost of a new investment, assuming the implementation of the investment on the Just in time basis [47,69], which was mentioned earlier.

Despite the pro-environmental action in the MASH implementation process, the WEIIo indicators increased from 2.21 to 2.77 times compared to cycle I and will extend the depreciation period of multiple assembly facilities. At the same time, the cases of such halls are recommended for a repeat design cycle in the CE circulation loop in order to reduce UK ecological and UE economic costs.

WEIIo indicators determine the impact of ecological costs on MASH's design solutions and constitute an approximate method but a reliable environmental assessment of the halls. The EET indicator assessment enables the elimination of incorrect technical solutions in the ecological and economic aspects already at the design stage. In the analyzed case, halls A and B, with a span of 21.0–36.0 m, have the most unfavorable WEIIo indicators, higher on average by 14.3–28% than the others.

As previously mentioned, Tingley and Allwood [13] and Cullen and Drewniok [12] showed that the reuse of building structure elements is uneconomical. However, the integrated approach presented in the EET analysis proved the profitability of the secondary use of steel hall structures by as much as 67% compared to new construction.

Using the EET method, the technological, economic and ecological aspects included in the dimensioned execution processes were combined. Simple indicators for assessing the return on environmental outlays were derived, i.e., the Wa depreciation indicator and the subsequent assembly Wkm index specifying the minimum reuse number of the hall structure to balance the environmental capital incurred for the original production of the facility. The presented approach, based on simple ecological indicators WEI and WEII, enables a quick analysis of the use of existing structures, which, in the era of limited raw material resources, are a good source of materials.

Reusing MASH elements is one aspect of the implementation of the construction sector sustainability paradigm [17]. It should be emphasized that the implementation of the reuse of MASH elements will require changes in the market from all participants in the investment process [19]. Starting from designers, through investors, traders, contractors, users and dismantling workers. This is important information for policymakers who should use a set of legal and financial instruments to lower the cost of reusing MASH structures.

The changes should also concern the creation of the MASH construction elements and the system of certification and trade in these elements [46], e.g., CER marking as an extension of the CE marking procedure has already been used for other products in the European Union.

However, due to widespread e-commerce, checking the availability of recycled MASH elements should not pose any major problems.

It is also important to change the perception of reusing MASH structural elements by the actors of the investment process. The common belief that only a "new" structural element will meet expectations regarding the safety of the structure should change.

The EET method can be dedicated to any steel structure, e.g., multi-span systems with any girders made of cylindrical profiles, openwork, plate girders or trusses; the same applies to columns.

The disadvantages of this method are the indirect assessment of ecological effects and the focus on material and economic gains in the life cycle of particular types of structures. However, the method is open to parallel parameterization of effects and ecological impacts, with an indication of environmental hazards resulting from the adoption of a specific design solution.

**Author Contributions:** Conceptualization, P.S.; Methodology, P.S., R.D. and J.A.; Software, P.S.; Validation, P.S., R.D. and J.A.; Resources, P.S.; Data Curation, P.S.; Writing—Original Draft Preparation, P.S., J.A. and R.D.; Writing—Review & Editing, P.S., J.A. and R.D.; Visualization, P.S.; Supervision, P.S.; Project Administration, P.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data available on request due to restrictions privacy.

**Conflicts of Interest:** The authors declare no conflict of interest.
